A copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst and preparation method thereof

Abstract

The present application relates to the field of catalysts, and more particularly to a copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst and a preparation method thereof. A method for preparing a copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst comprises the following steps: firstly 2+ and Al 3+ The two metal salts are prepared into a salt solution a, the first precipitant is prepared into an alkaline solution b, and the two solutions are used to prepare a hydrotalcite precipitate; then Cu 2+ 、Zn 2+ and Al 3+ The three metal salts are prepared into a salt solution A, the second precipitant is prepared into an alkaline solution B, and the two solutions are used to prepare a second precipitate; the hydrotalcite precipitate and the Al source are then reacted and aged with the second precipitate, the obtained precipitate is cleaned and roasted, and graphite is added, and the mixture is pressed into tablets to obtain a catalyst. The present application ensures that the active component (Cu 2+ 、Zn 2+ and Al 3+ ) is evenly distributed on the carrier, which is conducive to the formation of a catalyst structure with a high specific surface area, thereby improving the activity of the catalyst.

Description

Technical Field

[0001] The present application relates to the field of catalysts, and in particular to a copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst and a preparation method thereof. Background Art

[0002] Industrially, copper-zinc-aluminum catalysts are generally prepared by coprecipitation. The traditional coprecipitation method refers to: a solution contains two or more cations, which exist in the solution in a homogeneous phase, and a precipitant is added. After precipitation reaction, a uniform precipitate of various components can be obtained. The traditional coprecipitation method uses sodium carbonate as a precipitant to form a carbonate precipitate in a copper-zinc-aluminum nitrate mixture under a certain pH value and a certain precipitation temperature. The sodium ions are washed with distilled water, and then dried and roasted to form a copper-zinc-aluminum oxide mixture.

[0003] Gas-phase alcohol dehydrogenation catalysis is a process involving chemical catalysis, in which alcohol compounds, under gas-phase conditions, remove a molecule of hydrogen through the action of a catalyst and are converted into corresponding aldehydes, ketones or other unsaturated compounds. It is an important process in chemical production.

[0004] However, in actual applications, it was found that when the copper-zinc-aluminum catalyst prepared by the co-precipitation method was applied to the gas-phase alcohol dehydrogenation catalytic reaction, the catalytic activity was relatively low due to the small pore size of the copper-zinc-aluminum catalyst, and the catalytic performance of the copper-zinc-aluminum catalyst still needs to be improved. Summary of the invention

[0005] In order to solve the problem of further improving the catalytic performance of copper-zinc-aluminum catalysts, the present application provides a method for preparing a copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst. The catalyst prepared by this method has higher catalytic activity than existing commercial copper-zinc-aluminum catalysts.

[0006] In the first aspect, the present application provides a method for preparing a copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst, using the following technical solution:

[0007] A method for preparing a copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst comprises the following steps:

[0008] (1) Weigh Zn 2+ and Al 3+ Two metal salts are dissolved to form salt solution a;

[0009] (2) dissolving a first precipitant to prepare an alkaline solution b; the first precipitant comprises a mixture of sodium carbonate and sodium hydroxide;

[0010] (3) mixing the salt solution a and the alkaline solution b for reaction, and after the reaction is completed, centrifuging, washing and drying to obtain a hydrotalcite precipitate;

[0011] (4) Weigh Cu 2+、Zn 2+ 、Al 3+ Three metal salts are dissolved in water to obtain salt solution A;

[0012] (5) dissolving a second precipitant in water to prepare an alkaline solution B; the second precipitant comprises one of sodium carbonate, sodium bicarbonate and sodium hydroxide;

[0013] (6) adding the salt solution A and the alkaline solution B into a reaction container containing deionized water in parallel, maintaining the pH value in the reaction container in the range of 6.0-6.5, to obtain a reaction solution containing a second precipitate;

[0014] (7) After the second precipitate is stabilized, the hydrotalcite precipitate obtained in step (3) and the Al source are added to the reaction solution containing the second precipitate obtained in step (6) to continue aging;

[0015] (8) After aging is completed, filter the precipitate to obtain the catalyst precursor, wash, dry, and calcine to obtain a calcined product;

[0016] (9) The calcined product is uniformly mixed with graphite to obtain a mixture, and the mixture is pressed into tablets to obtain a catalyst.

[0017] By adopting the above technical solution, firstly, Zn 2+ and Al 3+ The initial hydrotalcite precipitate is formed at the same time. This hydrotalcite structure itself has a large specific surface area. Subsequently, in a reaction vessel containing deionized water, Cu 2+ 、Zn 2+ and Al 3+ The second precipitate is then reacted with the second precipitant to form a second precipitate, on which the hydrotalcite precipitate obtained in the first step and an additional Al source are introduced for further aging. This hierarchical and continuous precipitation process ensures that the active component (Cu 2+ 、Zn 2+ and Al 3+ ) are evenly distributed on the carrier, which is conducive to the formation of a catalyst structure with a high specific surface area. A high specific surface area means that more reaction sites are exposed on the surface, thereby improving the activity of the catalyst.

[0018] Preferably, in step (4), an alkaline earth metal salt is also added to the Cu 2+ 、Zn 2+ 、Al 3+ The three metal salts are dissolved together by ultrasonication to obtain salt solution A.

[0019] By adopting the above technical solution, the addition of alkaline earth metal salts can provide more active sites for the catalyst without significantly increasing the total volume of the catalyst. These sites can directly participate in the gas phase alcohol dehydrogenation reaction, or indirectly improve the reaction activity by affecting the acidity and alkalinity, redox properties, etc. of the catalyst surface. Therefore, the addition of alkaline earth metal salts helps to increase the relative content of active components within a limited catalyst volume, thereby improving the catalytic efficiency of the catalyst.

[0020] Alkaline earth metal elements generally have good structural stability and thermal stability, and they can enhance the overall structural strength of the catalyst. This enhanced structural stability helps the catalyst maintain its morphology and composition during high-temperature calcination, reduces the loss and sintering of active components, and thus improves the service life and stability of the catalyst.

[0021] The addition of alkaline earth metal salts can regulate the acidity and alkalinity of the catalyst surface, thereby affecting the catalyst's ability to adsorb and desorb reactants and products. In addition, alkaline earth metal elements may also participate in the redox cycle of the catalyst, changing the redox properties of the catalyst, thereby optimizing the catalytic reaction path and improving the selectivity and yield of the target product.

[0022] Preferably, the alkaline earth metal salt comprises Mg 2+ Salt and Ca 2+ At least one of the salts.

[0023] By adopting the above technical solution, oxides such as MgO and CaO have high stability at high temperatures, which can effectively prevent the sintering and deactivation of the catalyst during calcination and use, thereby extending the service life of the catalyst. Mg and Ca elements tend to form a relatively neutral surface, which helps to adjust the acidity and alkalinity of the catalyst, thereby optimizing the adsorption and desorption capabilities of reactants and products and improving the selectivity of the catalytic reaction.

[0024] Preferably, in step (4), a rare metal salt is also added.

[0025] By adopting the above technical solution, the addition of rare metal salts may optimize the structure and distribution of active centers on the catalyst surface. By optimizing the active centers, rare metals can enhance the catalyst's ability to adsorb and activate alcohol molecules, thereby improving the selectivity of aldehydes in the product. Rare metal elements have special electronic structures, and their addition may trigger changes in electronic effects in the catalyst. These changes in electronic effects may affect the charge distribution and energy state on the catalyst surface, thereby optimizing the path and energy barriers of the catalytic reaction, making it easier for alcohols to be converted into aldehydes.

[0026] Preferably, in step (7), the Al source includes Al 3+ Salt and Al 3+ At least one of the oxides of.

[0027] By adopting the above technical solution, whether it is Al 3+ Salt or Al 3+ Oxides, they can all play a role in stabilizing the structure of the catalyst. Especially Al 3+ Oxides (such as Al2O3), which have high thermal and chemical stability, can prevent the catalyst from sintering or structural collapse during high-temperature calcination, thereby improving the long-term performance of the catalyst.

[0028] Add Al source to the Cu 2+ 、Zn 2+ The introduction of Al source may affect the precipitation and distribution of active components by changing the pH value, ion concentration or forming new chemical bonds in the local environment.

[0029] Al has a certain acidity, and its addition can adjust the acidity and alkalinity of the catalyst surface, thereby affecting the catalyst's ability to adsorb and desorb reactants and products. Appropriate acidity and alkalinity help optimize the catalytic reaction path and improve the selectivity and yield of the target product.

[0030] Preferably, the Al source is Al 3+ of oxides.

[0031] By adopting the above technical solution, select Al 3+ Oxides (especially α-alumina) as Al sources are indeed beneficial to improving the thermal stability of the catalyst, increasing the basicity of the catalyst surface, and thereby improving the selectivity of the catalyst.

[0032] α-alumina is an oxide with a high melting point and excellent high temperature resistance. During high temperature calcination, α-alumina can maintain its structural stability and is not prone to sintering or phase change, thus effectively preventing the catalyst from structural collapse and deactivation at high temperatures.

[0033] α-alumina, as the skeleton component of the catalyst, can enhance the mechanical strength and thermal stability of the catalyst. Its stable crystal structure can support the overall structure of the catalyst and prevent the catalyst from breaking or pulverizing due to thermal stress at high temperature and during the reaction process.

[0034] Preferably, in steps (1) and (2), the solvents of the salt solution a and the alkaline solution b include water, a first mixed solvent of water and isopropanol, and a second mixed solvent of water, n-hexane and isopropanol.

[0035] Preferably, the solvent of the salt solution a and the alkaline solution b is a mixed solvent of water, n-hexane and isopropanol.

[0036] By adopting the above technical scheme, a mixed solvent is more beneficial to the present application than a single solvent. In a system with organic matter and water as a mixed solvent, an oil-in-water (W / O) microemulsion or microcapsule structure can be formed by controlling the conditions. This structure provides a unique microenvironment for the formation of hydrotalcite, which is conducive to the growth and dispersion of hydrotalcite crystals. The tiny water droplets in the oil-in-water structure act as a "microreactor" for the growth of hydrotalcite, which can significantly increase the nucleation density and growth rate of hydrotalcite, thereby generating hydrotalcite with a higher specific surface area. This high specific surface area hydrotalcite can provide more favorable growth sites in the subsequent preparation of catalysts, thereby improving the activity and selectivity of the catalyst.

[0037] The organic solvent in the mixed solvent can affect the pore structure and dispersibility of the hydrotalcite crystals to a certain extent, making them more uniform. This structural feature is beneficial to the mass transfer and heat transfer efficiency of the catalyst in subsequent applications, and improves the catalytic performance.

[0038] Preferably, in step (9), the amount of graphite used is 1-3 wt % of the mixture.

[0039] By adopting the above technical solution, graphite has good electrical and thermal conductivity. At the same time, it can also react with oxides such as copper oxide to generate CO and CO2. This reaction process promotes the reduction reaction. During the preparation of the catalyst, this reduction reaction helps to reduce metal oxides such as copper, zinc, and aluminum to the corresponding metals, thereby improving the activity of the catalyst. The addition of graphite may help to form more porous structures during the preparation of the catalyst, thereby increasing the specific surface area of ​​the catalyst. The increase in specific surface area means that the catalyst has more active sites, which can more effectively contact the reactants and catalyze the reaction, thereby improving the catalytic efficiency of the catalyst.

[0040] In a second aspect, the present application provides a copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst, which adopts the following technical solution:

[0041] A copper-zinc-aluminum series gas-phase alcohol dehydrogenation catalyst is prepared by the preparation method of the copper-zinc-aluminum series gas-phase alcohol dehydrogenation catalyst.

[0042] By adopting the above technical scheme, the copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst of the present application has the same technical advantages as the above preparation method over the prior art, which will not be repeated here.

[0043] In summary, this application has the following beneficial effects:

[0044] 1. Since this application is through Zn 2+ and Al3+ The initial hydrotalcite precipitate is formed by the simultaneous precipitation of Cu 2+ 、Zn 2+ and Al 3+ The second precipitate is formed by reacting with the precipitant, and the hydrotalcite precipitate obtained in the first step and an additional Al source are introduced on this basis for further aging; this hierarchical and continuous precipitation process ensures that the active components (Cu 2+ 、Zn 2+ and Al 3+ ) is evenly distributed on the carrier, and a special structure is formed between the active component and the carrier, which is conducive to forming a catalyst structure with a high specific surface area, thereby improving the activity of the catalyst;

[0045] 2. In the present application, an alkaline earth metal salt is further added in step (4). The addition of the alkaline earth metal salt can provide more active sites for the catalyst without significantly increasing the total volume of the catalyst, thereby improving the catalytic efficiency of the catalyst;

[0046] 3. In step (7) of the present application, the Al source is Al oxide (especially α-alumina) as the Al source, which is beneficial to improve the thermal stability of the catalyst and thus improve the selectivity of the catalyst;

[0047] 4. In steps (1) and (2) of the present application, the solvent of the salt solution a and the alkaline solution b is a mixed solvent of water, n-hexane and isopropanol. By controlling the conditions, a water-in-oil (W / O) microemulsion or microcapsule structure can be formed; this structure provides a unique microenvironment for the formation of hydrotalcite, is conducive to the growth and dispersion of hydrotalcite crystals, is conducive to the formation of hydrotalcite with a higher specific surface area, and improves the activity and selectivity of the catalyst. DETAILED DESCRIPTION

[0048] The raw materials in this application include the following parts:

[0049] Zn 2+ Salt: Zn of this application 2+ The salt may be zinc nitrate, zinc sulfate, etc., and this application uses a commercially available zinc nitrate product with a CAS number of 7779-88-6 as an example;

[0050] Al 3+ Salt: Al in this application 3+ The salt can be aluminum nitrate, aluminum sulfate, etc., and this application uses commercially available aluminum nitrate products with CAS number 13473-90-0 and commercially available aluminum sulfate products with CAS number 16828-11-8 as examples;

[0051] The first precipitant includes a commercial product of sodium carbonate with a CAS number of 497-19-8 and a commercial product of sodium hydroxide with a CAS number of 1310-73-2;

[0052] Second precipitant: The precipitant of the present application includes sodium carbonate, sodium bicarbonate and sodium hydroxide. The present application takes the commercially available sodium carbonate product with CAS No. 497-19-8 as an example;

[0053] Cu 2+ Salt: Cu in this application 2+ The salt may be copper nitrate, copper sulfate, etc., and this application uses a commercially available copper nitrate product with a CAS number of 10402-29-6 as an example;

[0054] Deionized water: Use commercially available product with CAS number 7732-18-5;

[0055] Mg 2+ Salt: Mg of this application 2+ The salt may be magnesium nitrate, magnesium sulfate, etc., and this application uses a commercially available magnesium nitrate product with a CAS number of 10377-60-3 as an example;

[0056] Ca 2+ Salt: Ca in this application 2+ The salt may be calcium nitrate, calcium sulfate, etc., and this application uses a commercially available calcium nitrate product with a CAS number of 10124-37-5 as an example;

[0057] Rare metal salt: The rare metal salt of the present application may be cerium nitrate, praseodymium nitrate, etc. The present application takes the commercially available cerium nitrate product with CAS No. 13093-17-9 as an example;

[0058] α-alumina and β-alumina: commercially available products;

[0059] n-Hexane: a commercial product with CAS number 110-54-3 was used;

[0060] Isopropyl alcohol: a commercially available product with CAS number 67-63-0 is used;

[0061] Graphite: a commercially available product with CAS number 7782-42-5 was used;

[0062] Commercially available copper-zinc-aluminum catalyst: copper-zinc-aluminum catalyst for methanol dehydrogenation purchased from the market is used as an example;

[0063] The present application is further described in detail below with reference to examples and comparative examples.

[0064] Example 1

[0065] A method for preparing a copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst comprises the following steps:

[0066] (1) Dissolve 0.04 mol Zn(NO3)2 and 0.01 mol Al(NO3)3 in 600 mL deionized water to form salt solution a;

[0067] (2) Dissolve 0.05 mol of NaCO3 and 0.15 mol of NaOH in 600 mL of deionized water to form alkaline solution b;

[0068] (3) After mixing the salt solution a and the alkaline solution b, ultrasonicate for 30 minutes, separate them using a centrifuge, wash them with ethanol for 5 times, and dry them to obtain a hydrotalcite precipitate;

[0069] (4) Dissolve 0.15 mol of Cu(NO3)2, 0.24 mol of Zn(NO3)2 and 0.01 mol of Al(NO3)3 in 500 mL of deionized water, dissolve by ultrasonication, and stir to fully dissolve to form salt solution A;

[0070] (5) Dissolve 0.40 mol of NaCO3 in 2000 mL of deionized water and stir to fully dissolve it to form the alkaline solution B required for precipitation;

[0071] (6) Under strong stirring, salt solution A and alkaline solution B are simultaneously added dropwise into a reaction tank containing 500 mL of deionized water, wherein the pH value in the reaction tank is in the range of 6.0-6.5, to obtain a reaction solution containing a second precipitate;

[0072] (7) After the precipitation in the reaction tank has formed for 15 minutes, all the above hydrotalcite precipitation and 0.005 mol of α-alumina are added, and the reaction temperature of the reaction tank is controlled to 80°C with a water bath, and the reaction is aged at a constant temperature for 2 hours;

[0073] (8) After aging is completed, filter and wash the precipitate with deionized water until there is no Na + The obtained precipitate was dried at 120°C for 24h, and the dried product was calcined at 500°C at a rate of 5°C / min for 6h to obtain a calcined product;

[0074] (9) Add graphite to the calcined product and mix evenly to obtain a mixture, wherein the amount of graphite is 3% by mass of the mixture, and then press the mixture into tablets to obtain a catalyst.

[0075] Embodiment 2-4

[0076] Example 2 Based on the preparation method of Example 1, in step (4), 0.015 mol of Mg(NO3)2 is further added and ultrasonically dissolved together with other metal salts to form salt solution A, while other conditions remain unchanged.

[0077] Example 3 Based on the preparation method of Example 1, in step (4), 0.015 mol of Ca(NO3)2 is further added and ultrasonically dissolved together with other metal salts to form salt solution A, while other conditions remain unchanged.

[0078] Example 4 Based on the preparation method of Example 1, in step (4), 0.015 mol of Ce(NO3)3·6H2O is further added and ultrasonically dissolved together with other metal salts to form salt solution A, while other conditions remain unchanged.

[0079] Comparative Examples 1-4

[0080] Comparative Example 1 Based on the preparation method of Example 1, in step (4), 0.015 mol of NaNO3 is further added and ultrasonically dissolved together with other metal salts to form salt solution A, and other conditions remain unchanged.

[0081] Comparative Example 2 used a commercially available copper-zinc-aluminum catalyst.

[0082] Comparative Example 3: Based on the preparation method of Example 2, in step (1), 0.005 mol of Mg(NO3)2 is added to form a new salt solution a with other metal salts; in step (4), 0.010 mol of Mg(NO3)2 is also added to ultrasonically dissolve with other metal salts to form salt solution A, and other conditions remain unchanged.

[0083] Comparative Example 4 Based on the preparation method of Example 1, in step (1), 0.015 mol of Mg(NO3)2 is further added to form a new salt solution a with other metal salts, and other conditions remain unchanged.

[0084] Table 1 Performance test table of Examples 1-4 and Comparative Examples 1-4

[0085]

[0086] Performance testing

[0087] The copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalysts of Examples 1-4 and Comparative Examples 1-4 were subjected to the following performance tests. The test results are shown in Table 1.

[0088] 1. Isooctyl alcohol conversion rate, isooctyl aldehyde selectivity and specific surface area

[0089] The copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst was used for fixed-bed reaction to test the catalytic performance. The reaction liquid was isooctyl alcohol (the copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst of the present application can be used in catalyzing the preparation of organic aldehydes from organic alcohols, such as methanol to formaldehyde, ethanol to acetaldehyde, isooctyl alcohol to isooctyl aldehyde, etc., and isooctyl alcohol is used as an example in the present application). The liquid phase space velocity is 10h -1The catalyst performance test experiment was carried out at 250°C. The isooctyl alcohol conversion rate = (1-the mass content of isooctyl alcohol in the liquid phase product after the reaction) × 100%.

[0090] Isooctyl aldehyde selectivity = isooctyl aldehyde mass content in the reaction liquid phase product / (1-isooctyl alcohol mass content in the reaction liquid phase product) × 100%.

[0091] 2. Specific surface area

[0092] The specific surface area of ​​the catalyst was measured on a COULTERSA3100 analyzer and was determined by linear regression using the BET equation.

[0093] Referring to Table 1, it can be seen from the comparison between Examples 1-4 and Comparative Examples 1-4 that, compared with Comparative Example 2, the isooctyl alcohol conversion rate, isooctyl aldehyde selectivity and specific surface area of ​​Example 1 are higher than those of Comparative Example 2, indicating that the hierarchical and continuous precipitation process ensures the uniform distribution of active components (Cu, Zn, Al) on the carrier, which is conducive to the formation of a catalyst structure with a high specific surface area. A high specific surface area means that more reaction sites are exposed on the surface, thereby improving the activity of the catalyst.

[0094] Compared with Example 1, the isooctyl alcohol conversion rate and isooctyl aldehyde selectivity of Example 2-3 are higher than those of Example 1, indicating that the addition of alkaline earth metal salt in step (4) can provide more active sites for the catalyst through its embedding in the hydrotalcite structure, thereby improving the catalytic efficiency of the catalyst. In comparison, adding Mg salt is better than adding Ca salt, that is, Example 2 is preferred.

[0095] The selectivity of isooctylaldehyde in Example 4 is higher than that in Example 1 and Comparative Example 2, but the conversion rate of isooctyl alcohol is lower than that in Example 1 and higher than that in Comparative Example 2. This may be because the addition of cerium nitrate may optimize the structure and distribution of the active center on the catalyst surface. By optimizing the active center, cerium ions can enhance the adsorption and activation ability of the catalyst to isooctyl alcohol molecules, thereby improving the selectivity of isooctylaldehyde. However, cerium ions may change the acidity and alkalinity of the catalyst surface, thereby reducing the conversion ability of the catalyst to isooctyl alcohol.

[0096] The selectivity of isooctyl aldehyde in Comparative Example 1 is higher than that in Example 1 and Comparative Example 2, but the conversion rate of isooctyl alcohol is lower than that in Example 1 and is basically the same as that in Comparative Example 2. Comprehensive comparison shows that the catalyst performance is not as improved as that of adding alkaline earth metal salts or cerium nitrate.

[0097] The isooctyl alcohol conversion rate, isooctyl aldehyde selectivity and specific surface area of ​​comparative examples 3-4 are lower than those of examples 1-2, indicating that the addition of alkaline earth metal salt Mg(NO3)2 in step (1) may destroy the hydrotalcite structure, affect the distribution of metal elements, reduce the catalytic sites, and reduce the performance of the catalyst.

[0098] Embodiment 5-7

[0099] Example 5 Based on the preparation method of Example 2, 0.005 mol of α-alumina in step (7) is replaced by 0.005 mol of β-alumina, and other conditions remain unchanged.

[0100] Example 6 Based on the preparation method of Example 2, 0.005 mol of α-alumina in step (7) is replaced by 0.01 mol of Al(NO3)3, and other conditions remain unchanged.

[0101] Example 7 Based on the preparation method of Example 2, 0.005 mol of α-alumina in step (7) is replaced by 0.005 mol of Al2(SO4)3, and other conditions remain unchanged.

[0102] Comparative Examples 5-8

[0103] Comparative Example 5: Based on the preparation method of Example 6, 0.02 mol of Al(NO3)3 was added in step (1), and Al(NO3)3 was not added in step (4), while other conditions remained unchanged.

[0104] Comparative Example 6: Based on the preparation method of Example 6, no Al(NO3)3 is added in step (4), and 0.02 mol of Al(NO3)3 is added in step (7), while other conditions remain unchanged.

[0105] Comparative Example 7 is based on the preparation method of Example 6, except that 0.02 mol of Al(NO3)3 is added in step (4), and Al(NO3)3 is not added in step (7), while other conditions remain unchanged.

[0106] Comparative Example 8 is based on the preparation method of Example 6, except that 0.02 mol of Al(NO3)3 is added in step (1), and Al(NO3)3 is not added in step (7), while other conditions remain unchanged.

[0107] The copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalysts of Examples 5-7 and Comparative Examples 5-8 were subjected to the above performance tests. The test results are shown in Table 2.

[0108] Table 2 Performance test table of Example 2, Examples 5-7 and Comparative Examples 5-8

[0109]

[0110] Referring to Table 2, it can be seen from the comparison between Example 2, Examples 5-7 and Comparative Examples 5-8 that in step (7), whether adding Al oxide or Al salt, both can be used in the present application, mainly because they can play a role in stabilizing the structure of the catalyst.

[0111] In addition, selecting Al oxide (especially α-alumina) as the Al source is beneficial to improving the thermal stability of the catalyst, increasing the basicity of the catalyst surface, and thereby improving the selectivity of the catalyst.

[0112] The isooctyl alcohol conversion rate, isooctyl aldehyde selectivity and specific surface area of ​​Comparative Examples 5-8 are much lower than those of Example 6, indicating that the addition of Al element at each stage is very necessary. Whether it is in the formation of hydrotalcite precipitation, the second precipitation or the Al source added in step (7), it cannot be reduced, otherwise it will affect the overall structure of the catalyst and the uniform distribution of the active ingredients.

[0113] Embodiment 8-10

[0114] Example 8 Based on the preparation method of Example 2, the solvents in steps (1) and (2) were adjusted to a second mixed solvent of 200 mL of water, 200 mL of n-hexane and 200 mL of isopropanol, and the other conditions remained unchanged.

[0115] Example 9 Based on the preparation method of Example 2, the solvents in steps (1) and (2) were adjusted to a first mixed solvent of 300 mL of water and 300 mL of isopropanol, and the other conditions remained unchanged.

[0116] The copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalysts of Examples 8-9 were subjected to the above performance tests, and the test results are shown in Table 3.

[0117] Table 3 Performance test table of Example 2 and Example 8-9

[0118]

[0119] Referring to Table 3, by comparing Example 2 with Examples 8-9, it can be seen that the solvent in steps (1) and (2) is a mixture of an organic solvent and water, which is more conducive to the present application. This may be because in a system with organic matter and water as a mixed solvent, an oil-in-water (W / O) microemulsion or microcapsule structure can be formed by controlling the conditions. This structure provides a unique microenvironment for the formation of hydrotalcite, which is conducive to the growth and dispersion of hydrotalcite crystals. The tiny water droplets in the oil-in-water structure act as a "microreactor" for the growth of hydrotalcite, which can significantly increase the nucleation density and growth rate of hydrotalcite, thereby generating hydrotalcite with a higher specific surface area. This high specific surface area hydrotalcite can provide more favorable growth sites in the subsequent preparation of catalysts, thereby improving the activity and selectivity of the catalyst.

[0120] Examples 10-13

[0121] In Examples 10-13, based on the preparation method of Example 2, the mass proportion of graphite in the mixture is adjusted, and the specific adjustments are shown in Table 4.

[0122] The copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalysts of Examples 10-13 were subjected to the above performance tests, and the test results are shown in Table 4 respectively.

[0123] Table 4 Mass proportion of graphite in the mixture and performance test table in Example 2 and Examples 10-13

[0124]

[0125] Referring to Table 4, it can be seen from Comparative Example 2 and Example 10-13 that as the mass proportion of graphite in the mixture increases, the isooctyl alcohol conversion rate, isooctyl aldehyde selectivity and specific surface area of ​​the catalyst present an increasing trend of stabilizing after increasing. Graphite can react with oxides such as copper oxide to generate CO and CO2, and this reaction process promotes the carrying out of the reduction reaction. In the preparation process of the catalyst, this reduction reaction helps to reduce metal oxides such as copper, zinc, and aluminum to corresponding metals, thereby improving the activity of the catalyst. Of course, the performance of the catalyst for graphite is also limited. When the mass proportion of graphite reaches a certain level, the activity of the catalyst is difficult to continue to improve.

[0126] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for preparing a copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst, characterized in that: The specific preparation steps include: (1) Weigh Zn 2+ and Al 3+ Two metal salts are dissolved to form salt solution a; (2) dissolving a first precipitant to prepare an alkaline solution b; the first precipitant comprises a mixture of sodium carbonate and sodium hydroxide; (3) mixing the salt solution a and the alkaline solution b for reaction, and after the reaction is completed, centrifuging, washing and drying to obtain a hydrotalcite precipitate; (4) Weigh Cu 2+ 、Zn 2+ 、Al 3+ Three metal salts are dissolved in water to obtain salt solution A; (5) dissolving a second precipitant in water to prepare an alkaline solution B; the second precipitant comprises one of sodium carbonate, sodium bicarbonate and sodium hydroxide; (6) adding the salt solution A and the alkaline solution B into a reaction container containing deionized water in parallel, maintaining the pH value in the reaction container in the range of 6.0-6.5, to obtain a reaction solution containing a second precipitate; (7) After the second precipitate is stabilized, the hydrotalcite precipitate obtained in step (3) and the Al source are added to the reaction solution containing the second precipitate obtained in step (6) to continue aging; (8) After aging is completed, filter the precipitate to obtain the catalyst precursor, wash, dry, and calcine to obtain a calcined product; (9) uniformly mixing the calcined product with graphite to obtain a mixture, and pressing the mixture into tablets to obtain a catalyst; In step (4), an alkaline earth metal salt or a rare metal salt is also added to the Cu 2+ 、Zn 2+ 、Al 3+ The three metal salts are dissolved together to obtain a salt solution A; the alkaline earth metal salt includes Mg 2+ Salt and Ca 2+ at least one of salt; In step (7), the Al source includes Al 3+ Salt and Al 3+ At least one of the oxides of.

2. The method for preparing the copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst according to claim 1, characterized in that: The Al source is Al 3+ of oxides.

3. The method for preparing the copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst according to claim 1, characterized in that: In steps (1) and (2), the solvents of the salt solution a and the alkaline solution b include water, a first mixed solvent of water and isopropanol, and a second mixed solvent of water, n-hexane and isopropanol.

4. The method for preparing the copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst according to claim 3, characterized in that: The solvents of the salt solution a and the alkaline solution b are a second mixed solvent of water, n-hexane and isopropanol.

5. The method for preparing the copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst according to claim 1, characterized in that: In step (9), the amount of graphite used is 1-3 wt % of the mixture.

6. A copper-zinc-aluminum gas-phase alcohol dehydrogenation catalyst, characterized in that: The catalyst is prepared by the method for preparing the copper-zinc-aluminum-based gas-phase alcohol dehydrogenation catalyst according to any one of claims 1 to 5.

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