A catalyst for dehydrating n-decyl alcohol to produce 1-decene, and its preparation and application

Abstract

The invention discloses a catalyst for preparing 1-decene by dehydrating n-decyl alcohol and a preparation method thereof. The catalyst is composed of (Al2O3@SiO2) / SiO2, in which nano Al2O3 particles of a dehydration active component mediated by high-toughness silica gel are assembled in SiO2 pores. The catalyst provided by the invention exhibits excellent catalytic activity, target product 1-decene selectivity and long-term stability in the reaction of preparing 1-decene by dehydrating n-decyl alcohol, and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a catalyst for dehydrating n-decyl alcohol to prepare 1-decene and a preparation method thereof. Background Art

[0002] As a widely used synthetic hydrocarbon-based lubricant, polyalphaolefin synthetic oil (PAO) has far superior performance to traditional mineral lubricants. Its current output accounts for about 45% of the world's synthetic lubricant market share. At present, the annual consumption of polyalphaolefin base oil in China is 40,000 to 50,000 tons, of which more than 80% is imported. The catalytic polymerization and hydrogenation saturation of 1-decene are important ways to produce PAO synthetic oil. At present, there are many methods for producing 1-decene. In industry, the main production process abroad is ethylene polymerization, and the resulting product has good quality and high purity, but the cost is high; the domestic production is mainly based on the relatively low-cost paraffin cracking process, but because its reaction mechanism is relatively complex and the operating conditions are relatively strict, the resulting product quality is poor and the purity is low, so it does not have an advantage in market economic benefits, resulting in my country's 1-decene being heavily dependent on imports. In order to solve the bottleneck problem of 1-decene, it is urgent to develop a new and efficient 1-decene synthesis route. The method of generating high-carbon alcohols, especially n-decanol, through coal-based Fischer-Tropsch reaction and then generating 1-decene through dehydration reaction of n-decanol can greatly simplify the process flow, with small investment, flexible production and huge economic advantages.

[0003] Solid acid catalysts, such as molecular sieves, heteropoly acids, and alumina, are usually used for the dehydration of alcohols to produce olefins, and oxide catalysts are usually used for the dehydration of high-carbon alcohols. Reference (Chemistry and Adhesion, 2013, 35, 44-46) selected Ba and H / γ-Al2O3 as catalysts for the dehydration of fatty alcohols. At a reaction temperature of 310°C, the selectivity of C8 and C8 / C10 fatty alcohol olefins reached the maximum values ​​of 98.1% and 97.5%, respectively. Reference (Modern Chemical Industry, 2013, 42, 275-277) used Nb2O5 as a catalyst and utilized the principle of dehydrating fatty alcohols to produce olefins to dehydrate C10 fatty alcohols to produce α-C10 olefins. At a reaction temperature of 290°C, the fatty alcohols were most thoroughly dehydrated, and the maximum conversion rate of the obtained fatty alcohols was 94%. However, the preparation process of Nb2O5 catalyst is complicated and the production cost is high. Chinese patent CN112898109 A uses alumina modified by a specific alkali metal as a catalyst to dehydrate high-carbon alcohol raw materials to generate α-high-carbon olefins. Under optimized reaction conditions, the conversion rate of α-high-carbon alcohol is above 99%. Although the modified alumina catalyst has high activity for the dehydration reaction of n-decyl alcohol, the polymerization-grade decene required for PAO requires a high purity of 1-decene, and the selectivity of the dehydration target product 1-decene of the catalyst currently developed still needs to be improved. Conventional alumina has a small pore size (<10nm), and the generated 1-decene cannot be desorbed in time during the catalytic dehydration reaction of n-decyl alcohol, and is prone to secondary reactions on the acid center to generate isomeric 2-decene, etc. In addition, 1-decene undergoes polymerization reaction on the acid center to generate carbon deposits that block and deactivate the catalyst. The present invention uses macroporous silica as a carrier and distributes nano-active alumina in an inert SiO2 gel network through the mediation of high-toughness silica gel, so that the target product 1-decene generated by the reaction can be desorbed in time, avoiding secondary reactions or carbon deposition on the acid active center, thereby improving the selectivity and stability of the catalyst. Summary of the invention

[0004] The invention discloses a catalyst for preparing 1-decene by dehydrating n-decyl alcohol and a preparation method thereof. Compared with the prior art, the invention can significantly improve the selectivity of 1-decene and significantly enhance the stability of the catalyst.

[0005] The content of the present invention is elaborated in detail below:

[0006] The catalyst composition of the present invention is (Al2O3@SiO2) / SiO2, acidic small-particle silica sol and aluminum nitrate are co-impregnated in a macroporous silica gel carrier, sealed and aged, and at a certain temperature, after a certain period of time, the acidic silica sol will form a gel with strong toughness and strength, and the aluminum nitrate is confined in situ therein, and after subsequent drying and roasting, the dehydrated active component nano Al2O3 particles are assembled in the SiO2 pores. Calculated based on the overall mass of the catalyst, the mass content of Al2O3 is 10.0% to 20.0% (preferably 10.0%-15.0%), the molar ratio of silicon in the SiO2 carrier used for confinement to aluminum in the active component is 0.1-0.5 (preferably 0.2-0.4), and the rest is SiO2 carrier.

[0007] The preparation method of the above catalyst comprises the following steps:

[0008] (1) Aluminum nitrate is prepared into an aqueous solution with a mass concentration of 30%-70%, and the pH value is adjusted to 2-3 with nitric acid with a mass concentration of 20%-40%, and a certain amount of small-particle acidic silica sol is added while stirring.

[0009] (2) The macroporous SiO2 carrier is impregnated with an equal volume of the impregnation solution prepared in step (1), and allowed to stand for 1-2 hours after impregnation. The carrier is then placed in a sealed oven and aged at 50-70°C for 5-10 hours to allow the acidic silica sol to form a gel network with certain toughness and rigidity in the macropores of the carrier.

[0010] (3) The solid particles prepared in step (2) are placed in a ventilated oven and dried at 80-100° C. to precipitate aluminum nitrate into nanocrystals under the confinement conditions of the silica hydrogel. The solid particles are then calcined in a muffle furnace at 400-600° C. for 3-6 hours to decompose the nano aluminum nitrate crystals in the silica gel into Al2O3, thereby obtaining the desired catalyst (Al2O3@SiO2) / SiO2.

[0011] The acidic silica sol in step (1) has a pH of 3-4, a particle size of 1-3 nm, and a silicon oxide solid content of 10%-20%.

[0012] The carrier in step (2) is a macroporous SiO2 carrier with an average pore size greater than or equal to 20 nm, preferably 20-80 nm.

[0013] The catalyst composition of the present invention is (Al2O3@SiO2) / SiO2, in which the high-toughness silica gel-mediated dehydration active component nano Al2O3 particles are assembled in the SiO2 pores. The catalyst provided by the present invention exhibits excellent catalytic activity, target product 1-decene selectivity and long-term stability in the reaction of dehydration of n-decyl alcohol to 1-decene, and has broad application prospects. DETAILED DESCRIPTION

[0014] The following examples are used to further illustrate the present invention, but the present invention is not limited to these examples.

[0015] Example 1

[0016] Weigh 14.72g Al(NO3)·9H2O, dissolve in 15ml deionized water, adjust pH=2 with 20% dilute nitric acid, add 4.71g acidic silica sol with 10% silicon oxide solid content while stirring, the particle size of SiO2 in the acidic silica sol is 1-2nm, and the pH is 3.5 (the same below). Use the above-prepared impregnation solution to impregnate 17.53g macroporous SiO2 carrier, the average pore size of the macroporous SiO2 carrier is 25nm. Let it stand for 1 hour, put it in a closed oven, age it at 50℃ for 6 hours, then put it in a blast oven, dry it at 80℃ for 7 hours, and roast it at 500℃ in a muffle furnace for 3 hours to obtain the required catalyst (Al2O3@SiO2) / SiO2-1.

[0017] Example 2

[0018] Weigh 14.72g Al(NO3)·9H2O, dissolve in 10ml deionized water, adjust pH=2 with 40% nitric acid, add 9.42g acidic silica sol with 10% silicon oxide solid content while stirring, the particle size of SiO2 in the acidic silica sol is 1-2nm. Use the above-prepared impregnation solution to impregnate 17.06g macroporous SiO2 carrier, the average pore size of the macroporous SiO2 carrier is 25nm. Let it stand for 1 hour, put it in a closed oven, age it at 50℃ for 6 hours, then put it in a blast oven, dry it at 90℃ for 7 hours, and roast it at 600℃ in a muffle furnace for 7 hours to obtain the required catalyst (Al2O3@SiO2) / SiO2-2.

[0019] Example 3

[0020] Weigh 14.72g Al(NO3)·9H2O, dissolve in 10ml deionized water, adjust pH=2 with 30% nitric acid, add 4.71g acidic silica sol with 20% silicon oxide solid content while stirring, the particle size of SiO2 in the acidic silica sol is 2-3nm. Use the above-prepared impregnation solution to impregnate 17.06g macroporous SiO2 carrier, the average pore size of the macroporous SiO2 carrier is 25nm. Let it stand for 1 hour, put it in a closed oven, age it at 50℃ for 6 hours, then put it in a blast oven, dry it at 100℃ for 7 hours, and roast it at 500℃ in a muffle furnace for 4 hours to obtain the required catalyst (Al2O3@SiO2) / SiO2-3.

[0021] Example 4

[0022] Weigh 14.72g Al(NO3)·9H2O, dissolve in 10ml deionized water, adjust pH=2 with 30% nitric acid, add 9.42g acidic silica sol with 10% silicon oxide solid content while stirring, the particle size of SiO2 in the acidic silica sol is 1-2nm. Use the above prepared impregnation solution to impregnate 17.06g macroporous SiO2 carrier, the average pore size of the macroporous SiO2 carrier is 35nm. Let it stand for 1 hour, put it in a closed oven, age it at 65℃ for 6 hours, then put it in a blast oven, dry it at 80℃ for 5 hours, and roast it at 500℃ in a muffle furnace for 3 hours to obtain the required catalyst (Al2O3@SiO2) / SiO2-4.

[0023] Example 5

[0024] Weigh 22.08g Al(NO3)·9H2O, dissolve in 11ml deionized water, adjust pH=3 with 40% nitric acid, add 7.07g acidic silica sol with 10% silicon oxide solid content while stirring, the particle size of SiO2 in the acidic silica sol is 2-3nm. Use the above-prepared impregnation solution to impregnate 16.29g macroporous SiO2 carrier, the average pore size of the macroporous SiO2 carrier is 35nm. Let it stand for 1 hour, put it in a closed oven, age it at 70℃ for 6 hours, then put it in a blast oven, dry it at 80℃ for 7 hours, and roast it at 600℃ in a muffle furnace for 3 hours to obtain the required catalyst (Al2O3@SiO2) / SiO2-5.

[0025] Example 6

[0026] Weigh 22.08g Al(NO3)·9H2O, dissolve in 11ml deionized water, adjust pH=2 with 40% nitric acid, add 7.07g acidic silica sol with 20% solid content of silicon oxide while stirring, the particle size of SiO2 in the acidic silica sol is 1-2nm. Use the above prepared impregnation solution to impregnate 15.58g macroporous SiO2 carrier, the average pore size of the macroporous SiO2 carrier is 25nm. Let it stand for 1 hour, put it in a closed oven, age it at 50℃ for 6 hours, then put it in a blast oven, dry it at 80℃ for 7 hours, and roast it at 500℃ in a muffle furnace for 3 hours to obtain the required catalyst (Al2O3@SiO2) / SiO2-6.

[0027] Comparative Example 1

[0028] Weigh 22.08g Al(NO3)·9H2O, dissolve it in 19ml deionized water, and use the prepared impregnation solution to impregnate 17.00g of macroporous SiO2 carrier, the average pore size of the macroporous SiO2 carrier used is 25nm. Let it stand for 1 hour, then put it in a blast oven, dry it at 80℃ for 7 hours, and calcine it in a muffle furnace at 550℃ for 3 hours to obtain the desired catalyst Al2O3 / SiO2.

[0029] Example 7

[0030] The catalyst prepared according to the above scheme was used in a fixed bed tubular reactor to evaluate the reaction activity of decanol dehydration to 1-decene. The reaction conditions were: catalyst loading of 1.0 g, reaction pressure of 0.3 MPa, reaction temperature of 300 ° C, liquid phase space velocity of decanol feed of 0.3 h -1 , the gas space velocity of nitrogen is 1200h -1 The final product is mainly 1-decene. After the reaction product is cooled and collected, it is analyzed by Alilent 8890 gas chromatograph equipped with HP-5 capillary column. The reaction evaluation results are listed in Table 1. Table 1 Reaction evaluation results of dehydration of n-decyl alcohol to 1-decene

[0031]

[0032] The results show that the catalyst (Al2O3@SiO2) / SiO2 of the present invention has excellent activity and selectivity for the target product 1-decene in the dehydration reaction of n-decyl alcohol.

[0033] Example 8

[0034] The (Al2O3@SiO2) / SiO2-5 catalyst in Example 5 was subjected to a long-term stability test. The conditions and process were the same as in Example 7. The reaction results are listed in Table 2.

[0035] Table 2 Performance of decanol dehydration reaction over (Al2O3@SiO2) / SiO2-5 catalyst

[0036]

[0037]

[0038] The catalyst provided by the present invention exhibits excellent activity, selectivity and long-term stability in the reaction of dehydrating n-decyl alcohol to prepare 1-decene, and has broad application prospects.

Claims

1. A catalyst for dehydrating n-decyl alcohol to prepare 1-decene, the catalyst composition is (Al2O3@SiO2) / SiO2, the dehydration active component nano-Al2O3 particles are assembled in the pores of the SiO2 carrier for confinement to form Al2O3@SiO2, the mass content of Al2O3 is 10.0%-15.0% based on the overall mass of the catalyst, the molar ratio of silicon in the SiO2 carrier for confinement to aluminum in the active component is 0.2-0.4, and the rest is SiO2 carrier; The preparation method of the catalyst comprises the following steps: (1) Prepare aluminum nitrate into an aqueous solution, adjust the pH value to 2-3, stir and add silica sol; in the solution, the molar ratio of silicon to aluminum is 0.1-0.5; (2) impregnating the SiO2 carrier in the impregnation solution prepared in step (1), leaving it to stand for 1-2 hours, and aging it in a closed oven at 50-70° C. for 5-10 hours; (3) drying the impregnated SiO2 carrier particles prepared in step (2), and then calcining them in a muffle furnace at 400-700° C. for 3-6 hours to obtain a catalyst (Al2O3@SiO2) / SiO2; The silica sol in step (1) is a small-particle acidic silica sol with a pH of 3-4, a silica particle size of 1-3 nm, and a silica solid content of 10%-20%; The SiO2 carrier in step (2) is a macroporous block or spherical SiO2 with an average pore size greater than or equal to 20 nm; In step (2), the impregnation liquid is used to impregnate the SiO2 carrier in equal volumes. After the impregnation, there is no flowing impregnation liquid on the surface of the SiO2 carrier.

2. The catalyst according to claim 1, characterized in that: In step (1), the pH value is adjusted to 2-3 with nitric acid having a mass concentration of 20%-40%; and the mass concentration of the aluminum nitrate aqueous solution is 30%-70%.

3. The catalyst according to claim 1, characterized in that: The SiO2 carrier in step (2) is a macroporous block or spherical SiO2 with an average pore size of 20-80nm.

4. The catalyst according to claim 1, characterized in that: The calcination temperature in the muffle furnace in step (3) is 400-600°C.

5. The catalyst according to claim 1, characterized in that: The drying temperature in step (3) is 80-100°C.

6. Use of the catalyst according to claim 1 in the dehydration of n-decyl alcohol to produce 1-decene.

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