Flexibilization of Biorefineries: Tuning Lignin Hydrogenation by Hydrogen Partial Pressure.

The present study describes an interesting and practical catalytic system that allows flexible conversion of lignin into aromatic or aliphatic hydrocarbons, depending on the hydrogen partial pressure. A combination of experiment and theory shows that the product distribution between aromatics and aliphatics can be simply tuned by controlling the availability of hydrogen on the catalyst surface. Noticeably, these pathways lead to almost complete oxygen removal from lignin biomass, yielding high-quality hydrocarbons. Thus, hydrogen-lignin co-refining by using this catalytic system provides high flexibility in hydrogen storage/consumption towards meeting different regional and temporal demands.

A Convergent Approach for a Deep Converting Lignin-First Biorefinery Rendering High-Energy-Density Drop-in Fuels.

Herein, a lignin-centered convergent approach to produce either aliphatic or aromatic bio-hydrocarbons is introduced. First, poplar or spruce wood was deconstructed by a lignin-first biorefining process, a technique based on the early-stage catalytic conversion of lignin, yielding lignin oils along with cellulosic pulps. Next, the lignin oils were catalytically upgraded in the presence of a phosphidated Ni/SiO2 catalyst under H2 pressure. Notably, selectivity toward aliphatics or aromatics can simply be adjusted by changes in H2 pressure and temperature. The process renders two distinct main cuts of branched hydrocarbons (gasoline: C6-C10, and kerosene/diesel: C14-C20). As the approach is H2-intensive, we examined the utilization of pulp as an H2 source via gasification. For several biomass sources, the H2 obtainable by gasification stoichiometrically meets the H2 demand of the deep converting lignin-first biorefinery, making this concept plausible for the production of high-energy-density drop-in biofuels.

Catalysis Meets Nonthermal Separation for the Production of (Alkyl)phenols and Hydrocarbons from Pyrolysis Oil.

A simple and efficient hydrodeoxygenation strategy is described to selectively generate and separate high-value alkylphenols from pyrolysis bio-oil, produced directly from lignocellulosic biomass. The overall process is efficient and only requires low pressures of hydrogen gas (5 bar). Initially, an investigation using model compounds indicates that MoCx /C is a promising catalyst for targeted hydrodeoxygenation, enabling selective retention of the desired Ar-OH substituents. By applying this procedure to pyrolysis bio-oil, the primary products (phenol/4-alkylphenols and hydrocarbons) are easily separable from each other by short-path column chromatography, serving as potential valuable feedstocks for industry. The strategy requires no prior fractionation of the lignocellulosic biomass, no further synthetic steps, and no input of additional (e.g., petrochemical) platform molecules.