Date of Award

1984

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Abstract

Hydrocracking of fluorene was investigated over a nickel loaded Y zeolite in a fixed bed flow reactor using decalin as a donor solvent. This system served as a model for typical commercial donor solvent operations in order to develop a representative kinetic model and propose a reaction mechanism for refining of coal derived liquids. After performing a qualitative investigation, base operating conditions of 661(DEGREES)K, 14.8 bar total pressure, 20 weight percent fluorene in decalin and a hydrogen to hydrocarbon ratio of 42 at a space-time of 4.8 seconds were established for the process. For each experimental series, the variable of interest was adjusted maintaining other conditions constant. Over the range of variables investigated, the effects of space-time and temperature were found to be most significant. No thermal reactions were observed during the study. The effect of hydrogen pressure was studied from 8.2 to 35.8 bar at 661(DEGREES)K, and no significant changes in the reaction occurred. Deactivation and coking were significant and the coke formation was found to be a function of catalyst exposure time. Deactivation was not included in the kinetic model as the route of coke formation was unknown. Two kinetic models were developed using pseudo-homogeneous rate expressions of the chemistry as understood at this time. Rate coefficients were determined by numerical analysis of the experimental data and activation energies estimated. An overall reaction mechanism was proposed taking into account the roles of the donor solvent, catalyst, and hydrogen. It was proposed that decalin transferred hydrogen to fluorene adsorbed on the catalyst in a reactive state. The cis-decalin isomer was highly reactive in isomerization, dehydrogenation, and cracking while trans-decalin was not as reactive. The kinetic model incorporates three routes for cracking of fluorene after partial hydrogenation from decalin; the side ring, the phenyl-methyl bond of the central ring, and both sides of the central ring. Each component, decalin, nickel on the acidic catalyst, and hydrogen were found essential for hydrocracking of fluorene to occur. The product distribution was primarily benzenes, cyclopentanes, and C(,2)-C(,6) hydrocarbon gases.

Pages

450

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