Magnesium-aluminum composite oxide carrier, method for preparing the same, and methane dry reforming catalyst and use thereof

Abstract

The present application relates to a magnesium-aluminum composite oxide carrier, a preparation method thereof, and a methane dry reforming catalyst and application thereof, the magnesium-aluminum composite oxide carrier is composed of MgAl2O4 spinel and potassium oxide, the mass fraction of the potassium oxide is 0.1-4% based on the magnesium-aluminum composite oxide carrier, the specific surface area of the magnesium-aluminum composite oxide carrier is 15-60 m 2 / g, the methane dry reforming catalyst prepared by using the magnesium-aluminum composite oxide carrier has the characteristics of high activity, good carbon deposition resistance and high stability, and the application method and device of the methane dry reforming catalyst provided by the present application have good stability and long running period.

Description

Technical Field

[0001] This invention relates to the field of methane dry reforming reaction, specifically to a magnesium-aluminum composite oxide support and its preparation method, a methane dry reforming catalyst using the magnesium-aluminum composite oxide support, and a method for applying the methane dry reforming catalyst. Background Technology

[0002] Both methane and CO2 are greenhouse gases. The dry reforming of methane provides a highly attractive process route for the large-scale industrial utilization of CO2, which has profound historical significance for mitigating the damage of the greenhouse effect to the global ecological environment and thus has broad application prospects.

[0003] Currently, inexpensive and highly catalytically active Ni is the preferred catalyst for methane dry reforming. However, Ni is prone to sintering and carbon deposition under high temperature and pressure conditions, which is the main obstacle to the industrialization of this process. Therefore, developing highly active and stable methane dry reforming catalysts is currently the key research area in this field.

[0004] CN 105561998 A relates to a methane dry reforming catalyst and its preparation method. The method includes impregnating a support with an impregnation solution, followed by drying and calcination. The impregnation solution contains a soluble compound of the metal active component and a surfactant. The methane dry reforming catalyst prepared by this method exhibits improved catalytic activity and enhanced resistance to coking.

[0005] CN102416328A discloses a catalyst for the reforming of methane into syngas and its preparation method, belonging to the technical field of catalysts for the reforming of methane into syngas. The catalyst of this invention is composed of nickel, iron, cerium oxide, and aluminum spinel. The method of this invention involves first preparing a mesoporous MgAl₂O₄ spinel support, then preparing a nickel-based catalyst suspension, and finally obtaining the finished product through a simple process of filtration, washing, drying, and calcination. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low activity and poor stability of existing methane dry reforming catalysts, and to provide a magnesium-aluminum composite oxide support and its preparation method, as well as a method for preparing a methane dry reforming catalyst with high activity, stability and good anti-coking properties, and the obtained methane dry reforming catalyst and its application method.

[0007] The first aspect of this invention provides a magnesium-aluminum composite oxide carrier, wherein the magnesium-aluminum composite oxide carrier is composed of MgAl2O4 spinel and potassium oxide, wherein the mass fraction of potassium oxide is 0.1-4% based on the magnesium-aluminum composite oxide carrier, and the specific surface area of ​​the magnesium-aluminum composite oxide carrier is 15-60 m². 2 / g.

[0008] Preferably, using a magnesium-aluminum composite oxide carrier as a reference, the mass fraction of potassium oxide is 0.5-3%, and the specific surface area of ​​the magnesium-aluminum composite oxide carrier is 20-55 m². 2 / g.

[0009] In this invention, the specific surface area is characterized by isothermal nitrogen adsorption.

[0010] A second aspect of the present invention provides a method for preparing the above-mentioned magnesium-aluminum composite oxide support, comprising:

[0011] (1) Weigh out the specified amounts of soluble aluminum salt and soluble magnesium salt to prepare a mixed salt solution;

[0012] (2) Weigh KOH and / or K2CO3 to prepare a precipitant;

[0013] (3) The mixed salt solution and the precipitant are separately added dropwise into the precipitation tank for co-precipitation using the co-flow co-precipitation method;

[0014] (4) After sedimentation, allow the mixture to stand and age.

[0015] (5) Filter cake I is obtained by filtration and washing. It is washed with deionized water. The amount of washing solvent and the number of washing times are controlled to control the amount of potassium oxide contained in the magnesium-aluminum composite oxide carrier after calcination.

[0016] (6) Filter cake I is ultrasonically dispersed in an organic solvent and then filtered to obtain filter cake II;

[0017] (7) After drying, filter cake II is calcined at 1250-1450℃ for 2-10 hours to obtain magnesium-aluminum composite oxide carrier.

[0018] In one embodiment of the present invention, in step (1), the soluble aluminum salt is one or more selected from aluminum nitrate, aluminum sulfate, aluminum chloride or their hydrates; preferably aluminum nitrate;

[0019] The soluble magnesium salt is selected from one or more of magnesium nitrate, magnesium sulfate, magnesium chloride, or their hydrates; magnesium nitrate is preferred.

[0020] The molar ratio of magnesium ions to aluminum ions in the solution is based on the stoichiometric ratio required to completely generate MgAl2O4 spinel; the total metal ion concentration in the mixed salt solution is 0.1–0.5 mol / L, preferably 0.2–0.4 mol / L.

[0021] In one embodiment of the present invention, in step (2), the KOH and K2CO3 in the precipitant are in a molar ratio of (OH) - ):(CO3 2-The precipitant solution is prepared with a ratio of 0.5 to 5:1, preferably 1 to 4:1. The concentration of the precipitant solution, in terms of the molar concentration of alkali metal ions, is 0.2 to 5 mol / L, preferably 0.5 to 2 mol / L.

[0022] In one embodiment of the present invention, in step (3), the mixed salt solution and the precipitant are dripped into the precipitation tank at a certain flow rate using a co-precipitation method, with the pH value of the solution in the precipitation tank being controlled to be stable at 7-13, preferably 8-12; the temperature of the precipitation tank is controlled at 25-80°C, preferably 40-80°C.

[0023] In one embodiment of the present invention, in step (4), the settling and aging time after precipitation is 1 to 10 hours, preferably 1.5 to 5 hours.

[0024] In one embodiment of the present invention, in step (5), the ratio of the volume of deionized water to the volume of filter cake in each wash is 3 to 10:1, and the number of washes is 2 to 6.

[0025] In one embodiment of the present invention, in step (6), filter cake I is placed in an organic solvent and ultrasonically dispersed to make it uniformly dispersed in the organic solvent and kept for 0.5 to 3 hours, preferably 0.5 to 2 hours; the organic solvent is one or more selected from methanol, ethanol, diethyl ether, acetone, and the volume ratio of the organic solvent to filter cake I is 3 to 10:1, preferably 3 to 6:1.

[0026] In one embodiment of the present invention, in step (7), the filter cake II is dried by one or more of the following methods: drying in ordinary static air, drying in flowing air, freeze drying, or vacuum drying, preferably freeze drying or vacuum drying, and the drying time is 1 to 20 hours, preferably 2 to 10 hours.

[0027] In one embodiment of the present invention, the dried sample is calcined at a temperature of 1250–1450°C for 2–5 hours to obtain a magnesium-aluminum composite oxide carrier.

[0028] The preparation method provided by the present invention is to mix soluble aluminum salt and soluble magnesium salt together and prepare them by co-precipitation. In the preparation process, by selecting a suitable precipitant and controlling the washing process, a suitable K2O content is retained. At the same time, the filter cake is ultrasonically dispersed with an organic solvent and combined with a preferred drying method. Finally, it is calcined at high temperature to prepare a high-performance K-containing magnesium-aluminum composite oxide carrier.

[0029] To improve the structural stability of the carrier, the carrier of the present invention is calcined at a high temperature of 1250-1450℃. However, due to the preferred preparation method of the present invention, the magnesium-aluminum composite oxide carrier still has a large specific surface area under such high temperature calcination, which is beneficial to the uniform dispersion of active metals.

[0030] A third aspect of the present invention provides a method for preparing a methane dry reforming catalyst using any of the above-mentioned magnesium-aluminum composite oxide supports, comprising: impregnating the magnesium-aluminum composite oxide support with an impregnation solution, and then drying and calcining it, wherein the impregnation solution contains a soluble compound of active metal Ni and a surfactant P123.

[0031] In this invention, the soluble compound of the active metal Ni is any soluble compound of Ni, such as Ni(NO3)2·6H2O or nickel acetate, preferably Ni(NO3)2·6H2O.

[0032] In one embodiment of the present invention, the molar ratio of surfactant P123 to active metal Ni atoms in the impregnation solution is 0.01 to 2, preferably 0.01 to 1; the concentration of soluble compounds of active metal Ni in the impregnation solution, based on metal elements, is 14.6 to 191.6 g / L; and the amount of support used is such that the content of active metal Ni component in the obtained catalyst, based on the total amount of catalyst, is 2 to 20% by weight, preferably 3 to 15% by weight, more preferably 4 to 12% by weight, and preferably for 2 to 5 hours.

[0033] In this invention, the impregnation method and conditions can be carried out with reference to existing technology, for example, it can be equal volume impregnation or supersaturated impregnation. Impregnation can be carried out at 10-80°C.

[0034] In one embodiment of the present invention, the drying temperature is 80-140°C, preferably 100-120°C, and the drying time is 1-10 hours, preferably 5-10 hours; the calcination temperature is 400-1000°C, preferably 450-700°C, and the calcination time is 1-10 hours, preferably 2-5 hours.

[0035] In one embodiment of the present invention, in the methane dry reforming catalyst, the dispersion of metallic Ni is 8-30%, preferably 10-25%, and the grain size of metallic Ni is 2-10 nm, preferably 3-8 nm.

[0036] In this invention, the dispersion of metallic Ni is measured by H2 chemisorption; the grain size of metallic Ni can be determined by XRD characterization or calculated by H2 chemisorption.

[0037] In this invention, the dispersion of the metal active component was measured using a Micromeritics (ASAP-2010C) chemisorption analyzer via the H2 chemisorption method described in CN105561998A. Specifically, a 0.2g sample was first degassed at 300℃ for 1 hour, then heated to 700℃ for reduction for 2 hours, and finally cooled to 40℃ for H2 chemisorption. The dispersion of the metal active component and the average particle size of the metal active component were then calculated using formulas based on the amount of H2 chemisorbed.

[0038] A fourth aspect of the present invention provides a methane dry reforming catalyst prepared by any of the above-described preparation methods.

[0039] Compared with existing technologies, the catalyst support preparation method provided by this invention can increase the specific surface area of ​​the support, thereby facilitating the dispersion and loading of active metals. The resulting catalyst exhibits smaller metal particle sizes, which in turn improves catalyst activity and anti-coking performance. Simultaneously, by controlling the number of washing cycles during support preparation, an appropriate amount of K element, which promotes anti-coking properties, is directly retained in the composite oxide support. This reduces the number of filter cake washing cycles, lowers production complexity, and enhances the catalyst's anti-coking performance. When the active metal supported on the support prepared by this invention is used to catalyze the dry reforming reaction of methane, it exhibits higher catalytic activity, better stability, and significantly enhanced anti-coking performance compared to similar catalysts used previously.

[0040] The fifth aspect of the present invention provides a method for using any of the above-described methane dry reforming catalysts in the preparation of syngas through methane dry reforming.

[0041] The catalyst prepared according to the method provided by the present invention requires reduction and activation of the active metal in the presence of hydrogen before it can be used in the dry reforming reaction of methane. The reduction conditions are as follows: reduction temperature is 300-800°C, preferably 400-750°C, more preferably 550-700°C; reduction time is 0.5-10 hours, preferably 1-5 hours, more preferably 2-4 hours. The reduction can be carried out in pure hydrogen or in a mixture of hydrogen and an inert gas, such as in a mixture of hydrogen and nitrogen and / or argon. The hydrogen pressure is 0-2 MPa, preferably 0-1 MPa, more preferably 0-0.5 MPa.

[0042] In one embodiment of the present invention, methane and CO2 are reacted in a fixed-bed reactor in the presence of a methane dry reforming catalyst to produce syngas. The molar ratio of methane to carbon dioxide is 0.7–1.1:1, preferably 0.8–1.0:1; the reaction temperature is 550–950°C, preferably 600–850°C, more preferably 700–800°C; the pressure is 0–3 MPa, preferably 0–1 MPa; and the feed gas space velocity is 2000–120000 ml·g. -1 ·h -1 Preferably, it is 60,000–120,000 ml·g -1 ·h -1 .

[0043] Compared with existing catalysts, the methane dry reforming catalyst provided by this invention has strong anti-coking properties, and the application method of the provided methane dry reforming catalyst has good equipment stability and long operating cycle. Attached Figure Description

[0044] Figure 1 This is the result of long-term continuous and stable operation of the methane dry reforming catalyst obtained in Example 1. Detailed Implementation

[0045] The following embodiments will further illustrate the present invention, but should not be construed as limiting the present invention.

[0046] Example 1

[0047] (1) Preparation of magnesium-aluminum composite oxide carrier

[0048] Weigh 18.46g of Mg(NO3)2·6H2O and 54.02g of Al(NO3)3·9H2O and dissolve them in 540mL of deionized water to prepare a mixed salt solution. Weigh 9.35g of KOH and 11.52g of K2CO3 and dissolve them in 250mL of deionized water to prepare a precipitant. The mixed salt solution and precipitant are co-precipitated in a precipitation tank at a controlled flow rate, maintaining the pH of the solution in the tank at 10 and the temperature at 65℃. After precipitation, allow the solution to stand for 2.5 hours to age.

[0049] The filter cake was filtered and washed three times with a deionized water to filter cake volume ratio of 10:1. The resulting filter cake I was then washed once more with anhydrous ethanol under ultrasonic assistance, with an anhydrous ethanol to filter cake I volume ratio of 4:1, followed by filtration. The resulting filter cake II was placed in a vacuum drying oven and dried at 50°C for 8 hours. It was then removed and calcined in a muffle furnace at 1350°C for 3 hours to obtain the magnesium-aluminum composite oxide support, denoted as Mg-Al-1. Characterized by isothermal nitrogen adsorption, its specific surface area was 45 m². 2 / g; based on the magnesium-aluminum composite oxide carrier, the K2O content in the carrier is 2.7% by mass.

[0050] (2) Preparation of methane dry reforming catalyst

[0051] 1.765 g of Ni(NO3)2·6H2O and 0.06 g of P123 were weighed and dissolved in 5.6 mL of deionized water. This impregnation solution was then used to impregnate 4 g of the carrier obtained in step (1). After standing for 2 hours, the carrier was vacuum dried in a rotary evaporator and then dried in an oven at 110 °C for 7 hours. The dried sample was then calcined in a muffle furnace at 500 °C for 3 hours. The resulting methane dry reforming catalyst was designated as Ni / Mg-Al-1. The dispersion of the Ni metal active component in the catalyst was 14.6%, and the average particle size of the Ni metal active component was 6.8 nm, as determined by hydrogen chemisorption.

[0052] (3) Application of methane dry reforming catalysts

[0053] Weigh 0.1g of Ni / Mg-Al-1 catalyst, dilute it to 2ml with 40-60 mesh quartz sand, and pack it into an inner diameter container. Activation was performed in a quartz tube reactor under normal pressure and a pure hydrogen atmosphere at 700°C for 3 hours. After reduction, the temperature was raised to 750°C under a hydrogen atmosphere, and the feed gas (CH4 / CO2 molar ratio = 1 / 1) was switched for further reaction. The reaction space velocity was 120,000 ml·g⁻¹. -1 ·h -1 The reaction pressure was atmospheric pressure. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4 =88.8%, X CO2 =88.5%, H2 / CO = 1.01, where X CH4 X represents the conversion rate of methane. CO2 H2 / CO represents the conversion rate of CO2, and H2 / CO represents the molar ratio of H2 and CO in the product gas.

[0054] The long-cycle reaction performance of the catalyst obtained in Example 1 is shown in... Figure 1 Specifically, this refers to the performance of the methane dry reforming reaction catalyzed by the catalyst with a reaction time of 0-930 hours. Figure 1 It can be seen that the catalyst exhibits very stable reaction performance. After 930 hours of reaction, coke deposition analysis was performed on the unloaded catalyst, and the coke deposition rate per unit time was calculated to be 0.025 mgC / g using the following formula. cat ·h.

[0055]

[0056] Where m after The mass m represents the mass of the catalyst after the reaction.before The value represents the mass of the catalyst before the reaction, C represents the coke content on the catalyst as measured by the CS instrument, and h represents the reaction time.

[0057] Example 2

[0058] (1) Preparation of magnesium-aluminum composite oxide carrier

[0059] Weigh 18.46g of Mg(NO3)2·6H2O and 54.02g of Al(NO3)3·9H2O and dissolve them in 540mL of deionized water to prepare a mixed salt solution. Weigh 7.01g of KOH and 17.28g of K2CO3 and dissolve them in 250mL of deionized water to prepare a precipitant. The mixed salt solution and precipitant are then co-precipitated in a precipitation tank at a controlled flow rate. The pH of the solution in the precipitation tank is controlled at 11, and the temperature of the precipitation tank is controlled at 75℃. After precipitation, allow the solution to stand for 1.5 hours to age.

[0060] The filter cake was filtered and washed twice with deionized water at a volume ratio of 15:1. The resulting filter cake I was then washed once more with anhydrous ethanol under ultrasonic assistance at a volume ratio of 3:1, followed by filtration. The resulting filter cake II was placed in a vacuum drying oven and dried at 50°C for 10 hours. It was then removed and calcined in a muffle furnace at 1250°C for 4 hours to obtain a magnesium-aluminum composite oxide support, denoted as Mg-Al-2. Characterized by isothermal nitrogen adsorption, its specific surface area was 31 m². 2 / g; based on the magnesium-aluminum composite oxide carrier, the K2O content in the carrier is 2.1% by mass.

[0061] (2) Preparation of methane dry reforming catalyst

[0062] 1.35 g of Ni(NO3)2·6H2O and 0.11 g of P123 were weighed and dissolved in 5.6 mL of deionized water. This impregnation solution was then used to impregnate 4 g of the carrier obtained in step (1). After standing for 2 hours, the carrier was vacuum dried in a rotary evaporator and then dried in an oven at 120 °C for 5 hours. The dried sample was then calcined in a muffle furnace at 450 °C for 3 hours. The resulting methane dry reforming catalyst was designated as Ni / Mg-Al-2. The dispersion of the Ni metal active component in the catalyst was 15.7%, and the average particle size of the Ni metal active component was 4.5 nm, as determined by hydrogen chemisorption.

[0063] (3) Application of methane dry reforming catalysts

[0064] The catalyst was activated and a dry reforming reaction of methane was carried out under the same conditions as in Example 1. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4 =82.3%, X CO2=81.7%, H2 / CO = 1.02. After 50 hours of reaction, coking analysis was performed on the unloaded catalyst, and the calculated coking rate was 0.042 mgC / g. cat ·h.

[0065] Example 3

[0066] (1) Preparation of magnesium-aluminum composite oxide carrier

[0067] Weigh 18.46g of Mg(NO3)2·6H2O and 54.02g of Al(NO3)3·9H2O and dissolve them in 540mL of deionized water to prepare a mixed salt solution. Weigh 9.12g of KOH and 7.49g of K2CO3 and dissolve them in 250mL of deionized water to prepare a precipitant. The mixed salt solution and precipitant are then co-precipitated in a precipitation tank at a controlled flow rate. The pH of the solution in the precipitation tank is controlled at 9, and the temperature of the precipitation tank is controlled at 60℃. After precipitation, allow the solution to stand for 3 hours to age.

[0068] The filter cake was filtered and washed four times with a deionized water to filter cake volume ratio of 7:1. The resulting filter cake I was then washed once more with anhydrous ethanol under ultrasonic assistance, with an anhydrous ethanol to filter cake volume ratio of 5:1. This was followed by filtration to obtain filter cake II. Filter cake II was then placed in a freeze-drying oven at -30°C for 5 hours and subsequently calcined in a muffle furnace at 1450°C for 2 hours to obtain a magnesium-aluminum composite oxide support, denoted as Mg-Al-3. Characterized by isothermal nitrogen adsorption, its specific surface area was 37 m² / s. 2 / g; based on the magnesium-aluminum composite oxide carrier, the K2O content in the carrier is 1.8% by mass.

[0069] (2) Preparation of methane dry reforming catalyst

[0070] 2.12 g of Ni(NO3)2·6H2O and 0.2 g of P123 were weighed and dissolved in 5.6 mL of deionized water. This impregnation solution was then used to impregnate 4 g of the carrier obtained in step (1). After standing for 1 hour, the carrier was vacuum dried in a rotary evaporator and then dried in an oven at 100 °C for 10 hours. The dried sample was then calcined in a muffle furnace at 400 °C for 5 hours. The resulting methane dry reforming catalyst was designated as Ni / Mg-Al-3. The dispersion of the Ni metal active component in the catalyst, as determined by hydrogen chemisorption, was 11.4%, and the average particle size of the Ni metal active component was 7.2 nm.

[0071] (3) Application of methane dry reforming catalysts

[0072] The catalyst was activated and a dry reforming reaction of methane was carried out under the same conditions as in Example 1. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4=85.4%, X CO2 =84.2%, H2 / CO = 1.00. After 50 hours of reaction, coking analysis was performed on the unloaded catalyst, and the calculated coking rate was 0.071 mgC / g. cat ·h.

[0073] Example 4

[0074] (1) Preparation of magnesium-aluminum composite oxide carrier

[0075] The magnesium-aluminum composite oxide support was prepared using the same method as in Example 1, except that acetone was used as the organic solvent for ultrasonic treatment of the water-washed filter cake I. The resulting magnesium-aluminum composite oxide support was designated Mg-Al-4. Characterized by isothermal nitrogen adsorption, its specific surface area was 35 m² / g. 2 / g; based on the magnesium-aluminum composite oxide carrier, the K2O content in the carrier is 2.5% by mass.

[0076] (2) Preparation of methane dry reforming catalyst

[0077] A methane dry reforming catalyst, denoted as Ni / Mg-Al-4, was prepared by loading the active metal Ni in the same manner as in Example 1, followed by drying and calcination. The dispersion of the Ni metal active component in the catalyst, as measured by hydrogen chemisorption, was 12.9%, and the average particle size of the Ni metal active component was 7.6 nm.

[0078] (3) Application of methane dry reforming catalysts

[0079] The catalyst was activated and a dry reforming reaction of methane was carried out under the same conditions as in Example 1. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4 =81.7%, X CO2 =80.5%, H2 / CO = 1.02. After 50 hours of reaction, coking analysis was performed on the unloaded catalyst, and the calculated coking rate was 0.043 mgC / g. cat ·h.

[0080] Example 5

[0081] (1) Preparation of magnesium-aluminum composite oxide carrier

[0082] The support was prepared using the same method as in Example 1, except that the precipitant was replaced with 14.0 g of pure KOH. The resulting support was designated Mg-Al-5 and characterized by isothermal nitrogen adsorption, showing a specific surface area of ​​32 m². 2 / g; the K2O content in the carrier is 2.4%.

[0083] (2) Preparation of methane dry reforming catalyst

[0084] The active metal Ni was supported in the same manner as in Example 1, and the resulting catalyst was designated Ni / Mg-Al-5. The dispersion of the Ni metal active component in the catalyst was 12.4%, and the average particle size of the Ni metal active component was 7.7 nm, as determined by hydrogen chemisorption.

[0085] (3) Application of methane dry reforming catalysts

[0086] The catalyst was activated and a dry reforming reaction of methane was carried out under the same conditions as in Example 1. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4 =83.1%, X CO2 =82.6%, H2 / CO = 1.03. After 50 hours of reaction, coking analysis was performed on the unloaded catalyst, and the calculated coking rate was 0.076 mg C / g. cat ·h.

[0087] Comparative Example 1

[0088] (1) Preparation of the carrier

[0089] The support was prepared using the same method as in Example 1, except that the resulting filter cake I was thoroughly washed with deionized water until the final filtrate conductivity was less than 2 μS / cm. The resulting support was designated Mg-Al-D1 and characterized by isothermal nitrogen adsorption, showing a specific surface area of ​​47 m². 2 / g; the K2O content in the carrier is 0.006% by mass.

[0090] (2) Preparation of catalyst

[0091] The catalyst, denoted as Ni / Mg-Al-D1, was prepared by loading the active metal Ni in the same manner as in Example 1, followed by drying and calcination. The dispersion of the Ni metal active component in the catalyst was 15.1%, and the average particle size of the Ni metal active component was 6.4 nm, as determined by hydrogen chemisorption.

[0092] (3) Activity evaluation

[0093] The catalyst was activated and a dry reforming reaction of methane was carried out under the same conditions as in Example 1. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4 =86.3%, X CO2 =85.2%, H2 / CO = 1.01. Coking analysis was performed on the unloaded catalyst after 50 hours of reaction, and the calculated coking rate of the catalyst was 0.107 mgC / g. cat ·h.

[0094] Comparative Example 2

[0095] (1) Preparation of the carrier

[0096] The support was prepared using the same method as in Example 1, except that the filter cake I after washing with deionized water was not subjected to ultrasonic dispersion with an organic solvent, but was directly vacuum dried. The resulting support was designated Mg-Al-D2 and characterized by isothermal nitrogen adsorption, with a specific surface area of ​​14 m². 2 / g; the K2O content in the carrier is 2.9% by mass.

[0097] (2) Preparation of catalyst

[0098] The catalyst, denoted as Ni / Mg-Al-D2, was prepared by loading the active metal Ni in the same manner as in Example 1, followed by drying and calcination. The dispersion of the Ni metal active component in the catalyst was 8.5%, and the average particle size of the Ni metal active component was 10.6 nm, as determined by hydrogen chemisorption.

[0099] (3) Activity evaluation

[0100] The catalyst was activated and a dry reforming reaction of methane was carried out under the same conditions as in Example 1. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4 =72.1%, X CO2 =71.4%, H2 / CO = 1.02. After 50 hours of reaction, coking analysis was performed on the unloaded catalyst, and the calculated coking rate was 0.143 mgC / g. cat ·h.

[0101] Comparative Example 3

[0102] (1) Preparation of the carrier

[0103] The support was prepared using the same method as in Example 1, except that the calcination temperature was 1000℃. The resulting support was designated Mg-Al-D3 and characterized by isothermal nitrogen adsorption, showing a specific surface area of ​​67 m². 2 / g; the K2O content in the carrier is 2.8% by mass.

[0104] (2) Preparation of catalyst

[0105] The catalyst, denoted as Ni / Mg-Al-D3, was prepared by loading the active metal Ni in the same manner as in Example 1, followed by drying and calcination. The dispersion of the Ni metal active component in this catalyst, measured by hydrogen chemisorption, was 17.1%, and the average particle size of the Ni metal active component was 4.9 nm. This demonstrates that a larger specific surface area of ​​the support is indeed beneficial for the dispersion and loading of the active metal.

[0106] (3) Activity evaluation

[0107] The catalyst was activated and a dry reforming reaction of methane was carried out under the same conditions as in Example 1. The composition of the tail gas was analyzed by online gas chromatography. X was calculated. CH4 =93.3%, X CO2 =92.5%, H2 / CO =1.01.

[0108] During the 50-hour reaction process, the catalyst's catalytic activity was continuously deactivated, with its methane conversion rate decreasing from 93.3% initially to 81.2% after 50 hours. This indicates that the high-temperature stability of the support has a significant impact on the catalyst's reaction stability. Therefore, the support prepared in this invention has undergone high-temperature calcination treatment, which can effectively maintain the catalyst's activity stability during high-temperature reactions.

[0109] After 50 hours of reaction, coking analysis was performed on the unloaded catalyst, and the calculated coking rate was 0.039 mgC / g. cat ·h.

[0110] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a methane dry reforming catalyst using a magnesium-aluminum composite oxide support, characterized in that, The magnesium-aluminum composite oxide carrier is impregnated with an impregnation solution, then dried and calcined. The impregnation solution contains a soluble compound of active metal Ni and a surfactant P123. The magnesium-aluminum composite oxide carrier is composed of MgAl2O4 spinel and potassium oxide. Based on the magnesium-aluminum composite oxide carrier, the mass fraction of potassium oxide is 0.1–4%, and the specific surface area of ​​the magnesium-aluminum composite oxide carrier is 15–60 m². 2 / g; The preparation method of magnesium-aluminum composite oxide support includes: (1) Weigh out the specified amounts of soluble aluminum salt and soluble magnesium salt to prepare a mixed salt solution; (2) Weigh KOH and / or K2CO3 to prepare a precipitant; (3) The mixed salt solution and the precipitant are separately added dropwise into the precipitation tank for co-precipitation using the co-flow co-precipitation method; (4) After sedimentation, allow the mixture to stand and age. (5) Filter cake I is obtained by filtration and washing. It is washed with deionized water. The amount of washing solvent and the number of washing times are controlled to control the amount of potassium oxide contained in the magnesium-aluminum composite oxide carrier after calcination. (6) Filter cake I is ultrasonically dispersed in an organic solvent, wherein the organic solvent is one or more selected from methanol, ethanol, diethyl ether, and acetone, and then filtered to obtain filter cake II; (7) After drying, filter cake II is calcined at 1250-1450℃ for 2-10 hours to obtain magnesium-aluminum composite oxide carrier.

2. The preparation method according to claim 1, characterized in that, Based on a magnesium-aluminum composite oxide carrier, the mass fraction of potassium oxide is 0.5-3%, and the specific surface area of ​​the magnesium-aluminum composite oxide carrier is 20-55 m². 2 / g.

3. The preparation method according to claim 1, characterized in that, Soluble aluminum salts are selected from one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, or their hydrates; Soluble magnesium salts are selected from one or more of magnesium nitrate, magnesium sulfate, magnesium chloride, or their hydrates; The molar ratio of magnesium ions to aluminum ions in the solution is based on the stoichiometric ratio required for the complete formation of MgAl2O4 spinel; the total metal ion concentration in the mixed salt solution is 0.1–0.5 mol / L.

4. The preparation method according to claim 3, characterized in that, The total metal ion concentration in the mixed salt solution is 0.2–0.4 mol / L.

5. The preparation method according to claim 1, characterized in that, The molar ratio of KOH and K2CO3 in the precipitant is (OH) - ):(CO3 2- The precipitant solution is prepared by mixing a ratio of 0.5 to 5:1, and the concentration of the precipitant solution, expressed as the molar concentration of alkali metal ions, is 0.2 to 5 mol / L.

6. The preparation method according to claim 1, characterized in that, The molar ratio of KOH and K2CO3 in the precipitant is (OH) - ):(CO3 2- The precipitant solution is prepared by mixing 1 to 4:1, and the concentration of the precipitant solution, expressed as the molar concentration of alkali metal ions, is 0.5 to 2 mol / L.

7. The preparation method according to claim 1, characterized in that, In step (3), the mixed salt solution and the precipitant are dripped into the precipitation tank at a certain flow rate using a co-precipitation method, with the pH value of the solution in the precipitation tank being controlled to be stable at 7-13; the temperature of the precipitation tank is controlled at 25-80℃. In step (4), the settling and aging time after precipitation is 1 to 10 hours.

8. The preparation method according to claim 1, characterized in that, In step (3), the pH value of the solution in the sedimentation tank is controlled to be stable at 8-12; the temperature of the sedimentation tank is controlled at 40-80℃. In step (4), the settling and aging time after precipitation is 1.5 to 5 hours.

9. The preparation method according to claim 1, characterized in that, In step (5), the ratio of the volume of deionized water to the volume of filter cake in each wash is 3 to 10:1, and the number of washes is 2 to 6.

10. The preparation method according to claim 1, characterized in that, In step (6), filter cake I is placed in an organic solvent and ultrasonically dispersed to ensure uniform dispersion in the organic solvent and maintained for 0.5 to 3 hours; the volume ratio of the organic solvent to filter cake I is 3 to 10:

1.

11. The preparation method according to claim 1, characterized in that, In step (7), the filter cake II is dried by one or more of the following methods: drying in ordinary static air, drying in flowing air, freeze drying, or vacuum drying, for a drying time of 1 to 20 hours; The roasting temperature is 1300-1400℃, and the roasting time is 1-10 hours.

12. The preparation method according to claim 1, characterized in that, In step (7), the filter cake II is dried by freeze drying or vacuum drying for 2 to 10 hours; The roasting time is 2 to 5 hours.

13. The preparation method according to claim 1, characterized in that, In the impregnation solution, the molar ratio of surfactant P123 to active metal Ni atoms is 0.01–2; in the impregnation solution, the concentration of soluble compounds of active metal Ni, calculated as metal elements, is 14.6–191.6 g / L; and the amount of support used is such that the content of active metal Ni component, calculated as metal elements, in the obtained catalyst is 2–20% by weight, based on the total amount of catalyst.

14. The preparation method according to claim 1, characterized in that, In the impregnation solution, the molar ratio of surfactant P123 to active metal Ni atoms is 0.01 to 1; the amount of support is such that the content of active metal Ni component in the obtained catalyst, based on the total amount of catalyst and calculated as metal element, is 3 to 15% by weight.

15. The preparation method according to claim 1, characterized in that, The content of the active metal Ni component, calculated as a metal element, is 4–12% by weight.

16. The preparation method according to claim 1, characterized in that, The drying temperature is 80–140℃ and the time is 1–10 hours; the calcination temperature is 400–1000℃ and the time is 1–10 hours.

17. The preparation method according to claim 16, characterized in that, The roasting temperature is 450–700℃, and the time is 2–5 hours.

18. The preparation method according to claim 1, characterized in that, In the methane dry reforming catalyst, the dispersion of metallic Ni is 8-30%, and the grain size of metallic Ni is 2-10 nm.

19. The preparation method according to claim 18, characterized in that, In the methane dry reforming catalyst, the dispersion of metallic Ni is 10-25%, and the grain size of metallic Ni is 3-8 nm.

20. The methane dry reforming catalyst prepared by any of the methods described in claims 1 to 19.

21. A method for using a methane dry reforming catalyst prepared by any one of claims 1 to 19 in the dry reforming of methane to produce syngas, characterized in that, Methane and CO2 are reacted in a fixed-bed reactor in the presence of a methane dry reforming catalyst to produce syngas. The molar ratio of methane to carbon dioxide is 0.7–1.1:1; the reaction temperature is 550–950℃; the pressure is 0–3 MPa; and the feed gas space velocity is 2000–120000 mL·g. -1 ·h -1 .

22. The application method according to claim 21, characterized in that, The molar ratio of methane to carbon dioxide is 0.8–1.0:1; the reaction temperature is 600–850℃; the pressure is 0–1 MPa; and the feed gas hourly space velocity is 60,000–120,000 mL·g. -1 ·h -1 .

23. The application method according to claim 22, characterized in that, The reaction temperature is 700–800℃.

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