Catalyst for preparing low-carbon olefin through carbon dioxide hydrogenation as well as preparation and application of catalyst

Abstract

The invention discloses a catalyst for preparing low-carbon olefin through carbon dioxide hydrogenation as well as preparation and application of the catalyst. The catalyst comprises a metal oxide and a modified SAPO molecular sieve, wherein metal in the metal oxide comprises In; the modified SAPO molecular sieve is an SAPO coated AlPO core-shell molecular sieve. When the catalyst disclosed by the invention is used for preparing low-carbon olefin through carbon dioxide hydrogenation, the conversion rate of carbon dioxide can be remarkably improved and the selectivity of carbon monoxide can be reduced while relatively high olefin selectivity is maintained.

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 hydrogenating carbon dioxide, and the preparation and application of the catalyst. Background Art

[0002] With the rapid economic development and social progress, the use of fossil energy has increased dramatically, and the content of carbon dioxide in the atmosphere has increased day by day. As the cheapest and most abundant resource in the carbon family, carbon dioxide emitted into the atmosphere not only exacerbates the greenhouse effect, but also causes a huge waste of carbon resources. Using carbon dioxide emitted from the atmosphere to carry out catalytic hydrogenation to produce high-value chemicals is of great significance for simultaneously solving the two new challenges of climate change and energy crisis facing human society today.

[0003] Olefins are the most important basic chemical raw materials, consisting of low-carbon olefins (C2 ＝ -C4 ＝ , namely ethylene, propylene and butene) can be used to prepare a variety of chemical raw materials and products. The hydrogenation of carbon dioxide to produce low-carbon olefins can be achieved through direct and indirect routes. The direct route is generally considered to be the reduction of carbon dioxide to carbon monoxide through the reverse water gas shift reaction (RWGS), and the carbon monoxide is then hydrogenated to produce low-carbon olefins through the Fischer-Tropsch synthesis reaction; while the indirect route is usually carried out in several different reactors, and the intermediates of the reaction include synthesis gas and / or methanol. Another direct route is to couple the indirect route, where carbon dioxide is hydrogenated on the surface of a metal oxide to form a reaction intermediate, and the reaction intermediate then diffuses into the pores of the molecular sieve for conversion to form olefins. However, due to the high thermodynamic stability of carbon dioxide molecules, it is very challenging to make the catalyst efficiently catalyze the hydrogenation of carbon dioxide to produce olefins. Therefore, although there has been a lot of research on the hydrogenation of carbon dioxide to produce low-carbon olefins, the conversion efficiency is still not high enough. Wang Ye et al. (Catal. Today 2013, 215, 186-193) used ZrO2 as a carrier to load potassium-modified iron-based catalysts. When the carbon dioxide conversion rate was 43%, the olefin selectivity was 63%, among which the high carbon olefin C5 + ＝The selectivity is only 19%, but there are more by-products of carbon monoxide and methane. Tsubaki (catal.commun.2019, 130, 105759) et al. used a bimetallic Fe / Co catalyst. When the carbon dioxide conversion rate was 25.9%, the olefin selectivity was 70.9%, but the by-products of carbon monoxide and methane were still relatively high. Professor Wang Ye of Xiamen University (ACS Catal.2020, 10, 8303-8314) achieved a CO2 conversion rate of 13% and a selectivity of 86% for C2-C4 olefins in organic compounds at 370°C by coupling ZnGa2O4 metal oxide with SAPO-34 molecular sieve to form a bifunctional catalyst; however, there is still a disadvantage that the CO2 conversion rate is still low.

[0004] In summary, the coupled catalyst system can realize the direct conversion of CO2 gas to produce light olefins by hydrogenation, but due to the limitations of the catalyst system, the CO2 conversion rate is low and the olefin selectivity is not high during the reaction, especially the CO selectivity in the product is high. Therefore, it is of great significance to construct a new high-performance coupled catalyst system to achieve efficient conversion of CO2 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 preparing light olefins by hydrogenation of carbon dioxide and its preparation and application. When the catalyst is used in the reaction of preparing light olefins by hydrogenation of carbon dioxide, it can significantly improve the carbon dioxide conversion efficiency and reduce the carbon monoxide selectivity while maintaining the olefin selectivity.

[0006] The first aspect of the present invention provides a catalyst for hydrogenating carbon dioxide to produce light olefins, the catalyst comprising a metal oxide and a modified SAPO molecular sieve, the metal in the metal oxide comprising In; the modified SAPO molecular sieve is a SAPO@AlPO core-shell molecular sieve.

[0007] In the above technical solution, the metal oxide is selected from InCr b Al y O x 、InAl b O x 、InCe b Al y O x 、InZr b Al y O x 、InMn b Al y O x 、InMn b Zr y Ox 、InCo b Al y O x 、InFe b Al y O x or InZr b O x -InAl b O x One or more of, wherein b = 1 / 3 to 3 / 1, y = 1 / 100 to 1 / 5; preferably, the metal oxide is selected from InCr b Al y O x 、InAl b O x 、InCe b Al y O x or InZr b Al y O x One or more of the above, wherein b=1 / 3 to 3 / 1, y=1 / 100 to 1 / 5, preferably b=1 / 3 to 1 / 1, y=1 / 100 to 1 / 10.

[0008] In the above technical solution, the metal oxide is selected from InCr b Al y O x 、InAl b O x 、InCe b Al y O x 、InZr b Al y O x 、InMn b Al y O x 、InMn b Zr y O x 、InCo b Al y O x 、InFe b Al y O x or InZr b O x -InAl 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 scheme, the SAPO@AlPO core-shell molecular sieve comprises a SAPO molecular sieve core and an AlPO molecular sieve shell, wherein the SAPO molecular sieve 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 AlPO molecular sieve is selected from one or more of AlPO-14, AlPO-17, AlPO-18, AlPO-34, AlPO-35, AlPO-42, AlPO-44, AlPO-47, and AlPO-56.

[0010] In the above technical solution, in the modified SAPO molecular sieve, the weight ratio of the SAPO molecular sieve core to the AlPO molecular sieve shell is 1000:1-2:1, preferably 100:1-5:1, more preferably 50:1-10:1, and even more preferably 80:1-15:1.

[0011] In the above technical solution, the silicon-aluminum molar ratio SiO2 / Al2O3 of the SAPO molecular sieve core in the modified SAPO molecular sieve is 0.001 to 0.60, preferably 0.01 to 0.40, and more preferably 0.05 to 0.20.

[0012] In the above technical solution, the mass ratio of the metal oxide to the modified SAPO molecular sieve is 1:8 to 8:1, preferably 1:3 to 3:1.

[0013] The second aspect of the present invention provides a method for preparing the above catalyst, comprising the following steps:

[0014] (1) mixing a phosphorus source, an aluminum source, a silicon source, a template agent and water uniformly to obtain a SAPO molecular sieve synthesis mixed gel;

[0015] (2) subjecting the mixed gel obtained in step (1) to hydrothermal crystallization to obtain SAPO molecular sieve raw powder;

[0016] (3) mixing a phosphorus source, an aluminum source, a template agent and water uniformly to obtain an AlPO molecular sieve synthesis mixed gel;

[0017] (4) adding the SAPO molecular sieve raw powder obtained in step (2) to the AlPO molecular sieve synthetic mixed gel obtained in step (3), and performing a hydrothermal crystallization treatment to obtain a SAPO@AlPO molecular sieve raw powder;

[0018] (5) Mixing the metal oxide with the SAPO@AlPO molecular sieve raw powder obtained in step (4) to obtain the catalyst.

[0019] In the above technical scheme, in the 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 a mixture of 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.

[0020] In the above technical scheme, the molar ratio of the mixed gel in step (1) 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; molecular sieve seeds are added to the mixed gel, the seeds are solid powder of the molecular sieve corresponding to the core or pre-crystallized mother liquor, and the proportion of alumina in the seeds to the aluminum source in step (1) calculated as alumina is 1.0wt% to 20wt%.

[0021] In the above technical solution, the crystallization conditions in step (2) and step (4) are independently selected from: crystallization temperature of 120 to 210° C., time of 12 to 72 hours, stirring or standing.

[0022] In the above technical solution, after crystallization in step (2) and step (4), conventional post-treatment steps such as separation, washing, drying and calcination can be adopted, 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 1-5 hours.

[0023] In the above technical scheme, the molar ratio of the mixed gel in step (3) is Al2O3:P2O5:template:H2O is 1:(0.85-1.25):(1.5-3.0):(20-100), the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P2O5.

[0024] In the above technical solution, the metal oxide in step (4) can be prepared by conventional methods, such as metal oxide InCr b Al y 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 Ox -InAl b O x First, InZr was prepared by precipitation in solution. b O x and InAl b O x and then physically mixed.

[0025] The third aspect of the present invention provides a method for preparing light olefins by hydrogenating carbon dioxide, comprising: contacting carbon dioxide and hydrogen with the above-provided catalyst to react to obtain a product containing light olefins.

[0026] 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.

[0027] In the above technical scheme, the reaction conditions are as follows: reaction temperature 320 ~ 500 ° C, reaction pressure 0.5 ~ 8MPa, CO2 / H2 mixed gas volume space velocity 1000 ~ 9600h -1 , the volume ratio of CO2 to H2 is 1.0~5.0.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The inventors have found through research that when a catalyst including a metal oxide having catalytic activity for the hydrogenation of carbon dioxide to produce light olefins and a SAPO@AlPO core-shell molecular sieve is used for the reaction of hydrogenation of carbon dioxide to produce light olefins, the carbon dioxide conversion efficiency can be significantly improved, and the olefin selectivity can be maintained at a high level while the carbon monoxide 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@AlPO-18 molecular sieve obtained in Example 1;

[0031] Figure 2 is a SEM image of the SAPO-34@AlPO-18 molecular sieve obtained in Example 1;

[0032] Figure 3 This is the silicon element distribution diagram of the SAPO-34@AlPO-18 molecular sieve obtained in Example 1. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below by way of embodiments, but the protection scope of the present invention is not limited by the embodiments.

[0034] In the present invention, wt% refers to mass fraction.

[0035] In the present invention, the test conditions of XRD and SEM are as follows:

[0036] 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.

[0037] SEM test conditions: Japan Hitachi S4800 field emission scanning electron microscope was used for testing.

[0038] In the present invention, the components after the reaction are separated and quantitatively analyzed by gas chromatography, and the calculation formula of CO2 conversion rate and C2-C4 olefin selectivity is:

[0039] CO2 conversion rate = (CO2 content in raw material - CO2 content in reaction product) / CO2 content in raw material × 100%, by volume;

[0040] CO selectivity = moles of CO2 converted to CO / total moles of CO2 converted × 100%;

[0041] C2-C4 olefin selectivity = moles of CO2 converted to C2-C4 olefins / (total moles of CO2 converted - moles of CO2 converted to CO) x 100%.

[0042] [Example 1]

[0043] (1) InZr b Al y O x The mixed oxides were prepared as follows:

[0044] Weigh a certain amount of zirconium nitrate, indium nitrate and aluminum nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / A1 at 5 / 2.5 / 0.2, 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.

[0045] (2) SAPO-34 molecular sieve was prepared according to the following steps:

[0046] Phosphoric acid, pseudo-boehmite, silica sol, and triethylamine (TEA) are used as phosphorus source, aluminum source, silicon source, and template agent, 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 ratio of alumina in the seed to the aluminum source in the feed is 10.0wt%), stirred evenly, and then allowed to stand at 170°C for crystallization for 24 hours. The obtained solid is washed with deionized water until neutral, separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-34 molecular sieve powder. The obtained molecular sieve has a silicon-aluminum molar ratio SiO2 / Al2O3 of 0.10.

[0047] (3) SAPO-34@AlPO-18 core-shell molecular sieve was prepared according to the following steps:

[0048] Phosphoric acid, aluminum isopropoxide, and tetraethylammonium hydroxide (TEAOH) are used as phosphorus source, aluminum source, and template agent, respectively, with a molar ratio of Al2O3:P2O5:TEAOH:H2O=1.0:2.0:4.0:50, and stirred evenly at room temperature (25°C). SAPO-34 molecular sieve powder is added to the above gel, and stirred for 1 hour, and then allowed to stand at 170°C for crystallization for 24 hours, and the solid is separated, dried, and calcined at 550°C in a muffle furnace for 6 hours to obtain SAPO-34@AlPO-18 core-shell molecular sieve powder. The XRD pattern of the obtained SAPO-34@AlPO-18 core-shell molecular sieve powder is shown in the figure. Figure 1 As shown in; the obtained SAPO-34@AlPO-18 core-shell molecular sieve powder SEM Figure 2 The element distribution diagram of the obtained SAPO-34@AlPO-18 core-shell molecular sieve powder is shown in Figure 3 as shown in .

[0049] (4) Catalyst preparation and reaction:

[0050] SAPO-34@AlPO-18 core-shell molecular sieve powder and metal oxide InZr b Al 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.

[0051] 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 volume ratio = 1:1) at 400°C, 3.0 MPa, 2000 h. -1The 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.

[0052] [Example 2]

[0053] (1) InZr b Al y O x The mixed oxides were prepared as follows:

[0054] Weigh a certain amount of zirconium nitrate, indium nitrate and aluminum nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Al at 4 / 3 / 0.2, 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.

[0055] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0056] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0057] (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.

[0058] [Example 3]

[0059] (1) InZr b Al y O x The mixed oxides were prepared as follows:

[0060] Weigh a certain amount of zirconium nitrate, indium nitrate and aluminum nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Al at 1.5 / 3.5 / 0.1, 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 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.

[0061] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0062] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0063] (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.

[0064] [Example 4]

[0065] (1) InZr b Al y O x The mixed oxides were prepared as follows:

[0066] Weigh a certain amount of zirconium nitrate, indium nitrate and aluminum nitrate solids and disperse them in water, keeping the molar ratio of In / Zr / Al at 2 / 4 / 0.2, 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.

[0067] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0068] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0069] (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.

[0070] [Example 5]

[0071] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0072] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0073] (3) SAPO-34@AlPO-17 molecular sieve was prepared according to the following steps:

[0074] Phosphoric acid, aluminum isopropoxide and cyclohexylamine (CHA) are used as phosphorus source, aluminum source and template agent respectively, with a molar ratio of Al2O3:P2O5:CHA:H2O=1.0:1.0:1.2:50. Stir evenly at room temperature, add SAPO-34 molecular sieve powder to the above gel, continue stirring for 1 hour, and then stand at 170°C for crystallization for 24 hours. The solid is separated, dried, and calcined at 550°C in a muffle furnace for 6 hours to obtain SAPO-34@AlPO-17 core-shell molecular sieve powder.

[0075] (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.

[0076] [Example 6]

[0077] (1) InZr b Aly O x The mixed oxide was prepared according to [Example 2].

[0078] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0079] (3) SAPO-34@AlPO-34 molecular sieve was prepared according to the following steps:

[0080] Phosphoric acid, aluminum isopropoxide and triethylamine (TEA) are used as phosphorus source, aluminum source and template respectively, with a molar ratio of Al2O3:P2O5:TEA:H2O=1.0:1.0:3.0:50. The mixture is stirred evenly at room temperature. SAPO-34 molecular sieve powder is added to the above gel. After stirring for 1 hour, the mixture is allowed to stand and crystallize at 170°C for 24 hours. The solid is separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-34@AlPO-34 core-shell molecular sieve powder.

[0081] (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.

[0082] [Example 7]

[0083] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0084] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0085] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0086] (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.

[0087] [Example 8]

[0088] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0089] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0090] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0091] (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.

[0092] [Example 9]

[0093] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0094] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0095] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0096] (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.

[0097] [Example 10]

[0098] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0099] (2) SAPO-18 molecular sieve is prepared according to the following process:

[0100] 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 ratio of alumina in the seed to the aluminum source in the feed as alumina is 10.0wt%). 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, separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-18 molecular sieve powder.

[0101] (3) SAPO-18@AlPO-18 core-shell molecular sieve was prepared according to the following steps:

[0102] Phosphoric acid, aluminum isopropoxide and tetraethylammonium hydroxide (TEAOH) are used as phosphorus source, aluminum source and template respectively, with a molar ratio of Al2O3:P2O5:TEAOH:H2O=1.0:2.0:4.0:50. The mixture is stirred evenly at room temperature. SAPO-18 molecular sieve powder is added to the above gel. After stirring for 1 hour, the mixture is allowed to stand and crystallize at 170°C for 24 hours. The solid is separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-18@AlPO-18 core-shell molecular sieve powder.

[0103] (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.

[0104] [Example 11]

[0105] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0106] (2) SAPO-17 molecular sieve is prepared according to the following process:

[0107] 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 ratio of alumina in the seed to the aluminum source in the feed as alumina is 10.0wt%). 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, separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-17 molecular sieve powder.

[0108] (3) SAPO-17@AlPO-18 core-shell molecular sieve was prepared according to the following steps:

[0109] Phosphoric acid, aluminum isopropoxide and tetraethylammonium hydroxide (TEAOH) are used as phosphorus source, aluminum source and template respectively, with a molar ratio of Al2O3:P2O5:TEAOH:H2O=1.0:2.0:4.0:50. The mixture is stirred evenly at room temperature. SAPO-17 molecular sieve powder is added to the above gel. After stirring for 1 hour, the mixture is allowed to stand and crystallize at 170°C for 24 hours. The solid is separated, dried, and calcined in a muffle furnace at 550°C for 6 hours to obtain SAPO-17@AlPO-18 core-shell molecular sieve powder.

[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) InCr b Al y O x The mixed oxides were prepared as follows:

[0113] Weigh a certain amount of chromium nitrate, indium nitrate and aluminum nitrate solids and disperse them in water, keeping the molar ratio of In / Cr / Al at 2 / 3 / 0.1, 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@AlPO-18 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) InAl b O x The mixed oxides were prepared as follows:

[0119] Weigh a certain amount of indium nitrate and aluminum nitrate solids and disperse them in water, keeping the In / Al molar ratio at 2 / 3, 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, filter and wash after precipitation, dry at 100℃ overnight, and calcine at 500℃ for 4h.

[0120] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0121] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[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] [Example 14]

[0124] (1)InCe b Al y O x The mixed oxides were prepared as follows:

[0125] Weigh a certain amount of indium nitrate, cerium nitrate and aluminum nitrate solids and disperse them in water, keeping the molar ratio of In / CeO2 / Al at 2 / 2 / 0.2, 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.

[0126] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0127] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0128] (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.

[0129] [Example 15]

[0130] (1) InZr b O x -InAl b O x The mixed oxides were prepared as follows:

[0131] InZ b O x Metal oxide: Weigh a certain amount of zirconium nitrate and indium nitrate solids and disperse them in water, keeping the In / Zr molar ratio at 1 / 0.79, 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. After precipitation, filter and wash, dry at 100°C overnight, and calcine at 500°C for 4 hours. The metal oxide In is obtained. 3.8 Zr3O x .

[0132] InAl b O x Metal oxide: Weigh a certain amount of aluminum nitrate and indium nitrate solids and disperse them in water, keeping the In / Al molar ratio at 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. After precipitation, filter and wash, dry at 100°C overnight, and calcine at 500°C for 4h. The metal oxide InAlO is obtained. x .

[0133] InZ b O x -InAl b O xMetal oxide: InZr 0.79 O x Metal oxides and InAlO x The metal oxides were physically mixed in a molar ratio of 19:1 to obtain a blended oxide, and the molar ratio of In / Zr / Al was maintained at 4:3:0.2.

[0134] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0135] (3) SAPO-34@AlPO-18 molecular sieve was prepared according to [Example 1].

[0136] (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.

[0137] [Comparative Example 1]

[0138] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0139] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0140] (3) Catalyst preparation and reaction:

[0141] SAPO-34 molecular sieve powder and metal oxide InZrAlO 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.

[0142] 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.

[0143] [Comparative Example 2]

[0144] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0145] (2) SAPO-34 molecular sieve was prepared according to [Example 1].

[0146] (3) AlPO-18 molecular sieve was prepared according to [Example 1].

[0147] 0.25 g AlPO-18 molecular sieve solid powder was dispersed in 20 g water and stirred to disperse evenly; 9.75 g SAPO-34 molecular sieve was added to the above solution and stirred to mix evenly; after centrifugation, a blended molecular sieve of AlPO-18 and SAPO-34 was obtained, named SAPO-34 / AlPO-18.

[0148] (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.

[0149] [Comparative Example 3]

[0150] (1) InZr b Al y O x The mixed oxide was prepared according to [Example 2].

[0151] (2) AlPO-18 molecular sieve was prepared according to [Example 1].

[0152] (3) Catalyst preparation and reaction:

[0153] AlPO-18 molecular sieve powder and metal oxide InZr b Al 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.

[0154] 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.

[0155] Table 1

[0156]

[0157]

[0158] Table 2

[0159]

[0160]

[0161] 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 preparing low-carbon olefins by hydrogenating carbon dioxide, the catalyst comprising a metal oxide and a modified SAPO molecular sieve, the metal in the metal oxide comprising In; the modified SAPO molecular sieve is a SAPO@AlPO core-shell molecular sieve.

2. The catalyst according to claim 1, characterized in that: The metal oxide is selected from InCr b Al y O x 、InAl b O x 、InCe b Al y O x 、InZr b Al y O x 、InMn b Al y O x 、InMn b Zr y O x 、InCo b Al y O x 、InFe b Al y O x or InZr b O x -InAl b O x One or more of, wherein b = 1 / 3 to 3 / 1, y = 1 / 100 to 1 / 5; preferably, the metal oxide is selected from InCr b Al y O x 、InAl b O x 、InCe b Al y O x or InZr b Al y O x One or more of the above, wherein b=1 / 3 to 3 / 1, y=1 / 100 to 1 / 5, preferably b=1 / 3 to 1 / 1, y=1 / 100 to 1 / 10.

3. The catalyst according to claim 1, characterized in that: The SAPO@AlPO core-shell molecular sieve, wherein the SAPO molecular sieve 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 AlPO molecular sieve is selected from one or more of AlPO-14, AlPO-17, AlPO-18, AlPO-34, AlPO-35, AlPO-42, AlPO-44, AlPO-47, and AlPO-56.

4. The catalyst according to claim 1, characterized in that: The weight ratio of the SAPO molecular sieve core to the AlPO molecular sieve shell in the modified SAPO molecular sieve is 1000:1-2:1, preferably 100:1-5:1, more preferably 50:1-10:1, and even more preferably 80:1-15:

1.

5. The catalyst according to claim 1, characterized in that: The silicon-aluminum molar ratio SiO2 / Al2O3 of the SAPO molecular sieve core in the modified SAPO molecular sieve is 0.001 to 0.60, preferably 0.01 to 0.40, and more preferably 0.05 to 0.20; And / or, the mass ratio of the metal oxide to the modified SAPO molecular sieve is 1:8 to 8:1, preferably 1:3 to 3:

1.

6. A method for preparing a catalyst according to any one of claims 1 to 5, comprising the following steps: (1) mixing a phosphorus source, an aluminum source, a silicon source, a template agent and water uniformly to obtain a SAPO molecular sieve synthesis mixed gel; (2) subjecting the mixed gel obtained in step (1) to hydrothermal crystallization to obtain SAPO molecular sieve raw powder; (3) mixing a phosphorus source, an aluminum source, a template agent and water uniformly to obtain an AlPO molecular sieve synthesis mixed gel; (4) adding the SAPO molecular sieve raw powder obtained in step (2) to the AlPO molecular sieve synthetic mixed gel obtained in step (3) to perform hydrothermal crystallization treatment to obtain SAPO@AlPO molecular sieve raw powder; (5) Mixing the metal oxide with the SAPO@AlPO molecular sieve raw powder obtained in step (4) to obtain the catalyst.

7. The preparation method according to claim 6, 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; and 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.

8. The preparation method according to claim 6, characterized in that: The molar ratio of the mixed gel in step (1) is SiO2:Al2O3:P2O5:template:H2O:(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; molecular sieve seed crystals are added to the mixed gel, and the ratio of aluminum oxide in the seed crystals to the aluminum source in step (1) calculated as aluminum oxide is 1.0wt%-20wt%; And / or, in step (3), the molar ratio of the mixed gel Al2O3:P2O5:template:H2O is 1:(0.85-1.25):(1.5-3.0):(20-100), the aluminum source is calculated as Al2O3, and the phosphorus source is calculated as P2O5.

9. The preparation method according to claim 6, characterized in that: The crystallization conditions in steps (2) and (4) are independently selected from: crystallization temperature of 120 to 210° C., time of 12 to 72 hours, stirring or standing.

10. A method for preparing light olefins by hydrogenating carbon dioxide, comprising: Carbon dioxide and hydrogen are contacted with the catalyst described in any one of claims 1 to 5 to react to obtain a product containing light olefins.

11. The method according to claim 10, characterized in that: The reaction conditions are as follows: reaction temperature 320-500°C, reaction pressure 0.5-8MPa, volume space velocity of CO2 / H2 mixed gas 1000-9600h -1 , the volume ratio of CO2 to H2 is 1.0~5.0.

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