Theoretical Study On Reaction Mechanism Of Electrochemical Synthesis Oxalic Acid From Acetylene

Oxalic is the most simple binary acid, the binary acid and its derivatives areimportant material for chemical industry. In recent years, electrochemicalsynthesis technique is rapidly developed because of its unique advantages. Thenew idea that Oxalic acid is made by electrochemical synthesis technique on Ptcatalyst surface is put forward, but the reaction mechanism is not clear. Up tonow, a large number of experimental studies have been performed to explore theadsorption and reaction properties of acetylene on single-crystal metal surfacesusing first-principles method. It is a pity that few theoretical studies aresystematically carried out to fully investigate the mechanism and kinetics aboutthe reaction of oxidation of acetylene to oxalic acid at the fundamental level dueto the complexity of the reactions. At present in the aspect also needs to befurther discussed.In the paper, The mechanism on electrochemical synthesis to oxalic acidfrom acetylene on Pt(111) has been investigated using first-principles methodbased on density functional theory (DFT). Geometries and energies for all of the intermediates involved the conversion mechanism were analyzed. We mainlydiscusses the four key steps:â‘ the forming of CHCHO species;â‘¡the formingof CHOCHO species;â‘¢the forming of CHOCOOH species;â‘£the forming ofCOOHCOOH species.All the results show:(1) acetylene, glyoxal, acetaldehyde alcohol, glyoxylic acid, oxalic acid andother substances adsorbed at parallel bridge configuration on the surface of Pt(111), the adsorption energey were2.381,3.587,2.071,0.156,2.578eV,respectively.(2) O, OH and H2O molecules adsorbed at fcc site, O-bridge site and the Oatoms at top site on the surface of the Pt (111)，respectively. Its adsorptionenergy are0.143,0.079and0.035eV, respectively.(3) The reaction mechanism of acetylene selective oxide is:â‘ In the formation of CHCHO species, the main reaction is the reactionCHCH+OHâ†'CHCHOHâ†'CHCHO+H, and it is most likely to occur,followed by CHCH+OHâ†'CHCHOH+Oâ†'CHCHO+OH.â‘¡In the formation of CHOCHO species, the chemical reaction occursmainly is CHCHO+Oâ†'CHOCHO in this step.â‘¢In the formation of CHOCOOH species, the main step is CHOCHOâ†'CHOCO+OHâ†'CHOCOOH followed by CHOCHO+OHâ†'CHOCHOOH+Oâ†'CHOCOOH+OH. â‘£In the formation of CHCHO species, the main process of reaction ofgenerating is CHOCOOHâ†'COCOOH+OHâ†'COOHCOOH. So the mainprcess of generating Oxalic acid by acetylene oxidation isCHCH+OHâ†'CHCHOHâ†'CHCHO+Oâ†'CHOCHOâ†'CHOCO+OHâ†'CHOCOOHâ†'COCOOH+OHâ†'COOHCOOH.