Fe-based catalyst, preparation method and application thereof, and method for water-gas shift reaction

Abstract

The application relates to the technical field of catalysts, and discloses an Fe-based catalyst, a preparation method and application thereof, and a water vapor shift reaction method. The catalyst comprises a substrate and modified elements loaded on the substrate, the substrate comprises Fe, Al, M and O elements, M is selected from at least one of non-Fe transition metals and alkaline earth metals; the substrate has a spinel crystal structure through XRD characterization; the modified elements are selected from at least one of alkali metals; wherein the content of oxygen defects in the catalyst is not less than 30%. The catalyst has high water vapor shift catalytic activity, good water and heat resistance and good sintering resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a Fe-based catalyst, a preparation method and application thereof, and a water vapor shift reaction method. BACKGROUND

[0002] Hydrogen energy is attracting attention as a potential alternative to traditional fossil fuels. Over the past decade, the hydrogen economy has grown rapidly, with a total heat value of 141.8 MJ / kg, which is twice that of natural gas (54.0 MJ / kg), and good economic performance. Although hydrogen resources are abundant, such as water and biomass energy, most of today's hydrogen is extracted from traditional fossil fuels, such as crude oil and natural gas. At present, steam methane reforming (SRM) is the main mature industrial hydrogen production technology. In order to improve hydrogen yield, a water gas shift reaction is required after the reforming process to remove excess CO to further increase the H2 content in the atmosphere, thereby improving hydrogen yield. The water vapor shift reaction also has important applications in the field of new energy vehicles. The electrode material of the fuel cell is mainly composed of Pt, which is easily deactivated in the presence of carbon monoxide. Therefore, the water gas shift reaction is placed before the fuel cell, thereby converting carbon monoxide into hydrogen and CO2 gas. As can be seen, the water gas shift reaction (WGS) has an important industrial role in adjusting and improving the concentration of H2.

[0003] Commercial iron oxide catalysts use chromium oxide as a structural promoter. Cr2O3 / CrO3 not only prevents the sintering of iron oxide crystals as a structural promoter, but also improves the inherent catalytic activity of Fe2O3. Under high-temperature hydrothermal conditions during the reaction, Cr2O3 inhibits the growth of iron oxide grains and avoids a significant reduction in the specific surface area of the catalyst. However, hexavalent chromium is a heavy metal that is toxic to humans, organisms, or cells, and is also a serious environmental pollutant. The water solubility of hexavalent chromium allows it to leach from the catalyst through condensed steam or cold water. The hexavalent chromium (Cr 6+ ) in fresh and waste commercial high-temperature shift Fe-Cr catalysts is very high in cost to treat. Therefore, there is an urgent need to develop a chromium-free catalyst with high stability and high activity.

[0004] CN107649142A discloses the use of Mn, Mg, and Cr as promoters to improve the high-temperature stability of Fe-based catalysts, but still contains a low content of Cr; CN103272600A discloses a hydrothermally synthesized supported copper-iron catalyst, but the hydrothermal reaction time is long and the process is complicated; CN104014345A discloses a Cu / CeO2 catalyst synthesized by deposition precipitation, but the deposition heat consumption is large and the catalyst preparation cost is high.

[0005] Key challenges facing existing water-gas shift reactions include severe methanogenic side reactions, low space-time yields, high catalyst costs, and significant chromium contamination. Therefore, developing chromium-free, highly selective, and simple-to-prepare catalysts while ensuring hydrothermal stability remains a key challenge and key direction for the industrial application of green shift catalysts. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of insufficient heat resistance, poor stability and poor environmental protection of water vapor shift catalysts in the prior art, and to provide an Fe-based catalyst and its preparation method and application, as well as a method for water vapor shift reaction. The catalyst has high stability, high resistance to hydrothermal and sintering, and high activity in catalyzing water vapor shift.

[0007] To achieve the above object, the present invention provides an Fe-based catalyst, comprising a matrix and a modifying element supported on the matrix, wherein the matrix comprises Fe, Al, M, and O elements, wherein M is selected from at least one of a non-Fe transition metal and an alkaline earth metal; XRD characterization shows that the matrix has a spinel crystal structure;

[0008] The modifying element is at least one selected from alkali metals;

[0009] Wherein, the content of oxygen defects in the catalyst is not less than 30%.

[0010] A second aspect of the present invention provides a method for preparing an Fe-based catalyst, comprising the following steps:

[0011] (1) mixing a soluble compound of Fe, a soluble compound of Al, a soluble compound of M, and a solvent to obtain a mixed solution; wherein M is selected from at least one of a non-Fe transition metal and an alkaline earth metal;

[0012] (2) mixing the mixed solution with a complexing agent under stirring to obtain a gel;

[0013] (3) drying and calcining the gel to obtain a matrix;

[0014] Wherein, the calcination temperature does not exceed 400°C;

[0015] (4) A modifying element is loaded on the matrix, wherein the modifying element is at least one selected from alkali metals.

[0016] The third aspect of the present invention provides the use of the Fe-based catalyst described in the first aspect or the Fe-based catalyst prepared by the preparation method described in the second aspect in a water gas shift reaction.

[0017] A fourth aspect of the present invention provides a method for a water gas shift reaction, comprising: contacting a feed gas containing CO, water vapor, and a catalyst under water gas shift reaction conditions to perform a water gas shift reaction;

[0018] Wherein, the catalyst is the Fe-based catalyst described in the first aspect or the Fe-based catalyst prepared by the preparation method described in the second aspect.

[0019] The oxygen defect content in the Fe-based catalyst provided by the present invention is not less than 30%. By controlling the Fe-based spinel catalyst to have a higher oxygen defect, it is beneficial to improve the catalytic activity and heat-resistant activity of the catalyst in the water vapor shift reaction. Further, the surface modification is performed using an alkali metal, which can have high stability, high hydrothermal resistance and sintering resistance, and high activity in catalyzing water vapor shift. The preparation method provided by the present invention forms a uniformly dispersed precursor by complexation, and forms a spinel-type catalyst with certain oxygen defects by controlling the roasting temperature and doping metal. In a preferred embodiment, the catalyst has a fluffy, porous, uneven spinel surface and a high specific surface area, which can further improve the catalytic activity. The Fe-based catalyst of the present invention is low in cost, and the production process is free of toxic substances. It is suitable for conditions with a low water-gas ratio, can improve the hydrogen yield of the water vapor shift, and reduce the methane selectivity. At the same time, the catalyst has good heat-resistant activity, and the specific surface and activity remain good after high-temperature treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the XRD pattern of the matrix prepared in Example 1;

[0021] Figure 2 is the XPS O1s curve of the catalysts prepared in Example 1 and Example 3;

[0022] Figure 3 This is the stability curve of the catalyst prepared in Example 1 after 100 hours of reaction. DETAILED DESCRIPTION

[0023] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0024] A first aspect of the present invention provides an Fe-based catalyst, comprising a matrix and a modifying element supported on the matrix, wherein the matrix comprises Fe, Al, M, and O elements, wherein M is selected from at least one of a non-Fe transition metal and an alkaline earth metal; XRD characterization shows that the matrix has a spinel crystal structure;

[0025] The modifying element is at least one selected from alkali metals;

[0026] Wherein, the content of oxygen defects in the catalyst is not less than 30%.

[0027] The inventors discovered that controlling the presence of high oxygen vacancies in Fe-based spinel catalysts can improve both the catalytic activity and thermal stability of the catalyst in the water-gas shift reaction. In this context, "oxygen vacancies" refer to vacancies in metal oxide crystals formed when oxygen atoms leave their lattice positions.

[0028] In the present invention, the oxygen defect content in the catalyst is characterized by XPS. XPS characterization is carried out on an ESCALAB 250 X-ray photoelectron spectrometer produced by Thermo Fisher-VG. The excitation source is AlKαX-ray with a monochromatic power of 150W. The reduction conditions are a heating rate of 5°C / min, pure H2 gas, a reaction pressure of 0.12MPa, and reduction for 3h after heating to the target temperature. The obtained XPS O1s curve is peak-separated, and the peak at 531±0.5eV is the characteristic peak of oxygen defect. The ratio of the peak area of ​​the characteristic peak of oxygen defect to the total area of ​​the O1s peak is calculated and recorded as the oxygen defect content.

[0029] In some preferred embodiments of the present invention, the oxygen deficiency content of the catalyst is 30-60%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or other typical but non-limiting values, or ranges therebetween. Preferably, the oxygen deficiency content of the catalyst is 40-50%. In these preferred embodiments, the catalytic activity and heat resistance of the catalyst in the water gas shift reaction are further enhanced.

[0030] According to the present invention, "characterized by XRD, the matrix has a spinel crystal structure" means that through X-ray diffraction testing, the XRD characteristic peaks of the matrix conform to the spinel structure characteristics and there are no obvious miscellaneous peaks, indicating that the matrix has a spinel crystal structure.

[0031] It is understood that, in the present invention, it is not excluded that the matrix also contains Fe, Al or M elements in the form of a single oxide, as long as the matrix has the above XRD characteristics.

[0032] In the present invention, X-ray diffraction analysis was performed on fresh catalyst samples using a Bruker D5005 diffractometer, using Cu Kα radiation (0.154184 nm), a scanning range of 3°-80°, and a scanning rate of 0.02° / s. Phases in the samples were analyzed and identified using EVA software based on the JCPDS method.

[0033] According to some preferred embodiments of the present invention, the molar ratio of Fe to Al in the matrix is ​​1:(0.01-0.2), preferably 1:(0.05-0.15). This preferred ratio of elements is beneficial for improving the structural stability of the catalyst under hydrothermal conditions.

[0034] Preferably, in the matrix, the Fe content calculated as ferric oxide is 40-98.5 wt%, preferably 60-90 wt%; the Al content calculated as aluminum oxide is 0.5-20 wt%, preferably 1-10 wt%; and the M content calculated as oxide is 1-40 wt%, preferably 1-35 wt%. The M oxide is calculated as a divalent oxide of the M metal.

[0035] In the present invention, the content of components in the matrix is ​​obtained by XRF testing.

[0036] In a preferred embodiment, the catalyst provided by the present invention has a fluffy, porous, non-uniform spinel surface, thereby having a high specific surface area. Preferably, the specific surface area of ​​the catalyst is 50-120 m 2 / g, preferably 60-100m 2 The above preferred specific surface area range is conducive to improving the water vapor conversion activity.

[0037] In this study, the specific surface area of ​​the catalyst was analyzed using low-temperature N2 isothermal adsorption-desorption and conventional BET calculations. Prior to analysis, the sample was dried at 120°C for 2 hours and then evacuated under vacuum at 300°C. The adsorption medium was high-purity nitrogen. Adsorption / desorption experiments were performed under liquid nitrogen cooling (-196°C).

[0038] In the present invention, the selection range for M is relatively wide, and non-Fe transition metals and alkaline earth metals can be applied to the present invention. For example, it can be at least one of Co, Ni, Cu, Cr, Mn, Zr, Ti, La, Mo, W, Ru, Rh, Pd, Zn, Ma, Ca, Sr and Ba, preferably at least one of Co, Ni, Cu, Cr, Mn, Mg, Ca, Sr and Ba. In order to improve catalyst stability, hydrothermal resistance and sintering resistance, while having environmental protection, it is more preferred that the M is selected from at least one of Co, Ni and Cu. Using the above-mentioned preferred M metal composition, it is conducive to forming an Fe-based spinel structure rich in oxygen defects with Fe and Al, while being conducive to further improving the water vapor shift activity and heat resistance of the catalyst.

[0039] In the present invention, the modifying element is at least one selected from alkali metals, preferably at least one selected from Li, Na, K, Rb, and Cs, more preferably K and / or Cs. In the above preferred case, the water vapor shift activity is improved.

[0040] The present invention provides a wide range of content for each component in the catalyst. Preferably, the matrix content is 90-99.9 wt% based on the total amount of the catalyst, and the content of the modifying element, calculated as oxide, is 0.1-10 wt%. Further preferably, the matrix content is 95-99.8 wt% based on the total amount of the catalyst, and the content of the modifying element, calculated as oxide, is 0.2-5 wt%.

[0041] In the present invention, the content of each component in the catalyst is obtained by X-ray fluorescence (XRF) testing.

[0042] A second aspect of the present invention provides a method for preparing an Fe-based catalyst, comprising the following steps:

[0043] (1) mixing a soluble compound of Fe, a soluble compound of Al, a soluble compound of M, and a solvent to obtain a mixed solution; wherein M is selected from at least one of a non-Fe transition metal and an alkaline earth metal;

[0044] (2) mixing the mixed solution with a complexing agent under stirring to obtain a gel;

[0045] (3) drying and calcining the gel to obtain a matrix;

[0046] Wherein, the calcination temperature does not exceed 400°C;

[0047] (4) A modifying element is loaded on the matrix, wherein the modifying element is at least one selected from alkali metals.

[0048] The preparation method provided by the present invention forms a uniformly dispersed precursor by complexation, forms a spinel catalyst with certain oxygen defects by controlling the calcination temperature and doping metals, and further loads alkali metals, which is beneficial to the dispersion of the alkali metals. The alkali metals and the Fe-based spinel oxides act synergistically, and the prepared catalyst has high stability, high hydrothermal and sintering resistance, and high activity in catalyzing water vapor shift.

[0049] According to the present invention, through X-ray diffraction testing, the XRD characteristic peaks of the matrix are consistent with the characteristics of the spinel structure, and there are no obvious miscellaneous peaks, indicating that the matrix has a spinel crystal structure.

[0050] The present invention has a wide range of selection for the amount of soluble Fe compounds, soluble Al compounds, and soluble M compounds, as long as the obtained Fe-based spinel oxide has the above-mentioned chemical composition. Those skilled in the art can make the selection according to actual conditions.

[0051] Preferably, calculated as metal elements, the molar ratio of the soluble Fe compound to the soluble Al compound is 1-25:1, preferably 5-15:1.

[0052] According to some preferred embodiments of the present invention, calculated as metal elements, the ratio of the total molar amount of the soluble Fe compounds and the soluble Al compounds to the molar amount of the soluble M compounds is 1-20:1, preferably 1-10:1.

[0053] The present invention does not particularly limit the type and amount of the solvent described in step (1), as long as the soluble compounds of Fe, Al, and M can be fully dissolved and mixed. Those skilled in the art can select the solvent according to actual conditions. For example, the solvent can be water.

[0054] According to some preferred embodiments of the present invention, in the mixed solution, the total molar concentration of Fe, Al and M, calculated as metal elements, is 0.01-5 mol / L, preferably 0.1-1 mol / L.

[0055] The present invention has no particular requirements for the specific selection of the soluble Fe compounds, soluble Al compounds and soluble M compounds. Conventional soluble inorganic salts or organic salts containing the above-mentioned metal elements can be used in the art as long as they can provide Fe, Al and M elements.

[0056] According to the present invention, the M element has the same definition as that of M in the catalyst described in the first aspect, and will not be repeated here.

[0057] According to some preferred embodiments of the present application, the soluble compound of Fe, the soluble compound of Al and the soluble compound of M are each independently selected from at least one of nitrates, sulfates, halides, acetates and formates of the metals, preferably nitrates of the metals.

[0058] The soluble compound of Fe, the soluble compound of Al and the soluble compound of M can also contain crystal water, which is well known to those skilled in the art.

[0059] According to some preferred embodiments of the present application, the complexing agent is selected from at least one of citric acid, oxalic acid, monoethanolamine, diethanolamine, triethanolamine and ethylenediaminetetraacetic acid, preferably citric acid. The use of the above preferred embodiments is advantageous for further promoting the dispersion of the catalyst.

[0060] According to some preferred embodiments of the present application, the ratio of the amount of the complexing agent to the total molar amount of the soluble compound of Fe, the soluble compound of Al and the soluble compound of M in terms of metal elements is 0.1-1:1, preferably 0.2-0.8:1. The use of the above preferred amount range is advantageous for forming a stable spinel structure.

[0061] In the present application, the complexing agent can be provided in the form of an aqueous solution of the complexing agent, preferably the concentration of the aqueous solution of the complexing agent is 0.01-2 mol / L, preferably 0.1-1 mol / L.

[0062] The present application does not have a particular limitation on the conditions for the mixing in step (2) as long as it is advantageous for forming a uniform gel, preferably the temperature for the mixing in step (2) is 40-90°C, preferably 50-80°C. The present application also does not have a particular requirement on the conditions for the stirring, which can be performed using the stirring conditions in the art.

[0063] In the present application, the solvent in the gel is removed by drying in step (3), preferably the conditions for the drying include a temperature of 90-150°C, preferably 90-120°C, and a time of 0.5-20 h, preferably 8-15 h.

[0064] In the present application, in order to form a good spinel structure and have an appropriate amount of oxygen defects, the calcination temperature in step (3) is not more than 400°C. In the prior art, the calcination temperature for preparing spinel oxides by sol-gel method is usually above 600°C.

[0065] In a further preferred case, the temperature for the calcination in step (3) is not more than 350°C, preferably 200-350°C. The use of the above preferred embodiments is advantageous for further forming a stable spinel structure.

[0066] Preferably, the calcination time is 0.5-12 hours, preferably 1-5 hours.

[0067] The present invention does not particularly limit the specific method of loading in step (4), and any conventional loading method and conditions in the art may be used. For example, an impregnation method using a soluble compound solution containing the modifying element may be used, or a physical mixing method such as mechanical grinding of an alkali metal salt, oxide, or hydroxide with the matrix may be used.

[0068] In the present invention, the selection range of the modifying element is the same as that defined in the first aspect and will not be repeated here.

[0069] According to some preferred embodiments of the present invention, in step (4), the loading comprises: impregnating the substrate with a solution of a soluble compound containing a modifying element, and then performing a second drying and a second calcination.

[0070] The present invention has no particular limitation on the specific method of the impregnation, which can be equal volume impregnation or excess impregnation. Preferably, the impregnation is equal volume impregnation.

[0071] Preferably, the amount of the solution containing the soluble compound of the modifying element and the matrix is ​​such that, based on the total amount of the prepared catalyst, the content of the matrix is ​​90-99.9wt%, preferably 95-99.8wt%; the content of the modifying element calculated as oxide is 0.1-10wt%, preferably 0.2-5wt%.

[0072] Preferably, the concentration of the modifying element in the solution of the soluble compound containing the modifying element is 0.1-0.5 mol / L.

[0073] The solvent in the solution may be water.

[0074] Preferably, the soluble compound of the modifying element is selected from alkali metal salts and / or hydroxides. Preferably, the alkali metal salt can be a metal inorganic salt and / or organic salt. The inorganic salt can be a nitrate, sulfate, or halide, and the organic salt can be a formates, acetates, etc. Preferably, the soluble compound of the modifying element is an alkali metal nitrate or an alkali metal hydroxide.

[0075] Preferably, the second drying temperature is 90-150° C. and the time is 0.5-12 h.

[0076] Preferably, the second calcination is performed at a temperature of 200-500° C. and for a time of 0.5-12 h.

[0077] The third aspect of the present invention provides the use of the above-mentioned Fe-based catalyst or the Fe-based catalyst prepared by the preparation method described in the second aspect in a water gas shift reaction.

[0078] A fourth aspect of the present invention provides a method for a water gas shift reaction, comprising: contacting a feed gas containing CO, water vapor, and a catalyst under water gas shift reaction conditions to perform a water gas shift reaction;

[0079] Wherein, the catalyst is the Fe-based catalyst described in the first aspect or the Fe-based catalyst prepared by the preparation method described in the second aspect.

[0080] Preferably, the water gas shift reaction conditions include: reaction temperature of 300-500°C, preferably 320-380°C; reaction pressure of 0.1-5 MPa, preferably 1-3 MPa; mass space velocity of feed gas of 2000-20000h -1 , preferably 5000-15000h -1 ; The water-to-carbon ratio is 2.4-6, preferably 3-4.

[0081] Preferably, the method further comprises: before the contacting, subjecting the catalyst to a reduction pretreatment in a reducing atmosphere containing H2 and / or CO.

[0082] Preferably, the reduction pretreatment conditions include: temperature of 200-600°C; time of 1-12 hours; pressure of 0.1-1 MPa, and space velocity of 500-20000 h -1 .

[0083] Preferably, the reducing atmosphere may further contain a non-reducing gas, wherein the non-reducing gas is water vapor and / or carbon dioxide. Preferably, in the reducing atmosphere, the ratio of the total volume of H2 and / or CO to the volume of the non-reducing gas is 1-2:1, preferably 1.2-1.6:1.

[0084] In a further preferred case, the reducing atmosphere can be provided directly by the raw gas.

[0085] The present invention will be described in detail below through examples.

[0086] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available.

[0087] The catalyst surface area was analyzed using low-temperature N2 isothermal adsorption-desorption and conventional BET calculations. Prior to analysis, the sample was dried at 120°C for 2 hours and then evacuated under vacuum at 300°C. The adsorption medium was high-purity nitrogen. Adsorption / desorption experiments were performed under liquid nitrogen cooling (-196°C).

[0088] The content of each component in the catalyst was determined by X-ray fluorescence analysis (XRF).

[0089] The oxygen defect content in the catalyst was determined by X-ray photoelectron spectroscopy (XPS).

[0090] Example 1

[0091] (1) Dissolve 4.83 g of Cu(NO3)2·3H2O, 16.16 g of Fe(NO3)3·9H2O, and 1.87 g of Al(NO3)3·9H2O in 80 mL of deionized water and stir to obtain a mixed solution.

[0092] (2) Dissolve 5.8 g of citric acid in 100 mL of deionized water and stir to dissolve. Mix the two solutions in a water bath at 80° C. and stir to obtain a gel.

[0093] (3) The obtained gel was dried in an oven at 100°C for 12 hours, then calcined at 200°C for 2 hours, and ground to obtain the matrix. The obtained matrix powder was subjected to X-ray diffraction analysis, as shown in FIG. Figure 1 As shown, it can be seen that the XRD curve of the matrix has a characteristic peak of the spinel structure and no other impurity peaks exist, indicating that the matrix has a spinel crystal structure. Through XRF testing and calculation, the molar ratio of Fe element to Al element in the matrix is ​​1:0.12. Based on the total amount of the matrix, the content of Fe2O3 is 63.4wt%, the content of Al2O3 is 5wt%, and the content of CuO is 31.5wt%.

[0094] (4) Pour 3 mL of 0.56 mol / L KOH aqueous solution into the above powder and grind it evenly. The obtained wet powder is dried in an oven at 100°C for 12 hours and then calcined at 340°C for 3 hours. The prepared sample is ground into powder and sieved with a 40-60 mesh sieve. The obtained catalyst is recorded as A1. The composition of the catalyst is shown in Table 1. The O1s curve of the catalyst is tested by the XPS method as shown in Figure 2 The calculated oxygen defect content is shown in Table 1.

[0095] Example 2

[0096] (1) Dissolve 1.52 g of Ni(NO3)2·6H2O, 20.2 g of Fe(NO3)3·9H2O, and 1.87 g of Al(NO3)3·9H2O in 100 mL of deionized water and stir to obtain a mixed solution.

[0097] (2) Dissolve 7.0 g of citric acid in 100 mL of deionized water and stir to dissolve. Mix the two solutions in a water bath at 80° C. and stir to obtain a gel.

[0098] (3) The obtained gel was dried in an oven at 100°C for 12 hours, then calcined at 200°C for 2 hours, and ground to obtain a matrix. The obtained matrix powder was subjected to X-ray diffraction analysis. Figure 1 Similarly, XRD testing shows that the matrix has a spinel crystal structure. XRF testing and calculation show that the molar ratio of Fe element to Al element in the matrix is ​​1:0.1. Based on the total amount of the matrix, the content of Fe2O3 is 86.1wt%, the content of Al2O3 is 5.5wt%, and the content of NiO is 8.4wt%.

[0099] (4) 2.5 mL of a 0.135 mol / L aqueous solution of Cs2CO3 was poured into the above powder and ground evenly. The resulting wet powder was dried in an oven at 100°C for 12 hours and then calcined at 340°C for 3 hours. The prepared sample was ground into a powder and sieved with a 40-60 mesh sieve. The resulting catalyst was designated A2. The composition of the catalyst is shown in Table 1. The oxygen defect content measured and calculated by the XPS method is shown in Table 1.

[0100] Example 3

[0101] (1) 8.73 g of Co(NO3)2·6H2O, 24.2 g of Fe(NO3)3·9H2O, and 2.81 g of Al(NO3)3·9H2O were dissolved in 120 mL of deionized water and stirred to obtain a mixed solution.

[0102] (2) Then, 8.65 g of citric acid was dissolved in 100 mL of deionized water and stirred to dissolve. The two solutions were mixed and stirred in a water bath at 80° C. to obtain a gel.

[0103] (3) The obtained gel was dried in an oven at 100°C for 12 hours, then calcined at 200°C for 2 hours, and ground to obtain a matrix. The obtained matrix powder was subjected to X-ray diffraction analysis. Figure 1 Similarly, XRD testing showed that the powder had a spinel crystal structure. XRF testing and calculation showed that the molar ratio of Fe element to Al element in the matrix was 1:0.12. Based on the total amount of the matrix, the content of Fe2O3 was 64.6wt%, the content of Al2O3 was 5.1wt%, and the content of CoO was 30.3wt%.

[0104] (4) Pour 3.8 mL of 0.85 mol / L KNO3 aqueous solution into the above powder and grind it evenly. The obtained wet powder is dried in an oven at 110°C for 12 hours and then calcined at 340°C for 3 hours. The prepared sample is ground into powder and sieved with a 40-60 mesh sieve. The obtained catalyst is recorded as A3. The composition of the catalyst is shown in Table 1. The O1s curve of the catalyst is tested by XPS method as shown in Figure 2 The calculated oxygen defect content is shown in Table 1.

[0105] Example 4

[0106] The method of Example 1 was followed, except that the mass of Cu(NO3)2·3H2O was 4.83 g, the mass of Fe(NO3)3·9H2O was 16.16 g, and the mass of Al(NO3)3·9H2O was 1.01 g. The calcination temperature used in step (3) was 400°C. XRD testing showed that the powder had a spinel crystal structure. XRF testing and calculation showed that the molar ratio of Fe to Al in the matrix was 1:0.067. Based on the total amount of the matrix, the content of Fe2O3 was 64.9 wt%, the content of Al2O3 was 2.8 wt%, and the content of CuO was 32.3 wt%.

[0107] K was loaded in the same manner as in Example 1 to obtain a catalyst designated as A4. The composition of the catalyst is shown in Table 1.

[0108] Example 5

[0109] The method of Example 1 was followed, except that the concentration of the KOH aqueous solution was 1.8 mol / L.

[0110] The prepared catalyst is recorded as A5, and the composition of the catalyst is shown in Table 1.

[0111] Comparative Example 1

[0112] Dissolve 4.83g of Cu(NO3)2·3H2O, 16.16g of Fe(NO3)3·9H2O and 1.01g of Al(NO3)3·9H2O in 160mL of deionized water and stir to obtain a mixed solution. Then pour 2mol / L of Na2CO3 solution into the above solution, stir during neutralization, titrate to pH 8, heat-boil and age at 80℃ for 1h, filter and wash, dry the obtained precipitate in an oven at 100℃ for 12h, and then roast at 200℃ for 2h, grind to obtain powder. The obtained powder was subjected to X-ray diffraction analysis, and the results were consistent with those of the previous examples. Figure 1Similarly, XRD testing showed that the powder had a spinel crystal structure. XRF testing and calculation showed that the molar ratio of Fe element to Al element in the matrix was 1:0.067. Based on the total amount of the matrix, the content of Fe2O3 was 64.9wt%, the content of Al2O3 was 2.8wt%, and the content of CuO was 32.2wt%.

[0113] 3 mL of 0.56 mol / L aqueous KOH solution was added to the above powder and ground uniformly. The resulting wet powder was dried in an oven at 100°C for 12 hours and then calcined at 400°C for 3 hours. The prepared sample was ground into a powder and sieved with a 40-60 mesh sieve. The resulting catalyst is designated DA1. The catalyst composition is shown in Table 1.

[0114] Comparative Example 2

[0115] The method of Example 1 was followed, except that step (4) was not performed. The substrate prepared in step (3) of Example 1 was used as a catalyst, denoted as DA2. The composition of the catalyst is shown in Table 1.

[0116] Comparative Example 3

[0117] The method of Example 1 is followed, except that the calcination temperature in step (3) is 600°C.

[0118] The prepared catalyst is recorded as DA3, and the composition of the catalyst is shown in Table 1.

[0119] Table 1

[0120]

[0121] Test Case

[0122] (1) Catalyst activity evaluation:

[0123] 0.5 g of the catalysts of the above examples and comparative examples were respectively loaded into a reaction tube with an inner diameter of 8 mm and pretreated at 400 ° C for 2 h. The pretreatment was carried out under normal pressure and dry gas atmosphere. The composition (volume content) of the dry gas atmosphere was as follows: CO / CO2 / H2 / N2 = 24.7% / 8.3% / 49.5% / 17.5%, and the dry gas space velocity was 20000 h -1 , water-carbon ratio 1.2.

[0124] Then adjust the dry gas air velocity to 12000h -1 , water-carbon ratio 3.0, reacted at normal pressure and 300℃ for 2h, and the product composition was analyzed by gas chromatography. The evaluation results are shown in Table 2. The stability curve of the catalyst prepared in Example 1 after 100h reaction is shown in Figure 3 shown.

[0125] in,

[0126]

[0127]

[0128] In the above formula, F CO(进) refers to the CO flow rate at the reactor inlet, F CO(出) refers to the CO flow rate at the reactor outlet (mL / min), F CH4(进) refers to the CH4flow rate at the reactor inlet (mL / min), F CH4(出) refers to the CH4flow rate at the reactor outlet (mL / min), F H2(进) refers to the H2flow rate at the reactor inlet (mL / min), F H2(出) refers to the H2flow rate at the reactor outlet (mL / min), V m is the molar volume of gas (L / mol), M cat is the mass of the catalyst loaded (g).

[0129] (2) Heat-resistant activity test

[0130] The atmosphere, space velocity and conditions of the above steam reforming reaction are the same, except that the temperature is maintained at 530℃ for 8h, then the temperature is lowered to 300℃ for 4h, and the CO conversion rate is tested as the heat-resistant activity.

[0131] The heat-resistant activity retention rate is then calculated by the following formula, and the results are shown in Table 2.

[0132] where the initial activity is the CO conversion rate measured under the conditions of Test Example (1).

[0133] Table 2

[0134]

[0135] It can be seen from the results of Table 1 and Table 2 that, by comparing the examples and Comparative Examples 1 and 3, it can be seen that the catalyst prepared in the present application has a higher oxygen defect, and by controlling the higher oxygen defect in the Fe-based spinel catalyst, the catalytic activity and heat-resistant activity of the catalyst in the steam reforming reaction are improved. By comparing Example 1 and Comparative Example 2, it can be seen that by surface modification of the substrate with alkali metal, the stability and catalytic activity of the catalyst in steam reforming can be improved.

[0136] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. An Fe-based catalyst, characterized in that The catalyst includes a matrix and a modifying element supported on the matrix, wherein the matrix includes Fe, Al, M and O elements, and M is selected from at least one of a non-Fe transition metal and an alkaline earth metal; XRD characterization shows that the matrix has a spinel crystal structure; The modifying element is at least one selected from alkali metals; wherein the content of oxygen defects in the catalyst is not less than 30%; The preparation method of the Fe-based catalyst comprises the following steps: (1) mixing a soluble compound of Fe, a soluble compound of Al, a soluble compound of M, and a solvent to obtain a mixed solution; wherein M is selected from at least one of a non-Fe transition metal and an alkaline earth metal; (2) mixing the mixed solution with a complexing agent under stirring to obtain a gel; (3) drying and calcining the gel to obtain a matrix; Wherein, the calcination temperature does not exceed 350°C; (4) A modifying element is loaded on the matrix, wherein the modifying element is selected from at least one of alkali metals.

2. The catalyst according to claim 1, wherein The oxygen deficiency content in the catalyst is 30-60%.

3. The catalyst according to claim 2, wherein The oxygen deficiency content in the catalyst is 40-50%.

4. The catalyst according to claim 1, wherein The specific surface area of ​​the catalyst is 50-120 m 2 / g.

5. The catalyst according to claim 4, wherein The specific surface area of ​​the catalyst is 60-100 m 2 / g. The catalyst according to claim 1 , wherein M is at least one selected from the group consisting of Co, Ni, Cu, Cr, Mn, Zn, Mg, Ca, Sr, and Ba.

7. The catalyst according to claim 6, wherein M is at least one selected from Co, Ni and Cu.

8. The catalyst according to claim 1, wherein The modifying element is selected from at least one of Li, Na, K, Rb and Cs.

9. The catalyst according to claim 8, wherein The modifying element is K and / or Cs.

10. The catalyst according to claim 1, wherein Based on the total amount of the catalyst, the content of the matrix is ​​90-99.9 wt %; the content of the modifying element calculated as oxide is 0.1-10 wt %. The catalyst according to claim 10 , wherein Based on the total amount of the catalyst, the content of the matrix is ​​95-99.8 wt %; the content of the modifying element calculated as oxide is 0.2-5 wt %.

12. The catalyst according to claim 1, wherein In the matrix, the molar ratio of Fe element to Al element is 1:(0.01-0.2).

13. The catalyst according to claim 12, wherein In the matrix, the molar ratio of Fe element to Al element is 1:(0.05-0.15).

14. The catalyst according to claim 1, wherein In the matrix, the content of Fe calculated as ferric oxide is 40-98.5 wt %, the content of Al calculated as aluminum oxide is 0.5-20 wt %, and the content of M calculated as oxide is 1-40 wt %.

15. The catalyst according to claim 1, wherein Calculated on the basis of metal elements, the molar ratio of the soluble Fe compound to the soluble Al compound is 1-25:

1.

16. The catalyst according to claim 15, wherein Calculated on the basis of metal elements, the molar ratio of the soluble Fe compound to the soluble Al compound is 5-15:

1.

17. The catalyst according to claim 1, wherein Calculated as metal elements, the ratio of the total molar amount of the soluble Fe compound and the soluble Al compound to the molar amount of the soluble M compound is 1-20:

1.

18. The catalyst according to claim 17, wherein Calculated on the basis of metal elements, the ratio of the total molar amount of the soluble Fe compound and the soluble Al compound to the molar amount of the soluble M compound is 1-10:

1.

19. The catalyst according to claim 1, wherein In the mixed solution, the total molar concentration of Fe, Al and M, calculated as metal elements, is 0.01-5 mol / L.

20. The catalyst according to claim 19, wherein In the mixed solution, the total molar concentration of Fe, Al and M, calculated as metal elements, is 0.1-1 mol / L.

21. The catalyst according to claim 1, wherein The soluble Fe compound, the soluble Al compound and the soluble M compound are each independently selected from inorganic salts and / or organic salts of metals.

22. The catalyst according to claim 21, wherein The soluble Fe compound, the soluble Al compound and the soluble M compound are each independently selected from at least one of nitrates, sulfates, halides, acetates and formates.

23. The catalyst according to claim 1, wherein The complexing agent is selected from at least one of citric acid, oxalic acid, monoethanolamine, diethanolamine, triethanolamine and ethylenediaminetetraacetic acid.

24. The catalyst according to claim 1, wherein The ratio of the amount of the complexing agent to the total molar amount of the soluble Fe compound, the soluble Al compound and the soluble M compound calculated as metal elements is 0.1-1:

1.

25. The catalyst according to claim 1, wherein The mixing temperature in step (2) is 40-90°C.

26. The catalyst according to claim 1, wherein In step (3), the drying conditions include: temperature of 90-150°C and time of 0.5-20h.

27. The catalyst according to claim 1, wherein The calcination temperature is 200-350°C.

28. The catalyst according to claim 1, wherein The calcination time is 0.5-12h.

29. The catalyst according to claim 1, wherein In step (4), the loading comprises: impregnating the substrate with a solution of a soluble compound containing a modifying element, and then performing a second drying and a second calcination.

30. The catalyst according to claim 29, wherein The impregnation is equal volume impregnation or excess impregnation.

31. The catalyst according to claim 29, wherein Calculated as the modifying element, the concentration of the solution containing the soluble compound of the modifying element is 0.01-2 mol / L.

32. The catalyst according to claim 29, wherein The amount of the solution of the soluble compound containing the modifying element and the matrix is ​​such that, based on the total amount of the prepared catalyst, the content of the matrix is ​​90-99.9 wt %; and the content of the modifying element calculated as oxide is 0.1-10 wt %.

33. The catalyst according to claim 32, wherein The amount of the solution of the soluble compound containing the modifying element and the matrix is ​​such that, based on the total amount of the prepared catalyst, the content of the matrix is ​​95-99.8 wt %; and the content of the modifying element calculated as oxide is 0.2-5 wt %.

34. Use of the Fe-based catalyst according to any one of claims 1 to 33 in a water gas shift reaction.

35. A method for a water gas shift reaction, characterized in that: include: Under water gas shift reaction conditions, raw gas containing CO and water vapor are brought into contact with a catalyst to perform water gas shift reaction; Wherein, the catalyst is the Fe-based catalyst described in any one of claims 1-33.

36. The method according to claim 35, wherein The water gas shift reaction conditions include: reaction temperature of 300-500°C; reaction pressure of 0.1-5 MPa; mass space velocity of feed gas of 2000-20000 h -1 ; The water-carbon ratio is 2.4-6.

37. The method according to claim 36, wherein The water gas shift reaction conditions include: reaction temperature of 320-380°C; reaction pressure of 1-3 MPa; mass space velocity of feed gas of 5000-15000 h -1 ; The water-to-carbon ratio is 3-4.

38. The method of claim 35, wherein: The method further comprises: before the contacting, subjecting the catalyst to a reduction pretreatment in a reducing atmosphere containing H2 and / or CO.

39. The method according to claim 38, wherein The reduction pretreatment conditions include: temperature of 200-600°C; time of 1-12 hours; pressure of 0.1-1 MPa; space velocity of 500-20000 h -1 .

40. The method of claim 38, wherein The reducing atmosphere further comprises a non-reducing gas, which is water vapor and / or carbon dioxide.

41. The method according to claim 40, wherein In the reducing atmosphere, the ratio of the total volume of H2 and / or CO to the volume of the non-reducing gas is 1-2:

1.

42. The method according to claim 41, wherein In the reducing atmosphere, the ratio of the total volume of H2 and / or CO to the volume of the non-reducing gas is 1.2-1.6:1.

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