Progress in application of the pyrolytic lignin from pyrolysis of biomass

Abstract

Bio-oil is a mixture of condensable volatiles and is produced by the pyrolysis of biomass. The production of biofuel from bio-oil via hydrotreatment has received considerable attention from both the research community and industry. However, for the effective conversion of bio-oil to biofuel, one key challenge that must be overcome is coke formation, especially at high temperatures. Coke is formed because of the presence of abundant organics in bio-oil with their reactive oxygen-containing functionalities and the heavy organics with large molecular structures. Pyrolytic lignin (PL), derived primarily from the pyrolysis of the lignin fraction in biomass, is a major component of the heavy organics in bio-oil. Understanding the properties of PL is important for solving the issue of coke formation during the polymerization/cracking of PL and for further utilizing PL for the production of chemicals, biofuels, and carbon materials. In this review, the progress toward understanding the properties of PL, the separation of PL from bio-oil, and the conversion of PL to other value-added products (i.e., biofuels, chemicals such as phenolics, aromatics, hydrogen, and radical scavengers, antioxidants, resins, carbon materials, and binders) was discussed, and techno-economic assessments of various routes for PL conversion were discoursed. Suggestions were provided for taking the next steps in each PL application, and potential challenges were analyzed and discussed in detail.