Effectively Hydroconversion of Heteroatom-Containing Organic Species from the Extraction of Low-Temperature Coal Tar to Cycloalkanes Over a Y/Beta Composite Zeolite Supported Nickel Nanoparticles

Abstract

The preparation of high activity bifunctional catalysts, especially hierarchical porous zeolite-supported metal catalysts, are of great important for efficient converting the heteroatom-containing organic species to high quality clean fuels. An excellent performance Y/Beta composite zeolite (YBCZ) supported highly disperse Ni nanoparticles (NNPs, 10% Ni loading) was prepared by modifying deposition-precipitation method (MDPM). Low-temperature coal tar (LTCT) was efficiently and successively extracted with petroleum ether (PE), methanol, and carbon disulfide (CDS) at room temperature under ultrasonic irradiation to obtained the CDS extractable portion (EP_CDS) in a high yield (20.1%). According to the analysis with a GC/MS, the organic species in EP_CDS are mainly chain alkanes (CAs, 4.0%), oxygen-containing organic compounds (OCOCs, 56.0%), arenes (35.3%), nitrogen-COCs (NCOCs, 3.3%), and sulfur-COCs (SCOCs, 1.4%), subjected to catalytic hydroconversion (CHC) over Ni_10%/YBCZ at 160 o C for 18 h under 5 MPa of initial hydrogen pressure (IHP) to obtain EP_CHC. The results show that all organic species in EP_CDS were completely converted to CAs (9.0%), cycloalkanes (70.8%), and hydroarenes (20.2%). In Ni_10%/YBCZ, hierarchical porous zeolite-zeolite composite with strong Lewis acid sites in its crystal texture and highly dispersed NNPs play significant roles in removing heteroatoms (HAs) and saturating aromatic rings (ARs). Oxydibenzene (ODB), a model compound with >C_ar-O bridge bond and AR, was used to investigate the catalytic activity of Ni 10% /YBCZ. ODB was completely and efficiently converted to cyclohexane, bicyclohexane, and tercyclohexane over Ni_10%/YBCZ in n -pentane at 160^oC for 2 h under 5 MPa of IHP, indicating that Ni_10%/YBCZ has excellent activity in CHC process under mild conditions.

Keywords: Low-temperature coal tar, Heteroatom-containing organic species, Ni10%/YBCZ, Efficiently hydroconversion, Cycloalkanes