Sn / H-ZSM-5 catalyst for catalyzing ammonia oxidation of ethane to prepare acetonitrile and preparation method of Sn / H-ZSM-5 catalyst

Abstract

The invention discloses a Sn / H-ZSM-5 catalyst for catalyzing ammonia oxidation of ethane to prepare acetonitrile and a preparation method of the Sn / H-ZSM-5 catalyst. The catalyst is obtained by loading Sn on an H-ZSM-5 molecular sieve with a silicon-aluminum molar ratio of 10-25. When the Sn / H-ZSM-5 catalyst provided by the invention is used for preparing the acetonitrile through the ethane ammoxidation reaction, the selectivity of the acetonitrile is relatively high, few byproducts are generated, and the conversion rate of the ethane is 23.3-27%, the selectivity of the acetonitrile can reach 75.2-80.4%, the generation rate of the acetonitrile reaches 100-120 [mu] mol / g / min, and the yield of the acetonitrile is 17.5-21.7%. In addition, after the catalyst is regenerated, good stability and activity are still maintained.

Description

Technical Field

[0001] The invention belongs to the technical field of nitriles or nitrile compounds, and particularly relates to a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to produce acetonitrile and a preparation method thereof. Background Art

[0002] Acetonitrile, as an important organic chemical raw material, is widely used in chemical synthesis fields such as medicine and pesticides. Currently, industrial production of acetonitrile mainly involves recovering by-products from propylene ammoxidation, but this method has problems such as limited acetonitrile production and complex separation and purification. Ethane, as an important component of natural gas and shale gas, has abundant reserves and is relatively inexpensive. Direct production of acetonitrile from ethane ammoxidation has the advantages of abundant raw material sources and high atom economy, making it a highly promising production method. The key to this reaction lies in the development of an efficient catalyst.

[0003] Currently, the catalysts used for the ammoxidation of alkanes are generally divided into mixed metal oxides and metal-modified molecular sieve catalysts. Initially, Aliev et al. used a Cr / Sc-Mo-O catalyst to study the ammoxidation of ethane in the temperature range of 400-500°C, but the highest selectivity for acetonitrile was only 32.2%, accompanied by the formation of a large number of by-products (S.M.A. Aliev & V.D. Sokolovskii. Ammoxidation of ethane on oxide catalysts [J]. React. Kinet. Catal. Lett., 1978 (9): 91-97). Patent SU-738657 mentions a catalyst based on Cr oxide and Mo oxide for the ammoxidation of ethane to produce acetonitrile. Under the conditions of a reaction temperature of 400°C and a contact time of 19 seconds, the maximum acetonitrile yield was only 10 mol%, and no specific by-products were mentioned. Catani et al. studied the effect of alumina-supported Nb-Sb oxide catalysts on the ammoxidation of ethane. At a temperature of approximately 530°C and a contact time of 2.6 seconds, the selectivity for acetonitrile was approximately 50%, with the formation of byproducts such as CO and CO2 (R. Catani & G. Centi. Selective Ethane Ammoxidation to Acetonitrile on Alumina-supported Niobium-Antimony Oxides [J]. J. Chem. Soc., Chem. Commun., 1991: 1081-1083). US Pat. No. 5,756,802 and CN Pat. No. 1,150,146 A proposed the use of metal-modified molecular sieve catalysts to catalyze the ammoxidation of ethane. Specifically, the metals were introduced into the molecular sieves of different topologies by exchanging them with some elements from the fourth period of the periodic table. Among these metals, Co was the best choice. Using Co-ZSM5 molecular sieve catalysts, the acetonitrile production rate was increased by one or two orders of magnitude compared to metal oxide catalysts, but a large number of byproducts were still present.

[0004] Although a variety of catalysts are currently used in the ethane ammoxidation reaction to produce acetonitrile, there are still deficiencies in ethane conversion rate, acetonitrile selectivity and stability, which makes it difficult to meet the needs of industrial production of acetonitrile. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art and provide a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile and a preparation method thereof. The catalyst has high selectivity for acetonitrile in the ethane ammoxidation reaction and produces fewer by-products.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] Provided is a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile, wherein the catalyst is obtained by loading Sn on an H-ZSM-5 molecular sieve having a silicon-aluminum molar ratio of 10 to 25. 4+ The Si in the molecular sieve framework can be occupied by isostructural substitution 4+ The Sn Lewis acid is believed to be the active site for acetonitrile formation. Molecular sieve catalysts with different Si / Al ratios result in different framework aluminum distributions, which can affect the acidity after Sn loading, and thus the selectivity and yield of acetonitrile in the ethane ammoxidation reaction.

[0008] According to the above scheme, the Sn content in the Sn / H-ZSM-5 catalyst is 1 to 3 wt%, preferably 1.8 to 2.1 wt%.

[0009] The present invention also provides a method for preparing the Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile, which comprises the following steps:

[0010] 1) Preparation of H-ZSM-5 molecular sieve: adding an alkali source, water, an aluminum source, and a template agent to a reaction vessel in sequence, stirring thoroughly until completely dissolved, then slowly adding a silicon source dropwise, and continuing stirring until a gel is formed. The resulting gel is then placed in a reactor and transferred to a homogeneous reactor for dynamic crystallization. The resulting product is washed and dried to obtain a ZSM-5 molecular sieve. The resulting ZSM-5 molecular sieve is then ion-exchanged with an ammonium nitrate solution, and then washed, dried, ground, and calcined to obtain an H-ZSM-5 molecular sieve.

[0011] 2) Preparation of Sn / H-ZSM-5 catalyst by atom-planting method: The H-ZSM-5 molecular sieve prepared in step 1) is placed in a quartz tube for heating and vacuum treatment. The quartz tube is connected to a flask with a rubber stopper. After vacuum treatment, anhydrous tin tetrachloride is added to the flask through a needle syringe. The liquid in the flask is then heated to accelerate the volatilization of the liquid so that it can be combined with the H-ZSM-5 molecular sieve framework in the quartz tube. Finally, the product in the quartz tube is washed with methanol to remove SnO x species, and then dried to obtain Sn / H-ZSM-5 catalyst.

[0012] According to the above scheme, the alkali source in step 1) is sodium hydroxide.

[0013] According to the above scheme, the aluminum source in step 1) is one of aluminum chloride and sodium metaaluminate or a mixture of the two, preferably sodium metaaluminate.

[0014] According to the above scheme, the template agent in step 1) is one or more of tetramethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium hydroxide, and tetraethylammonium bromide, preferably tetrapropylammonium hydroxide.

[0015] According to the above scheme, the silicon source in step 1) is tetraethyl orthosilicate.

[0016] According to the above scheme, step 1) adds an alkali source, water, an aluminum source, and a template agent to a reaction vessel in sequence. The molar ratio of silicon in the silicon source to aluminum in the aluminum source is 10 to 20, the mass ratio of the alkali source to the aluminum source is 1:2 to 14, the mass ratio of deionized water to the aluminum source is 8 to 205:1, and the mass ratio of the template agent to the aluminum source is 15 to 105:1. When the raw material silicon-to-aluminum ratio is within the range of 10 to 20, a catalyst for the ethane ammoxidation reaction to produce acetonitrile with high selectivity for acetonitrile and low byproduct production can be obtained. A molecular sieve is difficult to prepare with a silicon-to-aluminum ratio below 10, and the catalyst performance is poor when the silicon-to-aluminum ratio is above 20.

[0017] According to the above scheme, the dynamic crystallization conditions in step 1) are: dynamic crystallization temperature is 150-200° C., and dynamic crystallization time is 48-72 h.

[0018] According to the above scheme, in step 1), the method for ion exchange between ZSM-5 molecular sieve and ammonium nitrate solution is as follows: ZSM-5 molecular sieve is mixed with 0.5-1.5 mol / L ammonium nitrate solution at a mass volume ratio of 1 g of molecular sieve / 20-120 mL, and the ion exchange is carried out by heating at 50-100° C. for 1-12 hours, and a total of 1-5 ion exchanges are carried out.

[0019] According to the above scheme, in step 2), the heating temperature of the H-ZSM-5 molecular sieve is 400-600°C.

[0020] According to the above scheme, step 2) vacuum treatment is performed by vacuuming to 0.3-0.5 MPa.

[0021] According to the above scheme, in step 2), the heating temperature of the flask is 40-80° C., the mass volume ratio of the H-ZSM-5 molecular sieve and anhydrous tin tetrachloride is 1 g / 1-5 mL, and the heating time of the liquid in the flask is 48-72 h.

[0022] The present invention also includes the use of the Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to produce acetonitrile in catalyzing the ammoxidation of ethane to produce acetonitrile.

[0023] The present invention also includes a method for producing acetonitrile by catalyzing ethane ammoxidation using the above-mentioned Sn / H-ZSM-5 catalyst: first, the Sn / H-ZSM-5 catalyst is heated under an inert atmosphere for activation treatment, and after activation, a reaction gas and a carrier gas are introduced, wherein the reaction gas is a mixture of C2H6, NH3 and O2, and N2 is used as a carrier gas, and the ethane ammoxidation reaction is carried out at 450-550°C.

[0024] According to the above scheme, the activation treatment temperature is 550-650°C, and the activation treatment time is 30-60 minutes.

[0025] According to the above scheme, the volume percentage of nitrogen in the reaction gas and carrier gas is 55-65%, and the space velocity of the reaction gas and carrier gas is 55000-65000h -1 .

[0026] According to the above scheme, the molar ratio of C2H6, NH3 and O2 in the reaction gas is 10:8 to 10:5 to 8.

[0027] The present invention optimizes the synthesis conditions (silicon-aluminum ratio) of an H-ZSM-5 molecular sieve to obtain a molecular sieve with a higher acid content. Then, a metal is loaded on the H-ZSM-5 molecular sieve by an atomic implantation method. The results show that, under the same silicon-aluminum ratio, the molecular sieve synthesized using tetraethyl orthosilicate as a silicon source has a better catalytic effect of loaded Sn metal. Under the same silicon source and different silicon-aluminum ratios, when the silicon-aluminum ratio in the catalyst is 10-25, the catalytic effect is the best, the ethane conversion rate is the highest, and the acetonitrile selectivity is also the highest.

[0028] The present invention has the following beneficial effects: 1. The Sn / H-ZSM-5 catalyst provided by the present invention has high selectivity for acetonitrile and produces fewer by-products when used in the ethane ammoxidation reaction to produce acetonitrile. When the ethane conversion rate is 23.3-27%, the acetonitrile selectivity can reach 75.2-80.4%, the acetonitrile production rate reaches 100-120 μmol / g / min, and the acetonitrile yield is 17.5-21.7%. In addition, after regeneration, the catalyst still maintains good stability and activity. 2. The preparation method of the present invention has relatively simple steps, good reproducibility, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 XRD patterns of ZSM-5 molecular sieves and catalyst samples prepared in Examples 1-2 and Comparative Examples 1-6 of the present invention;

[0030] Figure 2 The SEM images of the ZSM-5 molecular sieves prepared in Examples 1-2 and Comparative Examples 1-2 are shown;

[0031] Figure 3SEM images of the Sn / H-ZSM-5 catalyst samples prepared in Examples 1-2 and Comparative Examples 1-2;

[0032] Figure 4 The SEM images of the ZSM-5 molecular sieve and catalyst samples prepared in Comparative Examples 3-4 are shown;

[0033] Figure 5 These are SEM images of the ZSM-5 molecular sieve and catalyst samples prepared in Comparative Examples 5-6. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0035] Example 1

[0036] A Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile, wherein the preparation method thereof is as follows:

[0037] 1) Preparation of H-ZSM-5 molecular sieve: 0.1033 g of sodium hydroxide, 37.6439 g of deionized water, 1.1907 g of sodium aluminate and 18.9234 g of tetrapropylammonium hydroxide were added to a 250 mL beaker in sequence, stirred thoroughly until completely dissolved, and then 31.2488 g of ethyl orthosilicate was slowly added dropwise. Stirring was continued until a gel was formed. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization. Dynamic crystallization was carried out at 175° C. for 3 days. The product was centrifugally washed with deionized water until neutral, and then dried at 80°C for 12 to 24 hours to obtain a ZSM-5 molecular sieve (Si / Al=10). The obtained ZSM-5 molecular sieve was mixed with a 1 mol / L ammonium nitrate solution at a mass ratio of 1 g molecular sieve to 50 mL ammonium nitrate solution, and ion exchange was performed in a 70°C water bath for a total of three ion exchanges. The product was then washed with deionized water and dried at 80°C for 12 hours. After drying, it was ground and finally calcined at 550°C for 6 hours to obtain 4.7 g of H-ZSM-5 molecular sieve (named H-ZSM-5-T-10, where T represents tetraethyl orthosilicate).

[0038] 2) Prepare Sn / H-ZSM-5 catalyst by loading Sn on H-ZSM-5 molecular sieve using atomic implantation method: 1 g of H-ZSM-5 molecular sieve prepared in step 1) is placed in a quartz tube for heating and vacuum treatment. The quartz tube is connected to a flask with a rubber stopper. The quartz tube is heated at a temperature of 500° C. and the vacuum degree is 0.4 MPa. After the vacuum is completed, 3 mL of anhydrous tin tetrachloride liquid (purity ≥99.0 wt%) is added to the flask through a needle syringe. The liquid in the flask is then heated to 80° C. to accelerate the volatilization rate of the liquid and allow it to combine with the H-ZSM-5 molecular sieve framework in the quartz tube. The heating temperature of the quartz tube and the flask is maintained for 48 hours. Finally, the product in the quartz tube is washed 5 times with methanol to remove SnO x The species was then dried at 60 °C to obtain Sn-loaded H-ZSM-5 catalyst, and the sample was named Sn / H-ZSM-5-T-10.

[0039] The actual silicon-to-aluminum ratio of the H-ZSM-5-T-10 prepared in step 1) of this embodiment was measured by an Oxford Instruments Ultim Max X-ray energy dispersive spectrometer (EDS) to be 11.2, the actual silicon-to-aluminum ratio of the Sn / H-ZSM-5-T-10 prepared in step 2) to be 13.4, and the Sn loading was 2.0 wt%.

[0040] Example 2

[0041] A Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile, the specific preparation method is similar to that of Example 1, except that the ZSM-5 molecular sieve Si / Al=18 (named H-ZSM-5-T-18) prepared in step 1) is specifically prepared as follows:

[0042] To a 250 mL beaker, 0.2600 g of sodium hydroxide, 37.6400 g of deionized water, 0.6933 g of sodium aluminate, and 18.9227 g of tetrapropylammonium hydroxide were added in sequence, and the mixture was stirred thoroughly until completely dissolved. Then, 31.2488 g of ethyl orthosilicate was slowly added dropwise, and stirring was continued until a gel was formed. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization. Dynamic crystallization was carried out at 175° C. for 3 days. The remaining steps were the same as in Example 1.

[0043] The Sn-loaded H-ZSM-5 catalyst sample prepared in this example is named Sn / H-ZSM-5-T-18.

[0044] The actual silicon-to-aluminum ratio of H-ZSM-5-T-18 prepared in this example was measured to be 18.6, the actual silicon-to-aluminum ratio of Sn / H-ZSM-5-T-18 was 20.6, and the Sn loading was 2.1 wt%.

[0045] Comparative Example 1

[0046] A Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile, the specific preparation method is similar to that of Example 1, except that the ZSM-5 molecular sieve Si / Al=30 (named H-ZSM-5-T-30) prepared in step 1) is specifically prepared as follows:

[0047] To a 250 mL beaker, 0.4109 g of sodium hydroxide, 37.6404 g of deionized water, 0.4130 g of sodium aluminate, and 18.9227 g of tetrapropylammonium hydroxide were added in sequence. After thorough stirring until completely dissolved, 31.2436 g of ethyl orthosilicate was slowly added dropwise. Stirring was continued until a gel was formed. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization. Dynamic crystallization was carried out at 175° C. for 3 days. The remaining steps were the same as in Example 1.

[0048] The Sn-loaded H-ZSM-5 catalyst sample prepared in this comparative example is named Sn / H-ZSM-5-T-30.

[0049] The actual silicon-aluminum ratio of H-ZSM-5-T-30 prepared in this comparative example was measured to be 28.9, the actual silicon-aluminum ratio of Sn / H-ZSM-5-T-30 was 33.8, and the Sn loading was 2.0 wt%.

[0050] Comparative Example 2

[0051] A Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile, the specific preparation method is similar to that of Example 1, except that the ZSM-5 molecular sieve Si / Al=68 (named H-ZSM-5-T-68) prepared in step 1) is as follows:

[0052] To a 250 mL beaker, 0.5347 g of sodium hydroxide, 37.6477 g of deionized water, 0.1800 g of sodium aluminate, and 18.9261 g of tetrapropylammonium hydroxide were added in sequence. After thorough stirring until completely dissolved, 31.2468 g of ethyl orthosilicate was slowly added dropwise. Stirring was continued until a gel was formed. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization. Dynamic crystallization was carried out at 175° C. for 3 days. The remaining steps were the same as in Example 1.

[0053] The Sn-loaded H-ZSM-5 catalyst sample prepared in this comparative example was named Sn / H-ZSM-5-T-68.

[0054] The actual silicon-aluminum ratio of H-ZSM-5-T-68 prepared in this comparative example was measured to be 67.2, the actual silicon-aluminum ratio of Sn / H-ZSM-5-T-68 was 69.2, and the Sn loading was 2.0 wt%.

[0055] Comparative Example 3

[0056] Sn / H-ZSM-5 catalyst was prepared using LUDOX HS-40 silica sol as the silicon source. The preparation method is as follows:

[0057] To a 250 mL beaker, 0.1054 g of sodium hydroxide, 12.1363 g of deionized water, 1.4003 g of sodium aluminate, 41.7432 g of tetrapropylammonium hydroxide, and 25.4965 g of LUDOX HS-40 silica sol were added in sequence, and 1-2 drops of seed solution were added dropwise. The mixture was stirred until it became a gel. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization. Dynamic crystallization was carried out at 175° C. for 3 days. The remaining steps were the same as in Example 1.

[0058] The seed solution used in this comparative example was prepared as follows: 151.9 g of deionized water was weighed, 1.2 g of sodium metaaluminate, 8.4 g of boric acid, and 11.9 g of tetrapropylammonium hydroxide were added in sequence, and after the above solutions were evenly mixed, 6.2 g of LUDOXHS-40 silica sol was slowly added, and the mixture was stirred continuously for 3 h using a magnetic stirrer to obtain a mixed gel. The mixed gel was placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization at 175° C. for 120 h to obtain a ZSM-5 seed solution.

[0059] The ZSM-5 molecular sieve prepared in this comparative example is named H-ZSM-5-S-10 (S represents silica sol), and the prepared Sn-loaded H-ZSM-5 catalyst sample is named Sn / H-ZSM-5-S-10.

[0060] The actual silicon-to-aluminum ratio of H-ZSM-5-S-10 prepared in this comparative example was measured to be 9.7, the actual silicon-to-aluminum ratio of Sn / H-ZSM-5-T-10 was 12.5, and the Sn loading was 2.0 wt%.

[0061] Comparative Example 4

[0062] Sn / H-ZSM-5 catalyst was prepared using LUDOX HS-40 silica sol as the silicon source. The preparation method is as follows:

[0063] To a 250 mL beaker, 0.4087 g of sodium hydroxide, 12.1317 g of deionized water, 0.8480 g of sodium aluminate, 41.7547 g of tetrapropylammonium hydroxide, and 25.4968 g of LUDOX HS-40 silica sol were added in sequence, and 1-2 drops of seed solution were added dropwise. The mixture was stirred until it became a gel. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization. Dynamic crystallization was carried out at 175° C. for 3 days. The remaining steps were the same as in Example 1.

[0064] The ZSM-5 molecular sieve prepared in this comparative example was named H-ZSM-5-S-16, and the prepared Sn-loaded H-ZSM-5 catalyst sample was named Sn / H-ZSM-5-S-16.

[0065] The actual silicon-to-aluminum ratio of H-ZSM-5-S-16 prepared in this comparative example was measured to be 14.4, the actual silicon-to-aluminum ratio of Sn / H-ZSM-5-T-16 was 17.6, and the Sn loading was 2.0 wt%.

[0066] Comparative Example 5

[0067] Sn / H-ZSM-5 catalyst was prepared using gas phase SiO2 as silicon source. The preparation method is as follows:

[0068] To a 250 mL beaker, 0.0967 g of sodium hydroxide, 32.2781 g of deionized water, 1.2447 g of sodium aluminate, 36.8421 g of tetrapropylammonium hydroxide, and 8.95 g of fumed SiO2 were added in sequence and stirred until a gel formed. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization at 175°C for 3 days. The catalyst was subsequently prepared according to the method in Example 1.

[0069] The ZSM-5 molecular sieve prepared in this comparative example is named H-ZSM-5-G-10 (G represents gas-phase SiO2), and the prepared Sn-loaded H-ZSM-5 catalyst sample is named Sn / H-ZSM-5-G-10.

[0070] The actual silicon-aluminum ratio of H-ZSM-5-G-10 prepared in this comparative example was measured to be 9.4, the actual silicon-aluminum ratio of Sn / H-ZSM-5-G-10 was 11.7, and the Sn loading was 2.0 wt%.

[0071] Comparative Example 6

[0072] Sn / H-ZSM-5 catalyst was prepared using gas phase SiO2 as silicon source. The preparation method is as follows:

[0073] To a 250 mL beaker, 0.3599 g of sodium hydroxide, 32.2793 g of deionized water, 0.7461 g of sodium aluminate, 36.8458 g of tetrapropylammonium hydroxide, and 8.90 g of fumed SiO2 were added in sequence and stirred until a gel formed. The resulting gel was then placed in a polytetrafluoroethylene-lined reactor and transferred to a homogeneous reactor for dynamic crystallization at 175°C for 3 days. The catalyst was subsequently prepared according to the method in Example 1.

[0074] The ZSM-5 molecular sieve prepared in this comparative example was named H-ZSM-5-G-16, and the prepared Sn-loaded H-ZSM-5 catalyst sample was named Sn / H-ZSM-5-G-16.

[0075] The actual silicon-aluminum ratio of the H-ZSM-5-G-16 molecular sieve prepared in this comparative example was measured to be 17.9, the actual silicon-aluminum ratio of Sn / H-ZSM-5-G-16 was 16.9, and the Sn loading was 2.0 wt%.

[0076] Figure 1 The XRD patterns of the ZSM-5 molecular sieves and catalyst samples prepared in Examples 1-2 and Comparative Examples 1-6 show that the ZSM-5 molecular sieves synthesized from the three silicon sources and the Sn / H-ZSM-5 catalyst have a topological structure similar to that of a typical MFI molecular sieve, have a high crystallinity and no obvious impurity phase, which indicates that the introduction of Sn does not destroy the original MFI topological structure of the H-ZSM-5 molecular sieve.

[0077] Figure 2 The SEM images of the ZSM-5 molecular sieves prepared in Example 1-2 and Comparative Example 1-2 show that the obtained molecular sieves are spherical particles with a relatively uniform particle size distribution and an average particle size between 250-400 nm. Figure 3 The SEM images of the Sn / H-ZSM-5 catalyst samples prepared in Example 1-2 and Comparative Example 1-2 show that the molecular sieve maintains its original particle size after being loaded with Sn, indicating that the introduction of Sn does not destroy the original structure of the molecular sieve.

[0078] Figure 4 The SEM images of the ZSM-5 molecular sieve and catalyst samples prepared in Comparative Examples 3-4 show that the original structure of the molecular sieve is not destroyed after Sn loading.

[0079] Figure 5 The SEM images of the ZSM-5 molecular sieve and catalyst samples prepared in Comparative Examples 5-6 show that the original structure of the molecular sieve is not destroyed after Sn loading.

[0080] Comparative Example 7

[0081] Catalysts loaded with different metals (Co, Zn, Mo, and Ni) were prepared using an in-situ atomic transplantation method similar to that of Example 1. The theoretical metal loading was 2 wt %. In step 2), 0.99 g of a 0.034 mol / L aqueous solution of cobalt nitrate hexahydrate, 0.10 g of a 0.007 mol / L aqueous solution of zinc chloride, 1.0 g of a 0.035 mol / L aqueous solution of molybdenum trioxide, and 1.0 g of a 0.034 mol / L aqueous solution of nickel nitrate hexahydrate were added to the flask via a needle syringe, replacing 3 mL of anhydrous tin tetrachloride solution. Subsequent steps and reaction conditions were consistent with those for the Sn loading protocol of Example 1. The resulting products were named Co / H-ZSM-5-T-10, Zn / H-ZSM-5-T-10, Mo / H-ZSM-5-T-10, and Ni / H-ZSM-5-T-10, respectively.

[0082] The catalyst prepared above was tested:

[0083] 1. Catalytic activity test

[0084] The activity of the catalysts prepared in Examples 1-2 of the present invention and Comparative Examples 1-6 in the catalytic oxidation of ethane to produce acetonitrile was tested using a fixed bed reactor and a GC chromatographic detector. The specific test method was as follows: the catalyst powder sample was sieved and granulated (20-40 mesh), 100 mg was taken and loaded into a fixed bed reactor with an inner diameter of 15 mm, and the catalyst was first activated at 600 ° C. in an N2 atmosphere for 30 min. Then, the reaction gas and carrier gas (N2) were introduced. The reaction gas was a mixture of C2H6, NH3 and O2, and the specific flow rates were: N260.9 mL / min, C2H616.6 mL / min, NH320.0 mL / min, O29.1 mL / min (the instruction manual mentioned a space velocity of 64000 h -1 After the inlet gas stabilized, ethane ammoxidation was tested at 550°C. Experimental data was collected every 50 minutes for a total of 550 minutes, and the reaction products were analyzed online using a GC detector. The results showed that the catalyst maintained good stability during the 550-minute reaction. The experimental data at the highest acetonitrile yield during the reaction time (acetonitrile yield = ethane conversion × acetonitrile selectivity) were selected. The specific results are shown in Table 1.

[0085] Table 1

[0086]

[0087] As shown in Table 1, the ethane ammoxidation reaction primarily produces acetonitrile and ethylene, along with small amounts of methane and carbon oxides (primarily CO and CO2). The table also reveals that, for the three catalyst types, acetonitrile selectivity decreases with increasing Si / Al ratios, while ethylene selectivity increases. Among them, the catalyst synthesized using tetraethyl orthosilicate as the silicon source exhibits the best catalytic performance. When the theoretical Si / Al ratio in the catalyst is 10-18, acetonitrile selectivity reaches 75.2-80.4%, ethane conversion reaches 23.3-27%, and yields reach 17.5-21.7%. However, selectivity for byproducts such as methane and carbon oxides is relatively low.

[0088] 2. Catalytic activity test after regeneration

[0089] The catalysts after the above catalytic activity test were heated at 550°C in an oxygen atmosphere for 6 hours for regeneration. The regenerated catalyst samples were recorded as regenerated Sn / H-ZSM-5-T-10, regenerated Sn / H-ZSM-5-T-18, regenerated Sn / H-ZSM-5-T-30, regenerated Sn / H-ZSM-5-T-68, regenerated Sn / H-ZSM-5-S-10, regenerated Sn / H-ZSM-5-S-16, regenerated Sn / H-ZSM-5-G-10, and regenerated Sn / H-ZSM-5-G-16. The catalytic activity test was then carried out using the same method as the above catalytic activity test. The test results are shown in Table 2.

[0090] Table 2

[0091]

[0092] It can be seen from Table 2 that the catalyst still maintains high activity and stability after regeneration.

[0093] 3. Catalytic activity test of catalysts loaded with different metals by atomic implantation method

[0094] The catalytic activity of the catalyst prepared in Comparative Example 7 was tested using the same method as the above catalytic activity test. The test results are shown in Table 3.

[0095] Table 3

[0096]

[0097] As can be seen from Table 3, the catalytic effect of the Co / Zn / Mo / Ni loaded catalyst prepared by the atomic implantation method on the ethane ammoxidation reaction is not so ideal, the acetonitrile selectivity is low, and more CO2 is produced.

[0098] 4. Determination of acid content of H-ZSM-5 molecular sieve and catalyst

[0099] Based on semi-quantitative analysis, pyridine adsorption infrared spectroscopy (Py-FTIR) was used to determine the acid amounts of B acid and L acid in the H-ZSM-5 molecular sieves prepared in Examples 1-2 and Comparative Examples 1-6 and the catalysts after loading Sn. The test results are shown in Table 4.

[0100] Table 4

[0101]

[0102] As can be seen from Table 4, on the H-ZSM-5 molecular sieve, with the increase of the silicon-aluminum ratio, the amount of both B acid and L acid showed a downward trend, and the L / B (L acid amount / B acid amount ratio) also decreased. It is worth noting that under the same silicon-aluminum ratio, the molecular sieve catalyst loaded with Sn significantly reduced the amount of B acid and significantly increased the amount of L acid compared to the H-type mother molecular sieve, but the total acid amount decreased. This may be because the Sn loading process belongs to an acidic environment, and "dealuminization and tin supplementation" occurred. Dealumination led to a decrease in the content of B acid; the introduction of Sn increased the content of L acid. Under the condition of the same catalyst silicon source and different silicon-aluminum ratios, a higher L / B ratio (L / B>1) is more conducive to the formation of acetonitrile.

[0103] 5. Determination of Sn-L acid content of Sn / H-ZSM-5 catalyst

[0104] In Sn / H-ZSM-5 molecular sieve, Sn 4+ By isostructural substitution, Si in the molecular sieve framework is occupied 4+ position, thus forming a closed Sn site [Sn-(OSi≡)4], while the open Sn site is divided into a hydrolysis-type open site and a defect-type open site. The hydrolysis-type open site is due to the closed Sn site reacting with water molecules to hydrolyze a Sn-O-Si bond, thereby generating a hydrolysis-type open site with a proximal Si-OH group [(HO)-Sn-(OSi≡)3-HO-Si], and the defect-type open site is partially bound to the hydroxylated Si(Ⅳ) site of the molecular sieve framework [(HO)-Sn-(OSi≡)3].

[0105] Based on semi-quantitative analysis, the Sn-L acid content of the Sn / H-ZSM-5 catalysts prepared in Examples 1-2 and Comparative Examples 1-6 was determined using deuterated acetonitrile infrared spectroscopy, which included open Sn sites and closed Sn sites. The specific results are shown in Table 5.

[0106] Table 5

[0107]

[0108] Table 5 shows that, for the three catalyst series, with the same silicon source, the lower the Si / Al ratio, the greater the total Sn-L acid content. Sn-L acid is considered the active site for acetonitrile formation, which corresponds well to the catalytic data in Table 1. The total Sn-L acid site content of the catalyst gradually decreases with increasing Si / Al ratio, and it can be observed that the selectivity for acetonitrile also decreases with decreasing total Sn-L acid content.

[0109] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile, characterized in that: The catalyst is obtained by loading Sn on H-ZSM-5 molecular sieve with a silicon-aluminum molar ratio of 10-25.

2. The Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile according to claim 1, wherein The Sn content in the Sn / H-ZSM-5 catalyst is 1-3 wt%.

3. A method for preparing a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile according to claim 1 or 2, characterized in that: The specific steps are as follows: 1) Preparation of H-ZSM-5 molecular sieve: adding an alkali source, water, an aluminum source, and a template agent to a reaction vessel in sequence, stirring thoroughly until completely dissolved, then slowly adding a silicon source dropwise, and continuing stirring until a gel is formed. The resulting gel is then placed in a reactor and transferred to a homogeneous reactor for dynamic crystallization. The resulting product is washed and dried to obtain a ZSM-5 molecular sieve. The resulting ZSM-5 molecular sieve is then ion-exchanged with an ammonium nitrate solution, and then washed, dried, ground, and calcined to obtain an H-ZSM-5 molecular sieve. 2) Preparation of Sn / H-ZSM-5 catalyst by atomic implantation: The H-ZSM-5 molecular sieve prepared in step 1) is placed in a quartz tube for heating and vacuum treatment. The quartz tube is connected to a flask with a rubber stopper. After vacuum treatment, anhydrous tin tetrachloride is added to the flask through a needle syringe. The liquid in the flask is then heated to accelerate the volatilization of the liquid so that it is combined with the H-ZSM-5 molecular sieve framework in the quartz tube. Finally, the product in the quartz tube is washed with methanol to remove SnO x species, and then dried to obtain Sn / H-ZSM-5 catalyst.

4. The method for preparing a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile according to claim 3, wherein: The alkali source in step 1) is sodium hydroxide; the aluminum source in step 1) is one of aluminum chloride and sodium metaaluminate or a mixture of the two; the template in step 1) is one or more of tetramethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium hydroxide, and tetraethylammonium bromide; and the silicon source in step 1) is tetraethyl orthosilicate.

5. The method for preparing a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile according to claim 3, wherein: Step 1) An alkali source, water, an aluminum source, and a template are sequentially added to a reaction vessel, wherein the molar ratio of the silicon element in the silicon source to the aluminum element in the aluminum source is 10 to 20, the mass ratio of the alkali source to the aluminum source is 1:2 to 14, the mass ratio of the deionized water to the aluminum source is 8 to 205:1, and the mass ratio of the template to the aluminum source is 15 to 105:

1.

6. The method for preparing a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile according to claim 3, wherein: The dynamic crystallization conditions in step 1) are as follows: a dynamic crystallization temperature of 150 to 200° C. and a dynamic crystallization time of 48 to 72 h. The method for ion exchange between the ZSM-5 molecular sieve and the ammonium nitrate solution in step 1) is as follows: the ZSM-5 molecular sieve is mixed with a 0.5 to 1.5 mol / L ammonium nitrate solution at a mass volume ratio of 1 g of molecular sieve to 20 to 120 mL, and the ion exchange is carried out by heating at 50 to 100° C. for 1 to 12 h, and a total of 1 to 5 ion exchanges are carried out.

7. The method for preparing a Sn / H-ZSM-5 catalyst for catalyzing the ammoxidation of ethane to acetonitrile according to claim 3, wherein: Step 2) the H-ZSM-5 molecular sieve is heated at a temperature of 400 to 600° C.; Step 2) the flask is heated at a temperature of 40 to 80° C., the mass volume ratio of the H-ZSM-5 molecular sieve to anhydrous tin tetrachloride is 1 g / 1 to 5 mL, and the heating time of the liquid in the flask is 48 to 72 h.

8. Use of the Sn / H-ZSM-5 catalyst for catalytic ethane ammoxidation to acetonitrile according to claim 1 or 2 in catalytic ethane ammoxidation to produce acetonitrile.

9. A method for producing acetonitrile by catalyzing the ammoxidation of ethane using a Sn / H-ZSM-5 catalyst according to claim 1 or 2, characterized in that: First, the Sn / H-ZSM-5 catalyst is heated under an inert atmosphere for activation treatment. After activation, the reaction gas and carrier gas are introduced. The reaction gas is a mixture of C2H6, NH3 and O2, and N2 is used as a carrier gas. The ethane ammoxidation reaction is carried out at 450-550°C.

10. The method for producing acetonitrile by catalyzing ethane ammoxidation using a Sn / H-ZSM-5 catalyst for catalyzing ethane ammoxidation to acetonitrile according to claim 9, wherein: The activation treatment temperature is 550-650°C, the activation treatment time is 30-60 min; the volume percentage of nitrogen in the reaction gas and carrier gas is 55-65%, and the space velocity of the reaction gas and carrier gas is 55000-65000 h -1 ; The molar ratio of C2H6, NH3 and O2 in the reaction gas is 10:8~10:5~8.

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