Deep Hydrodesulfurization of Light Gas Oil. 1. Kinetics and Mechanisms of Dibenzothiophene Hydrodesulfurization

Abstract

Hydrodesulfurization (HDS) of light gas oil was investigated using sulfided Co-Mo/Al 2 O 3 catalyst. The behavior of dibenzothiophene, monomethyldibenzothiophenes (C1-DBTs) and dimethyldibenzothiophenes (C2-DBTs) in HDS was traced under the following conditions: temperature, 280-400 °C; LHSV, 2-10 h -1 ; and gas/oil, 1000 and 125 NL (L-(NTP))/L. The HDS of these compounds was treated as a pseudo-first-order reaction. The ratio of the rate constants of 4-methyldibenzothiophene (4-MDBT) and DBT to that of 4,6-dimethyldibenzothiophene (4,6-DMDBT) diminished relative to those of the model reactions. The activation energies of DBTs increased in the order DBT < 4-MDBT < 4,6-DMDBT, while the differences between values diminished relative to those of HDS reactions using a single component among DBT, 4-MDBT, and 4,6-DMDBT. The retarding effect of H 2 S on HDS decreased in the order DBT > 4-MDBT, and further, 4,6-DMDBT was not inhibited. The results indicated that the selectivity for biphenyls in the HDS of DBT was higher than in the HDS of 4-MDBT or 4,6-DMDBT and that DBT and 4-MDBT were adsorbed by the catalyst more weakly than 4,6-DMDBT. An aromatic hydrocarbon of larger ring number has a stronger retarding effect on the HDS rate. The addition of phenanthrene decreased the HDS rate of DBTs in the order DBT > 4-MDBT > 4,6-DMDBT, while 1-methylnaphthalene did not affect the HDS rate. The effect of phenanthrene on the HDS rate appeared to be related to the differences in the adsorption ability of DBTs. To the contrary, the addition of acridine decreased HDS rate in the order 4,6-DMDBT > 4-MDBT > DBT. The results indicate that the retarding effect of acridine is different from that of phenanthrene.

Genotypic Characterization of Sulfur-Oxidative Desulfurizing Bacterial Strains Isolated from Mexican Refineries

“…To reduce these emissions, the total sulfur content in fuels is reduced during refining of middle-distillate fractions such as diesel oil [1]. However, some sulfurcontaining compounds are recalcitrant to the thermochemical hydrodesulfurization (HDS) process presently used in refineries for the removal of sulfur [2]. These compounds mainly consist of DBT and its substituted derivatives and may represent 70% of the sulfur in some crude oils; they are particularly concentrated in the fractions used to produce diesel oil [3].…”

Crystal Structure and Desulfurization Mechanism of 2′-Hydroxybiphenyl-2-sulfinic Acid Desulfinase

“…To alleviate these problems, efforts are being made to limit the sulfur content in diesel and gasoline fuel. Inorganic or nonaromatic organic sulfur compounds can easily be removed from fossil fuels by the conventional metal-catalyzed hydrodesulfurization method (2), but it is difficult to remove polycyclic aromatic sulfur compounds such as benzothiophene and dibenzothiophene (DBT) 2 (3). In particular, DBT is considered as a model compound of polycyclic organic sulfur compounds in fossil fuels, and degradation of DBT by microbial activities has been studied with a keen interest in biodesulfurization (4,5).…”

Protocols for the Isolation and Preliminary Characterization of Bacteria for Biodesulfurization and Biodenitrogenation of Petroleum-Derived Fuels

“…Dibenzothiophene (DBT) and DBT with alkyl substituents in the 4-and 6-position flanking the sulfur atom ( Fig. 1) are more resistant to the HDS treatment than mercaptans and sulfides [3]. DBT is the model compound of polyaromatic sulfur heterocyclic compounds.…”