Novel strategy to produce polyaromatic compounds at low temperature for the production of secondary chars

摘要

? 2023 The AuthorsThe production of polyaromatic compounds during biomass thermochemical processing at temperatures over 700 °C from the secondary reactions pyrolysis vapors is a well study phenomena. These compounds are sometimes used to produce carbonaceous materials (such as carbon black, carbon nanotubes). In the case of gasification these polyaromatic compounds form tars and are a major source of problems for the operation of these reactors. In this paper we explore the use of acid impregnation, particularly using phosphoric acid, to reduce the temperature at which small polyaromatic rings are formed and released from the biomass. The acid treatment of biomass was found to increase the yield of biochar (from 17 wt to 40 wt) and to be an excellent source of polyaromatic compounds (close to 15 wt on biomass dry basis). In this manuscript we explored the use of the small polyaromatic ring systems produced from the carbonization of acid-pretreated biomass as precursors for the synthesis of secondary carbons. A two-step pyrolysis process was conducted on acid-treated biomass, revealing that the volatiles produced in the first stage were primarily derived from the dehydration of anhydrosugars. In contrast, the volatiles produced in the second stage were found to be primarily composed of aromatic compounds similar to those produced in gasification processes, with low to no oxygen content. In this research, we have introduced an innovative strategy to maximize the benefits of acid-treated biomass pyrolysis by utilizing the low oxygen aromatic hydrocarbons compounds produced as a carbon source for the production of carbon nanostructures (CNS) on biochar-supported nickel catalysts. This methodology allows to produce polyaromatic compounds at very low temperature from lignocellulosic materials. This not only optimizes the utilization of biomass resources but also enhances the yield of high-value products and aligns with the principles of a circular economy.