HK1168066A - Processes for making ethanol or ethyl acetate from acetic acid using bimetallic catalysts - Google Patents

Description

Method for preparing ethanol or ethyl acetate from acetic acid using bimetallic catalyst

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 generally relates to a process for hydrogenating acetic acid to form ethanol and/or ethyl acetate depending on the molar ratio of the metals in the bimetallic catalyst.

Background

There is a long felt need for an economically viable process for converting acetic acid to ethanol and/or ethyl acetate. 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. Carboxylic acids and derivatives" 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).

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. patent 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 a group VIII metal alloy catalyst. 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)₂) 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.

Depending on, for example, market conditions, it may be desirable to control the relative amounts of ethanol and ethyl acetate formed in the catalytic hydrogenation of acetic acid. Thus, there is a need for methods and catalysts for controlling the type and relative amounts of various products formed in the hydrogenation of acetic acid.

Summary of The Invention

The present invention relates to a process for the selective preparation of ethanol, ethyl acetate or a mixture of ethanol and ethyl acetate by hydrogenation of acetic acid. It has now been found that the relative amounts of ethanol and ethyl acetate formed in the hydrogenation of acetic acid can be advantageously controlled based on the molar ratio of the metals used in the hydrogenation catalyst.

In one embodiment, the catalyst comprises platinum and tin and is selective for the production of ethanol. In this aspect, the invention relates to a process for producing ethanol comprising hydrogenating acetic acid in the presence of a catalyst comprising platinum, tin, and at least one support, wherein the molar ratio of platinum to tin is from 0.4: 0.6 to 0.6: 0.4.

In another embodiment, the catalyst comprises rhenium and palladium and is selective for the production of ethanol. In this aspect, the invention relates to a process comprising hydrogenating acetic acid in the presence of a catalyst comprising rhenium, palladium, and at least one support, wherein the molar ratio of rhenium to palladium is from 0.7: 0.3 to 0.85: 0.15.

In embodiments where ethanol is the desired product, the catalyst preferably further comprises at least one support modifier selected from the group consisting of: (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. For example, the at least one support modifier is optionally selected from oxides and metasilicates of sodium, potassium, magnesium, calcium, scandium, yttrium, and zinc and may be present in an amount of from 0.1 wt.% to 50 wt.%, based on the total weight of the catalyst. The hydrogenation is preferably carried out in the vapor phase at a temperature of from 125 ℃ to 350 ℃, a pressure of from 10KPa to 3000KPa and a hydrogen to acetic acid molar ratio of greater than 4: 1.

In another embodiment, the catalyst comprises platinum and tin and is selective for the production of ethyl acetate. In this aspect, the invention relates to a process for producing ethyl acetate comprising hydrogenating acetic acid in the presence of a catalyst comprising platinum, tin and at least one support, wherein the molar ratio of platinum to tin is less than 0.4: 0.6 or greater than 0.6: 0.4.

In another embodiment, the catalyst comprises rhenium and palladium and is selective for the production of ethyl acetate. In this aspect, the invention relates to a process for producing ethyl acetate comprising hydrogenating acetic acid in the presence of a catalyst comprising rhenium, palladium, and at least one support, wherein the molar ratio of rhenium to palladium is less than 0.7: 0.3 or greater than 0.85: 0.15.

In embodiments where ethyl acetate is the desired product, the catalyst may further comprise at least one support modifier selected from the group consisting of oxides of group IVB metals, oxides of group VB metals, oxides of group VIB metals, iron oxides, aluminum oxides, and mixtures thereof, e.g., at least one support modifier selected from WO₃、MoO₃、Fe₂O₃、Cr₂O₃、TiO₂、ZrO₂、Nb₂O₅、Ta₂O₅And Al₂O₃. The at least one support modifier may be present, for example, in an amount of from 0.1 wt.% to 50 wt.%, based on the total weight of the catalyst.

In each of the above embodiments, the hydrogenation is preferably carried out in the vapor phase at a temperature of from 125 ℃ to 350 ℃, a pressure of from 10KPa to 3000KPa, and a hydrogen to acetic acid molar ratio of greater than 4: 1. The support is optionally present in an amount of 25 wt.% to 99 wt.%, based on the total weight of the catalyst, and preferably has a weight average molecular weight of 5 wt.%0m²/g-600m²Surface area in g. The support may be selected from, for example, silica/alumina, calcium metasilicate, pyrogenic silica, high purity silica and mixtures thereof. The support optionally contains less than 1 wt.% aluminum, based on the total weight of the catalyst. The catalyst also preferably has a productivity that decreases by less than 6% per 100 hours of catalyst use.

According to the above embodiment, at least 10% of the acetic acid is preferably converted during hydrogenation, the hydrogenation preferably having a selectivity to ethanol or ethyl acetate of at least 50% or at least 60% as desired, and a selectivity to methane, ethane, and carbon dioxide, and mixtures thereof of less than 4%.

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 is a diagram of the use of SiO according to one embodiment of the present invention₂-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 diagram of the use of SiO according to one embodiment of the present invention₂-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; and

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

Detailed Description

The present invention relates to a process for the production of ethanol and/or ethyl acetate by hydrogenating acetic acid in the presence of a bimetallic catalyst. It has now been found that the relative amounts of ethanol and ethyl acetate formed in the hydrogenation of acetic acid can be advantageously controlled based on the molar ratio of the metals used in the hydrogenation catalyst. In one embodiment, the bimetallic catalyst comprises platinum and tin. In another embodiment, the bimetallic catalyst comprises rhenium and palladium.

The hydrogenation of acetic acid to ethanol may be represented as follows:

in embodiments where the catalyst comprises platinum and tin, the Pt/Sn molar ratio is preferably from 0.4: 0.6 to 0.6: 0.4, for example from 0.45: 0.55 to 0.55: 0.45 or about 1: 1, depending on the reaction being favorable to selectivity to ethanol. In embodiments where the catalyst comprises rhenium and palladium, the molar ratio of Re/Pd is preferably in the range of from 0.6: 0.4 to 0.85: 0.15, for example from 0.7: 0.3 to 0.85: 0.15, or about 0.75: 0.25, in favor of selectivity to ethanol.

The hydrogenation of acetic acid to form ethyl acetate may be represented as follows:

in embodiments where the catalyst comprises platinum and tin, the Pt/Sn molar ratio is preferably less than 0.4: 0.6 or greater than 0.6: 0.4, depending on whether the above reaction is selective to ethyl acetate. More effectively, for this embodiment, the Pt/Sn molar ratio is from 0.65: 0.35 to 0.95: 0.05, such as from 0.7: 0.3 to 0.95: 0.05. In another embodiment, the Pt/Sn molar ratio is from 0.05: 0.95 to 0.35: 0.65. To favor selectivity to ethyl acetate in embodiments where the catalyst comprises rhenium and palladium, the molar ratio of Re/Pd is preferably less than 0.7: 0.3 or greater than 0.85: 0.15. More effectively, for this embodiment, the Pt/Sn molar ratio is from 0.05: 0.95 to 0.7: 0.3, such as from 0.1: 0.9 to 0.6: 0.4. In another embodiment, the Pt/Sn molar ratio is from 0.85: 0.15 to 0.95: 0.05.

It is understood that ethyl acetate may also be formed using a method that favors the formation of a catalyst for ethanol, and conversely, ethanol may also be formed using a method that favors the formation of a catalyst for ethyl acetate. For the purposes of the present invention, the catalyst favors the formation of ethanol or ethyl acetate when the selectivity to one product is greater than to the other. According to embodiments of the present invention, selectivities to ethanol or ethyl acetate of greater than 50%, such as greater than 75% or greater than 80%, may 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 conversions, e.g., at least 80% or at least 90%, are desirable, low conversions may also be acceptable when the selectivity to the desired product, e.g., ethanol or ethyl acetate, is high. It is, of course, well understood that in many cases conversion can be compensated for by incorporating recycle streams or using larger reactors, but it is generally more difficult to compensate for poor selectivity.

As used herein, "selectivity" is expressed in terms of 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 referred to as 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. Of course, the selectivity to ethyl acetate can be similarly calculated by replacing mmol EtOH (GC) with mmol EtOAc (GC) in the above equation.

For the purposes of the present invention, the selectivity of the catalyst to ethoxylates is preferably at least 60%, for example at least 70% or at least 80%. As used herein, the term "ethoxylate" refers specifically to the compounds ethanol and ethyl acetate. In embodiments where ethanol is the desired product, the selectivity to ethanol is preferably at least 60%, e.g., at least 75% or at least 80%. In embodiments where ethyl acetate is the desired product, the selectivity to ethyl acetate is preferably at least 50%, for example at least 75% or at least 80%. It is also generally desirable to have low selectivity to undesirable products such as methane, ethane, and carbon dioxide. The selectivity to these undesired products is preferably less than 4%, for example less than 2% or less than 1%. Ideally, no detectable amounts of these undesirable products are formed during hydrogenation. In several embodiments of the invention, alkane production is low. For example, in preferred embodiments less than 2%, less than 1%, or less than 0.5% of the acetic acid passing through the catalyst is converted to alkanes, which have little value other than as fuel.

In embodiments of the invention, the first metal, e.g., platinum or palladium, 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, e.g. tin or rhenium, is preferably present in an amount of 0.1 to 20 wt.%, e.g. 0.1 to 10 wt.% or 0.1 to 5 wt.%. In such catalysts, the two or more metals may be alloyed with each other or may comprise a non-alloyed metal solid solution or mixture. Unless otherwise indicated, all catalyst metal loadings expressed herein are provided in weight percent based on the total weight of the catalyst including all metals, the support, and the support modifier, if present.

In some embodiments, the catalyst further comprises a third metal, preferably selected from the group consisting of cobalt, palladium, ruthenium, copper, zinc, platinum, tin, and rhenium. More preferably, the third metal (if present) is selected from cobalt, palladium and ruthenium. When present, the total weight of the third metal is preferably 0.05 to 4 wt.%, e.g., 0.1 to 3 wt.% or 0.1 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 metal, the catalyst of the present invention further comprises a support, optionally including a support modifier. As will be appreciated by those skilled in the art, the support material should be selected such that the catalyst system has suitable activity, selectivity and robustness (robust) under the process conditions used to form the desired product, e.g., ethanol and/or ethyl acetate. Suitable support materials may include, for example, stable metal oxide-or ceramic-based supports and molecular sieves, such as zeolites. Examples of suitable support materials include, but are not limited to, iron oxides (iron oxides), silica, alumina, silica/alumina, titania, zirconia, magnesia, group IIA silicates such as calcium metasilicate, carbon, graphite, high surface area graphitized carbon, activated carbon, and mixtures thereof.

Preferred supports include silica, silica/alumina, group IIA silicates such as calcium metasilicate, pyrogenic silica, high purity silica and mixtures thereof. It has been found that increasing the acidity of the support compared to ethanol tends to increase the selectivity to ethyl acetate and vice versa. Thus, in the case where silica is used as the support, particularly if ethanol is the desired product, it may be advantageous to ensure that the amount of aluminum (which is a common acidic contaminant of 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. In this regard, fumed silica may be preferred because it is generally obtained in a purity of over 99.7 wt.%. As used throughout this application, high purity silica refers to silica in which acidic contaminants such as aluminum (if any) are present at a level of less than 0.3 wt.%, e.g., less than 0.2 wt.% or less than 0.1 wt.%. The aluminum content of such silica may be, for example, less than 10 wt.%, such as less than 5 wt.% or less than 3 wt.%, based on the total weight of the silica including any contaminants contained therein. When calcium metasilicate is used as the support modifier, it is not necessary to be very critical as to the purity of the silica used as the support material, even if the desired product is ethanol. In the case where the support comprises from 2 wt.% to 10 wt.% of a basic support modifier, substantial amounts of acidic impurities, such as aluminum, may be tolerated as long as they are substantially balanced by a suitable amount of the support modifier.

The support material (optionally a siliceous support material) preferably has a surface area of 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 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 support material, e.g., a 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 thus the morphology of the resulting catalyst composition 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 support material, e.g. a siliceous support material, has a permissible bulk density of 0.1-1.0g/cm³For example, 0.2 to 0.9g/cm³Or 0.5-0.8g/cm³The form of (1). The 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, with average particle diameter being the diameter of spherical particles or the equivalent spherical diameter of non-spherical particles. Since the sizes of the various metals located on or within the modified support are generally 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.

A preferred silica support material is a SS61138 High Surface Area (HSA) silica catalyst support from Saint Gobain NorPro. Saint-Gobain NorPro SS61138 silica contained 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(22 1b/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.

The total weight of the support (optionally including the support modifier) is preferably from 75 wt.% to 99.9 wt.%, e.g., from 78 wt.% to 97 wt.% or from 80 wt.% to 95 wt.%, based on the total weight of the catalyst.

As indicated above, in some embodiments, the support further comprises a support modifier, which can, for example, adjust the acidity of the support material. The acidity of the support material may be adjusted, for example, by the introduction of one or more of a basic support modifier, an acidic support modifier, or a redox-type support modifier.

In one embodiment, the acid sites on the support material are asThe acid sites can be adjusted by the support modifier to favor selectivity to ethanol or ethyl acetate during the hydrogenation of acetic acid as desired. The acidity of the support material can be reduced, for example, by reducing the acidity of the support materialThe number of acid sites or reduction in the support materialThe availability of acid sites is adjusted to favor the formation of ethanol. 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 surface acidity or the number of acid sites thereon can be edited by f.delannay, "Characterization of heterogenous catalysis"; 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.

In a preferred embodiment, particularly for ethanol formation, 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) alkaline earth metal oxide, (ii) alkali metal oxide, (iii) alkaline earth metal metasilicate, (iv) alkali metal metasilicate, (v) group IIB metal oxide,(vi) Group IIB metal metasilicates, (vii) group IIIB metal oxides, (viii) group IIIB metal metasilicates, and mixtures thereof. In addition to oxides and metasilicates, other types of modifiers including nitrates, nitrites, acetates, and lactates may be used in various embodiments of the present invention. In a preferred embodiment for forming ethanol, 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. In a particularly preferred embodiment, the support modifier is calcium silicate, more preferably calcium metasilicate (CaSiO)₃). If the support modifier comprises calcium metasilicate, at least a portion of the calcium metasilicate is preferably in crystalline form. In a preferred embodiment for forming ethanol, the support modifier comprises a basic support modifier in an amount from 0.1 wt.% to 50 wt.%, e.g., 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 one embodiment, which is preferred for the formation of ethanol, the catalyst comprises a modified support comprising a support material and an effective balance of alumina produced, for example, from silicaCalcium metasilicate as a support modifier in the amount of acid sites. For example, the calcium metasilicate may be present in an amount of 1 wt.% to 10 wt.%, based on the total weight of the catalyst, 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, 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 a high surface area silica, to offset such effects due to the inclusion of the support modifier.

In another embodiment, which is generally preferred for the formation of ethyl acetate, the support comprises an acidic or redox support modifier.Examples of such support modifiers include, for example, those selected from the group consisting of group IVB metal oxides, group VB metal oxides, group VIB metal oxides, iron oxides, aluminum oxides, and mixtures thereof. Preferred redox type support modifiers include those selected from WO₃、MoO₃、Fe₂O₃And Cr₂O₃Those of (a). Preferred acidic support modifiers include those selected from TiO₂、ZrO₂、Nb₂O₅、Ta₂O₅And Al₂O₃Those of (a). In these aspects, the support modifier preferably has low volatility or is non-volatile. 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).

The catalyst of the present invention is a particulate catalyst in the sense that it is not impregnated into a washcoat 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 and/or ethyl acetate. It will therefore be appreciated that the catalyst of the present invention is fully capable of commercial scale industrial application for the hydrogenation of acetic acid, particularly for the production of ethanol and/or ethyl acetate. 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 achieved a steady state condition.

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 prolonged or stabilized at greater than 2500hr in the presence of acetic acid vapor at a temperature of 125 ℃ to 350 ℃^-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 invention is preferably formed by metal impregnation of the support or modified support, although other methods such as chemical vapor deposition may also be used. Prior to impregnation of the metal, it is generally desirable to form the modified support, if necessary, by a step of impregnating the support 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 in which the support modifier is added 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 can be extruded, granulated, tabletted,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 support or 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 support or modified support from a second metal precursor. If desired, a third metal or third metal precursor may also be impregnated into the support or modified support.

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 support or 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 support or 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 support or 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 support or 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. A particularly preferred precursor for platinum is platinum ammine nitrate, i.e., Pt (NH)₃)₄(NO₄)₂. Generally, from the viewpoint of both economic and environmental aspects, an aqueous solution is preferred. In one embodiment, the first metal precursor and the second metal precursor are not metal halides and are substantially free of metal halides. While not being bound by theory, it is believed that such non- (metal halide) precursors enhance ethanol selectivity.

In one aspect, the "promoter" metal or metal precursor is first added to a support, such as a modified support, followed by a "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. Again, 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 form ethanol and/or ethyl acetate 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 invention, the hydrogenation is carried out at a selected GHSV at a pressure just sufficient to overcome the pressure drop across the catalyst bed, although the use of higher pressures is not limited, but is understood to be at high space velocities, e.g., 5000hr^-1Or 6,500hr^-1May experience a significant pressure drop through the reactor bed.

The actual molar ratio of hydrogen to acetic acid in the feed stream may be in the range of about 100: 1 to 1: 100, for example 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 variables such as 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.

The yield refers to the grams of a given product, e.g., ethanol or ethyl acetate, formed per hour during hydrogenation based on kilograms of catalyst used. For embodiments in which ethanol is the preferred product, a yield of at least 200 grams of ethanol, for example at least 400 grams of ethanol or at least 600 grams of ethanol, per kilogram of catalyst per hour is preferred. In terms of ranges, the yield is preferably 200-.

If ethyl acetate is the desired product, a yield of at least 200 grams of ethyl acetate per kilogram of catalyst per hour, for example at least 400 grams of ethyl acetate or at least 600 grams of ethyl acetate, is preferred. In terms of ranges, the yield is preferably 200-3,000 g of ethyl acetate per kg of catalyst per hour, for example 400-2,500 or 600-2,000.

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 from the hydrogenation process of the present invention can be used as a fuel by itself or subsequently converted to ethylene, which is an important commodity 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 ethyl acetate obtained by the present invention can be used as such, polymerized or converted to ethylene by cracking processes. The cleavage of ethyl acetate to give ethylene is shown below.

The cracking may be a catalytic reaction using a cracking catalyst. Suitable cracking catalysts include the sulfonic acid resins disclosed in U.S. patent No.4,399,305, for example perfluorosulfonic acid resins, the disclosure of which is incorporated herein by reference, as described above. Zeolites are also suitable as cracking catalysts, as described in U.S. Pat. No.4,620,050, the disclosure of which is incorporated herein by reference.

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 operations 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.

Examples 1 to 5SiO₂-Pt_mSn_1-m(0＜m＜1)

5 materials were prepared by varying the mole fraction of Pt while maintaining a total metal amount (Pt + Sn) of 1.20 mmol. The following preparations describe example 1, SiO₂-Pt_0.5Sn_0.5(i.e., m is 0.5; the two metals are in an equimolar ratio). Using an appropriate amount of the metal precursor Pt (NH)₃)₄(NO₃)₂And Sn (OAc)₂The remaining preparations were carried out in the same way (i.e. m ═ 0, 0.25, 0.75 and 1.00; examples 2,3, 4 and 5, respectively). The catalyst is prepared by firstly mixing Sn (OAc)₂(tin acetate, Sn (OAc) from Aldrich)₂) (0.1421g, 0.60mmol) 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 0.2323g (0.60 g) were addedmmol) solid Pt (NH)₃)₄(NO₃)₂(Aldrich). The mixture was stirred at room temperature for a further 15 minutes and then added dropwise to 5.0g of dry SiO in a 100ml round-bottomed flask₂Catalyst support (high purity silica catalyst support HSA SS #61138, SA 250 m)²/g；SZ#61152，SA＝156m²(ii)/g; Saint-Gobain NorPro). The metal solution was continuously stirred until all the Pt/Sn mixture was added to the SiO₂The catalyst support was simultaneously rotated after each addition of the metal solution. 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: 5.2g of dark grey material.

In example 1, the weight percent of the catalyst was 2.3 wt.% platinum and 1.4 wt.% tin. The weight percentages for example 3 were 1.1 wt.% platinum and 2.1 wt.% tin and example 4 was 3.4 wt.% platinum and 0.7 wt.% tin. Example 2, which contained no platinum, contained 2.7 wt% tin and example 5, which contained no tin, contained 4.5 wt% platinum.

Example 6 SiO₂-CaSiO₃(5)-Pt(3)-Sn(1.8)

As previously described, the material is prepared by first forming 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) was prepared. The suspension was stirred at room temperature for 2 hours and then 10.0g SiO was added using the incipient wetness 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 hoursThen (c) is performed. 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 examples 1-5₂-CaSiO₃The material was used for Pt/Sn metal impregnation. Yield: 11.21g of dark grey material.

Examples 7 to 11 SiO₂-Re_nPd_1-n(0＜n＜1)。

5 materials were prepared by varying the mole fraction of Re while maintaining a total metal amount (Re + Pd) of 1.20 mmol. The following preparations describe SiO₂-Re_0.5Pd_0.5(i.e., n is 0.5; the two metals are in an equimolar ratio). Using the appropriate amount of metal precursor NH₄ReO₄And Pd (NO)₃)₂The remaining preparations were performed similarly (i.e. x ═ 0, 0.25, 0.75, and 1.00). The metal solution is prepared by first reacting NH₄ReO₄(0.1609g, 0.60mmol) was added to a vial containing 6.75ml of deionized water for preparation. The mixture was stirred at room temperature for 15 minutes, then 0.1154g (0.60mmol) of solid Pd (NO) were added₃)₂. The mixture was stirred at room temperature for a further 15 minutes and then added dropwise to 5.0g of dry SiO in a 100ml round-bottomed flask₂Catalyst support (14/30 mesh). 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. All other treatments (drying, calcination) were carried out as described above for examples 1-5. Yield: 5.1g of brown material.

Example 12-Gas Chromatography (GC) analysis of acetic acid hydrogenation and crude ethanol product over catalysts from examples 1-11

The catalysts of examples 1-11 were tested to determine the selectivity and yield of ethanol as shown in table 1.

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 1. The feed stream contained a molar ratio of hydrogen to acetic acid as shown in table 1. FIGS. 1A-1C also depict the performance of the catalysts of examples 1-5, and FIGS. 2A-2C depict the performance of the catalysts of examples 7-11.

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.

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 (65)

1. A process for producing ethanol comprising hydrogenating acetic acid in the presence of a catalyst comprising platinum, tin, and at least one support, wherein the molar ratio of platinum to tin is from 0.4: 0.6 to 0.6: 0.4.

2. The process of claim 1, wherein the support is present in an amount of 25 wt.% to 99 wt.%, based on the total weight of the catalyst.

3. The method of claim 1, wherein the vector has50m²/g-600m²Surface area in g.

4. The process of claim 1 wherein the support is selected from the group consisting of silica, silica/alumina, calcium metasilicate, pyrogenic silica, high purity silica and mixtures thereof.

5. The process of claim 4, wherein the support contains less than 1 wt.% aluminum, based on the total weight of the catalyst.

6. The process of claim 1, wherein the catalyst further comprises at least one support modifier selected from the group consisting of: (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.

7. The process of claim 6, wherein the at least one support modifier is selected from the group consisting of oxides and metasilicates of sodium, potassium, magnesium, calcium, scandium, yttrium, and zinc.

8. The process of claim 6, 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.

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 60%.

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 of acetic acid also produces ethyl acetate.

16. 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.

17. A process for producing ethyl acetate comprising hydrogenating acetic acid in the presence of a catalyst comprising platinum, tin and at least one support, wherein the molar ratio of platinum to tin is less than 0.4: 0.6 or greater than 0.6: 0.4.

18. The process of claim 17, wherein the molar ratio of platinum to tin is from 0.65: 0.35 to 0.95: 0.05.

19. The process of claim 17, wherein the molar ratio of platinum to tin is from 0.05: 0.95 to 0.35: 0.65.

20. The process of claim 17, wherein the support is present in an amount of 25 wt.% to 99 wt.%, based on the total weight of the catalyst.

21. The method of claim 17, wherein the vector has a length of 50m²/g-600m²Surface area in g.

22. The process of claim 17, wherein the support is selected from the group consisting of silica, silica/alumina, calcium metasilicate, pyrogenic silica, high purity silica, and mixtures thereof.

23. The process of claim 17, wherein the catalyst further comprises at least one support modifier selected from the group consisting of: group IVB metal oxides, group VB metal oxides, group VIB metal oxides, iron oxides, aluminum oxides, and mixtures thereof.

24. The method of claim 23, wherein the at least one support modifier is selected from WO₃、MoO₃、Fe₂O₃、Cr₂O₃、TiO₂、ZrO₂、Nb₂O₅、Ta₂O₅And Al₂O₃。

25. The process of claim 23, 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.

26. The process of claim 17, wherein at least 10% of the acetic acid is converted during hydrogenation.

27. The process of claim 17, wherein the hydrogenation has a selectivity to ethyl acetate of at least 50%.

28. The process of claim 27, wherein the hydrogenation has a selectivity to methane, ethane, and carbon dioxide and mixtures thereof of less than 4%.

29. The method of claim 17, wherein the catalyst has a productivity that decreases by less than 6% per 100 hours of catalyst usage.

30. The method of claim 17, wherein the acetic acid is obtained from a coal source, a natural gas source, or a biomass source.

31. The process of claim 17, wherein the hydrogenation of acetic acid also produces ethanol.

32. The process of claim 17, 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.

33. A process for producing ethanol, comprising hydrogenating acetic acid in the presence of a catalyst comprising rhenium, palladium, and at least one support, wherein the molar ratio of rhenium to palladium is from 0.7: 0.3 to 0.85: 0.15.

34. The method of claim 33, wherein the molar ratio of rhenium to palladium is about 0.75: 0.25.

35. The process of claim 33, wherein the support is present in an amount of 25 wt.% to 99 wt.%, based on the total weight of the catalyst.

36. The method of claim 33, wherein the vector has a length of 50m²/g-600m²Surface area in g.

37. The process of claim 33, wherein the support is selected from the group consisting of silica, silica/alumina, calcium metasilicate, pyrogenic silica, high purity silica, and mixtures thereof.

38. The process of claim 37, wherein the support contains less than 1 wt.% aluminum, based on the total weight of the catalyst.

39. The process of claim 33, wherein the catalyst further comprises at least one support modifier selected from the group consisting of: (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.

40. The process of claim 39, wherein the at least one support modifier is selected from the group consisting of oxides and metasilicates of sodium, potassium, magnesium, calcium, scandium, yttrium, and zinc.

41. The process of claim 39, wherein the at least one support modifier is present in an amount from 0.1 wt.% to 50 wt.%, based on the total weight of the catalyst.

42. The process of claim 33, wherein at least 10% of the acetic acid is converted during hydrogenation.

43. The process of claim 33, wherein the hydrogenation has an ethanol selectivity of at least 60%.

44. The process of claim 43, wherein the hydrogenation has a selectivity to methane, ethane, and carbon dioxide and mixtures thereof of less than 4%.

45. The method of claim 33, wherein the catalyst has a productivity that decreases by less than 6% per 100 hours of catalyst usage.

46. The method of claim 33, wherein the acetic acid is obtained from a coal source, a natural gas source, or a biomass source.

47. The process of claim 33, comprising dehydrating ethanol obtained during hydrogenation to produce ethylene.

48. The process of claim 33, wherein the hydrogenation of acetic acid also produces ethyl acetate.

49. The process of claim 33, 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.

50. A process for producing ethyl acetate comprising hydrogenating acetic acid in the presence of a catalyst comprising rhenium, palladium, and at least one support, wherein the molar ratio of rhenium to palladium is less than 0.7: 0.3 or greater than 0.85: 0.15.

51. The process of claim 50 wherein the molar ratio of rhenium to palladium is from 0.05: 0.95 to 0.7: 0.3.

52. The process of claim 50 wherein the molar ratio of rhenium to palladium is from 0.85: 0.15 to 0.95: 0.05.

53. The process of claim 50, wherein the support is present in an amount of from 25 wt.% to 99 wt.%, based on the total weight of the catalyst.

54. The method of claim 50, wherein the vector has a length of 50m²/g-600m²Surface area in g.

55. The process of claim 50, wherein the support is selected from the group consisting of silica, silica/alumina, calcium metasilicate, pyrogenic silica, high purity silica, and mixtures thereof.

56. The method of claim 50, wherein at least one support modifier is included, said support modifier selected from the group consisting of: group IVB metal oxides, group VB metal oxides, group VIB metal oxides, iron oxides, aluminum oxides, and mixtures thereof.

57. The method of claim 56, wherein the at least one support modifier is selected from WO₃、MoO₃、Fe₂O₃、Cr₂O₃、TiO₂、ZrO₂、Nb₂O₅、Ta₂O₅And Al₂O₃。

58. The process of claim 56, 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.

59. The process of claim 50, wherein at least 10% of the acetic acid is converted during hydrogenation.

60. The process of claim 50, wherein the hydrogenation has a selectivity to ethyl acetate of at least 50%.

61. The process of claim 60, wherein the hydrogenation has a selectivity to methane, ethane, and carbon dioxide and mixtures thereof of less than 4%.

62. The method of claim 50, wherein the catalyst has a productivity that decreases by less than 6% per 100 hours of catalyst usage.

63. The method of claim 50, wherein the acetic acid is obtained from a coal source, a natural gas source, or a biomass source.

64. The process of claim 50, wherein the hydrogenation of acetic acid also produces ethanol.

65. The process of claim 50, 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.