Catalyst for preparing low-carbon olefin by directly hydrogenating mixed gas of CO and CO2 as well as preparation and application of catalyst

Abstract

The invention discloses a catalyst for preparing low-carbon olefin by directly hydrogenating mixed gas of CO and CO2 as well as preparation and application of the catalyst. The catalyst comprises a metal oxide and a molecular sieve compound which have catalytic activity in preparation of low-carbon olefin by direct hydrogenation of CO and CO2 mixed gas, the molecular sieve compound is of an SAPO (at) MO core-shell structure with an SAPO molecular sieve as a core and an inert oxide MO as a shell. The catalyst is used for preparing low-carbon olefin through direct hydrogenation of CO and CO2 mixed gas, the conversion efficiency of carbon monoxide can be remarkably improved, the high selectivity of olefin is kept, and the selectivity of carbon dioxide is reduced.

Description

Technical Field

[0001] The present invention relates to a catalyst for preparing light olefins, and in particular to a catalyst for preparing light olefins by direct hydrogenation of a CO and CO2 mixed gas, and the preparation and application of the catalyst. Background Art

[0002] Olefins are the most important basic chemical raw materials. ＝ -C4 ＝ , ethylene, propylene and butene) can be used to prepare a variety of chemical raw materials and products, affecting all aspects of people's daily lives. With the rapid development of the economy and the progress of society, the demand for olefin raw materials is increasing. The traditional route to produce olefins mainly relies on petroleum resources, but due to the limitation of raw material sources, it is urgent to develop non-petroleum route technologies.

[0003] Through the coal chemical process, a route for coal-to-olefins can be opened up. Through the water-gas conversion technology, coal resources can be converted into carbon monoxide, water, carbon dioxide and hydrogen, etc. Among them, carbon monoxide hydrogenation (synthesis gas) is an important platform for C1 conversion. The production of low-carbon olefins by carbon monoxide hydrogenation can be traced back to the Fischer-Tropsch synthesis process developed in Germany in the 1920s. The process uses supported iron or cobalt as a catalyst and can efficiently convert synthesis gas. CN103157489A discloses a catalyst for direct production of low-carbon olefins from synthesis gas and its preparation method and application. Fe and auxiliary agents are highly dispersed on the surface of the alkaline carrier by coprecipitation. During the carbon monoxide hydrogenation process, the CO per-pass conversion rate can reach 75-85%, and the weight of olefins in the organic product reaches 50-60%. However, due to the limitations of the reaction characteristics of the Fischer-Tropsch synthesis process itself, the product distribution of low-carbon olefins produced by this process is often wide (ASF), and the single selectivity of olefins is not high. Subsequently, the methanol synthesis catalyst (oxide) is coupled with the methanol conversion catalyst (SAPO molecular sieve) to achieve the purpose of direct and efficient conversion of synthesis gas. FENG JIAO et al. (Science. 2016, 351, 1065) studied an OX-ZEO process, through which the selectivity of carbon monoxide hydrogenation was as high as 94% (olefins 80%, alkanes 14%), and methane was only 2%, with a CO conversion rate of 17%. Although syngas can be directly converted to produce low-carbon olefins, a large amount of CO2 will be generated during the syngas conversion process. Direct separation and discharge of carbon dioxide will increase CO2 emissions in the atmosphere, which will not only aggravate the greenhouse effect, but also cause a huge waste of carbon resources. Professor Wang Ye of Xiamen University (ACS Catal. 2020, 10, 8303–8314) used ZnGa2O4 metal oxide coupled with SAPO-34 molecular sieve to form a bifunctional catalyst, achieving a CO2 conversion rate of 13% at 370°C and a selectivity of 86% for C2-C4 olefins in organic compounds, and successfully used the separated and enriched CO2 effectively through chemical conversion.

[0004] At present, the main research is on the technology of hydrogenating CO and CO2 to produce olefins, but there is little research on the technology of hydrogenating CO and CO2 mixed gases, because CO2 is a by-product of CO hydrogenation, and too high a concentration will lead to a significant reduction in the CO hydrogenation conversion efficiency and poor catalyst conversion performance. Therefore, it is of great significance to develop a CO and CO2 mixed gas hydrogenation catalyst with high conversion efficiency and achieve efficient conversion of CO and CO2 mixed gas hydrogenation. Summary of the invention

[0005] Based on the defects of the coupled catalyst system in the prior art, such as low reaction activity, low target product selectivity and high by-product selectivity, the present invention provides a catalyst for direct hydrogenation of a CO and CO2 mixture to produce light olefins, as well as its preparation and application. When the catalyst is used for the direct hydrogenation of a CO and CO2 mixture to produce light olefins, it can significantly improve the carbon monoxide conversion efficiency and reduce the carbon dioxide selectivity while maintaining the olefin selectivity.

[0006] The first aspect of the present invention provides a catalyst for the direct hydrogenation reaction of a CO and CO2 mixed gas to produce light olefins, the catalyst comprising a metal oxide and a molecular sieve composite having catalytic activity for the direct hydrogenation of a CO and CO2 mixed gas to produce light olefins; the molecular sieve composite is a SAPO@MO core-shell structure with a SAPO molecular sieve as a core and an inert oxide MO as a shell.

[0007] In the above technical solution, the metal oxide is selected from InZr b Cr y O x 、ZnZr b Cr y O x 、InZr b Al y O x 、InCr b Ce y O x 、ZnZr b Al y O x 、InZr b ZnCr b O x 、InCe b ZnCr b O x 、InZr b O x -InCr b O x 、InAl b O x -InCr b O x 、InCe b O x -ZnCr b O x 、MnAl b O x -InCr b O x 、MnZr b O x -InCr b O x 、CoAlb O x -InCr b O x and FeAl b O x -InCr b O x At least one of the following, wherein b=1 / 4 to 3 / 1, y=1 / 4 to 3 / 1; preferably, the metal oxide is selected from InZr b Cr y O x 、ZnZr b Cr y O x 、InZr b ZnCr b O x 、InCe b ZnCr b O x and InZr b O x -InCr b O x At least one of the following, wherein b=1 / 4 to 3 / 1, y=1 / 4 to 3 / 1.

[0008] In the above technical solution, the metal oxide is selected from InZr b Cr y O x 、ZnZr b Cr y O x 、InZr b Al y O x 、InCr b Ce y O x 、ZnZr b Al y O x 、InZr b ZnCr b O x 、InCe b ZnCr b O x 、InZr b O x -InCr b O x 、InAl b O x -InCr b O x 、InCe b O x -ZnCr bO x 、MnAl b O x -InCr b O x 、MnZr b O x -InCr b O x 、CoAl b O x -InCr b O x and FeAl b O x -InCr b O x When there are multiple types of metal oxides, b in different types of metal oxides may be the same or different, y in different types of metal oxides may be the same or different, and x in different types of metal oxides may be the same or different.

[0009] In the above technical solution, the SAPO molecule is selected from one or more of SAPO-14, SAPO-17, SAPO-18, SAPO-34, SAPO-35, SAPO-42, SAPO-44, SAPO-47, and SAPO-56. The inert oxide MO is selected from one or more of B2O3, SiO2, Al2O3, TiO2, ZrO2, kaolin, and montmorillonite, preferably one or more of B2O3, SiO2, and Al2O3.

[0010] In the above technical solution, in the molecular sieve, the weight ratio of SAPO molecular sieve to inert oxide MO is 1000:1 to 2:1, preferably 100:1 to 5:1, and more preferably 50:1 to 10:1.

[0011] In the above technical solution, in the molecular sieve, the silicon-aluminum molar ratio SiO2 / Al2O3 of the SAPO molecular sieve is 0.001-0.60, preferably 0.01-0.40, and more preferably 0.05-0.20; in the catalyst, the mass ratio of the metal oxide to the molecular sieve composite is 1:8-8:1, preferably 1:3-3:1.

[0012] The second aspect of the present invention provides a method for preparing the above catalyst, comprising the following steps:

[0013] (1) uniformly mixing a phosphorus source, an aluminum source, a silicon source, a template and water, adding a seed crystal to obtain a SAPO molecular sieve synthesis mixed gel, and subjecting the mixture to a hydrothermal crystallization treatment to obtain a SAPO molecular sieve raw powder;

[0014] (2) mixing the inert oxide MO precursor with the SAPO molecular sieve raw powder obtained in step (1), and optionally performing a hydrothermal treatment to obtain a SAPO@MO core-shell structured molecular sieve composite;

[0015] (3) Mixing the metal oxide with the molecular sieve complex obtained in step (1) to obtain the catalyst.

[0016] In the above technical scheme, in step (1), the phosphorus source is selected from one or more of phosphoric acid, phosphorous acid, phosphates and phosphorus oxides; the silicon source is selected from silica sol, silica gel, silicate, water glass, and tetraethyl orthosilicate; the aluminum source is selected from one or more of pseudoboehmite, boehmite, aluminum sol, aluminum isopropoxide, tert-butyl aluminum, aluminate, and activated alumina; and the template agent is selected from one or more of tetraethylammonium hydroxide, triethylamine, diethylamine, N,N-diisopropylethylamine, morpholine, cyclohexylamine, n-propylamine, isopropylamine, di-n-propylamine, diisopropylamine, tripropylamine, n-butylamine or isobutylamine.

[0017] In the above technical scheme, the molar ratio of the mixed gel in step (1) is SiO2:Al2O3:P2O5:template:H2O is (0.001-0.40):1:(0.85-1.25):(1.5-3.0):(20-100), the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P2O5.

[0018] In the above technical solution, the seed crystal in step (1) is a solid powder of the molecular sieve corresponding to the core or a pre-crystallization mother liquor, and the proportion of alumina in the seed crystal to the aluminum source in step (1) calculated as alumina is 1.0wt%-20wt%.

[0019] In the above technical solution, the crystallization conditions in step (1) are: crystallization temperature is 120-210° C., and crystallization time is 12-72 hours. Stirring or standing.

[0020] In the above technical solution, conventional post-treatment steps such as separation, washing, drying and calcination can be adopted after crystallization in step (1), wherein the separation, washing, drying and calcination processes can adopt conventional methods, such as separation can be carried out by centrifugal separation, washing can be carried out by washing with deionized water, and drying can be carried out in an oven. For example, the drying conditions are: drying at 20-120°C for 2-24 hours; the calcination conditions are calcination at 420-650°C for 1-6 hours.

[0021] In the above technical scheme, the inert oxide MO precursor in step (2) can be a soluble compound, for example, the SiO2 precursor can be one or more of silica sol, sodium silicate solution, and tetraethyl silicate; the Al2O3 precursor can be one or more of aluminum sol, aluminum isopropoxide, and aluminum tert-butoxide; the ZrO2 precursor can be zirconium nitrate, the B2O3 precursor can be boric acid, and the TiO2 precursor can be tetrabutyl titanate. In step (2), the preparation method of the SAPO@MO core-shell structured molecular sieve composite can adopt a conventional coating method, such as a surface deposition method, a sol coating method, etc.

[0022] In the above technical solution, in step (2), the weight ratio of the SAPO molecular sieve to the inert oxide MO precursor is 1000:1 to 2:1, preferably 100:1 to 5:1, and more preferably 50:1 to 10:1, calculated as oxide.

[0023] In the above technical solution, the hydrothermal treatment conditions in step (2) are: standing and crystallizing at 120-210° C. for 12-72 hours.

[0024] In the above technical scheme, after the hydrothermal treatment in step (2), the SAPO@MO core-shell structure is obtained by cooling, separation and drying. The separation and drying are conventional operations in the art, for example, separation can be performed by centrifugal separation. The drying conditions are: drying at 20 to 120°C for 2 to 24 hours.

[0025] In the above technical solution, the metal oxide in step (3) can be prepared by conventional methods, such as metal oxide InZr b Cr y O x or InZr b ZnCr b O x The precursor of the metal oxide is prepared by precipitation in solution, separated, dried and then calcined to obtain the metal oxide; the metal oxide InZr b O x -InCr b O x InZr was first prepared by precipitation in solution. b O x and InCr b O x , and then prepared by physical mixing method.

[0026] The third aspect of the present invention provides a method for directly hydrogenating a mixture of CO and CO2 to produce light olefins, wherein the CO / CO2 / H2 mixture is contacted with the catalyst provided above to react to obtain a product containing light olefins.

[0027] In the above technical solution, the catalyst needs to be reduced before the reaction, and the reducing gas is hydrogen. The reduction conditions are as follows: the pressure is normal pressure, the temperature is 350-450°C, and the time is 1-5 hours.

[0028] In the above technical scheme, the reaction conditions are as follows: reaction temperature 320-500°C, reaction pressure 0.5-8MPa, volume space velocity 1000-9600h -1 , the volume ratio of CO to CO2 is 0.1~10.0, and the volume ratio of CO to H2 is 0.5~5.0.

[0029] The inventors have found through research that when a catalyst comprising a metal oxide having catalytic activity for the direct hydrogenation reaction of a CO and CO2 mixed gas and a SAPO@MO core-shell structured molecular sieve composite is used for the direct hydrogenation reaction of a CO and CO2 mixed gas to produce light olefins, the carbon monoxide conversion efficiency can be significantly improved, and the olefin selectivity can be maintained at a high level while the carbon dioxide selectivity can be reduced. The catalyst preparation method of the present invention is simple, the raw materials are cheap and readily available, and the preparation cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the XRD pattern of the SAPO-34@Al2O3 core-shell structure obtained in Example 1;

[0031] Figure 2 This is the SEM image of the SAPO-34@Al2O3 core-shell structure obtained in Example 1. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below by way of examples, but the protection scope of the present invention is not limited by the examples. In the present invention, wt% refers to mass fraction.

[0033] In the present invention, the test conditions of XRD and SEM are as follows:

[0034] XRD test conditions: The molecular sieve crystal phase analysis was performed using a Rigaku-Ultima X-ray diffractometer from Japan. CuKα radiation, wavelength λ = 0.15432nm. The X-ray diffraction pattern scanning range was 2θ5-50°, and the scanning speed was 10° / min.

[0035] SEM test conditions: Japan Hitachi S4800 field emission scanning electron microscope was used for testing.

[0036] In the present invention, the components after the reaction are separated and quantitatively analyzed by gas chromatography, and the calculation formula of CO conversion rate and C2-C4 olefin selectivity is:

[0037] CO conversion rate = (CO content in syngas feedstock - CO content in reaction product) / CO content in syngas feedstock × 100%, by volume;

[0039] CO2 selectivity generated by CO conversion = moles of CO converted to CO2 / total moles of CO converted × 100%;

[0040] C2-C4 olefin selectivity = moles of CO converted to C2-C4 olefins / (total moles of CO converted - moles of CO converted to CO2) x 100%.

[0041] [Example 1]

[0042] (1) InZr b Cr y O x The mixed oxides were prepared as follows:

[0043] Weigh a certain amount of zirconium nitrate, chromium nitrate and indium nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Cr at 4 / 1 / 1, and stir until completely dissolved; weigh a certain amount of (NH4)2CO3 solid and dissolve it in water to prepare a 0.1 mol / L solution. Add the two aqueous solutions to the beaker at the same time for co-precipitation, filter and wash after precipitation, dry at 100°C overnight, and calcine at 500°C for 4h.

[0044] (2) SAPO-34 molecular sieve was prepared according to the following steps:

[0045] Phosphoric acid, pseudoboehmite, silica sol and triethylamine (TEA) are used as phosphorus source, aluminum source, silicon source and template respectively, with a molar ratio of SiO2:Al2O3:P2O5:TEA:H2O=0.10:1:0.95:3:50. After stirring at room temperature (25°C) for 1 hour, SAPO-34 molecular sieve is added as seed (the alumina content in the seed accounts for 10.0wt% of the total alumina in the feed), and after stirring evenly, the mixture is allowed to stand at 170°C for crystallization for 24 hours. The obtained solid is washed with deionized water until neutral, the solid is separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-34 molecular sieve (SiO2 / Al2O3 molar ratio is 0.10) powder.

[0046] (3) SAPO-34@Al2O3 core-shell structure was prepared by the following steps:

[0047] 2.5 g aluminum sol (Al2O3 20 wt%) was dispersed in 18.0 g water and stirred to disperse evenly; 9.5 g SAPO-34 molecular sieve was added to the above mixture and stirred evenly; the mixture was allowed to stand at 120°C for crystallization for 24 h, cooled, centrifuged and dried to obtain SAPO-34@Al2O3 core-shell structure, whose XRD pattern is shown in Figure 1 As shown in the SEM image Figure 2 shown.

[0048] (4) Catalyst preparation and reaction:

[0049] SAPO-34@Al2O3 core-shell structure powder and metal oxide InZr b Cr y O x The metal oxide-molecular sieve bifunctional catalyst is formed by physically mixing in a mass ratio of 1:1, tableting and crushing to 20-40 mesh. The catalyst composition is shown in Table 1.

[0050] The catalyst was evaluated in a fixed bed microreactor. The reactor was a stainless steel reactor lined with a quartz tube. The catalyst was first reduced with pure hydrogen at atmospheric pressure and 400°C for 2 hours, then switched to a mixture of carbon dioxide and hydrogen (CO:CO2:H2=3:1:3) at 390°C, 4.0MPa, 5000h. -1 The reaction was carried out for 20 hours under the condition of space velocity, and the reaction product was monitored online by gas chromatography. The reaction results are shown in Table 2.

[0051] [Example 2]

[0052] (1) InZr b Cr y O x The mixed oxides were prepared as follows:

[0053] Weigh a certain amount of zirconium nitrate, chromium nitrate and indium nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Cr at 3 / 1 / 1, and stir until completely dissolved; weigh a certain amount of (NH4)2CO3 solid and dissolve it in water to prepare a 0.1 mol / L solution. Add the two aqueous solutions to the beaker at the same time for co-precipitation, filter and wash after precipitation, dry at 100°C overnight, and calcine at 500°C for 4 hours.

[0054] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0055] (3) SAPO-34@Al2O3 core-shell structure was prepared according to [Example 1].

[0056] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0057] [Example 3]

[0058] (1) InZr b Cr y O xThe mixed oxides were prepared as follows:

[0059] Weigh a certain amount of zirconium nitrate, chromium nitrate and indium nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Cr at 2 / 1 / 1, and stir until completely dissolved; weigh a certain amount of (NH4)2CO3 solid and dissolve it in water to prepare a 0.1 mol / L solution. Add the two aqueous solutions to the beaker at the same time for co-precipitation, filter and wash after precipitation, dry at 100°C overnight, and calcine at 500°C for 4 hours.

[0060] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0061] (3) SAPO-34@Al2O3 core-shell structure was prepared according to [Example 1].

[0062] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0063] [Example 4]

[0064] (1) InZr b Cr y O x The mixed oxides were prepared as follows:

[0065] Weigh a certain amount of zirconium nitrate, chromium nitrate and indium nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Cr at 1 / 1 / 1, and stir until completely dissolved; weigh a certain amount of (NH4)2CO3 solid and dissolve it in water to prepare a 0.1 mol / L solution. Add the two aqueous solutions to the beaker at the same time for co-precipitation, filter and wash after precipitation, dry at 100°C overnight, and calcine at 500°C for 4 hours.

[0066] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0067] (3) SAPO-34@Al2O3 core-shell structure was prepared according to [Example 1].

[0068] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0069] [Example 5]

[0070] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0071] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0072] (3) SAPO-34@SiO2 molecular sieve was prepared according to the following steps:

[0073] Disperse 1.25g silica sol (SiO2 content 40wt%) in 20g water and stir to disperse evenly; add 9.5g SAPO-34 molecular sieve to the above solution and stir to mix evenly; add a small amount of dilute acetic acid solution (HAc content 5%) to adjust the pH value of the mixed solution to 5-7; let the mixed solution stand at 120°C for crystallization for 24h, cool, centrifuge and dry to obtain a SAPO-34@SiO2 core-shell structure.

[0074] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0075] [Example 6]

[0076] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0077] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0078] (3) SAPO-34@B2O3 core-shell structure was prepared according to the following steps:

[0079] Disperse 0.9g of boric acid (H3BO3) in 20g of water and stir to disperse evenly; add 9.5g of SAPO-34 molecular sieve to the above solution and stir to mix evenly; add a small amount of dilute ammonia solution (NH3 concentration 5%) to adjust the pH value of the mixed solution to 5-7; let the mixed solution stand at 120°C for crystallization for 24h, and then cool and directly dry to obtain a SAPO-34@B2O3 core-shell structure.

[0080] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0081] [Example 7]

[0082] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0083] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0084] (3) SAPO-34@Al2O3 core-shell structure was prepared according to [Example 1].

[0085] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0086] [Example 8]

[0087] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0088] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0089] (3) SAPO-34@Al2O3 core-shell structure was prepared according to [Example 1].

[0090] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0091] [Example 9]

[0092] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0093] (2) SAPO-18 molecular sieve is prepared according to the following process:

[0094] Phosphoric acid, aluminum isopropoxide, silica sol and tetraethylammonium hydroxide (TEAOH) are used as phosphorus source, aluminum source, silicon source and template respectively, with a molar ratio of SiO2:Al2O3:P2O5:TEA:H2O=0.10:1:2.0:4.0:50. After stirring at room temperature for 1 hour, SAPO-18 molecular sieve is added as seed (the alumina content in the seed accounts for 10.0wt% of the total alumina in the feed). After stirring evenly, the mixture is allowed to stand at 170°C for crystallization for 24 hours. The obtained solid is washed with deionized water until neutral, the solid is separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-18 molecular sieve (SiO2 / Al2O3 molar ratio is 0.10) powder.

[0095] (3) SAPO-18@Al2O3 core-shell structure was prepared according to [Example 1].

[0096] 2.5g aluminum sol (Al2O3 wt-20%) was dispersed in 18.0g water and stirred to disperse evenly; 9.5g SAPO-18 molecular sieve was added to the above mixture and stirred evenly; the mixture was allowed to stand at 120°C for crystallization for 24h, cooled, centrifuged and dried to obtain SAPO-18@Al2O3 core-shell structure.

[0097] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0098] [Example 10]

[0099] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0100] (2) SAPO-17 molecular sieve is prepared according to the following process:

[0101] Phosphoric acid, aluminum isopropoxide, silica sol and cyclohexylamine (CHA) are used as phosphorus source, aluminum source, silicon source and template respectively, with a molar ratio of SiO2:Al2O3:P2O5:CHA:H2O=0.10:1:0.95.0:1.2:50. After stirring at room temperature for 1 hour, SAPO-17 molecular sieve is added as seed (the alumina content in the seed accounts for 10.0wt% of the total alumina in the feed). After stirring evenly, the mixture is allowed to stand at 170°C for crystallization for 24 hours. The obtained solid is washed with deionized water until neutral, the solid is separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-17 molecular sieve (SiO2 / Al2O3 molar ratio is 0.10) powder.

[0102] (3) SAPO-17@Al2O3 core-shell structure was prepared according to [Example 1].

[0103] 2.5 g aluminum sol (Al2O3 20 wt%) was dispersed in 18.0 g water and stirred to disperse evenly; 9.5 g SAPO-17 molecular sieve was added to the mixed solution and stirred evenly; the mixed solution was allowed to stand at 120° C. for crystallization for 24 h, cooled, centrifuged and dried to obtain a SAPO-17@Al2O3 core-shell structure.

[0104] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0105] [Example 11]

[0106] (1) InZr b ZnCr b O x The mixed oxides were prepared as follows:

[0107] Weigh a certain amount of indium nitrate, zirconium nitrate, zinc nitrate and chromium nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Zn / Cr at 1 / 1 / 1 / 1, and stir until completely dissolved; weigh a certain amount of (NH4)2CO3 solid and dissolve it in water to prepare a 0.1 mol / L solution. Add the two aqueous solutions to the beaker at the same time for co-precipitation, filter and wash after precipitation, dry at 100°C overnight, and calcine at 500°C for 4 hours.

[0108] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0109] (3) SAPO-34@Al2O3 molecular sieve was prepared according to [Example 1].

[0110] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0111] [Example 12]

[0112] (1)InCe b ZnCr b O x The mixed oxides were prepared as follows:

[0113] Weigh a certain amount of indium nitrate, cerium nitrate, zinc nitrate and chromium nitrate solids and disperse them in water, keeping the molar ratio of In / Ce / Zn / Cr at 1 / 1 / 1 / 1, and stir until completely dissolved; weigh a certain amount of (NH4)2CO3 solid and dissolve it in water to prepare a 0.1 mol / L solution. Add the two aqueous solutions to the beaker at the same time for co-precipitation, filter and wash after precipitation, dry at 100°C overnight, and calcine at 500°C for 4 hours.

[0114] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0115] (3) SAPO-34@Al2O3 molecular sieve was prepared according to [Example 1].

[0116] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0117] [Example 13]

[0118] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0119] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0120] (3) SAPO-34@TiO2 core-shell structure was prepared according to the following steps:

[0121] 2.1 g of tetrabutyl titanate was dispersed in 20.0 g of tetrabutylammonium hydroxide solution, and the mixture was allowed to stand for crystallization at 120° C. for 24 h. 9.5 g of SAPO-34 molecular sieve was added to the crystallized mixture and stirred evenly. The SAPO-34@TiO2 core-shell structure was obtained after cooling, centrifugation and drying.

[0122] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0123] [Comparative Example 1]

[0124] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0125] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0126] (3) Catalyst preparation and reaction:

[0127] SAPO-34 molecular sieve powder and metal oxide InZr b Cr y O x The metal oxide-molecular sieve bifunctional catalyst is formed by physically mixing in a mass ratio of 1:1, tableting and crushing to 20-40 mesh. The catalyst composition is shown in Table 1.

[0128] The catalyst was evaluated in a fixed bed microreactor. The reactor was a stainless steel reactor lined with a quartz tube. The catalyst was first reduced with pure hydrogen at atmospheric pressure and 400°C for 2 hours, then switched to a mixture of carbon dioxide and hydrogen (CO2:H2=1:1) at 400°C, 3.0Mpa, 2000h. -1 The reaction was carried out for 20 hours under the condition of space velocity, and the reaction product was monitored online by gas chromatography. The reaction results are shown in Table 2.

[0129] [Comparative Example 2]

[0130] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0131] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0132] (3) SAPO-34 / Al2O3 mixed oxide was prepared as follows:

[0133] 0.5 g Al2O3 solid powder and 9.5 g SAPO-34 molecular sieve were placed in a ball mill and ground for 5 min. The resulting solid mixture was named SAPO-34 / Al2O3.

[0134] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0135] [Comparative Example 3]

[0136] (1)InZrO x The mixed oxides were prepared according to the following steps:

[0137] Weigh a certain amount of zirconium nitrate and indium nitrate solids and disperse them in water, keeping the In / Zr molar ratio of 1 / 1, and stir until completely dissolved; weigh a certain amount of (NH4)2CO3 solid and dissolve it in water to prepare a 0.1M solution. Add the two aqueous solutions to the beaker at the same time for co-precipitation. After precipitation, filter and wash, dry at 100℃ overnight, and calcine at 500℃ for 4h.

[0138] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0139] (3) SAPO-34@Al2O3 core-shell structure was prepared according to [Example 1].

[0140] (4) Catalyst preparation and reaction were carried out according to [Example 1]. The catalyst composition is shown in Table 1. The reaction results are shown in Table 2.

[0141] [Comparative Example 4]

[0142] (1) InZr b Cr y O x The mixed oxide was prepared according to [Example 3].

[0143] (2) Catalyst preparation and reaction:

[0144] Al2O3 powder and metal oxide InZr b Cr y O x The catalyst is formed by physically mixing the mixture in a mass ratio of 1:1, tableting and crushing the mixture into 20-40 meshes. The catalyst composition is shown in Table 1.

[0145] The catalyst was evaluated in a fixed bed microreactor. The reactor was a stainless steel reactor lined with a quartz tube. The catalyst was first reduced with pure hydrogen at atmospheric pressure and 400°C for 2 hours, then switched to a mixture of carbon dioxide and hydrogen (CO2:H2=1:1) at 400°C, 3.0MPa, 2000h. -1 The reaction was carried out for 20 hours under the condition of space velocity, and the reaction product was monitored online by gas chromatography. The reaction results are shown in Table 2.

[0146] Table 1

[0147]

[0148]

[0149] Table 2

[0150]

[0151]

[0152] The above describes the specific implementation of the present invention in detail, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the various technical features being combined in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A catalyst for direct hydrogenation of a CO and CO2 mixed gas to produce light olefins, the catalyst comprising a metal oxide and a molecular sieve composite having catalytic activity for direct hydrogenation of a CO and CO2 mixed gas to produce light olefins; the molecular sieve composite is a SAPO@MO core-shell structure with a SAPO molecular sieve as a core and an inert oxide MO as a shell.

2. The catalyst according to claim 1, characterized in that The metal oxide is selected from InZr b Cr y O x 、ZnZr b Cr y O x 、InZr b Al y O x 、InCr b Ce y O x 、ZnZr b Al y O x 、InZr b ZnCr b O x 、InCe b ZnCr b O x 、InZr b O x -InCr b O x 、InAl b O x -InCr b O x 、InCe b O x -ZnCr b O x 、MnAl b O x -InCr b O x 、MnZr b O x -InCr b O x 、CoAl b O x -InCr b O x and FeAl b O x -InCr b O x At least one of the following, wherein b=1 / 4 to 3 / 1, y=1 / 4 to 3 / 1; Preferably, the metal oxide is selected from InZr b Cr y O x 、ZnZr b Cr y O x 、InZr b ZnCr b O x 、InCe b ZnCr b O x and InZr b O x -InCr b O x At least one of the following, wherein b=1 / 4 to 3 / 1, y=1 / 4 to 3 / 1.

3. The catalyst according to claim 1, characterized in that The SAPO molecules are selected from one or more of SAPO-14, SAPO-17, SAPO-18, SAPO-34, SAPO-35, SAPO-42, SAPO-44, SAPO-47, and SAPO-56; And / or, the inert oxide MO is selected from one or more of B2O3, SiO2, Al2O3, TiO2, ZrO2, kaolin, and montmorillonite, preferably one or more of B2O3, SiO2, and Al2O3.

4. The catalyst according to claim 1, characterized in that In the molecular sieve, the weight ratio of SAPO molecular sieve to inert oxide MO is 1000:1 to 2:1, preferably 100:1 to 5:1, and more preferably 50:1 to 10:1; And / or, in the molecular sieve, the silicon-aluminum molar ratio SiO2 / Al2O3 of the SAPO molecular sieve is 0.001 to 0.60, preferably 0.01 to 0.40, more preferably 0.05 to 0.20; And / or, in the catalyst, the mass ratio of the metal oxide to the molecular sieve composite is 1:8 to 8:1, preferably 1:3 to 3:

1.

5. A method for preparing a catalyst according to any one of claims 1 to 4, comprising the following steps: (1) uniformly mixing a phosphorus source, an aluminum source, a silicon source, a template and water, adding a seed crystal to obtain a SAPO molecular sieve synthesis mixed gel, and subjecting the mixture to a hydrothermal crystallization treatment to obtain a SAPO molecular sieve raw powder; (2) mixing the inert oxide MO precursor with the SAPO molecular sieve raw powder obtained in step (1), and optionally performing a hydrothermal treatment to obtain a SAPO@MO core-shell structured molecular sieve composite; (3) Mixing the active component metal oxide with the molecular sieve composite obtained in step (1) to obtain the catalyst.

6. The catalyst according to claim 5, characterized in that In step (1), the phosphorus source is selected from one or more of phosphoric acid, phosphorous acid, phosphates and phosphorus oxides; the silicon source is selected from one or more of silica sol, silica gel, silicate, water glass and tetraethyl orthosilicate; the aluminum source is selected from one or more of pseudoboehmite, boehmite, aluminum sol, aluminum isopropoxide, tert-butyl aluminum, aluminate and activated alumina; the template is selected from one or more of tetraethylammonium hydroxide, triethylamine, diethylamine, N,N-diisopropylethylamine, morpholine, cyclohexylamine, n-propylamine, isopropylamine, di-n-propylamine, diisopropylamine, tripropylamine, n-butylamine or isobutylamine.

7. The preparation method according to claim 5, characterized in that: In step (1), the molar ratio of the mixed gel SiO2:Al2O3:P2O5:template:H2O is (0.001-0.40):1:(0.85-1.25):(1.5-3.0):(20-100), wherein the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P2O5; And / or, in step (1), the ratio of alumina in the seed crystal to the aluminum source in step (1) calculated as alumina is 1.0 wt% to 20 wt%.

8. The preparation method according to claim 5, characterized in that: The crystallization conditions in step (1) are: temperature of 120 to 210° C., time of 12 to 72 hours, stirring or standing; And / or, the hydrothermal treatment conditions in step (2) are: standing and crystallizing at 120-210° C. for 12-72 hours.

9. A method for directly hydrogenating a mixture of CO and CO2 to produce light olefins, comprising: The CO / CO2 / H2 mixed gas is contacted with the catalyst described in any one of claims 1 to 4 to react to obtain a product containing light olefins.

10. The method according to claim 9, characterized in that The reaction conditions are as follows: reaction temperature 320-500°C, reaction pressure 0.5-8MPa, volumetric space velocity of the mixed gas 1000-9600h -1 , the volume ratio of CO to CO2 is 0.1~10.0, and the volume ratio of CO to H2 is 0.5~5.0.

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