Catalyst for preparing propylene by converting methyl tert-butyl ether and preparation method and application thereof
阅读说明：本技术 用于甲基叔丁基醚转化制丙烯的催化剂及其制备方法和应用 (Catalyst for preparing propylene by converting methyl tert-butyl ether and preparation method and application thereof ) 是由 王定博 刘红梅 亢宇 于 2020-05-25 设计创作，主要内容包括：本发明涉及石油化工领域,公开了一种用于甲基叔丁基醚转化制丙烯的催化剂及其制备方法和应用。所述催化剂包括ZRP-5沸石分子筛、KIT-6介孔分子筛、氧化铝和改性氧化物；其中,以所述甲基叔丁基醚转化制丙烯催化剂的总重量为基准,所述ZRP-5沸石分子筛的含量为40-70重量％,所述KIT-6介孔分子筛的含量为15-35重量％,所述氧化铝的含量为5-25重量％,所述改性氧化物的含量为1-9重量％。该催化剂既解决了MTBE生产过剩的问题,又增产了重要的化工原料丙烯。(The invention relates to the field of petrochemical industry, and discloses a catalyst for preparing propylene by converting methyl tert-butyl ether, and a preparation method and application thereof. The catalyst comprises a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, alumina and a modified oxide; wherein, based on the total weight of the catalyst for preparing propylene by converting methyl tert-butyl ether, the content of the ZRP-5 zeolite molecular sieve is 40-70 wt%, the content of the KIT-6 mesoporous molecular sieve is 15-35 wt%, the content of the alumina is 5-25 wt%, and the content of the modified oxide is 1-9 wt%. The catalyst not only solves the problem of excessive production of MTBE, but also increases the yield of the important chemical raw material propylene.)
1. The catalyst for converting methyl tert-butyl ether to propylene is characterized by comprising a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, alumina and a modified oxide; wherein, based on the total weight of the catalyst, the content of the ZRP-5 zeolite molecular sieve is 40-70 wt%, the content of the KIT-6 mesoporous molecular sieve is 15-35 wt%, the content of the alumina is 5-25 wt%, and the content of the modified oxide is 1-9 wt%.
2. The catalyst of claim 1, wherein the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the KIT-6 mesoporous molecular sieve is (1.1-4.7): 1, preferably (1.5-4): 1, more preferably (2.1-3.3): 1.
3. the catalyst of claim 1 or 2, wherein KIT-6 is a mediatorThe average pore diameter of the molecular sieve is 4-10nm, the specific surface area is 600-800m2Per g, pore volume of 0.7-1.5cm3/g；
Preferably, the KIT-6 mesoporous molecular sieve has an average pore diameter of 6.5-8.5nm and a specific surface area of 650-780m2Per g, pore volume of 1.2-1.4cm3/g。
4. The catalyst of any of claims 1-3, wherein the KIT-6 mesoporous molecular sieve is prepared by a method comprising:
(S1) under the condition of hydrolysis gel making, mixing a template solvent, a silicon source, n-butanol and hydrochloric acid to obtain a gel mixture;
(S2) sequentially crystallizing, filtering, washing, drying and roasting the gel mixture to obtain the KIT-6 mesoporous molecular sieve.
5. The catalyst according to claim 4, wherein, in step (S1), the template agent is a nonionic surfactant;
preferably, the silicon source is a silicon-containing organic compound and/or a silicon-containing inorganic compound;
preferably, the molar ratio of the template agent, the silicon source, n-butanol, hydrochloric acid and water is 1: (10-150): (20-200): (200-1200): (5000-; preferably 1: (30-100): (50-120): (500-900): (8000- > 13500);
preferably, the conditions for preparing the glue by hydrolysis comprise: the temperature is 20-50 deg.C, and the time is 5-30 h.
6. The catalyst of claim 4, wherein, in the step (S2), the crystallization conditions include: the temperature is 80-120 ℃, and the time is 10-40 h;
preferably, the conditions of the calcination include: the temperature is 400 ℃ and 600 ℃, and the time is 8-60 h.
7. The catalyst according to any one of claims 1 to 6, wherein the alumina is an oxide obtained by calcining a binder; the adhesive is selected from one or more of aluminum sol, pseudo-boehmite and aluminum hydroxide xerogel.
8. The catalyst of any one of claims 1-7, wherein the modifying oxide is an alkaline earth metal oxide; preferably, the modified oxide is selected from one or more of beryllium oxide, calcium oxide, magnesium 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 250-500m2Per g, pore volume of 0.35-0.7cm3/g；
Preferably, the specific surface area of the catalyst is 300-400m2Per g, pore volume of 0.4-0.6cm3/g。
10. A method for preparing a catalyst according to any one of claims 1 to 9, comprising:
(1) mixing a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, an adhesive and an extrusion aid in the presence of dilute nitric acid, 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 modified oxide precursor, and carrying out second roasting treatment on the obtained solid product to obtain the catalyst for preparing propylene by converting methyl tert-butyl ether.
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 modified oxide precursor comprises an inorganic salt of an alkaline earth metal; preferably, the alkaline earth metal is selected from one or more of beryllium, calcium, magnesium and strontium.
12. Use of a catalyst according to any one of claims 1 to 9 in the catalytic cracking reaction of methyl tert-butyl ether.
Technical Field
The invention relates to the field of petrochemical industry, in particular to a catalyst for preparing propylene by converting methyl tert-butyl ether, and a preparation method and application thereof.
Background
Methyl Tertiary Butyl Ether (MTBE) has been used for a long time in gasoline blending as a high octane gasoline additive. However, since methyl t-butyl ether remaining in the atmosphere and water causes environmental pollution, the future and fate of industrial facilities for producing MTBE have attracted extensive attention from domestic enterprises and research institutions in view of the above-mentioned reasons, and it is urgent to find new industrial uses for MTBE.
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: CN108409517A discloses a method for preparing isobutene by catalytic cracking of methyl tert-butyl ether.
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 dosage of methyl tert-butyl ether used as a gasoline additive is gradually reduced in the prior art, provides a new utilization way for the methyl tert-butyl ether, provides a catalyst for preparing propylene by converting the methyl tert-butyl ether, a preparation method and application thereof, solves the problem of over production of MTBE, increases the yield of important chemical raw material propylene, and can better improve the content of propylene and ethylene in the product by applying the catalyst provided by the invention to the catalytic cracking reaction of the methyl tert-butyl ether.
In order to achieve the above object, the present invention provides in a first aspect a catalyst for the conversion of methyl tert-butyl ether to propylene, characterized in that the catalyst comprises a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, alumina and a modified oxide; wherein, based on the total weight of the catalyst for preparing propylene by converting methyl tert-butyl ether, the content of the ZRP-5 zeolite molecular sieve is 40-70 wt%, the content of the KIT-6 mesoporous molecular sieve is 15-35 wt%, the content of the alumina is 5-25 wt%, and the content of the modified oxide is 1-9 wt%.
In a second aspect, the present invention provides a method for preparing the aforementioned catalyst, wherein the method comprises:
(1) mixing a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, an adhesive and an extrusion aid in the presence of dilute nitric acid, 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 modified oxide precursor, and carrying out second roasting treatment on the obtained solid product to obtain the catalyst for preparing propylene by converting methyl tert-butyl ether.
The third aspect of the invention provides an application of the catalyst in the catalytic cracking reaction of the methyl tert-butyl ether.
Through the technical scheme, the technical scheme provided by the invention has the following advantages:
(1) the catalyst for preparing propylene by converting methyl tert-butyl ether provided by the invention can be used for directly catalytically converting methyl tert-butyl ether to produce propylene, so that the problem of over production of MTBE is solved, and the production of important chemical raw material propylene is increased.
(2) The catalyst for preparing propylene by converting methyl tert-butyl ether provided by the invention is used in the catalytic cracking reaction of methyl tert-butyl ether, and has the advantages of mild reaction process conditions and high selectivity of propylene and ethylene.
(3) The catalyst for preparing propylene by converting methyl tert-butyl ether provided by the invention has the advantages of easily obtained preparation 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 an XRD spectrum of KIT-6 mesoporous molecular sieve A prepared in example 1 of the present invention;
FIG. 2 is a TEM transmission electron micrograph of a KIT-6 mesoporous molecular sieve A prepared in example 1 of the present invention;
FIG. 3 is a graph of the pore size distribution of the KIT-6 mesoporous molecular sieve A prepared in example 1 of the present invention.
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 sieves, KIT-6 mesoporous molecular sieve materials have large pore canal size and pore volume, and are very suitable for catalytic reactions 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 ZRP-5 zeolite molecular sieve and the KIT-6 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 improved.
The invention provides a catalyst for converting methyl tert-butyl ether to propylene, wherein the catalyst comprises a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, alumina and a modified oxide; wherein, based on the total weight of the catalyst, the content of the ZRP-5 zeolite molecular sieve is 40-70 wt%, the content of the KIT-6 mesoporous molecular sieve is 15-35 wt%, the content of the alumina is 5-25 wt%, and the content of the modified oxide is 1-9 wt%.
In the present invention, it should be noted that, when the catalyst includes a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, alumina, and a modified oxide, the total content of the ZRP-5 zeolite molecular sieve, the KIT-6 mesoporous molecular sieve, the alumina, and the modified oxide is one hundred percent.
According to the invention, preferably, the content of the ZRP-5 zeolite molecular sieve is 52-62 wt%, the content of the KIT-6 mesoporous molecular sieve is 19-28 wt%, the content of the alumina is 10-19 wt%, and the content of the modified oxide is 3-8 wt%, based on the total weight of the catalyst.
In the invention, the contents of the ZRP-5 zeolite molecular sieve, the KIT-6 mesoporous molecular sieve, the alumina and the modified oxide are limited to be in the specific ranges, so that the prepared catalyst can be used for the catalytic cracking reaction of the methyl tert-butyl ether, and the contents of propylene and ethylene in the product can be better improved.
According to the invention, the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the content of the KIT-6 mesoporous molecular sieve is (1.1-4.7): 1, preferably (1.5-4): 1, more preferably (2.1-3.3): 1.
in the invention, the inventor finds that the catalytic material with the acid center has better catalytic effect on the MTBE cracking reaction according to the basic characteristics of the cracking reaction. The experimental results further demonstrate that this finding is correct. It was indeed possible to effectively convert MTBE and produce ethylene and propylene using a ZRP-5 zeolite molecular sieve containing surface acid centers as the catalyst (comparative example D1 for catalyst, see Table 3 for test results). On the basis, it is explained that ZRP-5 belongs to the category of zeolite molecular sieves, and although it has a regular pore structure, a suitable acid center and a good hydrothermal stability, because the pore opening size is small (the pore diameter is less than 0.6nm), it is not favorable for the diffusion of reaction raw material molecules and product molecules during the reaction process, and further causes the occurrence of side reactions and the deposition of carbon deposition, thereby reducing the selectivity of the target product and the stability of the catalyst. In order to make up for the structural defects of the ZRP-5 molecular sieve, the inventor creatively uses a mesoporous material doping method to improve the catalytic performance of the acidic zeolite molecular sieve in the MTBE cracking reaction. In the invention, the inventor selects and mixes the all-silicon mesoporous molecular sieve KIT-6 with the ZRP-5 molecular sieve to make up the weakness of narrow pore channels of the zeolite molecular sieve. KIT-6 all-silicon mesoporous molecular sieve has no acid center on the surface, so that the KIT-6 all-silicon mesoporous molecular sieve cannot be used as a cracking reaction catalyst alone. But the specific surface area of the material is larger (724 m)2(g) and large pore size (the average pore diameter is 6-10nm which is more than 10 times of the pore diameter of the ZRP-5 molecular sieve). If the advantages of the channel structure of the KIT-6 full-silicon mesoporous molecular sieve can be utilized in the reaction process to improve the reaction on the surface of the ZRP-5 molecular sieveThe diffusion effect of the substance molecules and the product molecules can obviously improve the selectivity of propylene and ethylene and inhibit the generation of carbon deposition. Therefore, in the invention, the ZRP-5 zeolite molecular sieve and the KIT-6 mesoporous molecular sieve are mixed, molded and modified to prepare the catalyst, and the catalyst is applied to the reaction of preparing propylene and ethylene by cracking MTBE. Furthermore, the ZRP-5 zeolite molecular sieve and the KIT-6 mesoporous molecular sieve are matched and used according to the specific proportion, so that the characteristic of complementary structure advantages of the ZRP-5 molecular sieve and the KIT-6 full-silicon mesoporous molecular sieve can be more effectively exerted.
According to the invention, the KIT-6 mesoporous molecular sieve has an average pore diameter of 4-10nm and a specific surface area of 600-800m2Per g, pore volume of 0.7-1.5cm3(ii)/g; preferably, the KIT-6 mesoporous molecular sieve has an average pore diameter of 6.5-8.5nm and a specific surface area of 650-780m2Per g, pore volume of 1.2-1.4cm3(ii)/g; more preferably, the KIT-6 mesoporous molecular sieve has an average pore diameter of 7.2-8.2nm and a specific surface area of 694-751m2Per g, pore volume of 1.2-1.4cm3(ii) in terms of/g. In the present invention, the main reason for selecting the specific KIT-6 mesoporous molecular sieve is that the pore size of the molecular sieve is much larger than that of the ZRP-5 molecular sieve, and the average pore diameter can be 6nm or more. The structure is particularly beneficial to the diffusion of raw materials and products in the reaction, the reaction efficiency can be greatly improved, and the occurrence of side reactions is reduced.
According to the invention, the preparation method of the KIT-6 mesoporous molecular sieve comprises the following steps:
(S1) under the condition of hydrolysis gel making, mixing a template solvent, a silicon source, n-butanol and hydrochloric acid to obtain a gel mixture;
(S2) sequentially crystallizing, filtering, washing, drying and roasting the gel mixture to obtain the KIT-6 mesoporous molecular sieve.
According to the present invention, in the step (S1), there may be various nonionic surfactants conventionally used in the art; in the present invention, preferably, the template is a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer; more preferably, the templating agent is P123 (formula EO)20PO70EO20)。
According to the present invention, the silicon source may be a silicon-containing organic compound and/or a silicon-containing inorganic compound; in the present invention, preferably, the silicon source is selected from one or more of ethyl orthosilicate, methyl orthosilicate and butyl orthosilicate; more preferably, the silicon source is tetraethoxysilane.
According to the invention, the molar ratio of the template agent, the silicon source, n-butanol, hydrochloric acid and water is 1: (10-150): (20-200): (200-1200): (5000-; preferably 1: (30-100): (50-120): (500-900): (8000-13500).
In the present invention, the inventors of the present invention found that: mixing the template solvent, a silicon source, n-butanol and hydrochloric acid to obtain a gel mixture. The template agent is used for forming a directing agent of a specific pore channel structure, the silicon source is used for providing necessary elements for the basic framework structure of the mesoporous molecular sieve, the n-butanol is used for assisting the formation of the mesoporous structure, and the hydrochloric acid is used for enabling the synthesis reaction to be carried out under an acidic condition. The combination of the template solvent, the silicon source, the n-butanol and the hydrochloric acid is a necessary condition for synthesizing the required KIT-6 mesoporous molecular sieve.
According to the present invention, in the step (S1), the conditions for hydrolysis gum making include: the temperature is 20-50 ℃ and the time is 5-30 h; preferably, the temperature is 30-40 ℃ and the time is 20-24 h.
According to the invention, in the preparation method of the KIT-6 mesoporous molecular sieve, in the step (S2), the crystallization conditions include: the temperature is 80-120 ℃, and the time is 10-40 h; preferably, the temperature is 90-110 ℃ and the time is 20-30 h.
According to the present invention, the washing conditions in the preparation method of KIT-6 mesoporous molecular sieve in the step (S2) are not particularly limited, and for example, the washing process may include: after filtration, a solid product is obtained, which is repeatedly washed with distilled water (the number of washing times may be 2 to 10), and then subjected to suction filtration.
According to the present invention, in the preparation method of KIT-6 mesoporous molecular sieve, in the step (S2), the drying conditions include: the temperature is 70-140 ℃ and the time is 4-20 h.
According to the present invention, in the step (S2), the firing conditions include: the temperature is 400 ℃ and 600 ℃, and the time is 8-60 h; preferably, the temperature is 450 ℃ and 550 ℃, and the time is 20-30 h.
According to the present invention, in step (S2), the catalyst precursor is immersed in an aqueous solution containing a modified oxide precursor, and water is removed to obtain a solid product. The method for removing water is not particularly limited, and may be a method known in the art, for example: evaporation is carried out using a rotary evaporator or by heating during stirring.
According to the invention, the alumina is an oxide obtained by roasting a binder; the adhesive is selected from one or more of aluminum sol, pseudo-boehmite and aluminum hydroxide xerogel.
According to the invention, the modified oxide is an alkaline earth metal oxide; preferably, the modified oxide is selected from one or more of beryllium oxide, calcium oxide, magnesium oxide and strontium oxide. In the present invention, the particular modified oxide selected from the present invention has the advantage of improving the electron distribution on the surface of the molecular sieve and selectively covering too strong acid sites, making the surface characteristics of the catalyst more suitable for the MTBE cleavage reaction to proceed.
According to the invention, the specific surface area of the catalyst is 250-500m2Per g, pore volume of 0.35-0.7cm3(ii)/g; preferably, the specific surface area of the catalyst is 300-400m2Per g, pore volume of 0.4-0.6cm3(ii)/g; more preferably, the specific surface area of the catalyst is 327-362m2Per g, pore volume of 0.44-0.53cm3/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) mixing a ZRP-5 zeolite molecular sieve, a KIT-6 mesoporous molecular sieve, an adhesive and an extrusion aid in the presence of dilute nitric acid, 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 modified oxide precursor, and carrying out second roasting treatment on the obtained solid product to obtain the catalyst for preparing propylene by converting methyl tert-butyl ether.
According to the invention, in the step (1), 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 ZRP-5 zeolite molecular sieve, the KIT-6 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 the temperature of 70-150 ℃ for 2-20h and is subjected to first roasting at the temperature of 500-600 ℃ for 6-20h to obtain the catalyst precursor.
According to the present invention, in the step (2), the modified oxide precursor includes an inorganic salt of an alkaline earth metal; preferably, the alkaline earth metal is selected from one or more of beryllium, calcium, magnesium and strontium.
According to the invention, in the step (2), the catalyst precursor can be immersed in an aqueous solution containing a modified oxide precursor, the solid product after moisture removal is dried at 70-150 ℃ for 3-30h, and the second roasting at 500-700 ℃ for 3-16h, so as to obtain the catalyst for converting methyl tert-butyl ether to propylene.
The third aspect of the invention provides an application of the catalyst in the catalytic cracking reaction of the methyl tert-butyl ether.
The catalyst provided by the invention is used in the catalytic cracking process of methyl tert-butyl ether, and the catalytic cracking reaction process conditions of the methyl tert-butyl ether are as follows: the temperature can be 400-700 ℃, preferably 450-600 ℃; the pressure may be 0.01-5.0MPa, preferably 0.02-1.0 MPa; the mass space velocity of the methyl tert-butyl ether can be 0.1-50h-1Preferably 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 kinds of alkanesPreferably 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 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; the high-resolution transmission electron microscope picture of the sample is obtained on a Tecnai F20 type high-resolution transmission electron microscope produced by FEIPhilips, the Netherlands; 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 polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123) used in the examples and comparative examples was purchased from Sigma-Aldrich Chemistry; the ZRP-5 zeolite molecular sieve is purchased from Kyowa Biochemical manufacturing Co., Ltd; alumina sol was 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 is intended to illustrate a catalyst for the conversion of methyl t-butyl ether to propylene, prepared by the process of the present invention.
(1) Preparation of KIT-6 mesoporous molecular sieve
Dissolving 11.6g of triblock copolymer surfactant P123 in 411g of 3.9M hydrochloric acid solution at the temperature of 35 ℃, and stirring for 4 hours till the P123 is completely dissolved to form a transparent solution; adding 11.8g of n-butanol into the solution and continuing stirring for 1 hour; then, 25g of ethyl orthosilicate was slowly added dropwise to the solution, and stirred at 35 ℃ for 24 hours to obtain a gel mixture. And transferring the gel mixture to a hydrothermal reaction kettle, and crystallizing for 24 hours at 100 ℃. And repeatedly washing and filtering the crystallized product by using deionized water to obtain a KIT-6 mesoporous material filter cake. Drying the KIT-6 mesoporous material filter cake at 100 ℃ for 12h, and calcining at 500 ℃ for 24h to remove the template agent to obtain the KIT-6 mesoporous molecular sieve A.
The structural parameters of the KIT-6 mesoporous molecular sieve A are listed in Table 1.
FIG. 1 is an XRD spectrum of KIT-6 mesoporous molecular sieve A. As can be seen from fig. 1: according to a small-angle spectrum peak appearing in an XRD spectrogram, the KIT-6 mesoporous molecular sieve A has a typical three-dimensional cubic mesoporous structure.
FIG. 2 is a TEM transmission electron micrograph of KIT-6 mesoporous molecular sieve A. As can be seen from fig. 2: the channels of the KIT-6 mesoporous molecular sieve A are communicated with each other, and the aperture is between 7 and 9 nm.
FIG. 3 is a graph of the pore size distribution of KIT-6 mesoporous molecular sieve A. As can be seen from fig. 3: the material has uniform pore size distribution, and the most probable pore size is about 8 nm.
(2) Preparation of catalyst for cracking methyl tert-butyl ether to prepare propylene
Uniformly mixing 110g of ZRP-5 zeolite molecular sieve, 50g of KIT-6 mesoporous molecular sieve A, 48g of pseudo-boehmite with the water content of 33% and 10g of sesbania powder, adding 90ml of 5% nitric acid, stirring uniformly, extruding and cutting into cylinders with the diameter of 2mm and the length of 2-3 mm; drying at 110 ℃ for 8h and finally calcining at 560 ℃ for 7h gave catalyst precursor A. 96g of the catalyst precursor A was taken out and impregnated with 100ml of an aqueous solution in which 11.7g of calcium nitrate was dissolved, and after removing water, the solid product was dried at 120 ℃ for 15 hours and then calcined at 550 ℃ for 8 hours to obtain a catalyst A for propylene production by cracking of methyl t-butyl ether.
The specific surface area, pore volume and composition of catalyst a are listed in table 2; and by calculating: the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the content of the KIT-6 mesoporous molecular sieve is 2.2.
Examples 2 to 3
Examples 2-3 are directed to illustrating the catalyst prepared by the process of the present invention for the conversion of methyl t-butyl ether to propylene.
A catalyst was prepared under the same conditions as in example 1, except that: by changing various parameters in the preparation process of the KIT-6 mesoporous molecular sieve and the preparation process of the catalyst for preparing propylene by cracking methyl tert-butyl ether in the example 1, the KIT-6 mesoporous molecular sieves B and C and the catalysts B and C are respectively obtained by carrying out the example 2 and the example 3.
Table 1 lists various process parameters and structural parameters of the KIT-6 mesoporous molecular sieve in the preparation process of the KIT-6 mesoporous molecular sieve.
The specific surface areas, pore volumes and compositions of catalysts B and C are shown in table 2; and by calculating: the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the content of the KIT-6 mesoporous molecular sieve in example 2 is 2.3636; the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the KIT-6 mesoporous molecular sieve in example 3 was 2.107.
Example 4
This example is intended to illustrate a catalyst for the conversion of methyl t-butyl ether to propylene, prepared by the process of the present invention.
Catalyst D was prepared according to the method of example 1, except that KIT-6 mesoporous molecular sieve D was used instead of KIT-6 mesoporous molecular sieve a.
The specific surface area, pore volume and composition of catalyst D are shown in table 2; and by calculating: the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the content of the KIT-6 mesoporous molecular sieve is 2.2.
Example 5
This example is intended to illustrate a catalyst for the conversion of methyl t-butyl ether to propylene, prepared by the process 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: the content of the ZRP-5 zeolite molecular sieve is 62 percent, the content of the KIT-6 mesoporous molecular sieve A is 19 percent, the content of alumina from a binding agent is 11 percent, and the content of calcium oxide from a modified oxide is 8 percent.
The specific surface area, pore volume and composition of catalyst D are shown in table 2; and by calculating: the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the content of the KIT-6 mesoporous molecular sieve is 3.263.
Example 6
This example is intended to illustrate a catalyst for the conversion of methyl t-butyl ether to propylene, prepared by the process 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: the content of the ZRP-5 zeolite molecular sieve is 40 percent, the content of the KIT-6 mesoporous molecular sieve A is 35 percent, the content of alumina from a binding agent is 16 percent, and the content of calcium oxide from a modified oxide is 9 percent.
The specific surface area, pore volume and composition of catalyst F are shown in table 2; and by calculating: the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the content of the KIT-6 mesoporous molecular sieve is 1.143.
Example 7
This example is intended to illustrate a catalyst for the conversion of methyl t-butyl ether to propylene, prepared by the process 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: the content of the ZRP-5 zeolite molecular sieve is 70%, the content of the KIT-6 mesoporous molecular sieve A is 15%, the content of alumina from the adhesive is 14%, and the content of calcium oxide from the modified oxide is 1%.
The specific surface area, pore volume and composition of catalyst G are shown in table 2; and by calculating: the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the content of the KIT-6 mesoporous molecular sieve is 4.667.
Comparative example 1
Catalyst D1 was prepared under the same conditions as in example 1, except that: step (1) was eliminated and only step (2) was retained, i.e., KIT-6 mesoporous molecular sieve A was not used and "110 g ZRP-5 zeolitic molecular sieve" was replaced with "160 g ZRP-5 zeolitic molecular sieve".
Comparative example 2
According to the same manner as in example 1With the exception of the following conditions, catalyst D2 was prepared: replacing KIT-6 mesoporous molecular sieve A with commercially available silicon dioxide; wherein, the commercial silicon dioxide is a disordered mesoporous material, the average pore diameter is 23nm, and the specific surface area is 239m2Per g, pore volume 0.7cm3/g。
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 content of the ZRP-5 zeolite molecular sieve is 72%, the content of the KIT-6 mesoporous molecular sieve A is 9%, the content of alumina from the adhesive is 8%, and the content of calcium oxide from the modified oxide is 11%.
Test example 1
Taking a fixed bed reactor as an example, the performance evaluation result of the catalyst for preparing propylene by cracking methyl tert-butyl ether provided by the invention in the catalytic cracking reaction of methyl tert-butyl ether is illustrated.
Respectively filling 5.0G of catalyst A, catalyst B, catalyst C, catalyst D, catalyst E, catalyst F, catalyst G, 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 test results are shown in Table 3.
TABLE 1
TABLE 2
TABLE 3
Catalyst and process for preparing same
Reaction time (h)
MTBE average conversion (%)
Average yield of ethylene (%)
Average yield (%) of propylene
Catalyst A
150
100
6.5
24.3
Catalyst B
150
100
6.4
24.1
Catalyst C
150
100
6.7
24.6
Catalyst D
150
100
5.9
23.8
Catalyst E
150
100
5.7
23.5
Catalyst F
150
100
4.8
22.1
Catalyst G
150
100
4.6
21.9
Catalyst D1
150
100
3.6
20.3
Catalyst D2
150
100
3.8
20.8
Catalyst D3
150
100
3.5
19.9
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 converting methyl tert-butyl ether provided by the invention has excellent performance when used for preparing propylene by catalytic cracking of methyl tert-butyl ether.
Comparing the data of catalyst A and catalyst D1, it can be seen that a portion of the KIT-6 mesoporous molecular sieve was added to catalyst A, and the KIT-6 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 a portion of KIT-6 mesoporous molecular sieve was added to catalyst a, and a commercially available disordered silica material was used in place of KIT-6 mesoporous molecular sieve in catalyst D2. Compared with catalyst D2, the ethylene selectivity and the propylene selectivity of catalyst A are both improved significantly. The results show that the catalyst for converting methyl tert-butyl ether into propylene provided by the invention has excellent performance because the catalyst contains a certain amount of KIT-6 mesoporous molecular sieve with a three-dimensional structure.
Comparing the data for catalyst a and catalyst D3, it can be seen that the weight ratio of the content of the ZRP-5 zeolite molecular sieve to the KIT-6 mesoporous molecular sieve is 8 and the content of the modifying component is outside the appropriate range. As the content of the mesoporous molecular sieve is too low and the addition amount of the modifying component is too much, the catalyst has poor performance in reaction.
Comparing catalyst a with catalyst E and catalyst G, 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 F, 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 converting methyl tert-butyl ether provided by the invention has excellent performance because the catalyst simultaneously contains the ZRP-5 zeolite molecular sieve and the KIT-6 mesoporous molecular sieve and specific mixture ratio of the ZRP-5 zeolite molecular sieve and the KIT-6 mesoporous molecular sieve, and also contains specific contents of the ZRP-5 zeolite molecular sieve, the KIT-6 mesoporous molecular sieve, alumina and modified oxide.
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.
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