Novel efficient molecular sieve catalyst for preparing acetonitrile through ethane ammoxidation

Abstract

The invention belongs to a novel catalyst technology in the field of chemical engineering, and relates to a high-efficiency catalyst for preparing acetonitrile through ethane ammoxidation. According to the catalyst, an MFI type molecular sieve is used as a carrier, dealumination and tin loading treatment are carried out, tin (Sn) is used as an active component, and the content of the active component is 0.1 wt%-5wt%. The method comprises the following steps: mixing an organic tin or inorganic tin source with an MFI type molecular sieve in a water-free and oxygen-free environment, and plating tin by adopting a solvent-free ion exchange method, thereby obtaining the catalyst. According to the method, no CO2 is generated in the process of preparing acetonitrile through ethane ammoxidation, and meanwhile, higher ethane conversion rate and acetonitrile yield are shown.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical catalysis, and particularly relates to a high-efficiency catalyst for the ammoxidation of ethane to acetonitrile and a preparation method thereof. Background Art

[0002] As a resource widely distributed in associated oilfield gas, shale gas, natural gas and refinery gas, ethane has the dual attributes of fuel and chemical raw material. In recent years, with the in-depth promotion of the shale gas revolution in the United States, the supply of ethane has increased significantly, resulting in a substantial reduction in its cost, which has in turn stimulated a research boom on using it as a direct raw material for acetonitrile production.

[0003] As an important organic chemical raw material and solvent, acetonitrile has a wide range of applications in the fields of medicine, pesticides, analytical chemistry and lithium batteries. With the rapid development of related industries, the market demand for acetonitrile continues to grow, driving the continuous progress of its production and application technologies. Due to its rich source, low price and excellent solvent properties, acetonitrile has become one of the commonly used solvents in organic synthesis. In addition, acetonitrile is also a key synthetic intermediate and is often used as a nitrogen source for the preparation of various nitrogen-containing compounds. For example, compounds containing nitrile groups have important applications in medicine and materials science. Research shows that acetonitrile can be used as a reliable source of cyanide for the synthesis of various functional compounds. On the other hand, heterocyclic structures are widely present in natural products and synthetic compounds and have important values in the fields of organic synthesis, agriculture, animal husbandry, etc. Some heterocyclic compounds have also been widely used in the medical field due to their unique biological activities. Acetonitrile plays a key role in the construction of various heterocyclic compounds, such as the synthesis of heterocycles like pyridine, oxazole and tetrazole. Therefore, acetonitrile is not only an important solvent and intermediate, but also shows great potential in the synthesis of heterocyclic compounds, further highlighting its important position in the chemical industry.

[0004] The conversion of ethane to acetonitrile not only has significant economic and environmental benefits, but also provides a solid foundation for the wide application of acetonitrile. With the continuous progress of technology, the position of acetonitrile in the chemical industry will be further consolidated, and its market prospect will be broader.

[0005] Ethane ammoxidation is an important process for the preparation of acetonitrile. The commonly used catalysts in the prior art have problems such as low activity, poor selectivity and many by-products. For example: in the research work on the ammoxidation of ethane to acetonitrile, the early patent SU738657 disclosed a catalyst using oxides of Cr-Nb-Mo as the catalyst. At a reaction temperature of 350 - 500 °C and a reaction material residence time of 19 s, the maximum acetonitrile yield was only 10%, and the by-products were CO, CO2 and HCN. For example, Essid, S.; Ayari, F.; Bulánek, R.; etc. (2019,93 , 13–23) The Co / BEA catalyst prepared by solid-state ion exchange method showed excellent catalytic performance in ethane ammoxidation, with the ethane conversion rate reaching up to 23% at 500°C, the selectivity of acetonitrile reaching up to 70%, the yield of acetonitrile being 16%, and the selectivity of byproduct CO2 being 10-40%. The catalysts reported in the above-mentioned public literature provide important ideas for the conversion of light olefins into acetonitrile and open up a new synthesis method. However, improving the conversion rate of ethane and the selectivity of acetonitrile are still key issues to be solved in this field. Summary of the invention

[0006] The present invention aims to provide a novel method for preparing a molecular sieve catalyst for use in the reaction of ethane ammoxidation to prepare acetonitrile, aiming to improve the yield of acetonitrile.

[0007] In order to achieve the above-mentioned object, the present invention provides an ethane ammonia oxidation catalyst, wherein the ethane ammonia oxidation catalyst uses an MFI type molecular sieve as a carrier, uses Sn as an active metal, and changes its acidic site distribution by regulating the Si / Al of the molecular sieve through dealumination, and then modifies the molecular sieve with an active metal to improve the catalytic performance of the catalyst.

[0008] The catalyst according to the present invention adopts an MFI type molecular sieve with zeolite Si / Al=40-150.

[0009] According to the catalyst of the present invention, the specific surface area of ​​the catalyst is 200-500m 2 / g.

[0010] According to the catalyst of the present invention, the average pore diameter of the catalyst is 1-10 nm.

[0011] According to the catalyst of the present invention, the active component Sn of the molecular sieve catalyst accounts for 0.1wt%-5wt% of the total mass.

[0012] According to the catalyst described in the present invention, the specific preparation steps of the Sn / MFI type are as follows: the MFI type molecular sieve is dealuminated by stirring and heating it under reflux with a 2-10 mol / L acidic solution, then drying it, and then transferring it to an anhydrous and oxygen-free environment, mixing and grinding the molecular sieve with the Sn active component, and then calcining it in an inert gas environment, and finally washing, centrifuging, filtering, drying, and granulating the molecular sieve to obtain a Sn / MFI type molecular sieve catalyst.

[0013] According to the method described in this article, the MFI molecular sieve dealumination stirring heating reflux time is 5-30h, the dehydration vacuum drying time is 2-6h, and the vacuum drying temperature is increased to 50-200°C at a rate of 5-10°C / min.

[0014] According to the method described herein, the dehydrated MFI zeolite is loaded with an active component in an anhydrous and oxygen-free environment, and the active component is sourced from organic Sn / inorganic Sn.

[0015] According to the method described herein, the MFI zeolite is ground with 0.1 wt% - 5 wt% of the active component based on the total weight of the zeolite, and the grinding time is 10 - 30 min.

[0016] According to the method described herein, the ground powder is calcined in an inert environment to obtain the Sn / MFI zeolite catalyst; the calcination is also in an anhydrous and oxygen-free environment, and the temperature is raised to 400 - 600 °C at a rate of 5 - 15 °C / min and maintained for 6 - 30 h.

[0017] According to the method described herein, the catalyst after tube furnace calcination is poured into a beaker and stirred with alcohol for washing, and the washing time is 2 - 6 h.

[0018] According to the method described herein, the separation process after alcohol washing uses centrifugal filtration, and the centrifugal speed is 1500 - 3000 rpm / min.

[0019] According to the method described herein, the obtained Sn / MFI zeolite catalyst is dried in an oven for 8 - 15 h, and the oven temperature is 50 - 80 °C.

[0020] According to the method described herein, the obtained Sn / MFI zeolite catalyst is granulated at 20 - 80 mesh to obtain the final Sn / MFI catalyst.

[0021] According to the method of the present invention, the further preferably reaction conditions for ethane ammoxidation are as follows: the activation temperature of the catalyst is 400 - 650 °C, the activation time is 1 - 3 h, the activation gas is nitrogen, and the target value of the catalyst bed temperature is 400 - 650 °C. Among them, the gas flow rate of ethane is 5 - 50 ml / min, the gas flow rate of ammonia is denoted as 5 - 50 ml / min, the gas flow rate of oxygen is denoted as 1 - 50 ml / min, and the gas flow rate of inert gas is denoted as 30 - 100 ml / min.

[0022] The beneficial effects of the present invention: The preparation method of the zeolite catalyst of the present invention is simple. By performing dealumination and dehydration operations on the MFI zeolite, the performance of the zeolite catalyst prepared by the solid-state ion exchange method is stable. No CO2 is produced in the reaction of ethane ammoxidation to acetonitrile, and it has a high ethane conversion rate and acetonitrile selectivity. Among them, the highest acetonitrile yield reaches 30%. Specific Embodiments

[0023] The following further illustrates the present invention in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0024] Example 1 Using an MFI zeolite molecular sieve after dealumination and dehydration with an average pore diameter of 3.2 nm, a specific surface area of 330 m 2 / g, and Si / Al = 45 as the carrier, 1 wt% of the organic Sn / inorganic Sn component was mixed with the molecular sieve in an anhydrous and oxygen-free environment and ground for 10 min. Then, it was transferred to a furnace under the protection of an inert atmosphere, calcined at 500 °C for 10 h by passing helium gas, taken out, washed with an aqueous solvent for 2 h, centrifuged, filtered, dried, and granulated to obtain Catalyst 1#.

[0025] The performance of the above catalyst in the ethane ammoxidation reaction was measured on a fixed-bed reactor. The specific reaction conditions were as follows: the catalyst dosage was 100 - 300 mg, the catalyst was activated at 600 °C in nitrogen for 1 hour before the reaction, and then the reaction gas was introduced at 500 °C. The reaction pressure was 0.1 MPa, the gas flow rate of the reaction gas was 55 ml / min for nitrogen, 38.6 ml / min for ethane, 24.5 ml / min for ammonia, and 23.8 ml / min for oxygen. The ethane conversion rate of Catalyst 1# was 67.5%, the selectivity for acetonitrile was 44.2%, and the yield of acetonitrile was 29.9%.

[0026] Example 2 Using an MFI zeolite molecular sieve after dealumination and dehydration with an average pore diameter of 2.8 nm, a specific surface area of 320 m 2 / g, and Si / Al = 40 as the carrier, 2 wt% of the organic / inorganic Sn component was mixed with the molecular sieve in an anhydrous and oxygen-free environment and ground for 10 min. Then, it was transferred to a furnace under the protection of an inert atmosphere, calcined at 550 °C for 20 h by passing helium gas, taken out, washed with an aqueous solvent for 2 h, centrifuged, filtered, dried, and granulated to obtain Catalyst 2#.

[0027] The performance of the above catalyst in the ethane ammoxidation reaction was measured on a fixed-bed reactor. The specific reaction conditions were as follows: the catalyst dosage was 100 - 300 mg, the catalyst was activated at 600 °C in nitrogen for 1 hour before the reaction, and then the reaction gas was introduced at 550 °C. The reaction pressure was 0.1 MPa, the gas flow rate of the reaction gas was 60.5 ml / min for nitrogen, 25.6 ml / min for ethane, 20.5 ml / min for ammonia, and 13.8 ml / min for oxygen. The ethane conversion rate of Catalyst 2# was 55.4%, the selectivity for acetonitrile was 29.6%, and the yield of acetonitrile was 16.3%.

[0028] Example 3 Using an MFI zeolite molecular sieve after dealumination and dehydration with an average pore diameter of 2.3 nm, a specific surface area of 295 m 2The MFI zeolite after dealumination and dehydration with Si / Al = 40 was used as the carrier. 2 wt% of the organic / inorganic Sn component was mixed with the zeolite in an anhydrous and oxygen-free environment and ground for 10 min. Then it was transferred to a furnace under the protection of an inert atmosphere, and calcined at 550 °C for 30 h by passing helium gas to obtain Catalyst 3#.

[0029] The performance of the above catalyst in the ethane ammoxidation reaction was measured on a fixed-bed reactor. The specific reaction conditions were as follows: the catalyst dosage was 100 - 300 mg. Before the reaction, the catalyst was activated at 600 °C for 1 hour under nitrogen, and then the reaction gas was introduced at 500 °C. The reaction pressure was 0.1 MPa. The gas flow rate of the reaction gas was 55 ml / min for nitrogen, 28.6 ml / min for ethane, 24.5 ml / min for ammonia, and 23.8 ml / min for oxygen. The ethane conversion rate of Catalyst 2# was 65.4%, the selectivity for acetonitrile was 40.6%, and the yield of acetonitrile was 26.6%.

[0030] Comparative Example 1 Using the MFI zeolite after dealumination and dehydration with an average pore diameter of 3 nm and a specific surface area of 400 m 2 / g and Si / Al = 50 as the carrier, 3 wt% of the organic / inorganic Sn component was mixed with the zeolite in an anhydrous and oxygen-free environment and ground for 10 min. Then it was transferred to a furnace under the protection of an inert atmosphere, and calcined at 600 °C for 25 h by passing helium gas. After taking it out, it was washed with an aqueous solvent for 2 h, and then centrifuged, filtered, dried, and granulated to obtain Catalyst 4#.

[0031] The performance of the above catalyst in the ethane ammoxidation reaction was measured on a fixed-bed reactor. The specific reaction conditions were as follows: the catalyst dosage was 100 - 300 mg. Before the reaction, the catalyst was activated at 600 °C for 1 hour under nitrogen, and then the reaction gas was introduced at 500 °C. The reaction pressure was 0.1 MPa. The gas flow rate of the reaction gas was 75 ml / min for nitrogen, 23.5 ml / min for ethane, 35.5 ml / min for ammonia, and 16.6 ml / min for oxygen. The ethane conversion rate of Catalyst 3# was 70.5%, the selectivity for acetonitrile was 38.8%, and the yield of acetonitrile was 27.3%.

[0032] Comparative Example 2 Using the MFI zeolite with an average pore diameter of 2.5 nm and a specific surface area of 368 m 2The catalyst 5# was obtained by using the dehydrated MFI zeolite with a Si / Al ratio of 75 as the carrier. 3 wt% of the organic / inorganic Sn component was mixed with the zeolite in an anhydrous and oxygen-free environment and ground for 15 min. Then it was transferred to a hot furnace under the protection of an inert atmosphere, calcined at 600 °C for 15 h with helium gas passing through. After being taken out, it was washed with an aqueous solvent for 4 h, and then centrifuged, filtered, dried, and granulated.

[0033] The performance of the above catalyst in the ethane ammoxidation reaction was measured on a fixed-bed reactor. The specific reaction conditions were as follows: the catalyst dosage was 100 - 300 mg. Before the reaction, the catalyst was activated at 650 °C for 1 h under nitrogen, and then the reaction gas was introduced at 600 °C. The reaction pressure was 0.1 MPa. The gas flow rate of the reaction gas was 75 ml / min for nitrogen, 27 ml / min for ethane, 32.6 ml / min for ammonia, and 22 ml / min for oxygen. The ethane conversion rate of catalyst 4# was 75.4%, the selectivity to acetonitrile was 27.8%, and the yield of acetonitrile was 21%.

[0034] Comparative Example 3 Using the dehydrated MFI zeolite with an average pore diameter of 2 nm and a specific surface area of 432 m 2 / g and a Si / Al ratio of 80 as the carrier, 0.5 wt% of the organic / inorganic Sn component was mixed with the zeolite in an anhydrous and oxygen-free environment and ground for 20 min. Then it was transferred to a hot furnace under the protection of an inert atmosphere, calcined at 600 °C for 10 h with helium gas passing through. After being taken out, it was washed with an aqueous solvent for 2 h, and then centrifuged, filtered, dried, and granulated to obtain the catalyst 6#.

[0035] The performance of the above catalyst in the ethane ammoxidation reaction was measured on a fixed-bed reactor. The specific reaction conditions were as follows: the catalyst dosage was 100 - 300 mg. Before the reaction, the catalyst was activated at 650 °C for 1 h under nitrogen, and then the reaction gas was introduced at 450 °C. The reaction pressure was 0.1 MPa. The gas flow rate of the reaction gas was 80.9 ml / min for nitrogen, 10.6 ml / min for ethane, 25.2 ml / min for ammonia, and 30 ml / min for oxygen. The ethane conversion rate of catalyst 5# was 40.6%, the selectivity to acetonitrile was 18.8%, and the yield of acetonitrile was 7.6%.

Claims

1. An efficient catalyst for preparing acetonitrile by ethane ammoxidation, characterized in that: The MFI type molecular sieve is used as a carrier, and organic tin or inorganic tin is used as an active component, the content of the active component is 0.1wt%-5wt%, and the specific surface area of ​​the MFI type molecular sieve is 200-500m 2 / g, and the average pore size is 1-10nm.

2. The highly efficient catalyst for preparing acetonitrile by ethane ammoxidation as claimed in claim 1, characterized in that: The preparation method described comprises the following steps: subjecting the MFI molecular sieve to dealuminization and water removal treatment, transferring and loading the active component in an anhydrous and oxygen-free environment, and obtaining the catalyst through the steps of grinding, calcining, washing, filtering, drying, and granulating; The active component is organic / inorganic tin.

3. The preparation method according to claim 2, characterized in that: The method comprises the following steps: (1) The molecular sieve used is an MFI type molecular sieve with zeolite Si / Al=40-150; (2) The MFI molecular sieve dealumination is accomplished by stirring, heating and refluxing with a 2-10 mol / L acidic / alkaline solution, and then vacuum drying at a temperature of 50-200°C for 2-6 hours. (3) In a glove box, mix and grind the MFI molecular sieve and 0.1wt%-5wt% of the active component accounting for the total weight of the molecular sieve for 10-30 min; (4) calcining the powder ground in (3) to obtain a Sn / MFI molecular sieve catalyst, wherein the calcination conditions are: in a certain gas protection environment, the calcination temperature is 400-700° C. and maintained for 6-30 hours; (5) The calcined catalyst is poured into a beaker containing a solvent and stirred. The solvent washing time is 2-6 hours; (6) subjecting the substance obtained by solvent washing in (5) to centrifugal filtration at a centrifugal speed of 1500-3000 rpm / min; (7) Drying the Sn / MFI molecular sieve catalyst obtained in (6) in an oven for 8-15 hours at a temperature of 50-80°C; (8) The Sn / MFI molecular sieve catalyst obtained in (7) is granulated into 20-80 mesh particles to obtain the final Sn / MFI catalyst.

4. The preparation method according to claim 3, characterized in that: The active component of step (3) is organic / inorganic Sn.

5. Use of a molecular sieve catalyst prepared by the method for preparing a molecular sieve according to any one of claims 1 to 4 in ethane ammoxidation.