Direct SVUV-PIMS identification of unstable oxygenated intermediates in ethanol to butadiene reaction

Abstract

Unstable oxygenated intermediates widely exist in biomass catalytic reactions but are difficult to be experimentally observed. Synchrotron-based vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was employed for the identification of unstable oxygenate intermediates in the ethanol to butadiene reaction over a MgO–SiO₂ catalyst. Acetaldol, which was suggested to be a key intermediate in this reaction but never experimentally observed before, was detected and proven to be sensitive to the reaction conditions in this work. Additionally, ketene, a less discussed intermediate, was also proven to exist in this reaction. These unstable oxygenate intermediates strengthen the reaction network, and directly observing them can give guidance for optimizing catalysts. It was believed that the SVUV-PIMS system could be used to detect further unstable oxygenated intermediates and play an important role in biomass catalytic reactions.