Preparation method and application of modified ZSM-35 molecular sieve catalyst
The removal of surface aluminum and amorphous species of ZSM-35 catalyst through acid treatment method, solving the problem of binder dilution and hole blocking, improving the isomerization activity and stability of the catalyst, and achieving efficient olefin conversion and selectivity , suitable for olefin isomerization reaction.
Patent Information
- Application Number
- CN202211677478.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-26
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2042-12-26
AI Technical Summary
The existing ZSM-35 catalyst contains a large amount of binder during the extrusion process, resulting in the catalyst active center being diluted, the reaction speed becomes larger, the catalyst deactivation is accelerated, and the binder has a hole-blocking effect on the molecular sieve pores, affecting the diffusion performance. , resulting in poor stability.
The molded ZSM-35 molecular sieve was treated by acid treatment to remove the amorphous species in the surface aluminum and pores, and the modified catalyst was obtained by extrusion molding, drying, calcining and acidic solution treatment.
The isomerization activity and stability of the catalyst are improved, the conversion and selectivity of olefins are improved, the conversion rate of butene reaches more than 44%, and the selectivity of isobutene reaches up to 93.1%, and a high mechanical strength is maintained.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of catalyst preparation, in particular to a preparation method of a modified ZSM-35 molecular sieve and application thereof in olefin isomerization reaction. Background Art
[0002] With the rapid development of high value-added fine chemical products, the demand for fine chemical raw materials such as isoolefins is also increasing rapidly. The development of industrial processes for skeletal isomerization of olefins provides a feasible way to increase the production of isoolefins, which has great economic and social benefits. At present, ZSM-35 has been proven to be the best catalyst for the skeletal isomerization reaction of n-butene, and has been industrialized.
[0003] Catalyst powder is very inconvenient in practical application due to its small particle size, and has weaknesses such as difficult recovery, easy deactivation and aggregation, so it needs to be molded in advance. In the molding process, it is generally necessary to add a binder, and the binder content generally accounts for 10-40% of the total weight of the catalyst, or even higher, so that the catalyst has a certain specific shape and a certain mechanical strength. From this point of view, the binder is necessary. The existing industrial ZSM-35 molecular sieve catalyst contains a large amount of binder, but the binder is generally an inert component. The addition of the binder also has a "dilution" effect on the active center of the molecular sieve, which makes the actual reaction space velocity larger, resulting in accelerated catalyst deactivation. In addition, the binder has a certain pore blocking effect on the molecular sieve, which affects the diffusion performance, and ultimately leads to poor catalyst stability. The present invention uses an acid treatment method to treat the molded ZSM-35 molecular sieve to remove the outer surface aluminum of the molecular sieve and remove the amorphous species in the molecular sieve pores to obtain a molded catalyst with high isomerization activity and good stability. The modified catalyst has a positive effect on performance improvement and has important industrial application value. Summary of the invention
[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the current catalyst extrusion molding method, and provide a ZSM-35 molecular sieve after acid treatment molding and its application. The modified catalyst has high isomerization activity and good stability.
[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0006] A method for preparing a modified ZSM-35 molecular sieve catalyst comprises the following steps: extruding, drying, and calcining the ZSM-35 molecular sieve catalyst, placing it in an acidic solution for acid treatment, and finally drying and calcining it again to obtain the modified ZSM-35 molecular sieve catalyst;
[0007] The molar ratio of silicon oxide to aluminum oxide in the ZSM-35 molecular sieve catalyst is 5-15; the extrusion molding makes the diameter of the ZSM-35 molecular sieve catalyst 1.5-5.0 mm; its cross-section is circular, and can also be at least one of strip, clover, cylindrical mesoporous, four-leaf clover, dumbbell, honeycomb, wheel or cross-hole column.
[0008] Preferably, the drying temperature is 80-120° C., and the drying time is 6-12 hours.
[0009] Preferably, the calcination temperature is 450-650° C., and the calcination time is 3-6 hours.
[0010] Preferably, the acidic solution is at least one of a nitric acid solution, a citric acid solution or an acetic acid solution.
[0011] More preferably, the mass concentration of the nitric acid solution is 0.2%-10wt%; the concentration of the citric acid solution is 2%-20wt%; and the mass concentration of the acetic acid solution is 2%-20wt%.
[0012] More preferably, the acidic solution is a mixture of nitric acid solution and citric acid solution in a mass ratio of 0.2-5:2-10, or
[0013] The acidic solution is a mixture of citric acid solution and acetic acid solution in a mass ratio of 2-10:2-10, or,
[0014] The acidic solution is prepared by mixing a nitric acid solution and an acetic acid solution in a mass ratio of 0.2-5:2-10.
[0015] Preferably, the temperature of the acid treatment is 25-120° C., and the treatment time is 1-24 h.
[0016] The present invention also provides a modified ZSM-35 molecular sieve catalyst prepared by the method.
[0017] The present invention also provides an application of the modified ZSM-35 molecular sieve catalyst, wherein the catalyst is applied to olefin isomerization reaction, the reaction temperature is 250-350°C, the space velocity is 1-7h -1 .
[0018] The beneficial effects of the present invention are:
[0019] The invention provides a method for preparing a modified ZSM-35 molecular sieve catalyst. The catalyst prepared by the method has high olefin conversion rate and selectivity. When the catalyst of the invention is used for olefin isomerization reaction, the butene conversion rate reaches more than 44%, and can reach up to 54.3% at the highest. The selectivity of the product isobutylene reaches up to 93.1% at the highest. The reaction performance reaches the effect of an unformed powdered molecular sieve, and the catalyst has high mechanical strength and good application value. DETAILED DESCRIPTION
[0020] The present invention will be further described below in conjunction with the embodiments.
[0021] In the embodiment of the present invention, the molar ratio of silicon oxide to aluminum oxide in the ZSM-35 molecular sieve used is 1:10.5.
[0022] Example 1
[0023] A method for preparing a modified ZSM-35 molecular sieve catalyst, comprising the following steps:
[0024] Weigh 28g of nitric acid (67%), add it to 722g of deionized water, and stir well to make a nitric acid solution;
[0025] 80g of ZSM-35 molecular sieve catalyst was extruded into strips with a diameter of 3.0mm, dried at 120℃ for 10h, calcined at 550℃ for 4h, then placed in a nitric acid solution with slight stirring, heated to 60℃, and kept with slight stirring for 3h; filtered, washed to neutrality, transferred to an oven for drying at 120℃ / 10h, and finally calcined in a muffle furnace at 500℃ for 4h to obtain a nitric acid-modified ZSM-35 molecular sieve catalyst.
[0026] Example 2
[0027] A method for preparing a modified ZSM-35 molecular sieve catalyst, comprising the following steps:
[0028] Weigh 58g of citric acid, add it to 692g of deionized water (7.7%), stir evenly to make a citric acid solution;
[0029] 80g of ZSM-35 molecular sieve catalyst was extruded into strips with a diameter of 3.0mm, dried at 120℃ for 10h, calcined at 550℃ for 4h, then placed in a citric acid solution and gently stirred, heated to 90℃, and kept gently stirred for 12h; filtered and washed until neutral; transferred to an oven for drying at 120℃ / 10h, and finally calcined in a muffle furnace at 500℃ for 4h to obtain a citric acid modified ZSM-35 molecular sieve catalyst.
[0030] Example 3
[0031] A method for preparing a modified ZSM-35 molecular sieve catalyst, comprising the following steps:
[0032] Weigh 54 g of acetic acid, add it to 696 g of deionized water, and stir evenly to prepare an acetic acid solution;
[0033] 80g of ZSM-35 molecular sieve catalyst was extruded into strips with a diameter of 3.0mm, dried at 120℃ for 10h, calcined at 550℃ for 4h, then placed in an acetic acid solution and gently stirred, heated to 90℃, and kept gently stirred for 12h; filtered and washed until neutral; transferred to an oven for drying at 120℃ / 10h, and finally calcined in a muffle furnace at 500℃ for 4h to obtain an acetic acid modified ZSM-35 molecular sieve catalyst.
[0034] Example 4
[0035] A method for preparing a modified ZSM-35 molecular sieve catalyst, comprising the following steps:
[0036] Weigh 28g nitric acid (67%) and 58g citric acid in turn and add them to 664g deionized water, stir evenly, to prepare a mixed acid solution of nitric acid and citric acid;
[0037] 80g of ZSM-35 molecular sieve catalyst was extruded into strips with a diameter of 3.0mm, dried at 120℃ for 10h, calcined at 550℃ for 4h, then placed in a mixed acid solution and gently stirred, heated to 60℃, and kept gently stirred for 3h; filtered and washed until neutral; transferred to an oven for drying at 120℃ / 10h, and finally calcined in a muffle furnace at 500℃ for 4h to obtain a nitric acid and citric acid mixed acid modified ZSM-35 molecular sieve catalyst.
[0038] Example 5
[0039] A method for preparing a modified ZSM-35 molecular sieve catalyst, comprising the following steps:
[0040] Weigh 28g nitric acid (67%) and 54g acetic acid and add them to 668g deionized water. Stir evenly to prepare a mixed acid solution of nitric acid and acetic acid.
[0041] 80g of ZSM-35 molecular sieve catalyst was extruded into strips with a diameter of 3.0mm, dried at 120℃ for 10h, calcined at 550℃ for 4h, then placed in a mixed acid solution and gently stirred, heated to 60℃, and kept gently stirred for 3h; filtered, washed until neutral; transferred to an oven for drying at 120℃ / 10h, and finally calcined in a muffle furnace at 500℃ for 4h to obtain a nitric acid and acetic acid mixed acid modified ZSM-35 molecular sieve catalyst.
[0042] Example 6
[0043] A method for preparing a modified ZSM-35 molecular sieve catalyst, comprising the following steps:
[0044] Weigh 58g of citric acid and 54g of acetic acid, add them into 638g of deionized water, stir evenly, and prepare a mixed acid solution of citric acid and acetic acid;
[0045] 80g of ZSM-35 molecular sieve catalyst was extruded into strips with a diameter of 3.0mm, dried at 120℃ for 10h, calcined at 550℃ for 4h, then placed in a mixed acid solution and gently stirred, heated to 120℃, and kept gently stirred for 12h; filtered and washed until neutral; transferred to an oven for drying at 120℃ / 10h, and finally calcined in a muffle furnace at 500℃ for 4h to obtain a citric acid and acetic acid mixed acid modified ZSM-35 molecular sieve catalyst.
[0046] Embodiment 7-14
[0047] The acid solution is composed of a two-substance combination solution of nitric acid and citric acid. The mass concentration of each species in the solution is shown in Table 1. Other processing conditions are the same as in Example 4.
[0048] Table 1
[0049]
[0050] Embodiment 15
[0051] The activity of the ZSM-35 molecular sieve catalyst prepared in Examples 1-14 was evaluated, and the commercially available industrial ZSM-35 molecular sieve of China Catalyst Co., Ltd. was used as a control.
[0052] Evaluation method: The catalyst activity test is carried out on a fixed bed reactor with a reaction pressure of 0.1MPa. The experimental process is as follows: Weigh 4g of catalyst (20-40 mesh) and 4g of quartz sand (20-40 mesh), mix them and load them into a stainless steel reaction tube with a diameter of 10mm. Before the reaction, the catalyst is heated to the reaction temperature under a nitrogen flow and activated at this temperature for 1h, and then 1-butene raw gas is introduced for reaction. After the reaction is sampled every 4h through a six-way valve, it enters the chromatography analysis system for online analysis, and the liquid product is analyzed offline. Reaction conditions: Reaction conditions: T = 290℃, P = 0.1MPa, space velocity 4h -1 , the results are shown in Table 2:
[0053] Table 2
[0054]
[0055]
[0056] It can be seen from Table 1 that compared with the commercially available catalysts modified by single-substance acid solution, the 1-butene conversion rate and isobutylene selectivity of the modified ZSM-35 molecular sieve prepared by the acid solution of the dual-substance combination are greatly improved, among which the molecular sieve 1-butene conversion rate and isobutylene selectivity obtained by treating with the mixed acid solution composed of 0.8% nitric acid concentration and 2% citric acid concentration in Example 11 are the highest. The above experimental results show that the method of acid treatment molding molecular sieve process has significant advantages, and the catalytic performance is improved while the mechanical strength of the finished product is basically maintained, and it can be used for industrial scale-up production.
[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing a modified ZSM-35 molecular sieve catalyst, characterized in that: The method comprises the following steps: extruding, drying, and calcining the ZSM-35 molecular sieve, placing the ZSM-35 molecular sieve in an acid solution for acid treatment, and finally drying and calcining the ZSM-35 molecular sieve again to obtain a modified ZSM-35 molecular sieve catalyst; The acidic solution is a mixture of a nitric acid solution and a citric acid solution in a mass ratio of 0.2-5:2-10, or The acidic solution is prepared by mixing a citric acid solution and an acetic acid solution in a mass ratio of 2-10:2-10, or, The acidic solution is prepared by mixing a nitric acid solution and an acetic acid solution in a mass ratio of 0.2-5:2-10; The mass concentration of the nitric acid solution is 0.2%-10wt%; the concentration of the citric acid solution is 2%-20wt%, and the mass concentration of the acetic acid solution is 2%-20wt%; the temperature of the acid treatment is 25-120°C, and the treatment time is 1-24h; The drying temperature is 80-120°C, and the drying time is 6-12 hours; the calcining temperature is 450-650°C, and the calcining time is 3-6 hours; The molar ratio of silicon oxide to aluminum oxide in the ZSM-35 molecular sieve is 5-15; the extrusion molding makes the diameter of the ZSM-35 molecular sieve 1.5-5.0 mm.
2. A modified ZSM-35 molecular sieve catalyst, characterized in that: Prepared according to the method of claim 1.
3. An application of the modified ZSM-35 molecular sieve catalyst according to claim 2, characterized in that: The catalyst is applied to olefin isomerization reaction, the reaction temperature is 250-350°C, and the space velocity is 1-7h -1 .