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, CH4, 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/Ceff 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/Ceff 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.