CN109939669B - A kind of alkali-modified composite catalyst and method for producing ethylene by hydrogenation of carbon monoxide - Google Patents

Abstract

The invention belongs to the direct conversion of carbon monoxide hydrogenation to prepare ethylene, and in particular relates to an alkali-modified composite catalyst and a method for preparing ethylene by hydrogenation of carbon monoxide. , the catalyst is a composite catalyst, which is composed of component I and component II in a mechanical mixing manner, the active component of component I is a metal oxide, and component II is a molecular sieve with a MOR structure modified by an organic base; The weight ratio of the active ingredient in Part I to Component II is 0.1-20. The reaction process has high product yield and selectivity, the C2-C3 olefin selectivity is as high as 83-90%, the hydrocarbon products containing more than 4 C atoms are lower than 7%, and the by-product methane selectivity is extremely low (< 5%), and the ethylene selectivity and space-time yield are significantly improved, and the selectivity reaches 75-85%, which has a good application prospect.

Description

A kind of alkali-modified composite catalyst and method for producing ethylene by hydrogenation of carbon monoxide

technical field

The invention belongs to carbon monoxide hydrogenation to produce low-carbon olefin high-value chemicals, and in particular relates to an alkali-modified composite catalyst and a method for producing ethylene by carbon monoxide hydrogenation.

Background technique

Ethylene is a very important basic chemical raw material and one of the largest chemical products in the world. The ethylene industry is the core of the petrochemical industry and occupies an important position in the national economy. Lower olefins refer to olefins with carbon number less than or equal to 4. Low-carbon olefins represented by ethylene and propylene are very important basic organic chemical raw materials. With the rapid growth of my country's economy, my country's ethylene industry has developed rapidly and occupies an important position in the world ethylene market. For a long time, the low-carbon olefins market has been in short supply. At present, the production of ethylene mainly adopts the petrochemical route of cracking naphtha and light diesel oil or the technology of ethane cracking. Due to the long-term dependence of my country's oil on imports, my country's energy security is at great risk, and there is an urgent need to develop ethylene production that does not depend on petroleum. technology. Convert coal, natural gas, biomass and other renewable materials into a mixture of carbon monoxide and hydrogen, that is, syngas. The ratio of carbon monoxide and hydrogen in the syngas varies with the raw materials; then these syngas are used as raw materials, and the carbon monoxide is adjusted by adjusting the ratio of carbon monoxide and hydrogen. After the ratio of carbon monoxide and hydrogen reaches an appropriate value, carbon monoxide and hydrogen can be directly prepared by a Fischer-Tropsch synthesis reaction under the action of a suitable catalyst to produce light olefins with carbon atoms less than or equal to 4, so that olefins can be produced in one step. The route provides an alternative to naphtha cracking technology to produce ethylene. This process does not need to further prepare olefins from synthesis gas through methanol or dimethyl ether as in the indirect process, which simplifies the process flow and greatly reduces investment.

The direct production of light olefins by Fischer-Tropsch synthesis has always been one of the research hotspots in the direct production of olefins from synthesis gas. In the patent CN1083415A published by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, the iron-manganese catalyst system supported by IIA group alkali metal oxides such as MgO or high silica zeolite molecular sieve (or phosphorus aluminum zeolite) is supported by strong alkali K or Cs ions. When the reaction pressure of synthesis gas to low-carbon olefins is 1.0-5.0Mpa and the reaction temperature is 300-400℃, higher activity (CO conversion rate of 90%) and selectivity (low-carbon olefin selectivity of 66%) can be obtained. . In the patent ZL03109585.2 filed by Beijing University of Chemical Technology, Fe/activated carbon catalysts with manganese, copper, zinc silicon, potassium, etc. as auxiliary agents are prepared by vacuum impregnation method for the reaction of synthesis gas to low-carbon olefins. Under the conditions, the CO conversion rate is 96%, and the selectivity of light olefins in hydrocarbons is 68%. The catalyst reported above uses metallic iron or iron carbide as the active component, the reaction follows the chain growth reaction mechanism on the metal surface, and the selectivity of the product low-carbon olefin is low, especially the selectivity of a single product such as ethylene is lower than 30%. In 2016, researchers Sun Yuhan and Zhong Liangshu of Shanghai Institutes for Advanced Study reported a preferentially exposed [101] and [020] manganese-assisted cobalt carbide-based catalyst, which achieved 31.8% CO conversion and 60.8% low-carbon olefins. Selectivity and methane selectivity of 5%. But the ethylene single selectivity is less than 20%. The team of Bao Xinhe and Pan Xiulian from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences reported the composite bifunctional catalyst of alumina-supported ZnCr ₂ O ₄ oxide and hierarchically porous SAPO-34 molecular sieve (Jiao et al., Science 351(2016) 1065-1068) , the selectivity of light olefins is 80% when the CO conversion rate is 17%, but the selectivity of ethylene is lower than 30%. In their patent application 201610600945.6, the use of a bifunctional catalyst containing oxygen cavities combined with MOR molecular sieves for one-step synthesis gas to olefins reaction increases the selectivity of ethylene to 30-75%, but the number of carbon atoms in the by-product exceeds 3 has more hydrocarbons, which affects the application of this technology. The present invention further reduces the selectivity of methane by-products by adjusting the acidity of the MOR molecular sieve, and further reduces the selectivity of hydrocarbon products above C4.

SUMMARY OF THE INVENTION

The technology of the present invention solves the problem: overcomes the deficiencies of the prior art, provides an alkali-modified catalyst and a method for producing ethylene by hydrogenation of carbon monoxide, and the invented catalyst can catalyze the hydrogenation of carbon monoxide and directly convert it into low-carbon olefins with high selectivity, and The selectivity of C2-C3 olefins is as high as 83-90%, the selectivity of single product ethylene can be as high as 75-85%, the selectivity of methane is less than 5%, and the selectivity of C4 and above hydrocarbons is less than 7%.

The technical scheme of the present invention is: a catalyst, the catalyst comprises component I and component II, the component I and component II are combined together by mechanical mixing, and the active component of component I is a metal oxide , component II is a molecular sieve with a MOR topology; the molecular sieve with a MOR topology is modified with an organic base; the modification treatment is to disperse the organic base into the 12-ring channel of the molecular sieve with the MOR topology. B acid site; the organic base is a heterocyclic compound; preferably a heteroaryl group; further preferably a heteroaryl group containing 1-2 heteroatoms; more preferably a 5- or 6-membered heteroaryl group containing 1-2 N atoms .

The MOR topology structure of the present invention is a kind of orthorhombic crystal system, and has a one-dimensional channel structure with parallel elliptical straight through channels, and contains 8 ring pockets and 12 ring one-dimensional channels.

The mechanical mixing of the present invention can be compounded by one or more of mechanical stirring, ball milling, shaking table mixing and mechanical grinding.

The molecular sieve with the MOR topology is modified by a heterocyclic compound, which can prevent organic base molecules from entering the 8-ring channel, but selectively occupy the B acid site of the 12-ring. The use of meta-para-substituted molecules can avoid the problem of weak contact between organic bases and B acid caused by steric hindrance effect and weak adsorption.

The heterocyclic compound can be furan, thiophene, pyrrole, thiazole, imidazole, pyridine, pyrazine, pyrimidine, pyridazine, indole, quinoline, pteridine, acridine. The heterocyclic compound may have one or two or more substituents of methyl, ethyl, amino and nitro. Meta and/or para substitutions are preferred.

The metal oxides are MnO _x , Mn _a Cr _(1-a) O _x , Mn _a Al _(1-a) O _x , Mn _a Zr _(1-a) O _x , Mn _a In _{(1-a) )} O _x , ZnO _x , Zn _a Cr _(1-a) O _x , Zn _a Al _(1-a) O _x , Zn _a Ga _(1-a) O _x , Zn _a In _(1-a) O _x , CeO _x , Co _a Al _(1-a) O _x , Fe _a Al _(1-a) O _x , GaO _x , BiO _x , InO _x , In _a Al _b Mn _(1-ab) O _x , In _a One or more of Ga _b Mn _(1-ab) O _x ;

The specific surface area of the MnO _x , ZnO _x , CeO _x , GaO _x , BiO _x , and InO _x is 1-100 m ² /g; preferably the specific surface area is 50-100 m ² /g;

The Mn _a Cr _(1-a) O _x , Mn _a Al _(1-a) O _x , Mn _a Zr _(1-a) O _x , Mn _a In _(1-a) O _x , Zn _a Cr _{( 1-a)} O _x , Zn _a Al _(1-a) O _x , Zn _a Ga _(1-a) O _x , Zn _a In _(1-a) O _x , Co _a Al _(1-a) O _x The specific surface area of , _FeaAl (1- _{a )} Ox, _InaAlbMn (1- _{ab )} Ox, _{InaGabMn (1-ab) Ox is 5-150m} ² /g. The preferred specific surface area is 50-150 m ² /g;

The value range of the x is 0.7～3.7, the value range of a is 0～1; the value range of a+b is 0～1;

The a,b,(1-a),(1-a-b),x described in the present invention only represent the relative ratio of the chemical composition of the elements in the metal oxide, and all metal oxides with the same ratio are regarded as the same metal oxide.

The weight ratio of the active ingredient in component I to component II is 0.1-20, preferably 0.3-8, and the reaction can be carried out effectively only by the coordination of multiple components, and too much or too little of one of them will be unfavorable for the reaction.

A dispersant is also added to the component I, the metal oxide is dispersed in the dispersant, and the dispersant is Al ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , ZrO ₂ , TiO ₂ , Ga ₂ O ₃ , One or more of activated carbon, graphene, and carbon nanotubes. In the component I, the content of the dispersant is 0.05-90 wt%, and the rest are metal oxides.

The framework element composition of the molecular sieve with MOR topology can be Si-Al-O, Ga-Si-O, Ga-Si-Al-O, Ti-Si-O, Ti-Al-Si-O, Ca- One or more of Al-O and Ca-Si-Al-O.

The organic base modification in the present invention refers to the use of organic base molecules to occupy the B acid sites in the annular pores of the MOR molecular sieve 12, which can be fully occupied or partially occupied. The B acid sites in the occupied 12-ring channel are 50-100%

The method for dispersing the organic base into the B acid site in the annular channel of the MOR molecular sieve 12, all known methods that can achieve this purpose can meet the requirements. The present invention takes the vacuum dehydration adsorption method as an example. Control the temperature on the vacuum line to dehydrate and degas the molecular sieve sample at a temperature of 350-500 °C, a pressure of 1Pa- ^10-5 Pa, and a time of 4h-24h, and further expose the degassed molecular sieve to an organic alkali atmosphere of 10Pa-100kPa or In the atmosphere of organic base diluted with inert gas, the adsorption temperature is controlled from room temperature to 300°C, and the organic base-modified molecular sieve is obtained after purging with inorganic gas at 200-330°C for 30min-12h.

A method for directly converting synthesis gas to ethylene involves using synthesis gas as a reaction raw material, the synthesis gas may also contain a certain amount of carbon dioxide, and the conversion reaction is carried out on a fixed bed or a moving bed to generate ethylene with high selectivity. The catalyst is the above-mentioned catalyst.

The pressure of the synthesis gas is 0.5-10MPa, preferably 1-8MPa, more preferably 2-8MPa; the reaction temperature is 300-600°C, preferably 300-450°C; the space velocity is 300-10000h ^-1 , preferably 500- 9000h ^-1 , more preferably 500-6000h ^-1 , higher space-time yield can be obtained.

The H ₂ /CO molar ratio of the synthesis gas for the reaction is 0.2-3.5, preferably 0.3-2.5, so that higher space-time yield and selectivity can be obtained. The syngas may also contain _CO2 , wherein the volume concentration of _CO2 in the syngas is 0.1-50%.

The catalyst of the present invention is used for the one-step direct conversion of synthesis gas to produce ethylene or C2-C3 olefins, wherein the selectivity of C2-C3 olefins is as high as 83-90%, the selectivity of ethylene reaches 75-85%, and the by-product methane is also The selectivity is extremely low (<5%), and the selectivity for C4 and above hydrocarbons is less than 7%.

The present invention has the following advantages:

(1) The present invention is different from the traditional methanol-to-light olefin technology (referred to as MTO for short), and realizes that one step directly converts synthesis gas to ethylene.

(2) The single product selectivity of ethylene in the product of the present invention is high, which can reach 75-85%, and the space-time yield is high (the olefin yield is as high as 1.42 mmol/h g), the product is easy to separate, and has a good application prospect .

(3) The metal oxide in the catalyst has a higher specific surface area, so there are more active sites on the surface of the metal oxide, which is more conducive to the progress of the catalytic reaction.

(4) On the one hand, the role of component II in the catalyst is to further convert the active gas-phase intermediates produced by component I to obtain low-carbon olefins by coupling with component I. Due to the effect of component II on the equilibrium pull of the series reaction, the Promote the activation and conversion of component I to syngas to improve the conversion rate. On the other hand, the special pore structure of the molecular sieve in component II used in the present invention has a unique type-selective effect, and can obtain more ethylene products with high selectivity. .

(5) The function of the present invention cannot be achieved by using component I or component II described in the present invention separately. For example, when component I is used alone, the selectivity of methane in the product is very high, and the conversion rate is very low, while the When component II is used alone, it is almost impossible to activate the conversion of syngas, and only the synergistic catalysis of component I and component II can achieve efficient syngas conversion and obtain excellent selectivity. This is because component I can activate the synthesis gas to generate specific active gas-phase intermediates, and the intermediates diffuse into the pores of component II through the gas phase. Due to the molecular sieves with the MOR structure selected in the present invention, they have special pore structure and acidity, which can effectively The active gas-phase intermediates produced by component I are further activated and converted into olefins. Due to the special pore structure of the II component, the product has special selectivity.

(6) Component II of the catalyst of the present invention is modified with a heterocyclic organic base, and the selectivity of catalyzing synthesis gas to obtain a single component of ethylene is as high as 75-85%, and the selectivity of methane is lower than 5%, and greatly inhibits The selectivity of hydrocarbons above C4.

Detailed ways

The present invention will be further illustrated by the following examples, but the scope of the claims of the present invention is not limited by these examples. Meanwhile, the embodiments only provide some conditions for achieving this purpose, but it does not mean that these conditions must be satisfied to achieve this purpose.

Example 1

1. Preparation of component I

The present invention will be further illustrated by the following examples, but the scope of the claims of the present invention is not limited by these examples. Meanwhile, the embodiments only provide some conditions for achieving this purpose, but it does not mean that these conditions must be satisfied to achieve this purpose.

The specific surface area of the sample can be tested by nitrogen or argon physical adsorption.

The metal oxides of the present invention can be obtained by purchasing commercially available metal oxides with high specific surface area, or by the following methods:

1. Preparation of catalyst component I

(1) Synthesis of ZnO materials with high specific surface by precipitation method:

(1) Weigh 3 parts, each 0.446g (1.5mmol) Zn(NO ₃ ) ₂ ·6H ₂ O into 3 containers, and then weigh 0.300g (7.5mmol), 0.480g (12mmol), 0.720g (18mmol) NaOH was added to the above three containers in turn, and then 30ml of deionized water was added into the three containers, stirred at 70°C for more than 0.5h to make the solution evenly mixed, and cooled to room temperature naturally. The reaction solution was centrifuged to collect the centrifuged precipitate, and washed twice with deionized water to obtain a ZnO metal oxide precursor;

(2) Firing: After the product obtained above is dried in air, calcining is carried out in the atmosphere, that is, a ZnO material with a high specific surface is obtained. The atmosphere is an inert gas, a reducing gas or an oxidizing gas; the inert gas is one or more of N ₂ , He and Ar; the reducing gas is one or two of H ₂ , CO, and the reducing gas is also Inert gas may be contained; the oxidizing gas is one or more of O ₂ , O ₃ , and NO ₂ , and the oxidizing gas may also contain inert gas. The roasting temperature is 300-700°C, and the time is 0.5h-12h.

The purpose of calcination is to decompose the precipitated metal oxide precursor into oxide nanoparticles with high specific surface area at high temperature, and the decomposed oxide surface adsorbed species can be cleaned by the high temperature treatment of calcination.

The specific samples and their preparation conditions are shown in Table 1. As a comparative example, ZnO#4 in the table is a commercially available ZnO single crystal with low specific surface area.

Table 1 Preparation of ZnO materials and their parameter properties

(2) Synthesis of MnO materials with high specific surface area by co-precipitation method:

The preparation process is the same as the above-mentioned ZnO#2, the difference is that the precursor of Zn is replaced by the corresponding precursor of Mn, which can be one of manganese nitrate, manganese chloride, and manganese acetate, and here is manganese nitrate, corresponding to The product is defined as MnO; the specific surface area is: 23 m ² /g.

( ₃ ) Synthesis of CeO2 materials with high specific surface area by co-precipitation method:

The preparation process is the same as the above-mentioned ZnO#2, the difference is that the precursor of Zn is replaced by the corresponding precursor of Ce, which can be one of cerium nitrate, cerium chloride, and cerium acetate, and here is cerium nitrate, corresponding to The product is defined as CeO ₂ ; the specific surface area is: 92 m ² /g.

(4) Synthesis of Ga ₂ O ₃ materials with high specific surface area by co-precipitation method:

The preparation process is the same as the above-mentioned ZnO#2, the difference is that the precursor of Zn is replaced with the corresponding precursor of Ga, which can be one of gallium nitrate, gallium chloride, and gallium acetate, here is gallium nitrate, corresponding to The product is defined as Ga ₂ O ₃ ; the specific surface area is: 55 m ² /g.

(5) Synthesis of Bi ₂ O ₃ materials with high specific surface area by co-precipitation method:

The preparation process is the same as the above-mentioned ZnO#2, except that the precursor of Zn is replaced with the corresponding precursor of Bi, which can be one of bismuth nitrate, bismuth chloride, and bismuth acetate, and here is bismuth nitrate. The corresponding products are defined as Bi ₂ O ₃ ; the specific surface areas are respectively: 87 m ² /g.

(6) Synthesis of In ₂ O ₃ materials with high specific surface area by co-precipitation method:

The preparation process is the same as the above-mentioned ZnO#2, the difference is that the precursor of Zn is replaced with the corresponding precursor of In, which can be one of indium nitrate, indium chloride, and indium acetate, here is indium nitrate, corresponding to The product is defined as In ₂ O ₃ ; the specific surface area is: 52 m ² /g

(VII) Synthesis of Mn _a Cr _(1-a) O _x , Mn _a Al _(1-a) O _x , Mn _a Zr _(1-a) O _x , Mn _a In ₍ 1-a) with high specific surface area by precipitation method _a) O _x , Zn _a Cr _(1-a) O _x , Zn _a Al _(1-a) O _x , Zn _a Ga _(1-a) O _x , Zn _a In _(1-a) O _x , Co _a Al _(1-a) O _x , Fe _a Al _(1-a) O _x , In _a Al _b Mn _(1-ab) O _x , In _a Ga _b Mn _(1-ab) O _x :

Zinc nitrate, aluminum nitrate, chromium nitrate, manganese nitrate, zirconium nitrate, indium nitrate, cobalt nitrate, and ferric nitrate are used as precursors, mixed with ammonium carbonate in water at room temperature (ammonium carbonate is used as a precipitant, and the charging ratio is Ammonium carbonate is excessive or the ratio of preferred ammonium ion and metal ion is 1:1); above-mentioned mixed solution is aged, then taken out for washing, filtration and drying, and the solid of gained is roasted under air atmosphere to obtain the metal oxide of high specific surface , the specific samples and their preparation conditions are shown in Table 2 below.

Table 2 Preparation and performance parameters of metal oxides with high specific surface area

(8) Metal oxide dispersed by dispersant Cr ₂ O ₃ , Al ₂ O ₃ or ZrO ₂

Using dispersant Cr ₂ O ₃ , Al ₂ O ₃ or ZrO ₂ as carrier, the metal oxides dispersed in Cr ₂ O ₃ , Al ₂ O ₃ or ZrO ₂ were prepared by precipitation deposition method. Taking the preparation of dispersed ZnO as an example, commercial Cr ₂ O ₃ (specific surface area of about 5 m ² /g), Al ₂ O ₃ (specific surface area of about 20 m ² /g) or ZrO ₂ (specific surface area of about 10 m ² /g) g) pre-dispersed in water as carrier, then adopt zinc nitrate as raw material, mix and precipitate with sodium hydroxide precipitating agent at room temperature, the molar concentration of Zn ²⁺ is 0.067M, and the molar ratio of Zn ²⁺ and precipitating agent is 1:8; then aged at 160°C for 24 hours to obtain ZnO dispersed by Cr ₂ O ₃ , Al ₂ O ₃ or ZrO ₂ as a carrier (the content of dispersant in component I is 0.1 wt %, 20 wt % in turn) , 85wt%). The obtained samples were calcined at 500°C for 1 h under air, and the products were defined as dispersed oxides 1-3 in sequence, and their specific surface areas were: 148m ² /g, 115m ² /g, 127m ² /g.

In the same way, SiO ₂ (specific surface area is about 2m ² /g), Ga ₂ O ₃ (specific surface area is about 10m ² /g) or TiO ₂ (specific surface area is about 15m ² /g) can be obtained as carrier dispersion. MnO oxide (the content of dispersant in component I is 5wt%, 30wt%, 60wt% in sequence), and the products are defined as dispersed oxides 4-6 in sequence. Its specific surface area is: 97m ² /g, 64m ² /g, 56m ² /g.

In the same way, activated carbon (specific surface area is about 1000m ² /g), graphene (specific surface area is about 500m ² /g) or carbon nanotubes (specific surface area is about 300m ² /g) can be obtained as carrier dispersed ZnO Oxides (the content of dispersant in component I is 5wt%, 30wt%, 60wt% in sequence), and the products are defined as dispersed oxides 7-9. Its specific surface area is: 177m ² /g, 245m ^{2 /g, 307m 2 /} g.

2. Preparation of II component (molecular sieve with MOR topology)

The MOR topological structure is an orthorhombic crystal system, and has a one-dimensional channel structure with parallel elliptical through-channel channels, including 8 rings and 12-ring parallel one-dimensional through-channel channels, and there are 8 channels on the side of the main channel of the 12-ring. Ring pockets are connected.

The MOR molecular sieve of the present invention can be a commercial molecular sieve purchased directly, or a self-synthesized molecular sieve. Here, the MOR molecular sieve produced by the catalyst factory of Nankai University is used as MOR1; 7 molecular sieves with MOR structure are also prepared by hydrothermal synthesis method by oneself;

The specific preparation process is:

According to n(SiO ₂ )/n(Al ₂ O ₃ )=15, n(Na ₂ O)/n(SiO ₂ )=0.2, n(H ₂ O)/n(SiO ₂ )=26.

Mix aluminum sulfate and sodium hydroxide solution, then add silica sol, and stir for 1 hour to obtain a homogeneous initial gel, which is then transferred to an autoclave, statically crystallized at 180 °C for 24 hours, and then quenched, washed, and dried. A sample of mordenite was obtained, labeled Na-MOR.

Take Na-MOR, mix it with 1 mol/L ammonium chloride solution, stir at 90° C. for 3 hours, wash, dry, carry out 4 consecutive times, and calcinate at 450 degrees for 6 hours to obtain hydrogen-type mordenite.

The framework elements of the molecular sieve with MOR topology prepared by the above process can be Si-Al-O, Ga-Si-O, Ga-Si-Al-O, Ti-Si-O, Ti-Al-Si-O , one of Ca-Al-O, Ca-Si-Al-O;

H is connected to the O element of part of the skeleton, and the corresponding products are defined as MOR1-8 in turn;

Table 3 Preparation and performance parameters of molecular sieves with MOR topology

Take an appropriate amount of the prepared molecular sieve and carry out dehydration and degassing treatment under vacuum at a temperature of 400 °C and a pressure of 10 ^-4 Pa. After 10 hours, it is lowered to 300 °C, and an organic base gas of 200 Pa is introduced into the vacuum chamber, and after equilibration for 10 hours Desorb at the same temperature for 1 h.

MOR1 was sequentially treated with furan, thiophene, pyrrole, thiazole, imidazole, pyridine, pyrazine, pyrimidine, pyridazine, indole, quinoline, pteridine, and acridine to obtain MOR9-21.

To illustrate the modification of heterocyclic compounds containing substituents, MOR2 was treated with 1-methylfuran to obtain MOR22; MOR3 was treated with 1-methylpyrrole to obtain MOR23; MOR4 was treated with 3,5-lutidine to obtain MOR24; MOR5 was treated with 4-ethylpyridine to give MOR25; MOR6 was treated with 3-methylquinoline to give MOR26; MOR7 was treated with 4-methylindole to give MOR27; MOR8 was treated with 5-methylacridine to give MOR28.

3. Preparation of catalyst

Add component I and component II in the required proportions into the container, and use one or more of the extrusion force, impact force, cutting force, friction force, etc. generated by the high-speed movement of these materials and/or the container. To achieve separation, crushing, mixing and other purposes, by adjusting the temperature and carrier gas atmosphere to achieve the conversion of mechanical energy, thermal energy and chemical energy, and further adjust the interaction between different components.

During the mechanical mixing process, the mixing temperature can be set to 20-100°C, which can be carried out in the atmosphere or directly in the air, and the atmosphere can be selected from any of the following gases:

a) nitrogen and/or inert gas;

b) a mixture of hydrogen and nitrogen and/or inert gas, wherein the volume of hydrogen in the mixture is 5-50%;

c) a mixture of CO and nitrogen and/or inert gas, wherein the volume of CO in the mixture is 5-20%;

d) A mixed gas of O ₂ and nitrogen and/or inert gas, wherein the volume of O ₂ in the mixed gas is 5-20%, and the inert gas is one or both of helium, argon, and neon above.

Mechanical mixing can be compounded by one or more of mechanical stirring, ball milling, shaking table mixing and mechanical grinding, as follows:

Mechanical stirring: In the stirring tank, use a stirring rod to mix components I and II. By controlling the stirring time (5min-120min) and speed (30-300 rpm), the components I and components can be adjusted. The degree of mixing of II.

Ball milling: The abrasive and the catalyst are rolled at high speed in the grinding tank, and the catalyst is strongly impacted and rolled to achieve the effect of dispersing and mixing component I and component II. By controlling the abrasive (material can be stainless steel, agate, quartz. Size range: 5mm-15mm). Ratio to catalyst (mass ratio range: 20-100:1).

Shaker mixing method: Premix Component I and Component II and put them into a container; realize the mixing of Component I and Component II by controlling the reciprocating or circular oscillation of the shaker; : 1-70 rpm) and time (range: 5min-120min) to achieve uniform mixing.

Mechanical grinding method: Premix component I and component II, and put them into a container; under a certain pressure (range: 5 kg-20 kg), the relative movement is carried out by the grinding tool and the mixed catalyst (velocity range: 30-300 rev/min) to achieve uniform mixing.

The specific catalyst preparation and its parameter characteristics are shown in Table 4.

Table 4 Preparation of catalysts and their parameter characteristics

Examples of Catalytic Reactions

A fixed bed reaction is used as an example, but the catalyst is also suitable for a moving bed reactor. The device is equipped with a gas mass flow meter and an online product analysis chromatography (the tail gas of the reactor is directly connected to the quantitative valve of the chromatography for periodic real-time sampling and analysis).

The above-mentioned catalyst 2g of the present invention was placed in a fixed-bed reactor, and Ar was used to replace the air in the reactor, and then the temperature was raised to 300° C. in an H atmosphere, and the synthesis gas (H ₂ / _CO molar ratio=0.2- 3.5), the pressure of the synthesis gas is 0.5-10MPa, the temperature is raised to the reaction temperature of 300-600°C, and the space velocity of the reaction raw material gas is adjusted to 500-8000ml/g/h. The product was analyzed by on-line chromatographic detection.

Changes in temperature, pressure and space velocity can change the reaction performance. The selectivity of ethylene and propylene in the product is as high as 83-90%, and the conversion rate of raw materials is 10-60%; due to the effective synergistic effect of molecular sieve and oxide, the large-scale generation of methane is avoided, and the methane selectivity is lower than 5%. The selectivity reaches 75-85%.

The application of table 5 catalyst and its effect

Component I of the catalyst used in Comparative Example 2 is metal ZnCo, and the ZnCo molar ratio is 1:1, and the remaining parameters and mixing process are the same as catalyst C.

Component I of the catalyst used in Comparative Example 3 is TiO ₂ , and other parameters and mixing processes are the same as those of catalyst C.

The reaction results of Comparative Examples 4-11 show that the modification of MOR with organic bases has a significant effect on the regulation of catalytic performance. Compared with the catalysts without organic bases, the regulated catalysts significantly reduce the methane and hydrocarbons above C4. selectivity, while improving the selectivity of light olefins and ethylene.

The catalyst used in Comparative Example 12 is a sample with only component I, which is ZnO#1, and does not contain MOR molecular sieve. The reaction conversion rate is very low, and the products are mainly by-products such as dimethyl ether and methane, and almost no ethylene is generated. .

The catalyst adopted in Comparative Example 13 is only component II, which is MOR9 molecular sieve, and does not contain the sample of component I, and the catalytic reaction has almost no activity.

Comparative examples 12 and 13 show that only component I or component II has an extremely poor reaction effect, and does not have the excellent reaction performance described in the present invention at all.

The above embodiments are provided for the purpose of describing the present invention only, and are not intended to limit the scope of the present invention. The scope of the invention is defined by the appended claims. Various equivalent replacements and modifications made without departing from the spirit and principle of the present invention should be included within the scope of the present invention.

Claims (18)

1. A catalyst, characterized by: the catalyst comprises a component I and a component II, wherein the component I and the component II are compounded together in a mechanical mixing mode, the active component of the component I is a metal oxide, and the component II is a molecular sieve with an MOR topological structure; the molecular sieve with the MOR topological structure is subjected to organic alkali modification treatment; the modification treatment is to disperse organic base intoA B acid site within a 12-ring pore of the molecular sieve of said MOR topology; the organic base is a heterocyclic compound; the metal oxide is MnO_x、Mn_aCr_(1-a)O_x、Mn_aAl_(1-a)O_x、Mn_aZr_(1-a)O_x、Mn_aIn_(1-a)O_x、ZnO_x、Zn_aCr_(1-a)O_x、Zn_aAl_(1-a)O_x、Zn_aGa_(1-a)O_x、Zn_aIn_(1-a)O_x、CeO_x、Co_aAl_(1-a)O_x、Fe_aAl_(1-a)O_x、GaO_x、BiO_x、InO_x、In_aAl_bMn_(1-a-b)O_x、In_aGa_bMn_(1-a-b)O_xOne or more than two of them; the MnO_x、ZnO_x、CeO_x、GaO_x、BiO_x、InO_xHas a specific surface area of 1 to 100m²(ii)/g; the Mn is_aCr_(1-a)O_x、Mn_aAl_(1-a)O_x、Mn_aZr_(1-a)O_x、Mn_aIn_(1-a)O_x、Zn_aCr_(1-a)O_x、Zn_aAl_(1-a)O_x、Zn_aGa_(1-a)O_x、Zn_aIn_(1-a)O_x、Co_aAl_(1-a)O_x、Fe_aAl_(1-a)O_x、In_aAl_bMn_(1-a-b)O_x、In_aGa_bMn_(1-a-b)O_xHas a specific surface area of 5 to 150m²(ii)/g; the value range of x is 0.7-3.7, and the value range of a is 0-1; the value range of a + b is 0-1.

2. The catalyst of claim 1, wherein: the organic base is a heteroaryl compound.

3. The catalyst of claim 1, wherein: the organic base is a heteroaryl compound containing 1-2 heteroatoms.

4. The catalyst of claim 1, wherein: the organic base is a 5 or6 membered heteroaryl compound containing 1-2N atoms.

5. The catalyst of claim 1, wherein: the MnO_x、ZnO_x、CeO_x、GaO_x、BiO_x、InO_xHas a specific surface area of 50 to 100m²(ii)/g; the Mn is_aCr_(1-a)O_x、Mn_aAl_(1-a)O_x、Mn_aZr_(1-a)O_x、Mn_aIn_(1-a)O_x、Zn_aCr_(1-a)O_x、Zn_aAl_(1-a)O_x、Zn_aGa_(1-a)O_x、Zn_aIn_(1-a)O_x、Co_aAl_(1-a)O_x、Fe_aAl_(1-a)O_x、In_aAl_bMn_(1-a-b)O_x、In_aGa_bMn_(1-a-b)O_xHas a specific surface area of 50 to 150m²/g。

6. The catalyst of claim 1, wherein: the heterocyclic compound is furan, thiophene, pyrrole, thiazole, imidazole, pyridine, pyrazine, pyrimidine, pyridazine, indole, quinoline, pteridine or acridine.

7. The catalyst of claim 6, wherein: the heterocyclic compound has one or more than two substituents of methyl, ethyl, amino and nitro.

8. The catalyst of claim 7, wherein: the substituent is meta-and/or para-substitution.

9. The catalyst of claim 1, wherein: the weight ratio of the active ingredients in the component I to the component II is 0.1-20.

10. The catalyst of claim 1, wherein: the weight ratio of the active ingredients in the component I to the component II is 0.3-8.

11. The catalyst of claim 1, wherein: the component I is also added with a dispersant, the metal oxide is dispersed in the dispersant, and the dispersant is Al₂O₃、SiO₂、Cr₂O₃、ZrO₂、TiO₂、Ga₂O₃One or more of activated carbon, graphene and carbon nanotubes.

12. The catalyst of claim 1, wherein: in the component I, the content of the dispersant is 0.05 to 90 weight percent, and the balance is metal oxide.

13. A catalyst as claimed in any one of claims 1 to 12, wherein: the framework element composition of the MOR topological structure molecular sieve is one or more than two of Si-Al-O, Ga-Si-O, Ga-Si-Al-O, Ti-Si-O, Ti-Al-Si-O, Ca-Al-O, Ca-Si-Al-O.

14. A method for preparing ethylene with high selectivity by using synthesis gas reaction is characterized in that: taking synthetic gas mixture as a reaction raw material, and carrying out conversion reaction on a fixed bed or a moving bed to obtain a low-carbon olefin product mainly containing ethylene, wherein the adopted catalyst is the catalyst in any one of claims 1 to 13.

15. The method of claim 14, wherein: the pressure of the synthesis gas is 0.5-10 MPa; the reaction temperature is 300-600 ℃; airspeed of 300-10000h^-1(ii) a The synthesis gas contains H₂Mixed gas of/CO, H₂The mol ratio of/CO is 0.2-3.5; the synthesis gas may also contain CO₂In which CO is₂The volume concentration in the synthesis gas is 0.1-50%.

16. The method of claim 15, wherein: the pressure of the synthesis gas is 1-8 MPa; the reaction temperature is 350-450 ℃; the space velocity is 500-^-1(ii) a The synthesis gas contains H₂Mixed gas of/CO, H₂The mol ratio of/CO is 0.3-2.5.

17. The method of claim 16, wherein: the pressure of the synthesis gas is 2-8 MPa; the space velocity is 500-6000h^-1。

18. The method of claim 14, wherein: the method directly converts the synthesis gas into C by a one-step method_2-4The selectivity of olefin and ethylene is 75-85%, and the selectivity of byproduct methane is<5%。