Selective catalytic hydroconversion of organic waster oil to cyclanes over a coal fly ash-derived zeolite-supported nickel catalyst: Waster to energy

• Ni/ZTMS prepared from a coal fly ash proved to be active for the CHC of a waster oil. • More than 95% of the waster oil was converted to cyclanes over Ni/ZTMS at 240 °C. • Three birds with one stone: reducing aromatics, removing HAs, and increasing cyclanes. • The synergism of H⋯H and H + plays crucial role in the CHC of the waster oil to cyclanes. An organic waster oil (OWO) from petroleum processing was extracted with petroleum ether (PE) to PE-extractable portion (PEEP) and extraction residue 1 (ER 1 ), which was extracted with isometric acetone/carbon disulfide mixed solvent (MS) to MS-extractable portion (MSEP) and extraction residue 2 (ER 2 ). A zeolite topology molecular sieve (ZTMS) was prepared from coal fly ash. Ni/ZTMS was prepared by loading Ni into ZTMS. Both PEEP and MSEP were subjected to catalytic hydroconversion (CHC) over Ni/ZTMS in n -hexane under 4 MPa of initial hydrogen pressure (IHP) at 240 °C for 2 h. The results show that most of arenes, hydroarenes, and oxygen-containing organic compounds (OCOCs) and all the nitrogen-containing aromatics (NCAs) in PEEP and all the arenes and NCAs together with most of OCOCs in MSEP were converted to cyclanes. To understand the mechanism for the CHC of PEEP and MSPE from the OWO, 2-phenylphenol (PP) was used as the OWO-related model compound. As a result, PP was completely converted and the yield of target product bicyclohexane (BCH) reached to 97.7% over Ni/ZTMS in n -hexane under 4 MPa of IHP at 240 °C for 2 h. The characterizations of Ni/ZTMS and time profiles of the products from the CHC of PP reveal that Ni/ZTMS can activate H 2 to H⋯H and heterolytically cleave H 2 to relatively mobile H + and immobile H - ; H⋯H addition to benzene ring in PP causes PP hydrogenation, while H + addition to the oxygen in the resulting 2-phenylcyclohexanol (PCH) and 2-cyclohexylcyclohexanol (2-CHCH) induces the dehydroxylation of PCH and CHCH.