Compound and preparation method and application thereof
Technical Field
The invention relates to a compound and a preparation method and application thereof, in particular to a low-temperature high-activity coal gas layer deoxidation compound catalyst and a preparation method and application thereof.
Background
China is a large coal producing country, coal bed gas with different concentrations can be produced due to coal production every year, and developing effective coal bed gas utilization technology and reducing direct emission of methane are a component part for building an energy-saving and environment-friendly sustainable development mode and building a low-carbon economic system in China. The method has the advantages that the low-grade energy source coal bed gas is practically and reasonably developed by combining energy conservation and emission reduction and improvement of the requirement on the environment, the low-grade energy source coal bed gas is well converted into available resources, the application range and the scale of the coal bed gas are expanded, the utilization efficiency of the coal bed gas is improved, the dual meanings of energy conservation and environmental protection are realized, the national planning on energy policies is met, the control of the international environmental protection organization on the greenhouse effect is met, the strong support of China on the development and the use of the low-grade energy source is better met, and the domestic rapid development of the coal bed gas industry.
The key point of the development and utilization of the coal bed gas is to remove oxygen in the coal bed gas, and the existing coal bed gas deoxidation technology mainly comprises a pressure swing adsorption separation method, a coke combustion method, a catalytic deoxidation method and the like. Chinese patent ZL85103557 discloses a method for separating and enriching methane from coal bed gas by using a pressure swing adsorption method. Generally, the oxygen content of the exhaust gas discharged in the concentration and purification process of methane is also concentrated and improved, and the exhaust gas inevitably contains 5-15% of methane, so that the discharged exhaust gas is in the explosion limit range of methane, and explosion danger exists, so that the application of the technology is limited.
The deoxidation method by using coke combustion (ZL 02113627.0, 200610021720.1) is characterized in that oxygen in methane-rich gas reacts with coke under the high-temperature condition, and part of methane reacts with oxygen to achieve the aim of deoxidation. The advantage is that about 70% of the oxygen reacts with coke and 30% of the oxygen reacts with methane, so that methane losses are smaller. But the disadvantage is that the precious coke resource is consumed, and the coke consumption cost accounts for about 50 percent of the whole operation cost. In addition, the coke deoxidation method has high labor intensity during coke feeding and slag discharging, large environmental dust and difficulty in realizing self-control operation and large-scale production, and the coke contains sulfides in various forms, so that the sulfur content in the gas after oxygen removal is increased.
The essence of the catalytic deoxidation process is rich combustion and oxygen deficiencyCatalytic combustion of methane in atmosphere, under the action of proper catalyst, reacting CH4Oxidative conversion to CO2And H2And O, the oxygen content in the coal bed gas can be reduced to be below 0.5 percent in the process, and the potential safety hazard in the operation process is thoroughly eliminated. Meanwhile, the process is simple and convenient to operate, automatic control and large-scale expansion are facilitated, equipment is simple, and the technology has a good commercial value in the aspect of economy. Catalytic deoxidation can be divided into two main categories, namely noble metal catalysts and non-noble metal catalysts according to active components of the catalysts.
The technology for researching the supported noble metal catalyst at home and abroad is mature. For example, rare earth cerium component with oxygen storage and release functions is added into a catalyst system for the large-scale ligation of Chinese academy of sciences to prepare the novel supported palladium noble metal catalyst, and the oxygen concentration in produced gas is within 0.1 percent and the oxygen conversion rate is higher than 96 percent after the deoxidation treatment of coal bed gas with the methane concentration of 39.15 percent and the oxygen concentration of 12.6 percent. Since the noble metal catalyst is expensive and has limited resources, the range of application is limited. And the non-noble metal oxide catalyst has low cost and easy availability, so the catalyst is greatly concerned. However, the non-noble metal is limited by activity, and the reaction needs to be carried out at a higher temperature, so that the energy consumption is higher.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a compound, a preparation method thereof and application thereof in coal bed methane deoxidation. The composite used for deoxidizing the coal bed gas has the advantages of high activity, low reaction temperature, simple preparation method, low cost and the like.
A composite comprising zinc-supporting alumina, cerous sulfate and a composite metal oxide NdCoO having a perovskite structure3-yY is oxygen vacancy, the weight ratio of the zinc-loaded alumina to the cerous sulfate in the composite is 8:1-2:1, preferably 6:1-3:1, and the zinc-loaded alumina and the composite metal oxide NdCoO with the perovskite structure in the composite3-yIn a weight ratio of 10:1 to 5:1, the zinc content, calculated as oxide, being from 5% to 25% by weight, preferably from 10% to 20% by weight, based on the weight of the alumina supporting zinc.
A process for the preparation of a composite,the method comprises the following steps: aluminum oxide loaded with zinc, cerous sulfate and composite metal oxide NdCoO with perovskite structure3-yKneading and molding, drying and roasting to obtain the composite.
In the above method, the ceric sulfate, the composite metal oxide NdCoO3-y having a perovskite structure, and the zinc-supporting alumina may be commercially available or prepared according to a conventional technique. The conventional preparation technology of the zinc-loaded alumina comprises the steps of loading zinc on alumina, wherein the zinc is selected from one or more of zinc nitrate, zinc sulfate, zinc bromide and zinc chloride; the composite metal oxide NdCoO3-y having a perovskite structure can be produced by a conventional citric acid method or a combustion method. The ceryl sulfate is prepared by adopting the prior art. A specific preparation method of ceryl sulfate, such as the preparation of ceryl sulfate by roasting at 300-500 ℃ for 1-10 h.
In the method, a proper amount of peptizing agent, pore-forming agent, metal auxiliary agent and the like can be added in the kneading process according to the needs.
In the method, the drying time is 1-5h, preferably 2-4h, the drying temperature is 90-150 ℃, preferably 100-; the roasting time is 3-8h, preferably 4-6h, and the temperature is 300-700 ℃, preferably 400-500 ℃.
In the above method, the mixed solution contains at least one of 2, 5-dihydroxy-terephthalic acid and 1,3, 5-benzene tricarboxylic acid, and the mass content of at least one of 2, 5-dihydroxy-terephthalic acid and 1,3, 5-benzene tricarboxylic acid in the mixed solution is 0.5 to 10%, preferably 2 to 7%. The 2, 5-dihydroxy-terephthalic acid or 1,3, 5-benzene tricarboxylic acid added into the mixed solution has stronger coordination effect with zinc ions, can improve the dispersion degree of zinc on alumina, and further improves the activity of the catalyst.
In the above method, the cerous sulfate is preferably treated with a mixed gas of water vapor and nitrogen gas with the water vapor volume content of 0.5% -5%, more preferably 1% -4%, before kneading, the treatment temperature is 100-. The ceryl sulfate treated by water vapor can improve the hydrophilicity of the surface of the ceryl sulfate, is beneficial to the dispersion of the ceryl sulfate, and further improves the activity.
The application of the catalyst in coal gas layer deoxidation is provided.
Research results show that the mechanism of catalytic combustion of the coal bed gas is that methane is firstly dissociated into CH on the surface of the catalytic combustion catalystxSpecies of which x<4, then carrying out oxidation reaction with the adsorbed oxygen or lattice oxygen. This application will catalyze burning catalyst and have the stronger ceric acyl sulfate of methane activation ability to mix, methane can be activated on ceric acyl sulfate molecular sieve, and activated methane species can overflow to catalytic combustion catalyst around and react, burns more easily fast, is showing the activity that has improved the catalyst, and the composite metal oxide NdCoO who has the perovskite structure that contains in this application catalyst in addition has3-yHas rich oxygen vacancy and strong oxygen adsorption capacity, and is beneficial to the enrichment of oxygen for efficient reaction.
Detailed Description
The function and effect of a coal bed methane deoxidation catalyst and a preparation method thereof are further illustrated with reference to the following examples, but the following examples are not to be construed as limiting the invention. In this application,% is volume concentration unless otherwise specified. The ceric acid sulfate referred to in examples and comparative examples was prepared by calcining cerium sulfate at 350 ℃ for 3 hours.
Example 1
The method comprises the steps of mixing commercially available zinc-loaded alumina, commercially available cerous sulfate and a self-made composite metal oxide NdCoO with a perovskite structure3-yKneading and molding, drying and roasting to obtain a compound, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 6h, and the temperature is 400 ℃.
The properties of the complex are as follows: the weight ratio of the zinc-loaded alumina to the molybdenum-loaded HZSM-5 molecular sieve is 7:1, and the zinc-loaded alumina and the composite metal oxide NdCoO with the perovskite structure3-yIn a weight ratio of 7:1, the content of zinc in terms of oxide is 15wt% based on the weight of the zinc-loaded alumina, and the content of molybdenum in terms of oxide is 2wt% based on the weight of the molybdenum-loaded HZSM-5 molecular sieve.
Reaction evaluation catalyst with coal bed gas deoxidation as probeThe catalyst performance, the raw material gas composition is: CH (CH)420 vol%,O23vol%, the balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 0.78%.
Example 2
The method comprises the steps of mixing commercially available zinc-loaded alumina, commercially available cerous sulfate and a self-made composite metal oxide NdCoO with a perovskite structure3-yKneading and molding, drying and roasting to obtain a compound, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 6h, and the temperature is 400 ℃.
The properties of the complex are as follows: the weight ratio of the zinc-loaded alumina to the molybdenum-loaded HZSM-5 molecular sieve is 8:1, and the zinc-loaded alumina and the composite metal oxide NdCoO with the perovskite structure3-yIn a weight ratio of 10:1, the content of zinc in terms of oxide is 10wt% based on the weight of the zinc-loaded alumina, and the content of molybdenum in terms of oxide is 3wt% based on the weight of the molybdenum-loaded HZSM-5 molecular sieve.
The catalyst performance is evaluated by taking coal bed methane deoxidation as a probe reaction, and the feed gas comprises the following components: CH (CH)420 vol%,O23vol%, the balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 0.67%.
Example 3
The method comprises the steps of mixing commercially available zinc-loaded alumina, commercially available cerous sulfate and a self-made composite metal oxide NdCoO with a perovskite structure3-yKneading and molding, drying and roasting to obtain a compound, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 6h, and the temperature is 400 ℃.
The properties of the complex are as follows: the weight ratio of the zinc-loaded alumina to the molybdenum-loaded HZSM-5 molecular sieve is 5:1, and the zinc-loaded alumina and the composite metal oxide NdCoO with the perovskite structure3-yIn a weight ratio of 5:1, based on the weight of the zinc-loaded alumina, zinc is oxygenThe content of the compound is 20wt%, and the content of the molybdenum is 1wt% in terms of oxide based on the weight of the HZSM-5 molecular sieve loaded with the molybdenum.
The catalyst performance is evaluated by taking coal bed methane deoxidation as a probe reaction, and the feed gas comprises the following components: CH (CH)420 vol%,O23vol%, the balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 0.53%.
Example 4
The method comprises the steps of mixing self-made zinc-loaded alumina, commercially available cerous sulfate and self-made composite metal oxide NdCoO with a perovskite structure3-yKneading and molding, drying and roasting to obtain a compound, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 6h, and the temperature is 400 ℃. The preparation process of the zinc-loaded alumina comprises the following steps: preparing a zinc nitrate aqueous solution containing 6 mass% of 2, 5-dihydroxy-terephthalic acid, impregnating the zinc nitrate aqueous solution with alumina, drying the impregnated alumina, and roasting the impregnated alumina, the rest being the same as in example 1.
The catalyst performance is evaluated by taking coal bed methane deoxidation as a probe reaction, and the feed gas comprises the following components: CH (CH)420 vol%,O23vol%, the balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 0.07%.
Example 5
The method comprises the steps of mixing self-made zinc-loaded alumina, commercially available cerous sulfate and self-made composite metal oxide NdCoO with a perovskite structure3-yKneading and molding, drying and roasting to obtain a compound, wherein the drying time is 4 hours, and the drying temperature is 100 ℃; the roasting time is 6h, and the temperature is 400 ℃. The preparation process of the zinc-loaded alumina comprises the following steps: an aqueous solution of zinc nitrate containing 3% by mass of 1,3, 5-benzenetricarboxylic acid was prepared as in example 1.
The catalyst performance is evaluated by taking coal bed methane deoxidation as a probe reaction, and the feed gas comprises the following components: CH (CH)420 vol%,O23vol%The balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 0.03%.
Example 6
The difference from example 1 is that before kneading, the commercially available ceryl sulfate was treated with a steam-nitrogen mixture containing 1% by volume of steam at 180 ℃ for 3 min.
The catalyst performance is evaluated by taking coal bed methane deoxidation as a probe reaction, and the feed gas comprises the following components: CH (CH)420 vol%,O23vol%, the balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 0.43%.
Example 7
Compared with the example 1, the difference is that before the commercial ceryl sulfate is kneaded, the ceryl sulfate is treated by adopting a water vapor nitrogen mixed gas with the water vapor volume content of 4 percent, the treatment temperature is 120 ℃, and the treatment time is 1-151010 min.
The catalyst performance is evaluated by taking coal bed methane deoxidation as a probe reaction, and the feed gas comprises the following components: CH (CH)420 vol%,O23vol%, the balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 0.35%.
Example 8
The same procedure as in example 1 was repeated except that the zinc-loaded alumina prepared in the preparation of the alloy, the ceric sulfate commercially available in the preparation of the alloy, and the composite metal oxide NdCoO3-y prepared in the preparation of the alloy were directly mixed.
The catalyst performance is evaluated by taking coal bed methane deoxidation as a probe reaction, and the feed gas comprises the following components: CH (CH)420 vol%,O23vol%, the balance being N2. The reaction temperature is 425 ℃, and the volume space velocity is 12500 h-1After the reaction is stable, detecting O in tail gas at the outlet of the reactor by on-line chromatography2The concentration was 1.25%.