【作者】 丁春晓；

【导师】 林春绵；

【作者基本信息】 浙江工业大学 ， 环境工程， 2011， 硕士

【摘要】 超临界CO₂参与的有机合成反应（CO₂既作为反应溶剂,又作为反应物）,既可拓展CO₂资源化利用的可行途径,又是绿色合成的发展方向。碳酸二甲酯（DMC）的一步合成法是近年来的研究热点。本文以环氧丙烷（PO）和甲醇为原料,以金属醋酸盐复合K₂CO₃和KI作为催化剂,开展了在超临界CO₂中一步法合成DMC的研究。结果表明,在金属醋酸盐复合催化剂中,Zn（CH₃COO）₂具有突出的催化效果。催化剂用量的适当增加对加快反应进行及DMC的产生起到促进作用,该反应最合适的催化剂用量为反应物（PO+甲醇）加入量的4%。甲醇适当过量有助于提高DMC产率,VCH3OH: VPO=8是该反应较合适的物料配比。产物产率随着反应温度的逐渐升高呈增大趋势,超过443K后釜内产物易碳化变色,反应合适温度为433K。当压力控制在CO₂临界点附近时,反应可获得最佳DMC产率。反应时间增长,DMC产率随之逐渐增大,反应超过4h后基本保持平衡,最高产率可达54.3%。醋酸锌复合催化剂催化超临界CO₂一步法合成DMC的最佳反应条件为:催化剂配比为K₂CO₃:KI:Zn（CH₃COO）₂=1:1:2、用量为4%,物料配比VCH3OH: VPO=8,反应温度433K,反应压力7.5Mpa,反应时间4h。通过分析产物,提出了可能的反应机理。对反应动力学的研究最终得出该反应活化能Ea=89.81kJ/mol。丙二醇（PG）是一步法合成DMC中主要的副产物,探究其在CO₂中的转化有助于一步合成DMC反应的进一步发展。实验对以PG为原料在超临界CO₂中转化为碳酸丙烯酯（PC）的反应进行了研究。通过实验发现,只有在乙腈作溶剂和吸水剂的情况下,由碳酸钾、醋酸锌或醋酸镍作催化剂才可进行,但PC产率较小。通过对比,发现碳酸钾对该反应的催化效果最佳。PC产率随温度升高先增大后减小,在433K时达最高值。二氧化碳的压力为7.5Mpa时,PC产率达到最大值8.91%。加入耦合剂PO,能够有效增强超临界CO₂中PG转化为PC的反应效果,PC产率可提高50.9%。更多还原

【Abstract】 Study on organic synthesis reactions involved supercritical CO₂ （CO₂ could be not only a reagent but also a solvent）, which could expand the possible ways of CO₂ utilization and could be the direction of green synthesis. The study on one-pot synthesis of dimethyl carbonate in supercritical CO₂ is carried out, using propylene oxide（PO） and methanol as raw materials and metal acetate formulated with K₂CO₃ and KI as a catalyst.The results showed that: Zn（CH₃COO）₂ had outstanding catalytic effect in the reaction. Appropriate increase in the dosage of catalyst played a role in speeding up the reaction and in promoting the production of DMC, and the most appropriate dosage of reaction catalyst was 4% of the reactants amount（PO+CH3OH）. Excess of methanol could be properly help to improve the yield of DMC, VCH3OH:VPO = 8 was appropriate in one-pot DMC synthesis in supercritical CO₂. The yields gradually increased with reaction temperature rising, higher than 443K, the product was easily color changed because of carbonation, and thus the suitable reaction temperature is 433K. When the pressure was controlled at the vicinity of supercritical point, the yield of DMC got best. DMC yield increased with reaction time gradually increased, then remained stable after more than 4h, and the highest yield was 54.3%. The best reaction conditions catalyzed by zinc acetate composite catalysts in one-step synthesis of DMC in supercritical CO₂ was: K₂CO₃: KI: Zn（CH₃COO）₂ = 1:1:2, dosage 4%, reaction ratio VCH3OH:VPO=8, reaction temperature 433K, reaction pressure 7.5Mpa, reaction time 4h. By analyzing the products, the possible reaction mechanism and kinetics were proposed, and the activation energy was Ea=89.81kJ/mol.Propylene glycol（PG） is a major by-product in the one-pot synthesis of DMC, its conversion in CO₂ would play an important role in the further development of the synthesis of DMC. Using propylene glycol as raw materials in supercritical CO₂, the conversion of propylene glycol into propylene carbonate （PC） was studied. It showed that only in the case of acetonitrile as solvent and absorbent ,the catalysts such as K₂CO₃, Zn（CH₃COO）₂ or Ni（CH₃COO）₂ can be conducted, but the yield of propylene carbonate was small. By contrast, K₂CO₃ showed the best catalysis. With temperature increasing, yield of PC first increased then decreased, in the 433K, the yield reached the highest. When carbon dioxide pressure kept 7.5MPa, PC reached the maximum yield of 8.91%. Adding PO as coupling agent could effectively enhance the effect PG conversing into PC in supercritical CO₂, and PC yield can increased to 50.9%.更多还原