Catalyst for preparing alcohol through octenal gas phase hydrogenation and preparation method thereof

Abstract

The invention relates to the technical field of catalyst preparation, in particular to an octenal gas phase hydrogenation alcohol preparation catalyst and a preparation method thereof. According to the technical scheme, the preparation method comprises the following steps: S1, mixing a zinc source and water to prepare a zinc salt solution; s2, dropwise adding a precipitant and an aluminum salt solution into the solution prepared in the step S1 in a parallel flow manner, uniformly mixing, stirring, keeping the temperature, and aging until the precipitation is complete; s3, dropwise adding a precipitant, an auxiliary agent and a copper salt and zinc salt mixed solution into the mother solution prepared in the step S2 in a parallel flow manner, uniformly mixing, stirring the materials, and carrying out heat preservation, so that the materials are neutralized and aged; and S4, washing and filtering the mature material in the step S3, drying the obtained filter cake, and calcining the powder at high temperature. The method has the advantages that coprecipitation is completed by embedding an aluminum system in the precipitation process through the strong driving force of zinc until coprecipitation is completed, generation of independent Al2O3 is reduced to a great extent, and meanwhile, the possibility that copper salt is added subsequently to generate CuAl2O3 is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and particularly to a catalyst for gas-phase hydrogenation of octenal to alcohol and a preparation method thereof. Background Art

[0002] Octanol is an important fine chemical raw material and is widely used in fields such as lipids, plasticizers, and surfactants. In domestic butanol and octanol plants, a combined process of gas-phase aldehyde hydrogenation and liquid-phase aldehyde hydrogenation is generally selected. The gas-phase aldehyde hydrogenation catalyst is mainly a copper-zinc (Cu-Zn) catalyst, which has the characteristics of strong activity, long service life, and high strength. Currently, the aldehyde hydrogenation catalysts used in China are mainly the OXO-1 and OXO-2 gas-phase aldehyde hydrogenation catalysts of Southern German Chemical, the VAH-1 and VAH-2 developed by the Research Institute of Sinopec, and the NCH6-1 and NCH6-2 gas-phase aldehyde hydrogenation catalysts of Nanjing Chemical Industry Research Institute. These catalysts are all Cu-Zn series catalysts prepared by the co-precipitation method. The metal salt solution and the precipitant are stirred and co-precipitated, aged, dried, and calcined in a reaction kettle to form the corresponding oxides, and then reduced by hydrogen to obtain a catalyst with copper as the active component.

[0003] The Cu-Zn catalyst has problems such as poor thermal stability and high side reactions. The stability and selectivity of the catalyst are mainly improved by innovating the preparation process, optimizing the preparation conditions, adding additives, etc. US Patent No. US5008235 adds one or more metals among Mg, Zn, Ti, Zr, Sn, Ni, and Co during the co-precipitation process to improve the selectivity of the target product. However, the increase in the reduction temperature causes the aggregation of copper particles, resulting in a decrease in activity.

[0004] In Tianjin Research Institute of Chemical Industry, in Chinese Patent CN1695802A, metal salts (one or more of Mg, Ca, Mn, Al) are used as additives to adjust the surface acidity of the catalyst and improve the selectivity of alcohols. Nanjing Chemical Industry Group Research Institute proposed in Chinese Patents CN1381311A and CN1381312A a gas-phase aldehyde hydrogenation catalyst prepared by co-precipitation of a mixed solution of nitrates of copper, zinc, and aluminum with a precipitant and adding a small amount of additives, which has high low-temperature activity selectivity and stability. However, during the preparation process of the catalyst, Cu2+ and A12O42- are prone to pre-combine to form a stable CuA12O4 spinel structure, reducing the amount of reducible metallic copper and resulting in a decrease in the activity of the catalyst. Chinese Patent CN1883795A uses a continuous stepwise co-precipitation method to prepare a gas-phase aldehyde hydrogenation catalyst with a zinc-aluminum spinel structure. In the first step, zinc and aluminum are co-precipitated to obtain more heat-resistant ZnA12O4, but there is still separate alumina, and its acidity and dehydration properties lead to various side reactions during the catalytic process, reducing the reaction selectivity. Patent CN202111430307.1 uses sodium aluminate as the aluminum source, which can avoid the formation of free alumina to a certain extent. However, the one-step precipitation method reduces the high dispersion of copper oxide grains, and the particle diameter is relatively large. Patent CN117899877A changes the one-step precipitation to stepwise precipitation. First, a zinc-aluminum layered double hydroxide is formed, and then CuO is precipitated on the lamellae. The dispersion degree and catalytic activity of copper oxide are improved by using the lamellar defect sites and confinement effects. However, the thermal stability of the catalyst prepared by this method has decreased. Summary of the Invention

[0005] The purpose of the present invention is to overcome at least one defect (insufficiency) of the above-mentioned prior art, and provide a catalyst for the gas-phase hydrogenation of octenal to alcohol and its preparation method. By precisely adjusting the precipitation pH, the complete precipitation of components in sequence is realized, the contents of CuA12O4 and A12O3 are reduced, and at the same time, additives are added to improve the selectivity and thermal stability of the gas-phase aldehyde hydrogenation reaction.

[0006] The technical solution of the present invention is as follows: A preparation method of a catalyst for the gas-phase hydrogenation of octenal to alcohol, which is characterized by including the following steps: S1 First, a zinc source and water are mixed to prepare a zinc salt solution; S2 A precipitant and an aluminum salt solution are added dropwise to the solution prepared in step S1 in parallel flow. After mixing evenly, the mixture is stirred, kept warm, and aged until precipitation is complete; S3 A precipitant, an additive, and a mixed solution of a copper salt and a zinc salt are added dropwise to the mother liquor prepared in step S2 in parallel flow. After mixing evenly, the material is stirred and kept warm to make the material neutralized and aged; S4 The mature material in step S3 is washed with water and filtered, and the obtained filter cake is dried and then calcined at a high temperature; Graphite and water are added to the material after S5 calcination for granulation. After tabletting, a catalyst is obtained and used for the gas-phase hydrogenation of aldehyde to alcohol. In the metal solution in step S1, the concentration of zinc ions is 0.8 - 1.5 mol / L. In step S2, the concentration of aluminum ions in the metal solution is 0.05 - 0.12 mol / L; the concentration of the precipitant is 1.2 - 5 mol / L. In step S3, the concentration of the mixed metal salt solution is 1.1 - 1.6 mol / L, and the concentration of the alkaline precipitant is 0.5 - 2 mol / L. In step S2, the ionic mol ratio of the zinc salt solution to the aluminum salt solution is (11 - 14):1. In step S3, the ionic mol ratio of the copper salt solution to the zinc salt solution in the mixed metal salt solution is (1 - 3):1. In step S2, the coprecipitation temperature is from room temperature to 75 °C, the rotation speed is 200 - 500 rpm / min, the pH value at the end of coprecipitation is 8.5 - 10, and the aging time is 30 - 60 min. In step S3, the coprecipitation temperature is 60 - 90 °C, the rotation speed is 200 - 500 rpm / min, the pH value at the end of coprecipitation is 7.5 - 8.5, and the aging time is 1 - 2 h. The calcination temperature in step S4 is 350 - 400 °C, and the calcination time is 4 - 5 h.

[0007] Furthermore, the zinc source is one or a mixture of zinc nitrate, zinc acetate, and zinc chloride, the copper salt is one or a mixture of copper nitrate, copper acetate, and copper chloride, the precipitant is any one or a mixture of sodium carbonate, sodium bicarbonate, sodium oxalate, and sodium hydroxide; the promoter is any one or a mixture of MgAl alloy powder, silica sol, and SiC.

[0008] A catalyst prepared by a method for preparing a catalyst for the gas-phase hydrogenation of octenal to alcohol, characterized in that: by mass percentage, the catalyst contains 30% - 36% copper oxide, 58% - 64% zinc oxide, 1% - 10% aluminum oxide, 0.5 - 2.5% promoter, and 1 - 3% graphite, and the total mass percentage is 100%.

[0009] A catalyst prepared by a method for preparing a catalyst for the gas-phase hydrogenation of octenal to alcohol, characterized in that: the specific surface area of the catalyst is 60 - 100 m2 / g, the pore volume is 0.35 - 0.7 cm2 / g, and the average pore radius is 10 - 20 nm.

[0010] The beneficial effects of the present invention: (1) The precipitation of the aluminum source is carried out in a high-concentration metal zinc solution. By adjusting the pH, the preferential precipitation of Al is achieved. While precipitating, Zn is wrapped and embedded in it, and a part of ZnO precipitation is formed on the periphery. This can not only reduce the possibility of subsequent formation of CuAl2O4 but also play a role as part of the crystal seeds for subsequent copper-zinc coprecipitation.

[0011] (2) During the second-step coprecipitation, copper oxide is preferentially precipitated, and the free Zn better combines with the mother liquor of the previous step. Subsequently, zinc oxide is precipitated and wraps part of the copper oxide, forming a catalyst with a high specific surface area and high pore volume, improving the mass and heat transfer efficiency, and reducing the generation of side reactions.

[0012] (3) Adding additives effectively weakens the reaction hot spot temperature, reduces the generation amount of by-products under high-temperature conditions, especially the proportion of heavy components, and further improves the octanol selectivity and conversion rate of the gas-phase aldehyde hydrogenation reaction. Specific implementation mode

[0013] A preparation method of a catalyst for the gas-phase hydrogenation of octenal to alcohol, characterized by comprising the following steps: S1 First, a zinc salt solution is prepared by mixing a zinc source and water. S2 A precipitating agent and an aluminum salt solution are added dropwise to the solution obtained in step S1 in parallel flow. After mixing evenly, the mixture is stirred, kept warm, and aged until precipitation is complete. S3 A precipitating agent, an additive, and a mixed solution of a copper salt and a zinc salt are added dropwise to the mother liquor obtained in step S2 in parallel flow. After mixing evenly, the material is stirred and kept warm to make the material neutralized and aged. S4 The mature material in step S3 is washed with water and filtered, and the obtained filter cake is dried and then calcined at a high temperature in powder form. Graphite and water are added to the material after S5 calcination for granulation. After tabletting, a catalyst is obtained and used for the gas-phase hydrogenation of aldehyde to alcohol. In the metal solution in step S1, the concentration of zinc ions is 0.8 - 1.5 mol / L. In step S2, the concentration of aluminum ions in the metal solution is 0.05 - 0.12 mol / L; the concentration of the precipitant is 1.2 - 5 mol / L. In step S3, the concentration of the mixed metal salt solution is 1.1 - 1.6 mol / L, and the concentration of the basic precipitant is 0.5 - 2 mol / L. In step S2, the ionic mol ratio of the zinc salt solution to the aluminum salt solution is (11 - 14):1. In step S3, the ionic mol ratio of the copper salt solution to the zinc salt solution in the mixed metal salt solution is (1 - 3):1. In step S2, the coprecipitation temperature is from room temperature to 75 °C, the rotation speed is 200 - 500 rpm / min, the pH value at the end of coprecipitation is 8.5 - 10, and the aging time is 30 - 60 min. In step S3, the coprecipitation temperature is 60 - 90 °C, the rotation speed is 200 - 500 rpm / min, the pH value at the end of coprecipitation is 7.5 - 8.5, and the aging time is 1 - 2 h. The calcination temperature in step S4 is 350 - 400 °C, and the calcination time is 4 - 5 h. In this technical solution, the aluminum salt solution and the precipitant are dropped into the zinc salt solution in a co-current manner. In a high-concentration zinc salt environment, the solution pH is adjusted to precipitate aluminum preferentially, and zinc's strong driving force is used to embed the aluminum system during the precipitation process to complete coprecipitation until it is complete, greatly reducing the formation of single A12O3 and simultaneously reducing the possibility of forming CuA12O4 by adding copper salt later. The zinc component partially precipitated on the surface of the precipitate serves as a bridge and seed for the subsequent addition of the copper-zinc solution. When used in combination with additives, it improves the mass and heat transfer efficiency, reduces side reactions, and improves the heat resistance of the catalyst.

[0014] In this technical solution, the catalyst is prepared by using zinc salt, copper salt, and aluminum salt as raw materials and adjusting the precipitation priority order. The specific surface area of the catalyst is 60 - 100 m2 / g, the pore volume is 0.35 - 0.7 cm2 / g, and the average pore radius is 10 - 20 nm. There is no single alumina in the catalyst, and it has good thermal stability, reducing the content of high-boiling by-products and effectively improving the selectivity and stability of the gas-phase aldehyde hydrogenation reaction. Example 1

[0015] A catalyst for the gas-phase hydrogenation of octenal to alcohol, and its preparation method includes the following steps: First step: Dissolve 150 g of zinc nitrate hexahydrate in 350 mL of distilled water. After complete dissolution, put it into a reaction kettle with mechanical stirring, adjust the temperature to 70 °C, and set the rotation speed to 400 rpm / min.

[0016] Step 2: Dissolve 14 g of aluminum nitrate nonahydrate in 50 mL of distilled water to form an aluminum salt solution. Prepare a precipitant solution by dissolving 15 g of sodium carbonate and 5 g of sodium hydroxide in 100 mL of deionized water. Add the salt solution and the precipitant solution dropwise into the reaction kettle in parallel flow, and control the pH to 9.5 during this process; keep the rotation speed and precipitation temperature unchanged, and age for 30 min.

[0017] Step 3: Dissolve 100 g of copper nitrate trihydrate, 70 g of zinc nitrate hexahydrate and 10 g of silica sol in 350 mL of distilled water to prepare a mixed solution; dissolve 20 g of sodium carbonate in 150 mL of deionized water to prepare a precipitant solution. Add the mixed solution and the precipitant solution dropwise into the reaction kettle in the previous step in parallel flow, and control the pH to 8.5 during this process; raise the co-precipitation temperature to 75 °C, reduce the rotation speed to 200 rpm / min, and age for 1 h.

[0018] Step 4: Wash the aged material several times with deionized water, then perform suction filtration, and dry the obtained filter cake, grind it into powder, and calcine it at 380 °C for 4 h.

[0019] Step 5: Add 1.8 g of graphite and 10 mL of water to the calcined material for granulation and tabletting to obtain the gas-phase aldehyde hydrogenation catalyst. Example 2

[0020] A catalyst for the gas-phase hydrogenation of octenal to alcohol, and its preparation method includes the following steps: Step 1: Dissolve 173.25 g of zinc nitrate hexahydrate in 350 mL of distilled water. After complete dissolution, put it into a reaction kettle with mechanical stirring, adjust the temperature to 75 °C, and set the rotation speed to 350 rpm / min.

[0021] Step 2: Dissolve 3.94 g of sodium metaaluminate in 50 mL of distilled water to form an aluminum salt solution. Prepare a precipitant solution by dissolving 18 g of sodium carbonate in 100 mL of deionized water. Add the salt solution and the precipitant solution dropwise into the reaction kettle in parallel flow, and control the pH to 9 during this process; keep the rotation speed and precipitation temperature unchanged, and age for 30 min.

[0022] Step 3: Dissolve 118.5 g of copper nitrate trihydrate and 68.25 g of zinc nitrate hexahydrate in 350 mL of distilled water, add 1.2 g of SiC and stir evenly to prepare a mixed solution; dissolve 16 g of sodium carbonate in 150 mL of deionized water to prepare a precipitant solution. Add the mixed solution and the precipitant solution dropwise into the reaction kettle in the previous step in parallel flow, and control the pH to 8 during this process; lower the co-precipitation temperature to 70 °C, reduce the rotation speed to 250 rpm / min, and age for 1 h.

[0023] Step 4: Wash the aged material several times with deionized water, then perform suction filtration, and dry the obtained filter cake, grind it into powder, and calcine it at 370 °C for 4.5 h.

[0024] Step 5: Add 2.5 g of graphite and 20 mL of water to the calcined material, granulate and tablet it to obtain the gas-phase aldehyde hydrogenation catalyst.

[0025] Comparative Example 1 A catalyst for the gas-phase hydrogenation of octenal to alcohol, and its preparation method includes the following steps: Step 1: Dissolve 85.3 g of zinc nitrate hexahydrate and 50 g of aluminum nitrate nonahydrate in 200 mL of deionized water to prepare a first salt solution; dissolve 68 g of copper nitrate trihydrate, 42 g of zinc nitrate hexahydrate and 200 mL of deionized water to prepare a second salt solution; dissolve 18 g of sodium carbonate and 100 mL of deionized water to prepare a precipitant solution; Step 2: Add the first salt solution and the precipitant solution dropwise into a reaction kettle with mechanical stirring. During this period, control the pH to be about 9.5, the precipitation temperature to be 75 °C, the rotation speed to be 400 rpm / min. After the material titration is complete, maintain the temperature for aging for 30 min; Step 3: Add the second salt solution and the precipitant solution dropwise into the reaction kettle of the second step. During this period, control the pH to be about 8.5, the precipitation temperature to be 70 °C, the rotation speed to be 300 rpm / min. After the material titration is complete, maintain the temperature for aging for 1 h; Step 4: Wash the aged material several times with deionized water, then filter by suction, dry the obtained filter cake, grind it into powder, and calcine it at 360 °C for 4 h.

[0026] Step 5: Add 1.8 g of graphite and 10 mL of water to the calcined material, granulate and tablet it to obtain the gas-phase aldehyde hydrogenation catalyst.

[0027] Comparative Example 2 A catalyst for the gas-phase hydrogenation of octenal to alcohol, and its preparation method includes the following steps: Step 1: Dissolve 93.8 g of zinc nitrate hexahydrate in 150 mL of deionized water to prepare a mother liquor; dissolve 56 g of aluminum nitrate nonahydrate in 100 mL of deionized water to prepare a first salt solution; dissolve 81.6 g of copper nitrate trihydrate, 51.4 g of zinc nitrate hexahydrate and 250 mL of deionized water to prepare a second salt solution; dissolve 25 g of sodium carbonate and 150 mL of deionized water to prepare a precipitant solution; Step 2: Add the first salt solution and the precipitant solution dropwise into a reaction kettle containing the mother liquor. During this period, control the pH to be above 9, the precipitation temperature to be 75 °C, the rotation speed to be 380 rpm / min. After the material titration is complete, maintain the temperature for aging for 40 min; Step 3: Add the second salt solution and the precipitant solution dropwise into the reaction kettle of the second step. During this period, control the pH to be about 8, the precipitation temperature to be 70 °C, the rotation speed to be 300 rpm / min. After the material titration is complete, maintain the temperature for aging for 1.5 h; Step 4: Wash the aged material several times with deionized water, then perform suction filtration, dry the obtained filter cake, grind it into powder, and calcine it at 380 °C for 4 h.

[0028] Step 5: Add 2.2 g of graphite and 15 mL of water to the calcined material for granulation and tabletting to obtain the gas-phase aldehyde hydrogenation catalyst.

[0029] Apply the obtained catalyst to the reaction of octenal gas-phase hydrogenation to octanol. The reduction temperature of the catalyst is 230 °C, the reduction time is 10 h, the reduction pressure is 0.5 MPa, the reduction gas space velocity is 1000 h-1, the inlet temperature of the octenal hydrogenation reaction is 180 °C, the reaction pressure is 0.4 MPa, the liquid hourly space velocity of octenal is 0.3 h-1, and the molar ratio of hydrogen / octenal is 30. The results of the octenal hydrogenation reaction of the catalyst are as follows:

[0030] It can be seen that, compared with Comparative Examples 1 and 2 using the traditional distributed co-precipitation method, Examples 1 and 2 using the sequential precipitation method with zinc salt as the mother liquor have better selectivity and stability of the catalyst. This benefits from the optimization of the precipitation sequence. There is no separately existing alumina in the catalyst, which greatly weakens the acidity and dehydration of the catalyst, thus effectively inhibiting the side reactions. In addition, the addition of the promoter improves the heat transfer capacity of the catalyst, reduces the reaction hot spot temperature, reduces the generation of high-temperature by-products, and increases the octanol content.

[0031] The above is the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements or replacements can be made, and these improvements or replacements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for preparing alcohol by gas phase hydrogenation of octenal, characterized in that: The steps include: S1 first mixes a zinc source and water to prepare a zinc salt solution; S2. add the precipitant and the aluminum salt solution to the solution obtained in step S1 in parallel, mix them evenly, stir, keep warm, and age them until precipitation is complete; S3: adding the precipitant, the auxiliary agent and the mixed solution of copper salt and zinc salt to the mother liquor prepared in step S2 in parallel and dropping them, after mixing them evenly, stirring and keeping the materials warm to neutralize and age the materials; S4: washing and filtering the mature material in step S3, drying the obtained filter cake and calcining the powder at high temperature; S5: adding graphite and water to the calcined material for granulation, and obtaining a catalyst after tableting for gas phase aldehyde hydrogenation to alcohol; the concentration of zinc ions in the metal solution in step S1 is 0.8-1.5 mol / L; the concentration of aluminum ions in the metal solution in step S2 is 0.05-0.12 mol / L; the concentration of the precipitant is 1.2-5 mol / L; the concentration of the mixed metal salt solution in step S3 is 1.1-1.6 mol / L, and the concentration of the alkaline precipitant is 0.5-2 mol / L; the ion molar ratio of the zinc salt solution to the aluminum salt solution in step S2 is (11- 14):1; in step S3, the ion molar ratio of the copper salt solution and the zinc salt solution in the mixed metal salt solution is (1-3):1; in step S2, the coprecipitation temperature is room temperature-75°C, the rotation speed is 200-500rpm / min, the coprecipitation endpoint pH value is 8.5-10, and the aging time is 30-60min; in step S3, the coprecipitation temperature is 60-90°C, the rotation speed is 200-500rpm / min, the coprecipitation endpoint pH value is 7.5-8.5, and the aging time is 1-2h; the roasting temperature of step S4 is 350-400°C, and the roasting time is 4-5h.

2. The method for preparing a catalyst for preparing alcohol by gas phase hydrogenation of octenal according to claim 1, wherein: The zinc source is a mixture of one or more of zinc nitrate, zinc acetate and zinc chloride; the copper salt is a mixture of one or more of copper nitrate, copper acetate and copper chloride; the precipitant is any one or a mixture of several of sodium carbonate, sodium bicarbonate, sodium oxalate and sodium hydroxide; and the auxiliary agent is any one or a mixture of several of MgAl alloy powder, silica sol and SiC.

3. The catalyst prepared by the method for preparing a catalyst for preparing octenal by gas-phase hydrogenation of alcohol according to claim 1, characterized in that: In terms of mass percentage, the catalyst contains 30% to 36% of copper oxide, 58% to 64% of zinc oxide, 1% to 10% of aluminum oxide, 0.5% to 2.5% of an auxiliary agent, and 1% to 3% of graphite, and the total mass percentage is 100%.

4. The catalyst prepared by the method for preparing a catalyst for preparing octenal by gas-phase hydrogenation of alcohol according to claim 1, characterized in that: The specific surface area of ​​the catalyst is 60-100 m2 / g, the pore volume is 0.35-0.7 cm2 / g, and the average pore radius is 10-20 nm.

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