High-value monocyclic aromatic hydrocarbons produced by a catalytic pyrolysis of oil shale

Abstract

The expeditious exhaustion of conventional fossil resources of limited reserves strongly calls for new routes for the manufacture of monoaromatic hydrocarbons (MAHs), especially methyl-benzenes such as benzene, toluene, xylene (BTX), which are amongst the top 15 commodity petrochemicals and account for 30% of petrochemical products. Taking sulfated γ-alumina catalyst as a proof-of-concept example, we herein report our efforts via a catalyst-assisted pyrolysis of oil shale (OS), which is strategic unconventional fossil resources of huge reserves. We find that upon introduction of sulfated γ-alumina into OS pyrolyses, the MAHs proportion in the as-produced petroleum-like fuels (PLFs) increases by 275.0%, where the content of methyl-benzenes, BTX and xylene increases by 232.1%, 443.8% and 1220.0%, respectively. Besides, the catalyst could promote evident improvements in pyrolyzates quality, where the respective content of heteroatomic compounds and hydrocarbons displays 31.5% decrease and 51.2% increase, and the respective proportion of short-chain and long-chain hydrocarbons exhibits 82.4% rise and 81.0% drop. Moreover, the content of pyrroles and thiophenes, which are usually undesired species for PLFs, but are valuable heterocyclic aromatics widely used as feedstocks in numerous important industrial/scientific fields, is enriched by 253.8% and 75.9%, respectively. It is unveiled that the concentration and strength of the Brønsted acids of our sulfated γ-alumina are respectively larger and stronger than those of its Lewis acids such that their collaborate-competition actions confer it with fascinating catalytic attributes. Our work likely launches new opportunities for manufacturing MAHs, and it might provide guidance for designing sophisticated catalyst of much more satisfactory performances.