CN105294374A - Method for preparing paraxylene and propylene by methanol and/or dimethyl ether - Google Patents

Abstract

The invention relates to a method for preparing paraxylene and propylene by methanol and/or dimethyl ether. The method comprises the following steps: carrying out aromatization reaction on the the methanol and/or the dimethyl ether; carrying out alkylation reaction on ethylene, the methanol and/or the dimethyl ether; and coupling the two reactions. According to the method disclosed by the invention, components rich in ethylene in reaction by-products during preparation of the paraxylene by the methanol and/or the dimethyl ether in the presence of a catalyst are returned to a reaction system, then the alkylation reaction is carried out on the components, the methanol and/or the dimethyl ether, and the paraxylene and the propylene can be produced in a high-selectivity mode.

Description

A method for preparing p-xylene and propylene from methanol and/or dimethyl ether

technical field

The invention relates to a method for preparing p-xylene and propylene by reacting methanol and/or dimethyl ether, which belongs to the field of chemical industry.

Background technique

Both p-xylene (PX) and propylene are important basic chemical raw materials. At present, p-xylene is mainly obtained through aromatics complex. First, naphtha is continuously reformed to obtain aromatics-containing reformed oil, and then through aromatics extraction, aromatics fractionation, disproportionation and alkylation, and xylene isomerization Chemical and adsorption separation units to maximize the production of PX. Since the content of p-xylene in the three isomers is controlled by thermodynamics, p-xylene only accounts for about 23% of C ₈ mixed aromatics, so the entire PX production process has a large amount of material circulation, huge equipment, and high operating costs. . In particular, the difference between the boiling points of the three isomers of xylene is very small, and high-purity p-xylene cannot be obtained by ordinary distillation techniques, but an expensive adsorption separation process must be used. Propylene is mainly derived from petroleum refineries and naphtha steam cracking to produce ethylene by-products, or from natural gas processing propane as raw material for production. P-xylene is mainly used to produce polyester, and propylene is mainly used to prepare polypropylene, acrylonitrile and 1,3-propanediol required for the production of polyester. With the rapid development of the global economy, p-xylene and The demand for propylene is also increasing year by year.

The preparation of aromatics from methanol is a new way to produce aromatics by non-petroleum route. Chinese patent CN101244969 discloses a kind of C ₁ -C ₂ hydrocarbons or methanol aromatization and catalyst regeneration fluidized bed device, utilize this device and catalyst, can adjust the coking state of the catalyst in the aromatization reactor at any time, thereby The purpose of continuously and efficiently converting C ₁ -C ₂ hydrocarbons or methanol and generating aromatics with high selectivity is achieved. Chinese patent CN1880288 discloses a process for methanol conversion to aromatics. On the modified ZSM-5 molecular sieve catalyst, methanol is catalytically converted into aromatics-based products, which has the advantages of high overall selectivity of aromatics and flexible process operation. U.S. Patent No. 4,615,995 discloses a ZSM-5 molecular sieve catalyst loaded with Zn and Mn for methanol conversion to prepare olefins and aromatics. The content of low-carbon olefins/aromatics in the product can be changed by adjusting the content of Zn and Mn in the catalyst. ratio.

Methanol to olefins and methanol to propylene are new ways to produce ethylene and propylene by non-petroleum routes. In 1976, Mobil Oil Company carried out the conversion reaction of methanol to hydrocarbons on ZSM-5 molecular sieve catalyst. USP4,035,430 discloses the process of methanol converting gasoline on the ZSM-5 molecular sieve catalyst; USP4,542,252 discloses the technology of methanol producing low-carbon olefins on the ZSM-5 molecular sieve catalyst; USP3,911,041, USP4,049,573, USP4 , 100,219, JP60-126233, JP61-97231 and JP62-70324 disclose the use of ZSM-5 molecular sieve catalysts modified by phosphorus, magnesium, silicon or alkali metal elements to prepare low-carbon olefins from methanol; USP5,367,100 discloses Dalian Institute of Chemical Physics has used ZSM-5 molecular sieve catalyst modified by phosphorus and lanthanum to produce light olefins from methanol or methanol and/or dimethyl ether. The total selectivity of ethylene and propylene is only about 65wt%, and ethylene , propylene and butene total selectivity greater than 85wt%.

CN101767038B and CN101780417B disclose a catalyst and method for the co-production of low-carbon olefins from methanol to p-xylene, pointing out that the three basic chemicals ethylene, ethylene, and The purpose of propylene and p-xylene. Among the hydrocarbon products obtained from the reaction, the selectivity of p-xylene in aromatic hydrocarbons is greater than 80 wt%, and the selectivity of ethylene and propylene in _C1 - _C5 low-carbon hydrocarbons is greater than 80 wt%. However, the disadvantage of this method is that cryogenic separation technology must be used to obtain high-purity ethylene products, and the investment and energy consumption are large, which directly affects the economy of the process.

In addition, CN101780417B relates to the method for preparing _p ^- xylene and low-carbon olefins (ethylene and propylene) by methanol conversion, which does not involve in order to further increase the production of propylene and avoid the difficulty of ethylene separation. The process of alkylation to increase the production of propylene. CN102464550A discloses a method for co-producing light olefins and p-xylene, the method includes C4 and C5 hydrocarbons entering the first reaction zone to produce olefins, which is a process of _C4 or liquefied gas cracking to produce olefins, wherein also The process of producing propylene by alkylation of ethylene and methanol/dimethyl ether is not involved.

Contents of the invention

The object of the present invention is to provide a kind of method that methyl alcohol and/or dimethyl ether make p-xylene and propylene.

For this reason, the present invention provides a kind of method for methyl alcohol and/or dimethyl ether system p-xylene and propylene, comprises the following steps:

a) The raw material containing methanol and/or dimethyl ether is contacted and reacted with the catalyst in the reaction system; the ethylene ^{-rich C2-} _component coming out of the reaction system is returned to the reaction system, and is mixed with the raw material in the The reaction continues on the catalyst to produce propylene;

b) C ₆ ⁺ components from the reaction system are separated to obtain the product p-xylene; and

_c ) The C3 component coming out of the reaction system is separated to obtain the product propylene.

In a preferred embodiment, the reaction system comprises a first reaction zone and a second reaction zone, and the method comprises the following steps:

a) The raw material containing methanol and/or dimethyl ether first passes through the first reaction zone to contact catalyst I for aromatization reaction, and then enters the second reaction zone to contact catalyst II for alkylation reaction; The ethylene ^{-rich C2-} _components from the second reaction zone are returned to the second reaction zone, and undergo an alkylation reaction with methanol and/or dimethyl ether in the second reaction zone on the catalyst II to generate propylene;

b) the C ₆ ⁺ component from the second reaction zone is further separated to obtain the product p-xylene; and

_c ) The C3 component coming out of the second reaction zone is further separated to obtain propylene.

In a preferred embodiment, the reaction system comprises a first reaction zone and a second reaction zone, and the method comprises the following steps:

a) The raw material containing methanol and/or dimethyl ether is first contacted with the catalyst I through the first reaction zone to undergo an aromatization reaction to obtain the product A. After the product A is separated by the separation system, the ethylene-rich C ₂ ^- The components are returned to the second reaction zone, and carry out an alkylation reaction with methanol and/or dimethyl ether entering the second reaction zone on the catalyst II to obtain product B; product A and product The ethylene ^{-rich C2-} _component in B continues to return to the second reaction zone, and contacts with methanol and/or dimethyl ether in the second reaction zone on catalyst II for an alkylation reaction to generate propylene;

b) the C ₆ ⁺ components in the product A and product B are further separated to obtain the product p-xylene; and

_c ) The C3 component in the product A and product B is further separated to obtain the product propylene.

In a preferred embodiment, the catalyst, the catalyst I and the catalyst II contain the same or different modified zeolite molecular sieve catalysts.

In a preferred embodiment, the modified zeolite molecular sieve catalyst is obtained by modifying ZSM-5 and/or ZSM-11 zeolite molecular sieves with noble metals, rare earth metals and siloxane compounds.

In a preferred embodiment, in the modified zeolite molecular sieve catalyst, the content of the noble metal is 0.1-10 wt% of the total weight of the catalyst.

In a preferred embodiment, the content of the rare earth metal is 0.1-5 wt% of the total weight of the catalyst.

In a preferred embodiment, the amount of Si modified and supported by the siloxane-based compound is 1-10 wt% of the total weight of the modified zeolite molecular sieve catalyst.

In a preferred embodiment, the noble metal is silver; the rare earth metal is lanthanum.

In a preferred embodiment, the siloxane-based compound used for modification of the siloxane-based compound has a structural formula as shown in the following formula:

Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a C _1-10 alkyl group.

In a preferred embodiment, the siloxane-based compound is ethyl orthosilicate.

In a preferred embodiment, the reaction zone comprises one reactor or a plurality of reactors connected in series and/or in parallel; and preferably, the reactor is selected from fixed bed, fluidized bed and moving bed One or more of the reactors.

In a preferred embodiment, the first reaction zone and the second reaction zone are in the same reactor; and preferably, the reactor is selected from fixed bed, fluidized bed and moving bed reactors one or more of .

In a preferred embodiment, the first reaction zone includes one reactor or multiple reactors connected in series and/or in parallel; the second reaction zone includes one reactor or multiple reactors connected in series and/or A reactor connected in parallel; and between the first reaction zone and the second reaction zone, connected in series or in parallel; and preferably, the reactor is selected from fixed bed, fluidized bed and One or more of moving bed reactors.

The beneficial effects of the present invention include but are not limited to the following aspects: The present invention provides a new method for producing p-xylene and propylene with methanol and/or dimethyl ether, wherein the ethylene ^- rich C ₂ -group in the reaction product Alkylation reaction with methanol and/or dimethyl ether to further generate propylene, and finally obtain p-xylene and propylene with high selectivity. On the one hand, it avoids the high cost of ethylene product separation, and on the other hand, it can further increase production with more Propylene products in large market demand can effectively improve the economics of this technology.

Description of drawings

Figure 1 is a flow diagram of a method according to one embodiment of the invention.

Figure 2 is a flow diagram of a method according to another embodiment of the invention.

Figure 3 is a flow chart of a method according to another embodiment of the invention.

Figure 4 is a flow diagram of a method according to another embodiment of the invention.

detailed description

In the method of the present invention, two reaction processes, the aromatization reaction of methanol and/or dimethyl ether and the alkylation reaction of ethylene and methanol and/or dimethyl ether, are coupled to simultaneously prepare p-xylene and propylene with high selectivity. Specifically, at first the raw material methanol and/or dimethyl ether are contacted with the catalyst (the catalyst exists in the reactor) in the reaction system to carry out the aromatization reaction, and the generated product enters the separation system (such as a fractionation tower, etc.) for separation; After separation, C ₆ ⁺ components (aromatics with a carbon number equal to or greater than 6), C ₄ -C ₅ components (hydrocarbons with a carbon number of 4 and 5), and C ₃ components (propylene with a carbon number equal to 3 and Propane) and ethylene ^- rich C ₂ -components (hydrocarbons with carbon number less than or equal to 2 and CO, CO ₂ and H ₂ ) and water (H ₂ O), wherein, ethylene ^- rich C ₂ -components return Reaction system, C ₆ ⁺ components are further separated (such as rectification tower, crystallization separation system, etc.) to obtain p-xylene, C ₃ components are further separated (such as rectification tower, etc.) to obtain propylene, and a small amount of C ₄ -C ₅ components and H ₂ O are collected and used for other purposes. Wherein said reaction system can be a single reaction zone, also can be the combination of two or more reaction zones, a plurality of reaction zones can be in the same reactor, also can be respectively in a plurality of serial or parallel reactors . Preferably, the reactor is any one or more of fixed bed, fluidized bed or moving bed.

In a preferred embodiment, a reaction scheme according to the method of the present invention is shown in FIG. 1 . In Figure 1, the reaction system is composed of a reactor with a reaction zone, wherein the raw material methanol and/or dimethyl ether is contacted with the catalyst in the reaction zone of the reaction system, and the resulting product is separated by the separation system , to obtain C ₆ ⁺ components, C ₄ -C ₅ components, C ₃ components and C ₂ -components (including ethylene ^- rich C ₂ ^-components and purge gas) and H ₂ O, in which, rich The C ₂ ^- component containing ethylene is returned to the reaction system, the C ₆ ⁺ component is further separated to obtain p-xylene, and the C ₃ component is further separated to obtain propylene.

In a preferred embodiment, a reaction scheme according to the method of the present invention is shown in FIG. 2 . In Fig. 2, the reaction system is made up of a reactor with two reaction zones, the main reaction of the first reaction zone is methanol and/or dimethyl ether aromatization reaction, and the main reaction of the second reaction zone is ethylene (No. A by-product of a reaction zone) is alkylated with methanol and/or dimethyl ether. The raw material methanol and/or dimethyl ether first pass through the first reaction zone and contact with the catalyst I therein for reaction, then pass through the second reaction zone and contact with the catalyst II therein for the reaction, and the generated products enter the separation system for separation; they are separated by the separation system Finally, C ₆ ⁺ components, C ₄ -C ₅ components, C ₃ components and C ₂ -components (including ethylene ^- rich C ₂ ^-components and purge gas) and H ₂ O are obtained, which are rich in The C ₂ ^-component of ethylene is returned to the second reaction zone and is contacted with methanol and/or dimethyl ether entering the second reaction zone to carry out an alkylation reaction with catalyst II; the C ₆ ⁺ component is further separated to obtain p-xylene, _The C3 component is further separated to obtain propylene.

In a preferred embodiment, a reaction scheme according to the method of the present invention is shown in FIG. 3 . In Fig. 3, the reaction system is composed of two reaction zones respectively in two parallel reactors, the main reaction in the first reaction zone is the aromatization reaction of methanol and/or dimethyl ether, and the main reaction in the second reaction zone is The reaction is the alkylation of ethylene (by-product of the first reaction zone) with methanol and/or dimethyl ether. First, methanol and/or dimethyl ether are contacted with catalyst I in the reaction zone for aromatization to generate product A, and product A enters the separation system for separation; the ethylene ^{-rich C2-} _component obtained after separation is returned to the second reaction zone, Alkylation reaction with methanol and/or dimethyl ether entering the second reaction zone on catalyst II to generate product B, which enters the separation system for separation; after separation by the separation system, the C ₂ ^-group rich in ethylene The parts are returned to the second reaction zone, and the C ₆ ⁺ component obtained after the product A and product B are separated by the separation system is further separated to obtain p-xylene, and the C ₃ component is further separated to obtain propylene.

In a preferred embodiment, a reaction scheme according to the method of the present invention is shown in FIG. 4 . In Fig. 4, except that the reaction system is composed of two reaction zones respectively in the same reactor, its reaction process is the same as that described above with respect to Fig. 3, and will not be repeated here. Such a reaction system can be passed through Multi-stage feeding is realized.

In the present invention, the catalysts used are ZSM-5 and/or ZSM-11 zeolite molecular sieves modified ZSM-5 and/or ZSM- 11 Zeolite molecular sieve catalyst. When there are two reaction zones, the catalyst I and catalyst II respectively present therein may be the same or different catalysts. For example, in a preferred embodiment, the catalyst I and the catalyst II are the same catalyst or the same catalyst. More preferably, after the surface of the catalyst, catalyst I or catalyst II used in the present invention is modified with a siloxane compound, the loading amount of Si is 1-10 wt% of the total weight of the catalyst.

In a preferred embodiment, the preparation process of the catalyst used in the present invention is as follows:

(1) Prepare ZSM-5 and/or ZSM-11 zeolite molecular sieve raw powder through NH ₄ ⁺ ion exchange and roasting to prepare acidic zeolite molecular sieve.

(2) Immersing the above-mentioned acidic zeolite molecular sieve in a soluble salt solution of noble metal and rare earth metal to obtain a metal-modified zeolite molecular sieve.

(3) Surface modification of the metal-modified zeolite molecular sieve with a siloxane-based reagent to further adjust the acidity and pore structure of the outer surface of the molecular sieve to obtain a modified zeolite molecular sieve catalyst.

Preferably, after the catalyst, catalyst I or catalyst II used in the present invention is jointly modified by noble metal and rare earth metal, the content of noble metal is 0.1-10wt% of the total weight of the catalyst; the content of rare earth metal is 0.1% by weight of the total weight of the catalyst. -5 wt%.

Preferably, the noble metal used in the present invention is silver; the rare earth metal is lanthanum, which is used in the form of their soluble salts.

Preferably, the siloxane-based compound used in the present invention is represented by the following formula:

Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently C _1-10 alkyl, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl, and their isomeric form.

Preferably, the siloxane-based compound used is tetraethylorthosilicate.

Preferably, both the first reaction zone and the second reaction zone in the present invention can use a fixed-bed reaction process, and at the same time, a fluidized-bed or moving-bed reaction process can be used in combination with the regenerator. The first reaction zone and the second reaction zone can be implemented in one reactor or in a plurality of the same or different reactors connected in series or in parallel, respectively, through multi-stage feeding.

In the method of the present invention, methanol and/or dimethyl ether aromatization reaction, ethylene and methanol and/or dimethyl ether alkylation reaction temperature are in the range of 300-600°C, and methanol and/or dimethyl ether aromatization The preferred reaction temperature for the alkylation reaction is 450-520°C, and the preferred reaction temperature for the alkylation reaction of ethylene with methanol and/or dimethyl ether is 350-500°C.

In the method of the present invention, the mass space velocity of methanol and/or dimethyl ether aromatization reaction feed is 0.1-10h ^-1 , preferably 1-5h ^-1 , calculated as methanol and/or dimethyl ether. Wherein the molar ratio of ethylene to methanol and/or dimethyl ether is arbitrarily selected within the range of 0.1-10, generally preferably 0.5-5.

In the present invention, the C ₂ ^-component refers to a component with carbon atoms less than or equal to 2 in the molecular formula, including ethylene, ethane, methane, CO, CO ₂ and H ₂ , etc., that is, the C ₂ ^-component includes C ₂ ^-component of ethylene and purge gas. The purge gas is mainly ethane, methane, CO, CO ₂ and H ₂ and so on.

In the present invention, the C3 component refers to a compound with ₃ carbon atoms in the molecular formula, including propylene, propane and the like.

In the present invention, the C ₄ -C ₅ component refers to a component with carbon atoms equal to 4 or 5 in the molecular formula, including isobutane, isobutene, butane, 1-butene, 2-butene, and isopentane , Neopentane, pentane, 1-pentene, 2-pentene, etc.

In the present invention, the C ₆ ⁺ component refers to a component with 6 or more carbon atoms in the molecular formula, including p-xylene and other aromatic hydrocarbons and their derivatives.

The present invention is described in detail below by examples, but the present invention is not limited to these examples.

The gas chromatograph analyzes the product composition on-line, and the analysis conditions are:

Chromatography model: VarianCP3800

Chromatographic column: CPWax52CB capillary column

Carrier gas: helium, 5ml/min

Oven temperature: 60-220°C, programmed temperature rise, 15°C/min

Injection port temperature: 260°C

Detector: Hydrogen Flame Ionization Detector (FID)

Detector temperature: 300°C

Example 1

Catalyst preparation: silver lanthanum and silane modified HZSM-5 molecular sieve catalyst and HZSM-11 Molecular sieve catalyst

1) 500g ZSM-5 zeolite molecular sieve raw powder (Fushun Petrochemical Company Catalyst Factory) (SiO ₂ /Al ₂ O ₃ =68) and 500g ZSM-11 zeolite molecular sieve raw powder (Nankai University Catalyst Factory) (SiO ₂ /Al ₂ O ₃ =50) were roasted at 550°C to remove the template agent, exchanged 4 times with a 0.5 molar equivalent ammonium nitrate solution in a water bath at 80°C, dried in air at 120°C after the exchange, and roasted at 550°C for 3 hours to obtain HZSM respectively -5. HZSM-11 zeolite molecular sieve.

2) Take 100 g of the HZSM-5 and HZSM-11 zeolite molecular sieves prepared in step 1) respectively, and press them into tablets to obtain 40-60 mesh samples after crushing and screening, and impregnate them with 6% silver nitrate (AgNO ₃ ) solution at room temperature After 4 hours, pour out the upper layer liquid, dry at 120°C, and bake in air at 550°C for 6 hours to obtain silver-modified Ag-HZSM-5 and Ag-HZSM-11 zeolite molecular sieves.

3) respectively impregnating the Ag-HZSM-5 and Ag-HZSM-11 zeolite molecular sieves obtained in step 2) with 5wt% lanthanum nitrate solution (La(NO ₃ ) ₃ 6H ₂ O) at room temperature for 4 hours, and pouring out the upper liquid Drying at 120°C and calcination in air at 550°C for 6 hours to obtain Ag-La-HZSM-5 and Ag-La-HZSM-11 zeolite molecular sieves jointly modified by silver and lanthanum.

4) Use orthoethyl silicate (TEOS) to impregnate the Ag-La-HZSM-5 and Ag-La-HZSM-11 zeolite molecular sieves obtained in step 3) respectively at room temperature for 24 hours, pour out the upper liquid, and then dry it at 120°C and dry it at 550°C. ℃ in air for 6 hours to obtain silver lanthanum and silanized HZSM-5 and HZSM-11 molecular sieve catalysts, the catalysts were named MTPP-08 and MTPP-09. X-ray fluorescence diffraction (XRF) analysis and determination of the loading of each element of the MTPP-08 and MTPP-09 catalysts, the loading of Ag on the MTPP-08 catalyst was 1.02wt%, the loading of La was 1.25wt%, and the silanized Si loading The loading amount was 2.32wt%; the Ag loading amount on the MTPP-09 catalyst was 1.13wt%, the La loading amount was 1.18wt%, and the silylated Si loading amount was 2.16wt%.

Example 2

p-xylene and propylene from methanol

According to the reaction process shown in Figure 2, the MTPP-08 catalyst prepared in Example 1 was loaded into the first reaction zone and the second reaction zone of the fixed reactor respectively (each reaction zone is 10 grams). The first reaction zone mainly carries out methanol aromatization reaction, and the reaction product enters the second reaction zone, the mass space velocity of methanol feed is 2h ^-1 , and the reaction temperature is 500°C. The ethylene ^- rich C ₂ -component in the distribution of the reaction product enters the second reaction zone together with methanol to react, wherein the ethylene/methanol (molar ratio) is 1/1, the reaction temperature is 400°C, and the second reaction zone carries out ethylene And methanol alkylation reaction.

Gas chromatography was used to analyze the mixed product composition of the first reaction zone and the second reaction zone on-line. The product distribution after removing the generated water is shown in Table 1, and the product distribution after removing the C ₂ ^- return component is shown in Table 2.

As can be seen from Table ₂ , after the C2 ^- component is removed from the total product of the first reaction zone and the second reaction zone, the selectivity of propylene in the product is 42.52wt%, the selectivity of p-xylene is 38.05wt%, and the selectivity of propylene and p-xylene The overall selectivity to xylenes was 80.57 wt%. The selectivity of p-xylene among xylene isomers was 98.98 wt%.

Table 1

*wt%, product weight percent composition, the same below.

Table 2

Example 3

p-xylene and propylene from methanol

According to the reaction process shown in Figure 3 or 4, the MTPP-08 and MTPP-09 catalysts prepared in Example 1 were loaded into the first reaction zone and the second reaction zone (each reaction zone is 10 grams) respectively. The methanol aromatization reaction is carried out in the first reaction zone, the methanol feeding mass space velocity is 2h ^-1 , and the reaction temperature is 500°C. The second reaction zone carries out the alkylation reaction of ethylene and methanol. According to the methanol conversion reaction product distribution in the comparative example, the ethylene ^{-rich C2-} _component and methanol enter the second reaction zone for reaction, wherein ethylene/methanol (molar ratio) is 1/1, and the reaction temperature is 400°C.

The gas chromatograph was used to analyze the mixed product composition of the first reaction zone and the second reaction zone online. The product distribution after removing the generated water is shown in Table 3, and the product distribution after removing the C ₂ ^-component is shown in Table 4.

As can be seen from Table 4, after the _C2 ^- component is removed from the total product of the first reaction zone and the second reaction zone, the selectivity of propylene in the product is 53.62wt%, the selectivity of p-xylene is 30.59wt%, and the selectivity of propylene and p-xylene The total selectivity to xylenes was 84.21 wt%. The selectivity of p-xylene among xylene isomers was 99.32 wt%.

table 3

Table 4

Comparative example 1

p-xylene from methanol with co-production of propylene, but no C ₂ ^- Further reactions of component returns

Take 10 grams of the MTPP-08 catalyst prepared in Example 1 and load it into a reactor for methanol conversion reaction. The methanol mass space velocity is 2h ^-1 and the reaction temperature is 500°C. The product composition was analyzed online by gas chromatography, and the distribution of the product after removing the generated water was shown in Table 5.

When the reactor is reacted with only methanol feed, the selectivity of propylene in the product is only 29.48wt%.

Table 5 methanol conversion reaction results

The present invention has been described in detail above, but the present invention is not limited to the specific embodiments described herein. Those skilled in the art understand that other changes and modifications can be made without departing from the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. a method for methyl alcohol and/or dimethyl ether system p-xylene and propylene, said method may further comprise the steps: a) The raw material containing methanol and/or dimethyl ether is contacted and reacted with the catalyst in the reaction system; the ethylene ^{-rich C2-} _component coming out of the reaction system is returned to the reaction system, and is mixed with the raw material in the reaction system Continue the reaction on the catalyst to generate propylene; b) C ₆ ⁺ components from the reaction system are separated to obtain the product p-xylene; and _c ) The C3 component coming out of the reaction system is separated to obtain the product propylene. 2. method according to claim 1, is characterized in that, described reaction system comprises first reaction zone and second reaction zone, and described method comprises the following steps: a) The raw material containing methanol and/or dimethyl ether first passes through the first reaction zone to contact catalyst I for aromatization reaction, and then enters the second reaction zone to contact catalyst II for alkylation reaction; from The ethylene ^- rich C ₂ -components from the second reaction zone are returned to the second reaction zone and reacted with methanol and/or dimethyl ether in the second reaction zone on the catalyst II alkylation reaction to produce propylene; b) the C ₆ ⁺ component from the second reaction zone is further separated to obtain the product p-xylene; and _c ) The C3 component coming out of the second reaction zone is further separated to obtain propylene. 3. The method according to claim 1, wherein the reaction system comprises a first reaction zone and a second reaction zone, and the method comprises the steps of: a) The raw material containing methanol and/or dimethyl ether is first contacted with the catalyst I through the first reaction zone to undergo an aromatization reaction to obtain a product A, which is rich in ethylene after being separated by a separation system The C ₂ ^-component returns to the second reaction zone, and carries out an alkylation reaction with methanol and/or dimethyl ether entering the second reaction zone on the catalyst II to obtain a product B; the The ethylene ^- rich C ₂ -components in product A and product B continue to return to the second reaction zone, and are mixed with methanol and/or dimethyl ether in the second reaction zone in the catalyst II Alkylation reaction to produce propylene; b) the C ₆ ⁺ components in the product A and product B are further separated to obtain the product p-xylene; and _c ) The C3 component in the product A and product B is further separated to obtain the product propylene. 4. The method according to claim 1, 2 or 3, characterized in that, said catalyst, said catalyst I and said catalyst II contain the same or different modified zeolite molecular sieve catalysts. 5. The method according to claim 4, characterized in that, the modified zeolite molecular sieve catalyst is modified by ZSM-5 and/or ZSM-11 zeolite molecular sieve through noble metal and rare earth metal modification and siloxane compound modification And get. 6. The method according to claim 5, characterized in that, the structural formula of the siloxane-based compound used for modification of the siloxane-based compound is as follows: Wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a C _1-10 alkyl group. 7. The method according to claim 1, wherein the reaction system comprises one reactor or a plurality of reactors connected in series and/or in parallel. 8. The method of claim 2, wherein the first reaction zone and the second reaction zone are in the same reactor. 9. The method according to claim 3, wherein the first reaction zone comprises a reactor or a plurality of reactors connected in series and/or in parallel; the second reaction zone comprises a reactor or a plurality of reactors connected in series and/or in parallel; and the first reaction zone and the second reaction zone are connected in series or in parallel. 10. The method according to claim 7, 8 or 9, characterized in that the reactor is one or more selected from fixed bed, fluidized bed and moving bed reactors.