JP7443474B2 - Catalyst for directly producing paraxylene from synthesis gas, its production method and use - Google Patents

Description

The present invention relates to a core-shell catalyst and a method for producing the same. The present invention further relates to a composite catalyst comprising the core-shell catalyst and a method for producing the same, and the use of the core-shell catalyst and composite catalyst of the present invention to directly produce paraxylene from synthesis gas.

Paraxylene is an important raw material for organic synthesis and is widely used in the fields of textiles and packaging materials. Paraxylene is mainly used in the production of terephthalic esters and terephthalic acid, and terephthalic acid is used as an intermediate for plastics and polyester fibers, and as a raw material for paints, dyes, and agricultural chemicals. Currently, the methods for producing paraxylene that are widely used in industry are the disproportionation of toluene and the transalkylation of nine-carbon aromatic hydrocarbons. In this method, the content of paraxylene in the product is limited by the thermodynamic balance, so that it is usually possible to obtain only a concentration of paraxylene of about 24 wt%. However, since the paraxylene market requires xylene with a paraxylene concentration of 60 wt% or more, it cannot fully meet the needs of industrial production such as the production of polyester materials. Furthermore, in order to obtain a high concentration of paraxylene and to increase the yield of paraxylene, it is necessary to undergo a series of post-treatments. In particular, the boiling point difference between the three isomers of xylene is small, and high-purity para-xylene cannot be obtained by ordinary distillation techniques, and an expensive adsorption separation process must be adopted, resulting in loss of raw materials and cost. leading to an increase in With the shortage of petroleum energy, the value of developing a new aromatic hydrocarbon synthesis process route is extremely high, not only from the market needs but also from the viewpoint of petroleum substitution.

As an energy conversion medium, syngas can convert coal, natural gas, and biomass into clean oil and is considered as one of the most potential oil alternatives. Therefore, composite catalysts combining metal catalysts and appropriate molecular sieves can effectively control the distribution of Fischer-Tropsch reaction products, and this research has made great progress in recent years. After successfully synthesizing and producing petroleum products with different carbon number ranges by Fischer-Tropsch reaction, many researchers have developed high-value-added chemicals, including low-carbon alkenes, low-carbon alcohols, etc., directly and highly selectively from syngas. We are focusing on manufacturing products based on Research has been reported on a one-shot method for producing aromatic hydrocarbons such as benzene, toluene, and xylene from synthesis gas, but the selectivity of para-xylene in the product is usually low, and industrialization has yet to be achieved. Not yet. This is because there is a major problem in that it is difficult to control the selectivity of the product. In addition, the catalyst easily deteriorates, making it difficult to maintain stability in catalyst performance.

In order to improve the selectivity of paraxylene production from synthesis gas using the one-shot method, the key is to manufacture and develop high-performance catalysts. Here, if a bifunctional composite catalyst consisting of a methanol synthesis catalyst and a molecular sieve is used, the catalyst performance will be improved. The reaction route includes a series of cascade reactions such as production of methanol by hydrogenation of synthesis gas, dehydration reaction by hydrogenation of methanol, aromatization reaction, and isomerization reaction of xylene. The route not only brings great advantages to the development of syngas conversion process and promotes the security of the country's energy strategy, but also becomes one of the solutions to the potential threat of global oil energy depletion. It has become. Therefore, increasing the selectivity of para-xylene and reducing the process complexity and cost are technical challenges that urgently need to be solved in the direct production of para-xylene from syngas.

Normally, direct production of aromatic hydrocarbons from synthesis gas requires two processes: first converting the synthesis gas to methanol or dimethyl ether, and then producing aromatic hydrocarbons (MTA) from methanol or dimethyl ether. Research shows that this is not the case. For example, a two-stage reactor used at the Shanxi Soot and Coal Chemistry Institute was equipped with two types of catalysts to convert synthesis gas from dimethyl ether to aromatic hydrocarbons (see CN101422743A). Synthesis gas aromatization catalysts include HNKF-5, aluminum phosphate molecular sieves, and Ga ₂ O ₃ :ZnO:BaO. The patent document discloses that after the synthesis gas passes through a mixed catalyst for methanol synthesis and methanol dehydration in the first stage, a mixed catalyst of an aromatization catalyst and a catalyst in the first stage is put into a second stage reactor. , aromatization is performed to finally obtain an aromatic hydrocarbon product.

The above two-step method has many steps when producing para-xylene from synthesis gas, the two-step reaction flow is long, energy consumption is large, and the method for producing the catalyst is complicated. The problem is that the selectivity is less than 30 wt% in the product of hydrocarbon compounds.

Lasa et al. (see Ind. Eng. Chem. Res., 1991, 30, 1448-1455) early characterized the properties of aromatic hydrocarbons produced from synthesis gas over a Cr-Zn/ZSM-5 catalyst. reported that the selectivity of aromatic hydrocarbons in hydrocarbon compounds reaches 70.8%, but does not mention the specific product distribution of aromatic hydrocarbons. Furthermore, the properties of aromatic hydrocarbons produced from synthesis gas with Cr-Zn/ZSM-5 composite catalysts (see Appl. Catal. A, 1995, 125, 81-98) have been reported, where 356 Under the reaction conditions of −410° C. and 3.6-4.5 MPa, the selectivity of aromatic hydrocarbons over hydrocarbons reached 75%, while the selectivity of xylene was less than 20%. In addition, Wang Desheng et al. (see Catalyst Chemistry Bulletin, 2002, 23(4), 333-335) have reported that Fe/MnO is a mixture of an Fe-based catalyst synthesized by the Fischer-Tropsch method and an aromatized molecular sieve. -Using Zn/ZSM-5 composite catalyst, syngas is converted into low carbon hydrocarbon intermediates through Fischer-Tropsch reaction and converted into aromatic hydrocarbons through molecular sieves, where the CO conversion rate is 270 Although the selectivity for aromatic hydrocarbons such as benzene and toluene was low, it reached 98.1% at ℃. Recently, the research team of Martin and Weibin Fan (see Chem, 2017, _{3 ,} 323-333) has developed mesoporous HZSM- By mixing with 5 molecular sieves, we have effectively realized the direct production of aromatic hydrocarbons using synthesis gas with alkenes as intermediates. Under the conditions of 340° C. and 2 MPa, up to 51 wt % of aromatic hydrocarbons were obtained from the hydrocarbon product, with light aromatic hydrocarbons being the main component. However, there is no mention of the selectivity of paraxylene in aromatic hydrocarbons. Based on the academic idea that developed the coupling reaction, the Wangno research team at Xiamen University (see Chem, 2017, 3, 334-347) has developed a combination of ZrO ₂ /H-ZSM-5 to Zn. By cleverly designing a mixture of functional catalysts, we were able to produce aromatic hydrocarbons from synthesis gas using a one-shot method with high selectivity and stability. In order to increase the content of light aromatic hydrocarbons BTX (benzene, toluene, xylene), the author reported that the outer surface of H-ZSM-5 molecular sieve was silanized to poison the Bronsted acid sites. The objective was achieved and finally the selectivity of BTX in aromatic hydrocarbon products was successfully increased. Although the proportion of BTX in aromatic hydrocarbons has increased to 60 wt%, the content of xylene and paraxylene is not mentioned.

All of the above-mentioned catalysts can obtain aromatic hydrocarbons from synthesis gas in a one-shot method, but the selectivity for para-xylene is always low and the isomerization reaction of xylene cannot be effectively suppressed.

The present invention provides a catalyst for directly producing paraxylene from synthesis gas with high selectivity, and its production method and use. The method for producing the catalyst is simple, the conversion rate of synthesis gas is high, and the selectivity for paraxylene is high, so it is expected to be used in industry.

One objective of the present invention is to provide a core-shell catalyst. When this catalyst is used in combination with a catalyst that converts synthesis gas into methanol through a catalytic reaction, not only the selectivity of para-xylene and the conversion rate of synthesis gas become high, but also the selectivity of para-xylene to xylene is high. Become.

Another object of the present invention is to provide a method for producing the core-shell catalyst.

A further object of the present invention is to provide a composite catalyst for directly producing paraxylene from synthesis gas, which comprises a catalyst for catalytically converting synthesis gas to methanol and a core-shell catalyst of the present invention. A catalyst containing a catalyst. When converting synthesis gas into hydrocarbons through a catalytic reaction, the composite catalyst not only increases the selectivity of para-xylene and the conversion rate of synthesis gas, but also increases the selectivity of para-xylene to xylene.

Another object of the present invention is to provide a method for producing the composite catalyst of the present invention.

The final objective of the present invention is to provide a core-shell catalyst of the present invention or a composite catalyst of the present invention for the direct production of paraxylene from synthesis gas. By using the core-shell catalyst or composite catalyst of the present invention as a catalyst for directly producing para-xylene from synthesis gas, not only the selectivity of para-xylene and the conversion rate of synthesis gas are increased, but also the selectivity of para-xylene to xylene is increased. It also becomes more expensive.

The technical solutions used to solve the above problems of the present invention are as follows.

1. The core is a hydrogen type ZSM-5 molecular sieve, and all or part of H in the hydrogen type ZSM-5 molecular sieve is Sn, Ga, Ti, Zn, Mg, Li, Ce, Co, La, Rh, Pd, Pt, Ni. , Cu, K, Ca, Ba, Fe, Mn and B, or any mixture thereof, and the shell is a carbon membrane, Silicalite. -1, MCM-41, SBA-15, KIT-6, MSU series, silica, graphene, carbon nanotubes, metal organic frameworks (MOF), graphite, activated carbon, metal oxide films (e.g. MgO, P ₂ O ₅ , A core-shell catalyst which is one or more selected from CaO).

2. The core is a hydrogen type ZSM-5 molecular sieve, a modified ZSM-5 molecular sieve in which part or all of the H in the hydrogen type ZSM-5 molecular sieve is replaced with Zn, or any mixture thereof, and/or the shell is one or more selected from silica film, Silicalite-1, metal oxide film (e.g. MgO, P ₂ O ₅ , CaO), MCM-41, SBA-15, KIT-6, preferably Silicalite-1. 1 and particularly preferably modified with element M, the element M is 0.5 to 15 wt% of the total weight of the M-ZSM-5 molecular sieve, preferably 1 to 10 wt%. %, particularly preferably from 1 to 5 wt.%.

3. The weight ratio of core to shell is 100:1 to 1:100, preferably 10:1 to 1:10, more preferably 5:1 to 1:5, particularly preferably 5:1 to 1. The core-shell catalyst according to item 1 or 2, which is: 1.

4.
1) Hydrogen type ZSM-5 molecular sieve, all or part of H in the hydrogen type ZSM-5 molecular sieve is Sn, Ga, Ti, Zn, Mg, Li, Ce, Co, La, Rh, Pd, Pt, Ni Modified ZSM-5 molecular sieve substituted with one or more elements M selected from , Cu, Na, K, Ca, Ba, Fe, Mn and B, or any mixture thereof, exhibiting particulate form a step of providing a core, and 2) a carbon film, Silicalite-1, MCM-41, SBA-15, KIT-6, MSU series, silica, graphene, carbon nanotube, organometallic structure on the surface of the core exhibiting a particle shape; coating one or more materials selected from (MOF), graphite, activated carbon, metal oxide films ₍ e.g. MgO, _P2O5 , CaO),
A method for producing a core-shell catalyst according to any one of items 1 to 3.

5.
A composite catalyst for directly producing para-xylene from synthesis gas, comprising: A) catalyst A for catalytically converting synthesis gas to methanol; and B) catalyst B for catalytically reacting to produce xylene. There it is,
The catalyst B is the core-shell catalyst according to any one of items 1 to 3,
Preferably, the composite catalyst is in the form of a mixture of catalyst A and catalyst B, with catalyst A physically or chemically encapsulating catalyst B, or catalyst B physically or chemically encapsulating catalyst A. do.

6. Catalyst A includes a first metal component and a second metal component, or consists of a first metal component and a second metal component, and the first metal component is selected from Cr, Fe, Zr, In, Ga, Co, and Cu. the second metal component is selected from Zn, Na, Al, Ag, Ce, K, Mn, Pd, Ni, La, and V. An element, an oxide thereof, a composite oxide thereof, or any mixture thereof, preferably an element in which the first metal component is selected from Cr, Co, Cu, and Zr, an oxide thereof, a composite oxide thereof, or any mixture thereof. and/or the second metal component is an element selected from Zn and Al, an oxide thereof, a composite oxide thereof, or an arbitrary mixture thereof, particularly preferably catalyst A is ZnO-Cr. 6. The composite catalyst according to item ₅ , which is _2O3 .

7. The molar ratio of the metal elements of the first metal component and the second metal component in catalyst A is 1000:1 to 1:100, preferably 100:1 to 1:50, more preferably 10:1 to 1. :10, particularly preferably 3:1 to 1:3.

8. The weight ratio of catalyst A and catalyst B is 1:99 to 99:1, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, particularly preferably 50:50. The composite catalyst according to any one of items 5 to 7, wherein the ratio is 75:25.

9.
1) A step of producing catalyst A powder and catalyst B powder, respectively;
2a) mixing catalyst A powder and catalyst B powder with an arbitrarily selected adhesive and then forming into a composite catalyst;
2b) A step of respectively molding the powder of catalyst A and the powder of catalyst B to obtain a molded body of catalyst A and a molded body of catalyst B, and then mixing these;
2c) Physically or chemically encapsulating catalyst A as a core and catalyst B as a shell;
2d) A step of physically or chemically encapsulating catalyst B as a core and catalyst A as a shell,
A method for producing a composite catalyst according to any one of items 5 to 8.

10. Catalyst A is produced by one or more selected from sequential impregnation method, co-impregnation method, urea method and coprecipitation method, preferably sequential impregnation method, co-impregnation method, urea method and/or coprecipitation method. In the calcination process of catalyst A by
The firing atmosphere is air, and/or
The firing temperature is 200 to 700°C, preferably 400 to 600°C, and/or
The firing time is 3 to 8 hours, preferably 4 to 6 hours.
The method described in paragraph 9.

11. The core-shell catalyst according to any one of paragraphs 1 to 3, the core-shell catalyst produced by the method according to paragraph 4, the composite catalyst according to any one of paragraphs 5 to 8, or any one of paragraphs 9 to 10. Use of the composite catalyst produced by the method described in 1 as a catalyst for directly producing paraxylene from synthesis gas.

12. The molar ratio of hydrogen to carbon monoxide in the synthesis gas is 0.1 to 5, preferably 1 to 4, the reaction pressure is 1 to 10 MPa, preferably 2 to 8 MPa, and the reaction temperature is 150 to 600° C., preferably 250 to 500° C., and/or the space velocity is 200 to 8000 h ⁻¹ , preferably 500 to 5000 h ⁻¹ .
Uses as described in Section 11.

13. Before the synthesis gas is vented and reacted, the composite catalyst is first pre-treated for reduction,
Preferably, the process conditions for the reduction pretreatment are as follows:
The reducing gas is pure hydrogen,
The pretreatment temperature is 300 to 700°C, preferably 400 to 600°C,
The pretreatment pressure is 0.1 to 1 MPa, preferably 0.1 to 0.5 MPa,
The volumetric hourly space velocity of the pretreatment hydrogen gas is 500 to 8000 h ^-1 , preferably 1000 to 4000 h ^-1 , and/or the pretreatment reduction time is 2 to 10 hours, preferably 4 to 6 hours. ,
Uses as described in Section 12.

1 is a SEM photograph of Zn/ZSM-5 and Zn/ZSM-5@S1 molecular sieve according to Example 2, a of FIG. 1 is a SEM photograph of Zn/ZSM-5 molecular sieve, and b of FIG. /ZSM-5@S1 SEM photo of molecular sieve. 1 is a SEM photograph of Zn/ZSM-5 and Zn/ZSM-5@S1 molecular sieve according to Example 2, a of FIG. 1 is a SEM photograph of Zn/ZSM-5 molecular sieve, and b of FIG. /ZSM-5@S1 SEM photo of molecular sieve. 2 is a STEM photograph of the Zn/ZSM-5@S1 molecular sieve produced in Example 2 and a scan image of its corresponding elemental EDS surface. 2 is a STEM photograph of the Zn/ZSM-5@S1 molecular sieve produced in Example 2 and a scan image of its corresponding elemental EDS surface. 2 is a STEM photograph of the Zn/ZSM-5@S1 molecular sieve produced in Example 2 and a scan image of its corresponding elemental EDS surface. 2 is a STEM photograph of the Zn/ZSM-5@S1 molecular sieve produced in Example 2 and a scan image of its corresponding elemental EDS surface. 2 is a STEM photograph of the Zn/ZSM-5@S1 molecular sieve produced in Example 2 and a scan image of its corresponding elemental EDS surface.

A first embodiment of the present invention provides a core-shell catalyst, in which the core is a hydrogen-type ZSM-5 molecular sieve, in which all or part of H in the hydrogen-type ZSM-5 molecular sieve is Sn, Ga. , Ti, Zn, Mg, Li, Ce, Co, La, Rh, Pd, Pt, Ni, Cu, K, Ca, Ba, Fe, Mn and B. Modified ZSM-5 molecular sieve or any mixture thereof, the shell is carbon membrane, Silicalite-1, MCM-41, SBA-15, KIT-6, MSU series, silica, graphene, carbon nanotube, organometallic structure The material is one or more selected from MOF, graphite, activated carbon, and metal oxide films (eg, MgO, P ₂ O ₅ , CaO).

The core-shell catalyst of the present invention has a core-shell structure. The core is a hydrogen type ZSM-5 molecular sieve (hereinafter sometimes referred to as HZSM-5), in which all or part of H in the hydrogen type ZSM-5 molecular sieve is Sn, Ga, Ti, Zn, Mg, Li, Modified ZSM-5 molecular sieve substituted with one or more elements M selected from Ce, Co, La, Rh, Pd, Pt, Ni, Cu, Na, K, Ca, Ba, Fe, Mn and B (hereinafter sometimes referred to as M/ZSM-5 molecular sieve) or any mixture thereof. These molecular sieves are collectively referred to as ZSM-5 molecular sieves in the present invention. ZSM-5 molecular sieve can catalyze the conversion of hydrocarbon compounds produced by a one-shot synthesis gas process into hydrocarbons. The inventors have demonstrated that when these catalytically active components are coated with the present invention, the selectivity for paraxylene can be clearly increased when producing hydrocarbons from synthesis gas compared to when the surface is not coated. In particular, it has been found that the selectivity of para-xylene to xylene can be significantly increased and a high CO conversion rate can be maintained. Furthermore, the core-shell catalyst of the present invention can clearly increase the selectivity of para-xylene even when compared with a mixed catalyst in which a core material and a shell material are physically mixed under the same conditions. The selectivity of CO can be significantly increased, and a high CO conversion rate can be maintained.

As core components, hydrogen type ZSM-5 molecular sieve and M/ZSM-5 molecular sieve can be purchased on the market, and various methods such as hydrothermal synthesis method, impregnation method, ion exchange method, vapor phase growth method, liquid phase growth method, etc. It can also be manufactured by conventional methods in the art. For example, HZSM-5 molecular sieve and Na/ZSM-5 can be produced by a hydrothermal synthesis method, and M/ZSM-5 molecular sieve can be produced from HZSM-5 molecular sieve and Na/ZSM-5 by an ion exchange method.

The hydrothermal synthesis method of HZSM-5 zeolite molecular sieve is given as an example. Silicon source (TEOS, ethyl orthosilicate), aluminum _source (Al( _NO3 ) _39H2O ), organic templating agent (TPAOH, tetrapropylammonium hydroxide), ethanol and deionized water in molar ratio (2TEOS: _xAl2 O ₃ :0.68TPAOH:8EtOH:120H ₂ O, x=0.002-0.2) and stirred at room temperature for 4-6 hours to obtain a sol.Then, the well-stirred sol was mixed with polyethylene tetrafluoride. After transferring to a crystallization vessel, it is sealed and crystallized at a temperature of 160-200°C and a rotation speed of 2-5 rpm for 24-72 hours. Once the crystallization is complete, it is cooled to room temperature, the resulting product is washed until the pH of the filtrate is 7-8, dried overnight, and then heated in a muffle furnace at a heating rate of 1-3°C/min. When the temperature is raised to 550-650° C. and calcined for 4-8 hours, ZSM-5 molecular sieve is obtained, which is HZSM-5. SiO ₂ /Al ₂ O ₃ in the ZSM-5 molecular sieve is 10 to 1000.

To produce M/ZSM-5 molecular sieve, when element M is a metal element, it can be produced using HZSM-5 as a raw material by ion exchange method, impregnation method, vapor phase growth method, liquid phase growth method, etc. When M is a nonmetallic element B, an M/ZSM-5 molecular sieve can be produced using HZSM-5 as a raw material by an impregnation method, a vapor phase growth method, a liquid phase growth method, or the like.

For example, we will take the production of Zn/ZSM-5 molecular sieve by ion exchange method. For example, ion exchange is performed by adding 1.5 g of HZSM-5 molecular sieve to a 1 mol/L zinc nitrate aqueous solution and stirring constantly at 80 to 100° C. for 10 to 15 hours. After the ion exchange is completed, it is cooled to room temperature, the resulting product is washed until the pH of the filtrate is 7-8, dried overnight, and then calcined in a muffle furnace at 500 °C for 4-6 hours, resulting in Zn. /ZSM-5 molecular sieve is obtained.

In an optimal embodiment of the present invention, in the M/ZSM-5 molecular sieve modified with element M, element M is 0.5 to 15 wt% of the total weight of the M/ZSM-5 molecular sieve, preferably The content is 1 to 10 wt%, particularly preferably 1 to 5 wt%.

In the HZSM-5 molecular sieve or M/ZSM-5 molecular sieve modified with M of the present invention, the molar ratio of Si to Al is usually 10 to 1000, preferably 20 to 800. The particle size of these molecular sieves is usually 0.01 to 20 μm, preferably 0.1 to 15 μm.

The shell of the core-shell catalyst of the present invention is carbon membrane, Silicalite-1, MCM-41, SBA-15, KIT-6, MSU series (pure silica molecular sieve), silica, graphene, carbon nanotube, organometallic framework (MOF). ) (for example, ZIF-8, ZIF-11), graphite, activated carbon, and metal oxide films (for example, MgO, P ₂ O ₅ , CaO). These materials coat the outer surface of the core to form a shell. These shell materials themselves do not have any activity in producing dimethylbenzene by aromatizing hydrocarbons, but by covering the core of ZSM-5 molecular sieve, the outer surface of ZSM-5 was exposed. By influencing the acidic sites and coating or treating these exposed acidic sites, side reactions can be reduced and ultimately the selectivity for the target product paraxylene can be increased. The shell material is preferably one or more selected from silica film, Silicalite-1, metal oxide film (for example, MgO, P ₂ O ₅ , CaO), MCM-41, SBA-15, and KIT-6. Silicalite-1 is particularly preferred.

The amount of shell to be used is not particularly limited, as long as it can cover the core. In one embodiment of the core-shell catalyst of the present invention, the weight ratio of core to shell is from 100:1 to 1:100, preferably from 10:1 to 1:10, more preferably from 5:1 to The ratio is 1:5, particularly preferably 5:1 to 1:1.

According to a second embodiment of the present invention, there is provided a method for producing the core-shell catalyst of the present invention, the method comprising:

1) Hydrogen type ZSM-5 molecular sieve, all or part of H in the hydrogen type ZSM-5 molecular sieve is Sn, Ga, Ti, Zn, Mg, Li, Ce, Co, La, Rh, Pd, Pt, Ni Modified ZSM-5 molecular sieve substituted with one or more elements M selected from , Cu, Na, K, Ca, Ba, Fe, Mn and B, or any mixture thereof, exhibiting particulate form a step of providing a core, and 2) a carbon film, Silicalite-1, MCM-41, SBA-15, KIT-6, MSU series, silica, graphene, carbon nanotube, organometallic structure on the surface of the core exhibiting a particle shape; coating one or more materials selected from (MOF), graphite, activated carbon, metal oxide films (eg, MgO, P ₂ O ₅ , CaO).

The core material and shell material of the core-shell catalyst of the present invention are both conventional ones. To provide the core in step 1), if the core material itself has particles of an appropriate size, it is used as is, but if the core material is large in size, it is pulverized before being used in step 2). In step 2), the core particles are coated. It is common knowledge in the art to coat core particles with different shell materials. Examples of the coating method include a hydrothermal synthesis method, a vapor growth method, an impregnation method, a sputtering method, and a Stover method, and any conventional method can be selected depending on the properties of the coating material. For example, a hydrothermal synthesis method can be used to coat a molecular sieve shell material, a vapor deposition method can be used to coat a carbon film, graphene, and carbon nanotubes, and a vapor deposition method can be used to coat a metal oxide. Impregnation and sputtering methods can be used to coat the silica, and Stover's method can be used to coat the silica.

An example will be given in which a Zn/ZSM-5@Silicalite-1 core-shell catalyst is obtained by coating Zn/ZSM-5 with Silicalite-1 by a hydrothermal synthesis method. A mixture was prepared by combining silicon source (TEOS), organic templating agent (TPAOH), ethanol and deionized water in molar ratio ( _1.00SiO2 :0.06TPAOH:16.0EtOH: _240H2O ) and kept at room temperature. After stirring for 4 to 6 hours, a Silicalite-1 molecular sieve precursor solution is obtained. After pulverizing the Zn/ZSM-5 zeolite molecular sieve produced as described above, it was transferred together with the obtained Silicalite-1 molecular sieve precursor solution to a polytetrafluoroethylene crystal kettle, sealed, and heated at a temperature of 180°C. Crystallize for 24 to 72 hours at a rotation speed of 2 to 5 rpm. Once the crystallization is completed, it is cooled to room temperature, the resulting product is washed with deionized water until the pH of the filtrate is 7-8, dried overnight, and then heated in a muffle oven at 1°C to 3°C/min. When the temperature is raised to 550 to 650°C at a heating rate of Let 1 be the shell.

There are two steps to produce aromatic hydrocarbons from synthesis gas in a one-shot process: one is to convert the synthesis gas to methanol, and the other is to further react the methanol to produce the final product. is the step to obtain aromatic hydrocarbons such as para-xylene. The core-shell catalyst of the present invention is extremely effective in increasing the selectivity of para-xylene in the second step, and it not only dramatically increases the selectivity of para-xylene, but especially the selectivity of para-xylene to xylene. However, a high CO conversion rate can be maintained.

Therefore, according to a third embodiment of the present invention, there is provided a composite catalyst for directly producing para-xylene from synthesis gas, the composite catalyst comprising:
A) a catalyst A for catalytically converting synthesis gas into methanol; and B) a catalyst B for producing xylene as a catalyst, and the catalyst B is a core-shell catalyst of the present invention.

Catalyst A may be any catalyst that can promote the conversion of synthesis gas to methanol. In a preferred embodiment of the invention, catalyst A comprises a first metal component and a second metal component, or consists of a first metal component and a second metal component, and the first metal component is Cr, Fe, Zr, In , Ga, Co, Cu, an oxide thereof, a composite oxide thereof, or any mixture thereof, and the second metal component is Zn, Na, Al, Ag, Ce, K, Mn, Pd, It is an element selected from Ni, La, and V, an oxide thereof, a composite oxide thereof, or an arbitrary mixture thereof. Preferably, the first metal component is an element selected from Cr, Fe, Co, Zr, Cu, an oxide thereof, a composite oxide thereof, or any mixture thereof, and/or the second metal component is Zn, It is an element selected from Al, its oxide, its composite oxide, or any mixture thereof, and particularly preferably catalyst A is ZnO--Cr ₂ O ₃ .

Catalyst A can be purchased commercially or prepared by any conventional method, such as, for example, sequential impregnation, co-impregnation, urea and coprecipitation, preferably coprecipitation. When the catalyst A containing the first metal component and the second metal component is manufactured by the above method, a precursor mixture containing the first metal component and the second metal component is finally fired. The firing atmosphere is air, and/or the firing temperature is 200 to 700°C, preferably 400 to 600°C, and/or the firing time is 3 to 8 hours, preferably 4 to 6 hours. It is beneficial to be

An example will be given in which ZnO--Cr ₂ O ₃ is produced as catalyst A by a coprecipitation method. In order to produce the catalyst, the nitrate precursors of chromium and zinc are usually prepared into a mixed nitrate aqueous solution of 1 mol/L at the ratio of chromium and zinc required for catalyst A using deionized water. Co-precipitate the solution by dropping it into a beaker with a 1 mol/L ammonium carbonate aqueous solution (for example, other precipitants such as sodium carbonate, sodium hydroxide, and ammonium hydroxide can also be used), and continue stirring during coprecipitation. By controlling the relative addition rates of the two types of solutions, the precipitation temperature is controlled at 50-90° C. and the pH is controlled at 6-8. After the addition is complete, stirring is continued and the resulting precipitate is aged at 50-90° C. for 60-240 minutes. The aged precipitate was filtered, washed with deionized water, and the washed product was placed in an oven to dry at 80-120°C for 8-12 hours, and then in a muffle oven at 350-550°C for 3-6 hours. After calcination, a ZnO--Cr ₂ O ₃ catalyst is obtained.

In an optimal embodiment of the composite catalyst of the present invention, the molar ratio of the metal elements of the first metal component and the second metal component in catalyst A is 1000:1 to 1:100, preferably 100:1 to 1: 50, more preferably 10:1 to 1:10, particularly preferably 3:1 to 1:3.

In other embodiments, the weight ratio of catalyst A to catalyst B is 1:99 to 99:1, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, Particularly preferred is 50:50 to 75:25.

According to the present invention, the composite catalyst is in the form of a mixture of catalyst A and catalyst B, where catalyst A physically or chemically encapsulates catalyst B, or catalyst B physically or chemically encapsulates catalyst A. It may also be encapsulated.

According to a fourth embodiment of the present invention, there is provided a method for producing a composite catalyst of the present invention, which method includes the steps of: 1) producing powder of catalyst A and powder of catalyst B, respectively;
2a) mixing catalyst A powder and catalyst B powder with an arbitrarily selected adhesive and then forming into a composite catalyst;
2b) A step of respectively molding the powder of catalyst A and the powder of catalyst B to obtain a molded body of catalyst A and a molded body of catalyst B, and then mixing these;
2c) Physically or chemically encapsulating catalyst A as a core and catalyst B as a shell;
2d) A step of physically or chemically encapsulating catalyst B as a core and catalyst A as a shell.

In the present invention, the technique for combining catalyst A and catalyst B is conventional. Catalyst A and Catalyst B are usually produced as powders. In step 2a), catalyst A powder and catalyst B powder are mixed with an arbitrarily selected adhesive and formed into a composite catalyst. Examples of the adhesive include water, alumina, and silica. By mixing the powder of catalyst A and the powder of catalyst B with an arbitrarily selected adhesive, the resulting powder mixture can be molded into a form such as a tablet, pellet, or granule. In step 2c), catalyst A is physically or chemically encapsulated as a core and catalyst B as a shell. In step 2d), catalyst B is physically or chemically encapsulated as a core and catalyst A as a shell. The conventional method is to form it into capsules.

For example, 1. Production of A@B catalyst by physical coating method in which catalyst B encapsulates catalyst A: First, the surface of particulate catalyst A having a certain size is impregnated with an adhesive liquid, and the excess adhesive is immediately removed. After removing the catalyst, place the wet catalyst A into the round-bottomed flask containing the powdered catalyst B, and move the round-bottomed flask quickly so that the entire surface of the catalyst A is coated with the catalyst B. Rotate. This process should be repeated 2-3 times. Finally, the catalyst is dried overnight and then calcined in a muffle furnace at 350-550° C. for 3-6 hours to obtain the A@B catalyst, where catalyst A is the core and catalyst B is the shell. When producing a B@A catalyst in which catalyst A physically encapsulates catalyst B, catalyst A and catalyst B in the above method may be replaced.

For example, 2. Production of A@B catalyst in which catalyst B encapsulates catalyst A by a chemical method: First, particulate catalyst A having a certain size is hydrothermally synthesized with ZSM-5 synthesis liquid, and specific operational steps are performed. can refer to the method for manufacturing the ZSM-5 molecular sieve. After the completion of hydrothermal synthesis, the obtained A@ZSM-5 catalyst is recovered. The A@ZSM-5 catalyst and Silicalite-1 molecular sieve are then hydrothermally synthesized together. Finally, after the hydrothermal synthesis is completed, the catalyst is washed with deionized water until the pH of the catalyst is 7, dried overnight, and then calcined in a muffle furnace at 500-600°C for 4-6 hours to produce the A@B catalyst. is obtained, where catalyst A is the core and catalyst B is the shell. When producing a B@A catalyst in which catalyst A chemically encapsulates catalyst B, first, catalyst B is produced by a hydrothermal synthesis method, and the specific operation steps are as follows: Refer to the method for producing sieves, and then the particulate catalyst B and the precursor solution of catalyst A are hydrothermally synthesized together and crystallized at a temperature of 220° C. and a rotation speed of 2-5 rpm for 24-72 hours. Once the crystallization has finished, it is cooled to room temperature, the resulting product is washed with deionized water until the pH of the filtrate is 7-8, dried overnight, and then heated in a muffle oven at 1°-3°/min. When the temperature is raised to 550 to 650° C. and calcined for 4 to 8 hours, a B@A catalyst is obtained, in which catalyst B is used as the core and catalyst A is used as the shell.

According to a final embodiment of the invention, the core-shell catalyst of the invention, the core-shell catalyst produced by the process of the invention, the composite catalyst of the invention or the composite catalyst produced by the process of the invention, is prepared from synthesis gas in parallel. Use as a catalyst for the direct production of xylene is provided. By using these catalysts of the present invention, not only the selectivity of para-xylene and conversion of syngas is high, but also the selectivity of para-xylene to xylene is high while maintaining high conversion of syngas. can.

Before catalytically reacting synthesis gas to produce paraxylene using the composite catalyst of the present invention, it is desirable to pre-reduce the composite catalyst. Desirable conditions for the reduction pretreatment include that the reducing gas is pure hydrogen, the pretreatment temperature is 300 to 700°C, preferably 400 to 600°C, and the pretreatment pressure is 0.1 to 1 MPa, preferably is 0.1 to 0.5 MPa, the volumetric hourly space velocity of the pretreatment hydrogen gas is 500 to 8000 h ^-1 , preferably 1000 to 4000 h ^-1 , and/or the pretreatment reduction time is 2 to 10 time, preferably 4 to 6 hours. After the reduction pretreatment, paraxylene is produced by bubbling synthesis gas and reacting. The molar ratio of hydrogen to carbon monoxide in the synthesis gas used is from 0.1 to 5, preferably from 1 to 4. The reaction pressure is 1 to 10 MPa, preferably 2 to 8 MPa. The reaction temperature is 150-600°C, preferably 250-500°C. The space velocity is between 200 and 8000 h ⁻¹ , preferably between 500 and 5000 h ⁻¹ .

When the composite catalyst of the present invention is employed to convert synthesis gas, the conversion rate of synthesis gas is 55% or more, the selectivity of para-xylene to xylene isomers is 70% or more, and the selection of para-xylene is rate is significantly higher under the same conditions. By using the composite catalyst of the present invention, synthesis gas can be converted to para-xylene in a one-shot method without going through a multistage reactor that uses a mixture of multiple types of different catalysts, and the reaction procedure is simple and easy to operate. . Syngas conversion processes carried out with the catalyst of the present invention can achieve higher para-xylene selectivity while maintaining high CO conversion.

[Comparative example 1]
a. Preparation of Cr/Zn Catalyst 23.6 _g of Cr(NO ₃ ) _{3.9H 2} O and 9.0 g of Zn(NO ₃ ) 2.6H ₂ O were dissolved in 100 ml of deionized water. The resulting mixed nitrate aqueous solution was mixed with a small amount of deionized water along with a 1 mol/L (NH ₄ ) ₂ CO ₃ aqueous solution (9.6 g of (NH ₄ ) ₂ CO ₃ dissolved in 100 ml of deionized water). It was dropped into a beaker containing water and co-precipitated. During coprecipitation, the temperature was maintained at 70° C. and the pH was maintained at about 7 by continuing stirring and controlling the relative flow rates of the two types of solutions. After the coprecipitation was completed, the mixture was allowed to stand at 70° C. for 3 hours for aging. The precipitate was filtered and then washed with deionized water. The washed precipitate was baked in an oven at 120°C for 12 hours, and further in a muffle furnace at 400°C for 5 hours. A methanol synthesis catalyst was obtained as a Cr/Zn catalyst, in which the molar ratio of the elements chromium and zinc was 2:1.

b. Production of HZSM-5 molecular sieve Silicon source (TEOS), aluminum source (Al(NO ₃ ) _{3.9H 2} O), organic template agent (TPAOH), ethanol and deionized water were mixed in a molar ratio (2TEOS:0.02Al _A mixture was prepared by blending ( _2O3 :0.68TPAOH:8EtOH: _120H2O ) and stirred at room temperature for 6 hours to obtain a sol. The well-stirred sol was then transferred to a polytetrafluoroethylene crystallization vessel, sealed, and crystallized at a temperature of 180° C. and a rotation speed of 2 rpm for 24 hours. Once the crystallization is complete, it is cooled to room temperature and the resulting product is washed with deionized water until the pH of the filtrate is 7, dried overnight and then heated in a muffle furnace at a heating rate of 1 °C/min. When the temperature was raised to 550° C. and calcined for 6 hours, a ZSM-5 molecular sieve was obtained as HZSM-5. The molar ratio of Si to Al in the HZSM-5 molecular sieve was 46.

c. Production of Bifunctional Catalyst The obtained Cr/Zn catalyst and HZSM-5 molecular sieve powder were physically mixed, ground for 10 minutes, and further compression molded to produce a bifunctional catalyst (Cr/Zn -HZSM-5) was obtained, in which the weight ratio of Cr/Zn catalyst to HZSM-5 molecular sieve was 2:1.

d. Catalyst Tests 0.5 g of Cr/Zn-HZSM-5 catalyst was packed in fixed bed form in a high pressure fixed bed reactor and continuously bubbled with synthesis gas with a volume ratio of _H2 to CO of 2.1. The reaction pressure was controlled at 5 MPa, the space velocity of the synthesis gas was controlled at 1200 h ^-1 , and the reaction temperature was controlled at 400°C. After reacting for 4 hours, the reaction products and raw material gas were analyzed online by gas chromatography, and the reaction characteristics are shown in Table 1.

[Comparative example 2]
a. Manufacture of Cr/Zn catalyst When the "manufacture of Cr/Zn catalyst" of Comparative Example 1 was repeated, a Cr/Zn catalyst was obtained.

b. Manufacture of Zn/ZSM-5 molecular sieve By repeating "Manufacture of HZSM-5 molecular sieve" in Comparative Example 1, HZSM-5 molecular sieve was obtained. Next, 1.5 g of HZSM-5 molecular sieve was added to a 1 mol/L zinc nitrate aqueous solution, and stirring was continued at 80° C. for 15 hours to perform ion exchange. After the ion exchange is completed, it is cooled to room temperature, the obtained product is washed until the pH of the filtrate is 7-8, dried overnight, and then calcined in a muffle furnace at 500 °C for 4 hours to produce Zn/ZSM. -5 molecular sieve was obtained. Based on the total weight of the Zn/ZSM-5 molecular sieve, the Zn content was 1 wt%.

c. Production of Bifunctional Catalyst When the "Production of Bifunctional Catalyst" of Comparative Example 1 was repeated except that Zn/ZSM-5 molecular sieve was used instead of HZSM-5 molecular sieve, bifunctional catalyst was produced by mechanical stirring method. A catalyst (referred to as Cr/Zn-Zn/ZSM-5 catalyst) was obtained, where the weight ratio of Cr/Zn catalyst and Zn/ZSM-5 molecular sieve was 2:1.

d. Catalyst Test The "catalyst test" of Comparative Example 1 was repeated except that a Cr/Zn-Zn/ZSM-5 catalyst was used instead of the Cr/Zn-HZSM-5 catalyst. The reaction results are shown in Table 1.

[Example 1]
a. Manufacture of Cr/Zn catalyst When the "manufacture of Cr/Zn catalyst" of Comparative Example 1 was repeated, a Cr/Zn catalyst was obtained.

b. Production of HZSM-5@S1 Catalyst By repeating "Production of HZSM-5 molecular sieve" in Comparative Example 1, HZSM-5 molecular sieve was obtained.

A mixture was prepared by combining silicon source (TEOS), organic templating agent (TPAOH), ethanol and deionized water in molar ratio ( _1.0SiO2 :0.06TPAOH:16.0EtOH: _240H2O ) and kept at room temperature. After stirring for 4 hours, a Silicalite-1 molecular sieve precursor solution was obtained. After crushing the HZSM-5 molecular sieve produced as above, it was transferred together with the obtained Silicalite-1 molecular sieve precursor solution to a polytetrafluoroethylene crystallization vessel, sealed, and heated at 2 rpm at a temperature of 180°C. Crystallization was allowed for 24 hours at rotating speed. Once the crystallization is complete, it is cooled to room temperature, the resulting product is washed with deionized water until the pH of the filtrate is 7, dried overnight, and then heated in a muffle furnace at a heating rate of 1 °C/min. After raising the temperature to 550° C. and calcination for 4 hours, HZSM-5@Silicalite-1 molecular sieve (referred to as HZSM-5@S1 catalyst) is obtained, where HZSM-5 molecular sieve is the core and Silicalite-1 molecular sieve is As a shell, the weight ratio of HZSM-5 molecular sieve to Silicalite-1 molecular sieve was 3:1.

c. Production of Bifunctional Catalyst When the "Production of Bifunctional Catalyst" of Comparative Example 1 was repeated except that the HZSM-5@S1 catalyst was used instead of the HZSM-5 molecular sieve, the bifunctional catalyst by the mechanical stirring method was (referred to as Cr/Zn-HZSM-5@S1 catalyst) was obtained, where the weight ratio of Cr/Zn catalyst and HZSM-5@S1 catalyst was 2:1.

d. Catalyst Test The "catalyst test" of Comparative Example 1 was repeated except that Cr/Zn-HZSM-5@S1 catalyst was used instead of Cr/Zn-HZSM-5 catalyst. The reaction results are shown in Table 1.

[Example 2]
a. Manufacture of Cr/Zn catalyst When the "manufacture of Cr/Zn catalyst" of Comparative Example 1 was repeated, a Cr/Zn catalyst was obtained.

b. Manufacture of Zn/ZSM-5@S1 molecular sieve When the "manufacture of Zn/ZSM-5 molecular sieve" of Comparative Example 2 was repeated, Zn/ZSM-5 molecular sieve was obtained. Then, a silicon source (TEOS), an organic template agent (TPAOH), ethanol and deionized water are combined in a molar ratio ( _1.0SiO2 :0.06TPAOH:16.0EtOH: _240H2O ) to prepare a mixture; After stirring at room temperature for 4 hours, a Silicalite-1 molecular sieve precursor solution was obtained. After pulverizing the Zn/ZSM-5 molecular sieve produced as above, it was transferred together with the obtained Silicalite-1 molecular sieve precursor solution to a polytetrafluoroethylene crystallization vessel, sealed, and heated at a temperature of 180°C. Crystallization was carried out for 24 hours at a rotation speed of 2 rpm. Once the crystallization is complete, it is cooled to room temperature, the resulting product is washed with deionized water until the pH of the filtrate is 7, dried overnight, and then heated in a muffle furnace at a heating rate of 1 °C/min. After raising the temperature to 550°C and calcination for 4 hours, a Zn/ZSM-5@Silicalite-1 molecular sieve (Zn/ZSM-5@S1 catalyst) was obtained, in which Zn/ZSM-5 molecular sieve was used as the core and Silicalite Using the -1 molecular sieve as a shell, the weight ratio of the Zn/ZSM-5 molecular sieve and the Silicalite-1 molecular sieve was 3:1.

FIG. 1 is a SEM photograph of Zn/ZSM-5 and Zn/ZSM-5@S1 according to this example, a of FIG. 1 is a SEM photograph of Zn/ZSM-5, and b of FIG. /ZSM-5@S1 SEM photo. From Figure 1, before coating with Silicalite-1 molecular sieve, the size of Zn/ZSM-5 molecular sieve is 0.5-1 μm, and after coating with Silicalite-1 molecular sieve, the obtained Zn/ZSM- The size of the 5@S1 molecular sieve was found to be 1.5-2 μm. This revealed that Silicalite-1 molecular sieve grows in situ on the core of Zn/ZSM-5 molecular sieve to form a shell.

In order to more visually demonstrate that the Zn/ZSM-5@S1 molecular sieve has a core-shell structure, it was demonstrated using STEM and EDS surface scan images.

FIG. 2 is a STEM diagram of the Zn/ZSM-5@S1 molecular sieve manufactured in Example 2 and a scan image of its corresponding elemental EDS surface. Figure 2b is a diagram of Si element, Figure 2c is a diagram of Al element, Figure 2d is a diagram of O element, and Figure 2e is a diagram of Zn element. 2, f in FIG. 2 is a mixture diagram of each element. From Figure 2, most of the Zn is supported on the upper surface of the ZSM-5 molecular sieve, and the Zn/ZSM-5@S1 molecular sieve has Zn/ZSM-5 as the core and Silicalite-1 as the shell. It turned out to be a molecular sieve with a core-shell structure.

That is, in the Zn/ZSM-5@S1 molecular sieve, Zn/ZSM-5 is the core, and the Silicalite-1 molecular sieve is the shell covering the core.

c. Production of Bifunctional Catalyst When the “Production of Bifunctional Catalyst” of Comparative Example 1 was repeated except that the Zn/ZSM-5@S1 catalyst was used instead of the HZSM-5 molecular sieve, the bifunctional catalyst was produced by the mechanical stirring method. A catalyst (referred to as Cr/Zn-Zn/ZSM-5@S1) was obtained, where the weight ratio of Cr/Zn catalyst and Zn/ZSM-5@S1 catalyst was 2:1.

d. Catalyst Test The "catalyst test" of Comparative Example 1 was repeated except that Cr/Zn-Zn/ZSM-5@S1 was used instead of the Cr/Zn-HZSM-5 catalyst. The reaction results are shown in Table 1.

[Comparative example 3]
The "catalyst test" of Comparative Example 1 was repeated using only a Cr/Zn catalyst and no molecular sieve. The reaction results are shown in Table 1.

[Comparative example 4]
a. Manufacture of Cr/Zn catalyst When the "manufacture of Cr/Zn catalyst" of Comparative Example 1 was repeated, a Cr/Zn catalyst was obtained.

b. Production of β molecular sieve Silicon source (SiO ₂ ), aluminum source (aluminum isopropoxide), organic template agent (TEAOH), NaOH and deionized water were mixed in a molar ratio (1SiO ₂ :0.023Al ₂ O ₃ :0.0425TEAOH). :0.049NaOH: _6.8H2O ) to prepare a mixture and stirred at room temperature for 6 hours to obtain a sol. The stirred sol was then transferred to a polytetrafluoroethylene crystallization vessel, sealed, and crystallized at a temperature of 150° C. and a rotation speed of 2 rpm for 72 hours. Once the crystallization is complete, it is cooled to room temperature and the resulting product is washed with deionized water until the pH of the filtrate is 7, dried overnight and then heated in a muffle furnace at a heating rate of 1 °C/min. When the temperature was raised to 550° C. and calcined for 6 hours, a β molecular sieve was obtained. The molar ratio of Si to Al in the β molecular sieve was 20.

c. Production of Bifunctional Catalyst When the "Production of Bifunctional Catalyst" of Comparative Example 1 was repeated except that β molecular sieve was used instead of HZSM-5 molecular sieve, a bifunctional catalyst (Cr/ Zn-β catalyst) was obtained, and the weight ratio of Cr/Zn catalyst to β molecular sieve was 2:1.

d. Catalyst Test The "catalyst test" of Comparative Example 1 was repeated, except that a Cr/Zn-β catalyst was used instead of the Cr/Zn-HZSM-5 catalyst. The reaction results are shown in Table 1.

[Comparative example 5]
b. Production of HZSM-5 & S1 Physically Mixed Catalyst The "Production of HZSM-5@S1 Catalyst" in Example 1 was repeated, but when HZSM-5 molecular sieve and Silicalite-1 molecular sieve were physically mixed, a bifunctional catalyst was obtained. (referred to as HZSM-5 & S1 catalyst) was obtained, where the weight ratio of HZSM-5 molecular sieve to Silicalite-1 molecular sieve was 3:1.

c. Preparation of Bifunctional Catalyst When the “Preparation of Bifunctional Catalyst” of Comparative Example 1 was repeated except that HZSM-5&S1 catalyst was used instead of HZSM-5 molecular sieve, the bifunctional catalyst (Cr /Zn-HZSM-5&S1 physical mixed catalyst) was obtained, where the weight ratio of Cr/Zn catalyst and HZSM-5&S1 catalyst was 2:1.

d. Catalyst Test The "Catalyst Test" of Example 1 was repeated except that Cr/Zn-HZSM-5 & S1 catalyst was used instead of Cr/Zn-HZSM-5 catalyst. The reaction results are shown in Table 1.

[Comparative example 6]
By repeating "Production of Cr/Zn catalyst" and "Production of Zn/ZSM-5@S1 molecular sieve" in Example 2, a Cr/Zn catalyst and a Zn/ZSM-5@S1 catalyst were obtained, respectively.

The “Catalyst Test” of Example 2 was repeated, but without mixing the Cr/Zn and Zn/ZSM-5@S1 catalysts, these two catalysts were each placed in fixed bed form in two of the high pressure fixed bed reactors. It was fixed in a stage separated in the middle by quartz wool, where along the gas flow direction, the Cr/Zn catalyst part was in the front and the Zn/ZSM-5@S1 catalyst part was in the rear. Ta. The reaction results are shown in Table 1.

[Example 3]
a. Preparation of Fe/Zn/Cu catalyst 9.0 g Fe(NO ₃ ) ₃ ·9H ₂ O, 3.8 g Zn(NO ₃ ) ₂ ·6H ₂ O and 1.3 g Cu(NO ₃ ) ₂ ·3H. When _2O was dissolved in 200 mL of deionized water, a mixed aqueous solution containing iron, zinc, and copper was obtained. 10.0 g of Na ₂ CO ₃ was dissolved in 100 mL of deionized water to obtain an aqueous sodium carbonate solution. These two types of solutions were simultaneously dropped into a beaker containing a small amount of deionized water to cause coprecipitation. During the coprecipitation, the temperature was maintained at 85° C. and the pH between 8 and 8.5 by continuous stirring and controlling the relative flow rates of the two solutions. After the precipitation was completed, the mixture was allowed to stand at 85° C. for 2 hours for aging. The precipitate was filtered and then washed with deionized water. The washed precipitate was calcined in an oven at 120°C for 12 hours and then in a muffle furnace at 320°C for 5 hours to obtain a methanol synthesis catalyst (referred to as Fe/Zn/Cu catalyst). The molar ratio of metal elements in the catalyst was Fe/Zn/Cu=55:32:13.

b. Production of Zn/ZSM-5@S1 molecular sieve By repeating "Production of Zn/ZSM-5@S1 molecular sieve" in Example 2, Zn/ZSM-5@S1 molecular sieve was obtained.

c. Production of bifunctional catalyst The obtained Fe/Zn/Cu catalyst and Zn/ZSM-5@S1 molecular sieve powder were physically mixed, pulverized for 10 minutes, and further compression molded to produce a bifunctional catalyst by mechanical stirring method. A catalyst (referred to as Fe/Zn/Cu-Zn/ZSM-5@S1) was obtained, where the weight ratio of Fe/Zn/Cu catalyst and Zn/ZSM-5@S1 molecular sieve was 2:1. .

d. Catalyst Test The "Catalyst Test" of Example 2 was repeated, except that Fe/Zn/Cu-Zn/ZSM-5@S1 catalyst was used instead of Cr/Zn-Zn/ZSM-5@S1 catalyst. The reaction results are shown in Table 1.

[Example 4]
a. Preparation of Zr/Zn Catalyst 2.0 g of ZrO ₂ was impregnated in 1 mol/L zinc nitrate aqueous solution, dried overnight at a temperature of 120°C, and then calcined in a muffle furnace at 400°C for 3 hours, resulting in ZrO ₂ − A ZnO catalyst (referred to as Zr/Zn catalyst) was obtained, in which the molar ratio of the elements Zr and Zn was 13.5:1.

b. Production of Zn/ZSM-5@S1 molecular sieve By repeating "Production of Zn/ZSM-5@S1 molecular sieve" in Example 2, Zn/ZSM-5@S1 molecular sieve was obtained.

c. Preparation of Bifunctional Catalyst The obtained Zr/Zn catalyst and Zn/ZSM-5@S1 molecular sieve powder were physically mixed, ground for 10 minutes, and further compression molded to produce a bifunctional catalyst by mechanical stirring method. (referred to as Zr/Zn-Zn/ZSM-5@S1) was obtained, where the weight ratio of Zr/Zn catalyst and Zn/ZSM-5@S1 molecular sieve was 2:1.

d. Catalyst Test The "Catalyst Test" of Example 2 was repeated, except that Zr/Zn-Zn/ZSM-5@S1 catalyst was used instead of Cr/Zn-Zn/ZSM-5@S1 catalyst. The reaction results are shown in Table 1.

[Example 5]
a. Preparation of Cr/Zn/Al catalyst 23.6 g Cr(NO ₃ ) ₃ ·9H ₂ O, 9.0 g Zn(NO ₃ ) ₂ ·6H ₂ O 9.0 g and 5.4 g Al(NO ₃ ) _{3.9H 2} O was dissolved in 100 ml of deionized water. Then, by performing a coprecipitation method in the same manner as in "Production of Cr/Zn catalyst" in Comparative Example 1, a Cr/Zn/Al catalyst was obtained, where the molar ratio of the elements of Cr, Zn, and Al was 4:2: It was 1.

b. Production of Zn/ZSM-5@S1 molecular sieve By repeating "Production of Zn/ZSM-5@S1 molecular sieve" in Example 2, Zn/ZSM-5@S1 molecular sieve was obtained.

c. Production of bifunctional catalyst The obtained Cr/Zn/Al catalyst and Zn/ZSM-5@S1 molecular sieve powder were physically mixed, pulverized for 10 minutes, and further compression molded to produce bifunctional catalyst by mechanical stirring method. A catalyst (referred to as Cr/Zn/Al-Zn/ZSM-5@S1) was obtained, where the weight ratio of Cr/Zn/Al catalyst and Zn/ZSM-5@S1 molecular sieve was 3:1. .

d. Catalyst Test The "Catalyst Test" of Example 2 was repeated, except that a Cr/Zn/Al-Zn/ZSM-5@S1 catalyst was used instead of the Cr/Zn-Zn/ZSM-5@S1 catalyst. The reaction results are shown in Table 1.

[Example 6]
a. Manufacture of Cr/Zn catalyst When the "manufacture of Cr/Zn catalyst" of Comparative Example 1 was repeated, a Cr/Zn catalyst was obtained.

b. Manufacture of Ag/ZSM-5@S1 molecular sieve By repeating "Manufacture of HZSM-5 molecular sieve" in Comparative Example 1, HZSM-5 molecular sieve was obtained. Next, 1.5 g of HZSM-5 molecular sieve was added to a 1 mol/L silver nitrate aqueous solution, and stirring was continued at 80° C. for 15 hours to perform ion exchange. After the ion exchange is completed, it is cooled to room temperature, the resulting product is washed until the pH of the filtrate is 7-8, dried overnight, and then calcined in a muffle furnace at 500 °C for 4 hours to produce Ag/ZSM. -5 molecular sieve was obtained. Based on the total weight of the Ag/ZSM-5 molecular sieve, the content of Ag was 1 wt%.

Example 1 "Preparation of HZSM-5@S1 Catalyst" was repeated except that Ag/ZSM-5 was used instead of HZSM-5 molecular sieve. Ag/ZSM-5@Silicalite-1 molecular sieve (referred to as Ag/ZSM-5@S1 catalyst) is obtained, where Ag/ZSM-5 molecular sieve is the core and Silicalite-1 molecular sieve is the shell. The weight ratio of ZSM-5 molecular sieve to Silicalite-1 molecular sieve was 3:1.

c. Production of Bifunctional Catalyst The obtained Cr/Zn catalyst and Ag/ZSM-5@S1 molecular sieve powder were physically mixed, ground for 10 minutes, and further compression molded to produce a bifunctional catalyst by mechanical stirring method. (referred to as Cr/Zn-Ag/ZSM-5@S1) was obtained, where the weight ratio of Cr/Zn catalyst and Ag/ZSM-5@S1 molecular sieve was 1:1.

d. Catalyst Test The "Catalyst Test" of Example 2 was repeated, except that Cr/Zn-Ag/ZSM-5@S1 catalyst was used instead of Cr/Zn-Zn/ZSM-5@S1 catalyst. The reaction results are shown in Table 1.

[Example 7]
a. Manufacture of Cr/Zn catalyst When the "manufacture of Cr/Zn catalyst" of Comparative Example 1 was repeated, a Cr/Zn catalyst was obtained.

b. Manufacture of HZSM-5@MgO catalyst By repeating the "manufacture of HZSM-5 molecular sieve" in Comparative Example 1, HZSM-5 molecular sieve was obtained. Impregnating 2.0 g of HZSM-5 molecular sieve in 1 mol/L magnesium nitrate aqueous solution, then drying at a temperature of 120 °C overnight, and then calcining at 500 °C for 4 hours in a muffle furnace yields HZSM-5@MgO. A molecular sieve (referred to as HZSM-5@MgO) is obtained, where HZSM-5 molecular sieve is the core and MgO is the shell. Based on the total weight of the HZSM-5@MgO molecular sieve, the content of MgO was 1 wt%.

c. Preparation of Bifunctional Catalyst The obtained Cr/Zn catalyst and HZSM-5@MgO catalyst powder were physically mixed, ground for 10 minutes, and compression molded to produce a bifunctional catalyst (Cr/Zn -HZSM-5@MgO) was obtained, where the weight ratio of Cr/Zn catalyst to HZSM-5@MgO catalyst was 2:1.

d. Catalyst test 0.5 g of Cr/Zn-HZSM-5@MgO catalyst was packed in fixed bed form in a high pressure fixed bed reactor and continuously bubbled with synthesis gas with a volume ratio of _H2 to CO of 2.1. The reaction pressure was controlled at 3 MPa, the space velocity of the synthesis gas at 1200 h ^-1 , and the reaction temperature at 400°C. After reacting for 4 hours, the reaction products and raw material gas were analyzed online by gas chromatography, and the reaction characteristics are shown in Table 1.

[Example 8]
a. Manufacture of Cr/Zn catalyst When the "manufacture of Cr/Zn catalyst" of Comparative Example 1 was repeated, a Cr/Zn catalyst was obtained.

b. Manufacture of HZSM-5@SiO ₂ molecular sieve By repeating the "manufacture of HZSM-5 molecular sieve" in Comparative Example 1, HZSM-5 molecular sieve was obtained. A SiO ₂ film was prepared by the Stover method, 1.0 g of HZSM-5 molecular sieve, 5-10 μL of TEOS, and 15 ml of ethanol were placed in a 20 ml beaker, and 2.3 ml of 25 wt% ammonia solution was added dropwise. Stirred for 2 hours. The product obtained after the completion of the reaction was washed with ethanol until the pH of the filtrate was 7, dried overnight, and then calcined in a muffle furnace at 500 °C for 4 hours to obtain HZSM-5@SiO ₂ catalyst (HZSM- 5@SiO ₂ ) was obtained. This process was repeated 2-3 times to uniformly coat the SiO ₂ film. Finally, based on the total weight of the HZSM-5@SiO ₂ molecular sieve, the content of SiO ₂ was 1 wt%.

c. Preparation of Bifunctional Catalyst The obtained Cr/Zn catalyst and HZSM-5@ _SiO2 catalyst powder were physically mixed, ground for 10 minutes, and further compression molded to produce a bifunctional catalyst (Cr /Zn-HZSM-5@SiO ₂ ) was obtained, where the weight ratio of Cr/Zn catalyst to HZSM-5@SiO ₂ catalyst was 2:1.

d. Catalyst Test The "Catalyst Test" of Example 2 was repeated, except that a Cr/Zn-HZSM-5@SiO ₂ catalyst was used instead of the Cr/Zn-Zn/ZSM-5@S1 catalyst. The reaction results are shown in Table 1.

[Comparative example 7]
The "catalyst test" of Example 3 was repeated using only a Fe/Zn/Cu catalyst and no molecular sieve. The reaction results are shown in Table 1.

[Comparative example 8]
The "catalyst test" of Example 4 was repeated using only a Zr/Zn catalyst and no molecular sieve. The reaction results are shown in Table 1.

Notes MeOH: Methanol DME: Dimethyl ether _C2 - _C5 : _C2 - _C5 hydrocarbons Extra: All other products MX: Meta-xylene OX: Ortho-xylene PX: Para-xylene PX/X: Selection of para-xylene over xylene rate

Claims (35)

A composite catalyst for directly producing para-xylene from synthesis gas, comprising: A) catalyst A for catalytically converting synthesis gas to methanol; and B) catalyst B for catalytically reacting to produce xylene. There it is,
In the catalyst B, the core is a hydrogen type ZSM-5 molecular sieve, and the shell is a carbon membrane, Silicalite-1, MCM-41, SBA-15, KIT-6, MSU series, silica, graphene, carbon nanotube, graphite, one or more selected from activated carbon and a metal oxide film, the metal oxide film being CaO, a core-shell catalyst ;
A composite catalyst , wherein the weight ratio of the catalyst A and the catalyst B is 1:99 to 99:1 . The composite catalyst according to claim 1, wherein the shell is one or more selected from silica membrane, Silicalite-1, metal oxide membrane, MCM-41, SBA-15, and KIT-6. The composite catalyst according to claim 1 or 2, wherein the weight ratio of the core to the shell is 100:1 to 1:100. The composite catalyst according to claim 3, wherein the weight ratio of the core to the shell is 10:1 to 1:10. The composite catalyst according to claim 4, wherein the weight ratio of the core to the shell is 5:1 to 1:5. The composite catalyst according to claim 5, wherein the weight ratio of core to shell is 5:1 to 1:1. The composite catalyst is in the form of a mixture of catalyst A and catalyst B, and catalyst A physically or chemically encapsulates catalyst B, or catalyst B physically or chemically encapsulates catalyst A. , the composite catalyst according to any one of claims 1 to 6. Catalyst A includes a first metal component and a second metal component, or consists of a first metal component and a second metal component, and the first metal component is selected from Cr, Fe, Zr, In, Ga, Co, and Cu. the second metal component is selected from Zn, Na, Al, Ag, Ce, K, Mn, Pd, Ni, La, and V. The composite catalyst according to any one of claims 1 to 7, which is an element, an oxide thereof, a composite oxide thereof, or any mixture thereof. The first metal component is an element selected from Cr, Co, Cu, and Zr, an oxide thereof, a composite oxide thereof, or any mixture thereof, and/or the second metal component is selected from Zn and Al. The composite catalyst according to claim 8, which is an element, an oxide thereof, a composite oxide thereof, or any mixture thereof. The composite catalyst according to claim 8 or 9, wherein catalyst A is ZnO-Cr ₂ O ₃ . The composite catalyst according to any one of claims 8 to 10, wherein the molar ratio of the metal elements of the first metal component and the second metal component in catalyst A is 1000:1 to 1:100. The composite catalyst according to claim 11, wherein the molar ratio of the metal elements of the first metal component and the second metal component in catalyst A is 100:1 to 1:50. The composite catalyst according to claim 12, wherein the molar ratio of the metal elements of the first metal component and the second metal component in catalyst A is 10:1 to 1:10. The composite catalyst according to claim 13, wherein the molar ratio of the metal elements of the first metal component and the second metal component in catalyst A is 3:1 to 1:3. The composite catalyst according to claim 14 , wherein the weight ratio of catalyst A and catalyst B is 20:80 to 80:20. The composite catalyst according to claim 15 , wherein the weight ratio of catalyst A and catalyst B is 30:70 to 70:30. The composite catalyst according to claim 16 , wherein the weight ratio of catalyst A and catalyst B is 50:50 to 75:25. 1) A step of producing catalyst A powder and catalyst B powder, respectively;
2a) mixing the powder of catalyst A and the powder of catalyst B with an arbitrarily selected adhesive and then forming it into a composite catalyst, or 2b) forming the powder of catalyst A and the powder of catalyst B, respectively, 2c) A step of physically or chemically encapsulating catalyst A as a core and catalyst B as a shell after obtaining a catalyst A molded body and a catalyst B molded body, or 2d) A step of physically or chemically encapsulating catalyst B as a core and catalyst A as a shell,
A method for producing a composite catalyst according to any one of claims 1 to 17 . 19. The method according to claim 18 , wherein catalyst A is produced by one or more selected from a sequential impregnation method, a co-impregnation method, a urea method, and a coprecipitation method. In the step of firing catalyst A by the sequential impregnation method, co-impregnation method, urea method and/or coprecipitation method, the process conditions are that the calcination atmosphere is air and/or the calcination temperature is 200 to 700°C, and 20. The method according to claim 19 , wherein the firing time is 3 to 8 hours. The method according to claim 20 , wherein the calcination temperature is 400 to 600°C. The method according to claim 20 or 21 , wherein the firing time is 4 to 6 hours. Use of the composite catalyst according to any one of claims 1 to 17 or the composite catalyst produced by the production method according to any one of claims 18 to 22 as a catalyst for directly producing paraxylene from synthesis gas. . The molar ratio of hydrogen to carbon monoxide in the synthesis gas is 0.1 to 5, the reaction pressure is 1 to 10 MPa, the reaction temperature is 150 to 600 ° C., and/or the space velocity is 200 to 8000 h ^- 24. The use according to claim 23 , which is ¹ . 25. Use according to claim 24 , wherein the molar ratio of hydrogen to carbon monoxide in the synthesis gas is from 1 to 4. The use according to claim 24 or 25 , wherein the reaction pressure is 2 to 8 MPa. Use according to any of claims 24 to 26 , wherein the reaction temperature is 250 to 500°C. Use according to any of claims 24 to 27 , wherein the space velocity is between 500 and 5000 h ^-1 . Use according to any of claims 24 to 28 , wherein the composite catalyst is first pre-reduced before the synthesis gas is bubbled through and reacted. The process conditions for the reduction pretreatment are that the reducing gas is pure hydrogen, the pretreatment temperature is 300 to 700°C, the pretreatment pressure is 0.1 to 1 MPa, and the volumetric hourly space velocity of the pretreated hydrogen gas is 500°C. 30. The use according to claim 29 ^, wherein the pretreatment reduction time is between 2 and 10 hours. Use according to claim 30 , wherein the pretreatment temperature is 400-600°C. The use according to claim 30 or 31 , wherein the pretreatment pressure is 0.1 to 0.5 MPa. The use according to any of claims 30 to 32 , wherein the pretreated hydrogen gas has a volumetric hourly space velocity of 1000 to 4000 h ⁻¹ . Use according to any of claims 30 to 33 , wherein the pretreatment reduction time is 4 to 6 hours. A) a step of catalytically reacting synthesis gas to convert it into methanol using a composite catalyst containing catalyst A and catalyst B; and B) a step of producing xylene using a composite catalyst containing catalyst A and catalyst B. A method for directly producing paraxylene from synthesis gas, wherein the catalyst A is a catalyst that promotes the conversion of synthesis gas to methanol, and the catalyst B has a core of hydrogen type ZSM-5 molecular sieve and a shell of One or more selected from carbon film, Silicalite-1, MCM-41, SBA-15, KIT-6, MSU series, silica, graphene, carbon nanotube, graphite, activated carbon, and metal oxide film, and the metal The oxide film is a core-shell catalyst of CaO, and the weight ratio of the catalyst A and the catalyst B is 1:99 to 99:1 .