含卡宾或烯酮基铁簇合物作为乙醇合成机理模型的研究

Model Reaction of Supported(μ-CH_2) or (μ_3-CCO)-Metal Carbonyl Clusters for Mechanism Study of Ethanol Synthsis

用含卡宾或烯酮的铁簇合物为模型,在模拟多相反应的条件下,研究了它们与H_2,H_2/CO,H_2/CO/CH_3OH 和H_2/CO/CD_3OD 的反应行为。在95℃和2.0 MPa的条件下,Fe_2(μ-CH_2)(CO)_8/SiO_2与含有合成气的甲醇反应可得 43％的醋酸甲酯,同时伴有甲烷、乙烷、乙烯、乙醛和乙醇等产物。与引入全氘代甲醇的合成气反应后,可得到氘代产物DCH_2COOCD_3和CH_3 COOCD_3.DCH_2 COOCD_3与A_cOCD_3(=DCH_2COOCD_3+CH_3COOCD_3)的相对丰度比随CD_3OD与H_2比值的减小而降低,由此可推测烯酮加成与烯酮氢化成乙酰基中间体这一对竞争反应。

Si02-supported Fe2(μ-CH2>(CO)8and Fe3(μ3-CCO)(CO)9 have been used to simulate the supported rhodium-catalysts for ethanol synthesis from syngas.Chemical trapping reaction with CH3OH and syngas gave CH3COOCH3in about 43 % yield, accompanying with CH3CHO, CH3CH2OH. CH4and C2-hydrocarbons at 95℃ , 2.0 MPa.CD3OD was also used in place of CH3OH and the reation products CH3CH2OH. CH3CHO. CH3COOCD3 and CH2DCOOCD3 have been obtained. The relative abundance of CH2DCOOCD3 to CH3COOCD3 in the reaction products was found to decrease (from 100%, 46%, 29%, 16%. 10% to 2%} with decreasing ratio of CD3OD:H2(from 3/0. 50/50, 34/50, 12/50, 8/50 to 1 /50.respectively).These results strongly supported the reaction pathway of metalloxycarbene-carbene-ketene-acetyl- ethanol(acetaldehyde) for ethanol synthesis over promoted rhodium catalysts.