Unraveling the Role of Reaction Environment and Catalysts for Pyrolysis of Technical Lignin into Different Functional Bio-Oil Yield

Catalytic pyrolysis of Kraft Lignin (KL) experiments were carried out at different temperatures (350-500 degrees C) over base MgO, acidic ZSM-5 and mixture of MgO-ZSM-5 catalysts under different environments (N-2 and CO2). Non-catalytic reaction produced maximum bio-oil (35.3 wt%) under CO2 at 450 degrees 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 N-2 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 N-2. Significant amount oxygen content reduced with the mixture of catalyst (MgO-ZSM-5, 1:1 ratio) under N-2 with the increasing of aromatic hydrocarbon. Higher heating value bio-oil was obtained with catalytic up-gradation.