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), Journal Name: Prepr., Div. Pet. Chem., Am. Chem. Soc.; (United States) Vol. 23:1; ISSN ACPCA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Deep desulfurization of light oil. 3. Effects of solvents on hydrodesulfurization of dibenzothiophene
Hydrodesulfurization of dibenzothiophene in a monolithic catalyst reactor
Related Subjects
020400* -- Petroleum-- Processing
ALLOYS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AROMATICS
BIPHENYL
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COBALT ALLOYS
DESULFURIZATION
ENERGY SOURCES
FOSSIL FUELS
FUELS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROGEN SULFIDES
HYDROGENATION
KINETICS
MOLYBDENUM ALLOYS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PETROLEUM
REACTION KINETICS
SULFIDES
SULFUR COMPOUNDS
THIONAPHTHENES