WO2013072197A1

WO2013072197A1 - Methanol synthesis catalyst on the basis of copper, zinc and aluminum

Info

Publication number: WO2013072197A1
Application number: PCT/EP2012/071581
Authority: WO
Inventors: Malte Behrens; Benjamin KNIEP; Patrick KURR; Robert SCHLÖGL; Martin Hieke
Original assignee: Süd-Chemie Ip Gmbh & Co. Kg
Priority date: 2011-11-16
Filing date: 2012-10-31
Publication date: 2013-05-23
Also published as: EP2780110A1; JP2015502248A; CN104039444A; DE102011086451A1; RU2014123678A; IN2014KN00985A

Abstract

The present invention relates to a catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminium, wherein Cu and En are present together in a greater molar amount than aluminum and said carbonates and oxides form a homogeneous phase, as well as the catalyst material resulting from the reduction of this precursor. The catalyst material comprises discrete crystalline Cu particles partly embedded in a continuous homogeneous phase comprising oxides and carbonates of at least Zn and Al wherein in said catalyst material Cu and Zn are present together in a greater 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 ¾ by mol, based on all metal constituents. The invention also pertains to a specific method of making this catalyst. The catalyst shows an excellent performance and stability in the synthesis of methanol from synthesis gas.

Description

METHANOL SYNTHESIS CATALYST

ON THE BASIS OF COPPER, ZINC AND ALUMINUM

The present invention relates to a catalyst containing

catalytically active copper particles embedded in a zinc- and luminum-containing phase as well as its use in the

manufacture of methanol from synthesis gas ,

BACKGROUND OF THE INVENTION

The worldwide demand for methanol, being a major basic chemical, is more than 30 million tons per year and its importance is forecasted to increase further in the future. Industrially it is produced from synthesis gas, a mixture of hydrogen {¾) , carbon monoxide (CO) and carbon dioxide (C0₂) , typically at 35 to 55 bar and 200 to 300°C. Since the early pioneer studies of workers at ICI reflected by GB 1 010 871, GB 1 159 035 and GB 1 296 211, Cu/ZnO/Al₂0₃ catalysts are almost exclusively used in this industrial reaction. These catalysts are typically prepared in a multi-step synthesis (D . Waller et al . Faraday Discuss . Chem. Soc . 1989 , 87, 107) . Co-precipi ation of mixed aqueous Cu- , Zn- and Al-nitrate solutions using soda as precipitating agent is performed at a constant pH close to 7 followed by an aging period to produce a mixed CuZnAl hydroxy carbonate precursor which is calcined to an intimate mixture of the oxides . Finally, CuO existing 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 Sud-Chemie AG discloses catalysts of this type characterised by a specific pore size distribution. This document also teaches that the copper/zinc mol ratio is preferably 2.8 to 3.8.

According to DE 101 60 486 Al (Sud-Chemie AG) Cu/Zn molar ratios of less than 2.8 are essential in achieving relatively small and catalytically particularly active copper crystallite sizes. This document also teaches that the aluminum oxide component is obtained at least in part from an aluminum hydroxide sol .

Similar catalysts containing aluminium oxide derived from a colloidally dispersed aluminium hydroxide sol or gel and containing about 13 to 130 x 10^"6 g atoms of alkali metal per gram of metallic oxide precursor mixture are the subject of US 4 , 598 , 061 being also in the name of Sud-Chemie AG. The catalyst disclosed in this document is also characterized by a pore size distribution wherein pores having a diameter of 7.5 to 14 nm constitute about 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 ratio,

expressed as metal by weight, of 2:1 to 3.5:1, The catalyst includes, preferably, a thermal stabilizing metal oxide such as aluminum oxide in minor proportions and is prepared by co- precipi ation of all three constituents from a single

solution O'f soluble zinc, copper and aluminum salts, say the nitrates, or by the decomposition of copper amine carbonates and zinc amine carbonates onto a thermally stabilizing metal oxide in the hydrated state, or as a gel. Both preparation techniques are expected to lead to an inhomogeneous

composition of the ZnO/Al2C>3 phase surrounding the particles .

US 3,850,850 and US 3,923,694 (both ICI) relate to spinel- containing Cu/Zn/Al catalysts with relatively high Cu

contents. The catalyst of US 3,923,694 seems to be free of carbonate as its precursor characterized as comprising 10 to 80% copper with the balance essentially being the crystalline spinel structure. The catalyst of US 3,850,850, on the other hand, seems to have an inhomogeneous structure as it is taught in the two examples that only 67% and 75.3%,

respectively, of the possible spinell content is reached. EP 0 522 669 A2 in the name of Engelhard Corporation

discloses hydrogenation catalysts comprising the oxides of copper, zinc and aluminum. These catalysts are taught to be useful in the hydrogenation of aldehydes, ketones, carboxylic acids and carboxylic esters. The examples evaluate the hydrogenation activity of the catalyst in the hydrogenation of coconut metal ester. The Cu/Zn ratio of these catalysts varies to a great extent. Unlike the above catalysts, the hydrogenation catalyst of EP 0 522 66.9 A2 is prepared 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 whereby an

insoluble solid is formed, d) recovering the insoluble solid, and e) calcining the recovered solid.

The recovered precipitate is calcined at a temperature in the range of from about 475 ° C to about 700 ° C for periods of about 30 to about 120 minutes. Under these conditions, metal carbonate still existing in the insoluble solid recovered in step d) is converted to oxide under release of carbon

dioxide . The complete removal of carbonate at these high temperatures is also expected to enhance the crystallinity of the catalyst material . It is one object of the present invention to provide a new catalyst (material) that is useful in the industrial

manufacture of methanol from synthesis gas. One further object of the present invention is to provide a new methanol synthesis catalyst (material) showing an excellent catalytic activity and stability.

It is one further object of the present invention to provide a catalyst precursor (material) that can be reduced in

hydrogen to the above high performance catalyst material .

One further object of the present invention resides in providing a preparation method for the catalyst precursor material, the catalyst material and the corresponding catalys .

Further objects become apparent from the following detailed description of the present invention.

SUMMARY OF THE PRESENT INVENTION

The main embodiments of the present invention can be

summarized as follows;

( la) 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 greater molar amount than aluminum, and

wherein the standard deviation of the local molar Al content, as measured by EDX, is not more than 50% .

(lb) 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 greater molar amount than aluminum, and wherein the reduction of this precursor material in the presence of hydrogen leads to a catalyst material, in which discrete crystalline Cu particles are partly embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al, said crystalline Cu particles having a lattice constant of 3,615 A or more, preferably 3.615 to 3.621 A.

(2) A Cu/Zn/Al catalyst material comprising discrete

crystalline Cu particles partly embedded in a

continuous phase comprising oxides and carbonates of at least Zn and Al

wherein in said catalyst material Cu and Zn are present together in a greater 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 5 to 30 ¾^■ by mol, based on all metal constituents, and

wherein the lattice constant of the crystalline Cu particles is 3.615 A or more, preferably 3.615 to

3.621 A. This catalyst material is preferably obtained by reducing the above catalyst precursor material in the presence of hydrogen .

(3) A process for the manufacture of 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 sal ,

(b) preparing a second solution containing at least one water-soluble basic aluminium salt (such as sodium aluminate) and at least one alkaline

carbonate-containing precipitating agent {such as sodium carbonate) ,

(c) mixing the first and second solutions whereby an insoluble solid is formed,

(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 the manufacture of 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

Figure 1 shows a HRTEM picture of the catalyst material obtained in example 2.

Figure 2 shows a HRTEM picture of the catalyst material obtained in reference example 2.

Figure 3 relates to a schematic illustration of the

microstructure of the catalyst materials according to example 2 and reference example 2, respectively .

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

Figure 5 shows the pore distribution of the calcined catalyst precursors according to exam le 1 and reference example 1.

Figure 6 shows the XRD pattern of the calcined catalyst precursor materials according to example 1 and reference example 1.

Figure 7 shows the TPR (temperature programmed reduction) curves of the calcined catalyst precursor materials of example 1 and reference example 1. Figure 8 shows the EDX (electron dispersive X-ray} analysis of local compositions in the catalyst materials of example 2 and reference example 2.

Figure 9 shows the Pawley refinement of XRD patterns of the reduced catalyst materials according to example 2 and

reference exam le 2.

Figures 10 and 11 show HRTEM pictures of the calcined

catalyst precursor material obtained in example 1.

DETAILED DESCRIPTION OF THE INVENTION

In the following the use of "comprising" also includes more restricting embodiments where "comprising" is replaced by "essentially consisting of" or "consisting". Further, hereinafter the explicit disclosure of a broader quantitative range of values (e.g. a-d) together with an included

(preferred) narrower range (e.g. b-c) also discloses the two possible part-ranges lying within the overall range on either side of the narrower range. Hence, within this broader quantitative range of values (e.g. a-d) further embodiments are characterized by all ranges (e.g. a-b₍ a-c, b-d or c-d) which can be formed b combining any of the upper limit or the lower limit of this explicitly defined broader

quantitative range with the lower limit or the upper limit of any explicitly defined and included (preferred) narrower range .

If not stated otherwise, molar contents and ratios of metal atoms refer to the average bulk composition, as can be

determined with 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 greater molar amount than aluminum, and wherein the standard deviation of the local molar Al content, as measured by EDX, is not more than 50%,

Accordingly, said carbonates and oxides form a more

homogeneous phase than exists in prior art catalyst precursor materials. The results available to the inventors indicate that this homogeneity of the precursor catalyst material is preserved when the catalyst precursor material is reduced in the presence of hydrogen under formation of crystalline copper particles. Moreover, without wishing to be bound, by theory, it is considered that the phase structure of the precursor material exerts a direct impact on the lattice constant of the resulting copper particles as explained below in. further detail . A shift of this lattice constant away from that of bulk copper (3.610 A) is observed in the present invention and considered as beneficial for catalyst activity.

According to an alternative description, the present

invention thus 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 greater molar amount than aluminum, and

wherein the reduction of this precursor material in the presence of hydrogen leads to a catalyst material , in which discrete crystalline Cu particles are partly embedded in a continuous phase comprising oxides and carbonates of at least En and Al. , said Cu particles having a lattice constant, of the crystalline Cu particles of 3.615 A or more, preferably 3.615 to 3,621 A. Although it is believed that the conditions chosen for the reduction do not influence the lattice constant, the

reduction referred to in the above embodiment is preferably conducted under the following conditions:

heating 50 mg of 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 held at 250°C for 30 min . Atmospheric pressure is used. The reaction can be monitored using a thermal conductivity detector.

The molar Cu/Zn ratio can be chosen in accordance with known catalysts. It ranges for instance from 0.2/1 to 5.5/1, or 0.4/1 to 4.0/1. It is believed that molar Cu/Zn 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 this catalyst precursor material. Stronger preferred are Cu/Zn ratios of 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.

Aluminum, in particular in form of aluminum oxide, on the other hand, is regarded as thermal stabiliser for the Cu crystallites preventing them from sintering. The aluminum content is preferably 1 to 30% by mol, more preferably 5 to 25 % by mol , in particular 10 to 20 % by mol, based on all metal constituents.

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

It is considered as preferred that the claimed catalyst precursor material, and thus also the resulting catalyst material, comprises copper, zinc and aluminum, as the only metal constituents, However, aluminum may be partially

replaced by at least one other metal capable of forming

thermally stabilizing oxides such as cerium, lanthanum, zirconium, titanium, chromium, manganese or magnesium.

Calcium and gallium may be used to replace Zn in part. The total content of the substituting metal atom (s) is preferably not more than 15 mol % , more preferably not more than 10 mol% and even more preferably not more than 5 mol% based on all metal constituents .

The claimed catalyst precursor material is preferably

distinguished from known catalyst precursors by the

homogeneity of its structure and the content of carbonate. It is considered that among others these features contribute to the formation of very active and stable catalyst materials after hydrogen reduction to form discrete Cu particles as catalytically active centers .

The homogenous nature of the catalyst precursor material can be described by relatively small variations in the 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 local molar 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. 5 to 15%, and/or

2) the standard deviation of the local molar En 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. 4 to 12% , and/or 3) the standard deviation of the local molar Cu content is not more than 25%, more preferably not more than 20%, more preferably not more than 15% , more preferably not more than 10%, e.g. 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 suited to characterise the preferred embodiments of the present invention and to

distinguish the same from the Reference Example explained in the experimental section. To describe the homogenous nature of the catalyst precursor material and the final catalyst material, each of these three conditions may, however, be used by its own or in combination with one or two further conditions to describe further embodiments of the present invention.

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

As "local composition" we understand the chemical composition of the catalyst (precursor) material (in terms of molar contents of aluminum, zinc and cupper) as determined by EDX under the conditions specified in the experimental section for a projected area of the sample that corresponds to a circle having a diameter of 500 ran in the TEM image .

To determine the standard deviation of local molar contents , the sample holder (grid plate with a holey carrier film, for instance a holey amorphous carbon film) is covered with a sufficient amount of catalyst (precursor) material powder to ensure that a sufficient number of sample areas exist from which one hundred circles (0=500 nm) can be arbitrarily selected for analysis of the local composition. If the sample preparation without the use of organic solvents as dispersing agents, by adhering dry powder particles of the catalyst (precursor) material to the surface of the dry carrier film, does not lead to a sufficient number of areas for analysis of 100 local compositions, one may for instance prepare a second or further samples in the same manner {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 instance a sample preparation by dipping the carrier into a dispersion of particles of the catalyst (precursor) material in a suitable dispersion agent {organic solvent) , if necessary in the absence of oxygen (to prevent the oxidation of active cupper particles) under use of an inert gas , followed by evaporating the organic solvent. This "wet" preparation technique typically leads to greater amounts of catalyst (precursor) material per unit area of the carrier film.

These aforementioned 100 circles should not overlap and be spread over the entire grid plate as evenly as possible. If possible, it is preferable to select local compositions which are located as far as possible from the meshes of the grid plate to minimize background signals resulting from the grid material. If possible, it is also preferable to select local compositions that are located close to the holes of the

carrier film or that are partly located above one hole. In these cases, the background signal from the carrier film material (for instance carbon signal) in EDX is weaker, Then., the illuminated area of the TEM spectrometer is focused in 100 individual measurements on the local compositions defined by these circles. The results are averaged and the standard deviation is calculated therefrom,

It should be added that local compositions as defined above sufficiently characterize local variations in the bulk of the sample since EDX measurements show a considerable penetration depth (preferably at least 500 nm) . Moreover, the region analyzable by EDX is believed to be representative for the metal variation throughout the bulk of the entire sample.

The above-described homogenous nature of the catalyst precursor material does not exclude a low degree of

crystallinity as explained below.

According to one preferred embodiment, the claimed catalyst precursor material shows a very low degree of crystallinity and is preferably X-ray amorphous under standard XRD

conditions, preferably those described in the experimental section of the present application. The term "X-ray

amorphous" is to be understood as absence of "well-defined diffraction peaks" . The term "well-defined diffraction peak" is to be understood as relating to a diffraction signal and an FWHM {full width at half maximum), i.e.. the width of the peak at 50% of its height above the base line, of at most 3° in 2 theta (2Θ) .

Catalyst precursor materials with a low degree of

crystallinity display less than 20%, preferably less than 10%, more preferably less than 5% of crystalline regions as can be observed in BRTEM pictures obtained under the

conditions specified in the experimental section . Crystalline regions ( ypically small ZnO or CuO phases) show

characteristic grid patterns in HRTEM . The catalyst precursor material (A) of example 1, which was analyzed by means of HRTEM as shown i Fig . 10, includes e.g. a very small

crystalline CuO region having a diameter in the order of lOnm . As seen from Fig . 11, another HRTM picture of the calcined catalyst precursor material (A) , the sample analyzed also contained a very small crystalline ZnO region

identifiable via its grid pattern.

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

According to an alternative definition, low crystalline materials are characterized by the absence of crystalline areas that have a diameter of more than 20 nm, more

preferably by the absence of crystalline areas that have a diameter of more than 15 nm in HRTEM pictures obtained under the measuring conditions specified in the experimental section.

The preferred low crystallinity or X-ray amorphous nature of the claimed catalyst precursor material also indicates that discrete crystalline ZnO and AI2O3 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 C0₂ and

measured by TGA under the conditions specified in the

experimental section, is 5 wt.-% or more, preferably 10 wt . - % or more. Typically, the carbonate content does not exceed 30 wt,~%. According to further embodiments, the carbonate content ranges from 12 to 25 wt . - % , e.g. from 13 to 19 wt . - % , expressed as CO2 · These carbonate contents can be adjusted using appropriate amounts of carbonates as starting materials in combination with a calcination temperature that does not exceed 450 °C as explained further below.

The catalyst precursor material of the invention preferably has a BET surface, as measured with nitrogen at 77 K, of 90 m²/g or more, more preferably 100 m²/g or more, even more preferably 110 m²/g or more. The upper limit of the BET surface area is not specifically limited, but is for instance 250 m²/g.

Preferably, the claimed catalyst precursor material comprises pores with radii of 2 to 3 nm. These pores preferably account for 20 to 40%, e.g. 25 to 35% of the total porosity.

According to one preferred pore size distribution, which was determined using the BJH method and desorption data, as described in the experimental section,

• pores having radii of i to 10 nm account for 45 to 90 % , more preferably 55 to 80% of the total porosity and

• pores having radii of more than 10 and up to 100 nm

account for 55 to 10 %, more preferably 45 to 20% of the total porosity.

Pores with radii above 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 might be porous in contrast to known catalysts where pores are only or primarily present between discrete ZnO and AI2O3 particles .

Without wishing to be bound by these theoretical

considerations , it is believed that strong interactions occur in the claimed catalyst precursor material between the nano- size copper oxide or copper carbonate domains and the

surrounding oxide/carbonate phase . This follows from TPR (temperature programmed reduction) analysis of the precursor material , as shown in Fig. 7, wherein the maximum rate of reduction was observed at higher temperatures than for a reference material . According to one embodiment the claimed Cu/Zn/Al catalyst precursor material is accordingly

characterised by a maximum rate of reduction (TPR) at a temperature of 180 °C or more, for instance 184 to 190°C . TPR analysis is conducted under the conditions specified 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 partly embedded in. a continuous phase comprising oxides and

carbonates of at least Zn and Al

wherein in said catalyst material Cu and Zn are present together in a greater molar amount than aluminum and

wherein the lattice constant of the crystalline Cu particles is 3,615 A or more, preferably 3.615 to 3.621 A.

The continuous phase comprising oxides and carbonates of at least Zn and Al is in the following also referred to as

"continuous Zn/Al phase" as it is depleted of Cu when

compared with the oxide/carbonate phase of the catalyst

precursor material. This depletion does not exclude that Cu is still present in the continuous phase.

This catalyst material is preferably obtained by reducing the above -described catalyst precursor material. Accordingly, if not stated otherwise, features and preferred features

characterizing embodiments of the precursor catalyst material can also be used to describe the resulting catalyst material .

This applies for instance to the molar contents and ratios of the metal constituents. Thus, in accordance with one

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 % by mol based on all metal constituents. Scientific results available to the present inventors

indicate that the pore size distribution also remains

unchanged or essentially unchanged.

The previous description of the homogeneity of the catalyst precursor material based 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 grinding steps.

The carbonate content, on the other hand, may be lowered during the activation treatment and is for instance 1-25 wt,%, e.g. 2-22 wt.%, 3-19 wt.%, 4-16 wt . % or 5-12 wt.%, each expressed as C0₂.

In the claimed catalyst material the partly embedded

crystalline Cu particles constitute the active catalyst sites . They are formed during the reduction step since copper as the most noble metal is reduced first and tends to

segregate form 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 3-11 ran, preferably 5-9 nm .

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

The term "partly embedded" as used in connection with the claimed catalyst material means that the surfaces of

discernible Cu particles are not fully covered with the

continuous Zn/Al phase . It goes without saying that the surface of the copper particles must be accessible to the reactant gas mixture to develop its catalytic activity. This property of the claimed catalyst material can also be expressed via the copper surface area (S^) , It is preferred that the claimed catalyst material displays SQ_U values of at least 10 m²/g, more preferably at least 15 m²/g, even more preferably at least 20 m²/g . The SQ_U value of 24.8 m²/g measured for the catalyst material of example 2 indicates for instance that about two thirds of the catalyst surface are in contact with the surrounding continuous Al/Zn phase .

Generally, higher SQ_U values reflecting a lower degree of Cu surface coverage are preferred. However_., the present

inventors have surprisingly found that the accessible Cu particle surface is not the only factor influencing catalytic activity. Without wishing to be bound by mechanistical considerations , it would appear that the homogenous nature (and the preferred low crystallinity) as well as the

carbonate content of the surrounding Al/Zn phase seems to exert a very beneficial effect on the remaining exposed fraction of the Cu surface . To achieve high catalytic

performance, it is preferred that the Cu particles are present in a non-equilibrium form reflected by an enlarged Cu lattice constant {the equilibrium lattice constant of bulk copper is 3.610 A). According to the present invention, the Cu lattice constant of the partly embedded Cu particles is preferably 3.615 A or more . Preferred embodiments relate to lattice constants ranging from 3.615 to 3.621 A, 3.616 to 3.620 A, and 3.617 to 3.619 A.

According to one preferred embodiment of the claimed catalyst material , the continuous Zn/Al phase shows a low degree of crystallinity or is preferably X-ray amorphous . "X-ray amorphous" is to be understood in the above-explained sense as free of well-defined diff action peaks .

Continuous Zn/Al phases showing a low degree of crystallinity display XRD patterns free of well-defined diffraction peaks except for weak reflections , as shown for instance in Fig. 9, that can be assigned to the presence of ZnO particles (XCDD 36-1451} . Since a low degree of crystallinity is

characterized by the absence of well defined diffraction peaks and thus difficult to quantify using 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- 39.0° 2theta (region of 100, 002, 101 reflections of ZnO) should be lower than 20%, preferably lower than 15% of the net area of the diffraction signal in the range 39.0-47.0° 2theta (region of 111 reflection of Cu) . "Net area" is to be understood as the area defined by the measured diffraction signal curve and the linear background in the given angular range. "Linear background" is to be understood as a straight line between the measured intensity at the lower limit of the given angular range and the measured intensity at the upper limit of the given angular range. For catalyst materials B {Reference 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 indicates that discrete crystalline ZnO and AI2O3 particles or spinel phases or crystallites are preferably absent therein.

Catalyst precursor and catalyst

The catalyst material of the invention, can be used as

catalyst as obtained after the activation treatment, that is as powder. According to one preferred embodiment, shaped catalyst precursor bodies of a definite size, e.g. tablets, are 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 instance by contacting the precursor bodies with synthesis gas , pure hydrogen or hydrogen gas diluted with inert gas . It is preferred to add a lubricant, for instance graphite, in small amounts, for instance 1 to 5 wt . -%, based on the final weight of the catalyst (precursor) . There is no specific limitation regarding the size of the catalyst (precursor) bodies to be used. The following structural features are however preferred.

The macroscopic size (average longest diameter) of the individual catalyst (precursor) bodies preferably ranges from

0.5 to 20mm, e.g. 1 to 10mm. Catalyst bodies of this size can be obtained by processes known in the art, for instance by pressing a dried calcined catalyst precursor material, newly crushing the pressed material and carrying out size- selecting steps such as sieving, before conducting the activation

(reduction) step. Instead of pressing, an extrudate may be formed.

According to one further embodiment, the catalyst precursor material is coated onto a carrier according to techniques known in the art prior to the reduction step. This coating of a carrier with the respective catalyst precursor materials can be equally effected at an earlier stage, for instance prior to the calcination treatment.

The carrier, which is preferably inert, can have any shape and surface structure . However, regularly shaped,

mechanically stable bodies such as spheres , rings , tube sections, half -rings , saddles, spirals or honeycomb carrier bodies or carrier bodies provided with channels such as , for exam le , fibre mats or ceramic foams are preferred . The size and shape of the carrier bodies is determined, for example, by the dimensions , primarily the internal diameter of the reaction tubes if the catalyst is used in tube or tube-bundle reactors . The diameter of the carrier body should then be between 1/2 and 1/10 of the internal diameter of the reactor . In the case of f luidised bed reactors , the carrier dimensions are determined, for example, by the fluid dynamics in the reactor. Suitable materials are, for example_., steatite, duranite, stoneware, porcelain, silicon dioxide, silicates, aluminium oxide, aluminates , silicon carbide or mixtures of these substances . The proportion of the layer of catalyst precursor material applied to the carrier is preferably 1 to 30% by weight, particularly preferred 2 to 20% by weight based on the total mass of the final carried catalyst material. The thickness of the catalyst material layer is preferably 5 to 300 jjm, particularly preferred 5 to 10 pm.

Manufacture of catalyst precursor material and activation by reduction

The claimed catalyst precursor material is preferably produced 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 aluminium salt (such as sodium aluminate) and at least one alkaline carbonate - containing precipitating agent (such as sodium

carbonate) ,

(c) mixing the first and second solutions whereby an

insoluble solid is formed,

(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 ,

It is preferred to conduct at least one washing step between steps (d) and (e) and/or step (e) and (f) , respectively, If the dried recovered solid obtained in step (e) is subjected to a washing step, it is preferred to newly dry the washed solid before subjecting the same to the final calcination step.

The present inventors have found that this process is

particularly suited to manufacture a catalyst precursor material that can be converted in a subsequent reduction step to high performance catalyst materials .

The first and second solutions described above may be mixed in any manner or 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 simultaneously mixing the two solutions such as by simultaneously adding the two solutions to a vessel . It is desirable that the mixing of the first and second

solutions in step (c) be conducted 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

simultaneously, the pH of the resulting mixture can be controlled by varying the rate of addition of the second solution which contains 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 utilized to form the first solution are copper and zinc salts such as nitrates, acetates, sulfates , chlorides , etc . It is presently

preferred, however, to use the nitrates of copper and zinc in the formation of the first solution . Any water-soluble aluminum salt can be utilized to prepare the second solution, and the aluminum salt generally is a basic aluminum salt such as sodium aluminate . Alumina gels can also be utilized even though, according to one preferred embodiment of the

invention, Al oxide present in the continuous Zn/Al phase is nei her obtained from an aluminum hydroxide sol or gel nor from colloidally dispersed AI2O3.

The second solution also contains at least one alkaline carbonate -containing water-soluble material such as such as 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 included 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, will result in a mixture having the desired pH . The pH of the mixture obtained by mixing the first and second solutions should be within the range of from about 5.5 to about 9.0 and more preferably is at least 6 , and most preferably at least about 6,0 to 7.0. As noted above , the pH of the mixture can be maintained as desired by adj sting the relative addition rates of the two solutions . Additionally, the mixture

obtained from the first and second solutions is preferably maintained at a temperature of from about 50-80°C (however preferably not over extended periods of time in order to suppress aging processes as explained below) , A precipitate is formed and recovered by techniques well known in the art such as by filtration, centrifugation, etc . The recovered precipitate preferably is washed with water to remove

impurities, dried by heating to a temperature of up to about 250°C, and finally calcined . Washing is for instance

conducted to reduce the content of alkali metals , preferably to values of 0.2 wt . -% or less, in particular 0.1 wt . -% or less . The actual drying temperature depends on the conditions chosen. In batch processes it is typically sufficient to dry by heating to a temperature of about 150°C or less, for instance 80°C to 120°C. In one preferred embodiment of the present invention, drying is effected by continuous spray drying. During spray drying the recovered insoluble solid is exposed to temperatures ranging preferably from 80 to 220°C. The spray dryer typically works with at least two temperature zones within this range which preferably include an inlet temperature higher than the temperature at the outlet. Spray drying may for instance be effected with an inlet temperature of 180· to 220°C and an outlet temperature of 80 to 120 °C, Preferably, spray drying is conducted continuously.

The present inventors have found that it is preferred to suppress aging processes in the manufacture of the catalyst

(precursor) material. For this reason it is considered advantageous to conduct steps (c) , (d) and (e) in a

continuous process . This may be achieved by continuous and simultaneous dosage of the first and second solution in step

(c) to the reactor vessel. While the second and first solution are mixed, in this manner, the insoluble solid is continuously recovered and introduced into a spray drying apparatus wherein the recovered solid is continuously dried.

If the granulate obtained from spray drying is subjected to a washing step, a second spray drying step may follow.

This continuous process ensures that little time lapses between the first formation of insoluble solid in step (c) and the recovery of the insoluble solid (from the mother liquid) in step (d) . In this manner, aging processes can be suppressed and the formation of a very homogenous and

preferably low crystalline or amorphous continuous Al/Zn phase is enhanced. According to one preferred embodiment, the time period between the formation of the insoluble solid in step (c) and the recovery (step (d) ) is shorter than Ih, preferably shorter than 50 min, more preferably shorter than 40min, for instance shorter than 30 min, e.g. 20 min or less. Aging processes can be recognized via colour changes of the insoluble solid being in contact with the mother liquid.

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

For the sake of convenience, this calcination reaction is usually conducted at atmospheric pressure. In principle it is, however, also possible to conduct this step under

elevated or reduced pressure, for instance within the range of atmospheric pressure ± 50% or ± 20%, As oxygen-containing atmosphere, air or a synthetic oxygen-containing atmosphere can be used. Depending on the other process conditions, oxygen is normally not employed in contents of more than 50 vol . - % . Suitable oxygen volume ratios are for instance 1 to 40 vol . % , 5 to 35 vol . - or 10 to 30 vol . -% . The remainder is nitrogen as in air or any other 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 is achieved by contacting the calcined

catalyst material with a hydrogen-containing atmosphere such as synthesis gas, pure hydrogen or hydrogen diluted with an inert gas {e.g. nitrogen, helium or argon) . In this reduction step a catalyst material as claimed arises by the segregation of crystalline Cu particles from the surrounding

oxide/carbonate phase, The reduction step is conducted under conditions known in the art, preferably at a temperature of from 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 used for the conversion O'f synthesis gas {see following description) could be used. According to one embodiment, the reduction is performed by- heating the catalyst precursor material in an atmosphere comprising 1 to 10 vol . - % hydrogen, preferably 2-7 vol . - % hydrogen, the remainder being an inert gas, such as nitrogen, argon or helium, to a temperature of 230 to 260°C. The heating rate is preferably 1-5 K/min and the precursor material is held at the final temperature preferably for at least 15 minutes , for instance 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 vol. -% 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. At both reduction stages the

precursor material is preferably held at the final

temperature over a time period of at least 15 minutes , for instance 30 minutes or more .

Process for the manufacture of methanol

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

According to one embodiment , the synthesis gas mixture

comprises for instance

CO 3 to 20 vol . -%, preferably 5 to 15 vol . -%,

CO2 1 to 12 vol . -% , preferably 2 to 8 vol . -%,

optionally an inert gas such as ¾ or helium in an amount of

1 to 30 vo1. - % , preferably 2 to 15 vol . - %, CH₄ 0 to 30 vol . - %, e . g less than 20 vol . -%,

¾ as remainde , Preferably, the reaction is conducted at a pressure of 10 to 150 bar, preferably 20 to 70 bar, more preferably 35 to 55 bar {each absolute pressure values) , and at a temperature of preferably 200 to 300°C over the catalyst (material) of the present invention.

The space velocity may be about 1000 to 50000, for instance 5000 to 30000 1 synthesis gas mixture per hour and 1 catalyst

Experimental Section;

Chemicals

The following gases of high purity were used: He (99,9999 %) , ¾ (99.9999 %) , N₂0/He {1% N₂0, 99.9995 %)

The following starting materials were used to prepare the catalyst materials :

Cu (N0₃) 2 3H₂0, Carl Roth, >= 99% p.. a.

Na₂0₃, Carl Roth, >= 99.8% p. a.

ZnO, Carl Roth, >= 99% p. a.,

Sodium aluminate , technical grade, Fisher Scientific.

Thermogravimetric analysis-evolved gas analysis (TGA-EGA)

TG curves of the hydroxy carbonate precursors were recorded on a Netzsch STA 449-C thermoba1ance with an attached quadrupol mass spectrometer for EGA (Pfeiffer Omnistar) . A heating rate of 2 K/min was applied in synthetic air.

Temperature programmed reduction (TPR)

TPR was performed by raising the temperature to 250 °C in a fixed bed reactor (CE instruments TPDRO 1100) with a heating rate of 2 K/min. H₂ consumption was monitored using a thermal conductivity detector,

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

Pore size and pore size distribution:

Nitrogen adsorption-desorption isotherm is measured at 77 K using for example an Autosorb- 1 instrument {Quantachrome ) . Prior to the adsorption, the sample is outgassed in vacuum at 353 K for 4 h. Calculation of the pore size distribution is performed using the desorption branch of the isotherm and the Barrett-Joyner-Halenda (BJH) method, as described in E . P . Barrett , L.G. Joyner, P.P. Halenda, J. Amer . Chem. Soc . 73 (1951) 373. Full adsorption/desorption isotherms in the p/ o range 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 Barret-Joyner-Halenda (BJH) method. The sample size is around 0.1 g .

Copper surface area Sp_n

The copper surface area was determined applying N₂0 reactive frontal chromatography with 1 vol . -% 2O in he1ium according to the method proposed by Chinchen et al . (G. C . Chinchen, C. M. Hay, H. D. Vanderwell, K. C. Waugh, J. Catal . 1987, 103, 79) at somewhat more moderate reaction conditions (O. Hinrichsen, T. Genger, M. Muhler, Chem. Eng. Technol . 2000, 11, 956-959) . XRD

For XRD the calcined samples of catalyst precursor material were reduced 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 K radiation. For reduction the temperature was increased linearly in a 5 vol . - % H₂ in He atmosphere (100 ml/min, 2 /min) to 250°C and maintained isothermal for 2 h . The reduced samples were cooled to room temperature in the reduction gas before collection of XRD patterns (30-100 °2Θ, 0.02° steps, 16 s counting/step) . The TOPAS software package (A. A. Coelho, Topas, General Profile and Structure Analysis Software for Powder Diffraction Data, Version 3.0, Bruker AXS GmbH , Karlsruhe, Germany, 2006 ) was used for refinements of XRD data.

XRD patterns of the samples of catalyst precursor materials were collected on a Stoe Stadi-p diffractometer equipped with a primary focusing Ge monochromator and a linear position sensitive detector (resolution 0.005⁰ /channel , step size 0.1° ) in the 2Θ range 4-80° with a counting time of 10s using Cu Ka radiation in transmission geometry.

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

A Philips CM200FIG microscope operated at 200 kV and equipped with an EDX spectrometer (T-TE CM-200F 147-5_» available from EDAX, Inc.) was used for TEM investigations. The coefficient of spherical aberration was C_s = 1,35 mm. The information limit was better than 0,18 nm allowing the principal phases to be identified in HRTEM images. High- resolution images with a pixel size of 0.016 nm were taken at the magnification of 1083000x with a CCD camera. The 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 into Genesis 5.21 were used. Reduced samples were transferred to the microscope in inert atmosphere. Ni grids covered with a 5 nm thick holey amorphous carbon film were used for specimen preparation. No liquids were used for specimen preparation.

The EDX spectra were taken with the specimen tilted by 30

+0.5 deg, and the TEM images without tilt.

When taking the EDX spectra of local compositions under illumination of 500nm 0 circles, the beam intensity was adjusted such that the signal registered by the detector had always about the same integral intensity. Further, exactly the same exposure time was used. In this manner, the counting statistics were fully comparable for all spectra obtained.

Reference Example 1 {calcined catalyst precursor material B)

Sample B was prepared in a similar manner as described in DE 101 60 486 Al in an automated laboratory reactor (Mettler- Toiedo Labmax) by constant pH precipitation at pH 6.5 and T = 65° C from 1 M aqueous solution of Cu, Zn and Al nitrates (Cu: Zn:Al=60 : 25 : 15) and 1.6 M Na₂C0₃ solution. The precipitate was aged for 3 h in the mother liquor . During aging the colour changed from light blue to green which indicates the formation of zincian malachite or rosasite and hydrotalcite-like phases. The sample was thoroughly washed with water, dried and calcined ( 3h, 330°C, 2 K/min) in static air.

Prior to calcination the sample was subjected to XRD investigation. It consisted of a mixture of a poorly crystalline zincian malachite or rosasite (Cu, Zn) ₂ (C0₃) (OH) ₂ ( ICDD 41-1390 , malachite) and a hydrotalcite-like phase (Cu, Zn) i-_xAl_x (OH) 2 (C0₃)x/2-m H₂0 (ICDD 37-629 with x = 0.25 and m = 4) and possibly additional X-ray amorphous phases .

The N2 adsorption/desorption isotherm of the calcined precursor material B (Reference Example 1) showed a hysteresis indicating capillary condensation in the pores . The surface area was determined to be 88 m²/g .

The pore size distribution of the calcined sample was determined using the BJH me hod and desorption data and is shown in Figure 5 ( "catalyst B" ) . Only one type of pores showing a maximum around 20 nm was observed and assigned to inter-particle pores . These results suggest that pores are only present in-between the nanostructured but non-porous oxide particles .

The calcined sample was also subj ected to a TPR analysis which gave the results shown in Figure 7 for "catalyst B" . The maximum of the TPR curve was at 179 °C. The results are discussed n connection with "catalyst A" (Example 1) .

Reference Example 2 (catalyst material B)

The calcined precursor material of Reference Example 1 was reduced in 5% ¾ (heating to 250°C at 2 K/min followed by 0.5 h at 250°C, flow rate 80 ml/min) in a fixed bed reactor- {TPDRO 1100, CE instruments) to obtain a catalyst material showing activity in the synthesis of methanol from synthesis gas.

HRTEM analysis of the reduced catalyst material revealed that it consisted essentially of three different types of phases with decreasing abundance, i.e. (i) the phase shown in Fig. 2, (ii) relatively large particles with small buried Cu grains and ( iii) large disordered needles with an Al content of more than 90 at . -% .

In phase (i) Cu particles of an average diameter < 10 nm were observed to be separated by small ZnO particles preventing them from sintering and forming a porous framework of individual particles . These areas of the catalyst were commonly observed and exhibited Cu-rich compositions near the nominal metal ratio.

The characteristic Al-rich composition of 20-30 at . -% found for phase (ii) as well as the sometimes observed hexagonal shape of these particles suggests that they have formed from the hydrotalcit-like precursor phase .

Phase (iii) presumably developed from an amorphous aluminum hydroxide precursor phase , which was not detected by XRD .

The inhomogeneity of the Reference catalyst material is also seen from an EDX analysis of the local compositions as shown in Figure 8. Catalyst B (□) shows a pronounced scattering compared to catalyst A (■) (= Example 2 as described below) . The blue grid lines mark the nominal composition .

The accessible copper surface SQ_U was determined by ¾0 chemisorption to be 36.1 + 1 m²/g .

The Cu lattice constant was determined via XRD to be 3.6138 ± 0.0008 A, which is close to the value 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) of the same Cu: Zn ratio as in Sample B (Reference example 1), The "first solution" was prepared by dissolving 87,0 g

Cu (N0₃) 2 · 3H₂0 in 200 ml water followed by the additiuon of 50 ml concentrated nitric acid {65 %) , After the addition of 12,2 g 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 by using 600ml of a 1.6 M Na₂C0₃ solution as precipitating agent to which 9.8g aluminate { a2 l20 x 3H₂0) solution was added under stirring .

An automatic lab reactor {Labmax, Metier-Toledo) was filled with 400 ml water and preheated to 65°C. Over a time period of 45 minutes, 600 ml of the above copper zinc nitrate solution were added while the above aluminate carbonate

solution was simultaneously added in a rate resulting in a pH value of the resulting mixture of the first and second solution between 6,0 and 7.0.

The resulting slurry of the insoluble solid, which formed during mixing, was continuously fed into a spray-dryer (Niro, jniet = 200 °C, T_outiet = 100 °C) after an estimated residence t me of 16 min in the reactor. The pump rate was such (about 35 ml/min) that the filling level in the reactor did not change .

The granulate obtained at the outlet of the spray-dryer was repeatedly slurried in water, stirred over 5min and filtrated off until the conductivity of the filtrate was less than 0.5 mS/cm (typically after the 5^th repeat) . After the last filtration step the solid wet filtration residue was slurried in about 11 of water and spray-dried under the same conditions as stated above.

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

XRD investigation prior to calcination indicated that, in contrast to the material of Reference Example 1, the uncalcined material was completely X-ray amorphous showing only weak and broad modulations of the background .

The uncalcined material was also subj ected to a TGA analysis as shown in Figure 4 which revealed the following. Up to ca . 300 °C the uncalcined catalyst precursor material decomposed in an ill-defined dehydroxlation step with almost linear mass loss mostly due to H₂0 emission. Only minor C0₂ emission is observed before a temperature around 463 °C and, hence , most of the carbonate persist the calcination treatment at a temperature of 330°C . The decarbo 1yation step contributes 13% to the overall mass loss of 30.5 % at 600°C (C0₂ content of claimed sample about 15.8%) .

XRD patterns of the calcined material showed only broad and weak reflections at the positions where peaks of CuO (ICDD 80-76) are expected . Characteristic peaks for Zn or Al compounds could not be observed . The continuous Zn/Al phase wherein the CuO particles are partly embedded can thus be considered as X-ray amorphous .

The 2 adsorption/desorption isotherms of the calcined intermediates of catalyst A (Example 1) was also of type V indicating the presence of mesopores . The surface area was determined to 114 m²/g.

The pore size distribution of the calcined sample was determined using the BJH method and desorption data and is shown in Figure 5 ("catalyst A" ) . A maximum around 20 nm is observed and assigned to inter-particle pores though in a relatively low abundance when compared with a second type of pores with radii of 2-3 nm. These small pores contribute considerably to the surface area suggesting that in catalyst A the oxide matrix itself might be porous.

The calcined sample was also subjected to a TPR analysis which gave the results shown in Figure 7 for "catalyst A" . The maximum of the TPR curve was at 18 7 ° C . Shoulders of the TPR profile of catalyst B (Reference Example 1) at the high and low temperature side are more pronounced compared to catalyst A confirming the lower degree of homogeneity. The maximum rate of reduction is observed at a significantly higher temperature for catalyst A indicating stronger metal- oxide interactions in agreement with the previously described microstrueture model.

Example 2 (catalyst material A)

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

The catalyst structure was investigated by HRTEM analysis as shown in Figure 1. The microstrueture of the catalyst material obtained in Example 2 was very homogeneous and no different types of materials were observed by TEM. Cu particles were nearly spherically shaped (Fig. 1) . Unlike catalyst B {Reference Example 2) , individual separated oxide particles are hardly observed and, consequently, the porous Cu/ZnO particle arrangement is absent in the new material. The Cu particles are partly embedded in the oxide matrix resulting in an arrangement that resembles a supported system with an intimate interface contact of metal particles and contiguous Cu depleted oxide. A statistically meaningful Cu particle size distribution was determined for both samples by measuring 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 into a size range of 4-9 ran, while the mean diameter {volume weighted) was 8,1 ± 2.4 nm (7.2 ± 2,2 nm for catalyst B} . Considering the similarity of Cu particle size and shape, it is assumed that differences in activity between this Example (A) and Reference Example 2 (B) are related to the microstructure of the ZnO/Al₂0₃ component and its interface contact to Cu particles . The microstructural differences are schematically illustrated in Fig. 3,

The homogeneity of the catalyst material was confirmed in an EDX analysis of the local compositions as shown in Figure 8 (cf . catalyst A (■) ) .

The average composition ( "nominal composition" ) of the catalyst material as determined by XRF 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 explained below. The average composition is indicated in Figure 8 by the crossing point of the two grid lines .

The local compositions shown in Fig . 8 were determined on 16 clusters of primary catalyst particles which had a total projected area of partially more than 500 nm x 500 nm . The local metal contents and local compositions were thus analyzed in a slightly different way than previously described and defined . It is believed that this difference has no impact on the assessment of the homogenity of the samples .

It is seen that , in contrast to the catalyst material of Reference Example 2, the local Cu, Zn and Al contents hardly differed 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 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 of reference example 2 was much bigger, 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 SQ_U was determined by ¾0 chemisorption to be 24.8 + 1.2 m²/g .

XRD data further confirmed that the Cu particles were in a non-equilibrium state, which is reflected by an enlarged Cu lattice constant. It was determined to be 3.618 ± 0.001 A by fitting of XRD data {Fig. 3) . This value is far removed from the value of bulk copper (3. SloA) . It can be speculated that the Cu lattice is distorted by enhanced metal/oxide interactions such as epitaxial stress at the interface or partial dissolution of zinc or oxygen in the Cu lattice across the interface leading to high intrinsic activity.

Example 3 {manufacture of methanol)

Catalytic testing was performed in a flow set-up equivalent to that described by O. Hinrichsen, T. Genger , M. Muhler , Chew. Eng. Technol, 2000, 11, 956-359. For fast on-line gas analysis, a calibrated quadrupole mass spectrometer (Pfeiffer Vacuum, Thermostar) was used.

A glass-lined stainless steel microreactor was filled with 100 mg catalyst (sieve fraction 250-355 μπι) . The catalyst precursor materials A (Example 2 ) and B (Reference Example 2), respectively, were reduced as follows: (i) by heating in a gas mixture of 2.0 % H₂/He to 175 °C (at 1 K min^"1) followed by holding the material at 175 °C over 15h and (ii) subsequently heating in 100% H₂ to 240 °C (at 1 K min^"1) followed by holding the material at 240°C over 30 min.

The "initial activity" of the catalyst under steady-state conditions was determined at 220°C and at 10 bar pressure, using a flow rate of 50 N mi min^"1. A mixture of 72% H₂, 10%

CO, 4% C0₂ and 14% He was used as methanol synthesis feed gas (purity 99,9395 %) . Helium was added to simulate the B½ content of synthesis gas. In order to test the catalysts for methanol synthesis activity, they were exposed to the feed and heated with 10 K/min to the standard reaction temperature (220°C) at which the "initial activity" was measured.

Subsequently the catalyst was cooled down in the feed at atmospheric pressure. Overnight, the catalyst was heated in the feed (at atmospheric pressure) to 513 K (240°C) at a very slow heating rate (0.5 K/min, i.e. 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 to the measured value. In this way, the calibration of the MS can be double checked. This overnight procedure at

relatively high temperature (compared to the standard testing temperature of 220°C) is intended to simulate catalyst deactivation over longer 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 decreased to 220 °C and the activity was measured again at 10 bar and 220 °C with the same feed and flow rate as on day 1 , Measurements at this second day are referred to as "final activity" . In these tests catalyst A (Example 2 ) showed a higher initial and final activity than catalyst B (Reference Example 2) as indicated below in table 1.

Table 1

Initial Activity Final Activity "Stability"

Catalyst A 13, 1 12 , 6 mraol / g h 96,2 %

Catalyst B 11, 56 10,82 mraol / g h 93 , 6 %

Claims

C L A I M S

1. Cu/Zn/Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum wherein copper and zinc are present together in a greater molar amount than aluminum, and

wherein the standard deviation of the local molar Al content, as measured by EDX, is not more than 50%.

2. Cu/Zn/Al catalyst precursor material comprising oxides and carbonates of copper, zinc and aluminum wherein copper and zinc are present together in a greater molar amount than aluminum, and

wherein the reduction of this precursor material in the presence of hydrogen leads to a catalyst material, in which discrete crystalline Cu particles are partly embedded in a continuous phase comprising oxides and carbonates of at least Zn and Al, said crystalline Cu particles having a lattice constant of 3.615 A or more, preferably 3.615 to 3.621 A.

3. 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 % by mol , preferably 10 to 20 % by mol based on all metal constituents.

4. Cu/Zn/Al catalyst precursor material according to claim

1 , 2 or 3 , wherein the standard deviation of the local molar Zn content, as measured by EDX, is not more than. 40% and/or the standard deviation of the local molar Cu content, as measured by EDX, is not more than 25%,

5. Cu/Zn/Al catalyst precursor material according to claim

1, 2, 3 or 4 wherein the degree of crystallini ty is less than 10% as measured by HRTEM.

6, Cu/Zn/Al catalyst precursor according to any of claims

1, 2, 3, 4 or 5 wherein the carbonate content,

expressed as CO2 and measured by TGA, is 5 wt . - % or more, preferably 10 wt . -% or more.

7, Cu/Zn/Al catalyst precursor material according to any of claims 1, 2, 3., 4, 5 or 6 which fulfils at least one of the following two conditions:

(i) the BET surface as measured with N² at 77K is 90 m²/g or more, preferably 100 or more, more

preferably 110 m²/g or more, and

(ii) it has pores with a size distribution measured by BJH wherein pores having radii of 1 to 10 nm account for 45 to 90 % of the total porosity and pores having radii of more than 10 and up to 100 nm account for 55 to 10 % of the total porosity.

8, Cu/Zn/Al catalyst precursor according to claim 1 having a maximum rate of reduction (TPR) at a temperature of 180 °C or more, preferably at 184 to 190°C.

9. Cu/Zn/Al catalyst material comprising discrete

crystalline Cu particles partly embedded in a

continuous phase comprising oxides and carbonates of at least Zn and Al

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 % by mol , based on all metal constituents , and

wherein the lattice constant of the crystalline Cu particles is 3.615 A or more , preferably 3.615 to 3.621 A and said catalyst material is preferably obtainable by reducing the catalyst precursor material of any of claims 1, 2 , 3, 4, 5 , 6 , 7 or 8 in the presence of hydrogen .

10. Cu/ n/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 ran.

11. Cu/Zn/Al catalyst material according to claim 3 or 10 wherein at least one of the following conditions is s t i sti ed:

{1} the standard deviation of the local molar Al

content, as measured by EDX, is not more than 50%,

(2) the standard deviation of the local molar n

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%.

12. Process for the manuf cture of a catalyst precursor

material according to any of claims 1, 2, 3, 4, 5_» 6, 7 or 8 comprising the steps of

(b) preparing a second solution containing at least one

water-soluble basic aluminium salt and at least one alkaline carbonate -containing precipitating agent ,

(c) mixing the first and second solutions whereby an

insoluble solid is formed,

(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 .

13. Process according to claim 12 wherein the drying is effected by continuous spray drying , preferably at a temperature of 80°C to 220°C.

14. Process according to claim 12 or 13 wherein steps (c) , (d) and (e) are conducted in a continuous proces .

15. Process according to claim 12 , 13 or 14 wherein the time period between the formation of the insoluble solid in step (c) and the recovery of the insoluble solid in step (d) is shorter than 60 min, preferably shorter than 30 min.

16. Catalyst comprising the catalyst material of any of claims 9, 10 or 11.

17. Process for the manufacture of methanol comprising the step of contacting a gas mixture comprising hydrogen, carbon monoxide and carbon dioxide with the catalyst of claim 16.