Catalyst and method for preparing propylene and butylene through direct conversion of synthesis gas

Abstract

The invention belongs to the technical field of direct preparation of low-carbon olefin from synthesis gas, and particularly relates to a catalyst and a method for preparing propylene and butylene by direct conversion of synthesis gas. The catalyst comprises a component A and a component B, the component A and the component B are compounded together in a mechanical mixing mode, an active component of the component A is a metal oxide, and the component B is an SAPO-14 molecular sieve or a heteroatom modified SAPO-14 molecular sieve. The synthesis gas is used as a reaction raw material, a conversion reaction is carried out on a fixed bed or a moving bed, the reaction process has very high product yield and selectivity, the selectivity of low-carbon olefin can reach 70%-90%, the selectivity of propylene and butylene can reach 60%-80%, the selectivity of propylene and butylene in low-carbon olefin can reach 75%-95%, and the selectivity of propylene and butylene in low-carbon olefin can reach 70%-90%. The ratio of propylene to butylene is 1.5-3.5, and the byproduct methane selectivity is low (lt; and the method has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing light olefins from syngas, and particularly relates to a catalyst and a method for directly converting syngas into propylene and butene. Background Art

[0002] Light olefins refer to olefins with carbon atoms less than or equal to 4. Light olefins represented by ethylene and propylene are very important basic organic chemical raw materials. At present, the production of light olefins mainly adopts the petrochemical route of cracking light hydrocarbons (ethane, naphtha, light diesel). Due to the increasingly scarce global petroleum resources and the long-term high operation of crude oil prices, developing the light olefin industry relying solely on the tubular cracking furnace process with petroleum light hydrocarbons as raw materials will encounter more and more serious raw material problems, and the production processes and raw materials of light olefins must be diversified. Selecting the process of producing olefins from syngas can broaden the sources of raw materials, produce syngas from raw materials such as crude oil, natural gas, coal and renewable materials, and provide an alternative solution for the steam cracking technology based on high-cost raw materials such as naphtha. The direct production of light olefins from syngas in one step is a process in which carbon monoxide and hydrogen are directly converted into light olefins with carbon atoms less than or equal to 4 under the action of a catalyst through the Fischer-Tropsch synthesis reaction. This process does not need to further prepare olefins from syngas through methanol or dimethyl ether like the indirect process, simplifies the process flow, and greatly reduces the investment.

[0003] The direct production of light olefins from syngas through Fischer-Tropsch synthesis has become one of the research hotspots in the development of Fischer-Tropsch synthesis catalysts. In the patent CN1083415A disclosed by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, an iron-manganese catalyst system supported by Group IIA alkali metal oxides such as MgO or high-silica zeolite molecular sieves (or aluminophosphate zeolites), with strong base K or Cs ions as promoters, can obtain relatively high activity (CO conversion rate of 90%) and selectivity (light olefin selectivity of 66%) under the reaction pressure of 1.0 - 5.0 MPa and reaction temperature of 300 - 400 °C for the reaction of syngas to light olefins. In the patent ZL03109585.2 - applied by Beijing University of Chemical Technology, an Fe / activated carbon catalyst with manganese, copper, zinc silicon, potassium, etc. as promoters prepared by the vacuum impregnation method is used for the reaction of syngas to light olefins. Under the condition of no recycle of raw material gas, the CO conversion rate is 96%, and the selectivity of light olefins in hydrocarbons is 68%. In 2012, the team of Professor de Jong from Utrecht University in the Netherlands used Fe supported on inert carriers such as SiC and carbon nanofibers and Fe catalysts modified with promoters such as Na and S, and achieved good progress with a light olefin selectivity of 61%. However, when the conversion rate increases, the selectivity decreases. In the process of directly producing olefins from syngas, due to the raw material CO and H 2is gaseous, and ethylene in the target product has a low boiling point, usually requiring cryogenic separation. If C3-C4 olefin products, namely propylene and butene, which contain three and four carbon atoms respectively, can be obtained with high selectivity, then cryogenic separation is not needed, greatly reducing the energy consumption and cost of separation and having great application value. In the above reports, the catalyst uses metallic iron or iron carbide as the active component, and the reaction follows the chain growth reaction mechanism on the metal surface, with low selectivity of light olefins in the products, and even lower selectivity of C3-C4 olefins.

[0004] Recently, Academician Baoxin He and Researcher Xiulian Pan from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences reported a bifunctional catalyst composed of an alumina-supported ZnCr 2 O 4 oxide and a hierarchical porous SAPO-34 molecular sieve (Jiao et al., Science 351 (2016) 1065-1068). When the CO conversion rate reached 17%, the selectivity of light olefins was 80%, but the selectivity of propylene and butene was still lower than 60%. SUMMARY OF THE INVENTION

[0005] In view of the above problems, the present invention provides a catalyst and a method for directly converting syngas to prepare propylene and butene. The invented catalyst can catalyze the direct conversion of syngas to produce light olefins, and the selectivity of propylene and butene can reach 60-80%.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] On the one hand, the present invention provides a catalyst, which comprises component A and component B. Component A and component B are compounded together in a mechanical mixing manner. The active ingredient of component A is a metal oxide, and component B is a SAPO-14 molecular sieve or a heteroatom-modified SAPO-14 molecular sieve;

[0008] The metal oxide is MnCr y O (x+1.5y) , MnAl y O (x+1.5y) , MnIn y O (x+1.5y) , ZnCr y O (1+1.5y) , ZnAl y O (1+1.5y) , ZnGa y O (1+1.5y) , ZnIn y O (1+1.5y) , In y Al z MnO (x+1.5y+1.5z) , In y Gaz MnO (x+1.5y+1.5z) One or more of the following;

[0009] The value range of x is 1 - 3.5, the value range of y is 0.1 - 10, and the value range of z is 0.1 - 10;

[0010] The specific surface area of the metal oxide is 5 - 150 m 2 / g.

[0011] In the present invention, x, y, and z only represent the relative proportions of the chemical composition of the elements in the metal oxide, and metal oxides with the same proportions are regarded as the same metal oxide.

[0012] Based on the above technical solutions, preferably, the SAPO-14 molecular sieve or heteroatom-modified SAPO-14 molecular sieve has a three-dimensional cage structure, and the heteroatom is one of Ga, Mg, Ge, and Zn; all of them are synthesized by a hydrothermal method.

[0013] Based on the above technical solutions, preferably, the weight ratio between the active ingredient in component A and component B is 0.1 - 20, preferably 0.3 - 5.

[0014] Based on the above technical solutions, preferably, a dispersant is further added to component A, and the metal oxide is dispersed in the dispersant; the dispersant is Al 2 O 3 , SiO 2 , Cr 2 O 3 , ZrO 2 , TiO 2 , Ga 2 O 3 , activated carbon, graphene, carbon nanotubes, or one or more of them.

[0015] Based on the above technical solutions, preferably, in component A, the content of the dispersant is 0.05 - 90 wt%, and the rest is the metal oxide.

[0016] Based on the above technical solutions, preferably, the SAPO-14 molecular sieve or heteroatom-modified SAPO-14 molecular sieve has medium-strong acid characteristics, 0.005 - 0.6 mol / kg; preferably 0.005 - 0.4 mol / kg, more preferably 0.005 - 0.2 mol / kg.

[0017] The acid strength is defined by the NH 3 -TPD peak, including three acidities: weak acid, medium-strong acid, and strong acid;

[0018] This NH 3 -TPD is based on NH3 The desorption peak position, where the position of the desorption peak refers to the test conditions of the ratio of the sample mass w to the carrier gas flow rate f (w / f) = 100 g·h / L and a heating rate of 10 °C / min under standard test conditions, and the TCD records the desorption of NH 3 thermal conductivity signal of, and a desorption curve is plotted. According to the vertex of the curve peak position, the inorganic solid is divided into three acid strengths; weak acid refers to NH 3 acid sites with a desorption temperature less than 245 °C; medium-strong acid is NH 3 acid sites with a desorption temperature in the range of 245 - 500 °C; strong acid is NH 3 acid sites with a desorption temperature greater than 500 °C. The molecular sieve can be synthesized in the laboratory or commercially purchased and meet the requirements of the present invention.

[0019] Using acetone as the probe molecule, 13 the 13C-NMR chemical shift is in the range of 210 - 220 ppm.

[0020] On the other hand, the present invention provides a method for directly converting syngas to prepare propylene and butene, which uses syngas as the reaction raw material and conducts the conversion reaction in a fixed bed or a moving bed, and the catalyst used is the above catalyst;

[0021] Based on the above technical solutions, preferably, the pressure of the syngas is 0.5 - 10 MPa, preferably 1 - 5 MPa; the reaction temperature is 300 - 500 °C, preferably 320 - 450 °C; the space velocity is 300 - 12000 h -1 , preferably 1000 - 9000 h -1 , more preferably 3000 - 9000 h -1 .

[0022] Based on the above technical solutions, preferably, the syngas is a H 2 / CO mixture, and the H 2 / CO ratio is 0.2 - 3.5, preferably 0.3 - 1.5.

[0023] The present invention directly converts syngas to propylene and butene in one step. The selectivity of light olefins can reach 70 - 90%, the selectivity of propylene and butene can reach 60% - 80%, the selectivity of propylene and butene in light olefins can reach 75% - 95%, and the ratio of propylene to butene is between 1.5 - 3.5. At the same time, the selectivity of the by-product methane is low (<12%), and it has good application prospects.

[0024] As a preferred technical solution, the process of directly converting syngas to prepare propylene and butene is carried out under preferred reaction conditions. When the reaction temperature is 320 - 450 °C, the space velocity is 3000 - 9000 h -1 , H2 When the H₂ / CO ratio is 0.3 - 1.5, the selectivities of propylene and butene are 70% - 80%, and the selectivity of by-product methane is <10%.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. Different from the traditional methanol - to - light - olefins technology (abbreviated as MTO), the present invention realizes the direct conversion of syngas into light olefins in one step.

[0027] 2. The present invention has higher selectivities of propylene and butene in the products, which can reach 60% - 80%, greatly improving the technical economy. Moreover, by adjusting the reaction conditions, the ratio of propylene to butene can be varied between 1.5 - 3.5, which is beneficial to coping with the changes in product prices.

[0028] 3. The active - ingredient metal oxide of component A in the catalyst of the present invention has a higher specific surface area and more active sites, which is more conducive to the progress of the catalytic reaction.

[0029] 4. On the one hand, the role of component B in the catalyst of the present invention is to couple with component A to further convert the active gas - phase intermediates generated by component A to obtain propylene and butene. Due to the role of component B in pulling the tandem - reaction equilibrium, it can promote the activation and conversion of syngas by component A and thus improve the conversion rate. On the other hand, SAPO - 14 molecular sieve used as a kind of 8 - ring small - pore molecular sieve in component B of the present invention has a chemical environment and spatial environment suitable for the formation of molecules with 3 - 4 carbon atoms. Therefore, the selectivities of propylene and butene in the products are greatly improved, having a unique shape - selective effect.

[0030] 5. The preparation process of the catalyst of the present invention is simple and the conditions are mild; the reaction process has a high product yield and selectivity. The selectivity of light olefins can reach 70% - 90%, the selectivities of propylene and butene can reach 60% - 80%, the selectivities of propylene and butene in light olefins can reach 75% - 95%, the ratio of propylene to butene is between 1.5 - 3.5, and the product - scheme can be customized according to market needs. At the same time, the selectivity of by - product methane is low (<12%). Specific Embodiments

[0031] The present invention will be further described below through examples, but the scope of the claims of the present invention is not limited by these examples. At the same time, the examples only give some of the conditions for achieving this purpose, but it does not mean that these conditions must be met to achieve this purpose.

[0032] The metal oxide described in the present invention can be obtained by purchasing commercially available metal oxides with a high specific surface area, or can be obtained by the following several methods:

[0033] I. Preparation of Catalyst Component A

[0034] (I) Synthesis of MnCr, MnAl, MnIn, ZnCr, ZnAl, ZnGa, ZnIn, InAlMnO, InGaMnO with High Specific Surface Area by Precipitation Method y O (x+1.5y) 、MnAl y O (x+1.5y) 、MnIn y O (x+1.5y) 、ZnCr y O (1+1.5y) 、ZnAl y O (1+1.5y) 、ZnGa y O (1+1.5y) 、ZnIn y O (1+1.5y) 、In y Al z MnO (x+1.5y+1.5z) 、In y Ga z MnO (x+1.5y+1.5z) :

[0035] Using zinc nitrate, aluminum nitrate, chromium nitrate, manganese nitrate, zirconium nitrate, indium nitrate, cobalt nitrate, and iron nitrate as precursors, they are mixed with ammonium carbonate in water at room temperature (where ammonium carbonate is used as the precipitating agent, and the feeding molar ratio is that ammonium carbonate is in excess or preferably the ratio of ammonium ions to metal ions is 1:1); the above-mentioned mixed solution is aged, then taken out for washing, filtering, and drying, and the obtained solid is calcined in an air atmosphere to obtain metal oxides with a high specific surface area. The specific samples and their preparation conditions are shown in Table 1 below.

[0036] Table 1 Preparation and Performance Parameters of Metal Oxides with High Specific Surface Area

[0037]

[0038]

[0039] (II) Metal Oxides Dispersed by Dispersants

[0040] Using dispersant Al 2 O 3 as the carrier, metal oxides dispersed in Al 2 O 3 are prepared by precipitation deposition method. Taking the preparation of dispersed ZnCr 2 O 4 as an example, commercial Al 2 O 3 (specific surface area is about 20m 2 / g) is pre-dispersed in water as the carrier, and then zinc nitrate and chromium nitrate are used as raw materials and mixed with sodium carbonate precipitating agent at room temperature for precipitation, Zn 2+The molar concentration of is 0.067 M, Zn 2+ , Cr 3+ The molar ratio to the precipitating agent is 1:2:8; then it is aged at 160 °C for 24 hours to obtain Al 2 O 3 supported ZnCr 2 O 4 (The content of the dispersant in component A is 20 wt%). The obtained sample is calcined in air at 500 °C for 1 h, and the product is defined as dispersed oxide 1, and its specific surface area is: 148 m 2 / g.

[0041] In the same way, activated carbon (specific surface area about 1000 m 2 / g) supported ZnCr 2 O 4 oxide (the content of the dispersant in component A is 30 wt%) can be obtained, and the product is defined as dispersed oxide 2. Its specific surface area is successively: 177 m 2 / g.

[0042] II. Preparation of catalyst component B

[0043] SAPO-14 molecular sieve is a kind of 8-ring small-pore molecular sieve, and the size of its slender AFN cage is The sizes of the 8-ring pore openings are respectively

[0044] The medium strong acid described in the present invention can be tested by means of H spectrum of solid nuclear magnetic resonance, NH 3 -TPD, infrared, chemical titration and other methods. However, the testing methods for acidity are not limited to the above testing methods.

[0045] The SAPO-14 molecular sieve or heteroatom-modified SAPO-14 molecular sieve of component B in the present invention can be a commercially available product purchased or a molecular sieve prepared by itself. Here, hydrothermal synthesis is taken as an example.

[0046] (I). The specific preparation process of SAPO-14 molecular sieve is as follows:

[0047] According to SiO 2 : Al 2 O 3 : H 3 PO 4 : IPA: H 2O = 0.1:1.0:1.0:1.38:80 (molar ratio). Weigh the raw materials: tetraethyl orthosilicate, aluminum isopropoxide, phosphoric acid, and deionized water. After mixing at room temperature, gradually add the templating agent isopropylamine (IPA) dropwise. After stirring and aging at 30 °C for 2 h, transfer it to a stainless-steel hydrothermal autoclave, heat it to 200 °C at a rate of 2 °C / min and carry out rotary crystallization for 48 h, quickly cool it to room temperature in a water bath, and repeatedly centrifuge and wash until the pH of the supernatant is 7 at the end of washing. After drying the precipitate at 90 °C for 12 h, calcine it in air at 600 °C for 6 h to obtain the SAPO-14 molecular sieve and label it as fraction 1.

[0048] (II). The specific preparation process of the Ga-SAPO-14 molecular sieve is as follows:

[0049] According to Ga 2 O 3 :SiO 2 :Al 2 O 3 :H 3 PO 4 :IPA:H 2 O = 0.005:0.1:1.0:1.0:1.38:80 (molar ratio). Weigh the raw materials: gallium nitrate, tetraethyl orthosilicate, aluminum isopropoxide, phosphoric acid, and deionized water. After mixing at room temperature, gradually add the templating agent isopropylamine (IPA) dropwise. After stirring and aging at 30 °C for 2 h, transfer it to a stainless-steel hydrothermal autoclave, heat it to 200 °C at a rate of 2 °C / min and carry out rotary crystallization for 48 h, quickly cool it to room temperature in a water bath, and repeatedly centrifuge and wash until the pH of the supernatant is 7 at the end of washing. After drying the precipitate at 90 °C for 12 h, calcine it in air at 600 °C for 6 h to obtain the Ga-SAPO-14 molecular sieve and label it as fraction 2.

[0050] (III). The specific preparation process of the Mg-SAPO-14 molecular sieve is as follows:

[0051] According to MgO:SiO 2 :Al 2 O 3 :H 3 PO 4 :IPA:H 2 O = 0.01:0.1:1.0:1.0:1.38:80 (molar ratio). Weigh the raw materials: magnesium nitrate, tetraethyl orthosilicate, aluminum isopropoxide, phosphoric acid, and deionized water. After mixing at room temperature, gradually add the templating agent isopropylamine (IPA) dropwise. After stirring and aging at 30 °C for 2 h, transfer it to a stainless-steel hydrothermal autoclave, heat it to 200 °C at a rate of 2 °C / min and carry out rotary crystallization for 48 h, quickly cool it to room temperature in a water bath, and repeatedly centrifuge and wash until the pH of the supernatant is 7 at the end of washing. After drying the precipitate at 90 °C for 12 h, calcine it in air at 600 °C for 6 h to obtain the Mg-SAPO-14 molecular sieve and label it as fraction 3.

[0052] (4) The specific preparation process of Ge-SAPO-14 molecular sieve is as follows:

[0053] According to GeO 2 :SiO 2 :Al 2 O 3 :H 3 PO 4 :IPA:H 2 O = 0.01:0.1:1.0:1.0:1.38:80 (molar ratio), weigh the raw materials: germanium oxide, tetraethyl orthosilicate, aluminum isopropoxide, phosphoric acid, deionized water, mix them at room temperature and then dropwise add the template agent isopropylamine (IPA); after stirring and aging at 30 °C for 2 h, transfer to a stainless-steel hydrothermal autoclave, heat to 200 °C at a rate of 2 °C / min and rotate and crystallize for 48 h, quickly cool to room temperature in a water bath, repeatedly centrifuge and wash until the pH of the supernatant is 7 at the end of washing, dry the precipitate at 90 °C for 12 h, and then calcine in air at 600 °C for 6 h to obtain Ge-SAPO-14 molecular sieve and label it as fraction 4.

[0054] (5) The specific preparation process of Zn-SAPO-14 molecular sieve is as follows:

[0055] According to ZnO:SiO 2 :Al 2 O 3 :H 3 PO 4 :IPA:H 2 O = 0.01:0.1:1.0:1.0:1.38:80 (molar ratio), weigh the raw materials: zinc nitrate, tetraethyl orthosilicate, aluminum isopropoxide, phosphoric acid, deionized water, mix them at room temperature and then dropwise add the template agent isopropylamine (IPA); after stirring and aging at 30 °C for 2 h, transfer to a stainless-steel hydrothermal autoclave, heat to 200 °C at a rate of 2 °C / min and rotate and crystallize for 48 h, quickly cool to room temperature in a water bath, repeatedly centrifuge and wash until the pH of the supernatant is 7 at the end of washing, dry the precipitate at 90 °C for 12 h, and then calcine in air at 600 °C for 6 h to obtain Ge-SAPO-14 molecular sieve and label it as fraction 5.

[0056] (6) The specific preparation process of AlPO-14 molecular sieve is as follows:

[0057] According to Al 2 O 3 :H 3 PO 4 :IPA:H 2O = 1.0:1.0:1.38:80 (molar ratio), weigh the raw materials: aluminum isopropoxide, phosphoric acid, deionized water, mix them at room temperature and then dropwise add the template agent isopropylamine (IPA); after stirring and aging at 30 °C for 2 h, transfer to a stainless-steel hydrothermal autoclave, heat up to 200 °C at a rate of 2 °C / min for rotary crystallization for 48 h, quickly cool to room temperature in a water bath, repeatedly centrifuge and wash until the pH of the supernatant is 7 at the end of washing, dry the precipitate at 90 °C for 12 h, and then calcine in air at 600 °C for 6 h to obtain AlPO-14 molecular sieve and label it as fraction 6.

[0058] The detailed preparation parameters are shown in Table 2.

[0059] Table 2 Preparation and performance parameters of molecular sieves with AFN topological structure

[0060]

[0061]

[0062] III. Preparation of catalyst

[0063] Add the required proportions of component A and component B into a container, and use the extrusion force, impact force, shearing force, friction force, etc. generated by the high-speed movement of these materials and / or the container to achieve the purposes of separation, crushing, mixing, etc., and realize the conversion of mechanical energy, thermal energy and chemical energy by adjusting the temperature and carrier gas atmosphere, and further adjust the interaction between different components.

[0064] During the mechanical mixing process, the mixing temperature can be set at 20 - 100 °C, and it can be carried out in an atmosphere or directly in air. The atmosphere is selected from any of the following gases:

[0065] a) Nitrogen and / or inert gas;

[0066] b) A mixture of hydrogen and nitrogen and / or inert gas, where the volume of hydrogen in the mixture is 5 - 50%;

[0067] c) A mixture of CO and nitrogen and / or inert gas, where the volume of CO in the mixture is 5 - 20%;

[0068] d) O 2 A mixture with nitrogen and / or inert gas, where O 2 The volume in the mixture is 5 - 20%, and the inert gas is one or more of helium, argon, neon.

[0069] Mechanical mixing can be carried out in combination with one or more of mechanical stirring, ball milling, shaker mixing, mechanical grinding, specifically as follows:

[0070] Mechanical stirring: In a stirring tank, a stirring rod is used to mix component A and component B. By controlling the stirring time (5 min - 120 min) and rate (30 - 300 revolutions per minute), the mixing degree and relative distance of component A and component B can be adjusted.

[0071] Ball milling: The abrasive and the catalyst are tumbled at high speed in a grinding jar, generating strong impacts and rolling on the catalyst to achieve the effect of dispersing and mixing component A and component B. By controlling the abrasive (the material can be stainless steel, agate, quartz, the size range: 5 mm - 15 mm, the mass ratio to the catalyst: 20 - 100:1), the particle size and relative distance of the catalyst can be adjusted.

[0072] Shaker mixing method: Component A and component B are pre-mixed and loaded into a container; by controlling the reciprocating oscillation or circular oscillation of the shaker, the mixing of component A and component B is achieved; by adjusting the oscillation speed (range: 1 - 70 revolutions per minute) and time (range: 5 min - 120 min), uniform mixing is achieved and their relative distance is adjusted.

[0073] Mechanical grinding method: Component A and component B are pre-mixed and loaded into a container; under a certain pressure (range: 5 kg - 20 kg), through the relative movement of the grinding tool and the mixed catalyst (rate range: 30 - 300 revolutions per minute), the particle size, relative distance of the catalyst are adjusted and uniform mixing is achieved.

[0074] The specific catalyst preparation and its parameter characteristics are shown in Table 3.

[0075] Table 3 Preparation of the catalyst and its parameter characteristics

[0076]

[0077]

[0078] Table 4 Preparation of the comparative catalyst and its parameter characteristics

[0079]

[0080]

[0081] Catalytic reaction examples

[0082] Taking the fixed-bed reaction as an example, but the catalyst is also applicable to a moving-bed reactor. The device is equipped with a gas mass flowmeter and an on-line product analysis chromatograph (the tail gas of the reactor is directly connected to the quantitative valve of the chromatograph for periodic real-time sampling and analysis).

[0083] Put 2 g of the above catalyst into a fixed-bed reactor, use Ar to displace the air in the reactor, and then... in H2 Heat it up to 300 °C in an atmosphere, and then switch to syngas (H 2 / CO molar ratio = 0.2 - 3.5). The pressure of the syngas is 0.5 - 10 MPa. Heat it up to the reaction temperature of 300 - 500 °C, and adjust the space velocity of the reaction feed gas to 300 - 12000 ml / g / h. The product is analyzed by on-line chromatography.

[0084] By changing the temperature, pressure, space velocity, and the H 2 / CO molar ratio in the syngas, the reaction performance can be changed. The selectivity of light olefins (one or more of ethylene, propylene, and butene) in the hydrocarbon products can reach 70 - 90%, the selectivity of propylene and butene can reach 60% - 80%, the selectivity of propylene and butene in the light olefins can reach 75% - 95%, the raw material conversion rate is 10 - 50%, and the ratio of propylene to butene is between 1.5 and 3.5. Since the hydrogenation activity on the catalyst surface is not high, a large amount of methane generation is avoided, and the methane selectivity is low (<12%). Table 5 lists the specific applications of the catalyst and its performance data.

[0085] Table 5 Specific applications of the catalyst and performance data after 20 h of reaction

[0086]

[0087]

[0088] In Comparative Example 1, the molecular sieve in the catalyst used is a commercially available SAPO-34, which has three-dimensional cross channels and an eight-membered ring pore mouth diameter.

[0089] In Comparative Example 2, the molecular sieve in the catalyst used is a commercially available ZSM-5, which has a three-dimensional ten-membered ring topological structure.

[0090] In Comparative Example 3, the molecular sieve in the catalyst used is a commercially available MOR, which has a one-dimensional twelve-membered ring topological structure.

[0091] The reaction results of Comparative Examples 1 - 3 show that molecular sieves with different topological structures significantly modulate the product selectivity. SAPO-34 has pore mouth sizes suitable for C2 - C4 hydrocarbons, but there are more C3 products, and the selectivity of propylene and butene is not high. While the pore mouth size of ZSM-5 is larger and is the products are mainly C4 hydrocarbons and even hydrocarbons with longer carbon chains. Although the pore mouth size of MOR is very large up to it also contains side pockets with eight-membered ring pore mouths, and the pocket depth is shallower than that of SAPO-34, so the main product is ethylene with two carbon atoms.

[0092] The catalyst used in Comparative Example 4 is only the oxide of component A and does not contain the molecular sieve of component B. The reaction conversion rate is very low, and the products are mainly by-products such as dimethyl ether and methane, and almost no propylene or butene is formed.

[0093] The catalyst used in Comparative Example 5 is only the molecular sieve of component B and does not contain the oxide of component A. Since the molecular sieve has no ability to activate CO, the catalytic reaction has almost no activity.

[0094] Comparative Examples 4 and 5 show that the reaction effect is poor when only component A or component B is present, and it does not have the excellent reaction performance described in the present invention at all.

[0095] In Comparative Example 6, the oxide in the catalyst used is a Cu-based oxide. The reaction conversion rate is very low, and the products are mainly by-products such as methane, and the selectivity of C 2 -C 4 hydrocarbons is very low.

[0096] In Comparative Example 7, the oxide in the catalyst used is single-component ZnO, which has large crystal grain size and low specific surface area (<1 m 2 / g), and there is no partially reduced O defect structure on the surface. The reaction conversion rate is very low, and hydrogenation is serious. The main product in the products is methane.

[0097] In Comparative Example 8, the same catalyst as that in Example 1 is used, except that the oxide component further contains 10% FeO component. The reaction products are mainly methane, the selectivity of propylene and butene is very low, and the selectivity of C2-C4 alkanes is also significantly higher than that of the present invention. This is because FeO in the catalyst is reduced during the reaction and then forms iron carbide phase, so the reaction process becomes a traditional Fischer-Tropsch synthesis technical route. The product distribution follows the ASF distribution and no longer meets the requirements of the present invention. The technical effect of the present invention cannot be achieved.

[0098] The reaction results of Comparative Examples 6-8 show that the oxide component in the catalyst used is crucial for preparing high-selectivity light olefins.

[0099] In Comparative Example 9, the molecular sieve of catalyst B is replaced with self-synthesized pure AlPO-14 molecular sieve (Fen 6). Since the medium-strong acid amount in this molecular sieve is about 0.01 mmol / g, its pulling effect on the reaction is very weak, and the products are mainly by-products such as dimethyl ether and methane, and almost no light olefins are formed, which does not meet the excellent reaction performance described in the present invention.

[0100] In Comparative Example 10, the molecular sieve in the catalyst used is SAPO-14 ion-exchanged with Ga(NO 3 ) 3 ions, and the remaining parameters and mixing process, etc. are the same as those of catalyst A.

[0101] The molecular sieve in the catalyst used in Comparative Example 11 was Mg(NO 3 ) 2 ion-exchanged SAPO-14, and the remaining parameters and mixing process were the same as those of Catalyst B.

[0102] The molecular sieve in the catalyst used in Comparative Example 12 was Ge-SAPO-14 with a high doping amount, and the remaining parameters and mixing process were the same as those of Catalyst C.

[0103] It can be seen from the above table that the structure of the molecular sieve, including the topological structure of AFN, its acid strength and acid amount, the doping amount of heteroatoms and whether they are doped into the framework, and the matching between the metal oxide and the molecular sieve are crucial, directly affecting the conversion rate of carbon monoxide and the selectivity of propylene and butene.

[0104] The above embodiments are only the preferred embodiments of the present invention and are not intended to limit the implementation manner. The protection scope of the present invention should be subject to the scope defined by the claims. Based on the above description, other different forms of changes or variations can be made. The obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A catalyst, characterized in that: the catalyst comprises component A and component B, component A and component B are compounded together in a mechanical mixing manner, the active ingredient of component A is a metal oxide, and component B is SAPO-14 molecular sieve or heteroatom-modified SAPO-14 molecular sieve; The metal oxide is MnCr y O (x+1.5y) 、MnAl y O (x+1.5y) 、MnIn y O (x+1.5y) 、ZnCr y O (1+1.5y) 、ZnAl y O (1+1.5y) 、ZnGa y O (1+1.5y) 、ZnIn y O (1+1.5y) 、In y Al z MnO (x+1.5y+1.5z) 、In y Ga z MnO (x+1.5y+1.5z) or more than one of them; the value range of x is 1-3.5, the value range of y is 0.1-10, and the value range of z is 0.1-10; The specific surface area of the metal oxide is 5 - 150 m 2 / g.

2. The catalyst according to claim 1, characterized in that: the heteroatom-modified SAPO-14 molecular sieve is one or more of Ga-SAPO-14, Mg-SAPO-14, Ge-SAPO-14, Zn-SAPO-14.

3. The catalyst according to claim 1, characterized in that: the weight ratio between the active ingredient in component A and component B is 0.1-20.

4. The catalyst according to claim 1, characterized in that: A dispersant is also added to the component A, and the metal oxide is dispersed in the dispersant; the dispersant is one or more of Al 2 O 3 、SiO 2 、Cr 2 O 3 、ZrO 2 、TiO 2 、Ga 2 O 3 、activated carbon, graphene, carbon nanotubes or more than two of them.

5. The catalyst according to claim 1, characterized in that: the SAPO-14 molecular sieve or heteroatom-modified SAPO-14 molecular sieve has the characteristics of medium-strong acid, and the amount of medium-strong acid sites is 0.005-0.6 mol / kg; Among them, medium strong acids correspond to NH 3 -TPD desorption peak top corresponding temperature range is 245 - 500 °C; Using acetone as the probe molecule, 13 C-NMR chemical shift is in the range of 210 - 220 ppm.

6. The catalyst according to claim 4, characterized in that: in component A, the content of the dispersant is 0.05-90 wt%, and the rest is the metal oxide.

7. A method for directly converting syngas to prepare propylene and butene, characterized in that: using syngas as a reaction raw material, carrying out a conversion reaction in a fixed bed or a moving bed, and the catalyst used is the catalyst according to any one of claims 1-6.

8. The method according to claim 7, characterized in that: The pressure of the syngas is 0.5 - 10 MPa; the reaction temperature is 300 - 500 °C; the space velocity is 300 - 12000 h -1 .

9. The method according to claim 7, characterized in that: The molar ratio of the syngas H 2 / CO is 0.2 - 3.5.

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