Conversion method for preparing propylene from methanol and catalyst used in conversion method

Abstract

The invention relates to a methanol-to-propylene conversion method and a catalyst used in the method, and belongs to the technical field of chemical engineering. Methanol is in contact with a high-shape-selective-activity catalyst in a parallel switching fixed bed; an active component of the catalyst is aluminum-rich Pentasil structure zeolite synthesized by taking zeolite containing 0.01%-3% of gallium as a crystal nucleus, the aluminum-rich Pentasil structure zeolite contains 6%-7% of aluminum oxide, and the crystal size is 2-4 microns; the catalyst is characterized in that a carrier which has a pore volume of 0.1-0.3 ml / g with a pore diameter of 3.5-4.5 nanometers except micropores and an n-hexane / cyclohexane adsorption ratio of more than or equal to 4 and accounts for 5-40% of the catalyst is composed of boron (accounting for 0.1-1% of the carrier)-doped high-pore-volume (0.5-1.2 ml / g) aluminum oxide and aluminum phosphate sol, and phosphorus accounts for 0.1-5% of the carrier. The MTP process and the catalyst thereof are high in conversion activity, good in product selectivity and high in material circulation and heat utilization rate, and the interval period of regeneration is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, in particular to a method for converting methanol into propylene and a catalyst used therefor. Background Art

[0002] Propylene is a basic petrochemical product widely used in the production of polypropylene, propylene oxide, acrylic acid, acrylonitrile, cumene, etc. It is mainly obtained from the petroleum processing process. However, the process of converting methanol produced from coal into propylene through catalysis has important strategic significance and application value and has been widely used in industrial applications.

[0003] The MTP process, which primarily converts methanol to propylene, primarily uses ZSM-5 zeolite as a catalyst and an adiabatic fixed-bed reactor. Its notable features include high propylene selectivity and P / E ratios. ExxonMobil and UOP in the United States, as well as research institutions in Germany, Japan, and China, have conducted related research. Early research conducted by ExxonMobil is reported in USP 3931349 and USP 3998899. Lurgi in Germany has developed methanol-to-propylene technology, as documented in documents such as EP 448000, DE 1020050159232, WO 192190, and WO 2006136433, and has built multiple plants for continuous operation.

[0004] USP 4035430 and USP 4542252 disclose a multi-stage fixed-bed adiabatic reactor system. The feedstock is first converted into an ether-rich equilibrium mixture in a catalytic dehydration reactor, which then enters a second reactor for further conversion, distributing the heat of reaction across the two stages. Furthermore, the reactors are loaded with zeolite catalyst in stages, with cooling between stages using either a coolant or the feedstock, either indirectly or directly, to maintain the inlet temperature of each bed and ensure a roughly uniform temperature rise across the beds.

[0005] Existing MTP process technology primarily originates from Lurgi. For example, patent document WO2004 / 018089 discloses a methanol-to-propylene reaction apparatus and conversion technology from Lurgi, Germany. Methanol first reacts with an acidic catalyst in a preheater to produce a balance of dimethyl ether, methanol, and water vapor. This mixture then reacts in a series of fixed-bed reactors to produce a propylene-rich mixture. According to reports, this reactor, by recycling non-propylene products after the reaction back into the reaction system, achieves an overall propylene selectivity of 70%. In addition to Lurgi, MG Technologies also discloses a similar fixed-bed reactor and a method for producing propylene from methanol in patent document WO01 / 92190.

[0006] Because the reactor setup significantly impacts the MTP process, there have been subsequent reports on existing technologies and improved methods for MTP setups, particularly reactors. For example, patent document WO2007 / 140844A1 discloses a process developed by Lurgi for producing propylene-based light olefins using a fixed-bed reactor. The process utilizes an axial-flow, multi-stage fixed-bed adiabatic reactor. Interstage quenching controls the reaction temperature, while a thin bed structure reduces reactor resistance, resulting in high propylene product selectivity. The process also effectively utilizes the phase transition heat from the vaporization of the liquid product to reduce the temperature of the reaction product in the upper bed.

[0007] A notable feature of MTP technology is that it requires a high propylene to ethylene mass ratio. However, during the conversion process, the propylene yield is often lower than that of ethylene. Therefore, it is necessary to improve the product selectivity of propylene during the conversion process. In the MTP conversion reaction, methanol is first dehydrated to form dimethyl ether. Then, the equilibrium mixture of dimethyl ether and methanol continues to react to form light olefins. In USP2003 / 0139635A1, the selectivity of propylene products was improved by adding a reactor for pre-dehydration of methanol to produce dimethyl ether and optimizing the reaction conditions.

[0008] Catalysts and their active components undoubtedly play a crucial role in the methanol conversion process to produce light olefins, forming a key element in the conversion process. It is generally believed that using non-ZSM-5 zeolites, such as SAPO-34 zeolite, results in methanol conversion to produce light olefins primarily consisting of ethylene, with relatively small amounts of propylene, as described in USP 5,817,906. Therefore, the MTP process, which primarily targets propylene, often utilizes a ZSM-5 zeolite as the active catalyst component and combines it with a fixed-bed reaction system.

[0009] The advantage of using a fixed-bed adiabatic reactor is its simple structure. Regardless of operational optimization, the zeolite catalyst in the reactor will gradually deactivate during the reaction due to severe carbon deposition, necessitating a gradual increase in reaction temperature until the process is shut down for regeneration. Typically, conversion processes employ multiple fixed-bed reactors, alternating between them for continuous reaction and regeneration. This places high demands on the performance of the catalyst and active components, compromising smooth operation and increasing operational complexity and overall operating costs.

[0010] Because the MTP process requires a high-performance catalyst, the active component, ZSM-5 zeolite, is generally considered to have excellent hydrothermal stability and coking resistance and is currently the preferred catalytic material for the MTP reaction. Further improvements to the ZSM-5 zeolite catalyst have primarily focused on modifying the silicon-aluminum ratio of the HZSM-5 zeolite, ion modification with various elements, hydrothermal treatment, mesoporation of the zeolite framework, and the use of small-crystal zeolites. These modifications aim to alter the acidity and pore structure of the active component and catalyst, enhance the catalyst's mass transfer capacity, improve propylene selectivity, and improve the catalyst's resistance to carbon deposition.

[0011] Patents such as USP 3911041, USP 4100219, USP 4049573, JP 60-126233, JP 61-97231, JP 62-70324, and Ger. Offen 28227385 all demonstrate chemical modification of zeolites, active components, with phosphorus, magnesium, silicon, and alkaline earth metals to adjust the acidity, acidity distribution, pore structure, and hydrothermal stability of the zeolite catalyst under hydrothermal conditions. The methanol-to-propylene conversion process is typically conducted at relatively low temperatures using a reaction-separation-recycle system. The primary methanol conversion rate is relatively low, typically 15% to 50%, and the catalyst's single-pass operating cycle is also relatively short. Summary of the Invention

[0012] In view of the current status of existing technologies, in the technical improvement of the methanol to propylene conversion method, further attention needs to be paid to increasing the olefin yield, improving the selectivity of the propylene product, increasing the P / E ratio, extending the catalyst regeneration interval, etc., as well as further improvements in the corresponding catalysts, active components and reaction systems.

[0013] The present invention provides a catalyst for preparing propylene from methanol, the catalyst comprising: an active component and a carrier;

[0014] The active component is an aluminum-rich pentasil structure zeolite synthesized from zeolite nuclei containing 0.01 wt% to 3 wt% gallium; wherein the aluminum oxide content is 6 wt% to 7 wt%, excluding micropores, the pore volume of pores with a diameter of 3.5 to 4.5 nanometers is 0.1 to 0.3 ml / g, the n-hexane / cyclohexane adsorption ratio is ≥4, and the crystal size is 2 to 4 microns;

[0015] The carrier is composed of boron-doped high-porous alumina and aluminum phosphate sol, wherein boron accounts for 0.1wt% to 1wt% of the total carrier, the pore volume of alumina is 0.5 to 1.2 ml / g, and phosphorus accounts for 0.1wt% to 5wt% of the total carrier;

[0016] The carrier accounts for 5 wt% to 40 wt% of the total catalyst.

[0017] Furthermore, the gallium content in the active component is 0.18wt% to 0.28wt%, the aluminum oxide content is 6.3wt% to 6.5wt%, and the crystal size is 2 to 4 microns;

[0018] The boron content of the carrier is 0.106 wt% to 0.11 wt%, the pore volume of alumina is 0.8 to 1 ml / g, the phosphorus content is 1.7 wt% to 1.9 wt%, and accounts for 20 wt% of the total amount of the catalyst.

[0019] Furthermore, the active component is prepared by the following method: using A, X, Y, Beta, M, L or ZSM series zeolite after gallium element exchange as a crystal nucleus, mixing it with a silicon source and an aluminum source at 40-100°C to form a gel, controlling [OH -1 ] / L is in the alkalinity range of 0.5 to 0.6, is synthesized by hydrothermal crystallization at 130 to 190° C., and gallium element accounts for 0.1 wt% to 1 wt% of the active component.

[0020] Furthermore, the gallium-containing zeolite nucleus is selected from X, Y, Beta, and ZSM-5 zeolites after gallium element exchange, and the best is selected from X, Y, and Beta zeolites after gallium element exchange, and is mixed with silicon source and aluminum source to form a gel at 90-95°C to control [OH -1 ] / L is in the range of 0.56 to 0.58, and the process is hydrothermal crystallization synthesis at 150 to 190° C., and the gallium content accounts for 0.4 wt % to 0.6 wt % of the active component.

[0021] Furthermore, the catalyst is formed by tableting, extrusion or ball rolling.

[0022] The present invention also provides a method for converting methanol to propylene, using the above-mentioned catalyst, comprising the following steps:

[0023] (a) Methanol is allowed to stand for 1 to 20 hours. 1 The mass space velocity enters the reaction device at 150~700℃;

[0024] (b) contacting and reacting with a catalyst bed (1 to 10 layers) in a continuous reaction apparatus consisting of 2 to 8 switchable fixed beds connected in parallel;

[0025] (c) condensing and separating the reaction product to obtain propylene;

[0026] (d) returning unconverted methanol and part of the by-products to the reactor for cyclic reaction;

[0027] (e) The catalyst deactivated by carbon deposition is regenerated using hot air at a temperature of 550-750°C.

[0028] Furthermore, the regeneration conditions in the fixed bed reactor are as follows: after the bed is switched and the feed is stopped, it is purged with water vapor and / or nitrogen, and then hot air at 580-680°C is introduced for regeneration for 1-20 hours, so that the catalyst carbon deposition is reduced from 5-10wt% to 0.5-1wt%.

[0029] Furthermore, the reaction products are subjected to two-stage condensation separation, oil-water-gas three-phase separation, drying and deep-cold separation to obtain propylene and ethylene; the separated by-products C4 hydrocarbons and C5-C7 liquid hydrocarbons are returned to the reaction device for further catalytic cracking into light olefins; in the water phase after the three-phase separation, unconverted methanol and dimethyl ether are recycled back to the reaction device.

[0030] The present invention provides a methanol-to-propylene conversion method, wherein the reaction system for converting methanol to propylene comprises: the catalyst; methanol feed, diluent gas and / or water; a continuous reaction device consisting of a switchable fixed-bed reactor; a three-phase separation device, an adsorption separation device, and a cryogenic separation device; a drying device and a condensing device; and the pressure range in the reaction device and the reaction system is 0.05 to 0.6 MPa.

[0031] In the methanol-to-propylene conversion method provided by the present invention, the reaction temperature can be controlled by fixing the outlet temperature or by gradually increasing the temperature within the process conditions according to the reaction progress, which is not further limited in the present invention. The raw materials, process water, circulating unconverted materials, and the medium and high-temperature heat-conducting medium involved are also not further limited. The specific structure and operation of the fixed-bed reactor involved are not further limited in the present invention.

[0032] It is well known to those skilled in the art that the conversion method, active components and catalyst, and reaction system constitute the content, system and characteristics of the present invention, and are different from the prior art. They are the most important factors affecting the catalytic conversion of methanol into the target product propylene. Since the mutual influence faces great uncertainty and does not show a simple linear law, it is difficult to obtain direct inspiration from the existing technology, and it is also difficult to obtain the expected results through simple permutation and combination experiments based on the existing technology.

[0033] The present invention provides a methanol-to-propylene conversion method having high shape-selective catalytic conversion performance for methanol raw materials. Under the conversion action of unique (aluminum-rich, large crystals, and easy diffusion) highly shape-selective catalytic active components and catalysts, side reactions and coking are suppressed during the reaction process, and the probability of deactivation is reduced. At the same time, propylene selectivity and P / E ratio are increased, the product yield and stability of the conversion process are improved, and the regeneration interval and service life of the catalyst are extended, thereby facilitating the stable operation of the process. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0035] In the examples, the composition analysis of the raw materials and reaction products was performed using an Agilent 6890N gas chromatograph. For other analytical tests, reference may be made to the relevant analytical methods in the National Standard for Testing Methods for Petroleum and Petroleum Products, published by China Standards Press in 1989, and the Petrochemical Analytical Methods (RIPP Test Method), published by Science Press in 1990.

[0036] Example 1

[0037] In this example, the gallium-containing zeolite nuclei required for the present invention were prepared by adding deionized water at a weight ratio of zeolite to soluble gallium salt of 1:0.5 and a liquid-to-solid ratio of 10:1. The mixture was heated to 95° C. and stirred. Gallium ions were exchanged with commercial zeolites X, Y, Beta, and ZSM-5 using a gallium nitrate solution prepared from commercial chemicals. After filtration and drying, gallium-containing GaX, GaY, GaBeta, and GaZSM-5 zeolites were obtained, respectively, to serve as gallium-containing zeolite nuclei for further preparation of active components.

[0038] Example 2

[0039] In this example, the active components required for the methanol to propylene catalyst of the present invention were prepared by referring to the preparation steps such as gelation and hydrothermal crystallization in USP 3,702,886. The different types of gallium-containing zeolites prepared in Example 1 were used as crystal nuclei. For ease of comparison, the elemental composition and preparation raw materials were kept as close as possible.

[0040] By controlling the amount of zeolite nuclei fed, the gallium content in the total material composition on a dry basis is controlled to be 0.4 wt% to 0.6 wt%; an industrial sodium silicate solution is used as a silicon source and an alkali source, the temperature is raised to 90° C. to 95° C. under stirring, an industrial aluminum sulfate solution is used as an aluminum source, and the Si / Al molar ratio on a dry basis is controlled within a range of 20 to 30; the acidity and alkalinity of the material are adjusted by using an industrial dilute sulfuric acid solution to control the material alkalinity [OH -1 ] / L is within the range of 0.56 to 0.58; after uniform stirring, the temperature is raised to 150°C to 190°C for crystallization, and by tracking sampling, when the relative crystallinity reaches 90%, the temperature is lowered to stop the hydrothermal crystallization, and the zeolite is filtered, washed, and dried to obtain a sodium-type pentasil structured gallium-containing aluminum-rich zeolite, wherein the aluminum oxide is 6.3wt% to 6.5wt% on a dry basis.

[0041] Deionized water was added at a weight ratio of zeolite to soluble ammonium salt of 1:0.5 and a liquid-to-solid ratio of 10:1. The mixture was heated to 95°C and stirred. Ammonium ion exchange was then performed on each zeolite product synthesized from different nuclei using a commercial ammonium sulfate solution. After filtration, the ammonium exchange was repeated once until the sodium ion content of the zeolite, on a dry basis, was less than 0.1 wt%. The zeolite was then dried and used as the active component for the catalyst of the present invention.

[0042] Example 3

[0043] This example prepares the highly shape-selective MTP catalyst required for the present invention. Referring to the catalyst shaping preparation method and steps described in "Catalyst Production - Laboratory and Industrial Preparation" by AB Steles, the catalyst is prepared using aluminum phosphate sol and high-porous alumina as the bialuminum binder and carrier. For ease of comparison, the binder and carrier, as well as the feed ratio of zeolite, are as close or identical as possible, with the zeolite accounting for 80 wt% on a dry basis. The aluminum phosphate sol and high-porous alumina (pore volume 0.9-0.95 g / mL) were provided by Sichuan Runhe Catalytic Materials Co., Ltd., China. The formed catalyst is activated by calcining in a muffle furnace at 550°C for 4 hours with water vapor, to obtain the MTP catalyst of the present invention.

[0044] Comparative Example 1

[0045] This comparative example utilizes a relatively classic zeolite synthesis and catalyst preparation technique from the prior art to produce a representative comparative sample for further comparison. ZSM-5 zeolite was prepared according to the procedures outlined in USP 3,702,886 and the examples. Similarly, a comparative catalyst with an alumina binder and support was prepared using the same active component weight ratio and catalyst molding method as in Example 1.

[0046] Example 4

[0047] This example illustrates the physicochemical properties of the highly shape-selective MTP catalyst prepared according to the present invention. Due to factors such as the zeolite preparation process, pH adjustment and control during gelation, material temperature increase during hydrothermal crystallization, and temperature control during crystallization, the physicochemical properties of the crystallized product can exhibit a certain degree of volatility. For ease of comparison, a group of relatively similar experimental products were selected as catalysts for further methanol conversion and evaluation. The comparative properties are shown in Table 1.

[0048] Table 1 Comparison of properties of the MTP catalysts of the present invention and the comparative catalysts

[0049]

[0050]

[0051] The comparative adsorption experiment between n-hexane and cyclohexane was carried out at 20°C to compare the differences in shape-selective adsorption and catalytic performance of active components.

[0052] Example 5

[0053] This example illustrates a methanol-to-propylene conversion method and the effectiveness of the catalyst in this invention. The conversion method and reaction system described herein utilize industrial methanol with a methanol content of ≥96 wt% as the raw material. The specific implementation steps are as follows:

[0054] (1) Four fixed-bed reactors with a catalyst loading of 40 ml (each reaction tube is separated into two catalyst beds by quartz sand) are connected through valves and pipelines to form a switchable continuous reaction device; and are connected to a (oil, water, gas) three-phase separation tank, an adsorption separation tank, a condenser, a drying tube, and a freezing separation tank to form a small-scale reaction-regeneration and separation experimental device;

[0055] (2) The methanol feed was diluted with deionized water, with a water to methanol mass ratio of 2.0, and the feed was heated at a space velocity of 1.5 (WHSV) h- 1 The pressure entering the reaction device, the reaction device and the separation system is 0.1MP;

[0056] (3) By temperature control and valve switching, the bed temperature of the series reactor I is set to 210°C, the bed temperature of the reactor II is set to 470°C, and the bed temperature of the reactor III is set to 530°C;

[0057] (4) The converted product gas enters a three-phase separation tank, an adsorption separation tank, a condenser (serving as a front-stage condenser, the temperature is maintained at 10-30°C), a drying tube, and a freezing separation tank (serving as a rear-stage condenser, the temperature is maintained at -5--10°C), where propylene and ethylene are obtained through condensation and separation;

[0058] (5) The unconverted methanol and dimethyl ether in the aqueous phase obtained after separation in the three-phase separation tank are recycled back to reactor I for a cyclic reaction; the unconverted part of the product obtained after separation in the freezing separation tank is returned to reactor III for a cyclic reaction;

[0059] (6) After the bed of the catalyst reaction tube is deactivated by carbon deposition, the feed is switched and the series reaction device is cut out and used as the fourth reactor for a simulated regeneration experiment. After purging with water vapor and / or nitrogen, it is regenerated with high-temperature hot air. The temperature control range is 660-670°C. The regeneration takes 4 hours to reduce the carbon deposition of the catalyst (5-10wt%) to 0.5-1wt%.

[0060] Table 2 Comparison of operation results of methanol to propylene conversion reaction in fixed bed reactor

[0061] project Example 4a Example 4b Example 4c Comparative Example 1 Total methanol conversion rate / % 99 99 98 94 Total propylene selectivity / % 47 48 46 41 Product P / E ratio 1.8 1.8 1.7 1.6 Total olefin selectivity / % 66 68 69 73 Regeneration interval cycle / min ～800 ～900 ～750 ～400

[0062] The methanol-to-propylene conversion method provided by the present invention, including a catalyst and reaction system, demonstrates superior performance compared to typical prior art methods in the methanol-to-propylene conversion reaction in a fixed-bed reactor. This method, including active components and catalysts, exhibits improved catalytic performance, conversion efficiency, and propylene product selectivity; extends the effective reaction time and regeneration cycle interval, thereby reducing process energy consumption; and, through adsorption separation and recycling of unconverted methanol and byproducts, conserves materials, improves conversion efficiency, and reduces environmental impact. These results also contribute to reducing the overall cost of the fixed-bed methanol-to-propylene process.

[0063] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A catalyst for methanol to propylene, characterized in that: The catalyst comprises: an active component and a carrier; The active component is an aluminum-rich pentasil structure zeolite synthesized from zeolite nuclei containing 0.01 wt% to 3 wt% gallium; wherein the aluminum oxide content is 6 wt% to 7 wt%; excluding micropores, the pore volume of pores with a diameter of 3.5 to 4.5 nanometers is 0.1 to 0.3 ml / g, the n-hexane / cyclohexane adsorption ratio is ≥4, and the crystal size is 2 to 4 microns; The carrier is composed of boron-doped high-porous alumina and aluminum phosphate sol, wherein boron accounts for 0.1wt% to 1wt% of the total carrier, the pore volume of alumina is 0.5 to 1.2 ml / g, and phosphorus accounts for 0.1wt% to 5wt% of the total carrier; The carrier accounts for 5 wt% to 40 wt% of the total catalyst.

2. The catalyst according to claim 1, characterized in that The gallium content in the active component is 0.18wt% to 0.28wt%, the aluminum oxide content is 6.3wt% to 6.5wt%, and the crystal size is 2 to 4 microns; The boron content of the carrier is 0.106 wt% to 0.11 wt%, the pore volume of alumina is 0.8 to 1 ml / g, the phosphorus content is 1.7 wt% to 1.9 wt%, and accounts for 20 wt% of the total amount of the catalyst.

3. The catalyst according to claim 1, characterized in that The active component is prepared by the following method: using A, X, Y, Beta, M, L or ZSM series zeolite after gallium element exchange as a crystal nucleus, mixing it with a silicon source and an aluminum source at 40-100° C. to form a gel, controlling the [OH -1 ] / L is in the alkalinity range of 0.5 to 0.6, is synthesized by hydrothermal crystallization at 130 to 190° C., and gallium element accounts for 0.1 wt% to 1 wt% of the active component.

4. The catalyst according to claim 3, characterized in that The gallium-containing zeolite nucleus is selected from X, Y, and Beta zeolites exchanged with gallium elements, and is mixed with silicon source and aluminum source at 90-95° C. to form a gel. -1 ] / L is in the range of 0.56 to 0.58, and the process is hydrothermal crystallization synthesis at 150 to 190° C., and the gallium content accounts for 0.4 wt % to 0.6 wt % of the active component.

5. The catalyst according to claim 1, characterized in that The catalyst is formed by tableting, extrusion or ball rolling.

6. A method for converting methanol to propylene, characterized in that: Using the catalyst according to any one of claims 1 to 5, comprising the following steps: (a) Methanol is allowed to stand for 1 to 20 hours. 1 The mass space velocity enters the reaction device at 150~700℃; (b) contacting and reacting with a catalyst bed (1 to 10 layers) in a continuous reaction apparatus consisting of 2 to 8 switchable fixed beds connected in parallel; (c) condensing and separating the reaction product to obtain propylene; (d) returning unconverted methanol and part of the by-products to the reactor for cyclic reaction; (e) The catalyst deactivated by carbon deposition is regenerated using hot air at a temperature of 550-750°C.

7. The conversion method according to claim 6, characterized in that The regeneration conditions in the fixed bed reactor are as follows: after the bed is switched and the feed is stopped, it is purged with water vapor and / or nitrogen, and then hot air at 580-680° C. is introduced for regeneration for 1-20 hours to reduce the carbon deposit on the catalyst from 5-10 wt % to 0.5-1 wt %.

8. The conversion method according to claim 6, characterized in that The reaction products are subjected to two-stage condensation separation, oil-water-gas three-phase separation, drying and deep-cold separation to obtain propylene and ethylene; the separated by-products C4 hydrocarbons and C5-C7 liquid hydrocarbons are returned to the reaction device for further catalytic cracking into light olefins; in the water phase after the three-phase separation, the unconverted methanol and dimethyl ether are recycled back to the reaction device.

9. The transformation method according to claim 6, characterized in that The reaction system for converting methanol to propylene comprises: the catalyst according to claims 1-5; methanol feed, diluent gas and / or water; a continuous reaction device consisting of a switchable fixed bed reactor; a three-phase separation device, an adsorption separation device, a cryogenic separation device; a drying device, and a condensing device.

10. The transformation method according to claim 6, characterized in that The operating pressure of the reaction system is 0.05-0.6 MPa.

Images