A preparation method and application of a catalyst for synthesizing cyclohexanone oxime by cyclohexanone ammoxidation

Abstract

The application discloses a preparation method and application of a catalyst for synthesizing cyclohexanone oxime through cyclohexanone ammoxidation, and belongs to the technical field of molecular sieve synthesis and catalysis. A silicon source, a tetrapropylammonium hydroxide aqueous solution and deionized water are uniformly mixed to obtain silicon ester hydrolysate A; a titanium source is added into a low-carbon alcohol to obtain titanium ester hydrolysate B, and then a crystallization aid is added; the obtained silicon ester hydrolysate A and the titanium ester hydrolysate B are uniformly mixed, alcohol is removed by heating, and then crystallization is carried out at 150-180 DEG C under self-generating pressure for 24-96 hours to obtain a titanium-silicon molecular sieve mother liquor; an iron salt aqueous solution and an aluminum sol or a silicon sol or a silicon-aluminum sol are added into the titanium-silicon molecular sieve mother liquor, and aging is carried out at 60-80 DEG C under stirring for 10-72 hours; spray molding is carried out; and then the obtained titanium-silicon molecular sieve is dried and calcined at 500-650 DEG C for 8-24 hours to obtain TS-1 molecular sieve. The prepared TS-1 molecular sieve can prepare cyclohexanone oxime under relatively mild reaction conditions, and effectively improves the conversion rate of raw materials and the selectivity of products.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieve synthesis and catalysis, and relates to a preparation method and application of a catalyst for synthesizing cyclohexanone oxime through ammoxidation of cyclohexanone. Background Art

[0002] Cyclohexanone oxime is a critical intermediate in the chemical industry, playing an indispensable role in the production of caprolactam. Traditional preparation methods suffer from harsh reaction conditions, low selectivity, and environmental pollution. Since the 1980s, a cyclohexanone ammoxidation process has been developed. Cyclohexanone oxime is produced by ammoxidation using cyclohexanone, ammonia, and hydrogen peroxide as raw materials and titanium silicalite TS-1 as a catalyst. Compared with traditional processes, the cyclohexanone ammoxidation process offers significant advantages, such as lower reaction temperatures and reduced energy consumption.

[0003] TS-1 catalyst, a specialized titanium silicalite molecular sieve, has a relatively high production cost. Although the ammoxidation of cyclohexanone to cyclohexanone oxime is environmentally friendly, the high production cost and relatively low reactivity and cyclohexanone oxime selectivity of existing catalysts limit its large-scale production application. The remarkable activity of TS-1 in the ammoxidation of cyclohexanone to cyclohexanone oxime is attributed to the presence of a unique tetracoordinated Ti center. Therefore, fully considering the preparation of skeletal titanium during the synthesis process is a top priority. The development of catalysts with high catalytic activity and cyclohexanone oxime selectivity is an important and pressing research topic. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a preparation method and application of a catalyst for the ammoxidation of cyclohexanone to synthesize cyclohexanone oxime. In the process of preparing TS-1, the present invention strictly controls the hydrolysis conditions of the titanium source and the silicon source in the synthesis mother liquor. At the same time, by adding a crystallization aid, the soluble titanium species formed by hydrolysis is promoted to undergo a condensation reaction with the silicon species to form Si-O-Ti. The metallic iron activity is introduced during the titanium silicon molecular sieve catalyst forming process to further improve the catalyst ammoxidation activity and cyclohexanone oxime selectivity. The catalyst prepared by the present invention has good sphericity, uniform particle size distribution, low wear rate, is suitable for producing cyclohexanone oxime using a slurry bed reactor, and has important industrial application value.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a catalyst for synthesizing cyclohexanone oxime by ammoxidation of cyclohexanone, comprising the following steps:

[0007] (1) mixing a silicon source, a tetrapropylammonium hydroxide aqueous solution, and deionized water, and hydrolyzing the mixture to obtain a silicon ester hydrolyzate A;

[0008] (2) adding a titanium source to a low-carbon alcohol, hydrolyzing to obtain a titanium ester hydrolyzate B, and then adding a crystallization aid;

[0009] (3) uniformly mixing the silicon ester hydrolyzate A obtained in step (1) and the titanium ester hydrolyzate B obtained in step (2), heating to remove alcohol, and crystallizing the obtained titanium silicalite sol at 150-180° C. under autogenous pressure for 24-96 hours to obtain a titanium silicalite mother liquor;

[0010] (4) adding an aqueous solution of iron salt and aluminum sol or silica sol or silica-alumina sol to the titanium silicate mother liquor obtained in step (3), aging at 60-80° C. for 10-72 hours under stirring conditions, spray-forming, drying the spray-formed titanium silicate, and calcining at 500-650° C. for 8-24 hours to obtain TS-1 molecular sieve.

[0011] Based on the above technical solution, further, the silicon source described in step (1) is one or a mixture of two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate; and the concentration of the tetrapropylammonium hydroxide aqueous solution is 10 to 50 wt%.

[0012] Based on the above technical solution, further, the mass ratio of the silicon source, tetrapropylammonium hydroxide and water in step (1) is (2-10):1:(3-15).

[0013] Based on the above technical solution, further, the titanium source in step (2) is one or a mixture of two or more of tetraethyl titanate, tetrabutyl titanate, tetraisopropyl titanate, titanium trichloride, and titanium tetrachloride; and the low-carbon alcohol is one of isopropyl alcohol, tert-butanol, n-butanol, and n-pentanol.

[0014] Based on the above technical solution, further, the mass ratio of the titanium source to the low-carbon alcohol in step (2) is 1:5-10.

[0015] Based on the above technical solution, further, the crystallization aid described in step (2) is one or a mixture of two or more of EDTA, ethylenediamine, glycine, and lactic acid, and the molar ratio of the added amount to the titanium source is (0.05-0.2):1.

[0016] Based on the above technical solution, further, the heating alcohol removal in step (3) is to remove alcohol at 80-90° C. for 4 to 10 hours.

[0017] Based on the above technical solution, further, the concentration of the aluminum sol or silica sol or silica-alumina sol described in step (4) is 10-50wt%, the concentration of iron ions in the iron salt aqueous solution is 5-20wt%, the mass ratio of aluminum sol or silica sol or silica-alumina sol to the titanium silicate mother liquor is (0.1-0.8):1, and the mass ratio of the iron salt aqueous solution to the molecular sieve mother liquor is (0.01-0.1):1.

[0018] Another aspect of the present invention provides a catalyst prepared by the above preparation method.

[0019] The present invention also provides the use of the catalyst in catalyzing the ammoxidation of cyclohexanone to synthesize cyclohexanone oxime.

[0020] Based on the above technical solution, the catalytic ammoxidation of cyclohexanone to synthesize cyclohexanone oxime is further specifically as follows: cyclohexanone, hydrogen peroxide, ammonia water and solvent are added to a reactor, a catalyst with a mass concentration of 0.5-5% is added, the reaction temperature is 35-80°C, and the pressure is 0-0.8MPa. After the reaction is completed, cyclohexanone oxime is separated.

[0021] Based on the above technical solution, further, the mass concentration of ammonia water is 20-30wt%, the concentration of hydrogen peroxide is 30-60wt%; the molar ratio of ammonia to cyclohexanone is (1.60-3.10):1, the molar ratio of hydrogen peroxide to cyclohexanone is (1.05-1.2):1, the solvent is tert-butanol, the mass ratio of the solvent to cyclohexanone is (5-30):1, the stirring speed is 150-600 r / min, and the reaction time is 1-6 hours.

[0022] Compared with the reported method for preparing cyclohexanone oxime using molecular sieve catalysis, the present invention has the following beneficial effects:

[0023] The present invention is directed to the ammoxidation reaction of cyclohexanone, in which the tetracoordinate titanium in the titanium silicate framework is the active center of ammoxidation. During the synthesis process, skeleton titanium can only be formed when the hydrolysis rates of the silicon precursor and the titanium precursor are consistent. Otherwise, non-skeleton titanium or TiO2 will be produced. Therefore, in the process of preparing TS-1, the present invention strictly controls the hydrolysis conditions of the titanium source and the silicon source in the synthesis mother liquor, and simultaneously adds a crystallization aid to promote the soluble titanium species formed by hydrolysis to undergo a condensation reaction with the silicon species to form Si-O-Ti. At the same time, the present invention also introduces metallic iron activity during the titanium silicate catalyst molding process to further improve the catalyst ammoxidation activity and cyclohexanone oxime selectivity. The catalyst prepared by the present invention has good sphericity, uniform particle size distribution, low wear rate, is suitable for producing cyclohexanone oxime using a slurry bed reactor, and has important industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a scanning electron microscope image of the titanium silicon molecular sieve raw powder synthesized in Comparative Example 1.

[0025] Figure 2 This is a scanning electron microscope image of the titanium silicon molecular sieve raw powder synthesized in Example 1.

[0026] Figure 3 This is a scanning electron microscope image of the titanium silicon molecular sieve catalyst synthesized in Example 1. DETAILED DESCRIPTION

[0027] The present invention is specifically described below with reference to examples:

[0028] The calculation formulas for the conversion of cyclohexanone and the selectivity of cyclohexanone oxime are as follows:

[0029] Cyclohexanone conversion (%) = (C0-C1) / C0×100%;

[0030] Cyclohexanone oxime selectivity (%) = C2 / (C0-C1) × 100%;

[0031] C0, C1 and C2 are the concentrations of cyclohexanone before the reaction, cyclohexanone after the reaction and cyclohexanone oxime respectively.

[0032] Comparative Example 1

[0033] This comparative example provides a method for preparing a conventional titanium silicate molecular sieve, comprising the following steps:

[0034] Take 20g of deionized water and add it to 22.5g of silica sol (30% wt). After stirring for 15 minutes, add 2.08g of tetrapropylammonium bromide to the colloid and continue stirring for 30 minutes to obtain a raw silicon solution; tetrabutyl titanate and acetylacetone are mixed in a mass ratio of 1:1 and stirred for 10 minutes to obtain a raw titanium solution; take 1.54ml of the prepared titanium solution and add it dropwise to the raw silicon solution for 6 hours, then stir for 30 minutes to obtain a silicon-titanium solution, add 5.2ml of n-butylamine and supplement 14.5g of deionized water, continue stirring for 60 minutes to obtain a uniform titanium-silicon solution; then add the obtained solution to a 200ml stainless steel reactor and crystallize it under autogenous pressure and 170°C to obtain a titanium-silicon molecular sieve.

[0035] Example 1:

[0036] This embodiment provides a method for preparing TS-1 molecular sieve-1, comprising the following steps:

[0037] (1) 90 g of a 25 wt% aqueous solution of tetrapropylammonium hydroxide and 75 ml of deionized water were added to 100 g of ethyl orthosilicate to hydrolyze the ethyl orthosilicate to obtain a silicone ester hydrolyzate A;

[0038] (2) 4.5 g of tetrabutyl titanate was added to 36 ml of isopropyl alcohol, and hydrolysis was carried out at room temperature to obtain a titanium ester hydrolysate B, and then 1.8 g of EDTA was added;

[0039] (3) The above-mentioned silicon ester hydrolysate A and the titanium ester hydrolysate B were mixed, and alcohol removal was continued at 85°C for 6 hours. 240 g of the obtained clear titanium-silicon sol was placed in a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and crystallization was carried out at 170°C under autogenous pressure for 24 hours to obtain a titanium-silicon molecular sieve mother liquor;

[0040] (4) 200 g of the above-mentioned titanium-silicon molecular sieve mother liquor was taken, 30 g of an aluminum sol with a mass concentration of 30% and 10 g of an aqueous solution of ferric nitrate with a mass fraction of 10% were added, and aging was carried out at 70°C for 24 hours under stirring. Spray molding was carried out using a small spray molding machine, and the spray-molded catalyst was dried at 100°C for 12 hours and calcined at 540°C for 12 hours to obtain a spray-molded TS-1 molecular sieve-1.

[0041] Figure 1 A scanning electron microscope image of the titanium-silicon molecular sieve raw powder synthesized for Comparative Example 1, Figure 2 A scanning electron microscope image of the titanium-silicon molecular sieve raw powder synthesized for Example 1, Figure 3 A scanning electron microscope image of the titanium-silicon molecular sieve catalyst synthesized for Example 1. It can be found from the scanning electron microscope images of the catalysts prepared in Comparative Example 1 and Example 1 that the titanium-silicon molecular sieve prepared by the method of Comparative Example 1 has a crystal size of about 8 μm, while the titanium-silicon molecular sieve prepared by the synthesis method used in Example 1 is of nanoscale, has a crystal size of about 200 nm, and is very uniform. The titanium-silicon molecular sieve catalyst obtained has good sphericity and uniform particle size distribution.

[0042] Example 2:

[0043] The present example provides a preparation method of a TS-1 molecular sieve-2, which comprises the following steps:

[0044] (1) 120 g of tetraethyl orthosilicate was added to 100 g of a 25 wt% aqueous solution of tetrapropylammonium hydroxide and 100 ml of deionized water, and hydrolysis of the tetraethyl orthosilicate was carried out to obtain a silicon ester hydrolysate A;

[0045] (2) 5 g of tetrabutyl titanate was added to 40 ml of isopropyl alcohol, and hydrolysis was carried out at room temperature to obtain a titanium ester hydrolysate B, and then 3.5 g of ethylenediamine was added;

[0046] (3) The above-mentioned silicon ester hydrolysate A and the titanium ester hydrolysate B were mixed, and alcohol removal was continued at 85°C for 6 hours. 220 g of the obtained clear titanium-silicon sol was placed in a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and crystallization was carried out at 170°C under autogenous pressure for 72 hours to obtain a titanium-silicon molecular sieve mother liquor;

[0047] (4) Take 200 g of the above-mentioned titanium silicate mother liquor, add 30 g of 30% aluminum sol and 10 g of 10% ferric nitrate aqueous solution, age at 70 ° C under stirring conditions for 24 hours, use a small spray molding machine to spray mold, dry the spray molded catalyst at 100 ° C for 12 hours, and calcine at 540 ° C for 12 hours to obtain spray-molded TS-1 molecular sieve-2.

[0048] Example 3:

[0049] This embodiment provides a method for preparing TS-1 molecular sieve-3, comprising the following steps:

[0050] (1) 60 g of a 25 wt% aqueous solution of tetrapropylammonium hydroxide and 60 ml of deionized water were added to 75 g of ethyl orthosilicate to hydrolyze the ethyl orthosilicate to obtain a silicone ester hydrolyzate A;

[0051] (2) 3.2 g of tetrabutyl titanate was added to 17 ml of isopropanol and hydrolyzed at room temperature to obtain titanium ester hydrolyzate B, and then 4.2 g of glycine was added;

[0052] (3) The silicon ester hydrolyzate A and the titanium ester hydrolyzate B were mixed and reacted at 85° C. for 6 hours to remove alcohol. 210 g of the obtained clarified titanium silicate sol was placed in a stainless steel sealed reactor with a polytetrafluoroethylene liner and crystallized at 170° C. under autogenous pressure for 72 hours to obtain a titanium silicate molecular sieve mother liquor.

[0053] (4) Take 200 g of the above-mentioned titanium silicalite mother liquor, add 30 g of 30% silica sol and 10 g of 10% ferric nitrate aqueous solution, age at 70 ° C for 24 hours under stirring conditions, use a small spray molding machine to spray mold, dry the spray molded catalyst at 100 ° C for 12 hours, and calcine at 540 ° C for 12 hours to obtain spray-molded TS-1 molecular sieve-3.

[0054] Example 4:

[0055] This embodiment provides a method for preparing TS-1 molecular sieve-4, comprising the following steps:

[0056] (1) 150 g of a 25 wt% aqueous solution of tetrapropylammonium hydroxide and 150 ml of deionized water were added to 200 g of ethyl orthosilicate to hydrolyze the ethyl orthosilicate to obtain a silicone ester hydrolyzate A;

[0057] (2) 8 g of tetrabutyl titanate was added to 60 ml of isopropyl alcohol and hydrolyzed at room temperature to obtain titanium ester hydrolyzate B, and then 13 g of lactic acid was added;

[0058] (3) The silicon ester hydrolyzate A and the titanium ester hydrolyzate B were mixed and reacted at 85° C. for 6 hours to remove alcohol. 500 g of the obtained clarified titanium silicalite was placed in a stainless steel sealed reactor with a polytetrafluoroethylene liner and crystallized at 170° C. under autogenous pressure for 72 hours to obtain a titanium silicalite mother liquor.

[0059] (4) Take 200 g of the above-mentioned titanium silicate mother liquor, add 30 g of 30% aluminum sol and 10 g of 10% ferric nitrate aqueous solution, age at 70 ° C for 24 hours under stirring conditions, use a small spray molding machine to spray mold, dry the spray molded catalyst at 100 ° C for 12 hours, and calcine at 540 ° C for 12 hours to obtain spray-molded TS-1 molecular sieve-4.

[0060] Example 5:

[0061] This embodiment provides a method for preparing TS-1 molecular sieve-5, comprising the following steps:

[0062] (1) 90 g of a 25 wt% aqueous solution of tetrapropylammonium hydroxide and 90 ml of deionized water were added to 100 g of ethyl orthosilicate to hydrolyze the ethyl orthosilicate to obtain a silicone ester hydrolyzate A;

[0063] (2) 5 g of tetrabutyl titanate was added to 40 ml of isopropanol and hydrolyzed at room temperature to obtain titanium ester hydrolyzate B, and then 4.3 g of lactic acid was added;

[0064] (3) The silicon ester hydrolyzate A and the titanium ester hydrolyzate B were mixed and reacted at 85° C. for 6 hours to remove alcohol. 250 g of the obtained clarified titanium silicalite was placed in a stainless steel sealed reactor with a polytetrafluoroethylene liner and crystallized at 175° C. under autogenous pressure for 72 hours to obtain a titanium silicalite mother liquor.

[0065] (4) Take 200 g of the above-mentioned titanium silicate mother liquor, add 30 g of 30% aluminum sol and 10 g of 20% ferric nitrate aqueous solution, age at 80 ° C for 24 hours under stirring conditions, use a small spray molding machine to spray mold, dry the spray molded catalyst at 100 ° C for 12 hours, and calcine at 600 ° C for 12 hours to obtain spray-molded TS-1 molecular sieve-5.

[0066] Example 6:

[0067] The catalyst prepared in Comparative Example 1 or Examples 1-5 catalyzes the ammoxidation of cyclohexanone to synthesize cyclohexanone oxime. The specific process is as follows: 3 g of the catalyst prepared in Comparative Example 1 or Examples 1-5 is weighed and placed in a three-necked flask, and 4.7 g of cyclohexanone, 13.5 g of 25% ammonia water, 3.9 g of 50% hydrogen peroxide, and 66.3 g of tert-butanol are added in sequence at 0.5 MPa. The reaction temperature is 80° C., the rotation speed is 400 r / min, and the reaction is stirred thoroughly for 1 hour. The conversion rate of cyclohexanone and the selectivity of cyclohexanone oxime are analyzed by gas chromatography. The results are shown in Table 1.

[0068] Table 1 Conditions and results of cyclohexanone oxime synthesis from cyclohexanone catalyzed by the catalysts of Comparative Example 1 or Examples 1-5

[0069]

[0070] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the specific details of the above embodiments. Within the technical concept of the present invention, the technical solutions of the present invention can be subjected to a variety of simple variations and combinations, all of which fall within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for synthesizing cyclohexanone oxime by ammoxidation of cyclohexanone, characterized in that: The steps include: (1) mixing a silicon source, a tetrapropylammonium hydroxide aqueous solution and deionized water uniformly, and hydrolyzing the mixture to obtain a silicon ester hydrolyzate A; (2) adding a titanium source to a low-carbon alcohol, hydrolyzing to obtain a titanium ester hydrolyzate B, and then adding a crystallization aid; (3) uniformly mixing the silicon ester hydrolyzate A obtained in step (1) and the titanium ester hydrolyzate B with the crystallization aid added obtained in step (2), heating to remove alcohol, and crystallizing the obtained titanium silicalite sol at 150-180° C. under autogenous pressure for 24-96 hours to obtain a titanium silicalite mother liquor; (4) adding an aqueous solution of iron salt and aluminum sol or silica sol or silica-alumina sol to the titanium silicate mother solution obtained in step (3), aging at 60-80°C for 10-72 hours under stirring conditions, spray-forming, drying the spray-formed titanium silicate, and calcining at 500-650°C for 8-24 hours to obtain TS-1 molecular sieve; The crystallization aid described in step (2) is one or a mixture of two or more of EDTA, ethylenediamine, glycine, and lactic acid.

2. The preparation method according to claim 1, characterized in that The silicon source described in step (1) is one or a mixture of two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate; the concentration of the tetrapropylammonium hydroxide aqueous solution is 10-50wt%; and the mass ratio of the silicon source, tetrapropylammonium hydroxide and water is (2-10):1:(3-15).

3. The preparation method according to claim 1, characterized in that The titanium source in step (2) is one of tetraethyl titanate, tetrabutyl titanate, and tetraisopropyl titanate, or a mixture of two or more thereof; the low-carbon alcohol is one of isopropyl alcohol, tert-butanol, n-butanol, and n-pentanol; and the mass ratio of the titanium source to the low-carbon alcohol is 1:5-10.

4. The preparation method according to claim 1, characterized in that The molar ratio of the amount of the crystallization aid added in step (2) to the titanium source is (0.05-0.2):

1.

5. The preparation method according to claim 1, characterized in that The heating and alcohol removal in step (3) is carried out at 80-90° C. for 4-10 hours.

6. The preparation method according to claim 1, characterized in that The concentration of the aluminum sol or silica sol or silica-alumina sol described in step (4) is 10-50 wt%, the concentration of iron ions in the iron salt aqueous solution is 5-20 wt%, the mass ratio of the aluminum sol or silica sol or silica-alumina sol to the titanium silicate mother liquor is (0.1-0.8):1, and the mass ratio of the iron salt aqueous solution to the molecular sieve mother liquor is (0.01-0.1):

1.

7. The catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the catalyst according to claim 7 in catalyzing the ammoxidation of cyclohexanone to synthesize cyclohexanone oxime.

9. The use according to claim 8, characterized in that The catalytic ammoxidation of cyclohexanone to synthesize cyclohexanone oxime reaction is specifically as follows: cyclohexanone, hydrogen peroxide, ammonia water and a solvent are added to a reactor, a catalyst with a mass concentration of 0.5-5% is added, the reaction temperature is 35-80°C, and the pressure is 0-0.8 MPa. After the reaction is completed, cyclohexanone oxime is separated.

10. The use according to claim 9, characterized in that The mass concentration of aqueous ammonia is 20-30 wt %, the concentration of hydrogen peroxide is 30-60 wt %; the molar ratio of ammonia to cyclohexanone is (1.60-3.10):1, the molar ratio of hydrogen peroxide to cyclohexanone is (1.05-1.2):1, the solvent is tert-butyl alcohol, the mass ratio of the solvent to cyclohexanone is (5-30):1, the stirring speed is 150-600 r / min, and the reaction time is 1-6 hours.

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