Technical benefits of using methane as a pyrolysis medium for catalytic pyrolysis of Kraft lignin

Catalytic fast pyrolysis of low sulfonated Kraft lignin was performed under different atmospheric environments such as N₂, CH_4, and the gas derived from CH₄ decomposition (CH₄-D). The use of Zn- or Mo-loaded HZSM-5 as catalyst led to a higher pyrolytic oil yield compared to parent HZSM-5 in CH₄ and CH₄-D atmospheres. The yields of benzene, toluene, and xylenes were increased by the synergistic effects from metal loading, higher H/C_eff ratio, higher acidity, and CH₄ activation. The enhanced CH₄ activation via metal loading resulted in higher methylation of alkyl moieties and 33% increase in the total yield of benzene, toluene, and xylenes in comparison to parent HZSM-5. A higher H/C_eff ratio of 6 via CH₄ decomposition led to the formation of a hydro-pyrolysis environment. Moreover, the CH₄-D environment showed H₂/CH₄ ratio of 0.36 in the product gas which warranted the presence of more H₂ under the CH₄-D pyrolysis environment.