Influence of H2 on the gas-phase decomposition of formic acid: a theoretical study.

J Phys Chem A

Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, China 100871.

Published: October 2005

AI Article Synopsis

  • Gas-phase decomposition of formic acid leads to the production of CO + H2O and CO2 + H2, with a notable disparity in the CO/CO2 ratio compared to expected activation energy values.
  • The research used advanced computational methods to investigate how the presence of H2 affects the decomposition pathways of formic acid.
  • Findings indicate that H2 promotes the formation of CO + H2O over CO2 + H2 by facilitating the reduction of formic acid to formaldehyde, which then further dissociates into CO + H2, while also decreasing the presence of conformers necessary for decarboxylation.

Article Abstract

Gas-phase decomposition of formic acid results in final products CO + H2O and CO2 + H2. Experimentally, the CO/CO2 ratio tends to be large, in contradiction with mechanism studies, which show almost equal activation energies for dehydration and decarboxylation. In this work, the influence of H2 on the decomposition mechanism of HCOOH was explored using ab initio calculations at the CCSD(T)/6-311++G**//MP2/6-311++G** level. It was found that, in the presence of H2, the reaction channels leading to CO + H2O are more than those leading to CO2 + H2. With competitive energy, H2 addition to HCOOH can reduce the latter into HCHO, which then dissociates into CO + H2 catalyzed by H2O. Compared to trans-HCOOH, cis-HCOOH and cis-C(OH)2, conformers required for decarboxylation, are less populated due to interactions with H2.

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Source
http://dx.doi.org/10.1021/jp051973uDOI Listing

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