Highly selective production of phenolic compounds from lignin pyrolysis with the strategy of hydrogen self-supply

In this study, a sealable fixed-bed reactor was developed to investigate the influence of gaseous products on lignin pyrolysis with a strategy of hydrogen self-supply, and lignin pyrolysis performances at various temperatures were monitored by the comprehensive characterization of the generated products, including gas, bio-oil and char. The results showed that the release of volatiles (both gas and bio-oil) from lignin was strengthened in this sealable system when the temperature rose, and therefore less char was left. Meanwhile no H 2 was detected under any of the operating conditions, which is a common component in pyrolysis gas from conventional reactors, indicating its participation in lignin pyrolysis. Furthermore, the formation of CO and CO 2 in the employed pyrolyzer benefited from not only the thermal evolution of feedstock, but also the interactions between char residues and generated gas components. Meanwhile, because of the hydrogen self-supply, compounds in bio-oil were enriched and only nine species were detected, which were all phenolic compounds. Vanillic acid was dominant, and its relative content was up to 38.86% for Alcell organosolv lignin and 34.41% for soda alkali lignin. This illustrates that highly selective production of phenolic compounds from lignin pyrolysis can be achieved by self-supplying hydrogen from pyrolysis gas.