Preparation and Application of an Oxide-Molecular Sieve Composite Material

Abstract

The present invention discloses a preparation method of a CuCoO x -SAPO-34 oxide-molecular sieve composite catalyst and its application in the reaction of ethanol ammoniation to synthesize acetonitrile. Specifically, the catalyst composition is CuCoO x composite oxide and SAPO-34 molecular sieve, which are prepared by coprecipitation method and hydrothermal method respectively. Then, SAPO-34 particles and CuCoOx oxide particles are mixed at a mass ratio of 0.25-1.5 and thoroughly mixed evenly by a ball mill. The catalyst of the present invention has the characteristics of high activity, high selectivity and high stability in a reaction system under conditions greater than atmospheric pressure. The catalyst of the present invention has easily available raw materials, a simple preparation process and excellent catalytic performance, and is suitable for large-scale production in factories.

Description

Technical Field

[0001] The present invention relates to a catalyst for preparing acetonitrile by ammoniation of ethanol, specifically CuCoO x -Preparation method of SAPO-34 oxide-molecular sieve composite catalyst and its application in the synthesis of acetonitrile from ethanol amination reaction. Background Art

[0002] Acetonitrile is an important chemical product widely used in the pharmaceutical, pesticide, organic synthesis, and petrochemical industries. Currently, acetonitrile is isolated as a byproduct of the ammoxidation of propylene to acrylonitrile. However, its production is severely limited by the availability of acrylonitrile plants. As demand increases, it can no longer meet current industrial needs. Developing a process for producing acetonitrile as the desired product is crucial to addressing the growing market demand for acetonitrile.

[0003] Compared with the technical routes of acetic acid ammonia dehydration and ethanol ammoxidation, the synthesis of acetonitrile by ethanol ammonia has the characteristics of high raw material utilization, hydrogen by-product, and milder reaction conditions, and therefore attracts more attention.

[0004] The key to the process of synthesizing acetonitrile from ethanol ammonia is the development of catalysts. In their research published in 2009, Zhang et al. [7] used a Ni-modified Co / γ-Al2O3 catalyst in the reaction process. Under the condition of 100% ethanol conversion, the selectivity of acetonitrile reached 92.5%. However, the reaction temperature was as high as 420°C, which was a relatively harsh condition. In 1981, Roger et al. reported that the reaction of ethanol ammonia to acetonitrile could be performed under the conditions of 15% Cu / Al2O3 catalyst and 325°C. Since then, copper-based catalysts have attracted widespread attention from scientists.

[0005] The reactant ethanol needs to pass through intermediate species such as acetaldehyde and imine to produce acetonitrile. Studies have shown that the conversion from ethanol to acetaldehyde is the limiting step of the entire process. It involves a hydrogen transfer reaction of the activated alcohol, so a dehydrogenation active center is required. However, according to experimental results, a carrier with a certain dehydrating effect is also needed to interact with the dehydrogenation active center to ensure the further reaction of the subsequent intermediate 1-aminoethanol, thereby obtaining the target product acetonitrile. However, in actual industrial production processes, as the reaction time accumulates, the system inevitably produces a certain pressure, which increases the NH3 partial pressure, covers the catalyst acid sites with NH3, hinders the dehydration reaction, and significantly reduces the product selectivity. Therefore, it is necessary to develop a catalyst with excellent acetonitrile selectivity and can withstand a certain pressure for the actual industrial production of ethanol ammonia to acetonitrile. Summary of the Invention

[0006] The present invention addresses the above problems and provides a preparation of a CuCoO x -SAPO-34 oxide-molecular sieve composite catalyst and its application in the reaction of ethanol ammoniation to synthesize acetonitrile.

[0007] To achieve the above object of the present invention, the following technical solutions are adopted:

[0008] The present invention provides a catalyst composed of CuCoO x composite oxide and SAPO-34 molecular sieve, which are prepared by the co-precipitation method and the hydrothermal method respectively. Then, the SAPO-34 particles and the CuCoOx oxide particles are mixed at a mass ratio of 0.25 - 1.5, and then fully mixed evenly using a ball mill, with a particle size distribution of 10 - 100 μm. The catalyst is applied to the reaction of ethanol ammoniation to synthesize acetonitrile. In CuCoO x x is a value determined by the oxygen of the metal oxide of Cu and the metal oxide of Co. The preparation method of the catalyst includes the following steps:

[0009] (1) Preparation of CuCoO x composite oxide: Weigh soluble copper salt and cobalt salt according to the required ratio, dissolve them in deionized water to form salt solution A; prepare an equal volume of alkali solution B and place it in a water bath at 20 - 50 °C. Under vigorous stirring, add solution A dropwise to solution B; after the addition is complete, adjust the pH value of the suspension to 9 - 11; then raise the water bath temperature to 55 - 80 °C and continue stirring and crystallizing for 3 - 8 h; filter, wash, dry, and then transfer to a muffle furnace and calcine at 400 - 650 °C for 4 - 6 h to obtain the CuCoO x composite oxide;

[0010] (2) Synthesis of SAPO-34 molecular sieve: Weigh a certain amount of aluminum source and deionized water according to the required ratio, stir to mix the two phases evenly. Weigh a certain amount of phosphorus source and add it dropwise to the above mixture. After the addition is complete, stir for 1 h. Gradually add a certain amount of silicon source dropwise to the above crystallization mixture. After the addition is complete, stir for 1 h. Gradually add a certain amount of template agent dropwise to the above well-mixed crystallization mixture. After the addition is complete, stir for 2 h until the mixture is homogeneous. Then transfer the well-stirred gel-like crystallization mixture into a stainless steel crystallization kettle with a polytetrafluoroethylene lining, age at 60 - 150 °C for 4 - 10 h, and then transfer to an oven at 180 - 220 °C for crystallization for 36 - 65 h. After the crystallization time is over, filter, wash the white paste, dry at 120 °C, and calcine the dried solid powder at 500 - 600 °C for 4 - 8 h. The obtained solid is the SAPO-34 molecular sieve.

[0011] (3) CuCoO xPreparation of SAPO-34 oxide-molecular sieve composite catalyst: SAPO-34 particles and CuCoOx oxide particles are mixed at a mass ratio of 0.25-1.5, ball milled at room temperature for 2-24 hours to ensure thorough mixing, and reduced in a hydrogen atmosphere to obtain the catalyst.

[0012] Furthermore, in the above technical solution, in the catalyst, CuCoO x The mass percentage of CuO in the composite oxide is 10-30%, and the mass percentage of CoO is 70-90wt%; CuCoO x The mass percentage of the composite oxide is 40-80 wt%, and the mass percentage of the SAPO-34 molecular sieve is 20-60 wt%.

[0013] Furthermore, in the above technical solution, in the preparation method, the copper salt described in step (1) is copper nitrate or copper chloride; the Co salt is cobalt nitrate or cobalt chloride; and the base is an aqueous solution of one of NaOH, urea, Na2CO3 or (NH4)2CO3, or a mixed aqueous solution of two or more thereof.

[0014] Furthermore, in the above technical solution, in the preparation method, the aluminum source described in step (2) is aluminum nitrate, sodium aluminate, aluminum isopropoxide, or aluminum chloride; the phosphorus source is ammonium hydrogen phosphate or phosphoric acid; the silicon source is silica sol, water glass, ethyl orthosilicate, or methyl orthosilicate; and the template is one or more templates selected from diethylamine (DEA), triethylamine (TEA), TEAOH, piperazine, morpholine, isopropylamine, or di-n-propylamine.

[0015] Furthermore, in the above technical solution, the molar ratio of the aluminum source, phosphorus source, silicon source and template in step (2) is SiO2:Al2O3:P2O5:template:H2O=(0.25-0.6):(0.8-1.0):(0.8-1):(1.9-2.2):(50-80).

[0016] Furthermore, in the above technical solution, the reduction process of the catalyst is carried out at 150-500° C. in a 10% H 2 / He mixed gas for 1-6 hours.

[0017] The catalyst provided by the present invention is applied to the reaction of synthesizing acetonitrile from ethanol ammonia under a working condition greater than atmospheric pressure, with a reaction temperature of 200-300° C. and a reaction pressure of 0.15-0.8 MPa, and has the characteristics of high activity and high selectivity.

[0018] Beneficial effects of the present invention:

[0019] The catalyst provided by the present invention has high acetonitrile selectivity and ethanol conversion rate in the reaction of synthesizing acetonitrile from ethanol ammonia under conditions greater than atmospheric pressure, and has excellent stability and good application value. DETAILED DESCRIPTION

[0020] Example 1

[0021] (1)CuCoO x Preparation of composite oxides: Weigh 3.05g of copper nitrate and 11.63g of cobalt nitrate respectively, dissolve them in 50mL of deionized water to prepare a mixed salt solution A. Dissolve 4.35g of sodium carbonate and 2.63g of sodium hydroxide in 50mL of deionized water to prepare a mixed alkaline solution B. Add A dropwise to B under stirring in a 35°C water bath. After the addition is completed, adjust the pH of the above suspension to 9.5 with 0.5M NaOH solution, transfer it to a 70°C constant temperature water bath, and continue stirring and crystallizing for 12h. Filter and wash the precipitate with deionized water, then dry it at 100°C, transfer it to a muffle furnace and roast it at 450°C for 4h to obtain CuCoO x complex oxides;

[0022] (2) Synthesis of SAPO-34 molecular sieve: According to the molar ratio of each substance in the synthesis mother liquor of 1Al2O3:0.3SiO2:0.8P2O5:60H2O:2TEAOH, a certain amount of pseudo-boehmite and deionized water were weighed and stirred for 20 minutes to mix the two phases evenly. A certain amount of phosphoric acid was weighed and added dropwise to the above mixture. After the addition was complete, the mixture was stirred for 1.5 hours. A certain amount of silica sol was added dropwise to the above crystallization mixture. After the addition was complete, the mixture was stirred for 3 hours. A certain amount of TEAOH was added dropwise to the above mixed crystallization mixture. After the addition was complete, the mixture was stirred for 3 hours until the mixture was uniform. The uniformly stirred gel-like crystallization mixture was then transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene lining, aged at 100°C for 8 hours, and then transferred to a 200°C oven for crystallization for 44 hours. After the crystallization time is completed, the white slurry is filtered, washed, and dried at 120° C. The dried solid powder is calcined at 550° C. for 6 h. The obtained solid is SAPO-34 molecular sieve.

[0023] (3)CuCoO x Preparation of SAPO-34 oxide-molecular sieve composite catalyst: 60g SAPO-34 particles were mixed with 40g CuCoOx oxide particles and ball milled at room temperature for 12 hours to fully mix them and obtain a particle size distribution of 10-100μm. x -SAPO-34 oxide-molecular sieve composite catalyst.

[0024] Comparative Example 1

[0025] The preparation method is the same as that in step (1) of Example 1 to obtain CuCoO x composite oxide.

[0026] Comparative Example 2

[0027] The preparation method is the same as that in step (2) of Example 1 to obtain SAPO-34 molecular sieve.

[0028] Comparative Example 3

[0029] Prepare CuCoO x composite oxide by the stepwise precipitation method: Weigh 3.05 g of copper nitrate and dissolve it in 15 mL of deionized water to prepare salt solution A; separately dissolve 4.35 g of sodium carbonate and 2.63 g of sodium hydroxide in 50 mL of deionized water to prepare mixed alkali solution B. Under stirring conditions in a 35 °C water bath, add A dropwise to B. After the addition is complete, stir for 2 h to obtain slurry C. Add 11.63 g of cobalt nitrate to 35 mL of deionized water to prepare salt solution D, add solution D dropwise to slurry C, adjust the pH of the above suspension to 9.5 with 0.5 M NaOH solution, and transfer it to a 70 °C constant temperature water bath, continue stirring and crystallizing for 12 h. Filter by suction, wash the precipitate with deionized water, then dry it at 100 °C and transfer it to a muffle furnace for calcination at 450 °C for 4 h to obtain CuCoO x composite oxide; The preparation method of SAPO-34 is the same as that in step (2) of Example 1 to obtain SAPO-34 molecular sieve.

[0030] CuCoO x The preparation method of the CuCoO

[0031] -SAPO-34 oxide-molecular sieve composite catalyst is the same as that in step (3) of Example 1.

[0032] (1) Preparation of CuNiO x composite oxide: Weigh 3.05 g of copper nitrate and 11.62 g of nickel nitrate respectively and dissolve them in 50 mL of deionized water to prepare mixed salt solution A. Separately dissolve 4.35 g of sodium carbonate and 2.63 g of sodium hydroxide in 50 mL of deionized water to prepare mixed alkali solution B. Under stirring conditions in a 35 °C water bath, add A dropwise to B. After the addition is complete, adjust the pH of the above suspension to 9.5 with 0.5 M NaOH solution, and transfer it to a 70 °C constant temperature water bath, continue stirring and crystallizing for 12 h. Filter by suction, wash the precipitate with deionized water, then dry it at 100 °C and transfer it to a muffle furnace for calcination at 450 °C for 4 h to obtain CuNiO x composite oxide;

[0033] The preparation method of SAPO-34 is the same as that in step (2) of Example 1 to obtain SAPO-34 molecular sieve.

[0034] CuNiO x The preparation method of the CuNiO-SAPO-34 oxide-zeolite composite catalyst is the same as that in step (3) of Example 1.

[0035] Example 2

[0036] CuCoO x The preparation method of the composite oxide is the same as that in step (1) of Example 1, and the only difference is that "3.05 g of copper nitrate and 11.63 g of cobalt nitrate" is changed to "2.19 g of copper chloride and 5.19 g of cobalt chloride".

[0037] The preparation method of SAPO-34 is the same as that in step (2) of Example 1 to obtain the SAPO-34 zeolite.

[0038] CuNiO x The preparation method of the CuNiO-SAPO-34 oxide-zeolite composite catalyst is the same as that in step (3) of Example 1.

[0039] Example 3

[0040] CuCoO x The preparation method of the composite oxide is the same as that in step (1) of Example 1, and the only difference is that "Another 4.35 g of sodium carbonate and 2.63 g of sodium hydroxide are dissolved in 50 mL of deionized water to prepare a mixed alkali solution B" is changed to "Another 10.26 g of ammonium carbonate is dissolved in 50 mL of deionized water to prepare an alkali solution B".

[0041] The preparation method of SAPO-34 is the same as that in step (2) of Example 1 to obtain the SAPO-34 zeolite.

[0042] CuNiO x The preparation method of the CuNiO-SAPO-34 oxide-zeolite composite catalyst is the same as that in step (3) of Example 1.

[0043] Example 4

[0044] Catalytic performance evaluation: The catalyst activity test was carried out in a fixed-bed reactor with a reaction pressure of 0.5 MPa. The experimental procedure is as follows: Weigh 1 g of the catalyst (20 - 40 mesh) and mix it evenly with 5 g of quartz sand (20 - 40 mesh), and then load it into a stainless-steel reaction tube with a diameter of 10 mm. At atmospheric pressure, 10% H2 / He gas (20 mL / min -1 ) was introduced into the reaction tube and the catalyst was in-situ reduced at 300 °C for 2 h, and then purged with nitrogen to cool down to 290 °C. Then the raw materials were fed into the reaction tube with a reaction space velocity of 1.0 h -1The ammonia-alcohol molar ratio was 7, the pressure was raised to 0.5 MPa, and after the reaction reached stability, the gas phase product composition was analyzed online on an Agilent 6890N chromatograph, and the liquid product was analyzed offline.

[0045] Table 1 Activity test results of catalysts obtained by different preparation methods, reaction conditions: T = 290 ° C, P = 0.5 MPa

[0046]

[0047] It can be seen from Table 1 that compared with CuCoO alone x Compared with oxides, SAPO-34 molecular sieve and industrial copper-based catalysts, CuCoO x The SAPO-34 oxide-molecular sieve composite catalyst achieved the highest ethanol conversion and acetonitrile selectivity, as well as the best stability. These experimental results demonstrate the significant advantages of the oxide-molecular sieve composite catalyst, improving catalytic performance.

[0048] The content of the present invention is not limited to the content of the embodiments of the present invention.

[0049] Specific examples are used herein to illustrate the embodiments of the present invention. The above examples are only intended to facilitate understanding of the present invention. It should be noted that those skilled in the art may make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A CuCoO x -SAPO-34 oxide-molecular sieve composite catalyst preparation method, characterized in that: The catalyst composition is CuCoO x The composite oxide and SAPO-34 molecular sieve are prepared by co-precipitation method and hydrothermal method respectively. Then, the SAPO-34 particles and CuCoO x oxide particles are mixed at a mass ratio of 0.25-1.5 and then fully mixed and homogenized using a ball mill. The particle size distribution is 10-100 μm; thus, the catalyst is prepared. The catalyst is applied to the reaction of ethanol amination to synthesize acetonitrile. In CuCoO x x is a value determined by the oxygen of the metal oxide of Cu and the metal oxide of Co.

2. The preparation method according to claim 1, characterized in that: (1)CuCoO x Preparation of composite oxide: Weigh soluble copper salt and cobalt salt according to the required ratio, dissolve them in deionized water to prepare salt solution A; prepare an equal-volume alkali solution B and place it in a water bath at 20 - 50 °C. While stirring vigorously, add solution A dropwise to solution B; after the addition is completed, adjust the pH value of the suspension to 9 - 11; Then raise the water bath temperature to 55 - 80 °C, continue stirring and crystallizing for 3 - 8 h; after filtration, washing, and drying, transfer it to a muffle furnace and calcine at 400 - 650 °C for 4 - 6 h to obtain CuCoO x composite oxide; (2) Synthesis of SAPO-34 molecular sieve: Weigh a certain amount of aluminum source and deionized water according to the required ratio, and stir to make the two phases evenly mixed; weigh a certain amount of phosphorus source and drop it into the above mixture drop by drop. After the dropping is completed, stir for 1 h; drop a certain amount of silicon source into the above mixture drop by drop. After the dropping is completed, stir for 1 h; drop a certain amount of template agent into the above evenly mixed mixture drop by drop. After the dropping is completed, stir for 2 h until the mixture is uniform; then transfer the evenly stirred gel-like mixture into a stainless steel crystallization kettle with a polytetrafluoroethylene lining, age at 60-150 °C for 4-10 h, and then transfer it to an oven at 180-220 °C for crystallization for 36-65 h; after the crystallization time ends, filter, wash, and dry the white paste at 120 °C. The dried solid powder is calcined at 500-600 °C for 4-8 h, and the obtained solid is the SAPO-34 molecular sieve; (3)CuCoO x - Preparation of CuCoOx-SAPO-34 oxide-zeolite composite catalyst: Mix SAPO-34 particles and CuCoOx oxide particles at a mass ratio of 0.25 - 1.5, and then ball-mill them at room temperature for 2 - 24 hours using a ball mill to make them fully and evenly mixed, thus obtaining the catalyst.

3. The preparation method according to claim 1 or 2, characterized in that: In the described catalyst, CuCoO x In the composite oxide, the mass percentage of CuO is 10-30%, and the mass percentage of CoO is 70-90 wt%; CuCoO x The mass percentage of the composite oxide is 40-80 wt%, and the mass content of the SAPO-34 molecular sieve is 20-60 wt%.

4. The preparation method according to claim 2, wherein: The copper salt described in step (1) is copper nitrate or copper chloride; the cobalt salt is cobalt nitrate or cobalt chloride; the base is an aqueous solution of one of NaOH, urea, Na2CO3 or (NH4)2CO3 or a mixed aqueous solution of two or more of them.

5. The preparation method according to claim 2, characterized in that: The aluminum source described in step (2) is aluminum nitrate, sodium aluminate, aluminum isopropoxide or aluminum chloride; the phosphorus source is ammonium hydrogen phosphate or phosphoric acid; the silicon source is silica sol, water glass, tetraethyl orthosilicate or methyl orthosilicate; the template agent is one of diethylamine, triethylamine, TEAOH, piperazine, morpholine, isopropylamine, di-n-propylamine or a combination of two or more template agents.

6. The preparation method according to claim 2, wherein: In step (2), the molar ratio of the amounts of the aluminum source, phosphorus source, silicon source, and template agent used is SiO2:Al2O3:P2O5:template agent:H2O = (0.25-0.6) : (0.8-1.0) : (0.8-1): (1.9-2.2) : (50-80).

7. Use of the catalyst obtained by the preparation method according to claim 1, characterized in that: The composite catalyst is reduced. The reduction process is carried out in a 10% H2 / He mixed gas at 150-300 °C for 1-6 h. After reduction, the catalyst is applied to the reaction of ethanol ammoniation to synthesize acetonitrile under conditions above atmospheric pressure.

8. The application according to claim 7, characterized in that: The reaction temperature is 200-500 °C, and the reaction pressure is 0.15-0.8 MPa.

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