Online Study on the Catalytic Hydrotreatment of Guaiacol in Liquid Phase by Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry

The detailed information on bio-oil upgrading reactions such as hydrogenolysis, hydrogenation, and hydrodeoxygenation is of great significance for improving the productivity and selectivity. Due to the compositional complexity of bio-oil and harsh upgrading conditions (e.g., with pressure of 10–30 MPa), conventional “cook-and-look” methods fail to track the real-time evolutions of products, limiting the deep understanding of the complex upgrading processes. In this work, we applied a feasible strategy by combining an autoclave with online soft photoionization mass spectrometry via a pressure- and fine particle-resistant sampling interface. With this strategy, the detailed evolution of guaiacol hydrotreatment with the catalysis of Ru–Ni/SiO2 under different hydrogen pressures was investigated. A comparison of products evolution for reactions under different conditions revealed that the reaction pathways are determined by hydrogen pressure. This newly developed methodology is crucial in detecting reaction evolution in a bio-oil upgrading process; it also provides a general strategy to investigate the chemical reactions under harsh conditions of relevance to synthetic chemistry and chemical engineering.