Theoretical Study Of The Mechanism Of Formic Acid Decomposition Reaction By Au_n(n=1,3,6) Catalyst

Formic acid is an important chemical industry product,which is widely used in the field of chemical industry,medical treatment and so on.The waste water discharged by industrial application contains formic acid,which brings great harm to the environment and human body.At room temperature,pure formic acid is too stable to disintegrate.but at high temperature,there are two ways in the disintegration process of formic acid,including dehydrogenation and dehydration,respectively.Different catalysts will lead to different decomposition pathways of formic acid.The results indicate that the catalyst is effective for the decomposition of formic acid.In particular,the use of metal catalysts for the reaction of decomposition of formic acid to produce CO₂and H₂ is highly feasible and thus of high research value.The quantum chemistry theory was performed to investigate each reaction channel of the formic acid with the presence of the Au1/Au3/Au6 of catalyst.Geometry configurations of each stationary points are optimized under the B3LYP/6-311+G?d,p?level.The vibrational frequency and zero-point energy?ZPE?were calculated,and the activation energy of each reaction channel are obtaine with ZPE correction.The main contents of the paper are as follow.1)In the absence of catalysts,there are two ways in the decomposition process of formic acid,including dehydrogenation and dehydration,respectively.In the absence of catalyst,the activation energy in rate controlling step of optimum reaction channel of the two ways are 319.0 and 302.2 k J/mol,respectively,which indicates that HCOOH molecular is too stable to disintegrate.2)After the treatment of Au₃,the significantly reduction of the activation energy can be obvious in the rate controlling step of optimum reaction channel of the two ways,being 43.6 and 82.5 k J/mol,respectively.This phenomenon can be attributed to the introduction of Au₃,which activate the C-H and O-H bond to reduce the activation energy in the rate controlling step.The decomposition of formic acid are predicted to produce CO₂/H₂ and CO/H₂O,while the former is the main reaction pathway.3)After the treatment of Au₁/Au₃/Au₆,the disintegration ways of formic acid are prefer to produce the CO₂/H₂ without CO/H₂O by the Au₁ catalyst.In the presence of the Au₁ catalyst,the activation energy in rate controlling step of optimum reaction channel of the dehydrogenation is 22.06 k J/mol.In the presence of the Au₃ catalyst,the activation energy in rate controlling step of optimum reaction channel of the two ways are 43.6 and 82.5 k J/mol.In the presence of the Au₆ catalyst,the activation energy in rate controlling step of optimum reaction channel of the two ways are 170.67 and 164.89 k J/mol.The catalytic effect of Au₁ and Au₃ for the decomposition of formic acid was better than Au₆,and the catalytic effect of Au₁ was the best.This phenomenon can be attributed to the introduction of Au₆,which activates the C-H and O-H bond to reduce the activation energy in the rate controlling step.