Palladium nanoparticles supported by phosphoric acid-modified SiO2 as efficient catalysts for low-temperature hydrodeoxygenation of vanillin in water

Selective hydrodeoxygenation (HDO) of lignin derivatives is regarded as an important route to produce high value-added biochemicals and biofuels. However, the low-temperature HDO process performed in water is still of challenge. In this study, a series of Pd/PSNs catalysts was prepared via a facile impregnation method where phosphoric acid-modified silica nanospheres (PSNs) were used as the support and then Pd nanoparticles (Pd NPs) were uniformly dispersed on them. The as-prepared catalysts showed high activities in low-temperature HDO of vanillin (VAN) to 2-methoxy-4-methylphenol (MMP) in water. VAN could be fully converted after reaction at 45℃ for 8h in water and the corresponding yield of MMP was up to 95.5%. Detailed experimental studies demonstrated that both P species and Pd NPs on the surface of Pd/PSNs catalyst were active sites for the HDO of VAN and the presence of P species could accelerate the selective conversion of the intermediate (vanillyl alcohol, VAL) to MMP via a free-radical process, resulting in the superior catalytic performances. Besides, Pd/PSNs catalysts also exhibited excellent catalytic performances in HDO of other lignin derivatives with different functional groups to the corresponding products. This work provides a new idea for the selective production of high value-added biochemicals and biofuels from lignin derivatives. © 2023 Chemical Industry Press. All rights reserved.