Reductive Catalytic Fractionation of Wheat Straw Biomass

Abstract

The reductive catalytic fractionation (RCF) is a promising method for the development of “lignin-first” biorefineries. Apart from the widely investigated virgin woody biomass, it is essential to explore the potential of waste biomass feedstocks. Herein, the RCF of wheat straw is examined to produce lignin mono-/oligomers along with a processable carbohydrate pulp. The use of different catalysts (Ru/C and Ru/Al2O3) and catalyst loadings (0–20% w/wbiomass) revealed the superior performance of Ru/C, which resulted in the largest yield of phenolic monomers (up to ∼25 wt % of initial acid-insoluble lignin) and in the lowest formation of high-molecular-weight fragments in the extracted lignin oil. Furthermore, the operating temperature was shown to substantially affect both lignin extraction–depolymerization and polysaccharides preservation–processability. For a reaction time of 3 h, an increase of the temperature from 200 to 250 °C resulted in a >2-fold boost of the yields of lignin oil and monophenolics, while the recovery of polysaccharides decreased by about 30 wt % (with ∼20% lower enzymatic digestibility). An economic assessment highlighted that the high-temperature treatment becomes the most profitable configuration as the market price of lignin products increases. Overall, this work provides insight into the adoption of the RCF for the upgrading of lignocellulose from inexpensive and widely available wheat straw biomass.