摘要:
研究了在甲醇、乙醇温和溶液中,氧化羰化一步合成不对称碳酸甲乙酯(MEC)反应。通过热力学计算考察了反应的可行性及程度。计算结果表明,在298.2 K下主反应平衡常数为2.39×1080,说明此反应的可行性和程度均很大。实验发现在氧化羰化合成碳酸甲乙酯的过程中,不仅存在氧化羰化过程,同时也存在酯交换过程；含氮席夫碱(Schiff)的种类,甲醇和乙醇相对用量,反应温度和压力对碳酸甲乙酯(MEC)的合成均有影响。当以氯化亚铜(CuCl)/1,10-菲罗啉(phen)/N-甲基咪唑(NMI)为催化剂时,摩尔比n(CuCl)∶n(NMI)∶n(phen) =1∶1.25∶1.25,在393 K,2.4MPa,VMeOH∶VEtOH=2∶8,CuCl浓度为0.20 mol/L的条件下,反应2 h,甲醇的转化率为44.3%,乙醇的转化率为22.3%, MEC产率为10.4%。与单纯CuCl催化剂相比,甲醇和乙醇的转化率分别提高17倍和9倍,MEC产率提高74倍。对氧化羰化反应机理也进行了探讨。
Abstract:
The oxidative carbonylation of methanol and ethanol to asymmetric methyl ethyl carbonate (MEC)catalyzed by CuCl coordinated with Schiff base ligands has been studied. A thermodynamic analysis of this process was carried out to discuss the possibility. The equilibrium constant of the main reaction at 298.2 K is 2.39×1080, so the possibility of this reaction is high. The effects of volume ratio of methanol to ethanol, molar ratio of 1,10-phenanthroline(phen)to N-methylimidazole(NMI), temperature, pressure on the conversion of methanol, ethanol and the yield of methyl ethyl carbonate have been investigated. CuCl/phen/NMI catalytic system was found to be active in the ox-idative carbonylation of methanol and ethanol to asymmetric methyl ethyl carbonate. When the reaction was carried out for 2 h at 393 K and 2.4 MPa (CO+O2) in the MeOH/EtOH system, with CuCl 0.20 molL-1, n(CuCl)∶n(phen)∶n(NMI) =1∶1.25∶1.25, and the ratio of vMeOH/vEtOH =2∶8, the conversion of methanol and ethanol are 44.3% and 22.3%, 17 and 9 times higher than that of CuCl system. The yield of MEC was 10.4%, which is increased about 74 times. The mechanism of synthesis of asymmetric carbonate was also discussed in detail.
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