Catalyst for low-temperature catalytic combustion and elimination of light alkanes, preparation method and application thereof

Abstract

The present invention relates to a catalyst for low-temperature catalytic combustion and elimination of light alkanes, and a preparation method and application thereof. The catalyst is 2.25wt% M 2 / 5M 1 O x ‑CoO x , where M 1 It is a rare earth metal, and its content is 5% of the molar content of cobalt. 2 The precious metal has a single substance content of 2.25wt% of the mass of the cobalt-based composite oxide doped with rare earth metals. 2 / 5M 1 O x ‑CoO x The catalyst was first calcined at 450°C and then aged at 750°C. x ‑CoO x and 2.25wt%Pt / 5LaO x ‑CoO x Alkane T after aging of two catalysts 90 The temperature of the catalyst does not increase but slightly decreases compared to the fresh catalyst. Compared with the prior art, the catalyst prepared by the present invention has high activity and high thermal stability, and has great application potential in waste gas treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst design and preparation and the technical field of volatile organic compound treatment, and in particular to a preparation method and application of a high thermal stability catalyst for low-temperature catalytic combustion of light alkanes. Background Art

[0002] The World Health Organization generally defines volatile organic compounds (VOCs) as compounds with a boiling point below 260°C and above 50°C at atmospheric pressure as major air pollutants. These compounds usually come from indoor and outdoor sources. Outdoor emissions are mainly composed of various industries such as coal chemical industry, organic chemical industry, petrochemical industry, paint, solvent, dyeing, etc. Most indoor organic matter comes from organic solvents in interior decoration materials, adhesives, cosmetics, detergents, household products, etc. Volatile organic compounds are toxic, carcinogenic, mutagenic and teratogenic, and are extremely harmful to human health. In addition, volatile organic compounds also greatly promote the formation of ozone, photochemical smog and secondary aerosols, which are destructive to the environment. Therefore, limiting VOCs emissions has become an important task to protect human health and the environment.

[0003] There are two main technologies for removing VOCs: recycling and degradation. Recycling technologies include absorption, condensation, adsorption, and membrane separation, while degradation technologies include catalytic combustion, photocatalysis, biodegradation, thermal incineration, and plasma destruction. Among the many methods, recycling technology is not suitable for the purification of low-concentration VOCs, and incineration technology requires high temperatures of 700-800°C, which will produce secondary pollution. Neither of them is an ideal removal technology. Catalytic combustion can achieve complete conversion of VOCs below 500°C without causing secondary pollution. Therefore, catalytic combustion technology is currently one of the most effective methods for treating VOCs.

[0004] There are two main types of catalysts used for catalytic combustion of VOCs, namely precious metal catalysts and transition metal catalysts. Precious metal catalysts have good activity and have been widely used, such as three-way catalysts in automobile exhaust treatment, but precious metal catalysts are expensive and easily sintered and poisoned, resulting in loss of activity. Although transition metal catalysts are not as active as precious metals, their long life and low cost make them very promising catalysts. Therefore, the current problem is the need to modify transition metal catalysts and develop catalysts with high activity, high stability, high selectivity and low cost.

[0005] Patent application CN202110317156.2 discloses a catalyst for low-temperature catalytic combustion of propane with high thermal stability, its preparation method and application. The catalyst provided by the present invention is Co with a loading of 30%. 3 O 4 / SmMn 2 O 5 The high temperature thermal stability of the catalyst is 400℃-1000℃, that is, the catalyst can circulate at 400℃-1000℃ for 24 hours without deformation. The catalyst can be used for low-temperature catalytic combustion of propane, and the temperature at which propane reaches 90% conversion rate is only 200℃-230℃, with good stability and good activity. However, the patent tests the stability of the catalyst at 400-1000℃, and the catalyst is only calcined once, focusing on the life of the catalyst when reacting under high temperature conditions. After the second calcination, the physical and chemical properties of the catalyst will change greatly, thus affecting the activity. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a catalyst for low-temperature catalytic combustion and elimination of light alkanes with high thermal stability and its preparation method and application. The catalyst of the present invention can still maintain good activity after being calcined at 450°C and then calcined at 750°C, and has good high temperature resistance.

[0007] The purpose of the present invention can be achieved by the following technical scheme: a catalyst for the low-temperature catalytic combustion and elimination of light alkanes, which is mainly a cobalt-based catalyst, modified by doping and loading, and used as a high thermal stability catalyst for the catalytic combustion of light alkanes. The catalyst not only shows high activity in the catalytic combustion of light alkanes, but also has good active thermal stability. The high thermal stability of the catalyst is an important performance for removing VOCs in a complex environment.

[0008] Specifically, the catalyst is 2.25wt% M 2 / 5M 1 O x -CoO x , where M 1 It is a rare earth metal, and its content is 5% of the molar content of cobalt. 2 It is a noble metal, and its single substance content is 2.25wt% of the mass of the cobalt-based composite oxide doped with the rare earth metal. x is 1-4.

[0009] Furthermore, the M 1 is La, Ce, Ga or Nd; the M 2 It is Ru, Pd, Ag or Pt.

[0010] Furthermore, the catalyst is 2.25wt%Ru / 5LaO x -CoO x or 2.25wt%Pt / 5LaO x -CoO x2.25wt%Ru / 5LaO x -CoO x or 2.25wt%Pt / 5LaO x -CoO x After catalyst aging at 750℃, propane T 90 It is about 10℃ higher than the catalyst calcined at 450℃.

[0011] The present invention also provides a method for preparing the catalyst for low-temperature catalytic combustion and elimination of light alkanes, comprising the following steps:

[0012] S1, Co and M 1 The rare earth metal-doped cobalt-based composite oxide 5M was prepared by a one-pot solvothermal method using soluble salts of 1 O x -CoO x ;

[0013] S2, M 2 The soluble salt of isocyanate is used as a precursor, and the composite oxide prepared in step S1 is used as a carrier. The catalyst 2.25wt% M is prepared by an equal volume impregnation method. 2 / 5M 1 O x -CoO x .

[0014] Furthermore, the soluble salt of Co includes cobalt acetate, and M 1 Soluble salts thereof include lanthanum acetate, cerium acetate, gadolinium acetate or neodymium acetate;

[0015] The M 2 Soluble salts thereof include ruthenium nitrate, palladium nitrate, platinum nitrate or silver nitrate.

[0016] Furthermore, the temperature of the solvothermal method in step S1 is 150-200° C., and the reaction time is 12-36 hours.

[0017] Further, the product prepared by the solvothermal method in step S1 is washed with alcohol, filtered, dried, and calcined to obtain a metal-doped cobalt-based composite oxide 5M 1 O x -CoO x .

[0018] Furthermore, the impregnated product of step S2 is left to stand at room temperature for 3-5 hours, then transferred to a 50-70°C oven for drying for 10-14 hours, and finally calcined at 400-500°C for 3-5 hours to obtain the final catalyst, and the catalyst is then aged at 700-800°C for 3-5 hours.

[0019] The present invention also provides application of the catalyst for low-temperature catalytic combustion and elimination of light alkanes, wherein the catalyst is used for catalytic combustion of light alkanes.

[0020] Further, light alkanes are a mixture of methane, ethane, and propane;

[0021] Reaction space velocity is 15000mlg -1 h -1 , the reaction temperature is 50℃-550℃.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The catalyst provided by the present invention has good high temperature resistance in terms of activity, mainly because the unique structure of the catalyst has high temperature resistance and more active species are generated at high temperature. After high temperature treatment, the activity becomes even better, and it has great potential for removing VOCs in complex industrial environments.

[0024] 2. The catalyst provided by the present invention can completely convert propane into water and carbon dioxide at a relatively low temperature, and the catalyst has good activity.

[0025] 3. The catalyst provided by the present invention is mainly composed of a transition metal cobalt-based catalyst and loaded with a trace amount of a precious metal catalyst. Therefore, the cost of preparing the catalyst is low, and the preparation process is simple, without complicated equipment, and has low risk. DETAILED DESCRIPTION

[0026] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0027] The catalyst developed by the present invention is used for the catalytic combustion of light alkanes. Since the CH bond energy of methane, ethane and propane is relatively large and difficult to be activated, the following examples use methane, ethane and propane as the model gases for the reaction. 2 / 5M 1 O x -CoO x , of which 2.25wt%Ru / 5LaO x -CoO x and 2.25wt%Pt / 5LaO x -CoO xThe catalytic activity of the two catalysts was not reduced but improved after high-temperature treatment, including the following preparation process: cobalt acetate and lanthanum acetate, cerium acetate, gadolinium acetate, and neodymium acetate were used as precursors, and rare earth metal-doped cobalt-based composite oxides were prepared by a one-pot solvent thermal method; then ruthenium nitrate, palladium nitrate, platinum nitrate, and silver nitrate were used as precursors, and rare earth metal-doped cobalt-based composite oxides were used as carriers, and the catalyst of the present invention was prepared by an equal volume impregnation method. The specific preparation process is as follows:

[0028] Preparation of cobalt-based composite oxides doped with rare earth metal elements:

[0029] 1. Soluble rare earth metal salts such as cobalt acetate, lanthanum acetate, gadolinium acetate, neodymium acetate, or cerium acetate are used as precursors, mixed and stirred in a reactor filled with methanol, and after mixing, the reactor is transferred to an oven at 150-200°C for reaction for 12-36 hours.

[0030] 2. Rinse and filter the precursors obtained in step 1 with anhydrous ethanol, and then dry them in an oven. Collect the completely dried precursors in a crucible, and then place them in a muffle furnace for calcination to obtain 5M 1 O x -CoO x Cobalt-based composite oxides.

[0031] Loading modification of cobalt-based composite oxides:

[0032] 3. Weigh a certain amount of cobalt-based composite oxide in step 2 as a carrier, and use soluble precious metal salts such as ruthenium nitrate, palladium nitrate, platinum nitrate or silver nitrate as precursors for equal volume impregnation. The specific impregnation process is: weigh a certain amount of ruthenium nitrate, palladium nitrate, platinum nitrate or silver nitrate solution, which contains 2.25wt% of elemental ruthenium, palladium, silver and platinum in the carrier mass, and then use a pipette to take a certain amount of deionized water to dilute ruthenium nitrate. The total solution content is determined according to the water absorption rate of the carrier, and then pour the diluted ruthenium nitrate, palladium nitrate, platinum nitrate or silver nitrate solution into the carrier, stir evenly, and after complete absorption, let it stand at room temperature for 3-5h, and then transfer it to a 50-70℃ oven to dry for 10-14h.

[0033] 4. The catalyst in step 3 was placed in a crucible and then calcined in a muffle furnace at 400-500°C for 3-5h at a heating rate of 5°C / min to obtain a fresh 2.25wt% M 2 / 5M 1 O x -CoO x Composite oxides.

[0034] 5. Take 500 mg of the fresh catalyst prepared in step 4 and calcine it again in a muffle furnace at a temperature of 750°C and a heating rate of 2°C / min to obtain an aged 2.25 wt% M 2 / 5M 1 O x -CoO x Composite oxides.

[0035] Example 1

[0036] 3.54g of cobalt acetate and 0.276g of lanthanum acetate were stirred evenly in 75ml of methanol solution, and then the reactor was transferred to a 180℃ oven for reaction for 24h. After the reaction, the product was filtered, washed and dried. Then it was calcined in a muffle furnace at 450℃ for 4h with a heating rate of 5℃ / min to obtain 5LaO x -CoO x Composite oxides.

[0037] Take 1g5LaO x -CoO x As a carrier, ruthenium nitrate was used as a precursor, and the carrier mass fraction of 2.25%wt of elemental Ru was loaded by equal volume impregnation method, left to stand for 4 hours, and dried in a 60℃ oven for 12 hours. Then it was calcined at 450℃ in a muffle furnace for 4 hours with a heating rate of 5℃ / min, and finally a fresh 2.25wt%Ru / 5LaO x -CoO x Catalyst. Prepare fresh 2.25wt%Ru / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Ru / 5LaO x -CoO x catalyst.

[0038] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 200℃, the propane conversion rate reaches 90%, about 270℃, the ethane conversion rate reaches 90%, about 500℃, the methane conversion rate can reach 90%.

[0039] Example 2

[0040] 3.54g of cobalt acetate and 0.250g of gadolinium acetate were stirred evenly in 75ml of methanol solution, and then the reactor was transferred to a 180℃ oven for reaction for 24h. After the reaction, the product was filtered, washed and dried. Then it was calcined in a muffle furnace at 450℃ for 4h with a heating rate of 5℃ / min. After calcination, 5GaO x -CoO x Composite oxides.

[0041] Take 1g5GaO x -CoO x As a carrier, the single substance Ru with a carrier mass fraction of 2.25%wt was loaded by the equal volume impregnation method, left to stand for 4 hours, and dried in a 60℃ oven for 12 hours. Then it was calcined in a muffle furnace at 450℃ for 4 hours with a heating rate of 5℃ / min, and finally a fresh 2.25wt%Ru / 5GaO x -CoO x Catalyst. Prepare fresh 2.25wt%Ru / 5GaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Ru / 5GaO x -CoO x catalyst.

[0042] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 180℃, the propane conversion rate reaches 90%, about 250℃, the ethane conversion rate reaches 90%, and about 430℃, the methane conversion rate can reach 90%.

[0043] Example 3

[0044] 3.54g of cobalt acetate and 0.198g of neodymium acetate were stirred evenly in 75ml of methanol solution, and then the reactor was transferred to a 180℃ oven for reaction for 24h. After the reaction, the product was filtered, washed and dried. Then it was calcined in a muffle furnace at 450℃ for 4h with a heating rate of 5℃ / min. After calcination, 5NdO x -CoO x Composite oxides.

[0045] Take 1g5NdO x -CoO xAs a carrier, the single substance Ru with a carrier mass fraction of 2.25%wt was loaded by the equal volume impregnation method, left to stand for 4 hours, and dried in an oven at 60°C for 12 hours. Then it was calcined in a muffle furnace at 450°C for 4 hours with a heating rate of 5°C / min to finally obtain fresh 2.25wt%Ru / 5NdO x -CoO x Catalyst. Prepare fresh 2.25wt%Ru / 5NdO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Ru / 5NdO x -CoO x catalyst.

[0046] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 175℃, the propane conversion rate reaches 90%, about 230℃, the ethane conversion rate reaches 90%, and about 420℃, the methane conversion rate can reach 90%.

[0047] Example 4

[0048] 3.54g of cobalt acetate and 0.225g of cerium acetate were stirred evenly in 75ml of methanol solution, and then the reactor was transferred to a 180℃ oven for reaction for 24h. After the reaction, the product was filtered, washed and dried. Then it was calcined in a muffle furnace at 450℃ for 4h with a heating rate of 5℃ / min. After calcination, 5CeO x -CoO x Composite oxides.

[0049] Take 1g5CeO x -CoO x As a carrier, the single substance Ru with a carrier mass fraction of 2.25%wt was loaded by the equal volume impregnation method, left to stand for 4 hours, and dried in a 60℃ oven for 12 hours. Then it was calcined in a muffle furnace at 450℃ for 4 hours with a heating rate of 5℃ / min, and finally a fresh 2.25wt%Ru / 5CeO x -CoO x Catalyst. Prepare fresh 2.25wt%Ru / 5CeO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Ru / 5CeOx -CoO x catalyst.

[0050] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 210℃, the propane conversion rate reaches 90%, at about 280℃, the ethane conversion rate reaches 90%, at about 480℃, the methane conversion rate can reach 90%.

[0051] Example 5

[0052] 5LaO was prepared by the same method as in Example 1. x -CoO x Composite oxide, weigh 1g of the composite oxide as a carrier, load the single substance Ru with a carrier mass fraction of 0.75wt% by isovolumetric impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ in a muffle furnace for 4h, with a heating rate of 5℃ / min, and finally obtain fresh 0.75wt%Ru / 5LaO x -CoO x Catalyst. 0.75wt%Ru / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 0.75 wt% Ru / 5LaO x -CoO x catalyst.

[0053] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 210℃, the propane conversion rate reaches 90%, at about 280℃, the ethane conversion rate reaches 90%, at about 480℃, the methane conversion rate can reach 90%.

[0054] Example 6

[0055] 5LaO was prepared by the same method as in Example 1. x -CoO xComposite oxide, weigh 1g of the composite oxide as a carrier, load the carrier mass fraction of 1.5wt% of elemental Ru by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ in a muffle furnace for 4h, with a heating rate of 5℃ / min, and finally obtain fresh 1.5wt%Ru / 5LaO x -CoO x Catalyst. 1.5wt%Ru / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 1.5 wt% Ru / 5LaO x -CoO x catalyst.

[0056] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 200℃, the propane conversion rate reaches 90%, about 270℃, the ethane conversion rate reaches 90%, about 500℃, the methane conversion rate can reach 90%.

[0057] Example 7

[0058] 5LaO was prepared by the same method as in Example 1. x -CoO x Composite oxide, weigh 1g of the composite oxide as a carrier, load the carrier mass fraction of 2.25wt% of elemental Ru by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ in a muffle furnace for 4h, with a heating rate of 5℃ / min, and finally obtain fresh 2.25wt%Ru / 5LaO x -CoO x Catalyst. 2.25wt%Ru / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Ru / 5LaO x -CoO x catalyst.

[0059] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g.-1 h -1 , gradually increase the temperature from room temperature to about 200℃, the propane conversion rate reaches 90%, about 270℃, the ethane conversion rate reaches 90%, about 500℃, the methane conversion rate can reach 90%.

[0060] Example 8

[0061] 5LaO was prepared by the same method as in Example 1. x -CoO x Composite oxide, weigh 1g of the composite oxide as a carrier, load the carrier mass fraction of 3wt% of elemental Ru by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ for 4h in a muffle furnace with a heating rate of 5℃ / min, and finally obtain fresh 3wt%Ru / 5LaO x -CoO x Catalyst. 3wt%Ru / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 3 wt% Ru / 5 LaO x -CoO x catalyst.

[0062] The catalyst of this embodiment is: 200mg catalyst (40-60 mesh), 2500ppm alkane (a mixture of methane, ethane and propane with a concentration ratio of 1:1:1), air as carrier gas, and the reaction space velocity is 15000mlg -1 h -1 , gradually increase the temperature from room temperature to about 210℃, the propane conversion rate reaches 90%, at about 280℃, the ethane conversion rate reaches 90%, at about 490℃, the methane conversion rate can reach 90%.

[0063] Example 9

[0064] 5LaO was prepared by the same method as in Example 1. x -CoO x Composite oxide, weigh 1g of the composite oxide as a carrier, load the carrier mass fraction of 3.75wt% of elemental Ru by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ in a muffle furnace for 4h, with a heating rate of 5℃ / min, and finally obtain fresh 3.75wt%Ru / 5LaO x -CoO x Catalyst. 3.75wt%Ru / 5LaO x -CoO x500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 3.75 wt% Ru / 5LaO x -CoO x catalyst.

[0065] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 200℃, the propane conversion rate reaches 90%, about 260℃, the ethane conversion rate reaches 90%, and about 460℃, the methane conversion rate can reach 90%.

[0066] Example 10

[0067] 5LaO was prepared by the same method as in Example 1. x -CoO x Composite oxide, weigh 1g of the composite oxide as a carrier, load the carrier mass fraction of 5wt% of elemental Ru by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ for 4h in a muffle furnace with a heating rate of 5℃ / min, and finally obtain fresh 5wt%Ru / 5LaO x -CoO x Catalyst. 5wt%Ru / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 5 wt% Ru / 5 LaO x -CoO x catalyst.

[0068] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 180℃, the propane conversion rate reaches 90%, at about 250℃, the ethane conversion rate reaches 90%, at about 450℃, the methane conversion rate can reach 90%.

[0069] Embodiment 11

[0070] 5LaO was prepared by the same method as in Example 1. x -CoO xComposite oxide, weigh 1g of the composite oxide as a carrier, load the single substance Pt with a carrier mass fraction of 2.25w% by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ in a muffle furnace for 4h, with a heating rate of 5℃ / min, and finally obtain fresh 2.25wt% Pt / 5LaO x -CoO x Catalyst. Prepare fresh 2.25wt% Pt / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Pt / 5LaO was obtained. x -CoO x catalyst.

[0071] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 220℃, the propane conversion rate reaches 90%, about 290℃, the ethane conversion rate reaches 90%, and about 420℃, the methane conversion rate can reach 90%.

[0072] Example 12

[0073] 5LaO was prepared by the same method as in Example 1. x -CoO x Composite oxide, weigh 1g of the composite oxide as a carrier, load the single substance Pd with a carrier mass fraction of 2.25w% by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ in a muffle furnace for 4h, with a heating rate of 5℃ / min, and finally obtain fresh 2.25wt% Pd / 5LaO x -CoO x Catalyst. Prepare fresh 2.25wt% Pd / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Pd / 5LaO was obtained. x -CoO x catalyst.

[0074] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 210℃, the propane conversion rate reaches 90%, about 270℃, the ethane conversion rate reaches 90%, and about 380℃, the methane conversion rate can reach 90%.

[0075] Embodiment 13

[0076] 5LaO was prepared by the same method as in Example 1. x -CoO x Composite oxide, weigh 1g of the composite oxide as a carrier, load the carrier mass fraction of 2.25w% of single substance Ag by equal volume impregnation method, let it stand for 4h, and dry it in a 60℃ oven for 12h. Then calcine it at 450℃ in a muffle furnace for 4h, with a heating rate of 5℃ / min, and finally obtain fresh 2.25wt% Ag / 5LaO x -CoO x Catalyst. Prepare fresh 2.25wt% Ag / 5LaO x -CoO x 500 mg of the catalyst was calcined in a muffle furnace at 750 °C for 4 h at a heating rate of 2 °C / min. After calcination, aged 2.25 wt% Ag / 5LaO x -CoO x catalyst.

[0077] The catalyst of this example is: 200 mg catalyst (40-60 mesh), 2500 ppm alkane (a mixture of methane, ethane, and propane in a concentration ratio of 1:1:1), air as the carrier gas, and the reaction space velocity is 15000 ml / g. -1 h -1 , gradually increase the temperature from room temperature to about 200℃, the propane conversion rate reaches 90%, at about 250℃, the ethane conversion rate reaches 90%, at about 390℃, the methane conversion rate can reach 90%.

[0078] Table 1 shows the fresh (450°C) and aged (750°C) 2.25wt%Ru / 5M 1 O x -CoO x ΔT of the catalytic combustion of methane, ethane and propane 90 (750℃-450℃), and investigated the effect of different rare earth metals on the thermal stability of catalyst activity. Finally, lanthanum was selected as the final rare earth metal.

[0079] <![CDATA[ΔT 90 (750℃-450℃)]]> Example 1 Example 2 Example 3 Example 4 Methane -40 28 39 25 Ethane -13 42 32 40 Propane -14 21 30 33

[0080] From the data in Table 1, we can see that:

[0081] 1. The data in the table represent the T values ​​of the catalysts in Examples 1-4 for catalytic combustion of methane, ethane and propane in two states: aged (calcined at 450°C and then calcined again at 750°C) and fresh (calcined only once at 450°C). 90 The only difference between the four catalysts in Examples 1-4 is that the rare earth metals doped in the cobalt-based oxide are different, and the rare earth metals doped in Examples 1-4 are: La, Ga, Nd, Ce.

[0082] 2. ΔT of catalytic combustion of methane, ethane and propane from Examples 1-4 90 (750℃-450℃) value, the value in Example 1 is negative, and the catalyst in Example 1 is 2.25wt%Ru / 5LaO x -CoO x , which indicates that 2.25wt%Ru / 5LaO x -CoO x The catalyst has good thermal stability of activity. After aging at 750°C, the catalyst activity did not lose or deactivate, but became better, and the activity recovered. In Examples 2-4, after aging at 750°C, the catalyst deactivated to varying degrees.

[0083] 3. In Examples 1-4, 2.25wt%Ru / 5LaO may be preferred x -CoO x It is the most active and thermally stable catalyst.

[0084] Table 2 shows the X-wt%Ru / 5LaO containing different masses of elemental ruthenium. x -CoO x ΔT of the catalyst before and after aging for the catalytic combustion of methane, ethane, and propane 90 (750℃-450℃), and finally 2.25wt% of ruthenium is preferred as the optimal content.

[0085]

[0086]

[0087] From the data in Table 2, we can see that:

[0088] 1. The data in the table represent the T values ​​of the catalysts in Examples 5-10 for catalytic combustion of methane, ethane and propane in two states: aged (calcined at 450°C and then calcined again at 750°C) and fresh (calcined only once at 450°C). 90The only difference between the six catalysts in Examples 5-10 is that 5LaO x -CoO x The contents of the loaded precious metal Ru are different, and their contents are respectively: 0.75, 1.5, 2.25, 3, 3.75, and 5 of the carrier mass fraction.

[0089] 2. ΔT of catalytic combustion of methane, ethane and propane from Examples 5-10 90 (750℃-450℃) value, the value in Example 7 is negative, and the catalyst in Example 7 is 2.25wt%Ru / 5LaO x -CoO x , which indicates that 2.25wt%Ru / 5LaO x -CoO x The catalyst has the best active thermal stability. After aging at 750°C, the catalyst activity becomes better and the strongest activity recovery ability appears. The catalysts loaded with different masses of Ru in other examples have different degrees of deactivation or recovery of activity after aging, but none of them exceeds the high temperature resistance of the catalyst in Example 7.

[0090] 3. In Examples 5-10, 2.25wt%Ru / 5LaO with a Ru mass fraction of 2.25% can be preferred. x -CoO x The catalyst is the most active and thermally stable catalyst.

[0091] Table 3 shows the 2.25wt% M in fresh (450℃) and aged (750℃) samples in different examples. 2 / 5LaO x -CoO x ΔT of the catalytic combustion of methane, ethane and propane 90 (750℃-450℃). 2 Including three precious metals: Pt, Pd and Ag.

[0092]

[0093]

[0094] From the data in Table 3, we can see that:

[0095] 1. The data in the table represent the T values ​​of the catalysts in Examples 11-13 for catalytic combustion of methane, ethane and propane in two states: aged (calcined at 450°C and then calcined again at 750°C) and fresh (calcined only once at 450°C). 90 The only difference between the three catalysts in Examples 11-13 is that 5LaO x-CoO x Different precious metals are loaded, in order: Pt, Pd, and Ag.

[0096] 2. ΔT of catalytic combustion of methane, ethane and propane from Examples 11-13 90 (750℃-450℃) value, the value in Example 11 is negative, and the catalyst of Example 11 is 2.25wt%Pt / 5LaO x -CoO x , which indicates that 2.25wt%Pt / 5LaO x -CoO x The catalyst also has active thermal stability. After aging at 750°C, the catalyst activity becomes better. The catalysts represented by Examples 12 and 13 are 2.25wt% Pd / 5LaO x -CoO x and 2.25wt%Ag / 5LaO x -CoO x All of them showed different degrees of deactivation, among which 2.25wt%Pd / 5LaO x -CoO x The degree of catalyst deactivation is not large, indicating that it also has a certain degree of thermal stability.

[0097] The preferred embodiments of the present invention are described above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0098] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0099] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A catalyst for low-temperature catalytic combustion and elimination of light alkanes, characterized in that: The catalyst is 2.25wt%Ru / 5LaO x -CoO x or 2.25wt%Pt / 5LaO x -CoO x , wherein the La content is 5% of the molar content of the cobalt element, the Ru and Pt are 2.25wt% of the mass of the cobalt-based composite oxide doped with rare earth metals, and x is 1-4; the catalytic activity of the two catalysts is not reduced but improved after high-temperature treatment; The catalyst is prepared by the following method: S1. Using soluble salts of Co and La as precursors, a one-pot solvothermal method was used to prepare rare earth metal-doped cobalt-based composite oxide 5LaO x -CoO x ; S2, using Ru or Pt soluble salt as precursor, and the composite oxide obtained in step S1 as carrier, adopting equal volume impregnation method, the impregnated product is placed at room temperature for 3-5 hours, transferred to 50-70 ℃ oven for drying for 10-14 hours, and finally calcined at 400-500 ℃ for 3-5 hours to obtain the final catalyst, and the catalyst is aged at 700-800 ℃ for 3-5 hours to obtain the catalyst 2.25wt%Ru / 5LaO x -CoO x or 2.25wt%Pt / 5LaO x -CoO x .

2. A method for preparing a catalyst for low-temperature catalytic combustion and elimination of light alkanes as claimed in claim 1, characterized in that: The following steps are involved: S1. Using soluble salts of Co and La as precursors, a one-pot solvothermal method was used to prepare rare earth metal-doped cobalt-based composite oxide 5LaO x -CoO x ; S2, using Ru or Pt soluble salt as precursor and the composite oxide prepared in step S1 as carrier, the catalyst 2.25wt%Ru / 5LaO was prepared by equal volume impregnation method. x -CoO x or 2.25wt%Pt / 5LaO x -CoO x .

3. The method for preparing a catalyst for low-temperature catalytic combustion and elimination of light alkanes according to claim 2, characterized in that: The soluble salt of Co includes cobalt acetate, and the soluble salt of La includes lanthanum acetate; The soluble salt of Ru or Pt includes ruthenium nitrate or platinum nitrate.

4. The method for preparing a catalyst for low-temperature catalytic combustion and elimination of light alkanes according to claim 2, characterized in that: The temperature of the solvothermal method in step S1 is 150-200° C., and the reaction time is 12-36 hours.

5. The method for preparing a catalyst for low-temperature catalytic combustion and elimination of light alkanes according to claim 2, characterized in that: The product prepared by the solvothermal method in step S1 is washed with alcohol, filtered, dried, and calcined to obtain a metal-doped cobalt-based composite oxide 5LaO x -CoO x .

6. The method for preparing a catalyst for low-temperature catalytic combustion and elimination of light alkanes according to claim 2, characterized in that: The impregnated product of step S2 is left to stand at room temperature for 3-5 hours, then transferred to a 50-70°C oven for drying for 10-14 hours, and finally calcined at 400-500°C for 3-5 hours to obtain the final catalyst, and the catalyst is then aged at 700-800°C for 3-5 hours.

7. Use of the catalyst for low-temperature catalytic combustion and elimination of light alkanes as claimed in claim 1, characterized in that: The catalyst is used for catalytic combustion of light alkanes.

8. The use of the catalyst for low-temperature catalytic combustion and elimination of light alkanes according to claim 7, characterized in that: Light alkanes are a mixture of methane, ethane, and propane; The reaction space velocity is 15000mLg -1 h -1 , the reaction temperature is 50℃-550℃.

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