Photocatalytic Upgrading of Lignin Oil to Diesel Precursors and Hydrogen

Abstract

Producing renewable biofuels from biomass is a promising way to meet future energy demand. Here, we demonstrated a lignin to diesel route via dimerization of the lignin oil followed by hydrodeoxygenation. The lignin oil undergoes CÀC bond dehydrogenative coupling over Au/CdS photocatalyst under visible light irradiation, co-generating diesel precursors and hydrogen. The Au nanoparticles loaded on CdS can effectively restrain the recombination of photogenerated electrons and holes, thus improving the efficiency of the dimerization reaction. About 2.4 mmol g catal À1 h À1 dimers and 1.6 mmol g catal À1 h À1 H 2 were generated over Au/CdS, which is about 12 and 6.5 times over CdS, respectively. The diesel precursors are finally converted into C16-C18 cycloalkanes or aromatics via hydrodeoxygenation reaction using Pd/C or porous CoMoS catalyst, respectively. The conversion of pine sawdust to diesel was performed to demonstrate the feasibility of the lignin-to-diesel route.Scheme 1. The Scheme for upgrading of lignin oil.

Photocatalytic Selective Oxidation of HMF Coupled with H2 Evolution on Flexible Ultrathin g-C3N4 Nanosheets with Enhanced N–H Interaction

“…Solar-driven water splitting to generate hydrogen energy (H 2 ) has been shown as a prospect to tackle the energy dilemma and environmental issues. , However, water oxidation with multielectron transfer always suffers from high overpotential and sluggish reaction kinetics, which slows down or even inhibits the half reaction of H 2 evolution. At present, most reported systems still require a hole scavenger to accelerate H 2 evolution, which inevitably leads to an increase in production costs and losses of hole oxidation capacity. − Thus, the replacement of traditional scavengers in photocatalytic H 2 evolution by renewable biomass to achieve catalytic oxidation of biomass into fine chemicals under ambient conditions has recently received wide attention. − …”

Facet-Dependent Electron Transfer Regulates Photocatalytic Valorization of Biopolyols

“…Photocatalysis shows great potential in a series of chemical reactions under mild conditions. − For example, photocatalytic valorization of biomass, which uses renewable solar energy and biomass, has been recently recognized as an efficient and feasible method to produce fuels and chemicals from biomass. − Photocatalysis involves the light-induced generation of electron–hole pairs and their transfer to adsorbed species on the semiconductor surface. The photoinduced electrons are generally captured and localized at some site in the crystal of the catalyst to some extent, named shallow trap/deep trap states, which strongly affect the electron transfer (ET) efficiency. , The ET from the conduction bands of the solid to the lowest unoccupied molecular orbital (LUMO) of the surface-bound species, ranging from several nanoseconds to several microseconds depending on the trapping state of the electrons, is a bottleneck step for photocatalysis. − However, the surface of a solid is nonuniform and consists of different facets, corners, and defects.…”

Hydrogen Bonding Promotes Alcohol C–C Coupling

“…Parallel to the reaction path, αHR may also be oxidized on semiconductors, producing acetaldehyde (AA) as the side product . CdS was used as the photocatalyst since it has been widely used for the photocatalytic conversion of alcohols. , Au nanoparticles (Au NPs) that serve as the reduction cocatalyst were immobilized on CdS to accelerate the hydrogen evolution half-reaction, thus allowing the oxidation half-reaction to be the rate-limiting step. Considering that the products are highly dependent on the oxidation half-reaction, any efficient way of altering the reaction paths of radical intermediates is expected to be discerned.…”