Lignocellulosic Biomass Upgrading into Valuable Nitrogen-Containing Compounds by Heterogeneous Catalysts

Lignocellulosic biomass feedstocks represent a large variety of carbohydrates that can be readily accessed from woody biomass resources. Upgrading of lignocellulosic feedstocks into nitrogen-containing chemicals (N-chemicals) with a nitrogen source has been prosperously studied in recent years, especially via heterogeneous catalysis, providing a more sustainable and efficient way for high-value N-chemical manufactures compared to the fossil-based routes. This review gives an account of the up-to- date progresses on the heterogeneously catalyzed transformation of lignocellulosic feedstocks into various N-chemicals (more than 100 papers examined). In the review, the lignocellulosic feedstocks are divided into three categories including the aliphatic, furanic, and aromatic molecules. The details are depicted which cover the chemical routes, catalyst types, process parameters, etc. Next, reactor design, product separation, and scale-up were described. Additionally, green nitrogen sources to obviate the NH3 synthesis were discussed. Besides, the challenges/future directions in lignocellulosic upgrading for N-chemicals will be illustrated.