阅读说明：本技术 一种改性分子筛复合催化剂及其制备方法和应用 (Modified molecular sieve composite catalyst and preparation method and application thereof ) 是由 樊卫斌 王森 张莉 秦张峰 董梅 王建国 于 2020-04-03 设计创作，主要内容包括：本发明提供了一种改性分子筛复合催化剂及其制备方法和应用,属于催化剂技术领域。本发明提供的改性分子筛复合催化剂,包括复合金属氧化物和氢型RUB-13分子筛；所述复合金属氧化物中的金属由IIB族金属、IVB族金属和镧系金属构成。本发明以复合金属氧化物作为活性组分,以氢型RUB-13分子筛为载体组成的改性分子筛复合催化剂,用于CO<Sub>2</Sub>加氢制丙烯和丁烯,能够显著提高CO<Sub>2</Sub>转化率和丙烯+丁烯的收率,同时还能够有效降低副产物CO和烷烃的生成。(The invention provides a modified molecular sieve composite catalyst, a preparation method and application thereof, and belongs to the technical field of catalysts. The modified molecular sieve composite catalyst provided by the invention comprises a composite metal oxide and a hydrogen type RUB-13 molecular sieve; the metal in the composite metal oxide is composed of group IIB metal, group IVB metal and lanthanide metal. The invention usesModified molecular sieve composite catalyst composed of metal oxide as active component and hydrogen type RUB-13 molecular sieve as carrier and used for CO 2 The hydrogenation for preparing propylene and butylene can obviously improve CO 2 The conversion rate and the yield of the propylene and the butylene can also effectively reduce the generation of byproducts CO and alkane.)

1. A modified molecular sieve composite catalyst is characterized by comprising a composite metal oxide and a hydrogen type RUB-13 molecular sieve; the metal in the composite metal oxide is composed of group IIB metal, group IVB metal and lanthanide metal.

2. The modified molecular sieve composite catalyst of claim 1, wherein the molar ratio of the group IIB metal, the group IVB metal, and the lanthanide metal is (0.03-3.0): (0.1-6.0): (0.01-1.0).

3. The modified molecular sieve composite catalyst according to claim 1 or 2, wherein the mass ratio of the composite metal oxide to the hydrogen type RUB-13 molecular sieve is 1:4 to 4: 1.

4. The preparation method of the modified molecular sieve composite catalyst of any one of claims 1 to 3, characterized by comprising the following steps:

mixing water-soluble IIB group metal salt, water-soluble IVB group metal salt, water-soluble lanthanide metal salt and water, and heating and mixing the obtained composite metal ion solution and a complexing agent to obtain a colloidal substance;

roasting the colloidal substance to obtain a composite metal oxide;

and mixing the composite metal oxide and the hydrogen type RUB-13 molecular sieve to obtain the modified molecular sieve composite catalyst.

5. The preparation method according to claim 4, wherein the molar ratio of the composite metal ions to the complexing agent in the composite metal ion solution is 1:0.75 to 1:5.

6. The method according to claim 4, wherein the heating and mixing are carried out at a temperature of 60 to 95 ℃ for 1 to 15 hours.

7. The preparation method according to claim 4, wherein the roasting temperature is 400-700 ℃ and the roasting time is 1-20 h.

8. Use of the modified molecular sieve composite catalyst according to any one of claims 1 to 3 or the modified molecular sieve composite catalyst prepared by the preparation method according to any one of claims 4 to 7 in preparation of propylene and butylene by carbon dioxide hydrogenation.

9. The application of the modified molecular sieve composite catalyst in the preparation of propylene and butylene by carbon dioxide hydrogenation comprises the following steps:

catalysis of H with modified molecular sieve composite catalyst₂/CO₂The mixed gas is hydrogenated to obtain propylene and butylene, and H is₂And CO₂The volume ratio of (1: 1) - (8: 1), and the space velocity of the mixed gas is 800-10000 mL/(h.g);

the temperature of the hydrogenation reaction is 260-400 ℃, the time is 20-1000 h, and the pressure is 0.1-5 MPa.

Technical Field

The invention relates to the technical field of catalysts, in particular to a modified molecular sieve composite catalyst and a preparation method and application thereof.

Background

The rapid consumption of fossil resources leads to a drastic increase in the carbon dioxide content of the atmosphere, thereby bringing about a serious greenhouse effect. Carbon dioxide capture, storage and utilization is one possible method of controlling the carbon dioxide content of the atmosphere. The method for preparing olefin by converting carbon dioxide in a hydrogenation reduction mode not only can reasonably use carbon dioxide and slow down greenhouse effect; meanwhile, chemical products with high added values are obtained, and the energy crisis caused by the reduction of petroleum resources can be effectively solved.

The preparation of the low-carbon olefin by carbon dioxide hydrogenation can be realized by a modified Fischer-Tropsch synthesis method. Although the conversion rate of carbon dioxide is high in the Fischer-Tropsch synthesis route, the selectivity of low-carbon olefin is lower than 61% and the selectivity of methane is as high as 25% due to the limitation of the product distribution rule of Fischer-Tropsch synthesis (ASF). For example, chinese patent CN104437504A discloses that a Fe-based catalyst generates a large amount of methane and other long-chain alkanes in the preparation of olefins by hydrogenation of carbon dioxide, and the selectivity of low-carbon olefins is only about 60%. Another common method for preparing low-carbon olefins by carbon dioxide hydrogenation is to first reduce carbon dioxide to methanol, and then prepare low-carbon olefins from methanol by acid catalysis of a molecular sieve. For example, In the high research institute (ACS Catalysis,2018,8,571-578) of China academy of sciences, the selectivity of low-carbon olefin In total hydrocarbon can reach 80% by using the In2O3/H-SAPO-34 composite catalyst to catalyze the carbon dioxide hydrogenation reaction, but the selectivity of the byproduct carbon monoxide is close to 90%; chinese patent CN106423263A discloses a method for preparing olefin by carbon dioxide hydrogenation, in which a catalyst prepared by physically mixing ZnZr oxide and H-SAPO-34 molecular sieve has a selectivity of low-carbon olefin prepared by the catalyst of about 60-80%, but the catalyst also generates a large amount of carbon monoxide by-products, the selectivity to CO reaches 36-60%, and the carbon dioxide conversion rate is low (< 15%); chinese patent CN110327969A discloses a nitrogen-doped metal oxide and molecular sieve composite catalyst used in the preparation of olefin by carbon dioxide hydrogenation, but the carbon dioxide conversion rate is only 9-13%, and the yield of low-carbon olefin is less than 7.2%.

Disclosure of Invention

In view of the above, the present invention aims to provide a modified molecular sieve composite catalyst, a preparation method and an application thereof, and the modified molecular sieve composite catalyst provided by the present invention is used for CO₂The hydrogenation for preparing low-carbon olefin (especially propylene and butylene) can obviously improve CO₂The conversion rate and the yield of the propylene and the butylene can be reduced, and the generation of a byproduct CO can be effectively reduced.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a modified molecular sieve composite catalyst, which comprises a composite metal oxide and a hydrogen type RUB-13 molecular sieve; the metal in the composite metal oxide is composed of group IIB metal, group IVB metal and lanthanide metal.

Preferably, the molar ratio of the group IIB metal, the group IVB metal and the lanthanide metal is (0.03-3.0): (0.1-6.0): (0.01-1.0).

Preferably, the mass ratio of the composite metal oxide to the hydrogen type RUB-13 molecular sieve is 1: 4-4: 1.

The invention provides a preparation method of the modified molecular sieve composite catalyst in the technical scheme, which comprises the following steps:

mixing water-soluble IIB group metal salt, water-soluble IVB group metal salt, water-soluble lanthanide metal salt and water, and heating and mixing the obtained composite metal ion solution and a complexing agent to obtain a colloidal substance;

roasting the colloidal substance to obtain a composite metal oxide;

and mixing the composite metal oxide and the hydrogen type RUB-13 molecular sieve to obtain the modified molecular sieve composite catalyst.

Preferably, the molar ratio of the composite metal ions to the complexing agent in the composite metal ion solution is 1: 0.75-1: 5.

Preferably, the heating and mixing temperature is 60-95 ℃ and the time is 1-15 h.

Preferably, the roasting temperature is 400-700 ℃, and the roasting time is 1-20 h.

The invention also provides the application of the modified molecular sieve composite catalyst in the technical scheme or the modified molecular sieve composite catalyst prepared by the preparation method in the technical scheme in the preparation of propylene and butylene through carbon dioxide hydrogenation.

Preferably, the application conditions of the modified molecular sieve composite catalyst in the preparation of propylene and butylene by carbon dioxide hydrogenation comprise:

catalysis of H with modified molecular sieve composite catalyst₂/CO₂The mixed gas is subjected to hydrogenation reaction to obtain propylene and butylene, and H in the reaction gas₂And CO₂The volume ratio of (A) is 1: 1-8: 1, and the space velocity of reaction gas is 800-10000 mL/(h.g);

the reaction temperature is 260-400 ℃, the reaction time is 20-1000 h, and the pressure is 0.1-5 MPa.

The invention provides a modified molecular sieve composite catalyst, which comprises a composite metal oxide and a hydrogen type RUB-13 molecular sieve; the metal in the composite metal oxide is composed of group IIB metal, group IVB metal and lanthanide metal. The hydrogen type RUB-13 molecular sieve has the characteristics of low strong acid content, low acid strength and high specific surface area, can selectively generate propylene and butylene, can also reduce the secondary hydrogenation rate of low-carbon olefin, and reduces the generation of byproduct alkane; the surface of the composite metal oxide has a large number of oxygen cavities, which is beneficial to CO₂Adsorption activation of (1), CO increase₂The conversion rate, the generation of carboxylate intermediate, the reaction rate of reverse water gas and the generation of byproduct CO are reduced. The invention adopts composite metal oxide as active component, and uses hydrogen type RUB-13 molecular sieve for CO₂The C can be obviously improved by preparing propylene and butylene through hydrogenationO₂The conversion rate and the yield of the propylene and the butylene can be simultaneously and effectively reduced, and the generation of byproducts CO and alkane can be simultaneously reduced. As shown by the results of the examples of the invention, the modified molecular sieve composite catalyst provided by the invention is used for CO₂The hydrogenation is carried out to prepare propylene and butylene, the conversion rate of carbon dioxide is as high as 30.1%, the selectivity and yield of propylene and butylene are respectively as high as 65.3% and 14.5%, and the selectivity of byproduct CO can be reduced to 26.5%.

The preparation method of the modified molecular sieve composite catalyst provided by the invention is simple to operate, low in cost, free of secondary pollution and suitable for industrial production.

Drawings

FIG. 1 is an XRD spectrum of a composite metal oxide prepared in example 4;

FIG. 2 is an XRD spectrum of the hydrogen RUB-13 molecular sieve prepared in example 4;

FIG. 3 is a schematic diagram showing the performance results of the modified molecular sieve composite catalyst prepared in example 4 in the reaction of preparing propylene and butylene by hydrogenation of carbon dioxide;

FIG. 4 is a schematic diagram showing the performance results of the modified molecular sieve composite catalyst prepared in example 4 in the reaction of preparing propylene and butylene by hydrogenation of carbon dioxide.

Detailed Description

The invention provides a modified molecular sieve composite catalyst, which comprises a composite metal oxide and a hydrogen type RUB-13 molecular sieve; the metal in the composite metal oxide is preferably composed of a group IIB metal, IVB and a lanthanide metal.

In the present invention, the molar ratio of the group IIB metal, the group IVB metal, and the lanthanide series metal in the composite metal oxide is preferably (0.03 to 3.0): (0.1-6.0): (0.01-1.0), more preferably (0.1-2.5): (0.5-5): (0.1 to 0.8), most preferably (0.5 to 2): (1-4): (0.2-0.5).

In the present invention, the group IIB metal preferably includes Zn or Cd, more preferably Zn; the group IVB metal preferably comprises Ti, Zr or Hf, more preferably Zr; the lanthanide metal preferably comprises La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, more preferably La, Ce or Pr, most preferably Ce. In thatIn the present invention, the chemical composition of the composite metal oxide is preferably Zn_aCe_bZr_cO_dWherein a is 0.03-3.0, b is 0.01-1.0, and c is 0.1-6.0, and the value of d is not particularly limited, so that the total valence of each metal element in the composite metal oxide is zero. In the present invention, the composite metal in the composite metal oxide forms a tetragonal solid solution structure.

In the invention, the molar ratio of the weak acid to the strong acid of the hydrogen type RUB-13 molecular sieve is preferably 1.2-3: 1, more preferably 1.5-2.8: 1, and most preferably 2-2.5: 1; the specific surface area of the hydrogen type RUB-13 molecular sieve is preferably 350-500 m²(iv)/g, more preferably 380 to 480m²(iv) g, most preferably 400 to 480m²(ii) in terms of/g. The hydrogen type RUB-13 molecular sieve utilized by the invention has the characteristics of low strong acid content, low acid strength and high specific surface area, can selectively generate propylene and butylene, and can also reduce the secondary hydrogenation rate of low-carbon olefin and reduce the generation of byproduct alkane.

In the invention, the mass ratio of the composite metal oxide to the hydrogen type RUB-13 molecular sieve is preferably 1: 4-4: 1, more preferably 1: 3-3: 1, and most preferably 1: 2-2: 1.

In the present invention, the hydrogen form of the RUB-13 molecular sieve is preferably obtained by self-production. In the present invention, the method for preparing the hydrogen-form RUB-13 molecular sieve preferably comprises the steps of:

mixing an RUB-13 molecular sieve seed crystal, a silicon source, an aluminum source, a boron source, an alkali source, an organic structure directing agent and water, and sequentially carrying out hydrothermal reaction and first roasting to obtain an RUB-13 molecular sieve;

and mixing the RUB-13 molecular sieve with an ammonium-containing solution, and sequentially carrying out ion exchange reaction and second roasting to obtain the hydrogen type RUB-13 molecular sieve.

The method comprises the steps of mixing the RUB-13 molecular sieve seed crystal, a silicon source, an aluminum source, a boron source, an alkali source, an organic structure directing agent and water, and sequentially carrying out hydrothermal reaction and first roasting to obtain the RUB-13 molecular sieve.

In the present invention, the RUB-13 molecular sieve seeds are preferably RUB-13 molecular sieve seeds containing an organic structure directing agent or RUB-13 molecular sieve seeds not containing an organic structure directing agent.

In the present invention, the method for preparing the seed crystals of the RUB-13 molecular sieve containing the organic structure directing agent preferably comprises the following steps: and mixing a first silicon source, a first boron source, a first organic structure directing agent and water, and sequentially carrying out a first hydrothermal reaction to obtain the RUB-13 molecular sieve seed crystal.

In the present invention, the first silicon source preferably includes white carbon black or silica sol, and the content of silica in the silica sol is preferably 25% to 50%. In the present invention, the first boron source preferably comprises boric acid. In the present invention, the first organic structure directing agent preferably comprises pentamethylpiperidine and ethylenediamine; the molar ratio of pentamethylpiperidine to ethylenediamine is preferably 1:1 to 1:6, and more preferably 1:2 to 1:5. In the invention, the first silicon source and the phosphoric acid are respectively used as SiO₂And P₂O₅The molar ratio of the first silicon source to the first boron source is preferably 1: 1-4: 1, and more preferably 2: 1-3: 1; the molar ratio of the first silicon source to the water is 1: 50-1: 150, and more preferably 1: 80-1: 120; the molar ratio of the first silicon source to the first organic structure directing agent is preferably 1:1.5 to 1:5.0, more preferably 1:2.5 to 1: 4.

In the present invention, the first silicon source, the first boron source, the first organic structure directing agent and the water are preferably mixed by stirring, and the speed and time of the stirring are not particularly limited in the present invention, and the raw materials can be uniformly mixed by using the stirring speed and time known to those skilled in the art.

In the invention, the first hydrothermal reaction temperature is preferably 140-200 ℃, more preferably 160-180 ℃, and most preferably 170 ℃; the time of the first hydrothermal reaction is preferably 140-200 h, more preferably 170-190 h, and most preferably 180 h. In the invention, in the first hydrothermal reaction process, a silicon source and a boron source are self-assembled under the action of an organic structure directing agent to form a RUB-13 skeleton structure containing silicon and boron.

After the first hydrothermal reaction, the method preferably further comprises the steps of carrying out solid-liquid separation, washing and drying on a system of the first hydrothermal reaction to obtain the RUB-13 molecular sieve seed crystal containing the organic structure directing agent. The solid-liquid separation method of the present invention is not particularly limited, and a solid-liquid separation method known to those skilled in the art, specifically, centrifugation, may be employed. In the invention, the water used for washing is preferably deionized water; in the present invention, the number of times of the washing with water is not particularly limited, and the washing solution obtained after the washing with water is neutral. In the invention, the drying temperature is preferably 30-120 ℃, and more preferably 50-90 ℃; most preferably 60-80 ℃; the drying time is preferably 4-20 h, more preferably 6-15 h, and most preferably 8-12 h.

In the present invention, the method for preparing the RUB-13 molecular sieve seeds without the organic structure directing agent preferably comprises the steps of: and roasting the RUB-13 molecular sieve seed crystal containing the organic structure directing agent to obtain the RUB-13 molecular sieve seed crystal without containing the organic structure directing agent. In the invention, the roasting temperature is preferably 500-650 ℃, and more preferably 550-600 ℃; the roasting time is preferably 8-30 hours, and more preferably 18-24 hours; the roasting atmosphere is preferably air; the calcination is preferably carried out in a muffle furnace; during the firing process, the organic structure directing agent is removed. After the calcination, the present invention preferably further comprises cooling the calcined product to room temperature. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be used, specifically, natural cooling.

After obtaining the RUB-13 molecular sieve seed crystal, mixing the RUB-13 molecular sieve seed crystal, a silicon source, an aluminum source, a boron source, an alkali source, an organic structure directing agent and water, and sequentially carrying out hydrothermal reaction and first roasting to obtain the RUB-13 molecular sieve.

In the invention, the silicon source preferably comprises white carbon black or silica sol, and the content of silicon dioxide in the silica sol is preferably 25-50%. In the present invention, the boron source preferably comprises boric acid. In the present invention, the organic structure directing agent preferably comprises pentamethylpiperidine and ethylenediamine; the molar ratio of pentamethylpiperidine to ethylenediamine is preferably 1:1 to 6, and more preferably 1:2 to 5. In the present invention, the aluminum source preferably comprises isopropyl alcoholAluminum alkoxides, aluminum hydroxides, aluminum sulfates, aluminum chlorides, or aluminum nitrates. In the invention, the alkali source is preferably one or more of ammonia water, sodium hydroxide and potassium hydroxide; when the alkali source is a mixture of two or more alkali sources, the ratio of the different kinds of alkali sources used in the present invention is not particularly limited, and may be any ratio. In the invention, the silicon source, the aluminum source and the phosphorus source are respectively used as SiO₂、Al₂O₃And P₂O₅The molar ratio of the silicon source to the boron source is preferably 1: 1-4: 1, and more preferably 2: 1-3: 1; the molar ratio of the silicon source to the water is 1: 50-1: 300, and more preferably 1: 100-1: 200; the molar ratio of the silicon source to the aluminum source is preferably 50: 1-300: 1, and more preferably 100: 1-200: 1; the molar ratio of the silicon source to the organic structure directing agent is preferably 1:1.5 to 1:5.0, and more preferably 1:2.5 to 1: 4. In the invention, the molar ratio of the silicon source to the RUB-13 molecular sieve seed crystal is preferably 1: 0.01-1: 0.2, and more preferably 1: 0.05-1: 0.1.

In the present invention, the mixing manner of the RUB-13 molecular sieve seed crystal, the silicon source, the aluminum source, the boron source, the alkali source, the organic structure directing agent and the water is preferably stirring mixing, and the speed and time of the stirring mixing are not particularly limited in the present invention, and the raw materials can be uniformly mixed by using the stirring speed and time well known to those skilled in the art.

In the invention, the hydrothermal reaction temperature is preferably 140-200 ℃, more preferably 160-180 ℃, and most preferably 170 ℃; the time of the hydrothermal reaction is preferably 140-200 h, more preferably 160-190 h, and most preferably 168 h. In the invention, in the hydrothermal reaction process, a silicon source, an aluminum source and a boron source are self-assembled under the action of an organic structure directing agent to form the RUB-13 framework structure containing silicon, aluminum and boron.

After the second hydrothermal reaction, the present invention preferably further comprises subjecting the system of the hydrothermal reaction to solid-liquid separation and washing. The solid-liquid separation method of the present invention is not particularly limited, and a solid-liquid separation method known to those skilled in the art, specifically, centrifugation, may be employed. In the invention, the water used for washing is preferably deionized water; in the present invention, the number of times of the washing with water is not particularly limited, and the washing solution obtained after the washing with water is neutral.

In the invention, the temperature of the first roasting is preferably 500-650 ℃, and more preferably 550-600 ℃; the first roasting time is preferably 2-24 hours, and more preferably 5-15 hours; the atmosphere of the first calcination is preferably air; the first firing is preferably carried out in a muffle furnace. In the present invention, the organic structure directing agent is removed during the first firing.

After the first calcination, the invention preferably cools the product of the first calcination to room temperature to obtain the RUB-13 molecular sieve. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be used, specifically, natural cooling.

After the RUB-13 molecular sieve is obtained, the RUB-13 molecular sieve and an ammonium-containing solution are mixed, and then ion exchange reaction and secondary roasting are sequentially carried out to obtain the hydrogen type RUB-13 molecular sieve.

In the present invention, the ammonium containing solution preferably comprises ammonium nitrate or ammonium chloride; the concentration of ammonium ions in the ammonium-containing solution is preferably 0.2 to 2mol/L, and more preferably 0.5 to 1 mol/L. The amount of the ammonium-containing solution used in the present invention is not particularly limited, and the RUB-13 molecular sieve can be immersed.

In the present invention, the mixing manner of the RUB-13 molecular sieve and the ammonium-containing solution is preferably stirring mixing, and the stirring mixing speed and time in the present invention are not particularly limited, and the raw materials can be uniformly mixed by using the stirring speed and time known to those skilled in the art.

In the invention, the temperature of the ion exchange reaction is preferably 40-100 ℃, and more preferably 60-90 ℃; the total time of the ion exchange reaction is preferably 3-20 h, and more preferably 5-15 h; the number of ion exchange is preferably 1-3, more preferably 3, and the time of each ion exchange is preferably 3-6 h, more preferably 5 h. In the invention, during the ion exchange reaction, sodium ions on the RUB-13 molecular sieve are exchanged for hydrogen ions to obtain the hydrogen type RUB-13 molecular sieve.

After the ion exchange reaction, the invention preferably further comprises the steps of carrying out solid-liquid separation, water washing and drying on the system of the ion exchange reaction. The solid-liquid separation method of the present invention is not particularly limited, and a solid-liquid separation method known to those skilled in the art, specifically, centrifugation, may be employed. In the invention, the water used for washing is preferably deionized water; the washing frequency is not specially limited, and the ammonium ions are removed completely, specifically 3-4 times. In the invention, the drying temperature is preferably 30-120 ℃, more preferably 50-90 ℃, and most preferably 60-80 ℃; the drying time is preferably 4-20 h, more preferably 6-15 h, and most preferably 8-12 h.

In the invention, the temperature of the second roasting is preferably 350-600 ℃, and more preferably 400-550 ℃; the second roasting time is preferably 1-8 hours, and more preferably 3-6 hours; the atmosphere of the second roasting is preferably air; the second firing is preferably carried out in a muffle furnace. In the present invention, the residual ammonium salt on the RUB-13 molecular sieve is removed in the second roasting process.

After the third calcination, the invention preferably cools the product of the second calcination to room temperature to obtain the hydrogen-form RUB-13 molecular sieve. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be used, specifically, natural cooling.

The invention adopts composite metal oxide as active component, and uses hydrogen type RUB-13 molecular sieve for CO₂The hydrogenation for preparing propylene and butylene can obviously improve CO₂The conversion rate and the yield of the propylene and the butylene can be simultaneously and effectively reduced, and the generation of byproducts CO and alkane can be simultaneously reduced.

The invention provides a preparation method of the modified molecular sieve composite catalyst in the technical scheme, which comprises the following steps:

mixing water-soluble IIB group metal salt, water-soluble IVB group metal salt, water-soluble lanthanide metal salt and water, and heating and mixing the obtained composite metal ion solution and a complexing agent to obtain a colloidal substance;

roasting the colloidal substance to obtain a composite metal oxide;

and mixing the composite metal oxide and the hydrogen type RUB-13 molecular sieve to obtain the modified molecular sieve composite catalyst.

The method comprises the steps of mixing water-soluble IIB group metal salt, water-soluble IVB group metal salt, water-soluble lanthanide metal salt and water, heating and mixing the obtained composite metal ion solution and a complexing agent to obtain a colloidal substance.

In the present invention, the water-soluble group IIB metal salt preferably includes a nitrate, chloride or sulfate of a group IIB metal, more preferably zinc nitrate, zinc chloride, zinc sulfate, cadmium nitrate, cadmium chloride or chromium sulfate, and most preferably zinc nitrate, zinc chloride or zinc sulfate. In the present invention, the water-soluble group IVB metal salt includes a nitrate, chloride or sulfate of a group IVB metal, more preferably titanium nitrate, titanium chloride, titanium sulfate, zirconium nitrate, zirconium chloride, zirconium sulfate, hafnium nitrate, hafnium chloride or hafnium sulfate, and more preferably zirconium nitrate, zirconium chloride or zirconium sulfate. In the present invention, the water-soluble lanthanoid metal salt preferably includes a nitrate, chloride or sulfate of a lanthanoid metal, more preferably includes lanthanum nitrate, lanthanum chloride, lanthanum sulfate, cerium nitrate, cerium chloride, cerium sulfate, praseodymium nitrate, praseodymium chloride, praseodymium sulfate, neodymium nitrate, neodymium chloride, neodymium sulfate, promethium nitrate, promethium chloride, promethium sulfate, samarium nitrate, samarium chloride, samarium sulfate, europium nitrate, europium chloride, europium sulfate, gadolinium nitrate, gadolinium chloride, gadolinium sulfate, terbium nitrate, terbium chloride, terbium sulfate, dysprosium nitrate, dysprosium chloride, dysprosium sulfate, holmium nitrate, holmium chloride, holmium sulfate, erbium nitrate, erbium chloride, erbium sulfate, thulium nitrate, thulium chloride, thulium sulfate, ytterbium nitrate, ytterbium sulfate, lutetium nitrate, lutetium chloride or lutetium sulfate, and most preferably cerium nitrate, cerium chloride or cerium sulfate. In the present invention, when the chemical composition of the composite metal oxide is Zn_aCe_bZr_cO_dIn the case, the water-soluble group IIB metal salt, the water-soluble group IVB metal salt, and the water-soluble lanthanide metal salt are preferably zinc nitrate, zirconium nitrate, and cerium nitrate in this order.

In the present invention, the water-soluble group IIB metal salt, the water-soluble group IVB metal salt and the water-soluble lanthanide metal salt are used in a molar ratio of 1 (1-6) to 0.1-1, more preferably 1 (2-5) to 0.2-0.8, and most preferably 1 (3-4) to 0.4-0.6, based on the amount of the group IIB metal ion, the amount of the group IVB metal ion and the amount of the lanthanide metal ion, respectively. In the present invention, the water is preferably deionized water. In the invention, the concentration of the IIB group metal ions in the composite metal ion solution is preferably 0.003-0.3 mol/L, more preferably 0.01-0.2 mol/L, and most preferably 0.05-0.15 mol/L; the concentration of the IVB group metal ions is preferably 0.01-0.6 mol/L, more preferably 0.1-0.5 mol/L, and most preferably 0.2-0.4 mol/L; the concentration of the lanthanide metal ion is preferably 0.001-0.2 mol/L, more preferably 0.01-0.15 mol/L, and most preferably 0.04-0.10 mol/L.

In the invention, the complexing agent preferably comprises one or more of glucose, citric acid, tartaric acid, salicylic acid and adipic acid; when the complexing agent is a mixed complexing agent of two or more, the mass ratio of different complexing agents is not particularly limited in the invention, and any ratio can be adopted. In the invention, the molar ratio of the composite metal ions to the complexing agent in the composite metal ion solution is preferably 1: 0.75-1: 5, more preferably 1: 1-1: 4, and most preferably 1: 2-1: 3.

In the invention, the heating and mixing temperature is preferably 60-95 ℃, more preferably 65-90 ℃, and most preferably 70-80 ℃; the heating and mixing time is preferably 1-15 hours, more preferably 3-10 hours, and most preferably 4-8 hours. In the present invention, the heating and mixing method is preferably stirring and mixing under heating conditions, and the stirring and mixing speed and time in the present invention are not particularly limited, and the raw materials can be uniformly mixed by using the stirring speed and time known to those skilled in the art. In the present invention, during the heating and mixing process, the metal ions are bridged to form a coordination complex under the action of the complexing agent.

After obtaining the colloidal substance, the invention roasts the colloidal substance to obtain the composite metal oxide.

In the present invention, it is preferable that the colloidal substance is dried before the firing. In the invention, the drying temperature is preferably 40-150 ℃, more preferably 60-130 ℃, and most preferably 80-120 ℃; the drying time is preferably 3-15 h, more preferably 5-12 h, and most preferably 6-10 h. The device used for drying is not particularly limited, and is specifically an oven.

In the invention, the roasting temperature is preferably 400-700 ℃, more preferably 450-650 ℃, and most preferably 500-600 ℃; the roasting time is preferably 1-20 hours, more preferably 4-10 hours, and most preferably 5-8 hours; the roasting atmosphere is preferably air; during the calcination process, the complexing agent is removed by combustion.

After the calcination, the present invention preferably cools the calcined product to room temperature to obtain a composite metal oxide. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be used, specifically, natural cooling.

After the composite metal oxide is obtained, the composite metal oxide and the hydrogen type RUB-13 molecular sieve are mixed to obtain the modified molecular sieve composite catalyst.

In the present invention, the mass ratio of the complex metal oxide to the hydrogen type RUB-13 molecular sieve is preferably 1:0.25 to 1:4, and more preferably 1:2.

In the present invention, the mixing is preferably mechanical mixing, more preferably milling mixing. In the invention, the raw materials are uniformly mixed after grinding and mixing.

After the mixing, the invention preferably further comprises the steps of tabletting, crushing and screening the composite catalyst obtained by mixing in sequence. The present invention is not particularly limited with respect to the specific procedures of tabletting, crushing and sieving, and the procedures of tabletting, crushing and sieving known to those skilled in the art may be employed. In the present invention, the pressure of the tablet is preferably 8 to 25MPa, and more preferably 10 MPa. In the invention, the particle size of the modified molecular sieve composite catalyst is preferably 20-40 meshes.

The preparation method provided by the invention is simple to operate, low in cost, green and environment-friendly by taking water as a solvent, free of secondary pollution and suitable for industrial production.

The invention also provides the application of the modified molecular sieve composite catalyst in the technical scheme or the modified molecular sieve composite catalyst prepared by the preparation method in the technical scheme in preparation of propylene and butylene through carbon dioxide hydrogenation.

In the invention, the application of the modified molecular sieve composite catalyst in the preparation of propylene and butylene by carbon dioxide hydrogenation comprises the following steps:

catalysis of H with modified molecular sieve composite catalyst₂/CO₂The mixed gas is hydrogenated to obtain propylene and butylene, and H is₂And CO₂The volume ratio of (a) is preferably 1:1 to 8:1, more preferably 2:1 to 7:1, and most preferably 3:1 to 6: 1; the space velocity of the mixed gas is preferably 800-10000 mL/(h.g), more preferably 1000-9000 mL/(h.g), and most preferably 3000-5000 mL/(h.g); the temperature of the hydrogenation reaction is preferably 260-400 ℃, more preferably 300-380 ℃, and most preferably 320-360 ℃; the time of the hydrogenation reaction is preferably 20-1000 h, and more preferably 30-500 h; the pressure of the hydrogenation reaction is preferably 0.1-5 MPa, and more preferably 1-4 MPa.

In the invention, the modified molecular sieve composite catalyst is preferably subjected to reduction treatment before application; the reduction treatment is preferably carried out in H₂Is carried out in the atmosphere; the temperature of the reduction treatment is preferably 350-450 ℃, more preferably 400 ℃, and the time is preferably 1-4 hours, more preferably 2-3 hours.

In the invention, the number of carbon atoms of the low-carbon olefin is preferably 2 to 4, and more preferably 3 to 4. Compared with the traditional catalyst, the composite catalyst provided by the invention has the advantage of higher CO₂The conversion rate and the yield of the low-carbon olefin (ethylene + propylene + butylene) are improved, the selectivity of the propylene and the butylene can be greatly improved, namely, the generation of the ethylene is effectively inhibited, while the traditional catalyst can only generate the ethylene + the propylene + the butylene, the yield is low, and the generation of the ethylene cannot be selectively inhibited.

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.