Catalytic upgrading of bio-oils over high alumina zeolites

Catalytic upgrading of bio-oils derived from fast pyrolysis of sunflower stalk, cedar, knotweed and apple tree stem over H-ZSM-5, H-beta and H-USY zeolites with high alumina content was investigated at a reaction temperature of 500 degrees C. All catalysts showed high catalytic activity and selectivity towards aromatic hydrocarbons in the conversions of oxygenated compounds in the bio-oils, and 56.2-100% of aromatic hydrocarbons were found in the upgraded bio-oils which can be detected by GC/MS. Naphthalene was favored to be produced by using H-ZSM-5 while more monocyclic aromatic hydrocarbons such as p-xylene, toluene and alkylbenzene were generated by using H-beta as well as H-USY. Furthermore, all catalysts maintained high activity and selectivity with the maximum aromatic hydrocarbons amount of 70% in the upgraded bio-oils detected in the third cycle. In addition, the spent catalysts were easily regenerated by simple calcination at 650 degrees C for 30 min, and the regenerated catalysts showed almost the same activity as the fresh ones. It is expected that these high alumina zeolites can be widely used in practical bio-oil upgrading processes. (C) 2018 Elsevier Ltd. All rights reserved.