Mechanism of hydrodesulfurization of dibenzothiophene: a kinetic analysis
Results are presented of a study conducted to develop an understanding of the mechanisms involved in hydrodesulfurization (HDS) of petroleum. Kinetic models were developed which quantify the routes for desulfurization and hydrogenation of dibenzothiophene (DBT). Hydrodesulfurization of dibenzothiophene to biphenyl, cyclohexylbenzene, and H/sub 2/S over a Co--Mo/Al/sub 2/O/sub 3/ catalyst fits a kinetic model which is included in the text. The model accounts for the observation by Rollman that the production of cyclohexylbenzene (CHB) increases with temperature. The proposed mechanism also accounts for the product distribution reported by Bartsch and Tanielian who found only H/sub 2/S and biphenyl (BiPh) at atmospheric pressure. The model predicts a product ratio, (CHB)/(BiPh), of 0.09 at 325/sup 0/C and 3.1 MPa and a ratio of 0.005 atmospheric pressure. The rate for DBT disappearance is described best by an included Langmuir--Hinshelwood expression. This expression becomes first order with respect to DBT as its concentration decreases. This accounts for the first order dependence observed by Houalla, et al. at the low DBT concentration they studied. The rate expression implies that the surface reaction involves two sites on the catalyst surface, one site on which DBT and products competively adsorb and a second site for H/sub 2/ adsorption. This concept of two sites is further established by studies in which the addition of H/sub 2/S decreased the rate of conversion but did not affect product selectivity. The competitive adsorption by more than one reaction product can be deduced from the ratio of absorption coefficients KDBT/K products which indicates that more than one product contributes to K products. The kinetic models developed to account for product selectivity and rate of DBT disappearance support the reaction mechanisms proposed in an earlier paper on the chemistry of condensed sulfur heterocyclics.
- Research Organization:
- Exxon Research and Engineering Co., Linden, NJ
- OSTI ID:
- 6870325
- Report Number(s):
- CONF-770814-P2; CONF-780305-P2
- Journal Information:
- Prepr., Div. Pet. Chem., Am. Chem. Soc.; (United States), Vol. 23:1; Conference: American Chemical Society meeting, Chicago, IL, USA, 29 Aug 1977
- Country of Publication:
- United States
- Language:
- English
Similar Records
Deep desulfurization of light oil. 3. Effects of solvents on hydrodesulfurization of dibenzothiophene
Hydrosulfurization of methyl-substituted dibenzothiophenes: Fundamnetal study of routes to deep desulfurization
Related Subjects
DESULFURIZATION
CHEMICAL REACTION KINETICS
HYDROGENATION
THIONAPHTHENES
ALUMINIUM OXIDES
AROMATICS
BIPHENYL
COBALT ALLOYS
HYDROGEN SULFIDES
MOLYBDENUM ALLOYS
PETROLEUM
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
ENERGY SOURCES
FOSSIL FUELS
FUELS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
HYDROGEN COMPOUNDS
KINETICS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SULFIDES
SULFUR COMPOUNDS
020400* - Petroleum- Processing