Catalytic upgrading of fast hydropyrolysis vapors from industrial kraft lignins using ZSM-5 zeolite and HY-340 niobic acid

Abstract Large amounts of lignin are produced in the pulp and paper industry and are still not used in a more valuable way. Lignin has great potential as a renewable raw material for the production of biofuels and high value chemical products. The aim of the present work was to study the hydropyrolysis process of two industrial kraft lignin types and evaluate the influence of operating temperature and the addition of two acid catalysts: a widely known commercial zeolite (ZSM-5) and niobic acid (HY-340), which has been poorly explored as a catalyst applied to biomass. HY-340, Nb2O5⋅nH2O, as well as commercial zeolites, has desirable acidic properties, and a low cost compared to traditional catalysts employed in catalytic pyrolysis. The composition of the vapors produced in a micropyrolyzer (CDS-5200) was analyzed in an online gas chromatograph coupled to a mass spectrometer (PY-GC/MS). The effects of operational parameters, such as reaction temperature and catalyst concentration added to lignins, were also investigated. The results showed that the use of ZSM-5 as a catalyst in hydropyrolysis reactions of both lignins promotes a significant increase in the formation of aromatic hydrocarbons. In the tests performed, the increase in selectivity for aromatic hydrocarbons reached a maximum of 98% of the area for lignin 1 and 99% for lignin 2. The addition of HY-340 in the reactions of catalytic hydropyrolysis of the industrial lignins resulted in an increase in the selectivity of open chain or aliphatic hydrocarbons, mainly n-alkanes, which reached a maximum value of 93% of area for lignin 1 and 92% for lignin 2.