HK1163589B - Processes for making ethanol from acetic acid - Google Patents

Description

Process for the preparation of ethanol from acetic acid

Priority requirement

Priority of U.S. application No. 12/588,727 entitled "Tunable catalyst gases Phase Hydrogenation of Carboxylic Acids", filed on 26.10.2009, this application, is incorporated herein by reference in its entirety.

Technical Field

The present invention relates generally to processes for hydrogenating acetic acid to ethanol and novel catalysts for use in these processes that have high selectivity to ethanol.

Background

There is a long felt need for an economically viable process for converting acetic acid to ethanol that can be used by itself or subsequently converted to ethylene, which is an important commercial feedstock as it can be converted to vinyl acetate and/or ethyl acetate or any of a number of other chemical products. For example, ethylene can also be converted into a number of polymer and monomer products. Fluctuating natural gas and crude oil prices contribute to fluctuating costs of conventionally produced petroleum or natural gas derived ethylene, thereby making the need for alternative sources of ethylene greater than ever as oil prices rise.

Catalytic processes for the reduction of alkanoic acids and other carbonyl-containing compounds have been extensively studied and various combinations of catalysts, supports and operating conditions have been mentioned in the literature. Yokoyama et al, in "Fine chemicals through hydrolysis catalysis. Carboxylicacids and derivitives" reviewed the reduction of various carboxylic acids on metal oxides. Some of the attempts to develop hydrogenation catalysts for various carboxylic acids are outlined in chapter 8.3.1. (Yokoyama, T.; Setoyama, T. "Carboxylic acids and derivatives." in: "Fine chemicals through hydrolysis catalysis." 2001, 370-.

A series of studies by M.A. Vannice et al involved the conversion of acetic acid over various heterogeneous catalysts (Rachmady W.; Vannice, M.A.; J Catal. (2002) Vol.207, 317-. The use of H on loaded and unloaded iron was reported in different studies₂Reducing acetic acid in the gas phase. (Rachmady, W.; Vannice, M.A.J.Catal. (2002) Vol.208, pp.158-169). In Rachmady, w.; additional information about catalyst surface materials and organic intermediates is given in Vannice, m.a., j.catal. (2002) vol.208, page 170-. In Rachmady, w.; vanniece, m.a.j.cat. (2002) vol.209, pages 87-98) and Rachmady, w.; vapor phase acetic acid hydrogenation over a range of supported Pt-Fe catalysts was further investigated in Vannice, M.A.J.Catal. (2000) Vol.192, pp. 322-334).

Various relevant publications relating to the selective hydrogenation of unsaturated aldehydes can be found in: (Djerboua, F.; Benachour, D.; Touroude, R.applied Catalysis A: General 2005, 282, 123-.

Studies reporting the activity and selectivity of cobalt, platinum and tin containing catalysts in the selective hydrogenation of crotonaldehyde to unsaturated alcohols were found in: touroude et al (Djerboua, F.; Benachour, D.; Tourooude, R. applied Catalysis A: General 2005, 282, 123-133 and Liberkova, K.; Tourounde, R.; J. mol. Catal.2002, 180, 221-230) and K.Lazar et al (Lazar, K.; Rhodes, W.D.; Borbarth, I.; Hegedues, M.; Margitfalvi, 1.L. hyperfinenteractions 2002, 1391140, 87-96).

Microresidation measurements, infrared spectroscopy measurements, and reaction kinetics measurements in combination with quantum chemometrics are discussed by m.santiago et al (Santiago, m.a.n.; Sanchez-Castillo, m.a.; Cortright, r.d.; Dumesic, 1, A.J cat.2000, 193, 16-28.).

Catalytic activity for the hydrogenation of acetic acid has also been reported for heterogeneous systems with rhenium and ruthenium. (Ryashentseva, M.A.; Minachev, K.M.; Buiychev, B.M.; Ishchenko, V.M. Bull.Acad Sci.USSR1988, 2436-.

U.S. Pat. No.5,149,680 to Kitson et al describes a process for the catalytic hydrogenation of carboxylic acids and their anhydrides to alcohols and/or esters using platinum group metal alloy catalysts. U.S. Pat. No.4,777,303 to Kitson et al describes a process for the production of alcohols by the hydrogenation of carboxylic acids. U.S. Pat. No.4,804,791 to Kitson et al describes another process for the production of alcohols by the hydrogenation of carboxylic acids. See also USP 5,061,671; USP 4,990,655; USP 4,985,572; and USP 4,826,795.

Malinowski et al (Bull. Soc. Chim. Belg. (1985), 94(2), 93-5) discuss the heterogenisation of acetic acid on a support material such as silica (SiO. in the case of₂) Or titanium dioxide (TiO)₂) The reaction on the lower valence titanium of (a).

Bimetallic ruthenium-tin/silica catalysts are prepared by reacting tetrabutyltin with ruthenium dioxide supported on silica. (Loessard et al, students in Surface Science and catalysis (1989), Volume Date 1988, 48(struct. read. surf.), 591-.

For example, catalytic reduction of acetic acid has also been studied in Hindermann et al (Hindermann et al, J. chem. Res., Synopses (1980), (11), 373), disclosing catalytic reduction of acetic acid on iron and on base-promoted iron.

Existing approaches suffer from various problems that hinder commercial viability, including: (i) the catalyst does not have the necessary selectivity to ethanol; (ii) the catalyst may be too expensive and/or non-selective for the production of ethanol and produce unwanted by-products; (iii) excess operating temperature and pressure; and/or (iv) insufficient catalyst life.

Summary of The Invention

The present invention relates to a process for the hydrogenation of acetic acid to ethanol with high selectivity. In a first embodiment, the present invention is directed to a process for producing ethanol comprising hydrogenating acetic acid in the presence of a catalyst comprising a first metal, a siliceous support, and at least one support modifier. The first metal may be selected from: IB. A transition metal of group IIB, IIIB, IVB, VB, VIB, VIIB or VIII, a lanthanide metal, an actinide metal, or a metal of any of groups IIIA, IVA, VA or VIA. More preferably, the first metal may be selected from copper, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, titanium, zinc, chromium, rhenium, molybdenum, and tungsten. The first metal may be present in an amount of 0.1 to 25 wt.%, based on the total weight of the catalyst.

In another aspect, the catalyst may comprise a second metal (preferably different from the first metal) which may be selected from copper, molybdenum, tin, chromium, iron, cobalt, vanadium, tungsten, palladium, platinum, lanthanum, cerium, manganese, ruthenium, rhenium, gold, and nickel. In this aspect, for example, the first metal can be present in an amount of 0.1 to 10 weight percent and the second metal can be present in an amount of 0.1 to 10 weight percent, based on the total weight of the catalyst. In another aspect, the catalyst may comprise a third metal (preferably different from the first and second metals), which may be selected from cobalt, palladium, ruthenium, copper, zinc, platinum, tin and rhenium and/or which may be present in an amount of 0.05 and 4 wt% based on the total weight of the catalyst.

Preferably, the first metal is platinum and the second metal is tin, the molar ratio of platinum to tin being 0.4:0.6 to 0.6: 0.4. In another preferred combination, the first metal is palladium, the second metal is rhenium, and the molar ratio of rhenium to palladium is from 0.7:0.3 to 0.85: 0.15.

In a preferred aspect of the process, at least 10% of the acetic acid is converted during hydrogenation. Optionally, the catalyst has a selectivity to ethanol of at least 80% and/or a selectivity to methane, ethane, and carbon dioxide of less than 4%. In one embodiment, the catalyst has a yield that decreases by less than 6% per 100 hours of catalyst use.

The siliceous support may optionally be selected from the group consisting of silica, silica/alumina, calcium metasilicate (metasilicate), pyrogenic silica, high purity silica and mixtures thereof and may be present in an amount of from 25 wt% to 99 wt%, based on the total weight of the catalyst. Preferably, the silicon containing carrier has 50m²/g-600m²Surface area in g.

Support modifiers such as metasilicate support modifiers may be selected from: (i) an alkaline earth metal oxide, (ii) an alkali metal oxide, (iii) an alkaline earth metal metasilicate, (iv) an alkali metal metasilicate, (v) a group IIB metal oxide, (vi) a group IIB metal metasilicate, (vii) a group IIIB metal oxide, (viii) a group IIIB metal metasilicate, and mixtures thereof. As an alternative, the support modifier may be selected from the group consisting of oxides and metasilicates of sodium, potassium, magnesium, calcium, scandium, yttrium, and zinc, preferably CaSiO₃. The support modifier may be present in an amount of from 0.1 wt% to 50 wt%, based on the total weight of the catalyst.

In one embodiment, the hydrogenation is carried out in the vapor phase at a temperature from 125 ℃ to 350 ℃, a pressure from 10KPa to 3000KPa, and a hydrogen to acetic acid molar ratio of greater than 4: 1.

In another embodiment, the present invention relates to a crude ethanol product (optionally obtained from the hydrogenation of acetic acid, as discussed above) comprising (a) ethanol in an amount of from 15 to 70 wt.%, preferably from 20 to 50 wt.%, or more preferably from 25 to 50 wt.%; (b) acetic acid in an amount of from 0 to 80 wt%, preferably from 20 to 70 wt% or more preferably from 44 to 65 wt%; (c) water in an amount of 5 to 30 wt%, preferably 10 to 30 wt% or more preferably 10 to 26 wt%; and (d) any other compound in an amount less than 10 weight percent, wherein all weight percents are based on the total weight of the caide ethanol product. Preferred crude ethanol products comprise ethanol in an amount of 20 to 50 wt.%; acetic acid in an amount of 28-70 wt%; water in an amount of 10-30 wt%; and any other compound in an amount less than 6 wt%. Further preferred crude ethanol products comprise ethanol in an amount of 25 to 50 wt.%; acetic acid in an amount of 44-65 wt%; water in an amount of 10-26 wt%; and any other compound in an amount of less than 4 wt%.

In another embodiment, the invention relates to a process for producing ethanol comprising hydrogenating acetic acid in the presence of a catalyst comprising:

Pt_vPd_wRe_xSn_yCa_pSi_qO_r，

wherein: (i) v: y in a ratio of from 3: 2 to 2: 3, and/or (ii) w: x in a ratio of from 1: 3 to 1: 5; p and q are selected such that p: q is from 1: 20 to 1: 200, wherein r is selected to satisfy valence requirements, and v and w are selected such that:

in yet another embodiment, the invention relates to a process for producing ethanol comprising hydrogenating acetic acid in the presence of a catalyst comprising:

Pt_vPd_wRe_xSn_yAl_zCa_pSi_qO_r，

wherein: (i) v and y are 3: 2 to 2: 3; and/or (ii) w and x are from 1: 3 to 1: 5; controlling the relative positions of p and z and the aluminum and calcium atoms present so as to be present on the surface thereofThe acid sites are balanced by a carrier modifier; p and q are selected such that p: q is from 1: 20 to 1: 200, wherein r is selected to satisfy valence requirements, and v and w are selected such that:

brief description of the drawings

The present invention is described in detail below with reference to the attached drawing figures, wherein like numerals indicate like parts.

FIG. 1A shows the use of SiO₂-Pt_mSn_1-mA graph of selectivity to ethanol and ethyl acetate over catalyst;

FIG. 1B is a graph of the yield of ethanol and ethyl acetate for the catalyst of FIG. 1A;

FIG. 1C is a graph of acetic acid conversion for the catalyst of FIG. 1A;

FIG. 2A is a schematic representation of the use of SiO₂-Re_nPd_1-nA graph of selectivity to ethanol and ethyl acetate over catalyst;

FIG. 2B is a graph of the catalyst of FIG. 2A for the yields of ethanol and ethyl acetate;

FIG. 2C is a graph of acetic acid conversion for the catalyst of FIG. 2A;

FIG. 3A is a graph of catalyst yield versus ethanol at 15 hour testing;

FIG. 3B is a graph of the selectivity of the catalyst of FIG. 3A for ethanol;

FIG. 4A is a graph of catalyst yield to ethanol over a 100 hour test in accordance with another embodiment of the present invention;

FIG. 4B is a graph of the selectivity of the catalyst of FIG. 4A for ethanol;

FIG. 5A is a graph of catalyst yield versus ethanol in a 20 hour test according to another embodiment of the present invention;

FIG. 5B is a graph of the selectivity of the catalyst of FIG. 5A for ethanol;

FIG. 6A is a graph of the conversion of the catalyst of example 18;

FIG. 6B is a graph of the productivity of the catalyst of example 18;

FIG. 6C is a graph of the selectivity of the catalyst of example 18 at 250 ℃; and

FIG. 6D is a graph of the selectivity of the catalyst of example 18 at 275 deg.C.

Detailed Description

The present invention relates to a process for the production of ethanol by hydrogenating acetic acid in the presence of a catalyst. The catalyst used in the process comprises at least one metal, a siliceous support and at least one support modifier. The invention also relates to a catalyst for use in the process and to a process for preparing the catalyst. The hydrogenation reaction can be represented as follows:

it has been unexpectedly and unexpectedly found that the catalyst of the present invention provides high selectivity to ethoxylates, such as ethanol and ethyl acetate, particularly ethanol, when used in the hydrogenation of acetic acid. Embodiments of the present invention may be advantageously used in industrial applications to produce ethanol on an economically viable scale.

The catalyst of the invention comprises a first metal and optionally one or more of a second metal, a third metal or another metal on a support. In this context, the numerical terms "first", "second", "third", etc., when used to modify the word "metal", mean that the respective metals are different from each other. The total weight of all supported metals present in the catalyst is preferably from 0.1 to 25 wt%, for example from 0.1 to 15 wt% or from 0.1 wt% to 10 wt%. For purposes of this specification, weight percentages are based on the total weight of the catalyst including the metal and the support, unless otherwise specified. The metals in the catalyst may be present in the form of one or more metal oxides. To determine the weight percent of metal in the catalyst, the weight of any oxygen bound to the metal is ignored.

The first metal may be selected from: IB. A transition metal of group IIB, IIIB, IVB, VB, VIB, VIIB or VIII, a lanthanide metal, an actinide metal, or a metal of any of groups IIIA, IVA, VA or VIA. In a preferred embodiment, the first metal is selected from the group consisting of copper, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, titanium, zinc, chromium, rhenium, molybdenum, and tungsten. Preferably, the first metal is selected from the group consisting of platinum, palladium, cobalt, nickel and ruthenium. More preferably, the first metal is selected from platinum and palladium. When the first metal comprises platinum, it is preferred that the catalyst comprises platinum in an amount of less than 5 wt.%, for example less than 3 wt.% or less than 1 wt.%, due to the availability of platinum.

As indicated above, the catalyst optionally further comprises a second metal, which typically may act as a promoter. The second metal, if present, is preferably selected from the group consisting of copper, molybdenum, tin, chromium, iron, cobalt, vanadium, tungsten, palladium, platinum, lanthanum, cerium, manganese, ruthenium, rhenium, gold, and nickel. More preferably, the second metal is selected from the group consisting of copper, tin, cobalt, rhenium, and nickel. More preferably, the second metal is selected from tin and rhenium.

When the catalyst comprises two or more metals, one metal may act as a promoter metal while the other metal is the primary metal. For example, for a platinum/tin catalyst, platinum may be considered the primary metal and tin may be considered the promoter metal. For convenience, the present specification designates a first metal as the primary catalyst and a second metal (and optionally a metal) as the promoter. But this should not be taken as an indication of the following mechanism of catalytic activity.

If the catalyst comprises two or more metals, e.g., a first metal and a second metal, the first metal is optionally present in the catalyst in an amount of 0.1 to 10 wt.%, e.g., 0.1 to 5 wt.%, or 0.1 to 3 wt.%. The second metal is preferably present in an amount of 0.1 to 20 wt%, for example 0.1 to 10 wt% or 0.1 to 5 wt%. For catalysts comprising two or more metals, the two or more metals may be alloyed with each other or may comprise a non-alloyed metal solid solution or mixture.

The preferred metal ratio may vary slightly depending on the metals used in the catalyst. In some embodiments, the molar ratio of the first metal to the second metal is preferably from 10: 1 to 1: 10, such as from 4:1 to 1: 4, from 2: 1 to 1: 2, from 1.5: 1 to 1: 1.5, or from 1.1: 1 to 1: 1.1. It has now been unexpectedly and unexpectedly discovered that, as shown in fig. 1A, 1B, and 1C, a platinum to tin molar ratio of about 0.4:0.6 to 0.6:0.4 (or about 1: 1) is particularly preferred for platinum/tin catalysts to form ethanol from acetic acid with high selectivity, conversion, and yield. The selectivity to ethanol can be further improved by incorporating a modified support as described throughout this specification.

For other catalysts, molar ratios other than 1: 1 may be preferred. For example, for a rhenium/palladium catalyst, higher ethanol selectivity can be obtained at rhenium loadings higher than palladium loadings. As shown in FIGS. 2A, 2B, and 2C, ethanol is formed with preferred rhenium to palladium molar ratios of about 0.7:0.3 to 0.85:0.15 or about 0.75: 0.25 (3: 1) in terms of selectivity, conversion, and yield. Again, ethanol selectivity can be further improved by incorporating modified supports as described throughout this specification.

In embodiments when the catalyst comprises a third metal, the third metal may be selected from any of the metals listed above for the first or second metal, provided that the third metal is different from the first and second metals. In a preferred aspect, the third metal is selected from the group consisting of cobalt, palladium, ruthenium, copper, zinc, platinum, tin, and rhenium. More preferably, the third metal is selected from cobalt, palladium and ruthenium. When present, the total weight of the third metal is preferably from 0.05 to 4 wt%, for example from 0.1 to 3 wt% or from 0.1 to 2 wt%.

In one embodiment, the catalyst comprises a first metal and no additional metal (no second metal, etc.). In this embodiment, the first metal is preferably present in an amount of 0.1 to 10 wt.%. In another embodiment, the catalyst comprises a combination of two or more metals on a support. Specific preferred metal combinations for the various catalysts of this embodiment of the invention are provided in table 1 below. When the catalyst comprises a first metal and a second metal, the first metal is preferably present in an amount of 0.1 to 5 wt% and the second metal is preferably present in an amount of 0.1 to 5 wt%. When the catalyst comprises a first metal, a second metal and a third metal, the first metal is preferably present in an amount of 0.1 to 5 wt.%, the second metal is preferably present in an amount of 0.1 to 5 wt.% and the third metal is preferably present in an amount of 0.1 to 2 wt.%. In an exemplary embodiment, the first metal is platinum and is present in an amount of 0.1 to 5 wt.%, the second metal is present in an amount of 0.1 to 5 wt.%, and the third metal, if present, is preferably present in an amount of 0.05 to 2 wt.%.

Depending primarily on how the catalyst is made, the metal of the catalyst of the present invention may be dispersed throughout the support, coated on the outer surface of the support (egg shell) or modified (decoate) on the surface of the support.

In addition to the one or more metals, the catalyst of the present invention comprises a modified support, by which is meant a support comprising a support material and a support modifier which regulates the acidity of the support material. For example, acid sites on the support material such asThe acid sites may be adjusted by the support modifier to favor selectivity to ethanol during the hydrogenation of acetic acid. The acidity of the support material may be reduced by reducing the acidity of the support materialThe number of acid sites or reduction in the support materialThe availability of acid sites. The support material may also be adjusted by having the support modifier change the pKa of the support material. Unless the context indicates otherwise, the acidity or number of acid sites on a surface can be edited by f.delannay, "Characterization of heterogenous Catalysts"; chapter III: measurement of Acidity of Surfaces, page 370-404; the determination is performed by techniques described in Marcel Dekker, inc., n.y.1984, which is incorporated herein by reference in its entirety. It has now been found that metal-support interactions can have a strong influence on ethanol selectivity, in addition to the metal precursors used and the preparation conditions. In particular, the use of a modified support that adjusts the acidity of the support to render the support less acidic or more basic has surprisingly and unexpectedly demonstrated a greater favor in the formation of ethanol over other hydrogenation products.

Those skilled in the art will appreciate that the support material is selected such that the catalyst system has suitable activity, selectivity and robustness (robust) under the process conditions used to produce ethanol. Suitable support materials may include, for example, a stable metal oxide-based support or a ceramic-based support. Preferred supports include siliceous supports such as silica, silica/alumina, group IIA silicates such as calcium metasilicate, pyrogenic silica, high purity silica and mixtures thereof. Other supports may be used in some embodiments of the invention, including but not limited to iron oxides, alumina, titania, zirconia, magnesia, carbon, graphite, high surface area graphitized carbon, activated carbon, and mixtures thereof.

In a preferred embodiment, the support comprises a basic support modifier with low or no volatility. The low volatility modifier has a sufficiently low rate of loss during the catalyst life that the acidity of the support modifier is not reversed (reverse). Such alkaline modifiers may be selected, for example, from: (i) an alkaline earth metal oxide, (ii) an alkali metal oxide, (iii) an alkaline earth metal metasilicate, (iv) an alkali metal metasilicate, (v) a group IIB metal oxide, (vi) a group IIB metal metasilicate, (vii) a group IIIB metal oxide, (viii) a group IIIB metal metasilicate, and mixtures thereof. In addition to oxides and metasilicates, other types of modifiers including nitrates, nitrites, acetates, and lactates may be used in embodiments of the present invention. Preferably, the support modifier is selected from the group consisting of oxides and metasilicates of any of sodium, potassium, magnesium, calcium, scandium, yttrium, and zinc, and mixtures of any of the foregoing. Preferably, the support modifier is calcium silicate, more preferably calcium metasilicate (CaSiO)₃). If the support modifier comprises calcium metasilicate, it is preferred that at least a portion of the calcium metasilicate is in crystalline form.

The total weight of the modified support, including the support material and the support modifier, is preferably from 75 wt% to 99.9 wt%, for example from 78 wt% to 97 wt% or from 80 wt% to 95 wt%, based on the total weight of the catalyst. Preferably, a sufficient amount of support modifier is provided to adjust acidity, for example by reducing activityNumber of acid sites or reduced activityThe availability of acid sites, more preferably to ensure that the surface of the support is substantially inactiveAcid sites. In preferred embodiments, the support modifier is present in an amount of from 0.1 wt% to 50 wt%, for example from 0.2 wt% to 25 wt%, from 0.5 wt% to 15 wt%, or from 1 wt% to 8 wt%, based on the total weight of the catalyst. In preferred embodiments, the support material is present in an amount of 25 wt% to 99 wt%, for example 30 wt% to 97 wt% or 35 wt% to 95 wt%.

In one embodiment, the support material is a siliceous support material selected from the group consisting of silica, silica/alumina, group IIA silicates such as calcium metasilicate, pyrogenic silica, high purity silica and mixtures thereof. In the case where silica is used as the siliceous support, it is advantageous to ensure that the amount of aluminum (which is a common contaminant for silica) is low, preferably below 1 wt.%, for example below 0.5 wt.% or below 0.3 wt.%, based on the total weight of the modified support. Fumed silica is preferred in this regard because it is generally obtained in purities in excess of 99.7% by weight. As used throughout this application, high purity silica refers to silica in which acidic contaminants such as aluminum (if any) are present at levels less than 0.3 wt.%, such as less than 0.2 wt.% or less than 0.1 wt.%. When calcium metasilicate is used as the support modifier, the purity with respect to the silica used as the support material need not be very critical, although aluminum is still undesirable and will generally not be added intentionally. The aluminum content of such silica may be, for example, less than 10 wt.%, e.g., less than 5 wt.% or less than 3 wt.%. In cases where the support comprises from 2 wt% to 10 wt% of the support modifier, larger amounts of acidic impurities, such as aluminum, may be tolerated as long as they are substantially offset by a suitable amount of the support modifier.

Watch crystal silicon-containing carrier materials, e.g. silicaThe area is preferably at least about 50m²In terms of/g, e.g. at least about 100m²A/g of at least about 150m²A/g of at least about 200m²/g or most preferably at least about 250m²(ii) in terms of/g. In terms of range, the silicon-containing carrier material preferably has a thickness of 50 to 600m²G, e.g. 100-500m²(g or 100) -²Surface area in g. As used throughout this application, high surface area silica refers to silica having at least about 250m²Silica per g of surface area. For purposes of this specification, surface area refers to BET nitrogen surface area, which refers to the surface area determined by astm d6556-04 (incorporated herein by reference in its entirety).

The silicon-containing support material also preferably has an average pore diameter of 5-100nm, e.g., 5-30nm, 5-25nm, or about 5-10nm, as determined by mercury intrusion porosimetry, and 0.5-2.0cm, as determined by mercury intrusion porosimetry³In g, e.g. 0.7-1.5cm³In g or about 0.8 to 1.3cm³Average pore volume in g.

The morphology of the support material and the catalyst composition obtained therefrom may vary widely. In some exemplary embodiments, the morphology of the support material and/or catalyst composition may be pellets, extrudates, spheres, spray dried microspheres, rings, penta-spokes (pentarings), trilobes, quadrulobes, multilobes, or flakes, although cylindrical pellets are preferred. Preferably, the siliceous support material has an allowable bulk density of 0.1 to 1.0g/cm³For example, 0.2 to 0.9g/cm³Or 0.5-0.8g/cm³The form of (1). The silica support material preferably has an average particle diameter, in terms of size, of from 0.01 to 1.0cm, for example from 0.1 to 0.5cm or from 0.2 to 0.4cm, by which is meant, for example, the diameter of spherical particles or the equivalent spherical diameter of non-spherical particles. Because the size of the metal or metals on or in the modified support is typically very small, they should not substantially affect the size of the overall catalyst particle. Thus, the above particle sizes are generally applicable to the modified support as well as the size of the final catalyst particles.

Preferred silica support materials areSS61138 High Surface Area (HSA) silica catalyst support from Saint Gobain NorPro. Saint-Gobain NorPro SS61138 silica contains about 95 wt.% high surface area silica; about 250m²Surface area per gram; a median pore diameter of about 12 nm; about 1.0cm as measured by mercury intrusion porosimetry³Average pore volume per gram and about 0.352g/cm³(22lb/ft³) The bulk density of (2).

A preferred silica/alumina support material is KA-160(Sud Chemie) silica spheres having a nominal diameter of about 5mm, a density of about 0.562g/ml, about 0.583gH₂Absorption rate of O/g carrier of about 160-175m²Surface area per gram and pore volume of about 0.68 ml/g.

In embodiments in which substantially pure ethanol is produced with high selectivity, the support material is controlled by the introduction of a support modifier, as shown aboveAcidity can be quite advantageous. One possible by-product of the hydrogenation of acetic acid is ethyl acetate. According to the present invention, the support preferably includes a support modifier effective to inhibit the production of ethyl acetate, thereby rendering the catalyst composition highly selective to ethanol. Thus, the catalyst composition preferably has a low selectivity for converting acetic acid to ethyl acetate and highly undesirable by-products such as alkanes. The acidity of the support is preferably controlled so that less than 4%, preferably less than 2%, most preferably less than about 1% of the acetic acid is converted to methane, ethane and carbon dioxide. In addition, the acidity of the support can be controlled by using fumed silica or high purity silica as discussed above.

In one embodiment, the modified support comprises a support material and is effective to balance alumina generated, for example, from silicaCalcium metasilicate as a support modifier in the amount of acid sites. Preferably, the calcium metasilicate is present in an amount based on the total weight of the catalystIn an amount of 1-10% by weight, in order to ensure that the nature of the support is substantially neutral or basic.

As a support modifier, for example, calcium metasilicate, may tend to have a lower surface area than a support material, for example, a siliceous support material, and in one embodiment, the support material comprises a siliceous support material comprising at least about 80 wt.%, for example, at least about 85 wt.% or at least about 90 wt.% of high surface area silica, to offset such effects resulting from the inclusion of the support modifier.

In another aspect, the catalyst composition can be represented by the formula:

Pt_vPd_wRe_xSn_yCa_pSi_qO_r，

wherein: (i) the ratio of v to y is 3: 2-2: 3; and/or (ii) the w: x ratio is from 1: 3 to 1: 5. Thus, in this embodiment, the catalyst may comprise (i) platinum and tin; (ii) palladium and rhenium; or (iii) platinum, tin, palladium, and rhenium. Preferably, p and q are selected such that p: q is from 1: 20 to 1: 200, wherein r is selected to satisfy valence requirements, and v and w are selected such that:

in this respect, the process conditions and the values of v, w, x, y, p, q and r are preferably selected such that at least 70%, such as at least 80% or at least 90%, of the converted acetic acid is converted to a compound selected from ethanol and ethyl acetate, and at the same time less than 4% of the acetic acid is converted to alkanes. More preferably, the process conditions and the values of v, w, x, y, p, q and r are preferably carried outThe choice is made such that at least 70%, for example at least 80% or at least 90% of the acetic acid converted is converted to ethanol and at the same time less than 4% of the acetic acid is converted to alkanes. In many embodiments of the invention, p is selected to ensure that the support surface is substantially inactive, taking into account any minor impurities presentAcid sites.

In another aspect, a catalyst composition comprises:

Pt_vPd_wRe_xSn_yAl_zCa_pSi_qO_r，

wherein: (i) v and y are 3: 2 to 2: 3; and/or (ii) w and x are from 1: 3 to 1: 5. The relative positions of p and z and the aluminum atom and calcium atom present are preferably controlled so as to be present on the surface thereofThe acid sites are equilibrated by support modifiers such as calcium metasilicate; p and q are selected such that p: q is from 1: 20 to 1: 200, wherein r is selected to satisfy valence requirements, and v and w are selected such that:

preferably, in this aspect, the catalyst has at least about 100m²In terms of/g, e.g. at least about 150m²A/g of at least about 200m²/g or most preferably at least about 250m²Surface area per g, and z and p.gtoreq.z. In many embodiments of the invention, it is contemplated that any minor impurities present are presentP is selected to also ensure that the carrier surface is substantially free of activity that appears to promote conversion of ethanol to ethyl acetateAcid sites. Thus, as with the previous embodiments, the process conditions and values of v, w, x, y, p, q and r are preferably selected such that at least 70%, such as at least 80% or at least 90%, of the converted acetic acid is converted to ethanol, and at the same time less than 4% of the acetic acid is converted to alkanes.

Thus, while not being bound by theory, the oxide support material used in the catalyst of the present invention is modified and stabilized by the incorporation of non-volatile support modifiers that have the effect of either counteracting the acid sites present on the support surface or of thermally stabilizing the surface, enabling the desired improvement in ethanol selectivity, extended catalyst life, or both to be obtained. In general, support modifiers based on oxides in their most stable valence states will have low vapor pressure and thus low or even no volatility. Thus, it is preferred to provide a sufficient amount of modification of the support to: (i) counteracting acid sites present on the surface of the support material; (ii) imparting resistance to shape change at hydrogenation temperatures; or (iii) both. While not being bound by theory, imparting shape change resistance refers to imparting resistance to, for example, sintering, grain growth, grain boundary migration, defect and dislocation migration, plastic deformation, and/or other temperature-induced microstructural changes.

The catalyst of the present invention is a particulate catalyst in the sense that it is not impregnated into a brush coat on a monolith support like automotive catalysts and diesel soot trapping devices, and it is preferred that the catalyst of the present invention is formed into particles, sometimes also referred to as beads or pellets, having any of a variety of shapes, and that the catalytic metal is provided to the reaction zone by placing a plurality of these formed catalysts in a reactor. Common shapes include extrudates having any cross section, which are generalized cylinders in the sense that the generators defining the extrudate surface are parallel lines. As indicated above, any convenient particle shape may be used including pellets, extrudates, spheres, spray dried microspheres, rings, penta-spoked wheels, trilobes, quadralobes and polylobes, although cylindrical pellets are preferred. Typically, the shape is selected empirically based on the recognized ability to effectively contact the gas phase with the catalyst.

One advantage of the catalyst of the present invention is the stability or activity of the catalyst for the production of ethanol. Thus, it can be appreciated that the catalyst of the present invention is fully useful for commercial scale industrial applications for the hydrogenation of acetic acid, particularly for ethanol production. In particular, a degree of stability can be obtained such that the catalyst activity can have a rate of yield decline of less than 6% per 100 hours of catalyst use, for example less than 3% per 100 hours or less than 1.5% per 100 hours. Preferably, the rate of yield decrease is determined once the catalyst has attained steady state conditions.

In one embodiment, when the catalyst support comprises high purity silica and calcium metasilicate is used as the support modifier, the catalyst activity may be extended or stabilized at a temperature of 125 ℃ to 350 ℃ in the presence of acetic acid vapor for greater than 2500hr^-1The long term productivity and selectivity of the catalyst for a commercially viable operation at space velocities of (a) is extended to over 1 week, over 2 weeks and even months.

The catalyst composition of the present invention is preferably formed by metal impregnation of the modified support, although other methods such as chemical vapor deposition may also be used. Prior to impregnation of the metal, it is often desirable to form the modified support, for example by a step of impregnating the support material with a support modifier. Precursors of the support modifier, such as acetate or nitrate, may be used. In one aspect, a support modifier such as CaSiO₃Added to a carrier material such as SiO₂In (1). For example, an aqueous suspension of the support modifier may be formed by adding the solid support modifier to deionized water followed by addition of the colloidal support material thereto. The resulting mixture may be stirred and added to additional support material using, for example, incipient wetness impregnation techniques, whereIncipient wetness impregnation techniques involve the addition of a support modifier to a support material having the same pore volume as the volume of the support modifier solution. Capillary action then draws the support modifier into the pores within the support material. The modified support may then be formed by drying and calcining to remove water and any volatile components from the support modifier solution and to deposit the support modifier on the support material. Drying may be carried out, for example, at a temperature of 50 ℃ to 300 ℃, e.g., 100 ℃ to 200 ℃, or about 120 ℃, optionally for a period of 1 to 24 hours, e.g., 3 to 15 hours, or 6 to 12 hours. Once formed, the modified support may be shaped into particles having a desired size distribution, for example, to form particles having an average particle size of 0.2 to 0.4 cm. The carrier may be extruded, granulated, tableted, pressed, crushed or sieved to the desired size distribution. Any known method of shaping the carrier material into the desired size distribution may be used. Calcination of the shaped modified support may be carried out, for example, at a temperature of from 250 ℃ to 800 ℃, such as 300 ℃ to 700 ℃ or about 500 ℃, optionally for a period of from 1 to 12 hours, such as from 2 to 10 hours, from 4 to 8 hours or about 6 hours.

In a preferred method of preparing the catalyst, the metal is impregnated onto the modified support. A precursor of the first metal (first metal precursor) is preferably used in the metal impregnation step, said precursor for example comprising a water-soluble compound or a water-dispersible compound/complex in respect of the first metal. Depending on the metal precursor used, a solvent such as water, glacial acetic acid or an organic solvent may preferably be used. The second metal is also preferably impregnated into the modified support from a second metal precursor. A third metal or third metal precursor may also be impregnated into the modified support if desired.

Impregnation is carried out by adding (optionally dropwise) either or both of the first metal precursor and/or the second metal precursor and/or the further metal precursor (preferably in suspension or solution) to the dry modified support. The resulting mixture may then be heated, for example optionally under vacuum, to remove the solvent. Additional drying and calcination may then optionally be performed with ramping heating to form the final catalyst composition. Upon heating and/or application of vacuum, the metals of the metal precursors preferably decompose to their elemental (or oxide) form. In some cases, removal of the liquid carrier, e.g., water, may not be complete before the catalyst is put into use and calcined, e.g., subjected to the high temperatures encountered during operation. These compounds are converted to the catalytically active form of the metal or catalytically active oxide thereof during the calcination step, or at least during the initial stage of use of the catalyst.

The impregnation of the first and second metals (and optionally further metals) into the modified support may be carried out simultaneously (co-impregnation) or sequentially. In simultaneous impregnation, the first and second metal precursors (and optionally additional metal precursors) are mixed together and added together to the modified support, followed by drying and calcination to form the final catalyst composition. For simultaneous impregnation, if the two precursors are not compatible with the desired solvent, e.g., water, it may be desirable to use a dispersant, surfactant, or solubilizer, e.g., ammonium oxalate, to facilitate dispersion or dissolution of the first and second metal precursors.

In sequential impregnation, the first metal precursor is first added to the modified support, followed by drying and calcination, and then the resulting material is impregnated with the second metal precursor, followed by additional drying and calcination steps to form the final catalyst composition. Additional metal precursors (e.g., a third metal precursor) may be added with the first and/or second metal precursor or may be a separate third impregnation step followed by drying and calcination. Of course, combinations of sequential and simultaneous impregnation may be used if desired.

Suitable metal precursors include, for example, metal halides, amine-solubilized metal hydroxides, metal nitrates, or metal oxalates. For example, suitable compounds for the platinum and palladium precursors include chloroplatinic acid, ammonium chloroplatinate, amine-solubilized platinum hydroxide, platinum nitrate, platinum tetraamine nitrate, platinum chloride, platinum oxalate, palladium nitrate, palladium tetraamine nitrate, palladium chloride, palladium oxalate, sodium palladium chloride, and sodium platinum chloride. Generally, from the viewpoint of both economic and environmental aspects, an aqueous solution of a soluble compound of platinum is preferable. In one embodiment, the first stepA metal precursor is not a metal halide and is substantially free of metal halide. While not being bound by theory, it is believed that such non- (metal halide) precursors enhance ethanol selectivity. A particularly preferred precursor for platinum is platinum ammine nitrate, i.e., Pt (NH)₃)₄(NO₄)₂。

In one aspect, the "promoter" metal or metal precursor is first added to the modified support, followed by the "primary" or "primary" metal or metal precursor. Of course, the reverse order of addition is also possible. Exemplary precursors of the promoter metal include metal halides, amine-solubilized metal hydroxides, metal nitrates, or metal oxalates. As indicated above, in a sequential embodiment, it is preferred to follow each impregnation step with drying and calcination. In the case of promoted bimetallic catalysts as described above, sequential impregnation may be used, with the promoter metal added initially, followed by a second impregnation step comprising co-impregnation of the two primary metals, e.g., Pt and Sn.

By way of example, SiO₂PtSn/CaSiO on₃Can be prepared by first adding CaSiO₃Impregnation into SiO₂Followed by Pt (NH)₃)₄(NO₄)₂And Sn (AcO)₂Co-impregnation for preparation. Furthermore, each impregnation step may be followed by a drying and calcination step. In most cases, the impregnation can be carried out using a metal nitrate solution. However, various other soluble salts that release metal ions upon calcination may also be used. Examples of other suitable metal salts for impregnation include metal acids such as perrhenic acid solutions, metal oxalates, and the like. In those cases where substantially pure ethanol is to be produced, it is generally preferred to avoid the use of halogenated precursors for the platinum group metals, but to use precursors based on nitrogen-containing amines and/or nitrates.

As will be readily appreciated by those skilled in the art, the process of hydrogenating acetic acid to ethanol according to one embodiment of the present invention may be carried out in various configurations using fixed bed reactors or fluidized bed reactors. In many embodiments of the invention, an "adiabatic" reactor may be used; that is, there is little or no need for internal piping (plumbig) through the reaction zone to add or remove heat. Alternatively, a shell-and-tube reactor provided with a heat transfer medium can be used. In many cases, the reaction zone may be housed in a single vessel or in a series of vessels with heat exchangers in between. It is expressly contemplated that the acetic acid reduction process using the catalyst of the present invention may be conducted in an adiabatic reactor, since such reactor configurations are generally much less capital intensive than shell and tube configurations.

Typically, the catalyst is used in a fixed bed reactor, for example in the shape of an elongated tube or conduit, through which the reactants, typically in vapor form, pass or pass. Other reactors, such as fluidized bed or ebullated bed reactors, may be used if desired. In some cases, the hydrogenation catalyst may be used in combination with an inert material to regulate the pressure drop of the reactant stream through the catalyst bed and the contact time of the reactant compound with the catalyst particles.

The hydrogenation reaction may be carried out in the liquid or gas phase. Preferably, the reaction is carried out in the gas phase under the following conditions. The reaction temperature may be from 125 ℃ to 350 ℃, e.g., from 200 ℃ to 325 ℃, from 225 ℃ to about 300 ℃, or from 250 ℃ to about 300 ℃. The pressure may be in the range of from 10KPa to 3000KPa (about 0.1 to 30 atmospheres), for example from 50KPa to 2300KPa or from 100KPa to 1500 KPa. The reactants may be added for more than 500hr^-1E.g. greater than 1000hr^-1Greater than 2500hr^-1And even greater than 5000hr^-1Is fed to the reactor at a Gas Hourly Space Velocity (GHSV). In terms of range, GHSV may be 50hr^-1-50,000hr^-1E.g. 500hr^-1-30,000hr^-1、1000hr^-1-10,000hr^-1Or 1000hr^-1-6500hr^-1。

In another aspect of the process of the invention, the hydrogenation is carried out at a selected GHSV at a pressure just sufficient to overcome the pressure drop across the catalytic bed, although the use of higher pressures is not limited, it being understood that at high space velocities, e.g., 5000hr, the hydrogenation is carried out at^-1Or 6,500hr^-1May experience a significant pressure drop through the reactor bed.

Although the reaction consumes 2 moles of hydrogen per mole of acetic acid to produce 1 mole of ethanol, the actual molar ratio of hydrogen to acetic acid in the feed stream may be about 100: 1 to 1: 100, such as 50: 1 to 1: 50, 20: 1 to 1: 2, or 12: 1 to 1: 1. Most preferably, the molar ratio of hydrogen to acetic acid is greater than 4:1, such as greater than 5: 1 or greater than 10: 1.

The contact or residence time may also vary widely, depending on the amount of acetic acid, catalyst, reactor, temperature and pressure. Typical contact times range from fractions of a second to more than several hours when using a catalyst system other than a fixed bed, with preferred contact times, at least for gas phase reactions, of from 0.1 to 100 seconds, for example from 0.3 to 80 seconds or from 0.4 to 30 seconds.

The acetic acid may be vaporized at the reaction temperature, and the vaporized acetic acid may then be fed along with hydrogen in an undiluted state or diluted with a relatively inert carrier gas such as nitrogen, argon, helium, carbon dioxide, and the like. For the reaction to run in the gas phase, the temperature in the system should be controlled so that it does not fall below the dew point of acetic acid.

In particular, using the catalyst and process of the present invention, favorable conversion of acetic acid and favorable selectivity and yield to ethanol can be obtained. For the purposes of the present invention, the term "conversion" refers to the amount of acetic acid in the feed that is converted to compounds other than acetic acid. Conversion is expressed as a mole percent based on acetic acid in the feed.

The conversion of acetic acid (AcOH) was calculated from the Gas Chromatography (GC) data using the following equation:

for the purposes of the present invention, the conversion may be at least 10%, for example at least 20%, at least 40%, at least 50%, at least 60%, at least 70% or at least 80%. While catalysts with high conversion, e.g., at least 80% or at least 90%, are desirable, low conversions may also be acceptable when the selectivity of ethanol is high. It is, of course, well understood that in many cases conversion can be compensated for by appropriate recycle streams or by using larger reactors, but it is more difficult to compensate for poor selectivity.

Selectivity is expressed as mole percent based on converted acetic acid. It is understood that each compound converted from acetic acid has an independent selectivity and that the selectivity is independent of conversion. For example, if 50 mole% of the converted acetic acid is converted to ethanol, the ethanol selectivity is 50%. The selectivity to ethanol (EtOH) was calculated from Gas Chromatography (GC) data using the following equation:

wherein "total mmol C (GC)" means the total moles of carbon of all products analyzed by gas chromatography.

For the purposes of the present invention, the catalyst has a selectivity to ethoxylates of at least 60%, for example at least 70% or at least 80%. As used herein, the term "ethoxylate" refers specifically to the compounds ethanol, acetaldehyde and ethyl acetate. Preferably, the selectivity to ethanol is at least 80%, such as at least 85% or at least 88%. It is also desirable in embodiments of the present invention to have low selectivity to undesirable products such as methane, ethane, and carbon dioxide. The selectivity to these undesirable products is less than 4%, for example less than 2% or less than 1%. Preferably, no detectable amounts of these undesirable products are formed during hydrogenation. In several embodiments of the invention, the formation of alkanes is low, typically less than 2%, often less than 1%, and in many cases less than 0.5% of the acetic acid passing through the catalyst is converted to alkanes, which have little value other than as a fuel.

The yield refers to the grams of a given product, e.g., ethanol, formed per hour during hydrogenation based on kilograms of catalyst used. In one embodiment of the invention, the yield of at least 200g of ethanol, for example at least 400 g of ethanol or at least 600g of ethanol per kg of catalyst per hour is preferred. In terms of ranges, the yield is preferably 200-.

Some catalysts of the invention can achieve acetic acid conversion of at least 10%, ethanol selectivity of at least 80%, and a yield of at least 200g of ethanol per kg of catalyst per hour. Catalysts within the scope of the present invention can achieve acetic acid conversion of at least 50%, ethanol selectivity of at least 80%, selectivity to undesired compounds of less than 4%, and a yield of at least 600g of ethanol per kg of catalyst per hour.

In another embodiment, the invention relates to a crude ethanol product formed by the process of the invention. The crude ethanol product produced by the hydrogenation process of the present invention will typically comprise primarily unreacted acetic acid and ethanol prior to any subsequent processing, such as purification and isolation. In some exemplary embodiments, the crude ethanol product comprises ethanol in an amount of 15 wt.% to 70 wt.%, such as 20 wt.% to 50 wt.% or 25 wt.% to 50 wt.%, based on the total weight of the crude ethanol product. Preferably, the crude ethanol product contains at least 22 wt.% ethanol, at least 28 wt.% ethanol, or at least 44 wt.% ethanol. Depending on the conversion, the caide ethanol product will typically also comprise unreacted acetic acid, for example in an amount of from 0 to 80 wt.%, for example from 5 to 80 wt.%, from 20 to 70 wt.%, from 28 to 70 wt.%, or from 44 to 65 wt.%. Because water is formed during the reaction, water will also be present in the crude ethanol product, for example, in an amount of 5 to 30 wt.%, such as 10 to 30 wt.% or 10 to 26 wt.%. Other components such as esters, ethers, aldehydes, ketones, alkanes, and carbon dioxide, if detectable, may be present in total in an amount of less than 10 wt%, such as less than 6 wt% or less than 4 wt%. In terms of ranges, the other components may be present in an amount of 0.1 to 10 weight percent, such as 0.1 to 6 weight percent or 0.1 to 4 weight percent. Thus, a range of exemplary crude ethanol compositions in various embodiments of the invention are provided in table 2 below.

In a preferred embodiment, the catalyst is prepared, for example, from CaSiO₃A crude ethanol product is formed over the platinum/tin catalyst on the modified silica support. Depending on the particular catalyst and process conditions used, the crude ethanol product may have any of the compositions shown in table 3 below.

The feedstock used in connection with the process of the present invention may be derived from any suitable source, including natural gas, petroleum, coal, biomass, and the like. It is well known to produce acetic acid by methanol carbonylation, acetaldehyde oxidation, ethylene oxidation, oxidative fermentation and anaerobic fermentation. As petroleum and natural gas prices fluctuate, becoming more or less expensive, processes for the production of acetic acid and intermediates, such as methanol and carbon monoxide, from alternative carbon sources have become increasingly attractive. In particular, when petroleum is relatively expensive compared to natural gas, it may become advantageous to produce acetic acid from synthesis gas ("syngas") derived from any available carbon source. For example, U.S. patent No.6,232,352 to Vidalin (the disclosure of which is incorporated herein by reference) teaches a method of retrofitting a methanol plant to make acetic acid. By retrofitting a methanol plant, the substantial capital costs associated with CO production are significantly reduced or largely eliminated for a new acetic acid plant. All or a portion of the syngas is diverted from the methanol synthesis loop and fed to a separator unit to recover CO and hydrogen, which are then used to produce acetic acid. In addition to acetic acid, this process can also be used to produce hydrogen for use in connection with the present invention.

U.S. patent No. re 35,377 to Steinberg et al, which is also incorporated herein by reference, provides a process for the production of methanol by the conversion of carbonaceous materials such as oil, coal, natural gas and biomass materials. The method comprises hydro-gasification of solid and/or liquid carbonaceous material to obtain a process gas, which process gas is steam pyrolyzed with additional natural gas to form synthesis gas. The synthesis gas is converted to methanol which can be carbonylated to acetic acid. This process also produces hydrogen gas as described above in connection with the present invention. See also U.S. Pat. No.5,821,111 to Grady et al and U.S. Pat. No.6,685,754 to Kindig et al, the disclosures of which are incorporated herein by reference, which disclose a process for converting waste biomass to syngas via gasification.

Alternatively, acetic acid may be withdrawn as a crude product in vapor form directly from the flasher of a methanol carbonylation unit of the type described in U.S. Pat. No.6,657,078 to Scates et al, which is incorporated herein by reference in its entirety. For example, the crude vapor product can be fed directly to the ethanol synthesis reaction zone of the present invention without the need to condense acetic acid and light ends or remove water, thereby saving overall process costs.

The ethanol obtained using the hydrogenation process of the present invention can be used as a fuel by itself or subsequently converted to ethylene, which is an important commercial feedstock as it can be converted to polyethylene, vinyl acetate and/or ethyl acetate or any of a number of other chemical products. For example, ethylene can also be converted into a number of polymer and monomer products. The dehydration of ethanol to ethylene is shown below.

Ethanol may be dehydrated using any known dehydration catalyst, such as those described in co-pending applications U.S. application No.12/221,137 and U.S. application No.12/221,138, the entire contents and disclosures of which are incorporated herein by reference. For example, zeolite catalysts may be used as dehydration catalysts. Although all zeolites having a pore size of at least about 0.6nm may be used, preferred zeolites include dehydration catalysts selected from the group consisting of mordenite, ZSM-5, zeolite X and zeolite Y. For example, zeolite X is described in U.S. Pat. No.2,882,244 and zeolite Y is described in U.S. Pat. No.3,130,007, which are incorporated herein by reference in their entirety.

Ethanol may also be used as a fuel for pharmaceutical products, detergents, sanitizers, hydroconversion, or consumption. Ethanol can also be used as a source material for the production of ethyl acetate, aldehydes, and higher alcohols, particularly butanol. In addition, any esters formed during the process for producing ethanol according to the present invention, such as ethyl acetate, may be further reacted with an acid catalyst to form additional ethanol as well as acetic acid, which may be recycled to the hydrogenation process.

The invention is described in detail below with reference to a number of embodiments for the purpose of illustration and description only. Modifications to the specific embodiments within the spirit and scope of the invention and set forth in the appended claims will be readily apparent to those skilled in the art.

The following examples describe the procedures used to prepare the various catalysts used in the process of the present invention.

Examples

Catalyst preparation (in general)

The catalyst support was dried overnight at 120 ℃ under circulating air before use. Unless otherwise mentioned, all commercial supports (i.e. SiO)₂、ZrO₂) Used at 14/30 mesh or in its original shape (1/16 inch or 1/8 inch pellets). The powdered material (i.e., CaSiO) is added after the metal is added₃) Granulation, crushing and sieving. The preparation of each catalyst is described in more detail below.

Example 1 SiO₂-CaSiO₃(5)-Pt(3)-Sn(1.8) catalyst

The catalyst is prepared by firstly mixing CaSiO₃(Aldrich) was added to SiO₂The catalyst support was prepared by adding Pt/Sn. First, CaSiO₃(. ltoreq.200 mesh) aqueous suspension by adding 0.52g of this solid to 13ml of deionized water, followed by 1.0ml of colloidal SiO₂(15 wt% solution, NALCO). The suspension was stirred at room temperature for 2 hours and then 10.0g SiO was added using incipient wetness impregnation technique₂Catalyst support (14/30 mesh). After standing for 2 hours, the material was evaporated to dryness, then dried under circulating air at 120 ℃ overnight and calcined at 500 ℃ for 6 hours. Then all SiO is put in₂-CaSiO₃The material was used for Pt/Sn metal impregnation.

The catalyst is prepared by firstly mixing Sn (OAc)₂(tin acetate, Sn (OAc) from Aldrich)₂) (0.4104g, 1.73mmol) was added to a vial (visual) containing 6.75ml of 1: 1 diluted glacial acetic acid (Fisher). The mixture was stirred at room temperature for 15 minutes, then 0.6711g (1.73mmol) of solid Pt (NH) were added₃)₄(NO₃)₂(Aldrich). The mixture was stirred at room temperature for an additional 15 minutes and then added dropwise to 5.0g of SiO in a 100ml round bottom flask₂-CaSiO₃In a carrier. The metal solution was continuously stirred until all the Pt/Sn mixture was added to the SiO₂-CaSiO₃In the support and while rotating the flask each time the metal solution is added. After the addition of the metal solution was completed, the flask containing the impregnated catalyst was maintained at room temperature for 2 hours. The flask was then connected to a rotary evaporator (bath temperature 80 ℃) and evacuated until dry while slowly rotating the flask. The material was then further dried overnight at 120 ℃ and then calcined using the following temperature sequence: 25 → 160 ℃/slope 5.0 deg/min; keeping for 2.0 hours; 160 → 500 deg.C/slope of 2.0 deg/min; the holding time was 4 hours. Yield (yield): 11.21g of dark grey material.

Example 2-KA160-CaSiO₃(8)-Pt(3)-Sn(1.8)

The material is prepared by firstly mixing CaSiO₃Adding into KA160 catalyst carrier (SiO)₂-(0.05)A1₂O₃Sud Chemie, 14/30 mesh), followed by addition of Pt/Sn. First, CaSiO₃(. ltoreq.200 mesh) aqueous suspension by adding 0.42g of this solid to 3.85ml of deionized water, followed by 0.8ml of colloidal SiO₂(15 wt% solution, NALCO). The suspension was stirred at room temperature for 2 hours and then 5.0g of KA160 catalyst support (14/30 mesh) was added using incipient wetness impregnation technique. After standing for 2 hours, the material was evaporated to dryness, then dried under circulating air at 120 ℃ overnight and calcined at 500 ℃ for 6 hours. Then all KA160-CaSiO₃The material was used for Pt/Sn metal impregnation.

The catalyst is prepared by firstly mixing Sn (OAc)₂(tin acetate, Sn (OAc) from Aldrich)₂) (0.2040g, 0.86mmol) was added to a vial containing 6.75ml of 1: 1 diluted glacial acetic acid (Fisher). The mixture was stirred at room temperature for 15 minutes, then 0.3350g (0.86mmol) of solid Pt (NH) were added₃)₄(NO₃)₂(Aldrich). The mixture was stirred at room temperature for a further 15 minutes and then added dropwise to 5.0g of SiO in a 100ml round-bottomed flask₂-CaSiO₃In a carrier. After the addition of the metal solution was completed, the flask containing the impregnated catalyst was maintained at room temperature for 2 hours. The flask was then connected to a rotary evaporator (bath temperature 80 ℃) and evacuated until dry while slowly rotating the flask. The material was then further dried overnight at 120 ℃ and then calcined using the following temperature sequence: 25 → 160 ℃/slope 5.0 deg/min; keeping for 2.0 hours; 160 → 500 deg.C/slope of 2.0 deg/min; the holding time was 4 hours. Yield: 5.19g of a tan material.

Example 3 SiO₂-CaSiO₃(2.5)-Pt(1.5)-Sn(0.9)

The catalyst was prepared in the same manner as in example 1 using the following starting materials: 0.26g CaSiO₃As a support modifier; 0.5ml of colloidal SiO₂(15% by weight solution)NALCO), 0.3355g (0.86mmol) of Pt (NH)₃)₄(NO₃)₂(ii) a And 0.2052g (0.86mmol) of Sn (OAc)₂. Yield: 10.90g of dark grey material.

Example 4 SiO₂+MgSiO₃-Pt(1.0)-Sn(1.0)

The catalyst was prepared in the same manner as in example 1 using the following starting materials: 0.69g Mg (AcO) as a support modifier; 1.3g of colloidal SiO₂(15% by weight solution, NALCO), 0.2680g (0.86mmol) of Pt (NH)₃)₄(NO₃)₂(ii) a And 0.1640g (0.86mmol) of Sn (OAc)₂. Yield: 8.35 g. With Mg (AcO) solution and colloidal SiO₂Impregnated SiO₂And (3) a carrier. The support was dried and then calcined to 700 ℃.

Example 5 SiO₂-CaSiO₃(5)-Re(4.5)-Pd(1)

Preparation of SiO as described in example 1₂-CaSiO₃(5) A modified catalyst support. Then by using a catalyst containing NH₄ReO₄And Pd (NO)₃)₂By impregnating SiO with an aqueous solution of₂-CaSiO₃(5) (1/16 inch extrudates) Re/Pd catalyst was prepared. The metal solution is prepared by first reacting NH₄ReO₄(0.7237g, 2.70mmol) was added to a vial containing 12.0ml of deionized water for preparation. The mixture was stirred at room temperature for 15 minutes, then 0.1756g (0.76mmol) of solid Pd (NO) were added₃)₂. The mixture was stirred at room temperature for a further 15 minutes and then added dropwise to 10.0g of dry SiO in a 100ml round-bottomed flask₂-(0.05)CaSiO₃In the catalyst support. After the addition of the metal solution was completed, the flask containing the impregnated catalyst was maintained at room temperature for 2 hours. All other treatments (drying, calcination) were carried out as described in example 1. Yield: 10.9g of brown material.

Example 6 SiO₂-ZnO(5)-Pt(1)-Sn(1)

Powdered and sieved high surface area silica NPSG SS61138(100g) with a uniform particle size distribution of about 0.2mm was dried overnight at 120 ℃ in a circulating air oven atmosphere and then cooled to room temperature. To this was added a zinc nitrate hexahydrate solution. The resulting slurry was dried in an oven with gradual heating to 110 ℃ (> 2 hours, 10 ℃/min) and then calcined. To this was added a solution of platinum nitrate (Chempur) in distilled water and a solution of tin oxalate (alfaaaesar) (1.74g) in dilute nitric acid (1N, 8.5 ml). The resulting slurry was dried in an oven with gradual heating to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

In addition, the following comparative catalysts were also prepared.

Example 7 comparison

TiO₂-CaSiO₃(5) -Pt (3) -Sn (1.8). The material is prepared by firstly mixing CaSiO₃Is added to TiO₂The catalyst (anatase, 14/30 mesh) support was then prepared by adding Pt/Sn as described in example 1. First, CaSiO₃(. ltoreq.200 mesh) aqueous suspension by adding 0.52g of this solid to 7.0ml of deionized water, followed by 1.0ml of colloidal SiO₂(15 wt% solution, NALCO). The suspension was stirred at room temperature for 2 hours and then 10.0g TiO was added using incipient wetness impregnation technique₂Catalyst support (14/30 mesh). After standing for 2 hours, the material was evaporated to dryness, then dried under circulating air at 120 ℃ overnight and calcined at 500 ℃ for 6 hours. 0.6711g (1.73mmol) of Pt (NH) were then used₃)₄(NO₃)₂And 0.4104g (1.73mmol) of Sn (OAc)₂All TiO are treated according to the procedure described in example 1₂-CaSiO₃The material was used for Pt/Sn metal impregnation. Yield: 11.5g of light grey material.

Example 8 comparison

Sn (0.5) on high purity low surface area silica. Powdered and sieved high purity low surface area silica (100g) of uniform particle size distribution of about 0.2mm was dried overnight at 120 ℃ in an oven under nitrogen atmosphere and then cooled to room temperature. To this was added a solution of tin oxalate (Alfa Aesar) (1.74g) in dilute nitric acid (1N, 8.5 ml). The resulting slurry was dried in an oven with gradual heating to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example 9 comparison

Pt (2) -Sn (2) on high surface area silica. Powdered and sieved high surface area silica NPSG SS61138(100g) with a uniform particle size distribution of about 0.2mm was dried overnight at 120 ℃ in a circulating air oven atmosphere and then cooled to room temperature. To this was added a solution of nitrate hexahydrate (Chempur). The resulting slurry was dried in an oven with gradual heating to 110 ℃ (> 2 hours, 10 ℃/min) and then calcined. To this was added a solution of platinum nitrate (Chempur) in distilled water and a solution of tin oxalate (Alfa Aesar) in dilute nitric acid. The resulting slurry was dried in an oven with gradual heating to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example 10 comparative

KA160-Pt (3) -Sn (1.8). This material was passed through KA160 catalyst Support (SiO) as described in example 16₂-(0.05)A1₂O₃Sud Chemie, 14/30 mesh) by incipient wetness impregnation. Metal solution is prepared by first reacting Sn (OAc)₂(0.2040g, 0.86mmol) was added to a vial containing 4.75ml of 1: 1 diluted glacial acetic acid. The mixture was stirred at room temperature for 15 minutes, then 0.3350g (0.86mmol) of solid Pt (NH) were added₃)₄(NO₃)₂. The mixture was stirred at room temperature for an additional 15 minutes and then added dropwise to 5.0g of dry KA160 catalyst support (14/30 mesh) in a 100mL round bottom flask. All other treatments, drying and calcination were carried out as described in example 16. Yield: 5.23g of tan material.

Example 11 comparison

SiO₂-SnO₂(5) -Pt (1) -Zn (1). Powdered and sieved high surface area silica NPSGSS61138(100g) with a uniform particle size distribution of about 0.2mm was dried overnight at 120 ℃ in a circulating air oven atmosphere and then cooled to room temperature. To which tin acetate (Sn (OAc) was added₂And (3) solution. The resulting slurry was dried in an oven with gradual heating to 110 ℃ (> 2 hours, 10 ℃/min) and then calcined. To this was added a solution of platinum nitrate (Chempur) in distilled water and a solution of tin oxalate (Alfa Aesar) in dilute nitric acid. The resulting slurry was dried in an oven with gradual heating to 110 ℃ (> 2 hours, 10 ℃/min). The impregnated catalyst mixture was then calcined at 500 deg.C (6 hours, 1 deg.C/min).

Example 12 comparison

SiO₂-TiO₂(10) -Pt (3) -Sn (1.8). Preparation of TiO as follows₂-a modified silica support. 4.15g (14.6mmol) of Ti { OCH (CH)₃)₂}₄The solution in 2-propanol (14ml) was added dropwise to 10.0g SiO in a 100ml round bottom flask₂Catalyst support (1/16 inch extrudates). The flask was allowed to stand at room temperature for 2 hours, and then evacuated using a rotary evaporator (bath temperature 80 ℃) until dry. Next, 20ml of deionized water was slowly added to the flask and the material was allowed to stand for 15 minutes. The resulting water/2-propanol was then removed by filtration and H was added repeatedly₂And O2 times. The final material was dried overnight at 120 ℃ under circulating air, followed by calcination at 500 ℃ for 6 hours. 0.6711g (1.73mmol) of Pt (NH) were then used₃)₄(NO₃)₂And 0.4104g (1.73mmol) of Sn (OAc)₂All SiO was prepared according to the procedure described in example 1₂-TiO₂The material was used for Pt/Sn metal impregnation. Yield: 11.98g of dark gray 1/16 inch extrudate.

Example 13 comparative

SiO₂-WO₃(10) -Pt (3) -Sn (1.8). WO is prepared as follows₃-a modified silica support. Will be 1.24g (0.42mmol) of (NH)₄)₆H₂W₁₂O₄₀·nH₂A solution of O (AMT) in deionized water (14ml) was added dropwise to 10.0g SiO in a 100ml round bottom flask₂NPSGSS61138 catalyst carrier (SA 250 m)²1/16 inch extrudates). The flask was left to stand at room temperature for 2 hours, and then evacuated using a rotary evaporator (bath temperature 80 ℃) until dry. The resulting material was dried overnight at 120 ℃ under circulating air, followed by calcination at 500 ℃ for 6 hours. 0.6711g (1.73mmol) of Pt (NH) were then used₃)₄(NO₃)₂And 0.4104g (1.73mmol) of Sn (OAc)₂All (pale yellow) SiO were prepared according to the procedure described in example 1₂-WO₃The material was used for Pt/Sn metal impregnation. Yield: 12.10g of dark gray 1/16 inch extrudate.

Example 14-hydrogenation of acetic acid over catalysts from examples 1-13 and Gas Chromatography (GC) analysis of the caide ethanol product

The catalysts of examples 1-13 were tested to determine the selectivity and yield of ethanol as shown in table 4.

The reaction feed liquid of acetic acid was vaporized and charged to the reactor with hydrogen and helium as carrier gas at the average total Gas Hourly Space Velocity (GHSV), temperature and pressure shown in table 4. The feed stream contained a molar ratio of hydrogen to acetic acid as shown in table 4.

Analysis of the product (crude ethanol composition) was performed by online GC. The reactants and products were analyzed using a three-channel integrated GC equipped with 1 Flame Ionization Detector (FID) and 2 Thermal Conductivity Detectors (TCD). The front channel was equipped with FID and CP-Sil 5(20m) + WaxFFap (5m) columns and used for quantification: acetaldehyde; ethanol; acetone; methyl acetate; vinyl acetate; ethyl acetate; acetic acid; ethylene glycol diacetate; ethylene glycol; ethylidene diacetate; and paraldehyde. The intermediate channel was equipped with TCD and Porabond Q columns and used for quantization: CO 2₂(ii) a Ethylene; and ethane. The back channel was equipped with TCD and Molsieve 5A columns and used for quantification: helium gas; hydrogen gas; nitrogen gas; methane;and carbon monoxide.

Prior to the reaction, the retention times of the different components were determined by spiking with individual compounds and the GC was calibrated with a calibration gas of known composition or with a liquid solution of known composition. This allows the response factors of the individual components to be determined.

Example 15 catalyst stability (15 hours)

At a temperature of about 225 deg.C, a pressure of 200psig (about 1400KPag) and GHSV of 6570h^-1A molar ratio of hydrogen to acetic acid of about 5: 1 (feed rate of 0.09g/min HOAc; 160sccm/min H)₂；60sccm/min N₂) Passing the vaporized acetic acid and hydrogen over a hydrogenation catalyst of the present invention, the hydrogenation catalyst comprising a catalyst having a surface area of about 250m²3 wt.% Pt, 1.5 wt.% Sn, and 5 wt.% CaSiO as promoter on high purity, high surface area silica/g₃. The use of 5% CaSiO in the hydrogenation of acetic acid with 5% CaSiO in a fixed bed continuous reactor system to produce primarily ethanol, acetaldehyde and ethyl acetate by hydrogenation and esterification reactions at 225 ℃ for 15 hours duration was investigated using 2.5ml of a solid catalyst (14/30 mesh, diluted 1: 1(v/v, with quartz chips, 14/30 mesh) within a typical range of operating conditions₃Stabilized SiO₂. Fig. 3A depicts selectivity and fig. 3B depicts catalyst productivity as a function of run time during the initial phase of catalyst life. From the results of this example as reported in fig. 3A and 3B, it can be appreciated that selectivities in excess of 90% and yields in excess of 500g of ethanol per kilogram of catalyst per hour can be obtained.

Example 16 catalyst stability (over 100 hours)

Catalyst stability: SiO 2₂-CaSiO₃(5) -Pt (3) -Sn (1.8). At constant temperature (260 ℃), andevaluation of SiO in the reaction time of over 100 hours₂-CaSiO₃(5) Catalytic performance and initial stability of Pt (3) -Sn (1.8). Only minor changes in catalyst performance and selectivity were observed over a total reaction time of over 100 hours. Acetaldehyde appears to be the only by-product and its concentration (about 3 wt%) remains largely unchanged during the course of the experiment. A summary of catalyst productivity and selectivity is provided in fig. 4A and 4B.

Example 17 catalyst stability

The procedure of example 16 was repeated at a temperature of about 250 ℃. Fig. 5A and 5B depict catalyst productivity and selectivity as a function of run time during the initial phase of catalyst life. From the results of this example as reported in fig. 5A and 5B, it can be appreciated that still more than 90% of the selectivity activity can be obtained, but with a yield of more than 800g of ethanol per kg of catalyst per hour at this temperature.

Example 18

The catalyst of example 3 was used with different loadings of the support modifier CaSiO₃The preparation was carried out and the following catalysts were produced: (i) SiO 2₂-Pt(1.5)-Sn(0.9)；(ii)SiO₂-CaSiO₃(2.5)-Pt(1.5)-Sn(0.9)；(iii)SiO₂-CaSiO₃(5.0)-Pt(1.5)-Sn(0.9)；(iv)SiO₂-CaSiO₃(7.5) -Pt (1.5) -Sn (0.9); and (v) SiO₂-CaSiO₃(10) -Pt (1.5) -Sn (0.9). Under similar conditions, i.e., 1400 bar (200psig), 2500h^-1GHSV of (1) and a 10: 1 molar feed ratio of hydrogen to acetic acid (683sccm/min H₂To 0.183g/min AcOH) at 250 ℃ and 275 ℃ each catalyst was used for the hydrogenation of acetic acid. The conversion is shown in fig. 6A, the yield is shown in fig. 6B, the selectivity at 250 ℃ is shown in fig. 6C, and the selectivity at 275 ℃ is shown in fig. 6D.

As shown in FIG. 6A, in CaSiO₃The conversion of acetic acid at 250 ℃ and 275 ℃ was unexpectedly improved at loadings greater than 2.5 wt.%. 0-2.5% by weight CaSiO₃The transformation exhibitedThe initial decrease in rate suggests that CaSiO increases with the addition of more CaSiO₃The conversion is expected to decrease. However, this trend is unexpectedly maintained with the addition of more support modifier. As shown in fig. 6B, increased conversion also resulted in increased yield. The selectivities in fig. 6C and 6C show a slight increase with increasing amount of support modifier.

Although the present invention has been described in detail, various modifications within the spirit and scope of the invention will be apparent to those skilled in the art. In view of the above discussion, relevant knowledge in the art and references discussed above in relation to the background and detailed description, the disclosures of which are incorporated herein by reference in their entirety. Furthermore, it is to be understood that various aspects of the invention as well as various portions of various embodiments and features recited below and/or in the appended claims may be combined or interchanged either in part or in whole. In the foregoing description of the various embodiments, the embodiments that refer to another embodiment may be combined with other embodiments as appropriate, as will be recognized by those skilled in the art. Furthermore, those skilled in the art will recognize that the foregoing description is by way of example only, and is not intended to limit the present invention.

Claims (16)

1.A process for producing ethanol comprising hydrogenating acetic acid in the presence of a catalyst comprising:

a first metal, wherein the first metal is present in an amount of 0.1 to 25 wt.%, based on the total weight of the catalyst;

a second metal, wherein the second metal is present in an amount of 0.1 to 10 wt.%, based on the total weight of the catalyst;

a silica support, wherein the silica support is present in an amount of 25 wt% to 99 wt%, based on the total weight of the catalyst;

and at least one support modifier, wherein the at least one support modifier is selected from the group consisting of alkaline earth metasilicates, ZnO, and mixtures thereof, and wherein the at least one support modifier is present in an amount of from 0.1 wt.% to 50 wt.%, based on the total weight of the catalyst;

wherein the first metal is platinum and the second metal is tin, or the first metal is palladium and the second metal is rhenium.

2. The process of claim 1 wherein the silica support has a thickness of 50m²/g-600m²Surface area in g.

3. The process of claim 1 wherein the silica support contains less than 1 wt% aluminum based on the total weight of the catalyst.

4. The method of claim 1, wherein the first metal is platinum, the second metal is tin, and the molar ratio of platinum to tin is from 0.4:0.6 to 0.6: 0.4.

5. The process of claim 1, wherein the first metal is palladium, the second metal is rhenium, and the molar ratio of rhenium to palladium is from 0.7:0.3 to 0.85: 0.15.

6. The method of claim 1, wherein the catalyst further comprises a third metal different from the first and second metals.

7. The method of claim 6, wherein the third metal is selected from the group consisting of cobalt, palladium, ruthenium, copper, zinc, platinum, tin, and rhenium.

8. The process of claim 6, wherein the third metal is present in an amount of from 0.05 to 4 wt.%, based on the total weight of the catalyst.

9. The process of claim 1, wherein at least 10% of the acetic acid is converted during hydrogenation.

10. The process of claim 1, wherein the hydrogenation has an ethanol selectivity of at least 80%.

11. The process of claim 10, wherein the hydrogenation has a selectivity to methane, ethane, and carbon dioxide and mixtures thereof of less than 4%.

12. The process of claim 1, wherein the catalyst has a productivity that decreases by less than 6% per 100 hours of catalyst usage.

13. The method of claim 1, wherein the acetic acid is derived from a coal source, a natural gas source, or a biomass source.

14. The process of claim 1, further comprising dehydrating the ethanol obtained during hydrogenation to produce ethylene.

15. The process of claim 1, wherein the hydrogenation is carried out in the vapor phase at a temperature from 125 ℃ to 350 ℃, a pressure from 10kPa to 3000kPa, and a hydrogen to acetic acid molar ratio of greater than 4: 1.

16. The process of claim 1, wherein the ethanol is a crude ethanol product comprising:

(a) ethanol in an amount of 15-70 wt%;

(b) acetic acid in an amount of 0-80 wt%;

(c) water in an amount of 5-30 wt%; and

(d) any other compound in an amount of less than 10 wt%,

wherein all weight percents are based on the total weight of the caide ethanol product.