阅读说明：本技术 Mtbe裂解制丙烯催化剂及其制备方法和应用 (Catalyst for preparing propylene by MTBE cracking and preparation method and application thereof ) 是由 刘红梅 王定博 亢宇 于 2020-05-26 设计创作，主要内容包括：本发明涉及石油化工领域,公开了一种MTBE裂解制丙烯催化剂及其制备方法和应用。所述MTBE裂解制丙烯催化剂包括SAPO-34沸石分子筛、高比表面积全硅介孔分子筛、第一氧化物和第二氧化物；其中,以所述催化剂的总重量为基准,所述SAPO-34沸石分子筛的含量为35-65重量％,所述高比表面积全硅介孔分子筛的含量为15-45重量％,所述第一氧化物的含量为8-25重量％,所述第二氧化物的含量为1-11重量％。该催化剂用于MTBE裂解制丙烯的裂解反应中,能够较好地提高产品中丙烯和乙烯的含量。(The invention relates to the field of petrochemical industry, and discloses a catalyst for preparing propylene by MTBE cracking, and a preparation method and application thereof. The MTBE cracking propylene preparation catalyst comprises a SAPO-34 zeolite molecular sieve, a high-specific surface area all-silicon mesoporous molecular sieve, a first oxide and a second oxide; wherein, based on the total weight of the catalyst, the content of the SAPO-34 zeolite molecular sieve is 35-65 wt%, the content of the high specific surface area all-silicon mesoporous molecular sieve is 15-45 wt%, the content of the first oxide is 8-25 wt%, and the content of the second oxide is 1-11 wt%. The catalyst is used in the cracking reaction of preparing propylene by MTBE cracking, and can better improve the content of propylene and ethylene in the product.)

1. An MTBE cracking propylene preparation catalyst, which is characterized by comprising a SAPO-34 zeolite molecular sieve, a high-specific surface area all-silicon mesoporous molecular sieve, a first oxide and a second oxide; wherein, based on the total weight of the catalyst, the content of the SAPO-34 zeolite molecular sieve is 35-65 wt%, the content of the high specific surface area all-silicon mesoporous molecular sieve is 15-45 wt%, the content of the first oxide is 8-25 wt%, and the content of the second oxide is 1-11 wt%.

2. The catalyst of claim 1, wherein the weight ratio of the SAPO-34 zeolite molecular sieve to the high specific surface area all-silicon mesoporous molecular sieve is (0.7-4.3): 1, preferably (1-3.5): 1, more preferably (1.2-2.6): 1.

3. the catalyst as claimed in claim 1 or 2, wherein the high specific surface area all-silicon mesoporous molecular sieve has a specific surface area of 800-1400m²Per g, pore volume of 0.7-1.7cm³(ii)/g, average pore diameter is 2-4 nm; preferably, the specific surface area of the high specific surface area all-silicon mesoporous molecular sieve is 950-1300m²Per g, pore volume of 1.1-1.6cm³(ii)/g, the average pore diameter is 3-4 nm.

4. The catalyst of any one of claims 1-3, wherein the process for preparing the high specific surface area all-silicon mesoporous molecular sieve comprises:

(S1) under the hydrolysis condition, mixing and contacting a template agent, ethyl orthosilicate and an ammonia water solution to obtain a mixture, and crystallizing, filtering, washing and drying the mixture to obtain high-specific surface area all-silicon mesoporous molecular sieve raw powder;

(S2) removing the template agent in the high specific surface area mesoporous material raw powder to obtain the high specific surface area all-silicon mesoporous molecular sieve.

5. The catalyst according to claim 4, wherein, in step (S1), the template agent is a cationic surfactant;

preferably, the molar ratio of the tetraethoxysilane, the template agent, the ammonia and the water is 1: (0.1-1): (0.5-5): (50-500), preferably 1: (0.2-0.6): (1-4): (100-);

preferably, the conditions of the hydrolysis include: the temperature is 20-60 deg.C, and the time is 20-120 min.

Preferably, the crystallization conditions include: the temperature is 40-140 ℃, and the time is 5-120 h;

preferably, the drying conditions include: the temperature is 70-140 ℃ and the time is 4-20 h.

6. The catalyst of claim 4, wherein in step (S2), the conditions for removal include: the temperature is 450 ℃ and 650 ℃, and the time is 4-30 h.

7. The catalyst according to any one of claims 1 to 6, wherein the first oxide is an oxide obtained by calcining a binder; preferably, the binder is selected from one or more of the group consisting of an aluminum sol, pseudo-boehmite, aluminum hydroxide xerogel and a silica sol.

8. The catalyst of any one of claims 1-7, wherein the second oxide is an alkaline earth oxide; preferably, the second oxide is selected from one or more of calcium oxide, magnesium oxide, beryllium oxide and strontium oxide.

9. The catalyst according to any one of claims 1 to 8, wherein the specific surface area of the catalyst is 300-600m²Per g, pore volume of 0.4-0.8cm³(ii)/g; preferably, the specific surface area of the catalyst is 400-550m²Per g, pore volume of 0.45-0.65cm³/g。

10. A method for preparing a catalyst according to any one of claims 1 to 9, comprising:

(1) in the presence of dilute nitric acid, mixing an SAPO-34 zeolite molecular sieve, a high-specific surface area all-silicon mesoporous molecular sieve, an adhesive and an extrusion aid, then carrying out extrusion forming, drying and first roasting treatment to obtain a catalyst precursor;

(2) and (3) dipping the catalyst precursor into an aqueous solution containing a second oxide precursor, and carrying out second roasting treatment on the obtained solid product to obtain the catalyst for preparing the propylene by cracking the MTBE.

11. The method of claim 10, wherein the extrusion aid is selected from one or more of sesbania powder, cellulose, starch, polyethylene glycol, and polyvinyl alcohol;

preferably, the second oxide precursor comprises an inorganic salt of an alkaline earth metal; preferably, the alkaline earth metal is selected from one or more of calcium, magnesium, beryllium and strontium.

12. Use of a catalyst according to any one of claims 1 to 9 in an MTBE cleavage reaction.

Technical Field

The invention relates to the field of petrochemical industry, and in particular relates to a catalyst for preparing propylene by MTBE cracking, and a preparation method and application thereof.

Background

Methyl Tertiary Butyl Ether (MTBE) has been used for a long time for gasoline blending as a high octane gasoline additive. However, since methyl t-butyl ether remaining in the atmosphere and water causes environmental pollution, ethanol gasoline is being promoted in China as a substitute for MTBE gasoline. In the future, the use of methyl tertiary butyl ether will be increasingly remote from gasoline formulations.

At present, the scheme that the existing MTBE production device can be fully utilized and the high value-added product can be produced is that MTBE is cracked into isobutene again. Isobutene obtained by cracking MTBE can be used for producing products such as polyisobutylene, butyl rubber, tert-butylamine and the like, and can also be subjected to a polymerization reaction by an indirect alkylation technology to generate diisobutylene. The diisobutylene hydrogenation product isooctane has high octane value and can be used as a gasoline additive. Currently, some research organizations have developed indirect alkylation technology using MTBE device for transfer at home and abroad. Therefore, the preparation of isobutene by MTBE cracking is a current research hotspot, and many researchers develop cracking catalysts for the reaction process, such as: CN106890673A discloses a catalyst for preparing isobutene by cracking methyl tert-butyl ether and a preparation method thereof.

Compared with isobutene, propylene has wider application. In recent years, with the increasing demand of downstream products of propylene, the demand of propylene is increasing year by year, and technologies for increasing the yield of propylene are more concerned. If can be through one-step schizolysis of MTBE and prepare propylene, can solve the problem of going out of the way of current MTBE device, can produce the propylene of urgent need again. From the aspects of economic benefit and long-term development, the direct cracking of MTBE to prepare propylene is a better process route.

However, no studies have been reported on the production of propylene by MTBE cracking.

Disclosure of Invention

The invention aims to overcome the current situation that the use amount of methyl tert-butyl ether as a gasoline additive is gradually reduced in the prior art, provides a new utilization way for the methyl tert-butyl ether, and provides a catalyst for preparing propylene by MTBE cracking, a preparation method and application thereof.

In order to achieve the above object, a first aspect of the present invention provides an MTBE cracking propylene preparation catalyst, wherein the MTBE cracking propylene preparation catalyst comprises a SAPO-34 zeolite molecular sieve, a high specific surface area all-silicon mesoporous molecular sieve, a first oxide and a second oxide; wherein, based on the total weight of the catalyst, the content of the SAPO-34 zeolite molecular sieve is 35-65 wt%, the content of the high specific surface area all-silicon mesoporous molecular sieve is 15-45 wt%, the content of the first oxide is 8-25 wt%, and the content of the second oxide is 1-11 wt%.

In a second aspect, the present invention provides a method for preparing the aforementioned catalyst, wherein the method comprises:

(1) in the presence of dilute nitric acid, mixing an SAPO-34 zeolite molecular sieve, a high-specific surface area all-silicon mesoporous molecular sieve, an adhesive and an extrusion aid, then carrying out extrusion forming, drying and first roasting treatment to obtain a catalyst precursor;

(2) and (3) dipping the catalyst precursor into an aqueous solution containing a second oxide precursor, and carrying out second roasting treatment on the obtained solid product to obtain the catalyst for preparing the propylene by cracking the MTBE.

In a third aspect, the invention provides the use of the aforementioned catalyst in an MTBE cleavage reaction.

Through the technical scheme, the technical scheme provided by the invention has the following advantages:

(1) the catalyst for preparing propylene by cracking MTBE provided by the invention can be used for directly catalytically converting methyl tert-butyl ether to produce propylene, thereby solving the problem of surplus MTBE production and increasing the yield of important chemical raw material propylene.

(2) The catalyst for preparing propylene by cracking MTBE provided by the invention is used for the catalytic cracking reaction of methyl tert-butyl ether, the reaction process conditions are mild, and the selectivity of propylene and ethylene is high.

(3) The catalyst for preparing propylene by MTBE cracking provided by the invention has the advantages of easily available raw materials, simple preparation method process, easily controlled conditions and good product repeatability.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

FIG. 1 is the XRD spectrum of the high specific surface area all-silicon mesoporous molecular sieve A prepared in example 1.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The inventors of the present invention found that: in the prior art, no MTBE direct cracking process for producing propylene exists, and the invention aims to solve the problem. According to the knowledge of the physicochemical properties of the heterogeneous catalyst, the catalyst used for preparing propylene by cracking MTBE should have certain acidity and good hydrothermal stability. Based on the above requirements, zeolite molecular sieves having both a stable framework structure and a certain acidity are very suitable as the main component of catalysts for the production of propylene by the cleavage of MTBE. However, since the zeolite molecular sieve has a small pore size, the diffusion rate of the raw material molecules and the product molecules is affected during the reaction process, which in turn leads to the decrease of the catalyst performance. Compared with zeolite molecular sieve, the high specific surface area all-silicon mesoporous molecular sieve material has large pore canal size and pore volume, and is very suitable for catalytic reaction with macromolecules. However, the surface acidity of the all-silicon mesoporous molecular sieve material is extremely weak, and the all-silicon mesoporous molecular sieve material is not suitable for being used as a catalyst to catalyze MTBE cracking reaction alone. The inventor of the invention finds that if the SAPO-34 zeolite molecular sieve and the high-specific surface area all-silicon mesoporous molecular sieve are uniformly mixed and further modified to prepare the catalyst in the process of developing the MTBE cracking catalyst, the catalyst can be used for producing propylene by MTBE cracking reaction, and the content of propylene and ethylene in the product can be better increased.

The invention provides an MTBE cracking propylene preparation catalyst, wherein the MTBE cracking propylene preparation catalyst comprises a SAPO-34 zeolite molecular sieve, a high-specific surface area all-silicon mesoporous molecular sieve, a first oxide and a second oxide; wherein, based on the total weight of the catalyst, the content of the SAPO-34 zeolite molecular sieve is 35-65 wt%, the content of the high specific surface area all-silicon mesoporous molecular sieve is 15-45 wt%, the content of the first oxide is 8-25 wt%, and the content of the second oxide is 1-11 wt%.

In the present invention, when the MTBE cracking propylene preparation catalyst includes the SAPO-34 zeolite molecular sieve, the high specific surface area all-silicon mesoporous molecular sieve, the first oxide and the second oxide, the total content of the SAPO-34 zeolite molecular sieve, the high specific surface area all-silicon mesoporous molecular sieve, the first oxide and the second oxide is one hundred percent.

According to the present invention, it is preferable that the SAPO-34 zeolite molecular sieve is present in an amount of 45 to 60 wt%, the high specific surface area all-silicon mesoporous molecular sieve is present in an amount of 23 to 35 wt%, the first oxide is present in an amount of 14 to 17 wt%, and the second oxide is present in an amount of 2 to 6 wt%, based on the total weight of the catalyst.

In the present invention, the contents of the SAPO-34 zeolite molecular sieve, the high specific surface area all-silicon mesoporous molecular sieve, the first oxide and the second oxide are limited to the specific ranges described above, so that the contents of propylene and ethylene in the product can be preferably increased when the prepared catalyst is used in an MTBE cracking reaction.

According to the invention, the weight ratio of the SAPO-34 zeolite molecular sieve to the high-specific surface area all-silicon mesoporous molecular sieve is (0.7-4.3): 1, preferably (1-3.5): 1, more preferably (1.2-2.6): 1.

in the invention, the inventor considers that the SAPO-34 molecular sieve belongs to a zeolite molecular sieve, has a short-range ordered regular pore channel structure and better thermal stability, and simultaneously has a large number of acid centers distributed on the surface of the molecular sieve. Since the acid center is the active site of the cleavage reaction, the SAPO-34 molecular sieve may have some catalytic activity in the MTBE cleavage reaction. Our guess has also proven to be correct. In comparative example 1, a SAPO-34 molecular sieve was used as a main raw material to prepare a catalyst D1 through modification. Catalyst D1 gave a 19.1% yield of propylene and a 3.2% yield of ethylene in the MTBE cleavage reaction. SAPO-34 molecular sieve, while exhibiting good catalytic cracking performance, also has some drawbacks. Such as: the SAPO-34 molecular sieve has densely distributed acid centers on the surface, and the zeolite molecular sieve has smaller openings of pore channels, so that reaction intermediate products and final products cannot be smoothly diffused into a gas phase, the utilization efficiency of the acid centers is reduced, and side reactions are easy to occur. In view of the above, the present inventors have innovatively used a high specific surface area all-silicon mesoporous molecular sieve material in combination with a SAPO-34 molecular sieve to improve the structural defects of the zeolitic molecular sieve. On the first hand, the all-silicon molecular sieve has extremely weak surface acidity, and the all-silicon mesoporous molecular sieve with high specific surface area and the SAPO-34 molecular sieve with dense acid centers are uniformly mixed, so that the density of the acid centers can be reduced to a certain extent, and the catalytic efficiency of the acid centers is improved. In the second aspect, the high specific surface area mesoporous molecular sieve has pore channel size greater than that of zeolite molecular sieve and average pore size greater than 2 nm. After the mesoporous molecular sieve and the zeolite molecular sieve are mixed, the diffusion speed of reaction intermediates and products can be effectively improved, side reaction is avoided, and carbon deposition is inhibited. Therefore, the inventor of the invention finds that the combination of the SAPO-34 zeolite molecular sieve and the high-specific surface area all-silicon mesoporous molecular sieve can obviously improve the catalytic performance of the MTBE cracking catalyst. Furthermore, the SAPO-34 zeolite molecular sieve and the high-specific-surface-area all-silicon mesoporous molecular sieve are used in a matching way according to the specific proportion, so that the structural advantages of the two types of molecular sieves can be more effectively exerted.

In the invention, if the SAPO-34 zeolite molecular sieve is replaced by the ZRP zeolite molecular sieve, the performance of the ZRP molecular sieve catalyst in the MTBE cracking reaction can also be improved to a certain extent. However, the inventor considers that the surface of the SAPO molecular sieve has denser acid centers, and the use of the mesoporous molecular sieve with high specific surface area is more beneficial to improving the working efficiency of the acid centers. The distribution of the acid centers on the surface of the ZRP molecular sieve is not particularly dense, and the mesoporous molecular sieve with larger aperture size is mixed with the ZRP molecular sieve, so that the internal diffusion performance of the catalyst can be more effectively improved. Therefore, in the invention, the SAPO molecular sieve is used in combination with the all-silicon mesoporous molecular sieve with high specific surface area, so that the effect is better.

According to the invention, the specific surface area of the high-specific-surface-area all-silicon mesoporous molecular sieve is 800-²Per g, pore volume of 0.7-1.7cm³(ii)/g, average pore diameter is 2-4 nm; preferably, the specific surface area of the high specific surface area all-silicon mesoporous molecular sieve is 950-1300m²Per g, pore volume of 1.1-1.6cm³(ii)/g, the average pore diameter is 3-4 nm; more preferably, the specific surface area of the high specific surface area all-silicon mesoporous molecular sieve is 1147-1182m²Per g, pore volume of 1.3-1.4cm³(ii)/g, the average pore diameter is 3.2-3.5 nm. In the present invention, the reason for selecting the specific high specific surface area all-silicon mesoporous molecular sieve is that the acid centers on the surface of the SAPO-34 molecular sieve are distributed densely, and the use of the high specific surface area mesoporous molecular sieve can reduce the acid center density to a certain extent, which is more beneficial to improving the working efficiency of the acid centers and simultaneously achieves the effect of inhibiting side reactions.

According to the invention, the preparation method of the all-silicon mesoporous molecular sieve with high specific surface area comprises the following steps:

(S1) under the hydrolysis condition, mixing and contacting a template agent, ethyl orthosilicate and an ammonia water solution to obtain a mixture, and crystallizing, filtering, washing and drying the mixture to obtain high-specific surface area all-silicon mesoporous molecular sieve raw powder;

(S2) removing the template agent in the high specific surface area mesoporous material raw powder to obtain the high specific surface area all-silicon mesoporous molecular sieve.

According to the present invention, in the step (S1), there may be various cationic surfactants conventionally used in the art; preferably, the templating agent is cetyltrimethylammonium bromide.

According to the invention, the molar charge ratio of the ethyl orthosilicate, the template agent, the ammonia and the deionized water is 1: (0.1-1): (0.5-5): (50-500), preferably 1: (0.2-0.6): (1-4): (100-300).

In the present invention, the inventors of the present invention found that: and mixing the tetraethoxysilane, the template agent, the ammonia and the deionized water to obtain a mixture. The template agent is mainly used as a pore structure directing agent and can maintain the charge balance of a synthetic system; the ethyl orthosilicate has the function of providing mesoporous molecular sieve SiO₂The main elements of the framework are silicon and oxygen; the function of ammonia is to ensure that the synthesis process is carried out under alkaline conditions. The combined use of tetraethoxysilane, template solvent, ammonia and water is a necessary condition for synthesizing the high-specific surface area all-silicon mesoporous molecular sieve used in the invention.

According to the present invention, in step (S1), the conditions of the hydrolysis include: the temperature is 20-60 deg.C, and the time is 20-120 min; preferably, the temperature is 35-45 deg.C and the time is 30-50 min.

According to the present invention, in the step (S1), the crystallization conditions include: the temperature is 40-140 ℃, and the time is 5-120 h; preferably, the temperature is 90-110 ℃ and the time is 45-50 h.

According to the present invention, in the step (S1), the drying conditions include: the temperature is 70-140 ℃, and the time is 4-20 h; preferably, the temperature is 100-120 ℃, and the time is 10-15 h.

According to the present invention, in the step (S2), the removing conditions include: the temperature is 450-650 ℃, and the time is 4-30 h; preferably, the temperature is 500-550 ℃, and the time is 15-20 h.

According to the present invention, the first oxide is an oxide obtained by baking a binder; wherein the adhesive is selected from one or more of aluminum sol, pseudo-boehmite, aluminum hydroxide xerogel and silica sol; preferably, the first oxide is alumina and/or silica.

According to the invention, the second oxide is an alkaline earth oxide; preferably, the second oxide is selected from one or more of calcium oxide, magnesium oxide, beryllium oxide and strontium oxide. In the present invention, the specific second oxide selected from the present invention has the advantages of effectively improving the electron distribution on the surface of the catalyst, and adjusting the surface acidity strength of the molecular sieve, so that the molecular sieve is more favorable for the MTBE cracking reaction.

According to the invention, the specific surface area of the catalyst is 300-600m²Per g, pore volume of 0.4-0.8cm³(ii)/g; preferably, the specific surface area of the catalyst is 400-550m²Per g, pore volume of 0.45-0.65cm³(ii)/g; more preferably, the specific surface area of the catalyst is 457-²Per g, pore volume of 0.55-0.61cm³/g。

According to the invention, the catalyst may be in the shape of spheres, granules, bars, cylinders, etc.

In a second aspect, the present invention provides a method for preparing the aforementioned catalyst, wherein the method comprises:

(1) in the presence of dilute nitric acid, mixing an SAPO-34 zeolite molecular sieve, a high-specific surface area all-silicon mesoporous molecular sieve, an adhesive and an extrusion aid, then carrying out extrusion forming, drying and first roasting treatment to obtain a catalyst precursor;

(2) and (3) dipping the catalyst precursor into an aqueous solution containing a second oxide precursor, and carrying out second roasting treatment on the obtained solid product to obtain the catalyst for preparing the propylene by cracking the MTBE.

According to the invention, the extrusion aid is selected from one or more of sesbania powder, cellulose, starch, polyethylene glycol and polyvinyl alcohol; sesbania powder is preferred.

According to the invention, in the step (1), the SAPO-34 zeolite molecular sieve, the high specific surface area all-silicon mesoporous molecular sieve, the adhesive and the extrusion aid are uniformly mixed, diluted nitric acid is added, the mixture is uniformly stirred and then extruded and formed, and the mixture is dried at 70-150 ℃ for 4-20h and calcined at 500-600 ℃ for 3-20h to obtain the catalyst precursor.

According to the invention, in step (2), the second oxide precursor comprises an inorganic salt of an alkaline earth metal; preferably, the alkaline earth metal is selected from one or more of calcium, magnesium, beryllium and strontium.

According to the invention, in the step (2), the catalyst precursor obtained in the above step can be immersed in an aqueous solution containing a second oxide precursor, the solid product after water removal is dried at 70-150 ℃ for 3-30h, and calcined at 500-700 ℃ for 3-16h, so as to obtain the catalyst for preparing propylene by MTBE cracking.

In a third aspect, the invention provides the use of the aforementioned catalyst in an MTBE cleavage reaction.

According to the invention, the catalyst provided by the invention is used in the catalytic cracking process of the methyl tert-butyl ether, and the technological conditions of the catalytic cracking reaction of the methyl tert-butyl ether are as follows: the temperature is 400-^-1(ii) a Preferably: the temperature is 450 ℃ and the pressure is 0.02-2.0MPa, the mass space velocity of MTBE is 1-30h^-1。

The catalyst provided by the invention is used in the catalytic cracking process of methyl tert-butyl ether, and the reaction raw material can be pure methyl tert-butyl ether or a mixture of methyl tert-butyl ether and a diluent. Wherein the diluent may be C₄-C₈One or more of alkanes, preferably one or more of n-butane, isobutane, n-pentane, isopentane, n-hexane, n-heptane and n-octane; the molar ratio of the diluent to the methyl tert-butyl ether is 0.01-20: 1.

The present invention will be described in detail below by way of examples.

In the following examples and comparative examples:

the X-ray diffraction analysis of the samples was carried out on an X-ray diffractometer, model D8Advance, from Bruker AXS, Germany; the pore structure parameter analysis of the samples was performed on an adsorption apparatus model ASAP2020-M + C, available from Micromeritics, USA. Degassing in vacuum at 350 ℃ for 4h before sample measurement, calculating the specific surface area of the sample by adopting a BET method, and calculating the pore volume by adopting a BJH model; elemental analysis experiments on catalyst samples were performed on an Eagle III energy dispersive X-ray fluorescence spectrometer manufactured by EDAX, USA.

The drying box is produced by Shanghai-Hengchang scientific instruments Co., Ltd, and is of a type DHG-9030A.

The muffle furnace is manufactured by CARBOLITE corporation, model CWF 1100.

The SAPO-34 molecular sieve powders used in the examples and comparative examples were obtained from Beijing Ke Xin Zi Tech Co., Ltd; the alumina sol and the silica sol are purchased from Zibo Jiarun chemical Co., Ltd; pseudoboehmite was purchased from Zibo Hengqi new materials Co.

Other reagents used in examples and comparative examples were purchased from national pharmaceutical group chemical agents, ltd, and the purity of the reagents was analytical grade.

Example 1

This example illustrates a catalyst for cracking MTBE to produce propylene, which is prepared by the method of the present invention.

(1) Preparation of high specific surface area full silicon mesoporous molecular sieve

25.5g (0.07mL) of cetyltrimethylammonium bromide as a template, 0.5mL of 25 wt% ammonia water and 488g of deionized water were mixed and stirred at 40 ℃ for 20min, 41.6g (0.2mL) of ethyl orthosilicate was slowly added to the mixture, and stirring was continued for 40 min. Transferring the mixture into a hydrothermal reaction kettle with a polytetrafluoroethylene lining, crystallizing at 100 ℃ for 48 hours, separating a solid product from a mother solution by using a filtering method, washing for 5 times by using deionized water, and drying at 110 ℃ for 12 hours after suction filtration to obtain high-specific surface area all-silicon mesoporous molecular sieve raw powder; and roasting the raw powder of the all-silicon mesoporous molecular sieve with the high specific surface area for 16 hours at 500 ℃ in flowing air to obtain the all-silicon mesoporous molecular sieve A with the high specific surface area.

The high specific surface area all-silicon mesoporous molecular sieve A is characterized by using an ASAP2020-M + C type adsorption apparatus, and various process parameters and structure parameters of the high specific surface area all-silicon mesoporous molecular sieve in the preparation process of the high specific surface area all-silicon mesoporous molecular sieve are listed in Table 1.

FIG. 1 is an XRD spectrum of an all-silicon mesoporous molecular sieve A with high specific surface area prepared in example 1 of the invention. As can be seen from fig. 1: three clearly visible diffraction spectrum peaks appear at a small angle below 5 degrees, and the material is proved to have a typical two-dimensional hexagonal mesoporous structure.

(2) Preparation of catalyst for preparing propylene by MTBE cracking

Uniformly mixing 100g of SAPO-34 molecular sieve, 60g of high-specific-surface-area all-silicon mesoporous molecular sieve, 48g of pseudo-boehmite with the water content of 33 wt% and 10g of sesbania powder, adding 90mL of nitric acid with the concentration of 5 wt%, uniformly stirring, extruding and cutting into cylinders with the diameter of 2mm and the length of 2-3 mm; drying at 110 ℃ for 10h and finally calcining at 570 ℃ for 6h to obtain the catalyst precursor A. 96g of the catalyst precursor A was taken and impregnated with 100mL of an aqueous solution in which 14.7g of magnesium nitrate was dissolved, and after removing water, the solid product was dried at 120 ℃ for 15 hours and calcined at 550 ℃ for 8 hours to obtain the MTBE cleavage propylene preparation catalyst A.

The specific surface area, pore volume and composition of catalyst a are shown in table 2 and calculated as: the weight ratio of the SAPO-34 zeolite molecular sieve to the high-specific surface area all-silicon mesoporous molecular sieve is 1.67.

Examples 2 to 3

This example illustrates a catalyst for cracking MTBE to produce propylene, which is prepared by the method of the present invention.

Catalysts B and C were prepared under the same conditions as in example 1, except that: by changing various parameters in the preparation process of the high specific surface area all-silicon mesoporous molecular sieve and the preparation process of the catalyst for preparing propylene by MTBE cracking in the example 1, the high specific surface area all-silicon mesoporous molecular sieves B and C and the catalysts B and C are respectively obtained by carrying out the examples 2 and 3.

Table 1 lists the process parameters and the structural parameters of the all-silicon mesoporous molecular sieve with high specific surface area in the preparation process of the all-silicon mesoporous molecular sieve with high specific surface area.

The specific surface areas, pore volumes and composition of catalysts B and C are shown in table 2 and calculated as: the weight ratio of the SAPO-34 zeolite molecular sieve to the high specific surface area all-silicon mesoporous molecular sieve in example 2 is 2.2, and the weight ratio of the SAPO-34 zeolite molecular sieve to the high specific surface area all-silicon mesoporous molecular sieve in example 3 is 1.2857.

Example 4

This example illustrates a catalyst for cracking MTBE to produce propylene, which is prepared by the method of the present invention.

Catalyst D was prepared under the same conditions as in example 1, except that: the high specific surface area all-silicon mesoporous molecular sieve D is used for replacing the high specific surface area all-silicon mesoporous molecular sieve A, and table 1 lists various process parameters and structural parameters of the high specific surface area all-silicon mesoporous molecular sieve in the preparation process of the high specific surface area all-silicon mesoporous molecular sieve.

The specific surface area, pore volume and composition of catalyst D are shown in table 2 and calculated as: the weight ratio of the SAPO-34 zeolite molecular sieve to the high-specific surface area all-silicon mesoporous molecular sieve is 1.67.

Example 5

This example illustrates a catalyst for cracking MTBE to produce propylene, which is prepared by the method of the present invention.

Catalyst E was prepared under the same conditions as in example 1, except that: based on the total weight of the catalyst E, the catalyst comprises the following components: 60 wt% of SAPO-34 molecular sieve, 23 wt% of high specific surface area all-silicon mesoporous molecular sieve A, 15 wt% of alumina from adhesive and 2 wt% of calcium oxide.

The specific surface area, pore volume and composition of catalyst E are shown in table 2 and calculated as: the weight ratio of the SAPO-34 zeolite molecular sieve to the high-specific surface area all-silicon mesoporous molecular sieve is 2.6087.

Example 6

This example illustrates a catalyst for cracking MTBE to produce propylene, which is prepared by the method of the present invention.

Catalyst F was prepared under the same conditions as in example 1, except that: based on the total weight of the catalyst F, the catalyst F comprises the following components: 65 wt% of SAPO-34 molecular sieve, 15 wt% of high specific surface area all-silicon mesoporous molecular sieve A, 9 wt% of alumina from adhesive and 11 wt% of calcium oxide.

The specific surface area, pore volume and composition of catalyst F are shown in table 2 and calculated as: the weight ratio of the SAPO-34 zeolite molecular sieve to the high-specific surface area all-silicon mesoporous molecular sieve is 4.33.

Example 7

This example illustrates a catalyst for cracking MTBE to produce propylene, which is prepared by the method of the present invention.

Catalyst G was prepared under the same conditions as in example 1, except that: based on the total weight of the catalyst G, the catalyst G comprises the following components: 35 wt% of SAPO-34 molecular sieve, 45 wt% of high specific surface area all-silicon mesoporous molecular sieve A, 19 wt% of alumina from adhesive and 1 wt% of calcium oxide.

The specific surface area, pore volume and composition of catalyst G are shown in table 2 and calculated as: the weight ratio of the SAPO-34 zeolite molecular sieve to the high-specific surface area all-silicon mesoporous molecular sieve is 0.78.

Comparative example 1

Catalyst D1 was prepared under the same conditions as in example 1, except that: and (3) eliminating the step (1), only reserving the step (2), not using the high-specific surface area all-silicon mesoporous molecular sieve A, and replacing 100g of SAPO-34 molecular sieve with 160g of SAPO-34 molecular sieve.

Comparative example 2

Catalyst D2 was prepared under the same conditions as in example 1, except that: 60g of high-specific-surface-area all-silicon mesoporous molecular sieve A is replaced by 160g of high-specific-surface-area all-silicon mesoporous molecular sieve A without using SAPO-34 molecular sieve.

Comparative example 3

Catalyst D3 was prepared under the same conditions as in example 1, except that: based on the total weight of the catalyst D3, the catalyst comprises: 73 wt% of SAPO-34 molecular sieve, 8 wt% of high specific surface area all-silicon mesoporous molecular sieve A, 7 wt% of alumina from adhesive and 12 wt% of calcium oxide.

Test example 1

Taking a fixed bed reactor as an example, the performance evaluation result of the MTBE cracking propylene preparation catalyst provided by the invention in the methyl tert-butyl ether catalytic cracking reaction is illustrated.

Respectively filling 5.0g of catalyst A, catalyst B, catalyst C, catalyst D, catalyst E, catalyst D1, catalyst D2 and catalyst D3 into a stainless steel reactor, wherein the reaction temperature is 500 ℃, the reaction pressure is 0.05MPa, the reaction raw material is pure methyl tert-butyl ether, and the weight space velocity of the raw material is 18h^-1Reaction time is 150 hours, after product cooling and gas-liquid separation, gas composition is prepared by Al₂O₃-agilent 6890 gas chromatograph analysis of S capillary chromatography column and hydrogen flame detector (FID), using programmed temperature, quantitative analysis with correction factors; the liquid composition was analyzed by an agilent 6890 gas chromatograph equipped with a PONA chromatographic column. The performance evaluation results of the MTBE cracking propylene preparation catalyst provided by the invention in the methyl tert-butyl ether catalytic cracking reaction are shown in Table 3.

TABLE 1

TABLE 2

TABLE 3

As can be seen from Table 3, MTBE was converted completely under the conditions of the process for producing propylene by catalytic cracking of MTBE selected in the test examples, regardless of whether the catalysts of examples or comparative examples were used. However, the catalyst for preparing propylene by MTBE cracking provided by the invention has excellent performance when used for preparing propylene by methyl tert-butyl ether catalytic cracking.

Comparing the data of catalyst a and catalyst D1, it can be seen that the high specific surface area all-silicon mesoporous molecular sieve was added to catalyst a, and the high specific surface area all-silicon mesoporous molecular sieve was not added to catalyst D1. Compared with catalyst D1, the ethylene selectivity and the propylene selectivity of catalyst A are both improved significantly.

Comparing the data of catalyst A and catalyst D2, it can be seen that the SAPO-34 molecular sieve and the high specific surface area all-silicon mesoporous molecular sieve are used simultaneously in catalyst A, and only the high specific surface area all-silicon mesoporous molecular sieve and no SAPO-34 molecular sieve are used in catalyst D2. The ethylene selectivity and propylene selectivity of catalyst D2 were both very low.

Comparing the data of catalyst a and catalyst D3, it can be seen that, in the component of catalyst D3, the weight ratio 9.125 of the SAPO-34 zeolite molecular sieve to the high specific surface area all-silicon mesoporous molecular sieve is higher than that of the zeolite molecular sieve and the high specific surface area all-silicon mesoporous molecular sieve, which is not in the scope of the claims of the present invention, and the channel advantages of the mesoporous material are difficult to be effectively exerted; in addition, the catalyst D3 has a high content of modifying components and is outside the scope of the claims. Thus, catalyst D3 exhibited significantly lower catalytic performance in the MTBE cleavage reaction than catalyst A.

Comparing catalyst a with catalyst E and catalyst F, the specific surface area and pore volume of the zeolitic molecular sieve are relatively small, while the specific surface area and pore volume of the mesoporous molecular sieve are relatively large. Therefore, if the zeolite molecular sieve content is high in the catalyst, the specific surface area and pore volume of the catalyst are small; in comparison with catalyst A and catalyst G, if the content of the mesoporous molecular sieve is high, the specific surface area and pore volume of the catalyst become large. The catalyst with the best reactivity is zeolite and has a mesoporous content within a certain range, so that the specific surface area and pore volume of the catalyst are also the best within a certain range, and the larger the catalyst, the better the catalyst, and the smaller the catalyst, the better the catalyst.

The results show that the catalyst for preparing propylene by MTBE cracking provided by the invention has excellent performance because the catalyst simultaneously contains the SAPO-34 zeolite molecular sieve and the high-specific-surface-area all-silicon mesoporous molecular sieve and specific mixture ratio of the SAPO-34 zeolite molecular sieve and the high-specific-surface-area all-silicon mesoporous molecular sieve, and also contains specific contents of the SAPO-34 zeolite molecular sieve, the first oxide and the second oxide of the high-specific-surface-area all-silicon mesoporous molecular sieve.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.