A Co / TiO 2 / Al 2 O 3 Preparation method of catalyst and its application in preparation of isooctanol by aldol condensation and hydrogenation of n-butanal

Abstract

The present invention belongs to the technical field of catalyst preparation, and specifically relates to a preparation method of a Co / TiO 2 / Al 2 O 3 catalyst and its application in the condensation hydrogenation of n-butanal to prepare isooctanol. Using Al 2 O 3 as the catalyst carrier, titanium and cobalt are simultaneously loaded under the condition that tannic acid is used as a chelating agent and a pH regulator, and the Co / TiO 2 / Al 2 O 3 catalyst is obtained after reduction treatment. When this catalyst is used to catalyze the condensation hydrogenation of n-butanal to prepare isooctanol, it not only has ideal catalytic activity, resulting in a high raw material conversion rate, but also exhibits good selectivity. It has good industrial prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method of a Co / TiO 2 / Al 2 O 3 catalyst and its application in the condensation hydrogenation of n-butyraldehyde to prepare isooctanol. Background Art

[0002] Isooctanol is a quite important chemical intermediate, which can mainly be used for producing plasticizers, and can also be used for producing octyl acrylate and its derivatives, and can also be used for producing lubricating oils and diesel additives, surfactants, pressure-sensitive adhesives, surface coatings, and defoaming agents and solvents used in the cosmetics industry, etc. It is a very widely used chemical auxiliary raw material and organic chemical raw material. Of course, it is also widely used in pesticides, pharmaceuticals, etc. At present, China's economy has developed rapidly, and isooctanol also plays an indispensable role.

[0003] The currently common preparation process of isooctanol in industry is the propylene oxo process: using propylene and syngas as raw materials, carbonyl synthesis occurs under the action of a catalyst to obtain a mixed butyraldehyde, and n-butyraldehyde is further purified from the mixed butyraldehyde. After n-butyraldehyde undergoes condensation dehydration, octenal is obtained, and finally catalytic hydrogenation generates the target product isooctanol. In this synthesis route, the step of generating isooctanol by the condensation hydrogenation of n-butyraldehyde is the key point of this route. Usually, the method is to first generate octenal by n-butyraldehyde under the action of a condensation catalyst, separate the octenal and generate isooctanol under the action of a hydrogenation catalyst. This method not only has cumbersome steps and large losses. In terms of catalysts, alumina is mostly used as the condensation catalyst, but during the reaction process, alumina undergoes hydrolysis and redeposits on the surface to form a boehmite structure, affecting the service life of the catalyst; at the same time, the degree of hydrogenation of octenal during the hydrogenation catalysis process is not easy to control. When the hydrogenation is insufficient, a diol structure is formed, and when the hydrogenation is excessive, the oxygen-containing group is removed in the form of water to generate a hydrocarbon group, resulting in unsatisfactory catalytic selectivity, and precious metal platinum is mostly used as the active metal in the hydrogenation catalyst, with a high cost. Summary of the Invention

[0004] To solve the above technical problems, the present application provides a preparation method of a Co / TiO 2 / Al 2 O 3 catalyst. The specific steps are as follows:

[0005] (1) Add urea in an amount of 0.8 to 1.5 times the weight of aluminum nitrate to the aqueous solution in which aluminum nitrate is dissolved and disperse it evenly, then carry out a hydrothermal reaction at 110°C to 140°C for 8 to 20 hours. After the reaction, filter, and dry the obtained filter cake;

[0006] (2) The dried filter cake obtained in step (1) is subjected to high-temperature treatment at 450 °C to 700 °C for 1 to 3 hours to obtain an Al 2 O 3 support;

[0007] (3) The Al 2 O 3 support is added to deionized water, and tannic acid, cobalt salt, and titanium source are added thereto. After sufficient mixing, filtration is carried out, and the obtained filter cake is dried. The mass ratio between the Al 2 O 3 support, tannic acid, cobalt salt, and titanium source is 10:5 to 20:1 to 2.5:20 to 40;

[0008] (4) The filter cake obtained in step (3) is heat-treated in an air atmosphere at 300 °C to 500 °C for 1 to 2 hours, and then reduced in hydrogen at 400 °C to 600 °C for 1 to 2 hours to obtain a Co / TiO 2 / Al 2 O 3 catalyst.

[0009] Further, in step (1), aluminum nitrate is aluminum nitrate nonahydrate, and the content of aluminum nitrate dissolved in the aqueous solution is 0.01 to 0.1 g / mL, and the drying is carried out by drying at 80 °C to 120 °C for 5 to 15 hours.

[0010] Further, in step (3), the Al 2 O 3 support is added to deionized water at 0.01 to 0.15 g / mL, and the drying is carried out by drying at 80 °C to 120 °C for 5 to 15 hours.

[0011] In addition, in step (3), the cobalt salt is anhydrous cobalt chloride, cobalt acetate tetrahydrate or cobalt chloride hexahydrate, and the titanium source is tetrabutyl titanate.

[0012] The present application also provides an application of the Co / TiO 2 / Al 2 O 3 catalyst prepared by the above method. The Al 2 O 3 simultaneously serves as a support for both the condensation catalyst and the hydrogenation catalyst, and uses transition metal cobalt as the hydrogenation active center to catalytically synthesize isooctanol by one-pot condensation hydrogenation of n-butyraldehyde,

[0013] Further, Co / TiO 2 / Al 2 O 3The dosage of the catalyst is 0.15 wt% - 0.3 wt% of n-butanal. In the catalytic reaction, first react at 150 °C - 180 °C in a nitrogen atmosphere for 5 - 8 hours. After introducing hydrogen to displace nitrogen and controlling the pressure to reach 2.5 - 3.5 MPa, continue the reaction for 5 - 8 hours.

[0014] The advantages of this application are as follows:

[0015] Using urea as a precipitant, the support Al 2 O 3 is synthesized by the hydrothermal method. During the hydrothermal process, urea slowly releases ammonium, adjusting the pH of the system to be alkaline. Since the pH changes slowly, aluminum is fully precipitated.

[0016] During the loading process of the active metal in this application, the added tannic acid makes the reaction system acidic, thereby catalyzing the slow hydrolysis of tetrabutyl titanate to form TiO 2 ; and the abundant oxygen-containing functional groups on tannic acid have a strong chelating effect on metal elements. Therefore, although the acidity of the tannic acid aqueous solution is not conducive to the hydrolysis and deposition of cobalt ions, using tannic acid as a bridging molecule to chelate and connect cobalt ions to the titanium dioxide or alumina support also avoids the separation of cobalt ions from the support by being free in the filtrate during filtration.

[0017] At the same time, the chelating and bridging effect of tannic acid is beneficial to enhancing the interaction between active cobalt, titanium dioxide, and the support, promoting the uniformity and stability of the loading.

[0018] When the alumina support participates in the hydrogenation catalytic reaction, the inherent acidity of the alumina will affect the active center cobalt, thus easily causing excessive hydrogenation and reducing the catalytic selectivity. In this regard, in this application, titanium and cobalt are simultaneously loaded. It is equivalent to titanium carrying the active center cobalt for deposition and distribution, making the cobalt as the active center uniformly distributed in the titanium dioxide environment on the support surface. Through the influence and protection of titanium dioxide on the active center cobalt, and reducing the amount of cobalt directly loaded on the alumina surface, the acidity near the active center cobalt of hydrogenation can be effectively and accurately adjusted, effectively suppressing the problem of excessive hydrogenation and increasing the content of isooctanol in the product.

[0019] At the same time, compared with the bare alumina support on the surface, after deposition and distribution on the alumina support surface, it can also reduce the formation of the boehmite structure due to the hydrolysis of alumina.

[0020] During the subsequent heat treatment process, consciously avoid the temperature being too high to reach the temperature for forming the cobalt-aluminum spinel structure, so that metallic cobalt can better stay on titanium dioxide, thereby avoiding the influence of the catalytic acidity of alumina on the active center cobalt due to the incorporation or proximity of cobalt to the alumina support. Detailed implementation mode

[0021] A Co / TiO2 / Al 2 O 3 The preparation method of the catalyst comprises the following specific steps:

[0022] (1) adding urea in an amount of 0.8 to 1.5 times the weight of the aluminum nitrate to an aqueous solution containing aluminum nitrate and dispersing the mixture uniformly, subjecting the mixture to a hydrothermal reaction at 110° C. to 140° C. for 8 to 20 hours, filtering the mixture after the reaction, and drying the resulting filter cake;

[0023] The aluminum nitrate is aluminum nitrate nonahydrate, the content of aluminum nitrate dissolved in the aqueous solution is 0.01-0.1 g / mL, and the drying is carried out at 80° C.-120° C. for 5-15 hours;

[0024] (2) The dried filter cake in step (1) is subjected to a high temperature treatment at 450°C to 700°C for 1 to 3 hours to obtain Al 2 O 3 Carrier;

[0025] (3) Al in step (2) 2 O 3 The carrier is added to deionized water, and tannic acid, cobalt salt and titanium source are added thereto, mixed thoroughly and filtered, and the obtained filter cake is dried. 2 O 3 The mass ratio of the carrier, tannic acid, cobalt salt and titanium source is 10:5-20:1-2.5:20-40. In the dried filter cake, the cobalt ions are complexed with tannic acid and bridged with titanium oxide and aluminum oxide through tannic acid.

[0026] Among them, Al 2 O 3 The carrier is added to deionized water at 0.01-0.15 g / mL, the cobalt salt is anhydrous cobalt chloride, cobalt acetate tetrahydrate or cobalt chloride hexahydrate, the titanium source is tetrabutyl titanate, and the drying is carried out at 80° C.-120° C. for 5-15 hours;

[0027] (4) The filter cake obtained in step (3) is heat treated in an air atmosphere at 300°C to 500°C for 1 to 2 hours, and then reduced in hydrogen at 400°C to 600°C for 1 to 2 hours to obtain Co / TiO 2 / Al 2 O 3 Catalyst, after heat treatment in air, tannic acid is decomposed and removed, cobalt ions are converted into oxides, and after hydrogen reduction, it becomes elemental cobalt.

[0028] Specific examples are as follows:

[0029] Example 1

[0030] (1) After adding 12 g of aluminum nitrate nonahydrate to 800 mL of deionized water and stirring until dissolved, 12 g of urea was added thereto. After stirring for 30 min, the obtained clear solution was added to a hydrothermal reactor and left to stand in an oven at 120 °C for 12 h, and then naturally cooled to room temperature (25 °C, the same hereinafter) with the furnace. After suction filtration, the obtained filter cake was dried in an oven at 80 °C for 12 hours;

[0031] (2) After subjecting the dried filter cake in step (1) to high-temperature treatment at 500 °C in a muffle furnace for 2 h, it was naturally cooled to room temperature with the furnace to obtain a white solid powder;

[0032] (3) After adding 1 g of the white solid powder obtained in step (2) to 100 mL of deionized water and ultrasonicating for 30 min, 1 g of tannic acid, 0.15 g of anhydrous cobalt chloride, and 3 g of tetrabutyl titanate were successively added thereto. After stirring at room temperature for 3 h, suction filtration separation was carried out, and the obtained filter cake was dried in an oven at 80 °C for 12 hours;

[0033] (4) The dried filter cake in step (3) was placed in a muffle furnace. First, it was heat-treated at 400 °C in an air atmosphere for 2 h, and after naturally cooling to room temperature, it was then heat-treated at 450 °C in a hydrogen atmosphere for 2 h. After naturally cooling to room temperature, Co / TiO 2 / Al 2 O 3 catalyst was obtained.

[0034] Example 2

[0035] (1) After adding 160 g of aluminum nitrate nonahydrate to 1600 mL of deionized water and stirring until dissolved, 240 g of urea was added thereto. After stirring for 90 min, the obtained clear solution was added to a hydrothermal reactor and left to stand in an oven at 140 °C for 20 h, and then naturally cooled to room temperature with the furnace. After suction filtration, the obtained filter cake was dried in an oven at 120 °C for 5 hours;

[0036] (2) After subjecting the dried filter cake in step (1) to high-temperature treatment at 700 °C in a muffle furnace for 1 h, it was naturally cooled to room temperature with the furnace to obtain a white solid powder;

[0037] (3) After adding 15 g of the white solid powder obtained in step (2) to 100 mL of deionized water and ultrasonicating for 100 min, 20 g of tannic acid, 3.5 g of cobalt nitrate hexahydrate, and 40 g of tetrabutyl titanate were successively added thereto. After stirring at room temperature for 7 h, suction filtration separation was carried out, and the obtained filter cake was dried in an oven at 120 °C for 8 hours;

[0038] (4) The dried filter cake in step (3) was placed in a muffle furnace. First, it was heat-treated at 500 °C in an air atmosphere for 2 h, and after naturally cooling to room temperature, it was then heat-treated at 450 °C in a hydrogen atmosphere for 2 h. After naturally cooling to room temperature, Co / TiO 2 / Al2 O 3 Catalyst.

[0039] Example 3

[0040] (1) After adding 12 g of aluminum nitrate nonahydrate to 800 mL of deionized water and stirring until dissolved, 12 g of urea was added thereto. After stirring for 30 min, the obtained clear solution was added to a hydrothermal reactor and left standing in an oven at 120 °C for 12 h, then naturally cooled to room temperature in the furnace, filtered by suction, and the obtained filter cake was dried in an oven at 80 °C for 12 hours;

[0041] (2) After subjecting the dried filter cake in step (1) to high-temperature treatment at 500 °C in a muffle furnace for 2 h, it was naturally cooled to room temperature in the furnace to obtain a white solid powder;

[0042] (3) After adding 1 g of the white solid powder obtained in step (2) to 100 mL of deionized water and ultrasonicating for 30 min, 2 g of tannic acid, 0.15 g of cobalt chloride anhydrous, and 3 g of tetrabutyl titanate were successively added thereto. After stirring at room temperature for 3 h, it was separated by suction filtration, and the obtained filter cake was dried in an oven at 80 °C for 12 hours;

[0043] (4) The dried filter cake in step (3) was placed in a muffle furnace, first heat-treated at 400 °C in an air atmosphere for 2 h, naturally cooled to room temperature, and then heat-treated at 450 °C in a hydrogen atmosphere for 2 h. After naturally cooling to room temperature, Co / TiO 2 / Al 2 O 3 Catalyst.

[0044] Example 4

[0045] (1) After adding 160 g of aluminum nitrate nonahydrate to 1600 mL of deionized water and stirring until dissolved, 240 g of urea was added thereto. After stirring for 90 min, the obtained clear solution was added to a hydrothermal reactor and left standing in an oven at 140 °C for 20 h, then naturally cooled to room temperature in the furnace, filtered by suction, and the obtained filter cake was dried in an oven at 120 °C for 5 hours;

[0046] (2) After subjecting the dried filter cake in step (1) to high-temperature treatment at 700 °C in a muffle furnace for 1 h, it was naturally cooled to room temperature in the furnace to obtain a white solid powder;

[0047] (3) After adding 15 g of the white solid powder obtained in step (2) to 100 mL of deionized water and ultrasonicating for 100 min, 7.5 g of tannic acid, 3.5 g of cobalt nitrate hexahydrate, and 40 g of tetrabutyl titanate were successively added thereto. After stirring at room temperature for 7 h, it was separated by suction filtration, and the obtained filter cake was dried in an oven at 120 °C for 8 hours;

[0048] (4) Put the dried filter cake in step (3) into a muffle furnace, first heat-treat it at 500 °C for 2 h in an air atmosphere, naturally cool it to room temperature, and then heat-treat it at 450 °C for 2 h in a hydrogen atmosphere. After naturally cooling to room temperature, Co / TiO 2 / Al 2 O 3 catalyst is obtained.

[0049] Comparative Example 1

[0050] Without adding a titanium source, and the rest of the operations are the same as in Example 1:

[0051] (1) Add 12 g of aluminum nitrate nonahydrate to 800 mL of deionized water, stir to dissolve it, add 12 g of urea to it, stir for 30 min, then add the obtained clear solution to a hydrothermal kettle and let it stand in an oven at 120 °C for 12 h, and then naturally cool it to room temperature with the furnace. Filter by suction, and dry the obtained filter cake in an oven at 80 °C for 12 hours;

[0052] (2) Heat-treat the dried filter cake in step (1) in a muffle furnace at 500 °C for 2 h, and then naturally cool it to room temperature with the furnace to obtain a white solid powder;

[0053] (3) Add 1 g of the white solid powder obtained in step (2) to 100 mL of deionized water, ultrasonically treat it for 30 min, then successively add 1 g of tannic acid and 0.15 g of anhydrous cobalt chloride to it, stir at room temperature for 3 h, then filter and separate, and dry the obtained filter cake in an oven at 80 °C for 12 hours;

[0054] (4) Put the dried filter cake in step (3) into a muffle furnace, first heat-treat it at 400 °C for 2 h in an air atmosphere, naturally cool it to room temperature, and then heat-treat it at 450 °C for 2 h in a hydrogen atmosphere. After naturally cooling to room temperature, Co / Al 2 O 3 catalyst is obtained.

[0055] Comparative Example 2

[0056] First deposit titanium dioxide, and then deposit cobalt ions by hydrolysis. The rest of the operations are the same as in Example 1:

[0057] (1) Add 12 g of aluminum nitrate nonahydrate to 800 mL of deionized water, stir to dissolve it, add 12 g of urea to it, stir for 30 min, then add the obtained clear solution to a hydrothermal kettle and let it stand in an oven at 120 °C for 12 h, and then naturally cool it to room temperature with the furnace. Filter by suction, and dry the obtained filter cake in an oven at 80 °C for 12 hours;

[0058] (2) Heat-treat the dried filter cake in step (1) in a muffle furnace at 500 °C for 2 h, and then naturally cool it to room temperature with the furnace to obtain a white solid powder;

[0059] (3) Add 1 g of the white solid powder obtained in step (2) to 100 mL of deionized water, ultrasonicate for 30 min, then successively add 1 g of tannic acid and 3 g of tetrabutyl titanate thereto, stir at room temperature for 3 h, perform suction filtration to separate, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0060] (4) Add the dried filter cake in step (3) to 100 mL of deionized water, ultrasonicate for 30 min, then successively add 1 g of tannic acid and 0.15 g of anhydrous cobalt chloride thereto, stir at room temperature for 3 h, perform suction filtration to separate, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0061] (5) Put the dried filter cake in step (4) into a muffle furnace, first heat-treat it at 400 °C for 2 h in an air atmosphere, naturally cool to room temperature, then heat-treat it at 450 °C for 2 h in a hydrogen atmosphere, and naturally cool to room temperature to obtain Co / TiO 2 / Al 2 O 3 catalyst.

[0062] Comparative Example 3

[0063] Hydrolyze and deposit titanium dioxide and aluminum oxide together as the support, and the remaining operations are the same as in Example 1:

[0064] (1) Add 12 g of aluminum nitrate nonahydrate and 4.9 g of tetrabutyl titanate to 800 mL of deionized water, stir to dissolve, then add 12 g of urea thereto, stir for 30 min, add the obtained clear solution to a hydrothermal kettle, and let it stand in an oven at 120 °C for 12 h, then naturally cool to room temperature with the furnace, perform suction filtration, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0065] (2) Heat-treat the dried filter cake in step (1) at 500 °C in a muffle furnace for 2 h, then naturally cool to room temperature with the furnace to obtain a white solid powder;

[0066] (3) Add 1.7 g of the white solid powder obtained in step (2) to 100 mL of deionized water, ultrasonicate for 30 min, then successively add 1 g of tannic acid and 0.15 g of anhydrous cobalt chloride thereto, stir at room temperature for 3 h, perform suction filtration to separate, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0067] (4) Put the dried filter cake in step (3) into a muffle furnace, first heat-treat it at 400 °C for 2 h in an air atmosphere, naturally cool to room temperature, then heat-treat it at 450 °C for 2 h in a hydrogen atmosphere, and naturally cool to room temperature to obtain Co / TiO 2 / Al 2 O 3 catalyst.

[0068] Comparative Example 4

[0069] Replace the tannic acid in Example 1 with citric acid of equal mass, and the remaining operations are the same as in Example 1:

[0070] (1) Add 12 g of aluminum nitrate nonahydrate to 800 mL of deionized water, stir to dissolve, then add 12 g of urea, stir for 30 min, add the resulting clear solution to a hydrothermal reactor, and let it stand in an oven at 120 °C for 12 h, then cool naturally to room temperature with the furnace, filter by suction, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0071] (2) Heat-treat the dried filter cake in step (1) in a muffle furnace at 500 °C for 2 h, then cool naturally to room temperature with the furnace to obtain a white solid powder;

[0072] (3) Add 1 g of the white solid powder obtained in step (2) to 100 mL of deionized water, sonicate for 30 min, then sequentially add 1 g of citric acid, 0.15 g of anhydrous cobalt chloride, and 3 g of tetrabutyl titanate, stir at room temperature for 3 h, then filter by suction to separate, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0073] (4) Put the dried filter cake in step (3) into a muffle furnace, first heat-treat it in an air atmosphere at 400 °C for 2 h, cool naturally to room temperature, then heat-treat it in a hydrogen atmosphere at 450 °C for 2 h, and after naturally cooling to room temperature, obtain Co / TiO 2 / Al 2 O 3 catalyst.

[0074] Comparative Example 5

[0075] Increase the subsequent heat treatment temperature, and the remaining operations are the same as in Example 1:

[0076] (1) Add 12 g of aluminum nitrate nonahydrate to 800 mL of deionized water, stir to dissolve, then add 12 g of urea, stir for 30 min, add the resulting clear solution to a hydrothermal reactor, and let it stand in an oven at 120 °C for 12 h, then cool naturally to room temperature (25 °C, the same below) with the furnace, filter by suction, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0077] (2) Heat-treat the dried filter cake in step (1) in a muffle furnace at 500 °C for 2 h, then cool naturally to room temperature with the furnace to obtain a white solid powder;

[0078] (3) Add 1 g of the white solid powder obtained in step (2) to 100 mL of deionized water, ultrasonicate for 30 min, then successively add 1 g of tannic acid, 0.15 g of anhydrous cobalt chloride, and 3 g of tetrabutyl titanate thereto, stir at room temperature for 3 h, perform suction filtration and separation, and dry the obtained filter cake in an oven at 80 °C for 12 h;

[0079] (4) Put the dried filter cake in step (3) into a muffle furnace, first perform heat treatment at 650 °C for 2 h in an air atmosphere, naturally cool to room temperature, then perform heat treatment at 450 °C for 2 h in a hydrogen atmosphere, and obtain Co / TiO 2 / Al 2 O 3 catalyst after natural cooling to room temperature.

[0080] Determine the total acid content of the catalysts prepared in the above examples and comparative examples by NH 3 -TPD method respectively;

[0081] Detect the catalytic activity and selectivity of the catalysts prepared in the above examples and comparative examples through application tests. The detection operation is as follows: Add the catalyst to a high-pressure reaction kettle together with n-butanal at 0.15 wt% of the mass of n-butanal and mix well. After replacing the air in the high-pressure reaction kettle with nitrogen 3 times, carry out a condensation reaction at 180 °C for 5 h in a nitrogen atmosphere (one atmospheric pressure), then introduce hydrogen to replace the nitrogen in the high-pressure reaction kettle and control the pressure in the high-pressure reaction kettle to reach 3 MPa, and then maintain a hydrogenation reaction at 180 °C for 6 h. After the reaction is completed, naturally cool to room temperature, open the kettle to sample and analyze the product composition by gas chromatography, and calculate the raw material conversion rate and product selectivity.

[0082] Conversion rate = 100% * (m in -m out ) / m in ; Selectivity = 2 * 100% * M butanal *m isooctanol / [(m in -m out ) * M isooctanol ,

[0083] wherein, m in is the mass of n-butanal added to the high-pressure reaction kettle;

[0084] m out is the mass of n-butanal analyzed and detected from the product system after the catalytic reaction;

[0085] M butanal is the molecular weight of n-butanal;

[0086] M isooctanol is the molecular weight of isooctanol;

[0087] m isooctanol It is the mass of isooctanol analyzed and detected from the product system after the catalytic reaction ends.

[0088] The results are shown in the following table.

[0089]

[0090] As can be seen from the above table, for Examples 1 to 4 of the present solution, both the catalytic conversion rate and selectivity are relatively ideal.

[0091] Compared with Example 1, in Comparative Example 1, when titanium dioxide was not introduced, the carrier alumina was in direct contact with the active center cobalt, resulting in too high catalytic acidity, excessive catalytic hydrogenation, and greatly affecting the selectivity of the target product.

[0092] Compared with Example 1, in Comparative Example 2, titanium and cobalt were deposited on the carrier successively. Compared with Example 1, it could not ensure that all cobalt was loaded on or near titanium dioxide, and the cobalt directly loaded on alumina was affected by alumina, resulting in excessive hydrogenation.

[0093] Compared with Example 1, in Comparative Example 3, after titanium dioxide was dispersed in the catalyst carrier, the connection between titanium dioxide and the subsequently loaded active center cobalt became smaller, and the protection effect on the active center cobalt decreased.

[0094] Compared with Example 1, the effect of Comparative Example 4 decreased. This may be because when citric acid adjusted the pH to control the hydrolysis of the titanium source and played a chelating bridging role for metal elements, the control of the loading uniformity of titanium and cobalt was not as good as that of tannic acid.

[0095] Compared with Example 1, in Comparative Example 5, after the heat treatment temperature increased, the catalyst as a whole tended to transform into a spinel structure, making the cobalt in the catalyst more incorporated into or closer to the alumina carrier, resulting in cobalt being more significantly affected by the catalytic acidity of alumina, increasing the catalytic acidity and causing excessive hydrogenation.

Claims

1. A preparation method of Co / TiO 2 / Al 2 O 3 catalyst It is characterized in that: The steps of the preparation method are as follows: (1) After adding urea which is 0.8 - 1.5 times the weight of aluminum nitrate to the aqueous solution in which aluminum nitrate is dissolved and dispersing evenly, perform hydrothermal reaction at 110°C - 140°C for 8 - 20 hours. After the reaction, filter and dry the obtained filter cake; (2) The dried filter cake in step (1) is subjected to high-temperature treatment at 450°C to 700°C for 1 to 3 hours to obtain an Al 2 O 3 support; (3) Add the Al in step (2) 2 O 3 carrier to deionized water, add tannic acid, cobalt salt, and titanium source thereto, filter after sufficient mixing, and dry the obtained filter cake. The mass ratio among the Al 2 O 3 carrier, tannic acid, cobalt salt, and titanium source is 10:5-20:1-2.5:20-40; (4) The filter cake obtained in step (3) is heat-treated at 300 °C to 500 °C for 1 to 2 hours in an air atmosphere, and then reduced at 400 °C to 600 °C in hydrogen for 1 to 2 hours to obtain Co / TiO 2 / Al 2 O 3 catalyst.

2. The preparation method of the Co / TiO 2 / Al 2 O 3 catalyst as claimed in claim 1, It is characterized in that: In the aqueous solution described in step (1), the content of aluminum nitrate is 0.01 - 0.1 g / mL.

3. The preparation method of the Co / TiO 2 / Al 2 O 3 catalyst as claimed in claim 1 It is characterized in that: The drying described in step (1) is drying at 80°C - 120°C for 5 - 15 hours.

4. The preparation method of the Co / TiO 2 / Al 2 O 3 catalyst It is characterized in that: In step (3), the Al 2 O 3 carrier is added to the deionized water at 0.01 - 0.15 g / mL.

5. The preparation method of the Co / TiO 2 / Al 2 O 3 catalyst It is characterized in that: The drying described in step (3) is drying at 80°C - 120°C for 5 - 15 hours.

6. Use of a Co / TiO 2 / Al 2 O 3 catalyst prepared by the method according to any one of claims 1 to 5, It is characterized in that: The application is to catalyze the condensation hydrogenation of n-butanal to prepare isooctanol.

7. Use of the Co / TiO 2 / Al 2 O 3 catalyst, It is characterized in that: The Co / TiO 2 / Al 2 O 3 The dosage of the catalyst is 0.15 wt% - 0.3 wt% of the n-butanal. In the catalytic reaction, first react at 150°C - 180°C for 5 - 8 hours in a nitrogen atmosphere, then introduce hydrogen to displace the nitrogen and control the pressure to reach 2.5 - 3.5 MPa, and then continue to react for 5 - 8 hours.

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