Production of bio-oil and biochar by the nitrogen-rich pyrolysis of cellulose with urea: Pathway of nitrile in bio-oil and evolution of nitrogen in biochar

Abstract

The production of nitrogen-containing chemicals from renewable biomass under nitrogen-rich conditions represents a promising technological pathway. Urea, as a nitrogen carrier, offers advantages over gaseous ammonia due to its easier storage and transportation. In this study, cellulose and two of its model compounds (cellobiose and glucose) were used as raw materials. The effects of different urea concentrations on the types and relative contents of bio-oil components and the properties of nitrogen-doped biochar were analyzed using GC-MS, FT-IR, and elemental analysis. We further clarified the evolution of exogenous nitrogen in nitrogen-rich pyrolyzed bio-oil and biochar with different urea concentrations. Cellobiose was found to be a more suitable feedstock for the production of nitrogen-containing compounds from nitrile than cellulose or glucose. A significant increase in the relative content of nitrile compounds (44.45%) was observed at a ratio of 40% cellulose to nitrogen carrier. Analysis of the bio-oil fraction led to the conclusion that there may be two main pathways for the production of the two nitrile compounds, acetonitrile and propionitrile. This research provides a better understanding of the N transfer pathways during the nitrogen-rich pyrolysis of cellulose and its model compounds (cellobiose and glucose) when using urea as the nitrogen carrier. This will facilitate further improvements in the yield of nitrogen-containing compounds in bio-oil.