Application of nickel-based catalyst in preparation of carbon monoxide and hydrogen by partial oxidation of methane

Abstract

The invention relates to a preparation method of a Ni-based catalyst taking a nanoscale commercial gamma-Al2O3 material as a carrier and a catalytic application of the Ni-based catalyst in a process of preparing carbon monoxide and hydrogen by partially oxidizing methane. The preparation method comprises the following steps: preparing metal Ni nano-particles and loading the metal Ni nano-particles on an Al2O3 carrier. Compared with a catalyst prepared by a common impregnation method, the Ni / Al2O3 catalyst prepared by the invention has obviously higher catalytic methane partial oxidation activity at the same reaction temperature. Wherein related species for oxidizing Ni are active centers of the reaction; al2O3 has a good active center dispersion effect, so that the reaction activity is improved. The preparation method of the catalyst is simple in process, raw materials are easy to obtain, the catalyst is suitable for large-scale catalyst production, and the activity of the catalyst can be improved on the basis of an existing catalyst preparation process.

Description

Technical Field

[0001] The present invention belongs to the field of industrial applications, and relates to the preparation of a catalyst and the study of its catalytic partial oxidation activity for methane. Specifically, it relates to the preparation process of a catalyst with nano-nickel particles supported on an Al 2 O 3 carrier and its application in the reaction of partial oxidation of methane to syngas (carbon monoxide and hydrogen) under the condition that the reactants are in a stoichiometric ratio. Background Art

[0002] With the rapid growth of energy demand and the increasingly severe environmental pollution problems, seeking clean energy to replace highly polluting fossil fuels such as coal and oil has become the main development direction in the energy field. Although wind energy, photovoltaic energy, nuclear power, hydrogen energy, etc. have become hot topics attracting wide attention in recent years, due to practical difficulties such as unstable energy supply, large upfront equipment investment, high potential safety risks, and the inability of preparation costs and storage and transportation efficiency to meet actual needs, fossil fuels will still be the main component of energy supply in the coming decades. Among the three major fossil fuels: coal, oil, and natural gas, natural gas has become the focus of research and application in the energy field in recent decades due to its advantages such as wide distribution, low price, multiple storage and transportation methods, being able to be directly used as fuel or deeply utilized in the natural gas industry, and having low pollution and low emissions during use.

[0003] Methane, which is the main component of natural gas and accounts for more than 90% of the content in natural gas, can not only directly provide energy for production and life through power generation, firing, driving natural gas vehicles and other means of transportation, but also become an important C1 raw material for the production of bulk chemicals through chemical processes such as direct conversion, oxidative coupling, anaerobic dehydrogenation, steam reforming, and dry reforming. In addition, methane not only exists in natural gas, but with the advancement of the "shale revolution" and "flammable ice" mining technology in the past 20 years, as well as the implementation and practical application of biogas production technology from biomass, the scope and intensity of the use of methane as an important energy and chemical raw material will continue to expand. One of the important ways to industrially utilize methane is to convert methane into carbon monoxide and hydrogen through the steam reforming process, and then prepare carbon-containing chemical products through methanol synthesis, Fischer-Tropsch synthesis and other ways. In addition, the hydrogen produced in the steam reforming process is also considered an important clean energy and can be applied to scenarios such as hydrogen fuel cells. Currently, methane is still the main raw material for hydrogen production.

[0004] However, the steam reforming reaction is a strongly endothermic process thermodynamically. To obtain a high methane conversion rate and product selectivity, a high temperature above 1000 °C is often required in actual operation. This requires a large amount of energy and economic costs to maintain the continuous progress of the reaction. The partial oxidation of methane with oxygen as the oxidant is an exothermic reaction thermodynamically and can produce carbon monoxide and hydrogen at a relatively low temperature (600 - 800 °C). However, in the currently industrialized applications, restricted by the catalyst activity, the production under the temperature condition of 600 - 700 °C cannot be achieved yet. The relatively high reaction temperature not only requires additional energy and economic costs but also shortens the catalyst life due to reasons such as sintering of active components and catalyst carbon deposition. Therefore, there is an urgent need to develop a new type of highly active catalyst for the partial oxidation of methane.

[0005] Based on the above research status, it is of great significance to seek a relatively simple method to prepare a highly active catalyst for the partial oxidation of methane and apply it to the catalytic partial oxidation reaction of methane. This patent aims to invent a highly active catalyst for the partial oxidation of methane containing Ni. Summary of the Invention

[0006] The purpose of the present invention is to provide a nickel-based catalyst for the reaction of partial oxidation of methane to produce carbon monoxide and hydrogen, and this catalyst has the characteristics of high activity and high stability for the partial oxidation reaction of methane.

[0007] The preparation method of the nickel-based catalyst in the present invention is specifically realized according to the following steps:

[0008] 1. Carrier heat treatment: Heat the carrier γ-phase Al 2 O 3 from room temperature to 600 - 900 °C in still air and calcine for 1 - 5 h to ensure that the carrier structure does not change during the subsequent preparation process.

[0009] 2. Preparation of metal nickel nanoparticles: Add a certain amount of nickel nitrate aqueous solution to a mixed solution composed of a certain amount of cetyltrimethylammonium bromide, n-butanol, and cyclohexane, heat the mixed solution to 60 - 80 °C, and keep it warm for 0.5 - 2 h under stirring; dissolve 20 - 50 mg of sodium borohydride in 0.2 - 1 mL of deionized water and add it to the above solution. The solution color quickly turns black, and a dispersion of metal nickel nanoparticles is obtained. Among them, the amount of cetyltrimethylammonium bromide used is 2 - 10 g, the amount of n-butanol used is 10 - 20 mL, the amount of cyclohexane used is 60 - 100 mL, and the addition amount of the nickel nitrate aqueous solution is adjusted according to the nickel loading in the final catalyst.

[0010] 3. Add 0.3 - 1 g of the calcined carrier γ-phase Al with a high specific surface area 2 O 3Immerse it in the metal nickel nanoparticle dispersion obtained in Step 2, where the mass percentage of nickel in the catalyst is 0.2 - 1.6 wt%; stir rapidly for 1 min, add 30 - 80 mL of ethanol and then centrifuge, wash ultrasonically with ethanol multiple times, let it stand in air at room temperature for 6 - 24 h, and then dry it in an oven at 30 - 120 °C for 2 - 24 h; fully grind the dried solid above for 10 - 30 min, then calcine it in still air at 400 - 600 °C for 2 - 12 h, and slowly cool it to room temperature to obtain a fresh catalyst. Reduce the freshly prepared catalyst above under hydrogen with different concentrations, where the volume percentage of hydrogen is 20 - 100%, and the rest is an inert gas such as He, Ar or N 2 , with a reduction temperature of 400 - 700 °C and a reduction time of 15 - 120 min, to obtain the catalyst required for the reaction.

[0011] The conditions for the partial oxidation of methane are as follows: the volume percentage of methane is 0.4 - 6%, the volume percentage of oxygen is 0.2 - 3%, the volume percentage of carbon monoxide is 0 - 6%, the volume percentage of hydrogen is 0 - 12%, the volume percentage of water gas is 0 - 6%, the volume percentage of carbon dioxide is 0 - 3%, and the rest is an inert gas such as He, Ar or N 2 or one or more of them; the reaction temperature is 550 - 800 °C, and the mass space velocity is 30000 - 300000 mL g 催化剂 -1 h -1 The total pressure of the reaction gas is 0.1 - 0.2 MPa.

[0012] The catalyst preparation conditions provided in the present invention are mild, the process is simple, and it is suitable for large-scale production.

[0013] The catalyst reaction conditions provided in the present invention are mild. Compared with the existing industrial steam reforming process, the reaction temperature is lower, which is beneficial to reducing production costs and is suitable for large-scale industrial applications.

[0014] The Ni / Al 2 O 3 catalyst obtained in the present invention has significantly higher catalytic activity for the partial oxidation of methane to carbon monoxide and hydrogen than the catalyst prepared by the ordinary impregnation method at the same reaction temperature. Among them, nickel oxide is the active center of the reaction; Al 2 O 3 plays a good role in dispersing the active centers and improves the reaction activity. The preparation method of the catalyst in the present invention has a simple process flow, easily available raw materials, is suitable for large-scale catalyst production, and can improve the catalyst activity on the basis of the existing catalyst preparation process.

[0015] The present invention will be described in detail below with specific embodiments. It should be noted that these embodiments are only examples and do not constitute any limitation to the essence and scope of the present invention. The present invention can be implemented as long as it meets the conditions described in the content part of the present invention. Therefore, the protection scope of the present invention is subject to the claims of the application. Description of the Drawings

[0016] Figure 1 TEM image of the high-temperature heat-treated support nano-Al 2 O 3 obtained in Example 1.

[0017] Figure 2 TEM image of the metal nickel nanoparticle dispersion obtained in Example 2.

[0018] Figure 3 TEM image after the reduction of Example 1 in pure hydrogen at 500 °C for 1 hour.

[0019] Figure 4 Performance changes of Examples 3-5 and Comparative Examples 1-3 in the partial oxidation of methane at 650 °C with reaction time, Figure 4 A shows the change in the conversion rate of the raw material methane, Figure 4 B shows the change in the selectivity of the product carbon monoxide, Figure 4 B shows the change in the selectivity of the product hydrogen, Figure 4 D shows the change in the ratio of the hydrogen and carbon monoxide concentrations in the product.

[0020] Figure 5 TEM image of Example 3 after 90 hours of catalytic partial oxidation of methane.

[0021] Figure 6 High-resolution TEM image of Example 3 after 90 hours of catalytic partial oxidation of methane.

[0022] Figure 7 Performance changes of the catalytic partial oxidation of methane at 650 °C corresponding to Example 9 with reaction time.

[0023] Figure 8 Performance changes of the catalytic partial oxidation of methane at 650 °C corresponding to Example 10 with reaction time.

[0024] Figure 9 Performance changes of the catalytic partial oxidation of methane at 650 °C corresponding to Example 11 with reaction time.

[0025] Figure 10 Performance changes of the catalytic partial oxidation of methane at 650 °C corresponding to Example 12 with reaction time.

[0026] Figure 11 Performance variation of catalytic partial oxidation of methane at 600 - 670 °C corresponding to Example 13 with reaction temperature.

[0027] Figure 12 Performance variation of catalytic partial oxidation of methane at 800 °C corresponding to Example 14 with reaction time. Detailed implementation modes

[0028] The technical solution of the present invention includes but is not limited to the following detailed implementation modes:

[0029] Example 1.

[0030] Nanometer Al 2 O 3 support:

[0031] Accurately weigh 2.0 g of commercial γ-phase Al 2 O 3 , put it into a crucible, heat it from room temperature to 850 °C in a muffle furnace at a heating rate of 2 °C / min, calcine for 2 h and then cool it to room temperature naturally, thus obtaining the nanometer Al 2 O 3 support (denoted as nanometer Al 2 O 3 ), the support composition is pure γ-phase Al 2 O 3 , the support shape is nanorod-like, with a length of 20 - 200 nm and a diameter of 5 - 25 nm.

[0032] Example 2.

[0033] Preparation of metal nickel nanoparticles:

[0034] Dilute 136 μL of 0.5 mol / L Ni(NO 3 ) 2 aqueous solution to 4 mL with deionized water, then add it to a mixed solution composed of 5.9 g of cetyltrimethylammonium bromide, 15 mL of n-butanol, and 80 mL of cyclohexane. Heat the mixed solution to 70 °C and keep it warm for 1 h under stirring; dissolve 35 mg of sodium borohydride in 0.5 mL of deionized water and add it to the above solution. The solution color quickly turns black, thus obtaining a metal nickel nanoparticle dispersion. The diameter of the metal nickel nanoparticles is 0.5 - 3 nm.

[0035] Example 3.

[0036] Preparation of 0.8 wt% Ni / Al 2 O 3 -ME catalyst using the metal nickel nanoparticle dispersion as a precursor:

[0037] At room temperature (~25 °C), 0.5 g of the nano-Al heat-treated at high temperature in Example 1 was added to the metal nickel nanoparticle dispersion obtained in Example 2 2 O 3 , after stirring for 1 min, 40 mL of ethanol was added, and the solid was separated by centrifugation at 7000 r / min for 1 min. The obtained solid was ultrasonically centrifuged and washed with ethanol 3 times. Finally, the obtained solid was dispersed in 10 mL of ethanol to form a black suspension. After standing for 12 h, the ethanol was evaporated at 70 °C and then dried in an oven at 80 °C for another 12 h. After drying, the sample was ground and placed in a muffle furnace. It was heated from room temperature (~25 °C) to 500 °C at a heating rate of 5 °C / min in air and held for 4 h, and then slowly cooled to room temperature. The obtained sample was heated from room temperature (~25 °C) to 500 °C at a heating rate of 10 °C / min in hydrogen and held for 1 h for reduction, and then the 0.8 wt% Ni / Al 2 O 3 -ME catalyst prepared using the metal nickel nanoparticle dispersion as the precursor was obtained. The diameter of the metal nickel nanoparticles was 4 - 7 nm.

[0038] Example 4.

[0039] Preparation of 0.4 wt% Ni / Al 2 O 3 -ME catalyst using the metal nickel nanoparticle dispersion as the precursor:

[0040] At room temperature (~25 °C), 1.0 g of the nano-Al heat-treated at high temperature in Example 1 was added to the metal nickel nanoparticle dispersion obtained in Example 2 2 O 3 , after stirring for 1 min, 40 mL of ethanol was added, and the solid was separated by centrifugation at 7000 r / min for 1 min. The obtained solid was ultrasonically centrifuged and washed with ethanol 3 times. Finally, the obtained solid was dispersed in 10 mL of ethanol to form a black suspension. After standing for 12 h, the ethanol was evaporated at 70 °C and then dried in an oven at 80 °C for another 12 h. After drying, the sample was ground and placed in a muffle furnace. It was heated from room temperature (~25 °C) to 500 °C at a heating rate of 5 °C / min in air and held for 4 h, and then slowly cooled to room temperature. The obtained sample was heated from room temperature (~25 °C) to 500 °C at a heating rate of 10 °C / min in hydrogen and held for 1 h for reduction, and then the 0.4 wt% Ni / Al 2 O 3 -ME catalyst prepared using the metal nickel nanoparticle dispersion as the precursor was obtained. The diameter of the metal nickel nanoparticles was 4 - 7 nm.

[0041] Example 5.

[0042] 0.2 wt% Ni / Al using the metal nickel nanoparticle dispersion as the precursor2 O 3 -ME Catalyst Preparation:

[0043] At room temperature (~25 °C), 2.0 g of the nano-Al that had been heat-treated at high temperature in Example 1 was added to the metal nickel nanoparticle dispersion obtained in Example 2. 2 O 3 After stirring for 1 min, 40 mL of ethanol was added. The solid was separated by centrifugation at 7000 r / min for 1 min, and the obtained solid was ultrasonically centrifuged and washed with ethanol 3 times. Finally, the obtained solid was dispersed in 10 mL of ethanol to form a black suspension. After standing for 12 h, the ethanol was evaporated to dryness at 70 °C and then dried in an oven at 80 °C for another 12 h. After drying, the sample was ground and placed in a muffle furnace. It was heated from room temperature (~25 °C) to 500 °C at a heating rate of 5 °C / min in air and held for 4 h, and then slowly cooled to room temperature. The obtained sample was heated from room temperature (~25 °C) to 500 °C at a heating rate of 10 °C / min in hydrogen and held for 1 h for reduction, and then the 0.2 wt% Ni / Al 2 O 3 -ME catalyst was obtained using the metal nickel nanoparticle dispersion as the precursor. The diameter of the metal nickel nanoparticles was 4 - 7 nm.

[0044] Example 6.

[0045] Catalytic Performance Evaluation of the 0.8 wt% Ni / Al 2 O 3 -ME Catalyst Prepared in Example 3:

[0046] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components was methane 5%, oxygen 2.5%, and He gas for balance, the reaction pressure was atmospheric pressure, and the space velocity of the raw material gas was 30000 mL g -1 h -1 , and the reaction temperature was 650 °C.

[0047] Example 7.

[0048] Catalytic Performance Evaluation of the 0.4 wt% Ni / Al 2 O 3 -ME Catalyst Prepared in Example 4:

[0049] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components was methane 5%, oxygen 2.5%, and He gas for balance, the reaction pressure was atmospheric pressure, and the space velocity of the raw material gas was 30000 mL g -1 h -1 , and the reaction temperature was 650 °C.

[0050] Example 8.

[0051] 0.2 wt% Ni / Al prepared in Example 5 2 O 3 -ME Catalyst Catalytic Performance Evaluation:

[0052] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, and balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 30000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0053] Example 9.

[0054] 0.8 wt% Ni / Al prepared in Example 3 2 O 3 -ME Catalyst Catalytic Performance Evaluation at Higher Space Velocity:

[0055] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, and balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 50000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0056] Example 10.

[0057] 0.8 wt% Ni / Al prepared in Example 3 2 O 3 -ME Catalyst Catalytic Performance Evaluation at Higher Space Velocity:

[0058] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, and balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 75000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0059] Example 11.

[0060] 0.8 wt% Ni / Al prepared in Example 3 2 O 3 -ME Catalyst Catalytic Performance Evaluation at Higher Space Velocity:

[0061] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, and balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 150000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0062] Example 12.

[0063] 0.8 wt% Ni / Al prepared in Example 3 2 O 3 -ME catalyst performance evaluation at higher space velocity:

[0064] Catalytic reaction conditions: Fixed-bed micro-reactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 300000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0065] Example 13.

[0066] 0.8 wt% Ni / Al prepared in Example 3 2 O 3 -ME catalyst performance evaluation at different temperatures:

[0067] Catalytic reaction conditions: Fixed-bed micro-reactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 60000 mL g -1 h -1 , and the reaction temperature is 600 - 670 °C.

[0068] Example 14.

[0069] 0.8 wt% Ni / Al prepared in Example 3 2 O 3 -ME catalyst performance evaluation at higher temperature and space velocity:

[0070] Catalytic reaction conditions: Fixed-bed micro-reactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 300000 mL g -1 h -1 , and the reaction temperature is 800 °C.

[0071] Comparative Example 1.

[0072] Preparation of 8 wt% Ni / Al 3 ) 2 IMP catalyst using an aqueous solution of Ni(NO 2 O 3 as a precursor:

[0073] At room temperature (~25 °C), measure 1360 μL (0.5 mol / L) of Ni(NO 3 ) 2 aqueous solution, dilute it to 10 mL with deionized water, and add 0.5 g of the nano-Al heat-treated at high temperature in Example 1 accurately weighed under stirring2 O 3 Continue stirring for 2 h to allow Ni(NO 3 ) 2 Adsorbed on the surface of the carrier. Heat the sample in a water bath to 80°C, and allow the water in the impregnation solution to evaporate naturally while stirring. Then place it in an 80°C oven and dry it in air for 12 hours. After drying, grind the sample and place it in a muffle furnace and heat it from room temperature (~25°C) to 500°C at a heating rate of 2°C / min and maintain it for 4 hours, then cool it down to room temperature naturally. The obtained sample was heated from room temperature (~25°C) to 500°C in hydrogen at a heating rate of 10°C / min and kept for reduction for 1 hour to obtain Ni(NO 3 ) 2 8wt% Ni / Al prepared from aqueous solution 2 O 3 IMP catalyst, in which the diameter of the metal nickel nanoparticles is 15-30nm.

[0074] Comparative Example 2.

[0075] Take Ni(NO 3 ) 2 Aqueous solution is a 0.8wt% Ni / Al precursor 2 O 3 -IMP catalyst preparation:

[0076] At room temperature (~25°C), 136 μL (0.5 mol / L) Ni(NO 3 ) 2 The aqueous solution was diluted to 10 mL with deionized water, and 0.5 g of nano-Al2O3, which had been heat-treated at high temperature in Example 1, was added under stirring. 2 O 3 Continue stirring for 2 h to allow Ni(NO 3 ) 2 Adsorbed on the surface of the carrier. Heat the sample in a water bath to 80°C, and allow the water in the impregnation solution to evaporate naturally while stirring. Then place it in an 80°C oven and dry it in air for 12 hours. After drying, grind the sample and place it in a muffle furnace and heat it from room temperature (~25°C) to 500°C at a heating rate of 2°C / min and maintain it for 4 hours, then cool it down to room temperature naturally. The obtained sample was heated from room temperature (~25°C) to 500°C in hydrogen at a heating rate of 10°C / min and kept for reduction for 1 hour to obtain Ni(NO 3 ) 2 Aqueous solution was used as the precursor to prepare 0.8wt% Ni / Al 2 O 3 -IMP catalyst, in which the diameter of the metal nickel nanoparticles is 5-10nm.

[0077] Comparative Example 3.

[0078] 0.8 wt% Ni / Al without hydrogen reduction using a metal nickel nanoparticle dispersion as a precursor 2 O 3 -caicined catalyst preparation:

[0079] At room temperature (~25 °C), 0.5 g of the nano-Al heat-treated at high temperature in Example 1 was added to the metal nickel nanoparticle dispersion obtained in Example 2 2 O 3 , after stirring for 1 min, 40 mL of ethanol was added, and the solid was separated by centrifugation at 7000 r / min for 1 min. The obtained solid was ultrasonically centrifuged and washed with ethanol 3 times. Finally, the obtained solid was dispersed in 10 mL of ethanol to form a black suspension. After standing for 12 h, the ethanol was evaporated to dryness at 70 °C and then further dried in an oven at 80 °C for 12 h. After drying, the sample was ground and placed in a muffle furnace. It was heated from room temperature (~25 °C) to 500 °C at a heating rate of 5 °C / min in air and held for 4 h, and then slowly cooled to room temperature to obtain the 0.8 wt% Ni / Al without hydrogen reduction using a metal nickel nanoparticle dispersion as a precursor 2 O 3 -caicined catalyst. The diameter of the nickel oxide nanoparticles is 8 - 15 nm.

[0080] Comparative Example 4.

[0081] Catalytic performance evaluation of the 8 wt% Ni / Al 2 O 3 IMP catalyst prepared in Comparative Example 1:

[0082] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, and balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 30000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0083] Comparative Example 5.

[0084] Catalytic performance evaluation of the 0.8 wt% Ni / Al 2 O 3 IMP catalyst prepared in Comparative Example 2:

[0085] Catalytic reaction conditions: Fixed-bed microreactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, and balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 30000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0086] Comparative Example 6.

[0087] The 0.8 wt% Ni / Al prepared in Comparative Example 3 2 O 3 -calcined catalyst catalytic performance evaluation:

[0088] Catalytic reaction conditions: fixed-bed microreactor, the volume ratio of the raw material gas components is 5% methane, 2.5% oxygen, and balanced with He gas, the reaction pressure is atmospheric pressure, and the space velocity of the raw material gas is 30000 mL g -1 h -1 , and the reaction temperature is 650 °C.

[0089] Figure 1 The transmission electron microscope photo of nano-Al in Example 1 is given. It can be seen that the nano-rod-shaped Al 2 O 3 support has a length of 20 - 200 nm and a diameter of 5 - 25 nm. The morphology of its nanorods can effectively disperse metal nickel nanoparticles, prevent nickel particles from aggregating under high-temperature reaction conditions, and thus improve the activity and stability of the catalyst. 2 O 3 The transmission electron microscope photo of Example 2 is given. It can be seen that the prepared metal nickel nanoparticles have a particle size of 0.5 - 3 nm and a uniform particle size distribution. Using this as a precursor to prepare the catalyst can obtain nickel nanoparticles with small and uniform particle sizes. Such nickel nanoparticles can effectively improve the dispersion degree of nickel atoms and are beneficial to improving the reaction activity of the catalyst.

[0090] Figure 2 The transmission electron microscope photo of Example 3 is given. It can be seen that the particle size of the metal nickel nanoparticles in the 0.8 wt% Ni / Al

[0091] Figure 3 O 2 O 3 -ME catalyst is 4 - 7 nm and the distribution is uniform.

[0092] Figure 4 The changes of the conversion rate of raw material methane, the selectivity of product carbon monoxide, the selectivity of hydrogen, and the ratio of hydrogen to carbon monoxide concentrations in the product with reaction time during the catalytic partial oxidation of methane to carbon monoxide and hydrogen at 650 °C and a space velocity of 30000 mL g -1 h -1 are given for the catalysts prepared in Examples 3 - 5 and Comparative Examples 1 - 3. It can be seen that the 0.8 wt% Ni / Al 2 O 3 -ME and 0.4 wt% Ni / Al 2 O 3 -ME catalysts prepared with metal nickel nanoparticles as precursors show significantly better activity, selectivity, and stability. Further reducing the nickel loading, it can be seen that 0.2 wt% Ni / Al2 O 3 The stability of the -ME catalyst decreases, indicating that an appropriate nickel loading is important for the continuous progress of the catalytic reaction. As a comparison, in Figure 4 we present the methane conversion rates during the catalytic reaction of 0.8 wt% Ni / Al 2 O 3 -calcined, 0.8 wt% Ni / Al 2 O 3 -IMP, and 8.0 wt% Ni / Al 2 O 3 -IMP. It can be seen that for the 0.8 wt% Ni / Al 2 O 3 -calcined and 0.8 wt% Ni / Al 2 O 3 -IMP catalysts, only about 12.5% of methane is converted and no carbon monoxide and hydrogen are detected. This indicates that preparing the catalyst with metal nickel nanoparticles as the precursor can effectively improve the activity of the catalyst at low loadings, and the hydrogen reduction process before the reaction is crucial for the catalyst activity. For the 8.0 wt% Ni / Al 2 O 3 -IMP catalyst, the methane conversion rate is significantly lower than that of the 0.8 wt% Ni / Al 2 O 3 -ME and 0.4 wt% Ni / Al 2 O 3 -ME catalysts; and as the reaction time extends, both the methane conversion rate and the carbon monoxide selectivity gradually decrease, indicating that the high-loading catalyst prepared by the ordinary impregnation method has poor activity and stability due to the large particle size of nickel particles.

[0093] Figure 5 Present the transmission electron microscopy images of the 0.8 wt% Ni / Al 2 O 3 -ME catalyst after 90 h of long-term partial oxidation of methane reaction in Example 3. It can be seen that the particle size of nickel particles in the catalyst is 8 - 15 nm at this time and the distribution is still uniform. Figure 6 Furthermore, the high-resolution transmission electron microscopy images of the catalyst after 90 h of reaction are presented. It can be found that the nickel particles in the catalyst expose the crystal lattice of nickel oxide and exist in the state of nickel oxide, indicating that nickel oxide is very likely the active phase of the catalytic reaction.

[0094] Figure 7-10 Present the corresponding catalytic performance curves for Examples 9 - 12. It can be seen that when increasing the reaction space velocity to 50000 mL g -1 h -1 ⁻¹, 75000 mL g -1 h-1 and 150000 mL g -1 h -1 under the conditions of, 0.8 wt% Ni / Al 2 O 3 -ME catalyst can still maintain good catalytic activity, selectivity and stability. Until the space velocity increases to 30000 mL g -1 h -1 when, 0.8 wt% Ni / Al 2 O 3 -ME catalyst shows a slow and uniform deactivation phenomenon. This indicates that the 0.8 wt% Ni / Al 2 O 3 -ME catalyst prepared with metal nickel nanoparticles as the precursor can tolerate harsh high space velocity reaction conditions, meeting the important conditions for becoming an industrial catalyst.

[0095] Figure 11 Give the catalytic performance curve of the 0.8 wt% Ni / Al 2 O 3 -ME catalyst under variable temperature conditions in Example 3. It can be seen that in the temperature range of 600 - 670 °C, the catalyst shows good stability at each temperature, and the changes in the activity and selectivity of the catalyst between different temperatures are not significant. The methane conversion rate always remains above 75%, especially when the reaction temperature is restored, the catalyst can show the same performance. This indicates that the catalyst can adapt to a certain range of temperature changes and maintain high activity, selectivity and stability, which provides a wider range of reaction conditions for the industrial application of this catalyst.

[0096] Figure 12 Give the 0.8 wt% Ni / Al in Example 3 2 O 3 -ME catalyst's performance curve for partial oxidation of methane under the conditions of 800 °C high temperature and 300000 mL g -1 h -1 high space velocity. It can be seen that the 0.8 wt% Ni / Al 2 O 3 -ME catalyst can still show good stability under harsh reaction conditions.

[0097] Combining the characterization data and activity data, we believe that: The Ni / Al 2 O 3 catalyst prepared with metal nickel nanoparticles as the precursor has good catalytic performance for the reaction of partial oxidation of methane to carbon monoxide and hydrogen; this kind of Ni / Al 2 O 3The catalytic active phase of the catalyst for the partial oxidation of methane is nickel oxide; it can maintain good activity, selectivity and stability under different conditions such as nickel loading, space velocity, temperature, etc.; this Ni / Al 2 O 3 catalyst is expected to become an efficient catalyst for the industrial application of the partial oxidation of methane.

Claims

1. Application of nickel-based catalyst in partial oxidation of methane to carbon monoxide and hydrogen, Characterized in that: The nickel-based catalyst used is a supported nickel-based catalyst. Before the reaction of partial oxidation of methane to produce carbon monoxide and hydrogen is initiated, nickel in the nickel-based catalyst exists in the form of metallic nickel nanoparticles. After the reaction is initiated, it is converted into nickel oxide nanoparticles as the active component; the carrier is a nanoscale γ-Al 2 O 3 material; the total mass percentage content of nickel in the catalyst is 0.2-1.6 wt% (preferably 0.7-1.0 wt%); The carrier composition is pure γ-phase Al 2 O 3 , the carrier is in the shape of nanorods, with a length of 20 - 200 nm and a diameter of 5 - 25 nm; Before the initiation of the reaction, the particle size of nickel is 4 - 7 nm, and after the initiation of the reaction, the particle size of nickel oxide is 8 - 15 nm; Preparation method of Ni-based catalyst: First, prepare metal nickel nanoparticles, and then directly immerse the carrier γ-Al 2 O 3 in the dispersion liquid containing metal nickel nanoparticles. After impregnation, dry it, calcine it in air at 400 - 600 °C (preferably 500 - 550 °C) for 2 - 12 h, and then reduce it in a hydrogen-containing atmosphere at 400 - 700 °C (preferably 500 - 550 °C) for 0.25 - 2 h to obtain the Ni / Al 2 O 3 catalyst, that is, obtain the Ni / Al 2 O 3 catalyst with nickel uniformly dispersed in the form of nanoparticles on the Al 2 O 3 nanorods before the initiation of the reaction.

2. The application according to claim 1, Characterized in that: The drying temperature is 30 - 150 °C, and the drying time is 2 - 24 h.

3. The application according to claim 1, Characterized in that: The carrier needs to be heat-treated before being immersed in the dispersion containing nickel metal nanoparticles. The specific process is as follows: The carrier γ-phase Al 2 O 3 is calcined in air at 600 - 900 °C for 1 - 5 h.

4. The application according to claim 1, Characterized in that: The preparation process of metal nickel nanoparticles is as follows: Dilute 100 - 150 μL of 0.2 - 1.0 mol / L nickel nitrate aqueous solution with water to 3 - 7 mL, add it to the mixed solution composed of cetyltrimethylammonium bromide, n-butanol, and cyclohexane, heat the mixed solution to 60 - 80 °C, and keep it warm for 0.5 - 2 h under stirring; Dissolve 20 - 50 mg of sodium borohydride in 0.2 - 1 mL of water, and add it to the above solution to obtain a metal nickel nanoparticle dispersion; wherein the dosage of cetyltrimethylammonium bromide is 2 - 10 g, the dosage of n-butanol is 10 - 20 mL, and the dosage of cyclohexane is 60 - 100 mL.

5. The application according to claim 1 or 3 or 4, Characterized in that: Impregnation for preparing Ni / Al 2 O 3 The catalyst process is as follows: Immerse 0.3 - 1 g of the carrier γ-phase Al 2 O 3 in the metal nickel nanoparticle dispersion, stir for 0.5 - 10 min, add 30 - 80 mL of ethanol and then centrifuge. After washing with ethanol, disperse the solid in 5 - 20 mL of ethanol and let it stand in air at room temperature for 6 - 24 h, and then dry at 30 - 120 °C for 2 - 24 h; after thoroughly grinding the dried solid for 10 - 30 min, calcine it in air at 400 - 600 °C for 2 - 12 h, and then carry out reduction treatment in a hydrogen-containing atmosphere, where the volume percentage of hydrogen is 20 - 100%, and the rest is one or more of the inert gases He, Ar or N 2 One or more of them, the reduction temperature is 400 - 700 °C, and the reduction time is 15 - 120 min, thus obtaining the catalyst required for the reaction.

6. The application according to claim 1, Characterized in that: The application of the nickel-based catalyst for partial oxidation of methane in the partial oxidation of methane to produce carbon monoxide and hydrogen, with the reaction gas ratio: the volume percentage of methane is 0.4 - 6% (preferably 3 - 5.6%), the volume percentage of oxygen is 0.2 - 3% (preferably 1.5 - 2.8%), and the rest is an inert gas such as He, Ar or N 2 or one or more of them.

7. The application according to claim 6, Characterized in that: The reaction gas may further contain carbon monoxide with a volume percentage of 0 - 6% (preferably 0.4 - 3%), hydrogen with a volume percentage of 0 - 12% (preferably 0.8 - 6%), water with a volume percentage of 0 - 6% (preferably 0.2 - 1%), and carbon dioxide with a volume percentage of 0 - 3% (preferably 0.2 - 1%).

8. The application according to any one of claims 1 - 7, Characterized in that: The reaction conditions are as follows: the reaction temperature is 550 - 800 °C (preferably 600 - 670 °C), the mass space velocity of the reaction gas is 30000 - 300000 mL g 催化剂 -1 h -1 preferably (30000 - 150000 mL g 催化剂 -1 h -1 ), and the total pressure of the reaction gas is 0.1 - 0.2 MPa (preferably 0.1 - 0.15 MPa).

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