Catalyst for preparing methanol by low-temperature conversion of low-concentration coal bed gas and method for preparing methanol
阅读说明：本技术 低浓度煤层气低温转化制甲醇的催化剂及制备甲醇的方法 (Catalyst for preparing methanol by low-temperature conversion of low-concentration coal bed gas and method for preparing methanol ) 是由 丁传敏 王俊文 杨美如 王涛 贾永杰 于 2021-09-27 设计创作，主要内容包括：本发明涉及一种低浓度煤层气低温转化制甲醇的方法,属于天然气化工和煤化工技术领域。主要解决低浓度煤层气需要在高温条件下转化的问题。本发明的方法中,所述工艺为使用催化剂,以离子液体为溶剂,置适量的H-(2)O-(2)在反应釜中,然后充低浓度煤层气至3-5MPa,在500-1200rpm、50-100℃下反应30-300min,反应后将反应釜冷却,防止产物挥发,随后通过离心分离出催化剂,通过蒸馏分离出产物。该工艺使得低浓度煤层气在低温条件下转化为甲醇,且离子液体高沸点有利于实现反应后产物的分离。(The invention relates to a method for preparing methanol by low-temperature conversion of low-concentration coal bed gas, belonging to the technical field of natural gas chemical industry and coal chemical industry. Mainly solves the problem that low-concentration coal bed gas needs to be converted under high temperature. In the method, the process uses a catalyst, takes ionic liquid as a solvent, and puts a proper amount of H 2 O 2 Filling low-concentration coal bed gas to 3-5MPa in a reaction kettle, reacting for 30-300min at 500-1200rpm and 50-100 ℃, cooling the reaction kettle after reaction to prevent the volatilization of the product, then centrifugally separating out the catalyst, and separating out the product by distillation. The process enables low-concentration coal bed gas to be converted into methanol at low temperature, and the high boiling point of the ionic liquid is beneficial to separation of products after reaction.)
1. The catalyst for preparing the methanol by low-temperature conversion of the low-concentration coal bed gas is characterized in that the catalyst is MN, wherein M is any one or more than two of Au, Rh, Pd and Pt, and N is nitrogen.
2. The catalyst for preparing the methanol by the low-temperature conversion of the low-concentration coal-bed gas as claimed in claim 1, which is prepared by the following steps:
(1) weighing a proper amount of prepared noble metal salt solution, and dissolving the noble metal salt solution in a proper amount of deionized water to ensure that the metal concentration is 0.16-5 mmol.L-1；
(2) Weighing a certain amount of nitrogen source, adding the nitrogen source into the solution to enable the molar ratio of the metal to the nitrogen source to be 1:2, and stirring until the metal and the nitrogen source are completely dissolved;
(3) adding newly prepared 0.1-5M NaBH4Dissolving in the solution to produce a dark brown colloid;
(4) and (4) freeze-drying the colloid obtained in the step (3), and roasting for 3-5h at the temperature of 800-1000 ℃ in an inert atmosphere to obtain the catalyst.
3. The catalyst for preparing methanol by low-temperature conversion of low-concentration coal-bed gas according to claim 2, wherein the noble metal salt is one or more of ammonium chloroplatinate, rhodium chloride, palladium nitrate and chloroauric acid.
4. The catalyst for preparing the methanol by the low-temperature conversion of the low-concentration coal-bed gas as claimed in claim 2, wherein the used nitrogen source is one or more of melamine, urea, potassium nitrate and ammonium phosphate.
5. The method for preparing the methanol by low-temperature conversion of the low-concentration coal bed gas is characterized in that the methanol is prepared in H2O2The conversion is carried out in the ionic liquid by using the catalyst for preparing the methanol by the low-temperature conversion of the coal bed gas with the low concentration in the claim 1 under the existing condition.
6. The method for preparing methanol by low-temperature conversion of low-concentration coal bed gas as claimed in claim 5, which comprises the following steps:
(1) weighing 20-300 mg of catalyst, and measuring 5-100 mL of ionic liquid and 5-100 mLH2O2Putting the mixture into a reaction kettle;
(2) filling low-concentration coal bed gas to 3-5MPa, reacting at 500-1200rpm and 50-100 ℃ for 30-300min, centrifugally separating the reacted liquid phase to obtain the catalyst, and distilling to separate the liquid phase product.
7. The method for preparing methanol by low-temperature conversion of low-concentration coal-bed gas according to claim 5 or 6, wherein the ionic liquid is one or more of 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-allyl-3-methylimidazolium chloride.
Technical Field
The invention relates to a catalyst for preparing methanol by low-temperature conversion of low-concentration coal bed gas and a method for preparing methanol by using the catalyst, and belongs to the technical field of natural gas chemical industry and coal chemical industry.
Background
The coal bed gas takes methane as a main component and is associated with coal and symbiotic gas resources. The energy in China has the characteristics of rich coal, less oil and gas, and the coal resources are rich, so the coal bed gas resources are also very rich, the reserves are third in the world, but the utilization rate is very low. According to different extraction modes, the coal bed gas can be divided into ground drilling extraction coal bed gas, underground extraction coal bed gas and ventilation gas. The coal bed gas with different methane concentrations can be divided into high-concentration coal bed gas, medium-high concentration coal bed gas and low-concentration coal bed gas. The coal bed gas with the methane concentration of 90-95% in the ground well drilling extracted coal bed gas is high-concentration coal bed gas, and the coal bed gas can be used as energy to be merged into a natural gas pipe network or used as a chemical raw material after being simply processed. When coal bed gas is extracted underground, air is mixed into the part of the coal bed gas, the methane concentration of the coal bed gas is between 3% and 80%, the coal bed gas with the methane concentration of 30% to 80% is generally called medium-high concentration coal bed gas according to the concentration, and the part of the coal bed gas is relatively simple and mature in utilization technology and is mainly used for civil fuel, power generation and the like. The coal bed gas with the methane concentration less than 30% is called low-concentration coal bed gas, and because the concentration of the coal bed gas crosses the explosion limit of the methane, the explosion risk exists in the transportation and purification concentration processes, so the coal bed gas with the methane concentration less than 30% is difficult to utilize, and the part of the coal bed gas is usually directly emptied, and the low-concentration coal bed gas accounts for about 65% of the coal bed gas, which causes resource waste and increases the greenhouse effect. The utilization of the part of the coal bed gas is mainly to utilize methane.
The conversion of methane has two modes of indirect conversion and direct conversion. Aiming at the low-concentration coal bed gas with the methane content of below 30 percent due to the CH4/O2Close to 2:1 for indirect conversion, which can convert methane first to synthesis gas and then to methanol and higher hydrocarbons via synthesis gas, however, the process needs to be carried out at high temperatures, high energy consumption and capital investment limit the wide application of this process; the direct conversion is to directly convert methane into chemical products such as methanol, formaldehyde, formic acid and the like, and convert the methane into liquid products without the process of converting the methane into synthesis gas, so that the methane, the oxygen and the nitrogen can be separated, and the methane, the oxygen and the nitrogen can be separatedThe problems of utilization and transportation of the coal bed gas are solved.
Is currently applied to CH4/N2The separation technology mainly comprises adsorption, absorption, low-temperature deep cooling, membrane separation, hydrate separation and the like. The cryogenic separation technology is mature, high-purity products can be obtained, but the whole process needs to be carried out at low temperature, equipment is complex, investment is large, energy consumption is large, and the method is only suitable for large coal mines with daily treatment capacity of coal bed gas of hundreds of thousands of cubic meters; the solvent absorption method has disadvantages in that the solubility of gas is low, the treatment amount is small, the solvent regeneration speed is slow, and it is suitable for only a small amount of N2Absorption, which is not applicable to the separation and purification of low-concentration coal bed gas; simple membrane separation equipment, low investment and low operating cost, but is suitable for CH4And N2The separation membrane with high performance and high selective permeability is yet to be researched and developed. The hydrate separation technology has wide research prospect, but the technology is still in the initial exploration stage and has a series of problems to be solved, and the technology is still in the initial research stage and has great difference from the practical application. While direct conversion of methane to liquid phase products will also effect CH4And N2In H2O2In the presence of the nitrogen, the methane and the oxygen react at low temperature to be converted into liquid-phase products, and nitrogen is left in a gas phase, so that the separation of the methane and the nitrogen is realized.
For low-concentration coal bed gas with methane content below 30%, the coal bed gas is difficult to use and is in H2O2In the presence of the catalyst, OH & free radicals can be generated as an initiator to break C-H of methane, so that the methane is activated, and can be converted into liquid product methanol under the condition of low temperature. At H2O2When the low-temperature conversion of methane is carried out in the presence of the ionic liquid, because the reaction is carried out in a liquid phase, the solubility of the methane in a solvent is very important, then safe and nontoxic water is mostly used as the solvent in the current research, and the solubility of the methane in the water is very low, so that the use of the solvent with high methane solubility has very important significance, and the ionic liquid which is green, safe and high in boiling point is well selected in consideration of the problems of high toxicity and unsafety of the organic solvent, so that the dissolution of the methane can be improvedThe contact between reactants and the catalyst is increased, the mass transfer resistance is reduced, and the method has important significance for the separation of subsequent products.
Disclosure of Invention
The invention aims to provide a catalyst for preparing methanol by low-temperature conversion of low-concentration coal bed gas and a method for preparing methanol by using the catalyst. The method can reduce the temperature of low-concentration coal bed gas conversion and realize high-value utilization of the coal bed methane.
The method for preparing the methanol from the low-concentration coal bed gas is characterized in that a catalyst is used, an ionic liquid is used as a solvent to increase the solubility of the methane, and H is used2O2The initiator provides OH & free radical to activate methane, and the methane can be converted into methanol under low temperature condition. The catalyst prepared by the process method has good performance in the process of converting methane into methanol at low temperature.
The preparation process of the catalyst comprises the following steps: the preparation method of the catalyst comprises the following specific steps:
(1) weighing a proper amount of prepared noble metal salt solution, and dissolving the noble metal salt solution in a proper amount of deionized water to ensure that the metal concentration is 0.16-5 mmol.L-1；
(2) Weighing a certain amount of nitrogen source, adding the nitrogen source into the solution to enable the molar ratio of the metal to the nitrogen source to be 1:2, and stirring until the nitrogen source is completely dissolved;
(3) adding newly prepared 0.1-5M NaBH4Dissolving in the solution to produce a dark brown colloid;
(4) and (4) freeze-drying the colloid obtained in the step (3), and roasting for 3-5h at the temperature of 800-1000 ℃ in an inert atmosphere to obtain the catalyst. In the invention at H2O2The method for converting low-concentration coal bed gas into methanol at low temperature in the presence of the methanol comprises the following steps:
(1) weighing 20-300 mg of catalyst, and measuring 5-100 mL of ionic liquid and 5-100 mLH2O2Putting the mixture into a reaction kettle;
(2) filling low-concentration coal bed gas to 3-5MPa, reacting at 500-1200rpm and 50-100 ℃ for 30-300min, centrifugally separating the reacted liquid phase to obtain the catalyst, and distilling to separate the liquid phase product.
In the method, the noble metal salt is one or more of ammonium chloroplatinate, rhodium chloride, palladium nitrate and chloroauric acid.
In the method, the used nitrogen source is one or more of melamine, urea, potassium nitrate and ammonium phosphate.
In the method, the ionic liquid is one or more of 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-allyl-3-methylimidazolium chloride.
The invention has the following outstanding characteristics:
(1) with H2O2OH & free radical can be generated as an oxidizing agent, so that the C-H bond of methane can be broken at low temperature;
(2) the ionic liquid is used as solvent to increase the solubility of methane, so that methane and H2O2Better contact can be achieved;
(3) the catalyst has excellent electron transfer capacity and can promote the generation of OH & free radicals and the catalytic capacity of the catalyst and methane.
Detailed Description
The following are examples of the present invention, but the present invention is not limited to these examples.
Example 1
Preparing a catalyst: weighing a proper amount of prepared chloroauric acid and palladium nitrate solution, and dissolving the chloroauric acid and the palladium nitrate solution in a proper amount of deionized water to ensure that the metal concentration is 0.16 mmol.L-1Weighing a certain amount of melamine and adding the melamine into the solution to ensure that the molar ratio of the metal to the nitrogen source is 1:2, stirring the melamine and the nitrogen source until the melamine and the nitrogen source are completely dissolved, and adding freshly prepared 0.2M NaBH4And (3) adding the solution into the solution to generate a dark brown colloid, freezing and drying the obtained colloid, and roasting the colloid for 4 hours at 800 ℃ in an inert atmosphere to obtain the semiconductor AuPdN catalyst.
Evaluation of reaction Performance: catalytic reaction in a high-pressure reaction kettle, weighing 50mg of catalyst, and weighing 30mL of 1-butyl-3-methylimidazolium bis (tris)Fluoromethanesulfonyl) imide salt ionic liquid and 50mLH2O2Putting the mixture into a reaction kettle, and putting the mixture into the reaction kettle; filling low-concentration coal bed gas to 4MPa, reacting at 500rpm and 70 ℃ for 60min, centrifuging the reacted liquid phase to separate out the catalyst, and distilling to separate out a liquid phase product. The experimental results of example 1 are shown in table 1.
TABLE 1 AuPdN catalyst at H2O2Experimental results for conversion of coal bed methane to methanol in the Presence of
Example 2
Preparing a catalyst: weighing a proper amount of prepared ammonium chloroplatinate and rhodium chloride solution, and dissolving in a proper amount of deionized water to ensure that the metal concentration is 3 mmol.L-1Weighing a certain amount of urea, adding the urea into the solution until the molar ratio of the metal to the nitrogen source is 1:2, stirring until the urea is completely dissolved, and adding freshly prepared 2M NaBH4And (3) adding the solution into the solution to generate a dark brown colloid, freezing and drying the obtained colloid, and roasting the colloid for 3 hours at 900 ℃ in an inert atmosphere to obtain the semiconductor RhPtN catalyst.
Catalytic performance evaluation conditions: catalytic reaction is carried out in a high-pressure reaction kettle, 100mg of catalyst is weighed, 100mL of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and 100mLH are weighed2O2Putting the mixture into a reaction kettle, and putting the mixture into the reaction kettle; filling low-concentration coal bed gas to 3MPa, reacting for 30min at 800rpm and 100 ℃, centrifuging the reacted liquid phase to separate out the catalyst, and distilling to separate out a liquid phase product. The experimental results of example 2 are shown in table 2.
TABLE 2 RhPtN catalysts in H2O2Experimental results for conversion of coal bed methane to methanol in the Presence of
Example 3
Preparing a catalyst: weighing a proper amount of prepared chloroauric acid solution, and dissolving the chloroauric acid solution in a proper amount of deionized water to ensure that the metal concentration is 5 mmol.L-1Weighing a certain amount of ammonium phosphate, adding the ammonium phosphate into the solution to ensure that the molar ratio of the metal to the nitrogen source is 1:2, stirring until the ammonium phosphate and the nitrogen source are completely dissolved, and adding freshly prepared 3M NaBH4The solution is added into the solution to generate dark brown colloid, the colloid is obtained and is frozen and dried, and the colloid is roasted for 3h at 1000 ℃ under inert atmosphere, so that the semiconductor AuN catalyst is prepared.
Catalytic performance evaluation conditions: catalytic reaction is carried out in a high-pressure reaction kettle, 300mg of catalyst is weighed, 100mL of 1-allyl-3-methylimidazolium chloride ionic liquid and 50mLH are weighed2O2Putting the mixture into a reaction kettle, and putting the mixture into the reaction kettle; filling low-concentration coal bed gas to 3MPa, reacting at 500rpm and 50 ℃ for 100min, centrifuging the reacted liquid phase to separate out the catalyst, and distilling to separate out a liquid phase product. The experimental results of example 3 are shown in table 3.
TABLE 3 AuN catalyst in H2O2Experimental results for conversion of coal bed methane to methanol in the Presence of
Example 4
Preparing a catalyst: appropriate amount of prepared rhodium chloride and palladium nitrate solution is measured and dissolved in appropriate amount of deionized water to ensure that the metal concentration is 5 mmol.L-1Weighing a certain amount of urea and potassium nitrate, adding the urea and the potassium nitrate into the solution until the molar ratio of the metal to the nitrogen source is 1:2, stirring the solution until the metal and the nitrogen source are completely dissolved, and adding freshly prepared 3M NaBH4And (3) adding the solution into the solution to generate a dark brown colloid, freezing and drying the obtained colloid, and roasting the colloid for 3 hours at 900 ℃ in an inert atmosphere to obtain the semiconductor RhPdN catalyst.
Catalytic performance evaluation conditions: catalytic reaction is carried out in a high-pressure reaction kettle, 300mg of catalyst is weighed, 100mL of 1-allyl-3-methylimidazolium chloride ionic liquid and 50mLH are weighed2O2Will bePutting the mixture into a reaction kettle, and putting the mixture into the reaction kettle; filling low-concentration coal bed gas to 3MPa, reacting at 500rpm and 60 ℃ for 100min, centrifuging the reacted liquid phase to separate out the catalyst, and distilling to separate out a liquid phase product. The experimental results of example 4 are shown in table 4.
TABLE 4 RhdN catalyst at H2O2Experimental results for conversion of coal bed methane to methanol in the Presence of
Example 5
Preparing a catalyst: appropriate amount of prepared rhodium chloride, palladium nitrate and chloroauric acid solution are measured and dissolved in appropriate amount of deionized water to ensure that the metal concentration is 3.5 mmol.L-1Weighing a certain amount of urea and potassium nitrate, adding the urea and the potassium nitrate into the solution until the molar ratio of the metal to the nitrogen source is 1:2, stirring the solution until the metal and the nitrogen source are completely dissolved, and adding freshly prepared 2M NaBH4And (3) dissolving the solution into the solution to generate a dark brown colloid, freezing and drying the obtained colloid, and roasting the colloid for 3 hours at 900 ℃ under an inert atmosphere to obtain the semiconductor RhdAuN catalyst.
Catalytic performance evaluation conditions: the catalytic reaction is carried out in a high-pressure reaction kettle, 300mg of catalyst is weighed, and 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and 50mLH are weighed2O2Putting the mixture into a reaction kettle, and putting the mixture into the reaction kettle; filling low-concentration coal bed gas to 3.5MPa, reacting at 500rpm and 80 ℃ for 100min, centrifuging the reacted liquid phase to separate out the catalyst, and distilling to separate out a liquid phase product. The experimental results of example 5 are shown in table 5.
TABLE 5 RhdAuN catalyst in H2O2Experimental results for conversion of coal bed methane to methanol in the Presence of
Example 6
Preparing a catalyst: measurement ofDissolving a proper amount of prepared rhodium chloride solution in a proper amount of deionized water to ensure that the metal concentration is 3 mmol.L-1Weighing a certain amount of urea and potassium nitrate, adding the urea and the potassium nitrate into the solution until the molar ratio of the metal to the nitrogen source is 1:2, stirring the solution until the metal and the nitrogen source are completely dissolved, and adding newly prepared 2.5M NaBH4The solution is added into the solution to generate dark brown colloid, the colloid is obtained and frozen and dried, and is roasted for 3h at 850 ℃ under inert atmosphere, and the semiconductor RhN catalyst is prepared.
Catalytic performance evaluation conditions: the catalytic reaction is carried out in a high-pressure reaction kettle, 300mg of catalyst is weighed, and 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and 50mLH are weighed2O2Putting the mixture into a reaction kettle, and putting the mixture into the reaction kettle; filling low-concentration coal bed gas to 3.5MPa, reacting at 500rpm and 80 ℃ for 100min, centrifuging the reacted liquid phase to separate out the catalyst, and distilling to separate out a liquid phase product. The experimental results of example 6 are shown in table 6.
TABLE 6 RhN catalyst in H2O2Experimental results for conversion of coal bed methane to methanol in the Presence of
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