Application of Ca-based solid base heterogeneous catalyst in preparation of dimethyl carbonate
阅读说明：本技术 Ca基固体碱非均相催化剂在制备碳酸二甲酯中的应用 (Application of Ca-based solid base heterogeneous catalyst in preparation of dimethyl carbonate ) 是由 蒲彦锋 翟明路 王甜 金文雅 杨浩 霍琳梦 乔聪震 柏* 于 2020-12-23 设计创作，主要内容包括：本发明提供了一种Ca基固体碱非均相催化剂在制备碳酸二甲酯中的应用,所述Ca基固体碱非均相催化剂为Ca-3Co-4O-9催化剂,用于环状碳酸酯与甲醇酯交换制备碳酸二甲酯反应中。本发明的Ca基固体碱非均相催化剂Ca-3Co-4O-9具有耐高温、抗氧化、热稳定性好和化学稳定性高等优点,能够有效抑制Ca活性组分的流失,并且在常压、低温反应条件下实现较高的碳酸二甲酯收率,除此之外,该催化剂制备方法简单,重复使用性能稳定,易于工业化放大。(The invention provides an application of a Ca-based solid base heterogeneous catalyst in preparation of dimethyl carbonate, wherein the Ca-based solid base heterogeneous catalyst is Ca 3 Co 4 O 9 The catalyst is used in the reaction of preparing dimethyl carbonate by ester exchange of cyclic carbonate and methanol. The Ca-based solid base heterogeneous catalyst Ca of the invention 3 Co 4 O 9 Has the advantages of high temperature resistance, oxidation resistance, good thermal stability, high chemical stability and the like, can effectively inhibit the loss of Ca active components, and realizes higher carbonic acid di-ester under the conditions of normal pressure and low temperature reactionBesides, the methyl ester yield is high, the preparation method of the catalyst is simple, the reusability is stable, and industrial amplification is easy to realize.)
The application of Ca-based solid base heterogeneous catalyst in preparing dimethyl carbonate is characterized in that: the Ca-based solid base heterogeneous catalyst is Ca3Co4O9The catalyst is used in the reaction of preparing dimethyl carbonate by ester exchange of cyclic carbonate and methanol.
2. Use according to claim 1, characterized in thatThe method comprises the following steps: mixing methanol with cyclic carbonate, adding Ca3Co4O9And (3) reacting the catalyst for 10-120 min at the temperature of 10-70 ℃, wherein the reaction pressure is normal pressure.
3. Use according to claim 2, characterized in that: the molar ratio of the methanol to the cyclic carbonate is (2-12): 1, and the dosage of the catalyst is 0.5-2.5 wt% of the mass of the cyclic carbonate.
4. Use according to any one of claims 1 to 3, characterized in that: the Ca3Co4O9The catalyst is prepared by a sol-gel method, a coprecipitation method or a direct roasting method.
5. Use according to claim 4, characterized in that the sol-gel process is specifically as follows:
(1) transferring Ca salt, Co salt, citric acid and deionized water into a three-neck flask together, refluxing for 6 h at 80 ℃ under magnetic stirring, then heating to 105 ℃, adding an ethylene glycol dispersant, and continuing to reflux and stir for 6 h to obtain gel;
(2) drying the gel obtained in the step (1) in a blast drying oven, grinding the gel into fine powder, and calcining the fine powder in a muffle furnace to obtain Ca3Co4O9A catalyst.
6. Use according to claim 5, characterized in that: in the step (1), the total molar ratio of citric acid to Ca and Co is (1-1.5): 1, the molar ratio of deionized water to citric acid is (30-50): 1, and the mass ratio of the dispersant ethylene glycol to citric acid is (0.3-1): 1.
7. Use according to claim 4, characterized in that the coprecipitation process is specifically as follows:
(1) dissolving Ca salt and Co salt in deionized water, and magnetically stirring at 40 ℃ to fully mix the Ca salt and the Co salt to obtain a mixed solution A;
(2) dissolving sodium hydroxide and sodium carbonate in deionized water to form a precipitator B;
(3) keeping the pH = 8-10 in the stirring process, dropwise adding the precipitator B into the mixed solution A, standing for 2-6 h at 40 ℃ after dropwise adding is finished, filtering, washing, drying in a blast drying oven, and finally calcining in a muffle furnace to obtain Ca3Co4O9A catalyst.
8. Use according to claim 7, characterized in that: the concentration of the mixed solution A in the step (1) is 0.2-2 mol/L; in the step (2), the molar ratio of the sodium hydroxide to the sodium carbonate is 1: 1.
9. use according to claim 4, wherein the direct roasting process comprises the following steps: mechanically grinding and uniformly mixing Ca salt and Co salt precursors, drying for 4-12 h at 100-120 ℃ in a drying oven, and finally calcining in a muffle furnace to obtain Ca3Co4O9A catalyst.
10. Use according to any one of claims 5 to 9, characterized in that: the molar ratio of Ca to Co is 3:4, the calcining temperature in a muffle furnace is 600-1000 ℃, the calcining time is 4 hours, and the heating rate is 2-10 ℃/min.
Technical Field
The invention relates to the field of catalysts, in particular to an application of a Ca-based solid base heterogeneous catalyst in preparation of dimethyl carbonate.
Background
Dimethyl carbonate (DMC for short) is a novel, low-pollution and environment-friendly basic chemical raw material, and has the advantages of wide application range, large market capacity, greenness, low toxicity and high added value. The development of industries such as green solvents, non-phosgene polycarbon, non-phosgene polyurethane, new energy lithium batteries and green medicine synthesis can be effectively promoted. In recent years, DMC has been gradually replaced by MTBE in the United states as a gasoline additive to improve octane number, and attention of various national scholars to DMC has been increased.
At present, most of the domestic processes for producing DMC by ester exchange method use sodium methoxide or potassium methoxide as catalyst, for example, patents CN101774888A and CN1569807A both use methanol and propylene carbonate as raw materials, and use sodium methoxide as homogeneous catalyst, so as to obtain DMC products with higher yield. However, the homogeneous catalysts sodium methoxide or potassium methoxide are sensitive to water, and sodium methoxide becomes sodium hydroxide after the reaction, and cannot be recycled. To separate sodium hydroxide from the product, CO is currently introduced into the sodium hydroxide-containing product mixture2And water to convert sodium hydroxide into sodium carbonate crystals for removal, the increased separation route, combined with the use of large amounts of sodium methoxide, leads to increased production costs of DMC.
In order to overcome the problem of difficult separation and recovery of the existing homogeneous catalyst, the heterogeneous solid base catalyst is favored by the majority of researchers and enterprises. In this regard, Amberlyst 39 Wet ion exchange resin catalyst (Applied Catalysis B: Environmental: 2012, 125: 486-；MgO-CeO2Complex metal oxide catalysts (Catalysis Letters: 2007, 118: 30-35); Na/ZrO2Heterogeneous catalysts such as supported catalysts (microporus and mesoporus Materials: 2007, 102: 304-. For this reason, a Ca-based metal oxide catalyst having low temperature and high activity has once been a hot spot. Patent CN105879892B adopts a strategy of fixing active component Ca by a hydrotalcite-like structure to synthesize Ca-Al-O-X (X = CO)3 2-、NO3 -、F-、Cl-Or Br-) The catalyst is used, and the DMC yield is 30.7-58.4% under the conditions of normal pressure, reaction temperature of 30-70 ℃ and reaction time of 0.5-2 h. Although the catalyst can synthesize DMC at low temperature, after 5 times of repeated use, the yield of dimethyl carbonate is reduced from 55.7% to 47.2%, the loss phenomenon of the catalyst active component Ca still exists, the preparation process of the catalyst is complex, and the accurate control of the hydrotalcite-like structure is difficult.
Generally speaking, the existing heterogeneous solid base catalyst generally needs higher reaction temperature, the high temperature is easy to cause the generation of byproducts, and the high temperature is also easy to polymerize the polyol. Therefore, how to design and adjust the catalyst structure and obtain a novel Ca-based solid base catalyst with low temperature and high activity is urgent.
Disclosure of Invention
The invention provides an application of a Ca-based solid base heterogeneous catalyst in preparation of dimethyl carbonate, which utilizes a special mismatch layer cobaltate structure Ca of a cobalt-calcium composite metal oxide3Co4O9Aims at efficiently fixing an active component Ca, thereby providing a low-temperature, high-activity, green and environment-friendly high-performance heterogeneous solid base catalyst for preparing DMC by methanol transesterification.
The technical scheme for realizing the invention is as follows:
use of a Ca-based solid base heterogeneous catalyst for the preparation of dimethyl carbonate, said catalystThe Ca-based solid base heterogeneous catalyst is Ca3Co4O9The catalyst is used in the reaction of preparing dimethyl carbonate by ester exchange of cyclic carbonate and methanol.
Mixing methanol with cyclic carbonate, adding Ca3Co4O9And (3) reacting the catalyst for 10-120 min at the temperature of 10-70 ℃, wherein the reaction pressure is normal pressure.
Preferably, the cyclic carbonate may be ethylene carbonate or propylene carbonate.
The molar ratio of the methanol to the cyclic carbonate is (2-12): 1, and the dosage of the catalyst is 0.5-2.5 wt% of the mass of the cyclic carbonate.
The Ca3Co4O9The catalyst is prepared by a sol-gel method, a coprecipitation method or a direct roasting method.
The sol-gel method is specifically as follows:
(1) transferring Ca salt, Co salt, citric acid and deionized water into a three-neck flask together, refluxing for 6 h at 80 ℃ under magnetic stirring, then heating to 105 ℃, adding an ethylene glycol dispersant, and continuing to reflux and stir for 6 h to obtain gel;
(2) drying the gel obtained in the step (1) in a blast drying oven, grinding the gel into fine powder, and calcining the fine powder in a muffle furnace to obtain Ca3Co4O9A catalyst.
In the step (1), the total molar ratio of citric acid to Ca and Co is (1-1.5): 1, the molar ratio of deionized water to citric acid is (30-50): 1, and the mass ratio of the dispersant ethylene glycol to citric acid is (0.3-1): 1.
The coprecipitation method is specifically as follows:
(1) dissolving Ca salt and Co salt in deionized water, and magnetically stirring at 40 ℃ to fully mix the Ca salt and the Co salt to obtain a mixed solution A;
(2) dissolving sodium hydroxide and sodium carbonate in deionized water to form a precipitator B;
(3) keeping the pH = 8-10 in the stirring process, dropwise adding the precipitator B into the mixed solution A, standing for 2-6 h at 40 ℃ after dropwise adding is finished, filtering, washing, and drying in a blast drying oven, and finallyThen calcining in a muffle furnace to obtain Ca3Co4O9A catalyst.
The concentration of the mixed solution A in the step (1) is 0.2-2 mol/L; in the step (2), the molar ratio of the sodium hydroxide to the sodium carbonate is 1: 1.
the direct roasting method comprises the following steps: mechanically grinding and uniformly mixing Ca salt and Co salt precursors, drying for 4-12 h at 100-120 ℃ in a drying oven, and finally calcining in a muffle furnace to obtain Ca3Co4O9A catalyst.
The molar ratio of Ca to Co is 3:4, the calcining temperature in a muffle furnace is 600-1000 ℃, the calcining time is 4 hours, and the heating rate is 2-10 ℃/min.
The invention has the beneficial effects that: the Ca-based solid base heterogeneous catalyst Ca of the invention3Co4O9The catalyst has the advantages of high temperature resistance, oxidation resistance, good thermal stability, high chemical stability and the like, can effectively inhibit the loss of Ca active components, and realizes higher dimethyl carbonate yield under the reaction conditions of normal pressure and low temperature.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 shows the cobaltate structure Ca of the mismatch layer3Co4O9Catalyst Scanning Electron Microscopy (SEM) spectra.
FIG. 2 shows the cobaltate structure Ca of the mismatch layer3Co4O9High power transmission electron microscopy (HR-TEM) spectra of the catalyst.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
The catalyst was prepared by sol-gel method, 10.12g Ca (NO) was weighed3)2·4H2O, 16.63g of Co (NO)3)2·6H2O salt, 19.21g of citric acid and 54mL of deionized water are jointly transferred into a 250mL three-neck flask, refluxed for 6 hours at 80 ℃ under magnetic stirring, then heated to 105 ℃, added with 5.76g of dispersant ethylene glycol and continuously refluxed and stirred for 6 hours. Then the formed gel is placed in a forced air drying oven for drying for 12 h at 110 ℃, is ground into fine powder and then is calcined for 4h at 800 ℃ in a muffle furnace at the heating rate of 2 ℃/min, thereby obtaining Ca3Co4O9A catalyst.
Adding 0.20g of catalyst into a kettle-type reactor, adding 6.40g of methanol and 2.55g of propylene carbonate raw material, reacting for 2 hours at 60 ℃ under stirring, and analyzing by using a gas chromatography after the product is cooled, wherein the conversion rate of the propylene carbonate is 57.5 percent, and the yield of the dimethyl carbonate is 53.9 percent.
Example 2
The catalyst was prepared by sol-gel method, 10.12g Ca (NO) was weighed3)2·4H2O, 16.63g of Co (NO)3)2·6H2O salt, 28.82g of citric acid and 90mL of deionized water are jointly transferred into a 250mL three-neck flask, refluxed for 6 hours at 80 ℃ under magnetic stirring, then heated to 105 ℃, added with 8.64g of dispersant glycol and continuously refluxed and stirred for 6 hours. Then the formed gel is placed in a forced air drying oven for drying for 12 h at 110 ℃, is ground into fine powder and then is calcined for 4h at 800 ℃ in a muffle furnace at the heating rate of 2 ℃/min, thereby obtaining Ca3Co4O9A catalyst.
Adding 0.20g of catalyst into a kettle-type reactor, adding 6.40g of methanol and 2.55g of propylene carbonate raw material, reacting for 2 hours at 60 ℃ under stirring, and analyzing by using a gas chromatography after the product is cooled, wherein the conversion rate of the propylene carbonate is 55.5 percent, and the yield of the dimethyl carbonate is 52.7 percent.
Example 3
The catalyst was prepared by sol-gel method, 10.12g Ca (NO) was weighed3)2·4H2O, 16.63g of Co (NO)3)2·6H2O salt, 24.01g of citric acid and 90mL of deionized water are jointly transferred into a 250mL three-neck flask, refluxed for 6 hours at 80 ℃ under magnetic stirring, then heated to 105 ℃, added with 9.0g of dispersant glycol, and continuously refluxed and stirred for 6 hours. Then the formed gel is placed in a forced air drying oven for drying for 12 h at 110 ℃, is ground into fine powder and then is calcined for 4h at 800 ℃ in a muffle furnace at the heating rate of 2 ℃/min, thereby obtaining Ca3Co4O9A catalyst.
Adding 0.20g of catalyst into a kettle-type reactor, adding 6.40g of methanol and 2.55g of propylene carbonate raw material, reacting for 2 hours at 60 ℃ under stirring, and analyzing by using a gas chromatography after the product is cooled, wherein the conversion rate of the propylene carbonate is 71.2 percent, and the yield of the dimethyl carbonate is 70.3 percent.
Example 4
The catalyst preparation method and evaluation conditions differ from example 3 as follows: the catalyst was evaluated to react for 2h with stirring at 30 ℃ with a propylene carbonate conversion of 70.2% and a dimethyl carbonate yield of 69.5%.
Example 5
The catalyst preparation method and evaluation conditions differ from example 3 as follows: the catalyst was evaluated to react for 10min at 60 ℃ with stirring, propylene carbonate conversion was 20.5% and dimethyl carbonate yield was 18.4%.
Example 6
The catalyst preparation method and evaluation conditions differ from example 3 as follows: the catalyst was evaluated to react for 2h with stirring at 10 ℃ with a propylene carbonate conversion of 25.4% and a dimethyl carbonate yield of 24.8%.
Example 7
The catalyst preparation method and evaluation conditions differ from example 3 as follows: 6.40g of methanol and 1.7g of propylene carbonate raw material were added, the conversion rate of propylene carbonate was 69.8%, and the yield of dimethyl carbonate was 68.7%.
Example 8
The catalyst preparation method and evaluation conditions differ from example 3 as follows: 6.40g of methanol and 10.20g of propylene carbonate raw material were added, the propylene carbonate conversion rate was 49.4%, and the dimethyl carbonate yield was 48.2%.
Example 9
The catalyst is prepared by a coprecipitation method, 9.38g of CaCl is weighed2·6H2O, 13.59g of C.degree.l2·6H2The O salt was dissolved in 100 ml of deionized water and mixed well by magnetic stirring at 40 ℃ to form a mixed solution A. Then 5.6g of sodium hydroxide and 14.84g of sodium carbonate are dissolved in 50ml of deionized water to form a precipitating agent B; and (3) dropwise adding the solution B into the solution A while keeping the pH =9 in the stirring process, standing for 4h at 40 ℃ after dropwise adding, filtering, washing, drying for 12 h at 120 ℃ in a forced air drying oven, and finally calcining for 4h at 800 ℃ in a muffle furnace at the heating rate of 2 ℃/min. To obtain Ca3Co4O9A catalyst.
Adding 0.20g of catalyst into a kettle-type reactor, adding 6.40g of methanol and 2.55g of propylene carbonate raw material, reacting for 2 hours at 60 ℃ under stirring, and analyzing by using a gas chromatography after the product is cooled, wherein the conversion rate of the propylene carbonate is 67.2 percent, and the yield of the dimethyl carbonate is 65.4 percent.
Example 10
The catalyst was prepared by direct calcination, weighing 7.55g of Ca (CH)3COO)214.23g of Co (CH)3COO)2·4H2And mechanically grinding the O salt precursor to uniformly mix the O salt precursor and the O salt precursor. Then directly drying the mixture in a drying oven at 110 ℃ for 12 h, calcining the mixture in a muffle furnace at 800 ℃ for 4h at the heating rate of 2 ℃/min to obtain Ca3Co4O9A catalyst.
Adding 0.20g of catalyst into a kettle-type reactor, adding 6.40g of methanol and 2.55g of propylene carbonate raw material, reacting for 2 hours at 60 ℃ under stirring, and analyzing by using a gas chromatography after the product is cooled, wherein the conversion rate of the propylene carbonate is 58.8 percent, and the yield of the dimethyl carbonate is 56.7 percent.
Example 11
The catalyst preparation method and evaluation conditions differ from example 10 as follows: calcining the mixture for 4 hours in a muffle furnace at the temperature of 600 ℃, wherein the conversion rate of the propylene carbonate is 55.1 percent, and the yield of the dimethyl carbonate is 54.0 percent.
Example 12
The catalyst preparation method and evaluation conditions differ from example 10 as follows: calcining the mixture for 4 hours at 1000 ℃ in a muffle furnace, wherein the conversion rate of the propylene carbonate is 51.5 percent, and the yield of the dimethyl carbonate is 50.4 percent.
Example 13
The catalyst preparation method and evaluation conditions differ from example 10 as follows: the catalyst was evaluated to react for 2h with stirring at 10 ℃ with a propylene carbonate conversion of 21.2% and a dimethyl carbonate yield of 20.1%.
Example 14
The catalyst preparation method and evaluation conditions differ from example 10 as follows: 6.40g of methanol and 2.20g of ethylene carbonate were added, the conversion of ethylene carbonate was 61.5% and the yield of dimethyl carbonate was 59.8%.
Example 15
The catalyst used in example 3 was centrifuged and added again to carry out the above reaction under the same conditions, and the reaction was repeated 10 times, with the following experimental results:
the above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
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