Bio-oil upgrading using dispersed unsupported MoS2 catalyst

Abstract

Fast pyrolysis bio-oil upgrading using a dispersed unsupported MoS2 catalyst, generated in-situ, was evaluated in a continuous flow reactor system. Light cycle oil (LCO), a typical petroleum refinery stream rich in aromatics, was selected as a reaction medium and a bio-oil-in-LCO microemulsion was used as a feeding strategy to ensure bio-oil is well distributed in LCO and suppress bio-oil polymerization especially at the reactor inlet. An aqueous solution of ammonium paramolybdate tetrahydrate was emulsified in LCO to form a stable water-in-oil microemulsion to ensure that the inorganic catalyst precursor is evenly dispersed in the feed stream. The impact of catalyst-to-bio-oil ratio on product properties, yields, oxygen removal and coke formation was investigated. Bio-oil deoxygenation as high as 90% was achieved and hydrogen consumption ranged between 316 and 723 L H2/L bio-oil within the investigated range of reaction conditions. The present work shows that an oil-phase product with significantly reduced oxygen content (0.56 wt%) and acidity (total acid number of 0.48 mg KOH/g) can be produced from bio-oils with minimal solids (coke) formation (0.8 to 1.8 g/100 g bio-oil). The experimental results demonstrate that the use of unsupported catalysts could provide a promising bio-oil upgrading alternative to conventional packed bed using supported catalysts, in which catalyst bed plugging and deactivation issues are commonly encountered.