Method for preparing copper-containing catalyst

Abstract

The present invention describes a method for preparing a copper-containing catalyst, the method comprising the steps of: (a) mixing an acidic copper-containing solution with a first alkaline precipitant solution in a first precipitation step to form a first precipitate, (b) mixing an acidic aluminum-containing solution with a second alkaline precipitant solution in a second precipitation step to form a second precipitate, the acidic aluminum-containing solution further comprising one or more metal compounds selected from copper compounds, zinc compounds and promoter compounds, (c) contacting the first precipitate and the second precipitate together in a further mixing step to form a catalyst precursor, and (d) washing, drying and calcining the catalyst precursor to form the copper-containing catalyst, wherein a silica precursor is included in the first precipitation step, the second precipitation step or the precipitate mixing step to provide a catalyst having a silica content expressed as SIO2 in the range of 0.1 wt% to 5.0 wt%.

Description

[0001] The present invention relates to a copper-containing catalyst, in particular to a method for preparing a copper-containing catalyst suitable for water-gas shift reaction and methanol synthesis.

[0002] Copper-containing catalysts for such reactions are typically prepared by forming small discrete particles of an intimate mixture of copper oxide and one or more oxidizing materials (typically including zinc oxide) into pellets that are not substantially reduced under the conditions of the conversion reaction process. The intimate mixture is typically prepared by precipitating a copper compound and a compound that can be converted to another oxidizing material, and / or precipitating a copper compound in the presence of another oxidizing material or a compound that can be converted thereto, followed by calcination to convert the precipitated copper compound and, if desired, other components into oxides.

[0003] In some cases, the copper-containing catalysts have been modified with silica.

[0004] US6048820 discloses a methanol synthesis catalyst modified with silica prepared in a single precipitation step using aluminium nitrate. We have found that the material prepared using this method has relatively low activity.

[0005] EP0742193 discloses a method for producing methanol in the presence of a catalyst, wherein the catalyst is obtained by mixing (a) a previously prepared copper and zinc precipitation slurry with (b) an aluminum oxide precursor separately prepared from a water-soluble aluminum salt and an alkaline precipitant in a slurry state to obtain a composition containing copper, zinc, and aluminum, and washing, drying, and then calcining the composition. Silica may be added to the composition.

[0006] CN101306369 discloses a catalyst preparation method comprising: (1) precipitating an acidic Al salt solution by reaction with a sodium carbonate solution also containing sodium silicate; (2) coprecipitating a Cu compound and a Zn compound by reaction with an alkali metal carbonate; and (3) mixing the two obtained coprecipitates, aging them, and then filtering, washing, drying, and calcining them. We have found that catalysts prepared by this route using an acidic Al solution have relatively low initial activity and poor stability. This may be due in part to the high levels of residual alkali found in materials prepared via this method.

[0007] We have discovered an alternative, simpler preparation method which provides improved catalyst performance.

[0008] Accordingly, the present invention provides a process for preparing a copper-containing catalyst, the process comprising the steps of: (a) mixing an acidic copper-containing solution with a first alkaline precipitant solution in a first precipitation step to form a first precipitate, (b) mixing an acidic aluminum-containing solution with a second alkaline precipitant solution in a second precipitation step to form a second precipitate, the acidic aluminum-containing solution further comprising one or more metal compounds selected from the group consisting of copper compounds, zinc compounds and promoter compounds, (c) contacting the first precipitate and the second precipitate together in a further mixing step to form a catalyst precursor, and (d) washing, drying and calcining the catalyst precursor to form the copper-containing catalyst, wherein a silica precursor is included in the first precipitation step, the second precipitation step or the precipitate mixing step to provide a catalyst having a silica content, expressed as SiO2, in the range of 0.1 wt% to 5.0 wt%.

[0009] The present invention also includes a catalyst obtainable by the method and a method selected from methanol synthesis, methanol steam reforming and water gas shift using the catalyst.

[0010] By precipitating aluminum in the presence of one or more metal compounds selected from copper compounds, zinc compounds, and promoter compounds, and by including a silica precursor, the present method provides a catalyst having high initial activity and excellent stability. Applicants have discovered that the method produces a material that does not retain high levels of unwanted alkali, does not produce an unwanted dawsonite phase, and produces a high surface area support phase and small malachite crystallite size. In addition, the inclusion of a small amount of silicon produces a catalyst with enhanced stability.

[0011] The method comprises (a) mixing an acidic copper-containing solution with a first alkaline precipitant solution in a first precipitation step to form a first precipitate. The solutions are preferably all aqueous. The acidic copper-containing solution can be formed by dissolving copper or copper oxide in a suitable acid such as nitric acid, or by dissolving one or more soluble copper compounds in water and adding acid as necessary. The one or more copper compounds can be selected from copper (II) nitrate, copper (II) acetate, or other water-soluble copper compounds or salts. Copper (II) nitrate is preferred. The acidic copper-containing solution can usefully contain other components suitable for inclusion in the copper catalyst. Specifically, the acidic copper-containing solution can contain one or more soluble zinc compounds. The one or more zinc compounds can be selected from zinc (II) nitrate, zinc (II) acetate, or other water-soluble zinc compounds or salts. The acidic copper-containing solution can also contain one or more promoter compounds selected from compounds of Mg, Co, Mn, V, Ti, Zr, or rare earth elements. Promoters can stabilize copper or enhance the properties of the support phase. Magnesium compounds and zirconium compounds are preferred. Suitable magnesium compounds and zirconium compounds are magnesium nitrate and zirconyl nitrate. Suitable promoters for water-gas shift catalysts include potassium and / or cesium. If desired, an acid, preferably nitric acid, may be added to the acidic copper solution. Nitrates and nitric acid are preferred because they do not leave catalyst poisons in the catalyst upon calcination.

[0012] The first alkaline precipitant solution may comprise an alkali metal hydroxide or ammonium hydroxide, but this is less preferred. Advantageously, the first alkaline precipitant solution is preferably composed of an alkali metal carbonate or bicarbonate, or a mixture thereof, to precipitate the basic copper carbonate material. Sodium carbonate or potassium carbonate solutions are preferred. The first alkaline precipitant solution may also contain one or more of the aforementioned promoter metals. The acidic copper-containing solution and the first alkaline precipitant solution may be added to the first precipitation vessel sequentially, but are preferably added simultaneously to the first precipitation vessel, such that the pH in the first precipitation vessel is maintained between 6 and 9, preferably between 6 and 7. The precipitation step forms a precipitate, which is advantageously mixed to form a slurry. If desired, the coprecipitate slurry may be aged to homogenize the precipitate and mature crystalline material. Aging of the coprecipitate slurry may be performed in the first aging vessel in a batch or semi-continuous process, whereby an aqueous slurry of the precipitated material is maintained in one or more stirred vessels for a period of time. Suspension of the coprecipitate in the liquid may be achieved solely by stirring, the intensity of which depends on the tendency of the particles to settle and the viscosity. Alternatively, the coprecipitate slurry can be aged in a pulse flow reactor as described in WO2008 / 047166 (incorporated herein by reference). Precipitation and aging can be carried out at temperatures ranging from 10°C to 80°C, but are preferably carried out at elevated temperatures, i.e., in the range of 40°C to 80°C, more preferably 50°C to 80°C, and especially 60°C to 80°C, as this has been found to produce small crystallites that provide a higher copper surface area after calcination. Conditions can be selected to produce crystalline compounds of the magnesite, chalcocite, chalcocite, or malachite type, for example. Coprecipitation and aging are preferably operated to produce malachite [Cu2(CO3)(OH)2], smithsonite [ZnCO3], and / or zincite malachite [(Cu / Zn)2(CO3)(OH)2] phases, as determined by XRD. However, in the present method, the first precipitate does not require aging.

[0013] The method further requires step (b): in a second precipitation step, mixing an acidic aluminum-containing solution with a second alkaline precipitant solution to form a second precipitate, wherein the acidic aluminum-containing solution further comprises one or more metal compounds selected from copper compounds, zinc compounds, and promoter compounds. The acidic aluminum-containing solution can be formed by dissolving the one or more aluminum compounds in water and adding an acid as necessary. The one or more aluminum compounds can be selected from aluminum nitrate, aluminum acetate, or other acidic water-soluble aluminum compounds or salts. Aluminum nitrate is preferred. In this method, the acidic aluminum-containing solution contains one or more other components suitable for inclusion in the copper catalyst. Specifically, the acidic aluminum-containing solution contains one or more metal compounds selected from copper compounds, zinc compounds, and promoter compounds. The one or more zinc compounds can be selected from zinc (II) nitrate, zinc (II) acetate, or other water-soluble zinc compounds or salts. The one or more copper compounds can be selected from copper (II) nitrate, copper (II) acetate, or other water-soluble copper compounds or salts. The one or more promoter compounds can be selected from compounds of Mg, Co, Mn, V, Ti, Zr, or rare earth elements. Magnesium compounds and zirconium compounds are preferred. Suitable magnesium and zirconium compounds are magnesium nitrate and zirconyl nitrate. Suitable promoter compounds for water-gas shift catalysts include potassium nitrate and / or cesium nitrate. Although one or more copper compounds may be included in the second precipitation step, it is preferred to include one or more zinc compounds and / or one or more promoter compounds, such as one or more magnesium compounds, in the acidic aluminum-containing solution. If desired, an acid, preferably nitric acid, may be added to the acidic aluminum-containing solution.

[0014] In the second precipitation step (b), one or more metal compounds selected from copper compounds, zinc compounds, and promoter compounds are co-precipitated with the aluminum. When copper is present, the amount of copper contained in the second precipitate may be in the range of 0.5% to 20% by weight of the total copper in the catalyst, preferably 0.5% to 10% by weight of the total copper in the catalyst. When zinc is present, the amount of zinc contained in the second precipitate may be in the range of 0.5% to 50% by weight of the total zinc in the catalyst, preferably 0.5% to 40% by weight of the total zinc in the catalyst, and more preferably 0.5% to 30% by weight of the total zinc in the catalyst. When a promoter such as magnesium or zirconium is present, the amount of promoter metal in the second precipitate may be in the range of 0.5% to 100% by weight of the total promoter metal added. Precipitating the aluminum compound using a carbonate precipitant in the absence of copper, zinc, or promoter metals may form a dawsonite-type phase, which may be detrimental to the initial activity and long-term stability of the catalyst.

[0015] The second alkaline precipitant solution used in the second precipitation step may comprise an alkali metal hydroxide, or an alkali metal carbonate, bicarbonate, or a mixture thereof. Preferably, the second alkaline precipitant solution consists of an alkali metal hydroxide. The alkali metal hydroxide may be sodium hydroxide or potassium hydroxide, or a mixture thereof.

[0016] Preferably, the second precipitation step comprises mixing an acidic aluminum-containing aqueous solution (such as an aluminum nitrate solution) containing one or more zinc compounds (such as zinc nitrate) and / or promoter compounds (such as magnesium nitrate and / or zirconyl nitrate) with a second alkaline aqueous precipitant solution (particularly sodium hydroxide or potassium hydroxide solution). The acidic aluminum-containing solution and the second alkaline precipitant solution can be added to each other in the second precipitation vessel, but are preferably added to the second precipitation vessel simultaneously, such that the pH in the second precipitation vessel is maintained between 5 and 9, preferably between 6 and 8. The second precipitation step is preferably mixed or stirred to form a slurry of precipitate. The optional aging of the precipitate slurry can be carried out using the methods described for the first precipitate. Aging of the second precipitate is preferred. Precipitation and aging can be carried out at a temperature in the range of 10°C to 80°C, but are preferably carried out in the range of 20°C to 70°C. This has been found to produce a suitable aluminum-containing support phase with a high surface area.

[0017] It should be understood that the above steps (a) and (b) can be carried out in any order, i.e. step (a) can be carried out before or after step (b), or step (a) and step (b) can be carried out simultaneously. These steps can be conveniently carried out in separate precipitation vessels.

[0018] The method also requires step (c): contacting the first and second precipitates in a mixing step to form a catalyst precursor. This step can be performed by recovering the precipitates from the first and second precipitation steps, for example by filtration or centrifugation, and then mixing the recovered precipitates in a slurry of water or another suitable solvent. However, it is more convenient to mix the slurries of the first and second precipitates in a mixing vessel. Preferably, the precipitates are not separated or washed prior to the mixing step (c).

[0019] The first precipitate can be added to the second precipitate or vice versa, or the two slurries can be mixed simultaneously at a controlled rate. The precipitate can be subjected to an aging step before mixing with other precipitates, or can be added without prior aging. Preferably, the second precipitate is aged before mixing with the unaged first precipitate, and then the mixed precipitate slurries are subjected to a final aging step in step (c). This optional final aging step can be carried out using the method described above for the first precipitate. The precipitate slurries can be mixed under stirring or agitation, and the resulting mixture is maintained in a contact container at a high temperature to allow mixing to occur between the precipitates.

[0020] In some embodiments, step (c) can be performed simultaneously with step (a) or step (b), i.e., the solution from step (a) can be added to the precipitate of step (b), or the solution of step (b) can be added to the precipitate of step (a). In one arrangement, the first precipitation step (a) and the precipitation contacting step (c) are performed simultaneously in the same vessel.

[0021] The resulting mixture may be mixed for a period of time of 0.1 hour to 24 hours at a temperature in the range of 40° C. to 80° C., more preferably 50° C. to 80° C., especially 60° C. to 80° C. After the mixing and aging process has occurred, the resulting catalyst precursor may be conveniently recovered by filtration, decantation, or centrifugation.

[0022] In the present process, a silica precursor is included in the first precipitation step (a), the second precipitation step (b), and / or the contacting step (c) to provide a catalyst having a silica content expressed as SiO2 of 0.1% to 5.0% by weight. We have found that lower levels of silica are surprisingly superior in terms of stability. Thus, in preferred embodiments, the silica content of the calcined catalyst expressed as SiO2 is in the range of 0.1% to 3%, 0.1% to 2%, and especially 0.2% to 1.0%.

[0023] The silica precursor may suitably be colloidal silica or silica sol and / or a water-soluble silicon compound, such as an alkali metal silicate, for example potassium silicate. Organic silicates, including alkyl silicates, such as tetramethyl orthosilicate and tetraethyl orthosilicate, may also be used. Silica stabilizes the copper during use and thereby improves the long-term activity of the catalyst compared to catalysts that do not contain silica.

[0024] If an acidic silica sol is used, it can be added to the acidic copper-containing solution in the first precipitation step and / or to the first precipitation vessel and / or to the first aging vessel (if present). Similarly, the silica sol can be added to the acidic aluminum-containing solution in the second precipitation step and / or to the second precipitation vessel and / or to the second aging vessel (if present). The silica sol can also be added to the mixture of precipitates in the contacting step (c). Particularly suitable silica sols comprise aqueous dispersions of colloidally dispersed silica having a particle size in the range of 10 nm to 20 nm. The pH of the dispersion can be <7, preferably in the range of 2 to 4. The silica concentration in the sol can be 100 g / L to 400 g / L. Such sols are commercially available, for example, as Nissan Chemicals Snowtex-O and Grace Ludox HSA.

[0025] If a water-soluble silicate (such as an alkali metal silicate) or alkaline silica sol is used, it can be added to the alkali carbonate solution and / or to the first precipitation vessel and / or the first aging vessel (if present) in the first precipitation step. Similarly, the alkali metal silicate or alkaline silica sol can be added to the alkaline precipitant solution and / or to the second precipitation vessel and / or the second aging vessel (if present) in the second precipitation step. The alkali metal silicate or alkaline silica sol can also be added to the precipitate mixture in the contacting step (c). Suitable alkali metal silicates are sodium silicate and potassium silicate. Such alkali metal silicates are commercially available, for example, as PQ Corporation Kasil 1, PQ Corporation Kasolv 16, or Zaclon LLC Zacsil 18. The amount of silicon (expressed as SiO2) in the alkali metal silicate solution can range from 5% to 40% by weight, preferably from 15% to 30% by weight. When an alkali metal silicate is used, the alkali metal in the alkali metal silicate may be matched with the alkali metal or alkali metal aluminate in the alkaline precipitant solution.

[0026] If an organosilicate such as an alkyl silicate of formula Si(OR)4 (wherein R = C1-C4 alkyl) is used, since it will hydrolyze on contact with water, it is preferably added to the first precipitation vessel and / or the second precipitation vessel, the first aging vessel and / or the second aging vessel, or to the mixed precipitate in contact step (c).

[0027] In step (d), the recovered catalyst precursor is washed to remove residual soluble salts that may act as poisons or contaminants during the use of the catalyst. The washing of the catalyst precursor can be carried out using conventional equipment such as a plate and frame filter press, a centrifuge or other suitable washing equipment, for example, by reslurrying the catalyst precursor one or more times in a deionized water, or by dynamic cross-flow filtration using Artisan thickener or Shriver thickener before recovery. For methanol synthesis catalysts, the alkali metal content in the dried catalyst precursor should advantageously be reduced to less than 0.2% by weight, preferably less than 0.1% by weight (the weight % being calculated on a non-destructive basis as the corresponding alkali metal oxide on the dry material).

[0028] The method also requires the steps of drying and calcining the catalyst precursor to form the copper-containing catalyst. Drying can include heating the moist mixture in discrete stages or continuously over an extended period of time until a maximum temperature is reached. The drying step can be carried out at a temperature in the range of 90°C to 150°C, preferably 90°C to 130°C, in air or an inert gas, using conventional drying equipment such as an oven, rotary dryer, spray dryer, or the like.

[0029] The dry composition is typically in the form of a powder. The average particle size (as determined by sieve fraction, i.e., weight average particle size) may be in the range of 10 μm to 1000 μm or 10 μm to 300 μm (micrometers). The dry composition may comprise one or more basic carbonates of copper and zinc, as well as aluminum oxide and silicon dioxide or compounds thereof.

[0030] The dried composition is calcined and advantageously shaped to form a catalyst. The dried composition may be calcined, i.e. heated, to convert the copper compound and any zinc compound and any promoter compound into their corresponding oxides before shaping, or less preferably, the dried composition may be shaped into shaped units before calcining. The latter method is less preferred because calcining of the shaped units generally reduces their strength and makes it more difficult to control the pellet density. Calcination may be carried out at a temperature in the range of 250°C to 500°C, preferably 280°C to 450°C, more preferably 280°C to 350°C. Lower temperatures provide lower pellet stability, while higher temperatures significantly reduce the initial activity resulting from the high copper dispersion. Calcination may be carried out in air or an inert gas such as nitrogen, but air or another oxygen-containing gas is preferred. The calcined product is typically in the form of a powder.

[0031] The catalyst is preferably granular. Therefore, the dried or calcined powder can be subjected to granulation, optionally after pre-compacting the powder (this can improve the granulation process). The pellet can be suitably cylindrical pellets. The cylindrical pellets used for the carbon oxide conversion process suitably have a diameter in the range of 2.5mm to 10mm, preferably 3mm-10mm and an aspect ratio (i.e. length / diameter) in the range of 0.5 to 2.0. Alternatively, the molding unit can be in the form of a ring. In one embodiment, the molding unit is in the form of a cylinder having two or more, preferably 3 to 7 grooves extending along its length. Suitable dome cylindrical shapes with one or more grooves are described in our WO2010 / 029325 and WO2017 / 072480, which are incorporated herein by reference.

[0032] The pellets, in particular cylindrical pellets with flat or domed ends as described above, are advantageously made to have a density of 1.8 g / cm 3 Up to 2.5g / cm 3 , preferably 1.9 g / cm 3 Up to 2.4g / cm 3 The pellet density is within the range of 2.4 g / cm. The pellet density can be easily determined by calculating the volume from the pellet dimensions and measuring its weight. As the density increases, the void volume in the molded unit decreases, which in turn reduces the permeability to the reaction gases. Therefore, for >2.4 g / cm 3For a density <1.8 g / cm2, the catalyst reactivity may be less than optimal despite a high volume content of copper. 3 The density and crush strength of these materials may not be sufficient for long-term use in modern carbon oxide conversion processes.

[0033] The relative amounts of the copper-containing solution, the zinc-containing solution, the aluminum-containing solution, the promoter solution, and the silica precursor can be adjusted to produce a composition suitable for use as a catalyst. The copper oxide content (expressed as CuO) of the calcined catalyst can be in the range of 30% to 70% by weight. Within this range, a copper oxide content in the range of 50% to 70% by weight, preferably 60% to 70% by weight, has general application for methanol synthesis, while for the water-gas shift reaction, the copper oxide content can be lower, particularly in the range of 30% to 60% by weight. Suitably, the copper (II) oxide content of the calcined catalyst is in the range of 50% to 68% by weight. As described above, zinc is preferably included in the first precipitation step. The weight ratio of Cu:Zn (expressed as CuO:ZnO) in the calcined catalyst may be 1:1 or higher, but is preferably in the range of 2:1 to 3.5:1, especially 2.5:1 to 2.75:1, for methanol synthesis catalysts, and preferably in the range of 1.4:1 to 2.0: 1 for water gas shift catalysts. In the methanol synthesis catalyst, the catalyst preferably contains 15 to 50 wt%, preferably 20 to 35 wt% zinc oxide.

[0034] The calcined catalyst contains alumina, which may be present in an amount ranging from 5% to 40% by weight, preferably from 6% to 20% by weight (expressed as Al2O3). The alumina may be present as boehmite AlOOH, and / or as a transition alumina such as gamma alumina, and / or as a metal aluminate such as zinc aluminate.

[0035] The calcined catalyst contains silica and may have a Si:Al atomic ratio in the range of 0.004 to 0.2:1. The amount of silica in the catalyst appears to be optimal when the Si:Al atomic ratio is in the range of 0.03 to 0.09:1. Therefore, the amount of silica in the catalyst is relatively low and may be present in the calcined catalyst in an amount in the range of 0.1 wt% to 5.0 wt%, preferably 0.1 wt% to 2.0 wt%, and more preferably 0.2 wt% to 1.0 wt%. Higher amounts of silica reduce the activity of the catalyst and may create acid sites that reduce selectivity in methanol production.

[0036] If a promoter is included in the first and / or second precipitation step, the calcined catalyst may contain promoter oxides, such as magnesium oxide and / or zirconium oxide, in an amount ranging from 0.5% to 5% by weight.

[0037] Preferred methanol synthesis catalysts consist essentially of oxides of copper, zinc, aluminum, magnesium and silicon.

[0038] The dried catalyst prepared by this method can have a malachite, such as zincite malachite, having a crystal size of less than 10 nm, preferably less than 9 nm, more preferably less than 8 nm. The crystal size can be greater than 3 nm. The malachite crystal size can be determined using X-ray diffraction (XRD).

[0039] The calcined catalyst prepared by this method may have a 2 / g catalyst, preferably ≥50m 2 / g catalyst, more preferably ≥55m 2 Copper surface area of ​​​​about 60 or 65m / g catalyst can be achieved. 2 The copper surface area of ​​100 g of catalyst is determined by measuring the surface area of ​​100 g of catalyst. These surface areas are suitably determined on samples of crushed catalyst pellets. The copper surface area can be readily established by reactive frontal chromatography, for example as described in EP-A-0 202 824.

[0040] The BET surface area of ​​the shaped catalyst, as determined by nitrogen physical adsorption (according to ASTM method D 3663-03), may be ≥ 75 m 2 / g, preferably ≥100m 2 / g, more preferably ≥115m 2 / g. Achievable up to about 130m 2 The BET surface area is determined on crushed catalyst pellet samples.

[0041] In the catalyst, zinc oxide, aluminum oxide, silicon dioxide, and promoter oxides (if present) are not substantially reduced to metals under the carbon oxide conversion process conditions and are generally present in the catalyst as oxides. In contrast, copper oxide is more readily reduced to its active elemental form. Copper can be reduced ex situ or in situ to form catalytically active copper metal grains prior to use.

[0042] The catalyst prepared by this method can be used in any carbon oxide conversion process comprising reacting a process gas containing carbon oxides, the process gas containing at least one of carbon monoxide and carbon dioxide and additionally containing hydrogen and / or steam, in the presence of a catalyst. The term "carbon oxide" herein includes at least one of carbon monoxide and carbon dioxide. The catalyst is particularly suitable for methanol synthesis, methanol steam reforming, and the water gas shift reaction.

[0043] The catalyst may be preactivated in situ by exposing it to a reducing gas stream, preferably containing hydrogen, to convert copper oxide into elemental copper. Thus, the method may further comprise the steps of: (i) activating the catalyst by contacting it with a reducing gas stream; and (ii) reacting a process gas containing carbon oxides in the presence of the catalyst to form a product stream, the process gas containing at least one of carbon monoxide and carbon dioxide and additionally containing hydrogen and / or steam. Activation may be carried out using a hydrogen-containing gas, including a synthesis gas containing hydrogen and carbon oxides, at a temperature above 80° C. and a pressure in the range of 1 bar to 50 bar (gauge). The maximum reduction temperature is advantageously between 150° C. and 300° C.

[0044] The present invention includes methods of using the catalyst, specifically:

[0045] A. Methanol synthesis, wherein a gas mixture containing one or two carbon oxides (i.e. carbon monoxide and / or carbon dioxide) and hydrogen is heated at a temperature in the range of 200° C. to 320° C., a pressure in the range of 20 bar to 250 bar, in particular 30 bar to 120 bar (absolute pressure) and a temperature in the range of 500 to 20,000 h. -1 The catalyst is passed through the catalyst at a space velocity within a range of 100 to 200 ℃. The method can be carried out on a once-through or recirculating basis and can involve cooling by an indirect heat exchange surface in contact with the reaction gas, or by subdividing the catalyst bed and cooling the gas between the beds by injecting a cooler gas or by indirect heat exchange. For this method, the catalyst preferably contains copper, zinc oxide and optionally magnesium oxide, as well as aluminum oxide and silicon dioxide. The catalyst can be used in a methanol synthesis process in which natural gas is steam reformed or autothermally reformed with oxygen to produce a synthesis gas containing carbon monoxide, carbon dioxide and hydrogen, or in a process in which the synthesis gas is rich in carbon monoxide and is derived from coal or biomass gasification. The catalyst is particularly useful in a methanol synthesis process in which the synthesis gas is essentially formed by hydrogen and carbon dioxide, especially in which the hydrogen and / or carbon dioxide are recovered only from renewable resources, such as water electrolysis to generate hydrogen and recovering CO2 from waste gases such as combustion gases or landfill gas.

[0046] B. Modified methanol synthesis, wherein the catalyst also contains a surface area of ​​50-300m 2 g -1 The free alumina, or another acidic catalyst, makes the synthesis product relatively rich in dimethyl ether. The temperature, pressure and space velocity are similar to those of methanol synthesis, but the synthesis gas can contain hydrogen and carbon monoxide in a molar ratio of less than 2.

[0047] C. Low-temperature shift reaction, in which a gas containing carbon monoxide (preferably less than 4% v / v on a dry basis) and steam (the molar ratio of steam to total dry gas typically being in the range of 0.3 to 1.5) is passed over a catalyst in an adiabatic fixed bed at an outlet temperature in the range of 200° C. to 300° C. at a pressure in the range of 15 bar to 50 bar (absolute). Typically, the inlet gas is the product of a "high-temperature shift" in which the carbon monoxide content has been reduced by reaction over a high-temperature shift catalyst (such as an iron or zinc aluminate catalyst) at an outlet temperature in the range of 400° C. to 500° C., followed by cooling by indirect heat exchange. The outlet carbon monoxide content from the low-temperature shift step is typically in the range of 0.1% v / v to 1.0% v / v on a dry basis, especially less than 0.5% v / v.

[0048] D. Moderate temperature shift, in which a gas containing carbon monoxide and steam is fed to the catalyst at a pressure in the range of 15 to 50 bar (absolute) at an inlet temperature typically in the range of 200° C. to 240° C., although the inlet temperature can be as high as 280° C., and an outlet temperature typically up to 300° C. but can be as high as 360° C. These conditions are more severe than in B, making the new catalyst expected to be particularly advantageous.

[0049] E. Medium and low temperature shift with heat exchange (also known as isothermal shift), in which the reaction in the catalyst bed occurs in contact with the heat exchange surface. The coolant is conveniently water at a pressure such that partial or complete boiling occurs. Suitable pressures are 15 to 50 bar (absolute), and the resulting steam can be used, for example, to drive a turbine or provide process steam for the shift, or for upstream stages where the shift feed gas is generated. The water can be located in tubes surrounded by or surrounding the catalyst.

[0050] F. Methanol reforming, in which a gaseous methanol stream is combined with steam and / or carbon dioxide and reacted over a catalyst at a temperature typically in the range of 250° C. to 360° C. and a pressure typically in the range of 10 bar to 30 bar (absolute) to produce a gas mixture containing hydrogen and carbon oxides. The hydrogen can be recovered from the gas mixture using conventional separation methods such as pressure swing adsorption or hydrogen permeable membranes.

[0051] The present invention will now be further described with reference to the following examples.

[0052] In the Examples, unless otherwise specified, a first precipitate was prepared on a 2- to 6-liter scale by simultaneously adding a mixed aqueous solution of a metal nitrate and an aqueous solution of an alkali metal carbonate to a stirred precipitation vessel maintained at 65°C to 70°C. The first precipitate was not aged. A second precipitate was prepared on a 0.5- to 4-liter scale by simultaneously adding a mixed aqueous solution of a metal nitrate and an aqueous solution of an alkali metal hydroxide or carbonate to a stirred precipitation vessel maintained at 65°C to 70°C. A slurry of the second precipitate was aged in a separate stirred vessel, again at 65°C to 70°C, for up to 2 hours. The first and second slurries were combined and mixed in a 3- to 8-liter vessel for up to 2 hours. Silica precursors were added by various means at different points during the preparation process. The combined precipitate slurry was filtered and washed with deionized water. Drying and calcination of the washed precipitate were performed at 110°C and 300°C, respectively, unless otherwise specified. The resulting powder was compacted into shaped units, which were then crushed into sand suitable for testing.

[0053] The silica sol used throughout the article is Snowtex-O (Nissan Chemicals). The potassium silicate used is Kasil 1 (PQ Corporation). The sodium silicate used is sodium metasilicate nonahydrate (Sigma Aldrich). Unless otherwise specified, in all cases, the weight percentage of metal oxides in the catalyst is determined on a non-destructive basis. A particularly suitable method for determining the metal oxide content on a non-destructive basis is to heat the catalyst to 900° C. in air for 2 hours to remove volatile matter before measuring the metal oxide content. The heat-treated catalyst can be stored under anhydrous conditions. The metal oxide content of the catalyst can be determined using any suitable elemental analysis technique, such as X-ray fluorescence spectroscopy (XRF) using known techniques. The copper surface area is determined using reverse head-on chromatography as follows: the catalyst pellets are crushed and sieved to a particle size of 0.6 mm to 1.00 mm. About 2.0 g of the crushed material is weighed into a stainless steel tube and heated to 68° C. and purged with helium for 2 minutes. The catalyst was then reduced by heating it at 4°C / min to a maximum of 230°C in a flow of 5% by volume H2 in helium and holding it at this temperature for 30 minutes until complete reduction. The reduced catalyst was cooled to 68°C under helium. A 2.5% by volume mixture of NO in helium was then passed over the reduced catalyst. The escaping gas was passed through a gas chromatograph, and the N2 evolution was measured. The discharged catalyst was weighed, and the copper surface area per gram of discharged catalyst was calculated therefrom.

[0054] The BET surface area on dried crushed granular sand was determined by nitrogen physical adsorption using a Micromeritics 2420ASAP physical adsorption analyzer according to ASTM method D 3663-03; Standard Test for Surface Area. Nitrogen was used as the adsorbate and the measurement was performed at liquid nitrogen temperature (77K). The cross-sectional area of ​​the nitrogen molecule was taken as Prior to analysis, the sample was degassed by purging with dry nitrogen at the optimal temperature for at least 1 hour. Five relative pressure / volume data pairs were obtained in the relative pressure region from 0.05 P / Po to 0.20 P / Po (inclusive). The equilibrium time for each point was 10 seconds.

[0055] The malachite crystal size of the dried intermediate was determined from the powder XRD patterns. The diffractograms were collected on a Bruker D8 diffractometer equipped with a 1.5-μm CMOS microscope, a Lynxeye detector, and a copper X-ray tube. Phase identification was performed using Bruker EVA v5.1.0.5 software. Crystallite size values ​​were estimated using Bruker Topas v6. Common parameters (sample displacement, scale factor, background coefficient, unit cell parameters, and peak shape) were refined using the Rietveld method. Atomic positions were fixed rather than exact. The reported crystallite size values ​​were obtained from LVol calculations based on the integral width using Lorentzian and Gaussian component convolutions.

[0056] Example 1

[0057] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 4.6:1.7:1.0:0.04 and a copper oxide content of 65.7 wt% was prepared. In a first precipitation step, a mixed metal solution containing copper and zinc nitrates was co-precipitated with a sodium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution containing aluminum and zinc nitrates, containing a silica sol, was precipitated with a sodium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, which was then aged at 65°C for up to 2 hours. The second precipitate slurry was added to the first precipitate slurry, and the mixture was aged at 70°C with stirring for up to 1.3 hours. The resulting catalyst precursor slurry was dehydrated, washed with deionized water, then dried and calcined in air at 300°C for 6 hours. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst.The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0058] Example 2

[0059] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 4.5:1.7:1.0:0.03 and a copper oxide content of 65.3 wt% was prepared. In a first precipitation step, a mixed metal solution comprising copper and zinc nitrates was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution comprising aluminum and zinc nitrates containing a silica sol was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0060] Example 3

[0061] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 4.6:1.7:1.0:0.07 and a copper oxide content of 65.3 wt% was prepared. In a first precipitation step, a mixed metal solution comprising copper and zinc nitrates was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution comprising aluminum and zinc nitrates containing a silica sol was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0062] Example 4

[0063] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 4.3:1.6:1.0:0.03 and a copper oxide content of 65.1 wt% was prepared. In a first precipitation step, a mixed metal solution comprising copper and zinc nitrates was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution comprising aluminum and zinc nitrates was precipitated with a potassium hydroxide solution containing potassium silicate at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcining steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0064] Example 5

[0065] An oxidation catalyst having a Cu:Zn:Al:Mg:Si molar ratio of 4.4:1.6:1.0:0.1:0.03 and a copper oxide content of 64.8 wt% was prepared. In a first precipitation step, a mixed metal solution containing copper, zinc, and magnesium nitrates was co-precipitated with a potassium carbonate solution containing potassium silicate at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution containing aluminum and zinc nitrates was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0066] Example 6

[0067] An oxidation catalyst having a Cu:Zn:Al:Mg:Si molar ratio of 4.3:1.6:1.0:0.2:0.04 and a copper oxide content of 63.9 wt% was prepared. In a first precipitation step, a mixed metal solution containing copper and zinc nitrates and a silica sol was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution containing aluminum and magnesium nitrates was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1.

[0068] Example 7

[0069] An oxidation catalyst having a Cu:Zn:Al:Mg:Si molar ratio of 4.3:1.6:1.0:0.2:0.04 and a copper oxide content of 64.2 wt% was prepared. In a first precipitation step, a mixed metal solution containing copper and zinc nitrates was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. A silica sol was added to the first precipitate slurry. In a second precipitation step, a mixed metal solution containing aluminum and magnesium nitrates was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, which was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1.

[0070] Example 8

[0071] An oxidation catalyst having a Cu:Zn:Al:Mg:Si molar ratio of 4.4:1.6:1.0:0.1:0.04 and a copper oxide content of 64.8 wt% was prepared. In a first precipitation step, a mixed metal solution containing nitrates of copper, zinc, and magnesium was co-precipitated with a potassium carbonate solution containing potassium silicate at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution containing nitrates of aluminum and zinc was precipitated with a potassium carbonate solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcining steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0072] Example 9

[0073] An oxidation catalyst having a Cu:Zn:Al:Mg:Si molar ratio of 4.3:1.6:1.0:0.2:0.04 and a copper oxide content of 63.9 wt% was prepared. In a first precipitation step, a mixed metal solution comprising copper and zinc nitrates was co-precipitated with a potassium carbonate solution containing potassium silicate at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution comprising aluminum, zinc, and magnesium nitrates was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcining steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0074] Example 10

[0075] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 4.6:1.7:1.0:0.03 and a copper oxide content of 65.4 wt% was prepared. In a first precipitation step, a mixed metal solution comprising copper and zinc nitrates was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution comprising aluminum and copper nitrates containing a silica sol was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 94 wt% of the total copper in the calcined catalyst. The second precipitate contained 6 wt% of the total copper in the calcined catalyst.

[0076] Example 11

[0077] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 4.6:1.7:1.0:0.03 and a copper oxide content of 65.5 wt% was prepared. A mixed metal solution comprising aluminum and zinc nitrates and a silica sol was co-precipitated with a potassium hydroxide solution at a pH of 7-7.2 and a temperature of 75°C to form a precipitate, which was aged at 65°C for 1.3 hours. The precipitate contained a total zinc oxide content of 16 wt%. The mixed metal solution comprising copper and zinc nitrates and a potassium carbonate solution were added simultaneously to the precipitate under stirring while maintaining a pH of 6.6-6.8 and a temperature of 65°C-70°C. The final co-precipitated catalyst precursor slurry was aged at 65°C-70°C for 1 hour, then dehydrated, washed with deionized water, dried, and calcined in air at 300°C for 6 hours.

[0078] Example 12

[0079] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 4.5:1.7:1.0:0.03 and a copper oxide content of 65.2 wt% was prepared. In a first precipitation step, a mixed metal solution containing copper and zinc nitrates was co-precipitated with potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution containing aluminum and zinc nitrates containing silica sol was precipitated with potassium hydroxide solution at a pH of 4.9-5.1 and a temperature of 70°C-72°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 2 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0080] Example 13

[0081] An oxidation catalyst having a Cu:Zn:Al:Mg:Si molar ratio of 4.3:1.7:1.0:0.1:0.03 and a copper oxide content of 64.0 wt% was prepared. In a first precipitation step, a mixed metal solution containing copper, zinc, and magnesium nitrates was co-precipitated with a potassium carbonate solution containing potassium silicate at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution containing aluminum and zinc nitrates was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for up to 1.5 hours. The first precipitate slurry was added to the second precipitate slurry, and the remaining aging, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 95 wt% of the total zinc in the calcined catalyst. The second precipitate contained 5 wt% of the total zinc in the calcined catalyst.

[0082] Example 14

[0083] An oxidation catalyst having a Cu:Zn:Al:Mg:Si molar ratio of 4.6:1.8:1.0:0.1:0.04 and a copper oxide content of 64.6 wt% was prepared. In a first precipitation step, a mixed metal solution comprising nitrates of copper, zinc, and magnesium was co-precipitated with a potassium carbonate solution containing potassium silicate at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution comprising nitrates of aluminum and zinc was added to a potassium hydroxide solution to form a second precipitate slurry, and the second precipitate slurry was aged at a pH of 6.5-6.8 and a temperature of 50°C for 2.5 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0084] Comparative Example 1

[0085] Following the procedure outlined in Example 5 of CN101306369, an oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 3.3:1.5:1.0:0.01 and a copper oxide content of 60.1% by weight was prepared by co-precipitating an aluminum nitrate solution with a solution of sodium carbonate and sodium silicate at a pH of 7-7.2 and a temperature of 80°C, and aging the precipitate at 65°C for 40 minutes to form an alumina-silica slurry. Separately, a mixed metal solution containing copper and zinc nitrates was co-precipitated with a sodium carbonate solution at a pH of 7.0-7.2 and a temperature between 65°C and 70°C to form a Cu-Zn basic carbonate slurry. The alumina-silica slurry was added to the Cu-Zn basic carbonate slurry in a volume ratio of 1:7, and the mixture was aged at 70°C with stirring for 2 hours. The slurry was dehydrated, washed with deionized water, then dried and calcined in air at 340°C for 4 hours.

[0086] Comparative Example 2

[0087] An oxidation catalyst having a Cu:Zn:Al:Si molar ratio of 5.8:2.0:1.0:0.03 and a copper oxide content of 68.1% by weight was prepared. In a first precipitation step, a mixed metal solution containing copper and zinc nitrates was co-precipitated with a sodium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, an aluminum nitrate solution was precipitated with a sodium hydroxide solution containing sodium silicate at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, which was then aged at 65°C for up to 2 hours. The second precipitate slurry was added to the first precipitate slurry, and the mixture was aged at 70°C with stirring for up to 2 hours. The slurry was dehydrated, washed with deionized water, then dried and calcined in air at 300°C for 6 hours.

[0088] Comparative Example 3

[0089] An oxidation catalyst with a Cu:Zn:Al:Si molar ratio of 3.8:2.2:1.0:0.04 and a copper oxide content of 56.6% by weight was prepared following the procedure outlined in Example 2 of US Pat. A mixed metal nitrate solution containing copper, zinc, and aluminum nitrates, a silica sol, and a sodium carbonate solution were simultaneously added to deionized water in a stirred vessel at room temperature. The resulting precipitate was aged at room temperature for 24 hours, dehydrated, washed with deionized water, dried, and calcined in air at 600°C for 2 hours.

[0090] Comparative Example 4

[0091] An oxidation catalyst having a Cu:Zn:Al molar ratio of 4.3:1.6:1.0 and a copper oxide content of 65.2 wt% was prepared. In a first precipitation step, a mixed metal solution comprising copper and zinc nitrates was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution comprising aluminum and zinc nitrates was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry, and the second precipitate slurry was aged at 65°C for 1.5 hours. The remaining mixing, drying, and calcination steps were performed according to the method of Example 1. The first precipitate contained 84 wt% of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0092] Comparative Example 5

[0093] An oxidation catalyst was prepared with a Cu:Zn:Al:Si molar ratio of 4.4:1.6:1.0:0.18 and a copper oxide content of 64.1% by weight. In a first precipitation step, a mixed metal solution containing copper and zinc nitrates was co-precipitated with a potassium carbonate solution at a pH of 6.4-6.7 and a temperature of 65°C to form a first precipitate slurry. In a second precipitation step, a mixed metal solution containing aluminum and zinc nitrates, containing a silica sol, was precipitated with a potassium hydroxide solution at a pH of 7.0-7.2 and a temperature of 75°C to form a second precipitate slurry. The second precipitate slurry was aged at 65°C for 2 hours. The second precipitate slurry was added to the first precipitate slurry, and the mixture was aged at 70°C with stirring for up to 45 minutes. The slurry was dewatered, washed with deionized water, then dried and calcined in air at 300°C for 6 hours. The first precipitate contained 84% by weight of the total zinc in the calcined catalyst. The second precipitate contained 16 wt% of the total zinc in the calcined catalyst.

[0094] The catalyst characteristics are as follows:

[0095]

[0096]

[0097] Microreactor testing

[0098] Each catalyst sample was crushed and sieved to a particle size of 0.6 mm to 1.0 mm. A conventional microreactor was used in the experiment. The crushed catalyst samples were fully reduced at 225°C in nitrogen with a gas mixture of 2% vol / vol hydrogen. A process gas mixture consisting of 6% vol / vol CO, 6% vol / vol CO2, 9% vol / vol N2, and 79% vol / vol H2 was then introduced above the catalyst samples. This process gas mixture represents synthesis gas produced by natural gas reforming. The reduced catalyst samples were exposed to the process gas mixture at 225°C, 40,000 L / h / kg, and 50 bar (gauge pressure) at the beginning of their life. After a period of time, the catalyst samples were exposed to deactivation conditions exceeding 300°C to simulate harsh operating conditions and accelerate the deactivation effects. Analytical flow scans of the product gas were performed at the beginning of their life and after the catalyst had been maintained under deactivation conditions. The analytical flow scans were performed by varying the mass velocity at 225°C and 50 bar (gauge pressure). An infrared analyzer was used to determine the % volume / volume concentration of the outlet gas stream from the reactor. The analytical flow scan data was used to calculate the relative activity of the test materials and the reference catalyst, which was selected as Comparative Example 1 in these experiments. The relative activity was calculated by the ratio of the flow rate through each catalyst relative to the flow rate through the standard catalyst at a constant conversion rate. The results are shown in the following table:

[0099]

[0100]

[0101] Test results show that compared to catalysts prepared using existing methods (Comparative Examples 1 and 3), the catalyst prepared using the method of the present invention exhibits higher initial activity and higher retained activity after a period of high-temperature deactivation under methanol synthesis conditions. This is attributed to the small malachite crystallite size, optimized support phase, and the stabilizing effect of silica.

[0102] Comparative Example 2 illustrates the requirement to include a second metal in a second precipitation with aluminum. Comparative Example 4 illustrates that a formulation without silica has poorer long-term activity compared to a formulation containing Si. Comparative Example 5 shows that higher silica loadings can be detrimental to long-term catalyst performance.

[0103] In addition to the above tests conducted with conventional synthesis gas, the catalyst of Example 5 was subjected to further microreactor testing to evaluate its performance under conditions suitable for CO2 hydrogenation. In this case, after reduction as described above, the sample was initially exposed to a process gas mixture consisting of 16% v / v CO2, 2% v / v CO, 10% v / v N2, and 72% v / v H2 at 225°C, 70,000 L / hr / kg, and 50 barg. After a period of time, the sample was exposed to deactivation conditions exceeding 265°C to simulate harsh operation and accelerate deactivation. As in the previous tests, flow scans were performed periodically throughout the run under milder conditions to monitor the residual activity of the sample. The results obtained are shown in the table below, again using Comparative Example 1 as the reference catalyst:

[0104]

[0105] These test results again show that compared with the catalyst prepared by the existing method, the catalyst prepared by the method of the present invention has higher initial activity and higher retained activity after a period of high temperature deactivation under the conditions of CO2 hydrogenation to methanol.

Claims

1. A method for preparing a copper-containing catalyst, comprising the following steps: (a) mixing an acidic copper-containing solution with a first alkaline precipitant solution in a first precipitation step to form a first precipitate, (b) mixing an acidic aluminum-containing solution with a second alkaline precipitant solution in a second precipitation step to form a second precipitate, the acidic aluminum-containing solution further comprising one or more metal compounds selected from copper compounds, zinc compounds and promoter metal compounds selected from compounds of Mg, Co, Mn, V, Ti, Zr or rare earths, (c) contacting the first precipitate and the second precipitate together in a further mixing step to form a catalyst precursor, and (d) washing, drying and calcining the catalyst precursor to form the copper-containing catalyst, wherein a silica precursor is included in the first precipitation step, the second precipitation step or the precipitate mixing step to provide a catalyst having a silica content expressed as SiO2 in the range of 0.1% to 5.0% by weight.

2. The method according to claim 1, wherein the first precipitation step is performed by mixing an acidic copper-containing aqueous solution containing a copper compound and a zinc compound with an alkali metal carbonate aqueous solution in a first precipitation vessel.

3. The method of claim 2, wherein the copper compound and the zinc compound are nitrates, and the alkaline precipitant comprises sodium carbonate or potassium carbonate.

4. The method of claim 1, wherein a copper compound is included in both the first precipitation step and the second precipitation step, and the amount of copper in the second precipitation step is in the range of 0.5% to 20% of the total copper added.

5. The method of claim 1, wherein a zinc compound is included in both the first precipitation step and the second precipitation step, and the amount of zinc in the second precipitation step is in the range of 0.5% to 50% of the total zinc added.

6. The method according to claim 1, wherein one or more promoter compounds selected from compounds of Mg are contained in the acidic copper-containing solution in the first precipitation step and / or in the acidic aluminum-containing solution in the second precipitation step.

7. The method of claim 1, wherein the first precipitation step is performed at a temperature in the range of 40°C to 80°C and a pH in the range of 6-8.

8. The method according to claim 1, wherein the second precipitation step is performed by mixing an aqueous solution containing aluminum nitrate and one or more metal nitrates selected from copper nitrate, zinc nitrate and promoter metal nitrates with an aqueous alkali metal hydroxide solution.

9. The method of claim 1, wherein the second precipitation step is performed at a temperature in the range of 10°C to 80°C and a pH in the range of 5-9.

10. The method of claim 1, wherein the second precipitate formed in step (b) and / or the mixed precipitate in step (c) are aged at a temperature in the range of 10°C to 80°C.

11. The method according to claim 1, wherein step (a) is performed before or after step (b), or step (a) and step (b) are performed simultaneously.

12. The method of claim 1, wherein the precipitates from step (a) and step (b) are not separated and washed before the mixing step (c).

13. The method of claim 1, wherein in step (c), slurries of the first precipitate and the second precipitate are mixed in a mixing vessel.

14. The method of claim 1, wherein step (c) is performed simultaneously with step (a) or step (b).

15. The process according to claim 1, wherein the catalyst has a silicon dioxide content expressed as SiO2 in the range of 0.1% to 3.0% by weight.

16. The method of claim 1, wherein the silica precursor is colloidal silica or silica sol, a water-soluble silicon compound, an alkali metal silicate, or an organic silicate.

17. The method of claim 1, wherein the acidic copper-containing solution in the first precipitation step, the acidic aluminum-containing solution in the second precipitation step, the first precipitate, the second precipitate, or a mixture of the first and second precipitates in the precipitate mixing step comprises acidic silica sol.

18. The method of claim 1, wherein the first alkaline precipitant solution in the first precipitation step, the second alkaline precipitant solution in the second precipitation step, the first precipitate, the second precipitate, or a mixture of the first and second precipitates in the precipitate mixing step comprises an alkali metal silicate or an alkaline silica sol.

19. The method of claim 1, wherein the drying is performed at a temperature in the range of 90°C to 150°C.

20. The method of claim 1, wherein the calcining is performed at a temperature in the range of 250°C to 500°C.

21. The method of claim 1, wherein the dried or calcined catalyst precursor is shaped by pelletizing.

22. The method of claim 1, wherein one or more zinc compounds are included in the first and second precipitates, and the weight ratio of Cu:Zn expressed as CuO:ZnO in the calcined catalyst is 1:1 or higher.

23. The process of claim 1 , wherein the calcined catalyst comprises 30 to 70 wt% of copper expressed as CuO, 15 to 50 wt% of Zn expressed as ZnO, 5 to 40 wt% of aluminum oxide expressed as Al 2 O 3 , 0 to 5 wt% of magnesium oxide expressed as MgO, and 0.1 to 2.0 wt% of Si expressed as SiO 2 .

24. The process of claim 1 , wherein the calcined catalyst comprises 50 to 68 weight % of copper expressed as CuO, 20 to 35 weight % of Zn expressed as ZnO, 6 to 20 weight % of aluminum oxide expressed as Al 2 O 3 , 0 to 5 weight % of magnesium oxide expressed as MgO, and 0.20 to 1.0 weight % of Si expressed as SiO 2 .

25. A catalyst obtainable by the method according to claim 1.

26. A process selected from methanol synthesis, methanol reforming and water gas shift, the process using the catalyst according to claim 25 or the catalyst prepared by the process according to claim 1.

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