合成气转化为甲醇和乙醇反应的速控步骤研究

Rate-Determining Steps in Syngas Conversion to Methanol and Ethanol

根据提出的合成气反应机理，用键级守恒－Ｍｏｒｓｅ势方法计算了Ｒｈ（１１１）面上合成气转化为甲醇、乙醇过程中各基元反应的活化能，结果表明ＣＯｓ＋Ｈｓ→ＨＣＯｓ、Ｈ２ＣＯｓ（或ＨＣＯＨｓ）＋Ｈｓ→ＣＨ２，ｓ＋ＯＨｓ分别是甲醇、乙醇生成反应中活化能最大的基元反应．通过考察Ｈ２／Ｄ２同位素效应，发现在高活性Ｒｈ基催化剂上，甲醇、乙醇生成反应同时表现出显著的氘逆同位素效应，表明这两个反应的速控步骤均为一步加氢反应，这与键级守恒的计算结果相符．

The BOC-MP (Bond Order Conservation-More Potential) approach has been used to identify the energetics associated with methanol and ethanol formation from syngas on Rh(111) surface. The BOC-MP calculation indicates that COs+Hs→HCOs and H_2COs (or HCOHs ) +Hs→CH_(2,s)+OHs are probably the rate-determining steps of methanol formation reaction and. of ethanol formation reaction, respectively. On the other hand, H_2/D_2 isotope effects in syngas conversion reactions have been investigated over V-promoted rhodium catalyst by performing CO+H_2 reaction and CO+D_2 reaction alternatively. Noticeable deuterium inverse isotope effects both on methanol formation and on ethanol formation are simultaneously observed, implying that the rate-determining steps involved in both methanol formation and ethanol formation are very probably, in each case, a step of hydrogenation. This result is in acccordance with that predicted by BOC-MP approach.