Spectroscopic study of hydroxymethyl radicals produced on MoOx/SiO2 catalysts by interaction of methanol with UV-induced [Mo5+-O-] triplet state

EPR along with MAS-NMR and QM spectroscopy have been used to investigate th e structure and reactivity of hydroxymethyl radicals formed upon UV-irradia tion of methanol adsorbed on MoOx/SiO2 catalysts. The use of natural and C- 13-enriched methanol allowed the authors to ascertain the H-1 superhyperfin e and C-13 hyperfine tensors. Based on the analysis of the magnetic paramet ers the structure of CR2OH radical interacting with the catalysts has been determined: it is non-planar and the C-H bonds are stretched. The hydroxyme thyl intermediates were found to reduce surface Mo6+ centers and adsorbed O -2 via an electroprotic mechanism involving electron transfer and release o f the hydroxyl proton.