Unraveling the role of reaction environment and catalysts for pyrolysis of technical lignin into different functional bio-oil yield

Abstract

Catalytic pyrolysis of Kraft Lignin (KL) experiments were carried out at different temperatures (350–500 °C) over base MgO, acidic ZSM-5 and mixture of MgO-ZSM-5 catalysts under different environments (N2 and CO2). Non-catalytic reaction produced maximum bio-oil (35.3 wt%) under CO2 at 450 °C. Upgrading of pyrolysis vapor under different environment with catalysts produced lower bio-oil as it is enhanced cracking and coke formation. Higher intensity peak at 1695–1720 cm-1 was found in up-gradation pyrolysis KL vapor under CO2, which showed that the higher aldehyde/acidic or ketone functionality in bio-oil. The content of monocyclic aromatic hydrocarbons increased whereas phenolic compound decreased with using the catalysts under N2 while acidic functionality increased under CO2 environment. Our results suggest that mixture of catalysts showed synergistic effects which increased the bio-oil quality. Overall, mixture of MgO-ZSM-5 showed the highest yield of aromatic hydrocarbons (ca. 49.2%) under N2. Significant amount oxygen content reduced with the mixture of catalyst (MgO-ZSM-5, 1:1 ratio) under N2 with the increasing of aromatic hydrocarbon. Higher heating value bio-oil was obtained with catalytic up-gradation.