| Summary: | Removal of polynuclear aromatics from diesel fuel has become a focus of intense
research due to the stringent environmental legislation associated with clean fuels. In this
work, selective ring opening of model compound decalin over the set of catalysts
comprising of 1) Ir-Pt supported on mesoporous Zr-MCM-41, large and medium pore
zeolites like HY and H-Beta and 2) Ni-Mo/carbide on HY, H-Beta, Al-SBA-15, ¥ã-
alumina and silica alumina were studied. All the catalysts were extensively characterized
by BET surface area measurement, CO-chemisorption, XRD, FTIR, TPR and TPD of
ammonia. Ring opening of decalin was studied on these catalysts in a trickle-bed reactor
in a temperature range of 200- 400 ¡ÆC, pressure range of 2-7 MPa and LHSV of 1 to 3 h-
1. 31.7 and 65.0 wt.% of RO yield and selectivity were observed on Ir-Pt/HY catalyst at
220 ¡ÆC, whereas 34.0 and 40.0 wt.% of ring opening yield and selectivity were observed
on Ni-Mo carbide/HY catalyst at 240 ¡ÆC. From the model compound studies, Ir-Pt/HY,
Ni-Mo carbide/HY and Ni-Mo carbide/H-Beta were selected for study of hydrotreated
light gas oil in a trickle bed reactor. Ni-Mo carbide/HY performed better over other
catalysts and increased the cetane index of hydrotreated light gas oil by 12 units at 325
¡ÆC. A first order kinetic model was fitted for the hydrotreated light gas oil study. 89, 111
and 42 KJ/gmol of activation energies was observed for dearomatization, aromatization
and naphthenes cracking steps, respectively. The thermodynamic equilibrium calculations
reveal that the selectivity of ring opening products of decalin can be maximized by
favoring the formation of unsaturated compounds at higher operating temperatures.
Energetics of dealkylation and ring opening reactions of naphthenes in gas phase and on
the surface of Br©ªnsted acid sites were calculated using quantum chemical simulations. In
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gas phase, ratio of Arrhenius activation energies for forward and reverse reactions of RO
and dealkylation reactions are 1.92 and 1.82 respectively. Deakylation on different level
clusters revealed that surface reaction is the rate controlling.
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