Selective hydrogenolysis of C-O bonds in lignin and its model compounds over a high-performance Ru/AC catalyst under mild conditions

Study of Ni-ZSM-5 Catalysts in the Hydrogenolysis of Benzyl Phenyl Ether: Effects of Ni Loading, Morphology, and Reaction Conditions

This work investigates the activity of a series of Ni catalysts under a range of reaction conditions for the conversion of a lignin model compound (benzyl phenyl ether) to aromatic compounds. A series of transition metal-based catalysts (Ni-ZSM-5) have been prepared with different metal loadings (5, 10 and 20%) via an excess impregnation method. The materials were characterized using power X-ray diffraction (p-XRD), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) confirming the formation of a set of dispersed, metallic and spherical nanoparticles on all materials. On a 10% Ni-ZSM-5 material, the formation of a set of nanoparticles with a tetrahedral shape was noted. The materials were applied in the cleavage of the ether bond of a lignin model compound (benzyl phenyl ether) via hydrogenolysis in a range of organic solvents (1-butanol, ethanol, 2-propanol and pentane) and under two different atmospheres (H2 and Ar). 2-Propanol was shown to be the optimal solvent for the reaction confirming its propensity to act as a H-transfer material and the morphology of the supported nanoparticles was shown to have an important effect on the reactivity of the catalysts.

Solvent-Free Catalytic Hydrotreatment of Lignin to Biobased Aromatics: Current Trends, Industrial Approach, and Future Perspectives

Lignin is the only naturally occurring, renewable biopolymer and an alternative for the production of six-membered aromatic chemicals. The utilization of lignin can increase the additional revenue of biorefineries and reduce the dependence on crude oil for the production of aromatic chemicals. Therefore, the development of technologies for the production of valuable chemicals from lignin waste in biorefineries is of great importance. Catalytic hydrotreatment of lignin is considered one of the most promising technologies for the production of biobased aromatic chemicals and fuels. Among the various hydrotreatment routes, the solvent-free hydrotreatment approach is advantageous because this process reduces production costs and is similar to petroleum refinery processes such as cracking and heteroatom removal. This review addresses recent developments in solvent-free catalytic hydrotreatment of various lignins such as sulfur-containing, sulfur-free, and pyrolytic lignins to produce low oxygen-containing aromatics such as alkylphenolics in batch, semicontinuous, and continuous reactors. Special emphasis is given to the various noble and non-noble metal catalysts, the best route between single and two-stage processing, key factors in solvent-free depolymerization of lignin, techno-economic evaluation, crude oil vs lignin oil refining, challenges and future prospects, etc.

Catalytic transfer hydrogenolysis of lignin derived aromatic ethers over MOF derived porous carbon spheres anchored by Ni species

The efficient hydrogenolysis of CO ether bonds in lignin is the key for producing bio-oil and high-value chemicals. In this work, we synthesized a series of Ni-MOF-derived porous carbon spheres anchored Ni catalysts (Ni/C-x-T) with different metal/ligand molar ratios and calcination temperatures through solvothermal and carbothermal reduction method, and evaluated their catalytic transfer hydrogenolysis (CTH) performance for lignin model compounds using isopropanol as H-donor. The Ni/C-2-400 catalyst exhibited the excellent CTH performance, affording almost 100 % conversion of 2-phenoxy-1-phenylethanol even at a low reaction temperature of 120 °C. It was worth noting that the further hydrogenation of hydrogenolysis products phenol and ethylbenzene could be controlled by adjusting the reaction conditions, achieving phenol and ethylbenzene as main products at 120 °C, cyclohexanol and ethylbenzene at 140 °C, and cyclohexanol and ethylcyclohexane at 200 °C for 4 h. Based on the characterization results, the high catalytic activity of Ni/C-2-400 was attributed to the good dispersion and small particle size of metal Ni particles. Mechanistic studies showed that the cleavage of CO ether bonds was the main reaction pathway, and high temperature helped accelerate hydrogenolysis and subsequent hydrogenation. Moreover, the Ni/C-2-400 catalyst had good stability and applicability to other model compounds. This work could provide some help for the upgrading of lignin and its derivative.