DE102011086451A1 - METHANOL SYNTHESIS CATALYST BASED ON COPPER, ZINC AND ALUMINUM - Google Patents

Abstract

The present invention relates to a catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum, wherein Cu and Zn are present together in a larger molar amount than aluminum and the carbonates and oxides form a homogeneous phase, as well as the catalyst material, that results from the reduction of this precursor. The catalyst material comprises discrete crystalline Cu particles partially embedded in a continuous homogeneous phase comprising oxides and carbonates of at least Zn and Al, wherein in the catalyst material Cu and Zn are present together in greater molar amount than aluminum and the molar ratio of Cu and Zn is preferably 0.5 / 1 to less than 2.8 / 1, and the Al content is 1 to 30 mol% based on all metal components. The invention also relates to a particular method of making this catalyst. The catalyst shows excellent efficiency and stability in the synthesis of methanol from synthesis gas.

Description

The present invention relates to a catalyst containing catalytically active copper particles embedded in a zinc and aluminum-containing phase and its use in the production of methanol from synthesis gas.

BACKGROUND OF THE INVENTION

Global demand for methanol, which is one of the major commodity chemicals, is more than 30 million tons per year, and it is predicted that its importance will continue to increase in the future. Industrially, it is made from synthesis gas, a mixture of hydrogen (H ₂ ), carbon monoxide (CO) and carbon dioxide (CO ₂ ), typically at 35 to 55 bar and 200 to 300 ° C. Since the early pioneering studies of the workers at the ICI, reflected by GB 1 010 871 . GB 1 159 035 and GB 1 296 211 , almost exclusively Cu / ZnO / Al ₂ O ₃ catalysts are used in this industrial reaction. These catalysts are usually prepared in a multi-step synthesis ( Waller et al. Faraday Discuss. Chem. Soc. 1989, 87, 107 ). Co-precipitation of mixed aqueous Cu, Zn and Al nitrate solutions using soda as precipitant is carried out at a constant pH close to 7 followed by an aging period to produce a mixed Cu / Zn / Al hydroxycarbonate precursor, which is calcined to an inseparable mixture of the oxides. Finally, CuO present in this catalyst precursor is reduced to obtain the active catalyst form containing elemental copper.

EP 0 125 689 A2 (= US 4,353,071 ), in the name of Süd-Chemie AG, discloses catalysts of this type, which are characterized by a specific pore size distribution. This document also teaches that the copper / zinc mole ratio is preferably 2.8 to 3.8.

According to DE 101 60 486 A1 (Süd-Chemie AG), Cu / Zn molar ratios of less than 2.8 are indispensable for achieving relatively small and catalytically particularly active copper crystallite sizes. This document also teaches that the alumina component is at least partially recovered from an aluminum hydroxide sol.

Similar catalysts containing alumina derived from a colloidally dispersed aluminum hydroxide sol or gel and containing about 13 to 130 x 10 ^-6 g atoms of alkali metals per gram of the metallic oxide precursor mixture are the subject of US 4,598,061 , also on behalf of Süd-Chemie AG. The catalyst disclosed in this document is also characterized by a pore size distribution, with pores having a diameter of 7.5 to 14 nm making up approximately 20 to 70% of the total pore volume.

US 4,279,781 discloses a low temperature methanol synthesis catalyst comprising copper and zinc oxide in a weight ratio, expressed as metal, of 2: 1 to 3.5: 1. The catalyst preferably comprises a heat stabilizing metal oxide, such as alumina, in low proportions and is obtained by co-precipitation of all three constituents from a single solution of soluble zinc, copper and aluminum salts, such as nitrates, or by the decomposition of copper amincarbonates and zinc amine carbonates a heat-stabilizing metal oxide in the hydrated state, or as a gel. Both production techniques are expected to result in an inhomogeneous composition of the ZnO / Al ₂ O ₃ phase surrounding the particles.

US 3,850,850 and US 3,923,694 (both ICI) refer to spinel-containing Cu / Zn / Al catalysts with relatively high Cu contents. The catalyst according to US 3,923,694 appears to be carbonate-free, as its precursor is characterized by comprising 10 to 80% copper, with the balance consisting essentially of the crystalline spinel structure. On the other hand, it seems that the catalyst according to US 3,850,850 has an inhomogeneous structure since it is taught in the two examples that only 67% and 75.3%, respectively, of the possible spinel content is achieved.

• a) Zubereiten einer ersten wässrigen Lösung, enthaltend mindestens ein wasserlösliches Kupfersalz und mindestens ein wasserlösliches Zinksalz,
• b) Zubereiten einer zweiten Lösung, enthaltend mindestens ein wasserlösliches basisches Aluminiumsalz, wie Natriumaluminat, und mindestens ein alkalisches Fällmittel, wie Natriumcarbonat,
• c) Mischen der ersten und der zweiten Lösung, wobei ein unlöslicher Feststoff gebildet wird,
• d) Gewinnen des unlöslichen Feststoffs, und
• e) Kalzinieren des gewonnenen Feststoffs,

umfasst. EP 0 522 669 A2 , on behalf of Engelhard Corporation, discloses hydrogenation catalysts comprising the oxides of copper, zinc and aluminum. It is taught that these catalysts are useful in the hydrogenation of aldehydes, ketones, carboxylic acids and carboxylic acid esters. The examples examine the hydrogenation activity of the catalyst in the hydrogenation of cocosmethyl ester. The Cu / Zn ratio of these catalysts varies widely. Unlike the catalysts mentioned above, the hydrogenation catalyst according to EP 0 522 669 A2 produced in a process comprising the steps of

• a) preparing a first aqueous solution containing at least one water-soluble copper salt and at least one water-soluble zinc salt,
• b) preparing a second solution containing at least one water-soluble basic aluminum salt, such as sodium aluminate, and at least one alkaline precipitating agent, such as sodium carbonate,
• c) mixing the first and second solutions to form an insoluble solid,
• d) recovering the insoluble solid, and
• e) calcining the recovered solid,

includes.

The recovered precipitate is calcined at a temperature in the range of about 475 ° C to about 700 ° C for about 30 to about 120 minutes. Under these conditions, metal carbonate remaining in the insoluble solid recovered in step d) is converted to the oxide releasing carbon dioxide. It is also expected that complete removal of the carbonate at these high temperatures will increase the crystallinity of the catalyst material.

It is an object of the present invention to provide a novel catalyst (a novel catalyst material) useful in the industrial production of methanol from synthesis gas. Another object of the present invention is to provide a novel methanol synthesis catalyst (methanol synthesis catalyst material) which has excellent catalytic activity and stability.

It is a further object of the present invention to provide a catalyst precursor (catalyst precursor material) which can be reduced in hydrogen to the above high performance catalyst material.

Another object of the present invention is to provide a method of producing the catalyst precursor material, the catalyst material and the corresponding catalyst. Other objects will become apparent from the following detailed description of the present invention.

SUMMARY OF THE PRESENT INVENTION

• (1a) Ein Cu/Zn/Al-Katalysatorvorläufermaterial, umfassend Oxide und Carbonate von Kupfer, Zink und Aluminium, wobei Kupfer und Zink zusammen in einer größeren molaren Menge als Aluminium vorhanden sind, und wobei die Standardabweichung des lokalen molaren Al-Gehalts, wie durch EDX gemessen, nicht mehr als 50% beträgt.
• (1b) Ein Cu/Zn/Al-Katalysatorvorläufermaterial, umfassend Oxide und Carbonate von Kupfer, Zink und Aluminium, wobei Kupfer und Zink zusammen in einer größeren molaren Menge als Aluminium vorhanden sind, und wobei die Reduktion dieses Vorläufermaterials in Gegenwart von Wasserstoff zu einem Katalysatormaterial führt, in dem diskrete kristalline Cu-Partikel teilweise in eine kontinuierliche Phase, umfassend Oxide und Carbonate von mindestens Zn und Al, eingebettet sind, wobei die kristallinen Cu-Partikel eine Gitterkonstante von 3,615 Å oder mehr, bevorzugt 3,615 bis 3,621 Å aufweisen.
• (2) Ein Cu/Zn/Al-Katalysatormaterial, umfassend diskrete kristalline Cu-Partikel, die teilweise in eine kontinuierliche Phase, umfassend Oxide und Carbonate von mindestens Zn und Al, eingebettet sind, wobei im Katalysatormaterial Cu und Zn zusammen in einer größeren molaren Menge als Aluminium vorhanden sind und bevorzugt das molare Verhältnis von Cu und Zn 0,5/1 bis weniger als 2,8/1 ist und der Al-Gehalt 5 bis 30 mol%, basierend auf allen Metallbestandteilen, ist, und wobei die Gitterkonstante der kristallinen Cu-Partikel 3,615 Å oder mehr, bevorzugt 3,615 bis 3,621 Å ist. Dieses Katalysatormaterial wird bevorzugt durch das Reduzieren des obigen Katalysatorvorläufermaterials in Gegenwart von Wasserstoff erhalten.
• (3) Ein Verfahren zum Herstellen des obigen Katalysatorvorläufermaterials, umfassend die Schritte (a) Zubereiten einer ersten wässrigen Lösung, enthaltend mindestens ein wasserlösliches Kupfersalz und mindestens ein wasserlösliches Zinksalz, (b) Zubereiten einer zweiten Lösung, enthaltend mindestens ein wasserlösliches basisches Aluminiumsalz (wie Natriumaluminat) und mindestens ein alkalisches carbonathaltiges Fällmittel (wie Natriumcarbonat), (c) Mischen der ersten und der zweiten Lösung, wobei ein unlöslicher Feststoff gebildet wird, (d) Gewinnen des unlöslichen Feststoffs, (e) Trocknen des gewonnenen Feststoffs, sowie (f) Kalzinieren des getrockneten Feststoffs bei einer Temperatur, die 450°C nicht überschreitet, um das Katalysatorvorläufermaterial zu erhalten.
• (4) Ein Verfahren zur Herstellung von Methanol, umfassend den Schritt des Inkontaktbringens einer Gasmischung, umfassend Wasserstoff, Kohlenmonoxid und Kohlendioxid, mit dem oben beschriebenen Katalysatormaterial.

The main embodiments of the present invention may be summarized as follows:

• (1a) A Cu / Zn / Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum, wherein copper and zinc are present together in a molar amount greater than aluminum, and wherein the standard deviation of the local molar Al content, such as measured by EDX is not more than 50%.
• (1b) A Cu / Zn / Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum, wherein copper and zinc are present together in a molar amount greater than aluminum, and wherein reduction of said precursor material in the presence of hydrogen Catalyst material in which discrete crystalline Cu particles are partially embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al, wherein the crystalline Cu particles have a lattice constant of 3.615 Å or more, preferably 3.615 to 3.621 Å.
• (2) A Cu / Zn / Al catalyst material comprising discrete crystalline Cu particles partially embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al, wherein in the catalyst material Cu and Zn together in a larger molar And the molar ratio of Cu and Zn is 0.5 / 1 to less than 2.8 / 1, and the Al content is 5 to 30 mol% based on all metal components, and wherein the lattice constant the crystalline Cu particle is 3.615 Å or more, preferably 3.615 to 3.621 Å. This catalyst material is preferably obtained by reducing the above catalyst precursor material in the presence of hydrogen.
• (3) A process for producing the above catalyst precursor material, comprising the steps of (a) preparing a first aqueous solution containing at least one water-soluble copper salt and at least one water-soluble zinc salt, (b) preparing a second solution containing at least one water-soluble basic aluminum salt (such as Sodium aluminate) and at least one alkaline carbonated precipitant (such as sodium carbonate), (c) mixing the first and second solutions to form an insoluble solid, (d) recovering the insoluble solid, (e) drying the recovered solid, and (f) calcining the dried solid at a temperature not exceeding 450 ° C to obtain the catalyst precursor material.
• (4) A process for producing methanol, comprising the step of contacting a gas mixture comprising hydrogen, carbon monoxide and carbon dioxide with the above-described catalyst material.

DESCRIPTION OF THE FIGURES

shows an HRTEM image of the catalyst material obtained in Example 2.

shows an HRTEM image of the catalyst material obtained in Comparative Example 2.

refers to a schematic representation of the microstructure of the catalyst materials according to Example 2 and Comparative Example 2.

Figure 4 shows the TGA curve obtained in a thermal analysis of the uncalcined catalyst precursor material described in Example 1.

shows the pore distribution of the calcined catalyst precursor according to Example 1 and Comparative Example 1.

Fig. 11 shows the X-ray diffraction pattern of the calcined catalyst precursor materials according to Example 1 and Comparative Example 1.

Figure 4 shows the TPR (temperature-programmed reduction) curves of the calcined catalyst precursor materials of Example 1 and Comparative Example 1.

shows the EDX (electron dispersive X-ray) analysis of the local composition of the catalyst materials of Example 2 and Comparative Example 2.

Figure 4 shows the Pawley refinement of the X-ray diffraction patterns of the reduced catalyst materials according to Example 2 and Comparative Example 2.

and show HRTEM images of the calcined catalyst precursor material obtained in Example 1.

DETAILED DESCRIPTION OF THE INVENTION

In the following, the use of "comprising" includes also more restrictive embodiments in which "comprising" is replaced by "consisting essentially of" or "consisting of". Further, hereafter, the explicit disclosure of a broader range of quantitative values (eg, a-d), together with an enclosed (preferred) narrower range (eg, b-c), also discloses the two possible sub-ranges that are within the overall range on one the sides of the narrower area. Thus, within this broader range of quantitative values (eg, a-d), further embodiments are characterized by all regions (eg, a-b, a-c, b-d, or c-d) which combine each of these upper bound or lower bound of this explicitly defined wider quantitative range may be formed with the lower bound or the upper bound of any explicitly defined and included (preferred) narrower region.

Unless otherwise indicated, molar contents and ratios of metal atoms refer to the total composition, which can be determined by techniques such as X-ray fluorescence (XRF).

Catalyst precursor material

In the first aspect, the present invention relates to a Cu / Zn / Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum, wherein copper and zinc are present together in a molar amount greater than aluminum, and wherein the standard deviation of the local molar Al content, as determined by EDX, is not more than 50%.

Accordingly, the carbonates and oxides form a more homogeneous phase than is present in the prior art catalyst precursor materials. The results available to the inventors indicate that this homogeneity of the catalyst precursor material is maintained when the catalyst precursor material is reduced in the presence of hydrogen to form crystalline copper particles. In addition, without wishing to be bound by theory, it is believed that the phase structure of the precursor material has a direct effect on the lattice constant of the resulting copper particles, as described in more detail below. A shift in this lattice constant away from that of bulk copper (3.610 Å) is observed in the present invention and considered beneficial for catalyst activity.

Thus, according to an alternative description, the present invention relates to a Cu / Zn / Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum, wherein copper and zinc are present together in a molar amount greater than aluminum, and
wherein the reduction of said precursor material in the presence of hydrogen results in a catalyst material in which discrete crystalline Cu particles are partially embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al, the crystalline Cu particles having a lattice constant of 3.615 Å or more, preferably 3.615 to 3.621 Å.

Although it is assumed that the conditions adopted for the reduction do not affect the lattice constant, the reduction referred to in the above embodiment is preferably carried out under the following conditions:
Heating 50 mg catalyst precursor material in a fixed bed reactor in an atmosphere consisting of 5 vol.% Hydrogen and 95 vol.% Helium (flow rate 80 ml / min.) To a temperature of 250 ° C. The heating rate is 2 K / min., And the material is kept at 250 ° C for 30 minutes. Atmospheric pressure is used. The reaction can be monitored using a thermal conductivity detector.

The molar Cu / Zn ratio can be selected according to known catalysts. For example, it is in the range of 0.2 / 1 to 5.5 / 1 or 0.4 / 1 to 4.0 / 1. It is believed that Cu / Zn molar ratios of less than 2.8 / 1 exert a positive influence on the formation of small crystalline Cu particles in the reduced and activated form of the catalyst precursor material. More preferably, Cu / Zn ratios are from 1/1 to 2.75 / 1, 1.5 / 1 to 2.7 / 1 or 2/1 to 2.7 / 1 (e.g., 2.2 / 1 to 2.6 / 1). Copper and zinc interact synergistically in the final catalyst material.

On the other hand, aluminum, especially in the form of alumina, is considered to be a heat stabilizer for the Cu crystallites, preventing their sintering. The content of aluminum is preferably 1 to 30 mol%, more preferably 5 to 25 mol%, especially 10 to 20 mol%, based on all metal components.

According to another preferred embodiment, the molar ratio Cu / Zn is 0.5 / 1 to less than 2.8 / 1 (with the above more preferred ranges) and the Al content is 1 to 30 mol%, based on all metal constituents.

It is considered preferable that the claimed catalyst precursor material, and therefore also the resulting catalyst material, comprises copper, zinc and aluminum as the sole metal constituents. However, aluminum may be partially replaced by at least one other metal capable of forming heat stable oxides such as cerium, lanthanum, zirconium, titanium, chromium, manganese or magnesium. Calcium and gallium can be used to partially replace Zn. The total content of the replacing metal atom (s) is preferably not more than 15 mol%, more preferably not more than 10 mol%, and more preferably not more than 5 mol%, based on all metal components.

The claimed catalyst precursor material preferably differs from known catalyst precursors by the homogeneity of its structure and the carbonate content. It is believed that these features, among others, contribute to the formation of the highly active and stable hydrogen reduction catalyst materials to form discrete Cu particles as catalytically active centers.

• 1) die Standardabweichung des lokalen molaren Al-Gehalts nicht mehr als 50%, stärker bevorzugt nicht mehr als 40%, bevorzugter nicht mehr als 30%, bevorzugter nicht mehr als 20%, z. B. 5 bis 15%, beträgt und/oder
• 2) die Standardabweichung des lokalen molaren Zn-Gehalts nicht mehr als 40%, stärker bevorzugt nicht mehr als 30% bevorzugter nicht mehr als 20%, bevorzugter nicht mehr als 15%, z. B. 4 bis 12% beträgt, und/oder
• 3) die Standardabweichung des lokalen molaren Cu-Gehalts nicht mehr als 25%, bevorzugt nicht mehr als 20%, bevorzugter nicht mehr als 15%, bevorzugter nicht mehr als 10%, z. B. 1 bis 7%, beträgt;

jeweils basierend auf dem durchschnittlichen lokalen molaren Gehalt von Al, Zn oder Cu, wie er durch EDX unter den Bedingungen, die im Experimentalteil beschrieben sind, bestimmt wird.The homogeneous nature of the catalyst precursor material can be described by relatively small variations in local composition as measured by electron-dispersive X-ray analysis (EDX) under the conditions described below and in the Experimental section. As the comparison provided in the examples will show, it is preferred in accordance with the present invention that

• 1) the standard deviation of the molar local Al content is not more than 50%, more preferably not more than 40%, more preferably not more than 30%, more preferably not more than 20%, e.g. B. 5 to 15%, is and / or
• 2) the standard deviation of the local molar Zn content is not more than 40%, more preferably not more than 30%, more preferably not more than 20%, more preferably not more than 15%, e.g. B. 4 to 12%, and / or
• 3) the standard deviation of the molar local Cu content is not more than 25%, preferably not more than 20%, more preferably not more than 15%, more preferably not more than 10%, e.g. From 1 to 7%;

each based on the average local molar content of Al, Zn or Cu as determined by EDX under the conditions described in the Experimental section.

Condition 1 is particularly suitable for characterizing the preferred embodiments of the present invention and for distinguishing them from the comparative example explained in the Experimental section. However, to describe the homogeneous nature of the catalyst precursor material and the final catalyst material, each of these three conditions may be used alone or in combination with one or two other conditions to describe other embodiments of the present invention.

The above-mentioned "local molar content" is to be understood as the molar content of the corresponding metal atom in a "local composition".

By "local composition" we mean the chemical composition of the catalyst (precursor) material (in terms of molar contents of aluminum, zinc and copper), as determined by EDX under the conditions given in the Experimental section for a projected area of the sample forming a circle with a Diameter of 500 nm in the TEM image, determined.

In order to determine the standard deviation of the local molar contents, the sample holder (grid plate with holey carrier film, eg a holey amorphous carbon film) is covered with a sufficient amount of catalyst (precursor) material powder to ensure that there are a sufficient number of sample areas. below which 100 circles (diameter = 500 nm) can be randomly selected for analysis of the local composition. If sample preparation without the use of organic solvents as a dispersing agent, adherence of dry powder particles of the catalyst (precursor) material to the surface of the dry carrier film does not result in a sufficient number of areas for the analysis of 100 local compositions, one can, for example prepare a second or further samples in the same way (without solvent). Alternative sample preparation techniques may also be used as long as they do not adversely affect the chemical composition of the sample, for example sample preparation by immersing the carrier in a dispersion of particles of catalyst (precursor) material in a suitable dispersing agent (organic solvent), if necessary in the absence of oxygen (to avoid the oxidation of active copper particles) using an inert gas, followed by evaporation of the organic solvent. This "wet" preparation technique usually results in larger amounts of catalyst (precursor) material per unit area of carrier film.

These aforementioned 100 circles should not overlap and be distributed as evenly as possible over the entire grid plate. If possible, it is preferable to select local compositions that are as far as possible from the meshes of the grid plate to minimize background signals resulting from the grid material. Whenever possible, it is also preferable to select local compositions that are near the holes of the carrier film or that are partially above a hole. In these cases, the background signal from the carrier film material (eg, carbon signal) in the EDX is weaker. Then the illuminated area of the TEM spectrometer is focused to 100 individual measurements of the local compositions defined by these circles. The results are averaged and the standard deviation calculated.

It should be added that local compositions, as defined above, adequately characterize local variations in the total sample since EDX measurements show a considerable depth of penetration (preferably at least 500 nm). In addition, it is believed that the range that can be analyzed by EDX is representative of the metal variation in the overall sample.

The homogeneous nature of the catalyst precursor material described above does not preclude a lower degree of crystallinity, as explained below.

In a preferred embodiment, the claimed catalyst precursor material exhibits a very low degree of crystallinity and is preferably X-ray amorphous under standard X-ray diffraction conditions, preferably those described in the experimental section of the present application. The term "X-ray amorphous" must be understood as the absence of "well defined diffraction peaks". The term "well defined diffraction peak" must be understood as referring to a diffraction signal and a FWHM (full width at half maximum), d. H. the width of the peak at 50% of its height above the baseline, of at most 3 ° in 2 theta (2θ).

Catalyst precursor materials having a low degree of crystallinity exhibit less than 20%, preferably less than 10%, more preferably less than 5% of crystalline regions as can be observed in HRTEM images obtained under the conditions carried out in the experimental section. Crystalline regions (typically small ZnO or CuO phases) show characteristic lattice patterns in the HRTEM. The catalyst precursor material (A) of Example 1 which was analyzed by HRTEM as in For example, as shown in FIG. 1, it has a very small crystalline CuO region having a diameter of the order of 10 nm. As in To see another HRTEM image of the calcined catalyst precursor material (A), the analyzed sample also contained a very small crystalline ZnO region that is identifiable by its lattice pattern.

The projected area of these crystalline regions can be determined, for example, manually, and related to the total projected area of the catalyst material observed in the HRTEM.

According to an alternative definition, low crystalline materials are characterized by the absence of crystalline regions having a diameter of more than 20 nm, more preferably by the absence of crystalline regions having a diameter of more than 15 nm in HRTEM images disclosed in U.S. Pat were obtained in the experimental part of measurement conditions.

The preferred low crystallinity or X-ray amorphous nature of the claimed catalyst precursor material also indicates that discrete crystalline ZnO and Al ₂ O ₃ particles or spinel phases or crystallites are preferably absent therein.

According to one embodiment of the claimed catalyst precursor material, the carbonate content, expressed as CO ₂ and measured by TGA under the conditions specified in the experimental section, is 5% by weight or more, preferably 10% by weight or more. Usually, the carbonate content does not exceed 30% by weight. According to further embodiments, the carbonate content is in the range of 12 to 25 wt .-%, z. From 13 to 19% by weight, expressed as CO ₂ . These carbonate contents can be adjusted using suitable amounts of carbonates as starting materials, in combination with a calcination temperature not exceeding 450 ° C, as further explained below.

The catalyst precursor material of the invention preferably has a BET surface area, as measured with nitrogen at 77K, of 90m ² / g or more, more preferably 100m ² / g or more, even more preferably 110m ² / g or more. The upper limit of the BET surface area is not particularly limited, but is 250 m ² / g, for example.

• • machen Poren mit Radien von 1 bis 10 nm 45 bis 90%, bevorzugt 55 bis 80% der Gesamtporosität aus und
• • machen Poren mit Radien von mehr als 10 und bis zu 100 nm 55 bis 10%, bevorzugter 45 bis 20% der Gesamtporosität aus.

Preferably, the claimed catalyst precursor material comprises pores having radii of 2 to 3 nm. These pores preferably make 20 to 40%, e.g. B. 25 to 35% of the total porosity. According to a preferred pore size distribution determined using the BJH method and from desorption data as described in the experimental section,

• Make pores with radii of 1 to 10 nm 45 to 90%, preferably 55 to 80% of the total porosity and
• Make pores with radii greater than 10 and up to 100 nm 55 to 10%, more preferably 45 to 20% of the total porosity.

Pores with radii greater than 100 nm are preferably absent. This preferred pore size distribution suggests that in the claimed catalyst precursor material, as well as in the resulting catalyst material, the homogeneous oxide / carbonate phase itself may be porous, in contrast to known catalysts where pores exist only or mainly between discrete ZnO and Al ₂ O ₃ Particles are present.

Without wishing to be bound by these theoretical considerations, it is believed that the claimed catalyst precursor material has strong interactions between the nanoscale copper oxide or copper carbonate domains and the surrounding oxide / carbonate phase. This follows from the TPR (Temperature Programmed Reduction) analysis of the precursor material, as in with the maximum reduction rate being observed at higher temperatures than a comparative material. According to one embodiment, the Cu / Zn / Al catalyst precursor material is accordingly characterized by a maximum reduction rate (TPR) at a temperature of 180 ° C or more, e.g. B. 184-190 ° C, characterized. The TPR analysis is performed under the conditions outlined in the Experimental section.

Cu / Zn / Al catalyst material

The present invention also relates to a Cu / Zn / Al catalyst material comprising discrete crystalline Cu particles partially embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al,
wherein in the catalyst material Cu and Zn are present together in a larger molar amount than aluminum, and
wherein the lattice constant of the crystalline Cu particles is 3.615 Å or more, preferably 3.615 to 3.621 Å.

The continuous phase comprising oxides and carbonates of at least Zn and Al is also referred to hereinafter as the "Zn / Al continuous phase" because it is depleted in copper as compared to the oxide / carbonate phase of the catalyst precursor material. This depletion does not rule out that Cu is still present in the continuous phase.

This catalyst material is preferably obtained by the reduction of the catalyst precursor material described above. Accordingly, unless stated otherwise, features and preferred features that characterize embodiments of the catalyst precursor material can also be used to describe the resulting catalyst material.

This is applicable, for example, to the molar contents and ratios of the metal components. Thus, in accordance with a preferred embodiment of the catalyst material, the molar ratio of Cu and Zn is 0.5 / 1 to less than 2.8 / 1 and the Al content is 1 to 30 mole%, based on all metal constituents. Scientific results available to the inventors indicate that the pore size distribution also remains unchanged or substantially unchanged.

The foregoing description of the homogeneity of the catalyst precursor material, which relies on the low standard deviation of local compositions, is also fully transferable to the catalyst material. In the present invention, this homogeneity is achieved without any milling steps.

On the other hand, the carbonate content can be lowered by the activation treatment and is, for example, 1 to 25% by weight, e.g. 2 to 22 wt .-%, 3 to 19 wt .-%, 4 to 16 wt .-% or 5 to 12 wt .-%, in each case as CO ₂ .

In the claimed catalyst material, the partially embedded crystalline Cu particles constitute the active sites of the catalyst. They are formed during the reduction step because copper, as the noblest metal, is first reduced and has a propensity to separate from the oxide / carbonate phase in the form of discrete particles. These particles preferably have an approximately spherical or oval shape. In the present invention, it is preferred that at least 60%, more preferably at least 75%, even more preferably at least 90% of all Cu particles of the claimed catalyst material have a diameter in the range of 3 to 11 nm, preferably 5 to 9 nm.

The diameter of the individual Cu particles can be determined by measuring the projected area of individual particles in TEM images (TEM analysis as described in the Experimental section), and calculating the equivalent diameter corresponding to the diameter of a circle with the same area. In order to obtain a reliable result with low standard deviation, the total number of particles measured was 5000. The average particle diameter (volume weighted), which is preferably also within the above nm ranges, can be determined in the same way.

The term "partially embedded," as used in connection with the claimed catalyst material, means that the surfaces on distinct Cu particles do not completely match the surface continuous Zn / Al phase are covered. It goes without saying that the surface on the copper particles must be accessible to the reactant gas mixture in order to develop its catalytic activity.

This property of the claimed catalyst material can also be expressed by the copper surface (S _Cu ). It is preferred that the claimed catalyst material S _{Cu exhibit} values of at least 10 m ² / g, more preferably at least 15 m ² / g, even more preferably at least 20 m ² / g. For example, the S _cu value of 24.8 m ² / g measured for the catalyst material of Example 2 shows that approximately two-thirds of the catalyst surface is in contact with the surrounding continuous Al / Zn phase. In general, higher S _Cu values reflecting a lower degree of copper surface coverage are preferred. However, the inventors surprisingly found that the accessible Cu particle surface is not the only factor affecting catalytic activity. Without wishing to be bound by mechanistic considerations, it appears that the homogeneous nature (and preferred low crystallinity) as well as the carbonate content of the surrounding Al / Zn phase have a particularly beneficial effect on the remaining exposed portion of the Cu Surface. In order to achieve high catalytic efficiency, it is preferred that the Cu particles be in a nonequilibrium form, which is reflected in an increased Cu lattice constant (the equilibrium lattice constant of bulk copper is 3.610 Å). According to the present invention, the Cu lattice constant of the partially embedded Cu particles is preferably 3.615 Å or more. Preferred embodiments relate to lattice constants in the range of 3.615 to 3.621 Å, 3.616 to 3.620 Å, and 3.617 to 3.619 Å.

According to a preferred embodiment of the claimed catalyst material, the continuous Zn / Al phase exhibits a low degree of crystallinity or is preferably X-ray amorphous. In the sense explained above, "X-ray amorphous" must be understood as free from well-defined diffraction peaks.

Continuous Zn / Al phases exhibiting a low degree of crystallinity exhibit X-ray diffraction patterns that are free of well-defined diffraction peaks except for weak reflections, such as in which can be attributed to the presence of ZnO particles (ICDD 36-1451). Since a low degree of crystallinity is characterized by the absence of well-defined diffraction peaks and therefore difficult to quantify with conventional diffraction peak terminology, we define it in the context of the claimed catalyst precursor material in the following way: the net area of the diffraction signal in the range 30.0 to 39.0 ° in 2 theta (region of the 100, 002, 101 reflections of ZnO) should be less than 20%, preferably less than 15% of the net area of the diffraction signal in the range 39.0 to 47.0 ° in 2 theta (region 111 reflection of Cu). "Net area" shall be understood as the area defined by the measured diffraction signal curve and the linear background in the predetermined angular range. "Linear background" shall be understood as a straight line between the measured intensity at the lower limit of the predetermined angular range and the measured intensity at the upper limit of the predetermined angular range. For catalyst materials B (Comparative Example 1) and A (Example 1), ZnO net areas of 31.5% and 12.6%, respectively, were measured.

The preferred low crystallinity or X-ray amorphous nature of the continuous Zn / Al phase also implies that discrete crystalline ZnO and Al ₂ O ₃ particles or spinel phases or crystallites are preferably absent therein.

CATALYST ACCELERATOR AND CATALYST

The catalyst material of the invention can be used as a catalyst after the activation treatment, that is, as a powder. According to a preferred embodiment, shaped catalyst precursor bodies of defined size, e.g. Tablets, formed from the catalyst precursor material, followed by reduction in the presence of hydrogen under the conditions explained below. This reduction can be achieved, for example, by contacting the precursor bodies with syngas, pure hydrogen or hydrogen gas diluted with inert gas.

It is preferred to add a lubricant, for example graphite, in small amounts, for example 1 to 5 wt.%, Based on the final weight of the catalyst (or catalyst precursor). There is no particular limitation on the size of the catalyst (precursor) bodies to be used. However, the following structural properties are preferred.

The macroscopic size (average largest diameter) of the individual catalyst (precursor) body is preferably in the range of 0.5 to 20 mm, z. B. 1 to 10 mm. Catalyst bodies of this size can be obtained by methods known in the art, for example by pressing a dried one calcined catalyst precursor material, rebreathing the pressed material, and performing size-selective steps, such as sieving, prior to performing the activation (reduction) step. Instead of pressing, an extrudate can be formed.

In another embodiment, the catalyst precursor material is coated onto a support prior to the reduction step according to art-known techniques. This coating of a support with the corresponding catalyst precursor materials may as well be carried out at an earlier stage, for example before the calcination treatment.

The support, which is preferably inert, may have any shape and surface structure. However, regularly shaped, mechanically stable bodies such as ball, ring, tube cut, half ring, saddle, coil or honeycomb carrier bodies or carriers provided with channels, such as fiber mats or ceramic foams, are preferred. The size and shape of the carrier bodies is determined, for example, by the dimensions, primarily the inner diameter of the reaction tubes, if the catalyst is used in tubular or tube bundle reactors. The diameter of the carrier body should then be between 1/2 and 1/10 of the inner diameter of the reactor. In the case of liquid bed reactors, the support dimensions are determined, for example, by the flow dynamics in the reactor. Suitable materials are, for example, soapstone, duranite, stoneware, porcelain, silicon dioxide, silicates, aluminum oxide, aluminates, silicon carbide or mixtures of these substances. The proportion of the layer of the catalyst precursor material applied to the support is preferably 1 to 30% by weight, more preferably 2 to 20% by weight, based on the total mass of the finally supported catalyst material. The thickness of the catalyst material layer is preferably 5 to 300 μm, more preferably 5 to 10 μm.

PREPARATION OF THE CATALYST PREPARATION MATERIAL AND ACTIVATION BY REDUCTION

• (a) Zubereiten einer ersten wässrigen Lösung, enthaltend mindestens ein wasserlösliches Kupfersalz und mindestens ein wasserlösliches Zinksalz,
• (b) Zubereiten einer zweiten Lösung, enthaltend mindestens ein wasserlösliches basisches Aluminiumsalz (wie Natriumaluminat) und mindestens ein alkalisches carbonathaltiges Fällmittel (wie Natriumcarbonat),
• (c) Mischen der ersten und der zweiten Lösung, wobei ein unlöslicher Feststoff gebildet wird,
• (d) Gewinnen des unlöslichen Feststoffs,
• (e) Trocknen des gewonnenen Feststoffs, sowie
• (f) Kalzinieren des getrockneten Feststoffs bei einer Temperatur, die 450°C nicht überschreitet, um das Katalysatorvorläufermaterial zu erhalten.

The claimed catalyst precursor material is preferably prepared in a process comprising the following steps.

• (a) preparing a first aqueous solution containing at least one water-soluble copper salt and at least one water-soluble zinc salt,
• (b) preparing a second solution containing at least one water-soluble basic aluminum salt (such as sodium aluminate) and at least one alkaline carbonated precipitant (such as sodium carbonate),
• (c) mixing the first and second solutions to form an insoluble solid,
• (d) recovering the insoluble solid,
• (e) drying the recovered solid, as well
• (f) calcining the dried solid at a temperature not exceeding 450 ° C to obtain the catalyst precursor material.

It is preferred to carry out at least one washing step between steps (d) and (e) and / or steps (e) and (f). When the dried solid recovered in step (e) is subjected to a washing step, it is preferred to re-dry the washed solid before it undergoes the final calcination step.

The inventors have found that this process is particularly suitable for preparing a catalyst precursor material that can be converted to high performance catalyst materials in a subsequent reduction step.

The first and second solutions described above may be mixed in any manner and in any order. Thus, the first solution can be added to the second solution, or the second solution can be added to the first solution, or a mixture of the two solutions can be obtained by mixing the two solutions simultaneously, as by adding the two solutions simultaneously into a vessel , It is desirable that the mixing of the first and second solutions in step (c) be at a pH above about 5.5 (e.g., pH 5.5 to 9), and more generally above about 6.0, e.g. At a pH of 6.0 to 7.0. When the two solutions are mixed at the same time, the pH of the resulting mixture can be controlled by changing the rate of addition of the second solution containing an alkaline material. As the rate of addition of the second solution increases, the pH of the resulting mixture increases.

The water-soluble copper and zinc salts used to form the first solution are copper and zinc salts, e.g. Nitrates, acetates, sulfates, chlorides, etc. However, it is presently preferred to use the nitrates of copper and zinc in the formation of the first solution. Any water-soluble aluminum salt may be used to prepare the second solution, and the aluminum salt is generally a basic aluminum salt, such as e.g. For example, sodium aluminate. Alumina gels may also be used, however, according to a preferred embodiment of the invention, the Al oxide present in the Zn / Al continuous phase is not derived from an aluminum hydroxide sol or gel nor from colloidally dispersed Al ₂ O ₃ .

The second solution also contains at least one alkaline carbonate-containing water-soluble material, such as. For example, sodium carbonate or ammonium carbonate. The carbonate-containing salt may be used in combination with other water-soluble salts, such as sodium hydroxide or ammonium hydroxide. The amount of alkaline material present in the second solution may be varied over a wide range, and the amount of alkaline materials should be sufficient to provide an alkaline solution which, when added to the first solution, is mixed with leads to the desired pH. The pH of the mixture obtained by mixing the first and second solutions should be within the range of 5.5 to 9.0 and is preferably at least 6 and most preferably at least about 6.0 to 7.0. As noted above, the pH of the mixture can be adjusted as desired by adjusting the relative rates of addition of the two solutions. In addition, the mixture obtained from the first and second solutions is preferably maintained at a temperature of about 50 to 80 ° C (but preferably not for extended periods of time to suppress the aging processes described below). A precipitate is formed and recovered by techniques known in the art, such as filtration, centrifugation, etc. The recovered precipitate is preferably washed with water to remove impurities, dried by heating to a temperature of up to about 250 ° C, and finally calcined. The washing is carried out, for example, to reduce the content of alkali metals, preferably to values of 0.2 wt% or less, more preferably 0.1 wt% or less.

The drying temperature used depends on the conditions selected. In batch processes, it is usually sufficient to dry by heating to a temperature of about 150 ° C or less, for example, 80 to 120 ° C. In a preferred embodiment of the present invention, the drying is carried out by continuous spray drying. During spray-drying, the insoluble solid obtained is exposed to temperatures in the range preferably from 80 to 220 ° C. The spray dryer typically operates with at least two temperature zones within this range, which preferably include an inlet temperature that is higher than the outlet temperature. Spray drying can be carried out, for example, at an inlet temperature of 180 to 220 ° C and an outlet temperature of 80 to 120 ° C. The spray-drying is preferably carried out continuously.

The inventors have found that it is preferable to suppress aging processes in the preparation of the catalyst (precursor) material. For this reason, it is considered advantageous to carry out steps (c), (d) and (e) in a continuous process. This can be achieved by continuous and simultaneous metering of the first and second solution in step (c) into the reaction vessel. While the second and the first solutions are mixed in this way, the insoluble solid is continuously recovered and placed in a spray-drying apparatus, whereby the recovered solid is dried continuously.

When the granules obtained by spray-drying are subjected to a washing step, a second spray-drying step may follow.

This continuous process ensures that little time passes between the first formation of an insoluble solid in step (c) and the recovery of the insoluble solid (from the mother liquor) in step (d). In this way, aging processes can be suppressed and the formation of a very homogeneous and preferably low-crystalline or amorphous continuous Al / Zn phase promoted. According to a preferred embodiment, the time span between the formation of the insoluble solid in step (c) and in the recovery (step (d)) is shorter than one hour, preferably shorter than 50 minutes, more preferably shorter than 40 minutes, for example shorter than 30 minutes , for example, 20 minutes or less. Aging processes can be detected by color changes of the insoluble solid in contact with the mother liquor.

The calcination (step f) is preferably carried out in an oxygen-containing atmosphere at a temperature of 200 to 400 ° C, preferably 280 to 380 ° C, more preferably 310 to 350 ° C.

For convenience, this calcination reaction is normally carried out at atmospheric pressure. In principle, however, it is also possible to perform this step at elevated or reduced pressure, for example within the range of atmospheric pressure ± 50% or ± 20%. As the oxygen-containing atmosphere, air or a synthetic oxygen-containing atmosphere may be used. Depending on the other process conditions, oxygen is not normally used in levels greater than 50% by volume. Suitable oxygen volume fractions are for example 1 to 40 vol.%, 5 to 35 vol.% Or 10 to 30 vol.%. The rest is nitrogen, as in air, or any inert gas such as Ar or He.

The calcined catalyst precursor material obtained in step (f) can be activated by reduction in the presence of hydrogen. This reduction will be accomplished by contacting the calcined catalyst material with a hydrogen-containing atmosphere, such as synthesis gas, pure hydrogen, or hydrogen diluted with an inert gas (eg, nitrogen, helium, or argon). In this reduction step, the deposition of crystalline Cu particles from the surrounding oxide / carbonate phase produces a catalyst material as claimed. This reduction step is carried out under conditions known in the art, preferably at a temperature of 150 to 300 ° C, more preferably 175 to 270 ° C and preferably at atmospheric pressure, although in principle the same pressures (up to 150 bar) as in the synthesis of synthesis gas (see below description ) could be used.

In one embodiment, the reduction is effected by heating the catalyst precursor material in an atmosphere comprising from 1 to 10% by volume of hydrogen, preferably from 2 to 7% by volume of hydrogen, the remainder being an inert gas such as nitrogen, argon or helium from 230 to 260 ° C. The heating rate is preferably 1 to 5 K / min, and the precursor material is held at the final temperature for at least 15 minutes, for example, 30 minutes or more.

According to a second embodiment, the precursor material is heated to 150 to 200 ° C at a rate of 0.5 to 5 K / min. in a gas mixture comprising 1 to 5% by volume of hydrogen, the remainder being inert gas such as nitrogen or helium, followed by reduction in 100% hydrogen at a higher temperature of preferably 220 to 260 ° C. In both reduction steps, the precursor material is preferably maintained at the final temperature for a period of at least 15 minutes, for example 30 minutes or more.

METHANOL FOR THE PREPARATION OF METHANOL

The catalyst of the invention (and therefore also the catalyst material included therein) can be used under conventional conditions to produce methanol from synthesis gas, which is a technical mixture of hydrogen, carbon monoxide and carbon dioxide.

According to one embodiment, the synthesis gas comprises, for example
CO 3 to 20 vol.%, Preferably 5 to 15 vol.%,
CO ₂ 1 to 12 vol.%, Preferably 2 to 8 vol.%,
optionally an inert gas such as N ₂ or helium in an amount of
From 1 to 30% by volume, preferably from 2 to 15% by volume,
CH ₄ 0 to 30 vol.%, Z. B. less than 20 vol.%,
and the remainder H ₂ .

The reaction is preferably carried out at a pressure of 10 to 150 bar, preferably 20 to 70 bar, more preferably 35 to 55 bar (in each case absolute pressure values), and at a temperature of preferably 200 to 300 ° C on the catalyst (material) of the present invention ,

The space velocity may be about 1000 to 50,000, for example 5,000 to 30,000 liters of synthesis gas mixture per hour and 1 catalyst.

EXPERIMENTAL:

chemicals

The following high purity gases were used: He (99.9999%), H ₂ (99.9999%), N ₂ O / He (1% N ₂ O, 99.9995%).

The following starting materials were used to prepare the catalyst materials:
Cu (NO ₃ ) ₂ × 3H ₂ O, Carl Roth,> = 99% pa
Na ₂ O ₃ , Carl Roth,> = 99.8% pa
ZnO, Carl Roth,> = 99% pa
Sodium aluminate, technical grade, Fisher Scientific.

Thermogravimetric analysis-emission gas analysis (TGA-EGA)

The hydroxycarbonate precursor TG curves were recorded on a Netzsch STA 449-C thermobalance with a connected quadrupole mass spectrometer for EGA (Pfeiffer Omnistar). A heating rate of 2 K / min. was applied in synthetic air.

Temperature-controlled reduction (TPR)

The TPR was achieved by raising the temperature to 250 ° C in a fixed bed reactor (CE instruments TPDRO 1100) at a heating rate of 2 K / min. carried out. H ₂ consumption was monitored using a thermal conductivity detector.

TPR studies were carried out with 50 mg of calcined catalyst precursor material (powder) at 5% hydrogen and 95% helium atmosphere at a flow rate of 80 ml / min. carried out.

Pore size and pore size distribution:

The nitrogen adsorption-desorption isotherm is measured at 77K using, for example, an Autosorb-1 instrument (Quantachrome). Before adsorption, the sample is degassed in vacuo at 353 K for 4 hours. The pore size distribution calculation is made using the desorption branch of the isotherm and the Barrett-Joyner-Halenda (BJH) method, as in EP Barrett, LG Joyner, PP Halenda, J. Amer. Chem. Soc. 73 (1951) 373 described, performed. Complete adsorption / desorption isotherms in the p / p ₀ range of 0.001 to 1 were recorded. The Quantachrome AUTOSORB software was used to calculate the pore size distribution based on the complete desorption branch of the isotherm and the Barrett-Joyner-Halenda (BJH) method. The sample size is about 0.1 g.

Copper surface S _Cu

The copper surface was analyzed using N ₂ O-reactive frontal chromatography with 1 vol.% N ₂ O in helium according to the method described by Chinchen et al. ( GC Chinchen, CM Hay, HD Vanderwell, KC Waugh, J. Catal. 1987, 103, 79 ) proposed at slightly more moderate reaction conditions ( O. Hinrichsen, T. Genger, M. Muhler, Chem. Eng. Technol. 2000, 11, 956-959 ) certainly.

X-ray diffraction

For X-ray diffraction (XRD), the calcined samples of the catalyst material were measured in situ on a Stoe theta-theta diffractometer equipped with an Anton Paar XRK 900 reaction chamber, a secondary graphite monochromator, and a scintillation counter using Cu Kα. Radiation reduced. For the reduction, the temperature was linearly increased to 250 ° C in an atmosphere of 5% by volume H ₂ in He (100 ml / min., 2 K / min.) And isothermally maintained for 2 hours. The reduced samples were cooled to room temperature in the reducing gas prior to taking the X-ray diffraction pattern (30 to 100 ° 2 theta, 0.02 ° increments, 16 sec count / step). The TOPAS software package ( AA Coelho, Topas, General Profile and Structure Analysis Software for Powder Diffraction Data, Version 3.0, Bruker AXS GmbH, Karlsruhe, Germany, 2006 ) was used for the refinements of the X-ray diffraction data.

X-ray diffraction patterns of the catalyst precursor material samples were collected on a Stoe Stadi-p diffractometer equipped with a primary focusing Ge monochromator and a linear position sensitive detector (resolution 0.005 ° / channel, 0.1 ° step size) in the 2 theta range 4 to 80 ° recorded with a counting time of 10 s using Cu Kα radiation in transmission geometry.

For the determination of the Cu lattice constant, X-ray diffraction patterns in the angular range 38 to 100 ° 2 theta were implemented using the Pawley method (implemented in TOPAS) and a single Gaussian peak for the ZnO 102 reflection at a fixed position of 47.698 ° 2 theta refined. The peak profile for the Cu reflections was a Lorentz profile with 1 / cos (theta) dependence of the fwhm (full width at Half maximum, full width at half maximum). In addition to the lattice parameter, a sample displacement parameter, but no zero shift, was refined. The background was modeled using a second-order Chebyshev polynomial.

TEM and EDX

A Philips CM200FEG microscope operated at 200 kV and equipped with an EDX spectrometer (T-TEM CM-200F 147-5, available from EDAX, Inc.) was used for the TEM studies. The coefficient of spherical deviation was C _S = 1.35 mm. The information boundary was better than 0.18 nm, which allowed the major phases to be identified in HRTEM (High Resolution Transmission Electron Microscopy) images. High-resolution images with a pixel size of 0.016 nm were recorded at a magnification of 1083000 x with a CCD camera. EDAX software (Genesis 5.21) was used for EDX raw data analysis. For the transformation of signal intensities to concentrations, the theoretical k factors implemented in Genesis 5.21 were used. Reduced samples were transferred to the microscope in inert gas. Ni lattices covered with a 5 nm thick holey amorphous carbon layer were used for sample preparation. No liquids were used during sample preparation.

The EDX spectra were recorded with samples inclined at 30 ± 0.5 ° and the TEM images without inclination.

When taking the EDX spectra of the local compositions exposed to 500 nm diameter circles, the beam intensity was adjusted so that the signal registered by the detector always had approximately the same integral intensity. Furthermore, exactly the same exposure time was used. In this way the counting statistics were completely comparable for all spectra obtained.

Comparative Example 1 (calcined catalyst precursor material B)

Sample B was prepared in a similar way as in DE 101 60 486 A1 in an automated laboratory reactor (Mettler-Toledo Labmax) by constant pH precipitation at pH 6.5 and T = 65 ° C from a 1 M aqueous solution of Cu, Zn and Al nitrates (Cu: Zn: Al = 60:25:15) and 1.6 M Na ₂ CO ₃ solution. The precipitate was aged in the mother liquor for 3 hours. During aging, the color changed from light blue to green, indicating the formation of zinc malachite or rosasite and hydrotalcite-like phases. The sample was washed thoroughly with water, dried and calcined in static air (3 hours, 330 ° C, 2 K / min.).

Before calcination, the sample was subjected to X-ray diffraction analysis. It consisted of a mixture of a slightly crystalline zinc malachite or rosasite (Cu, Zn) ₂ (CO ₃ ) (OH) ₂ (ICDD 41-1390, malachite) and a hydrotalcite-like phase (Cu, Zn) _1-x Al _x (OH) ₂ (CO ₃ ) _{x / 2} x mH ₂ O (ICDD 37-629, where x = 0.25 and m = 4) and possibly other X-ray amorphous phases.

The N ₂ adsorption / desorption isotherm of calcined precursor B (Comparative Example 1) exhibited hysteresis indicating capillary condensation in the pores. The surface area was determined to be 88 m ² / g.

The pore size distribution of the calcined sample was determined using the BJH method and desorption data and is described in US Pat shown ("Catalyst B"). Only one type of pore, which showed a maximum around 20 nm, was observed and assigned to interparticle pores. These results suggest that pores are only present between the nanostructured but non-porous oxide particles.

The calcined sample was also subjected to a TPR analysis, which corresponds to the in results shown for "Catalyst B". The maximum of the TPR curve was 179 ° C. The results are discussed in connection with "Catalyst A" (Example 1).

Comparative Example 2 (Catalyst B)

The calcined precursor material of Comparative Example 1 was dissolved in 5% H ₂ (heated to 250 ° C at 2 K / min followed by 0.5 hour at 250 ° C, flow rate 80 ml / min) in a fixed bed reactor (TPDRO 1100, CE instruments) to obtain a catalyst material which exhibits activity in the synthesis of methanol from synthesis gas.

The HRTEM analysis of the reduced catalyst material showed that it consisted essentially of three different phase types with decreasing frequency, ie (i) the in (ii) relatively large particles with small buried Cu grains and (iii) large disordered needles with an Al content of more than 90 atom%.

In phase (i) it was observed that Cu particles with an average diameter <10 nm were separated by small ZnO particles, which prevented their sintering and formed a porous frame around individual particles. These regions of the catalyst were frequently observed and exhibited Cu-rich compositions near the nominal metal ratio.

The characteristic Al-rich compositions of 20 to 30 atomic% found for phase (ii) and the sometimes observed hexagonal shape of these particles suggest that they were formed from a hydrotalcite-like precursor phase.

Phase (iii) probably evolved from an amorphous aluminum hydroxide precursor phase which was not detected by X-ray diffraction.

The inhomogeneity of the comparative catalyst material is also demonstrated in an EDX analysis of the local composition, as in shown, observed. Catalyst B (□) shows a significant scatter compared to Catalyst A (■) (= Example 2 as described below). The blue grid lines mark the nominal composition.

The accessible copper surface S _Cu was determined to be 36.1 ± 1 m ² / g by N ₂ O chemisorption.

The Cu lattice constant was determined to be 3.6138 ± 0.0008 Å by X-ray diffraction, which is close to that of bulk copper.

Example 1 (calcined catalyst precursor material A)

The continuously prepared precursor A was precipitated from a Cu, Zn nitrate solution ("first solution", 0.85 M) having the same Cu: Zn ratio as in Sample B (Comparative Example 1). The "first solution" was prepared by dissolving 87.0 g of Cu (NO ₃ ) ₂ .3H ₂ O in 200 ml of water followed by adding 50 ml of concentrated nitric acid (65%). After adding 12.2 g of ZnO, water was added until the volume of the slurry reached 600 ml. The slurry was stirred at 60 ° C until a clear solution was obtained.

The "second solution" was prepared using 600 ml of a 1.6 M Na ₂ CO ₃ solution as precipitant to which 9.8 g of aluminate (Na ₂ Al ₂ O ₄ .3H ₂ O) solution was added with stirring has been.

An automatic laboratory reactor (Labmax, Mettler-Toledo) was filled with 400 ml of water and preheated to 65 ° C. Over a period of 45 minutes, 600 ml of the above copper-zinc nitrate solution was added while the above aluminum carbonate solution was added simultaneously at a rate which had a pH of the resulting mixture of the first and second solutions between 6.0 and 7, 0 resulted.

The resulting slurry of the insoluble solid that formed during mixing was continuously in a spray dryer (T _inlet = 200 ° C, T _outlet = 100 ° C) after an estimated residence time of 16 min. Charged in the reactor. The pumping rate was such (about 35 ml / min.) That the fill level in the reactor did not change.

The granules obtained at the outlet of the spray dryer were repeatedly slurried in water for 5 min. stirred and filtered until the conductivity of the filtrate was less than 0.5 mS / cm (usually after the fifth repetition).

After the last filtration step, the solid, wet filter residue was slurried in about 1 liter of water and spray dried under the same conditions as above.

The dried material is calcined in static air (3 hours, 330 ° C, 2 K / min.).

The X-ray diffraction study before calcination showed that unlike the material of Comparative Example 1, the uncalcined material was completely X-ray amorphous and showed only weak and broad modulations of the background.

The uncalcined material was also subjected to a thermogravimetric analysis, as in shown, which revealed the following. Up to about 300 ° C, the uncalcined catalyst material decomposed in a poorly defined dehydroxylation step with almost linear mass loss, essentially due to H ₂ O emission. Before a temperature around 463 ° C, only a slight CO ₂ emission is observed, and therefore, most of the carbonate will withstand the calcining treatment at a temperature of 330 ° C. The decarboxylation step contributes 13% to the total mass loss of 30.5% at 600 ° C (CO ₂ content of the claimed sample about 15.8%).

The X-ray diffraction patterns of the calcined material showed only broad and weak reflections at the positions where the peaks of CuO (ICDD 80-76) are expected. Characteristic peaks for Zn or Al compounds could not be observed. The continuous Zn / Al phase, in which the CuO particles are partially embedded, can therefore be regarded as X-ray amorphous.

The N ₂ adsorption / desorption isotherms of the calcined intermediates of Catalyst A (Example 1) were also Type V indicating the presence of mesopores. The surface area was determined to be 114 m ² / g.

The pore size distribution of the calcined sample was determined using the BJH method and desorption data and is shown in FIG shown ("Catalyst A"). A maximum around 20 nm is observed and attributed to the interparticle pores, but at a relatively low frequency compared to a second pore type with radii of 2-3 nm. These small pores contribute significantly to the surface, suggesting that in catalyst A the oxide matrix itself could be porous.

The calcined sample was also subjected to a TPR analysis, which includes the in for "Catalyst A". The maximum of the TPR curve was 187 ° C. The shoulders of the TPR profile of Catalyst B (Comparative Example 1) on the high and low temperature sides are more pronounced compared to Catalyst A, confirming the lower degree of homogeneity. The maximum rate of reduction is observed at Catalyst A at a significantly higher temperature, suggesting stronger metal oxide interactions consistent with the previously described microstructure model.

Example 2 (catalyst material A)

The catalyst precursor material of Example 1 was reduced in the same manner as described in Comparative Example 2.

The catalyst structure was analyzed by HRTEM analysis as described in shown, examined. The microstructure of the catalyst material recovered in Example 2 was very homogeneous, and no different types of material were observed by TEM. The Cu particles were almost spherical ( ). Unlike catalyst B (Comparative Example 2), single separated oxide particles are hardly observed, and consequently, the porous Cu / ZnO particle assembly is not present in the new material. The Cu particles are partially embedded in the oxide matrix, resulting in an arrangement that resembles a supported system with close interfacial contact between the metal particles and adjacent Cu-depleted oxide. For both samples, a statistically significant Cu particle size distribution was determined by measuring the projected areas in TEM images of 16308 and 9930 particles for Catalyst A and B, respectively. For both samples, approximately 90% of the particles fall within a size range of 4 to 9 nm, with the average diameter (volume weighted) being 8.1 ± 2.4 nm (7.2 ± 2.2 nm for Catalyst B). In view of the similarities of Cu particle size and shape, it is believed that differences in activity between this Example (A) and Comparative Example 2 (B) are due to the microstructure of the ZnO / Al ₂ O ₃ ingredient and its interfacial contact with Cu particles in relationship. The microstructural differences are shown schematically in illustrated.

The homogeneity of the catalyst material was confirmed in an EDX analysis of the local compositions, as in (see Catalyst A (■)).

The average composition ("nominal composition") of the catalyst material, as determined by X-ray fluorescence, was Cu / Zn / Al = 0.6 / 0.25 / 0.15. Essentially the same Composition (Cu / Zn / Al = 60.6 / 25.8 / 13.6) was obtained by averaging 16 local compositions, which were determined as described below. The average composition is in indicated by the crossing point of the two grid lines.

The local compounds used in were determined on 16 clusters of primary catalyst particles which had a total projected area of more than 500 nm x 500 nm. The local metal contents and local compositions were therefore analyzed by a slightly different route than previously described and defined. It is assumed that this difference has no influence on the determination of the homogeneity of the samples.

• 1) Die Standardabweichung des lokalen molaren Al-Gehalts vom Durchschnittswert (13,6) betrug ungefähr 1,5, das sind ungefähr 11%.
• 2) Die Standardabweichung des lokalen molaren Zn-Gehalts vom Durchschnittswert (25,8) betrug ungefähr 2,2, das sind ungefähr 8,4%.
• 3) Die Standardabweichung des molaren Cu-Gehalts vom Durchschnittswert (60,6) betrug ungefähr 2,5, das sind ungefähr 4,1%.

It can be seen that unlike the catalyst material of Example 2, the local Cu, Zn, and Al contents hardly deviated from the average composition.

• 1) The standard deviation of the local molar Al content from the average value (13.6) was about 1.5, that is about 11%.
• 2) The standard deviation of the local molar Zn content from the average value (25.8) was about 2.2, that is about 8.4%.
• 3) The standard deviation of the molar Cu content from the average value (60.6) was about 2.5, that is about 4.1%.

The corresponding standard deviation calculated from 13 local compositions of the catalyst material according to Comparative Example 2 was substantially larger, that is more than 100% for the local Al content, about 28% for the local Cu content and about 14% for the local Zn content.

The accessible copper surface S _Cu was determined to be 24.8 ± 1.2 m ² / g by N ₂ O chemisorption.

The X-ray diffraction data further confirmed that the Cu particles were in a non-equilibrium state, which is reflected by an increased Cu lattice constant. It was calculated by fitting the X-ray diffraction data to 3.618 ± 0.001Å ( ) certainly. This value is far from the value for massive copper (3.610 Å). It can be speculated that the copper lattice is disturbed by enhanced metal / oxide interactions, such as epitaxial pressure at the interface, or by partial dissolution of zinc or oxygen in the Cu lattice across the interface resulting in high intrinsic activity.

Example 3 (production of methanol)

The catalytic test was carried out in a flow-up structure similar to that of O. Hinrichsen, T. Genger, M. Muhler, Chem. Eng. Technol. 2000, 11, 956-959 described. For a fast running analysis, a calibrated quadrupole mass spectrometer (Pfeiffer Vacuum, Thermostar) was used.

A glass-lined stainless steel reactor was filled with 100 mg of catalyst (sieve fraction 250 to 355 μm). The catalyst precursor materials A (Example 2) and B (Comparative Example 2) were reduced as follows: (i) by heating in a gas mixture of 2.0% H ₂ / He to 175 ° C (at 1 K / min ^-1 ), followed by holding the material at 175 ° C for 15 hours and (ii) subsequently heating in 100% H ₂ to 240 ° C (at 1 K / min ^-1 ) followed by holding the material at 240 ° C for 30 min.

The "initial activity" of the catalyst under equilibrium conditions was determined at 220 ° C and 10 bar pressure, using a flow rate of 50 N ml min ^-1. A mixture of 72% H ₂ , 10% CO, 4% CO ₂ and 14% He was used as the methanol synthesis feed gas (purity 99.9995%). Helium was added to simulate the N ₂ content of syngas. To examine the catalysts for methanol synthesis activity, they were exposed to the feed gas and at 10 K / min. heated to the standard reaction temperature (220 ° C) at which the "initial activity" was measured.

Subsequently, the catalyst in the feed gas was cooled at atmospheric pressure. The catalyst was heated to 513 K (240 ° C) in the feed gas (at atmospheric pressure) overnight at a very low heating rate (0.5 K / min, ie, quasi-stationary). At 240 ° C and atmospheric pressure, the methanol production is determined by the thermodynamic equilibrium so that the theoretical concentration can be calculated and compared with the measured value. In this way, the calibration of the MS can be checked again. This relatively high temperature overnight process (compared to the standard test temperature of 220 ° C) aims to simulate catalyst deactivation over extended periods of use under standard conditions. The residence time in the feed stream at 240 ° C was 8.5 hours. The next day, the temperature was lowered to 220 ° C and the activity measured again at 10 bar and 220 ° C at the same feed and flow rate as on day 1. Measurements on this second day are referred to as "end activity". In these tests, Catalyst A (Example 2) showed higher initial and final activity than Catalyst B (Comparative Example 2), as shown in Table 1 below. Table 1 initial activity lineout "Stability" Catalyst A 13.1 12.6 mmol / gh 96.2% Catalyst B 11.56 10.82 mmol / gh 93.6%

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• GB 1010871 [0002]
• GB 1159035 [0002]
• GB 1296211 [0002]
• EP 0125689 A2 [0003]
• US 4353071 [0003]
• DE 10160486 A1 [0004, 0103]
• US 4598061 [0005]
• US 4279781 [0006]
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Cited non-patent literature

• Waller et al. Faraday Discuss. Chem. Soc. 1989, 87, 107 [0002]
• EP Barrett, LG Joyner, PP Halenda, J. Amer. Chem. Soc. 73 (1951) 373 [0095]
• GC Chinchen, CM Hay, HD Vanderwell, KC Waugh, J. Catal. 1987, 103, 79 [0096]
• O. Hinrichsen, T. Genger, M. Muhler, Chem. Eng. Technol. 2000, 11, 956-959 [0096]
• AA Coelho, Topas, General Profile and Structure Analysis Software for Powder Diffraction Data, Version 3.0, Bruker AXS GmbH, Karlsruhe, Germany, 2006 [0097]
• O. Hinrichsen, T. Genger, M. Muhler, Chem. Eng. Technol. 2000, 11, 956-959 [0138]

Claims (17)

Cu / Zn / Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum, wherein copper and zinc are present together in a molar amount greater than aluminum, and wherein the standard deviation of the local molar Al content, such as by EDX measured, not more than 50%. A Cu / Zn / Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum, wherein copper and zinc are present together in a molar amount greater than aluminum, and wherein reduction of said precursor material in the presence of hydrogen results in a catalyst material in which discrete crystalline Cu particles are partially embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al, wherein the crystalline Cu particles have a lattice constant of 3.615 Å or more, preferably 3.615 to 3.621 Å. Cu / Zn / Al catalyst precursor material according to claim 1 or 2, wherein the molar ratio of Cu and Zn is 0.5 / 1 to less than 2.8 / 1, preferably 2/1 to 2.7 / 1, and the Al content is 1 to 30 mol%, preferably 10 to 20 mol%, based on all metal constituents. A Cu / Zn / Al catalyst precursor material according to claim 1, 2 or 3, wherein the standard deviation of the molar Zn local content, as measured by EDX, is not more than 40% and / or the standard deviation of the molar local Cu content, as measured by EDX, is not more than 25%. A Cu / Zn / Al catalyst precursor material according to claim 1, 2, 3 or 4, wherein the degree of crystallinity as measured by HRTEM is less than 10%. A Cu / Zn / Al catalyst precursor according to any one of claims 1, 2, 3, 4 or 5, wherein the carbonate content, expressed as CO ₂ and measured by TGA, is 5% by weight or more, preferably 10% by weight. -% or more. A Cu / Zn / Al catalyst precursor material according to any one of claims 1, 2, 3, 4, 5 or 6 which satisfies at least one of the following two conditions: (i) the BET surface area as measured at 77 K with N ₂ 90 m ² / g or more, preferably 100 or more, more preferably 110 m ² / g or more, and (ii) it has pores having a size distribution measured with BJH, wherein pores having radii of 1 to 10 nm 45 to 90% of the total porosity and pores with radii of more than 10 and up to 100 nm account for 55 to 10% of the total porosity. A Cu / Zn / Al catalyst precursor according to claim 1, which has a maximum reduction rate (TPR) at a temperature of 180 ° C or higher, preferably at 184-190 ° C. Cu / Zn / Al catalyst material comprising discrete crystalline Cu particles partially embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al, wherein in the catalyst material Cu and Zn are present together in a larger molar amount than aluminum and preferably the molar ratio of Cu and Zn is 0.5 / 1 to less than 2.8 / 1 and the Al content is 1 to 30 mol%, based on all metal components, is, and wherein the lattice constant of the crystalline Cu particles is 3.615 Å or more, preferably 3.615 to 3.621 Å, and the catalyst material is preferably obtained by reducing the catalyst precursor material according to any one of claims 1, 2, 3, 4, 5, 6, 7 or 8 in the presence of Hydrogen is available. Cu / Zn / Al catalyst material according to claim 9, wherein at least 75% of all Cu particles have a diameter in the range of 3 to 11 nm, preferably 5 to 9 nm. Cu / Zn / Al catalyst material according to claim 9 or 10, wherein at least one of the following conditions is satisfied: (1) the standard deviation of the molar local Al content as measured by EDX is not more than 50%, (2) the standard deviation of the local molar Zn content as measured by EDX is not more than 40%, (3) The standard deviation of the local molar Cu content as measured by EDX is not more than 25%. A process for producing a catalyst precursor material according to any one of claims 1, 2, 3, 4, 5, 6, 7 or 8, comprising the steps of (a) preparing a first aqueous solution containing at least one water-soluble copper salt and at least one water-soluble zinc salt (b Preparing a second solution containing at least one water-soluble basic aluminum salt and at least one alkaline carbonated precipitant; (c) mixing the first and second solutions to form an insoluble solid, (d) recovering the insoluble solid, (e) drying the and (f) calcining the dried solid at a temperature not exceeding 450 ° C to obtain the catalyst precursor material. Process according to claim 12, wherein the drying is carried out by continuous spray-drying, preferably at a temperature of 80 ° C to 220 ° C. A method according to claim 12 or 13, wherein steps (c), (d) and (e) are carried out in a continuous process. A method according to claim 12, 13 or 14, wherein the time interval between the formation of the insoluble solid in step (c) and the recovery of the insoluble solid in step (d) is shorter than 60 minutes, preferably shorter than 30 minutes. Catalyst comprising the catalyst material according to one of claims 9, 10 or 11. A process for producing methanol comprising the step of contacting a gas mixture comprising hydrogen, carbon monoxide and carbon dioxide with the catalyst of claim 16.

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