Methanol synthesis catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of methanol synthesis catalysts, and particularly relates to a methanol synthesis catalyst and a preparation method and application thereof. The preparation method comprises the following steps: (1) carrying out a first precipitation reaction on an Al source and a first precipitant containing no alkali metal to obtain a first turbid liquid, and filtering and washing the first turbid liquid to obtain a first precipitate; (2) carrying out a co-precipitation reaction on a Cu source, a Zn source and a second precipitator to obtain a second turbid liquid, then carrying out aging treatment, and then filtering and washing to obtain a second precipitate; (3) mixing the first precipitate and the second precipitate, adding water, and filtering, drying and roasting the mixture to obtain a catalyst; the first precipitator is selected from at least one of ammonia water, ammonium salt and urea; the second precipitator is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate. The specific surface area, the catalytic activity and the thermal stability of the catalyst can be improved, and meanwhile, the water consumption for washing can be greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of methanol synthesis catalysts, and in particular relates to a methanol synthesis catalyst and a preparation method and application thereof. Background Art

[0002] In the industrial production of copper-zinc-aluminum methanol synthesis catalysts, carbonates containing alkali metals are generally used as precipitants (such as sodium carbonate, sodium bicarbonate, potassium carbonate, etc.), which will result in a certain amount of alkali metal ions remaining in the copper-based methanol synthesis catalysts currently in wide use. The presence of alkali metals will lead to the growth of CuO and ZnO grains in the methanol synthesis catalyst, reduce the specific surface area of ​​the catalyst and the dispersion of copper, and thus affect the thermal stability of the catalyst.

[0003] Patent document CN104549300A discloses a method for preparing a low-sodium copper-based methanol synthesis catalyst, in which a low-sodium copper-zinc matrix is ​​obtained by precipitation and washing, and then an alumina carrier is directly added to obtain a catalyst sample. In this method, the operation mode of directly mixing the copper-zinc matrix with the alumina carrier will weaken the interaction between the aluminum element and the copper-zinc matrix, which will have an adverse effect on the performance of the catalyst.

[0004] Patent document CN104174404A discloses a method for preparing a methanol synthesis catalyst, wherein a precursor precipitant is mixed with a copper-zinc solution to prepare a precursor, and Al(NO) 3 The solution is neutralized with ammonia water to prepare a carrier, and the obtained matrix and the carrier are evenly mixed, filtered and washed to obtain a catalyst sample; in this preparation method, the matrix and the carrier are mixed and then filtered and washed, which may cause the alkali metal in the matrix to be doped into the aluminum-containing carrier, increase the amount of washing water or increase the sodium content in the catalyst, increase the process complexity and cost and also have an adverse effect on the performance of the catalyst.

[0005] Patent document CN105268442A discloses a method for preparing a copper-based methanol synthesis catalyst, which comprises mixing a copper-zinc mixed solution with a double precipitant buffer to obtain a copper-zinc suspension, mixing an aluminum solution with ammonia water to obtain a carrier suspension, and then mixing the copper-zinc suspension with the carrier suspension to obtain a catalyst sample through washing and filtering. This method uses ammonia water to prepare an aluminum-containing carrier, which can reduce the alkali metal content in the precipitate, but is subsequently directly mixed with a copper-zinc matrix containing alkali metal ions, resulting in the alkali metal ions brought into the matrix being doped into the aluminum-containing carrier, increasing the difficulty of washing, resulting in an increase in the amount of water used for washing and an increase in the sodium content of the catalyst, which also leads to increased process complexity and cost and will also have an adverse effect on the performance of the catalyst.

[0006] In view of this, further research and improvement of the precipitation method for preparing copper-zinc-aluminum methanol synthesis catalyst is a direction worthy of study. Summary of the invention

[0007] In view of the technical defects mentioned above, the purpose of the present invention is to provide a methanol synthesis catalyst and a preparation method and application thereof; an aluminum-containing carrier is prepared by reacting a precipitant that does not contain alkali metals with a solution containing aluminum salts, and the copper-zinc matrix is ​​mixed with the aluminum-containing carrier after washing, which can effectively avoid the doping of the aluminum-containing carrier with alkali metals, which is beneficial to further reduce the sodium content of the catalyst, improve the catalytic performance and thermal stability of the catalyst, and at the same time reduce the water consumption in the washing process, and have higher economic and environmental benefits.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] In a first aspect, a method for preparing a methanol synthesis catalyst is provided, the preparation method comprising the following steps:

[0010] (1) contacting an Al source with a first precipitant not containing an alkali metal and performing a first precipitation reaction to obtain a first suspension, which is then subjected to an aging treatment, and the obtained product is filtered and washed to obtain a first precipitate;

[0011] (2) contacting a Cu source, a Zn source and a second precipitant to perform a coprecipitation reaction to obtain a second suspension, which is then subjected to an aging treatment, and the obtained product is filtered and washed to obtain a second precipitate;

[0012] (3) mixing the first precipitate and the second precipitate, adding deionized water thereto, stirring the mixture evenly, filtering the obtained mixture, and drying and calcining the obtained filter residue in sequence to obtain the methanol synthesis catalyst;

[0013] Wherein, the first precipitant and the second precipitant are different; the first precipitant is selected from one or more of ammonia water, ammonium salt and urea; the second precipitant is selected from one or more of sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate.

[0014] According to the preparation method of the present invention, in some embodiments, the Al source is a water-soluble compound containing Al element, preferably selected from Al(NO 3 ) 3 、Al 2 (SO 4 ) 3 and AlCl 3 At least one of .

[0015] In some embodiments, the Cu source is a water-soluble compound containing the Cu element, preferably selected from Cu(NO 3 ) 2 ,CuSO 4 and CuCl2 At least one of .

[0016] In some embodiments, the Zn source is a water-soluble compound containing Zn element, preferably selected from Zn(NO 3 ) 2 、ZnSO 4 and ZnCl 2 At least one of .

[0017] In some embodiments, in step (1), the conditions of the first precipitation reaction include: the reaction temperature is 70-90°C (for example, 72°C, 74°C, 75°C, 78°C, 82°C, 85°C), preferably 70-80°C; the system pH is 5-10 (for example, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5), preferably 6-8.

[0018] The present invention selects to carry out the first precipitation reaction at a relatively high temperature, thereby obtaining an amorphous aluminum-containing colloid, the aluminum element has a higher degree of freedom, and is more evenly dispersed, which helps to promote the interaction between the aluminum element and the copper-zinc active components in the aluminum-containing precipitate.

[0019] In the present invention, the reaction time of the first precipitation reaction can be adjusted according to the amount of the reaction raw materials used. Generally, when the amount of the reaction raw materials used is large, the reaction time can be appropriately extended.

[0020] In step (1), the Al source and the first precipitant are dripped into the co-precipitation container, and the endpoint pH value of the mixture I in the system is, for example, in the range of 6 to 8. The mixture I should be understood as a mixture of the Al source and the first precipitant.

[0021] In step (1), the conditions for performing an aging reaction after the precipitation reaction include: an aging temperature of 70-90°C (for example, 72°C, 74°C, 75°C, 78°C, 82°C, 85°C), preferably 70-80°C; an aging time of 0.5-6h (for example, 1h, 1.5h, 2h, 3h, 4h, 5h, 5.5h), preferably 1-2.5h.

[0022] In some embodiments, in step (2), the conditions of the coprecipitation reaction include: the reaction temperature is 40-90°C (for example, 45°C, 50°C, 55°C, 65°C, 70°C, 85°C), preferably 60-80°C; the system pH is 5-10 (for example, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5), preferably 6-8.

[0023] In the present invention, the reaction time of the coprecipitation reaction can be adjusted according to the amount of the reaction raw materials used. Generally, when the amount of the reaction raw materials used is large, the reaction time can be appropriately extended.

[0024] In step (2), during the dropwise addition of the Cu source, Zn source and the second precipitant, it is necessary to ensure that the pH of the mixture II in the system is, for example, 6 to 8. The "mixture II" refers to the mixture of the Cu source, the Zn source and the second precipitant.

[0025] In some embodiments, in step (2), the conditions for performing an aging reaction after the coprecipitation reaction include: an aging temperature of 40-90°C (e.g., 50°C, 60°C, 75°C, 80°C, 85°C), preferably 70-90°C; an aging time of 1-12h (e.g., 1.5h, 3h, 3.5h, 5h, 8h, 10h), preferably 2-4h.

[0026] In the preparation method of the present invention, aluminum and copper-zinc elements are precipitated in steps, aluminum precipitation and copper-zinc precipitation are performed separately, and the precipitates are washed in the process, and the washing is completed before the two precipitates are mixed, which can avoid the mutual doping of impurity ions in the two precipitates, thereby avoiding the problem of washing difficulties caused by impurity doping.

[0027] In some embodiments, in step (1), the product obtained by aging treatment is filtered and washed, and the washing condition is: the conductivity of the washing filtrate finally obtained is less than or equal to 1000 μs / cm.

[0028] In some embodiments, in step (2), the product obtained by the aging treatment is filtered and washed, and the washing condition is: the conductivity of the washing filtrate finally obtained is less than or equal to 100 μs / cm.

[0029] In some embodiments, in step (3), the drying conditions include: a drying temperature of 90-120°C (e.g., 95°C, 100°C, 110°C, 115°C), and a drying time of 6-18h (e.g., 8h, 10h, 12h, 15h).

[0030] In some embodiments, in step (3), the calcination conditions include: a calcination temperature of 300-390°C (e.g., 310°C, 320°C, 350°C, 360°C, 380°C), and a calcination time of 2-18h (e.g., 3h, 4h, 5h, 8h, 10h, 12h, 15h).

[0031] In some embodiments, the molar ratio of the Cu source, Zn source and Al source, calculated on an element basis, is (40-65):(20-40):(3-30), for example, 40:40:20, 50:40:10, 60:30:10, 60:20:20, 50:30:20, 50:35:15, 60:35:5, 65:30:5, and preferably (45-65):(20-35):(8-20).

[0032] In a second aspect, a methanol synthesis catalyst prepared by the preparation method as described above is provided, wherein the methanol synthesis catalyst comprises the following components in the following amounts, based on the total weight of the methanol synthesis catalyst:

[0033] Al 2 O 3 1.5wt%-25wt% (e.g., 2wt%, 4wt%, 5wt%, 6wt%, 8wt%, 10wt%, 15wt%, 18wt%, 20wt%, 22wt%) of aluminum component, preferably 1.93wt%-21.44wt%,

[0034] 40wt%-70wt% (e.g., 43wt%, 45wt%, 50wt%, 55wt%, 60wt%, 62wt%, 65wt%) of copper component, preferably 42.67wt%-68.37wt%, based on CuO,

[0035] Calculated as ZnO, the zinc component is 20wt%-45wt% (e.g., 23wt%, 24wt%, 25wt%, 30wt%, 35wt%, 40wt%, 42wt%), preferably 21.94wt%-43.66wt%.

[0036] In a third aspect, a methanol synthesis catalyst prepared by the preparation method described above or use of the methanol synthesis catalyst described above in catalytic synthesis of methanol is provided.

[0037] The application process of the methanol synthesis catalyst in the catalytic synthesis of methanol can be achieved by conventional means in the art, which will not be described in detail here.

[0038] In the process of preparing copper-zinc-aluminum methanol synthesis catalyst by precipitation method in this field, a part of soluble impurities (such as alkali metal ions) are often brought into the precipitate. The main reasons for the introduction of impurities into the precipitate are: surface adsorption, formation of mixed crystals, mechanical occlusion and inclusion, among which surface adsorption is the main factor. Surface adsorption is related to the specific surface area of ​​the precipitate. The larger the specific surface area of ​​the precipitate, the stronger the ability of surface adsorption to introduce impurities. The inventors found that during the precipitation process, aluminum elements generally form amorphous phase precipitation with a larger specific surface area, while copper and zinc elements form crystalline phase precipitation with a relatively small specific surface area; therefore, the surface adsorption amount of the aluminum-containing carrier is large. If the precipitate is doped with sodium, it will be difficult to remove, and the water consumption will increase significantly.

[0039] The present invention firstly adopts a step-by-step precipitation process to precipitate aluminum and copper and zinc elements respectively, and simultaneously adopts a first precipitant (such as ammonia water, ammonium salt, etc.) that does not contain alkali metals to carry out neutralization reaction with an aluminum solution to prepare an aluminum-containing carrier, and after the copper-zinc co-precipitate is washed, it is mixed with the precipitated aluminum-containing carrier, thereby effectively avoiding the doping of the aluminum-containing carrier by the alkali metals that may be entrained, and the obtained methanol synthesis catalyst has a low sodium content, and the obtained catalyst has a higher specific surface area, better activity and thermal stability; in addition, the preparation process can greatly reduce the amount of washing water, and has higher environmental and economic benefits.

[0040] Compared with the existing technology, the preparation method discovered in the present invention is beneficial to reducing the sodium content in the copper-zinc-aluminum methanol synthesis catalyst, thereby improving the specific surface area, activity and thermal stability of the catalyst, while significantly reducing the water consumption in the washing process, thus having higher economic and environmental benefits. DETAILED DESCRIPTION

[0041] In order to understand the technical features and contents of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described here.

[0042] Unless otherwise specified, the experimental procedures used in the following examples are all conventional methods.

[0043] The materials, reagents, etc. used in the following examples can all be obtained from commercial sources.

[0044] Embodiment 1:

[0045] The raw materials used are Cu(NO 3 ) 2 ·3H 2 O、Zn(NO 3 ) 2 6H 2 O、Al(NO 3 ) 3 9H 2 O、NH 3 ·H 2 O and Na 2 CO 3 , prepare 1 mol / L copper-zinc salt mixed salt solution, 1 mol / L aluminum salt solution, and 1 mol / L NH 3 ·H 2 O solution (first precipitant) and Na 2 CO 3 Aqueous solution (second precipitant).

[0046] The preparation method of the methanol synthesis catalyst comprises the following steps:

[0047] (1) First, use a peristaltic pump to mix the aluminum salt solution prepared above with the first precipitant NH 3 ·H 2 O solution was added dropwise to the water bath flask, and the water bath temperature was controlled at 70°C. The dropping process was accompanied by stirring. The dropping speed of the first precipitant was adjusted to control the mixture I (i.e., the aluminum salt solution and NH 3 ·H 2 O solution) has an endpoint pH value of 8 to obtain a first suspension, which is aged at 70° C. for 1 h, and the obtained product is filtered and washed until the conductivity of the filtrate is less than 1000 μs / cm to obtain a first precipitate;

[0048] (2) Use a peristaltic pump to mix the copper-zinc salt mixed solution prepared above with the second precipitant Na 2 CO 3 The aqueous solution was added dropwise to a water bath flask at a temperature of 70°C. The addition process was accompanied by stirring. The addition rate of the second precipitant was adjusted to control the mixture II (copper-zinc salt mixed salt solution and Na 2 CO 3 The end point pH value of the mixture of the aqueous solution is 7 to obtain a second suspension; aging the suspension at 80° C. for 2 hours, and then filtering and washing the aging product until the conductivity of the filtrate is less than 100 μs / cm to obtain a second precipitate;

[0049] (3) mixing the first precipitate and the second precipitate prepared as above, adding deionized water thereto and mixing them evenly, stirring for 0.5 h and filtering the mixture; wherein the molar ratio of Cu and Zn contained in the copper-zinc salt mixed salt solution and Al contained in the aluminum salt solution is 60:30:10;

[0050] The filtered residue was dried at 110°C for 12 hours, and then calcined at 350°C for 4 hours. The obtained product was tableted, crushed, and sieved to obtain catalyst particles of 60-100 meshes.

[0051] Embodiment 2:

[0052] The raw material Cu(NO 3 ) 2 ·3H 2 O、Zn(NO 3 ) 2 6H 2 O、Al(NO 3 ) 3 9H 2 O、NH 3 ·H 2O、Na 2 CO 3 and NaHCO 3 Prepare 1 mol / L copper-zinc salt solution, 1 mol / L aluminum salt solution, and 1 mol / L (NH 4 ) 2 CO 3 aqueous solution (first precipitant) and Na 2 CO 3 With NaHCO 3 A mixed aqueous solution (second precipitant).

[0053] The preparation method of the methanol synthesis catalyst comprises the following steps:

[0054] (1) First, use a peristaltic pump to mix the aluminum salt solution prepared above with the first precipitant (NH 4 ) 2 CO 3 The aqueous solution was dripped into the water bath flask in parallel, and the water bath temperature was controlled to be 80°C. The dripping process was accompanied by stirring. The dripping speed of the first precipitant was adjusted to control the mixture I (i.e., the aluminum salt solution and (NH 4 ) 2 CO 3 The end point pH value of the mixture of the aqueous solution is 7 to obtain a first suspension, which is aged at 80° C. for 1 hour, and the obtained product is filtered and washed until the conductivity of the filtrate is less than 1000 μs / cm to obtain a first precipitate;

[0055] (2) Use a peristaltic pump to mix the copper-zinc salt mixed solution prepared above with the second precipitant (Na 2 CO 3 With NaHCO 3 The mixed aqueous solution of the copper-zinc salt mixture and the second precipitant) is added dropwise to a water bath flask, the water bath temperature is controlled to be 60°C, stirring is accompanied during the dropping process, and the endpoint pH value of the mixture II (the mixture of the copper-zinc salt mixed salt solution and the second precipitant) is controlled to be 8 by adjusting the dropping speed of the second precipitant to obtain a second suspension; the suspension is aged at 70°C for 2 hours, and then the aged product is filtered and washed until the conductivity of the filtrate is less than 100 μs / cm to obtain a second precipitate;

[0056] (3) mixing the first precipitate and the second precipitate prepared as above, adding deionized water thereto and mixing them evenly, stirring for 0.5 h and filtering the mixture; wherein the molar ratio of Cu and Zn contained in the copper-zinc salt mixed salt solution and Al contained in the aluminum salt solution is 57:28:15;

[0057] The filtered residue was dried at 100°C for 8 hours and then calcined at 320°C for 6 hours. The obtained product was tableted, crushed and sieved to obtain catalyst particles of 60-100 meshes.

[0058] Embodiment 3:

[0059] The preparation method of the methanol synthesis catalyst is similar to that of Example 1, except that: during the first precipitation reaction in step (1), the water bath temperature is controlled to be 90° C., the dropping process is accompanied by stirring, and the dropping speed of the first precipitant is adjusted to control the mixture I (i.e., the aluminum salt solution and NH 3 ·H 2 The endpoint pH of the mixture of the two solutions was 8.

[0060] The remaining steps are the same as those in Example 1; and finally catalyst particles of 60-100 mesh are obtained.

[0061] Embodiment 4:

[0062] The preparation method of the methanol synthesis catalyst is similar to that of Example 1, except that in step (3), the molar ratio of Cu, Zn contained in the copper-zinc salt mixed salt solution and Al contained in the aluminum salt solution is 45:25:30.

[0063] The remaining steps are the same as those in Example 1; and finally catalyst particles of 60-100 mesh are obtained.

[0064] Comparative Example 1:

[0065] The raw materials used are Cu(NO 3 ) 2 ·3H 2 O、Zn(NO 3 ) 2 6H 2 O、Al(NO 3 ) 3 9H 2 O、Na 2 CO 3 and NaHCO 3 , prepare 1 mol / L copper-zinc salt mixed salt solution, 1 mol / L aluminum salt solution and 1 mol / L Na 2 CO 3 aqueous solution (first precipitant) and Na 2 CO 3 With NaHCO 3 A mixed aqueous solution (second precipitant).

[0066] The preparation method of the catalyst comprises the following steps:

[0067] (1) First, use a peristaltic pump to mix the aluminum salt solution prepared above with the first precipitant (Na 2 CO 3 The mixture I (i.e., the aluminum salt solution and the Na solution) was added dropwise to the water bath flask, the water bath temperature was controlled to be 80°C, the addition process was accompanied by stirring, and the addition rate of the first precipitant was adjusted to control the mixture I (i.e., the aluminum salt solution and the Na 2 CO 3 The endpoint pH value of the mixture of the aqueous solution is stabilized at about 7 to obtain a first suspension, which is aged at 80° C. for 1 hour, and the obtained product is filtered and washed until the conductivity of the filtrate is less than 1000 μs / cm to obtain a first precipitate;

[0068] (2) Use a peristaltic pump to mix the copper-zinc salt mixed solution prepared above with the second precipitant (Na 2 CO 3 With NaHCO 3 The mixed aqueous solution of the copper-zinc salt mixture and the second precipitant) is added dropwise to a water bath flask, the water bath temperature is controlled to be 60°C, the dropping process is accompanied by stirring, and the endpoint pH value of the mixture II (the mixture of the copper-zinc salt mixed salt solution and the second precipitant) is controlled to be 8 by adjusting the dropping speed of the second precipitant to obtain a second suspension; the suspension is aged at 70°C for 2 hours, and then the aged product is filtered and washed until the conductivity of the filtrate is less than 100 μs / cm to obtain a second precipitate;

[0069] (3) mixing the first precipitate and the second precipitate prepared as above, adding deionized water thereto and mixing them evenly, stirring for 0.5 h and filtering the mixture; wherein the molar ratio of Cu and Zn contained in the copper-zinc salt mixed salt solution and Al contained in the aluminum salt solution is 57:28:15;

[0070] The filtered residue was dried at 100°C for 8 hours and then calcined at 320°C for 6 hours. The obtained product was tableted, crushed and sieved to obtain catalyst particles of 60-100 meshes.

[0071] Comparative Example 2:

[0072] The raw materials used are Cu(NO 3 ) 2 ·3H 2 O、Zn(NO 3 ) 2 6H 2 O、Al(NO 3 ) 3 9H 2 O、NH 3 ·H 2 O and Na 2 CO 3, prepare 1 mol / L copper-zinc salt mixed salt solution, 1 mol / L aluminum salt solution, and 1 mol / L NH 3 ·H 2 O solution (first precipitant) and Na 2 CO 3 Aqueous solution (second precipitant).

[0073] The preparation method of the methanol synthesis catalyst comprises the following steps:

[0074] (1) First, use a peristaltic pump to mix the aluminum salt solution prepared above with the first precipitant NH 3 ·H 2 O solution was added dropwise to the water bath flask, and the water bath temperature was controlled at 70°C. The dropping process was accompanied by stirring. The dropping speed of the first precipitant was adjusted to control the mixture I (i.e., the aluminum salt solution and NH 3 ·H 2 The endpoint pH value of the mixture of the above-mentioned solutions (the above-mentioned mixture) is 8, and the first suspension is obtained;

[0075] (2) Add the prepared copper-zinc salt mixed salt solution and the second precipitant Na 2 CO 3 The aqueous solution is dripped into a water bath flask in parallel, the water bath temperature is controlled to be 70° C., the dripping process is accompanied by stirring, and the endpoint pH value of the mixture II (a mixture of the first suspension, the copper-zinc salt mixed salt solution and the second precipitant) is controlled to be 7.0 by adjusting the dripping speed of the second precipitant to obtain a second suspension; wherein the molar ratio of Cu and Zn contained in the copper-zinc salt mixed salt solution to Al contained in the aluminum salt solution is 60:30:10;

[0076] (3) The second suspension prepared as above was aged at 70°C for 2 h, and the aged product was filtered and washed until the conductivity of the filtrate was less than 100 μs / cm. The filter residue was dried at 110°C for 12 h, and then calcined at 350°C for 4 h. The product was then tableted, crushed, and sieved to obtain catalyst particles of 60-100 mesh.

[0077] Comparative Example 3:

[0078] The preparation method of the methanol synthesis catalyst is similar to that of Example 1, except that in step (1), the temperature of the first precipitation reaction is 60°C.

[0079] The remaining steps are the same as those in Example 1, and finally catalyst particles of 60-100 mesh are obtained.

[0080] Comparative Example 4:

[0081] The preparation method of the methanol synthesis catalyst refers to Example 1, except that in step (2), the second precipitant is replaced by a sodium oxalate aqueous solution.

[0082] The remaining steps are the same as those in Example 1, and finally catalyst particles of 60-100 mesh are obtained.

[0083] The specific surface area of ​​the catalyst samples prepared in each embodiment and comparative example was analyzed at -196°C using a Micromeritics Tristar 3020 analyzer; before testing, the catalyst powder samples prepared in each embodiment and comparative example were degassed at 300°C for 6 hours. The sodium content of the catalyst samples prepared in each embodiment and comparative example was analyzed using a Spectro Arcos inductively coupled plasma emission spectrometer. The composition of the catalyst prepared in each embodiment is shown in Table 1; the test results of the performance parameters such as the specific surface area and sodium content of the catalyst are shown in Table 2.

[0084] Table 1 Composition of the catalysts prepared in each embodiment and comparative example

[0085] serial number <![CDATA[Al 2 O 3 Content (wt%)]]> CuO content (wt%) ZnO content (wt%) Example 1 6.60 61.79 31.61 Example 2 10.09 59.84 30.07 Example 3 6.60 61.79 31.61 Example 4 21.41 50.11 28.48 Comparative Example 1 10.09 59.84 30.07 Comparative Example 2 6.60 61.79 31.61 Comparative Example 3 6.60 61.79 31.61 Comparative Example 4 6.60 61.79 31.61

[0086] Table 2 Performance parameter test results of the catalysts prepared in each embodiment

[0087] Example 1 Example 2 Example 3 Example 4 Sodium content (mg / kg) 73.84 86.53 65.98 71.22 Washing water volume (ml / g) 85 80 85 70 <![CDATA[Specific surface area (m 3 / g)]]> 120.31 135.58 111.31 186.55

[0088] Table 3 Performance parameter test results of the catalysts prepared in each comparative example

[0089]

[0090]

[0091] As can be seen from Table 2-3, by using the method of the present invention, impurities are easy to wash during the catalyst preparation process, the residual sodium content in the obtained catalyst is low, and the amount of washing water is small; at the same time, due to the low sodium content in the catalyst, its specific surface area is also improved. However, the catalysts prepared in Comparative Examples 1 and 2 have relatively high sodium content in the catalyst, resulting in a low specific surface area. In Comparative Examples 3 and 4, although the sodium content and the amount of washing water are similar to those in Example 1, the specific area of ​​the obtained catalyst is reduced due to the use of a first precipitation reaction temperature and a second precipitant type different from those in the example.

[0092] Catalyst performance evaluation

[0093] The evaluation experiment uses a 16-channel micro multi-tube combined reaction device produced by HTE of Germany to evaluate the performance of the catalyst. The device evenly divides one channel of raw gas into 16 channels through a capillary splitting system and distributes them to 16 tubular reactors. The raw gas flow rate in each reaction tube is the same, and the components have good consistency; the experimental pressure is 4MPa, the reaction temperature is 230℃, the loading amount of the catalyst prepared in each embodiment and comparative example is 0.8g, and the space velocity is 8000h -1 ; The designed raw gas volume composition is: CO content is 13%, CO 2 The content is 1.2%, H 2 The content of Ar is 80%, the content of Ar is 5.8%, and the gas is provided by Beijing Helium Gas Industry Co., Ltd. The particle size of the catalyst prepared in each embodiment and comparative example is 60 mesh to 100 mesh, and quartz sand of the same particle size is mixed with the catalyst during filling. Among them, the No. 6 reaction tube is filled with quartz sand of the same particle size for online detection of the raw material gas composition.

[0094] The initial activity test process of the catalyst is as follows: after the catalyst to be tested is reduced, the raw gas introduced reacts under the action of the catalyst, and after reacting at 230°C for 48 hours, the gas product (including methanol) after the reaction is obtained, and it is introduced into the gas chromatograph to analyze the composition of the gas product. Before the gas product is introduced into the gas chromatograph, it is heated by a heating belt to stabilize the temperature of the gas product at 120°C, and then introduced into the gas chromatograph. The gas product samples at the outlet of each reaction tube are sampled in turn by the GC analysis system and tested and analyzed for their composition. The activity test process of the catalyst after heat treatment is as follows: after the catalyst to be tested is reduced, the introduced raw gas reacts under the action of the catalyst, and after reacting at 230°C for 48 hours, the temperature is raised to 320°C, and the catalyst is heat-treated at the constant temperature for 24 hours; then the temperature is lowered to 230°C and the raw gas is reacted at this temperature in the presence of the catalyst after the heat treatment for 24 hours, the gas product obtained by the reaction is introduced into a gas chromatograph, and the gas product samples at the outlet of each reaction tube are sampled in turn through the GC analysis system and the composition is detected and analyzed, that is, the activity of the catalyst after heat treatment is evaluated.

[0095] Activity retention % = (activity after heat treatment / initial activity)*100%.

[0096] The catalyst performance evaluation results are shown in Tables 4 and 5.

[0097] Table 4 Test results of catalyst performance evaluation

[0098] Example 1 Example 2 Example 3 Example 4 Initial activity 74.57％ 72.5％ 75.33％ 71.22％ Activity after heat treatment 69.73％ 68.70％ 70.41％ 66.7％ Activity retention rate 93.51％ 94.76％ 93.47％ 93.65％ Methanol selectivity 99.19％ 98.91％ 98.31％ 97.88％

[0099] Table 5 Test results of catalyst performance evaluation

[0100] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Initial activity 74.57％ 72.5％ 45.52％ 53.96％ 65.87％ 51.03％ Activity after heat treatment 69.73％ 68.70％ 35.02％ 41.76％ 59.28％ 41.22％ Activity retention rate 93.51％ 94.76％ 76.93％ 77.39％ 90.00％ 80.78％ Methanol selectivity 99.19％ 98.91％ 95.65％ 95.21％ 96.60％ 94.47％

[0101] It can be seen from Tables 4 and 5 that the catalyst prepared by the preparation method of the present invention has high initial activity. At the same time, due to the low sodium content, the activity loss after heat treatment is very small and the activity retention rate is very high, that is, the thermal stability is significantly improved.

[0102] The catalyst prepared in Comparative Example 1, because the first precipitate is Na 2 CO 3 The aqueous solution is used as a precipitant. Even if the first suspension is washed (washed until the conductivity of the filtrate is less than 1000μs / cm), it is difficult to remove all the sodium in the catalyst, resulting in a decrease in the activity and thermal stability of the catalyst. If you want to remove all the sodium ions contained therein, you need to continue washing the first precipitate, but this will consume a lot of water.

[0103] The catalyst prepared in Comparative Example 2 was subjected to copper-zinc co-precipitation directly in the aluminum precipitation suspension, which resulted in the sodium element being doped into the aluminum-containing carrier, making it difficult to wash and hard to clean, resulting in a decrease in the activity and selectivity of the catalyst.

[0104] In Comparative Example 3, since the temperature of the first precipitation reaction is relatively low, the aluminum ion precipitates easily agglomerate to form needle-shaped colloids or spherical crystals, which is not conducive to the interaction between the aluminum element and the copper-zinc active components, and is not conducive to improving the performance of the catalyst. The activity and selectivity of the catalyst are not high.

[0105] In each embodiment of the present invention, sodium carbonate and / or sodium bicarbonate are used as the second precipitant to form a precursor of zinc malachite ((Cu, Zn) 2 (OH) 2 CO 3 ), allowing copper and zinc elements to fully contact within the same precursor structure can produce a synergistic effect, which is beneficial to improving catalyst performance.

[0106] In Comparative Example 4, oxalate is used as the second precipitant, and two precursors, copper oxalate and zinc oxalate, are formed respectively, which weakens the interaction between the copper element and the zinc element, is not conducive to improving the catalyst performance, and the activity and selectivity of the catalyst are not high.

[0107] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for preparing a methanol synthesis catalyst, It is characterized in that The preparation method comprises the following steps: (1) contacting an Al source with a first precipitant not containing an alkali metal and performing a first precipitation reaction to obtain a first suspension, which is then subjected to an aging treatment, and the obtained product is filtered and washed to obtain a first precipitate; (2) contacting a Cu source, a Zn source and a second precipitant to perform a coprecipitation reaction to obtain a second suspension, which is then subjected to an aging treatment, and the obtained product is filtered and washed to obtain a second precipitate; (3) mixing the first precipitate and the second precipitate, adding deionized water thereto, stirring the mixture evenly, filtering the obtained mixture, and drying and calcining the obtained filter residue in sequence to obtain the methanol synthesis catalyst; Wherein, the first precipitant and the second precipitant are different; the first precipitant is selected from one or more of ammonia water, ammonium salt and urea; the second precipitant is selected from one or more of sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate.

2. The preparation method according to claim 1, It is characterized in that The Al source is a water-soluble compound containing Al element, preferably selected from Al(NO 3 ) 3 、Al 2 (SO 4 ) 3 and AlCl 3 At least one of; and / or The Cu source is a water-soluble compound containing the Cu element, preferably selected from Cu(NO 3 ) 2 、CuSO 4 and CuCl 2 At least one of; and / or The Zn source is a water-soluble compound containing Zn element, preferably selected from Zn(NO 3 ) 2 、ZnSO 4 and ZnCl 2 At least one of .

3. The preparation method according to claim 1, It is characterized in that In step (1), the conditions of the first precipitation reaction include: a reaction temperature of 70-90°C, preferably 70-80°C; a system pH of 5-10, preferably 6-8; and / or In step (1), the conditions for performing an aging reaction after the precipitation reaction include: an aging temperature of 70-90° C., preferably 70-80° C.; and an aging time of 0.5-6 h, preferably 1-2.5 h.

4. The preparation method according to claim 1, It is characterized in that In step (2), the conditions of the coprecipitation reaction include: the reaction temperature is 40-90°C, preferably 60-80°C; the system pH is 5-10, preferably 6-8.

5. The preparation method according to claim 1, It is characterized in that In step (2), the conditions for performing an aging reaction after the coprecipitation reaction include: an aging temperature of 40-90° C., preferably 70-90° C.; and an aging time of 1-12 h, preferably 2-4 h.

6. The preparation method according to any one of claims 1 to 5, It is characterized in that In step (1), the product obtained by the aging treatment is filtered and washed, and the washing conditions are: the conductivity of the washing filtrate finally obtained is less than or equal to 1000 μs / cm; and / or In step (2), the product obtained by the aging treatment is filtered and washed, and the washing condition is: the conductivity of the washing filtrate finally obtained is less than or equal to 100 μs / cm.

7. The preparation method according to any one of claims 1 to 6, It is characterized in that In step (3), the drying conditions include: drying temperature of 90-120° C., drying time of 6-18 h; and / or In step (3), the calcination conditions include: a calcination temperature of 300-390° C. and a calcination time of 2-18 hours.

8. The preparation method according to any one of claims 1 to 7, It is characterized in that Calculated by elements, the molar ratio of the Cu source, Zn source and Al source is (40-65):(20-40):(3-30), preferably (45-65):(20-35):(8-20).

9. A methanol synthesis catalyst obtained by the preparation method according to any one of claims 1 to 8, It is characterized in that Based on the total weight of the methanol synthesis catalyst, the methanol synthesis catalyst includes the following components: Al 2 O 3 1.5wt%-25wt% of aluminum component, 40wt%-70wt% of copper component, calculated as CuO, Calculated as ZnO, 20wt%-45wt% of the zinc component.

10. Use of the methanol synthesis catalyst obtained by the preparation method according to any one of claims 1 to 8 or the methanol synthesis catalyst according to claim 9 in catalytic synthesis of methanol.

Images