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 N ₂ , CH _4, and the gas derived from CH ₄ decomposition (CH ₄ -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 CH ₄ and CH ₄ -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 CH ₄ activation. The enhanced CH ₄ 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 CH ₄ decomposition led to the formation of a hydro-pyrolysis environment. Moreover, the CH ₄ -D environment showed H ₂ /CH ₄ ratio of 0.36 in the product gas which warranted the presence of more H ₂ under the CH ₄ -D pyrolysis environment.
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