Identification of Desulfurization Products in the Photochemical Desulfurization Process for Benzothiophenes and Dibenzothiophenes from Light Oil Using an Organic Two-Phase Extraction System

Abstract

The desulfurization products of benzothiophenes (BTs) and dibenzothiophenes (DBTs), produced during a new photochemical desulfurization process, employing an organic two-phase liquidliquid extraction system, have been identified. The acidic products were converted to their corresponding methyl esters by reaction with diazomethane and were then analyzed. In acetonitrile, BT is converted first to benzothiophene-2,3-dione, followed by hydrolysis, loss of carbon monoxide, and oxidation of the sulfur atom, to be converted finally to 2-sulfobenzoic acid. 3-Methyl BT and 2,3-dimethyl BT produce 2-sulfobenzoic acid and two other products, benzenesulfonic acid and 2-acetylbenzenesulfonic acid. DBT is first photooxidized to DBT sulfoxide, which is then further oxidized to form DBT sulfone or dibenz[c,e][1,2]oxathiin-6-oxide. The latter is then oxidized and finally converted to 2-sulfobenzoic acid via dibenz[c,e][1,2]oxathiin-6,6-dioxide. Benzothiophene-2,3-dicarboxylic acid is likely to be formed directly by the oxidation of DBT by a singlet oxygen, generated by photosensitization with DBT sulfone. 4-Methyl DBT and 4,6-dimethyl DBT finally produce the corresponding sulfobenzoic acid, dicarboxylic acid, and sulfone. The yields of these products are seriously affected by the presence of methyl substituents.

Photooxidation of dibenzothiophene on TiO2/hectorite thin films layered catalyst

“…This necessitates the development of improved techniques for the removal of DBT from gasoline and diesel fuels. Recently, a number of researchers have investigated the use of photooxidation to remove DBT and other heterocyclic sulfur compounds from both aqueous and organic solutions [4][5][6][7][8][9][10][11]. Most of these investigations have taken place in the presence of water.…”

Photocatalytic Desulfurization of Waste Tire Pyrolysis Oil

“…Moreover, the new signals at 18.9 and 28.6 min were found in the oxidized pyrolysis oil after isolating by using distilled water (Figure 6b). These might be the remaining oxidized sulfur compounds generated from the photo-oxidation of benzothiophenes or dibenzothiophenes which their larger molecules showed GC-FPD signals at longer elution time [10,18,41]. To monitor the conversion of the sulfurous compounds by photoirradiation, the oxidized waste tire pyrolysis oil obtained from the photocatalytic desulfurization in the presence of acetonitrile for 7 h was subjected to HPLC separation (monitored at 245 nm wavelength) before washing with distilled water.…”

“…Since the major components in tires are natural and synthetic rubbers, both having long hydrocarbon chains, waste tires have higher heating value (39.1 MJ/kg) [5] compared to waste biomass, such as palm (18)(19)(20) MJ/kg) [6] or rice husk (15 MJ/kg) [7]. Thus, waste tires have a high potential for use as a supplemental energy resource aimed at partially or totally replacing conventional fossil fuels.…”

“…Then, the higher polarity oxidized products are extracted by exposure to a polar solvent-extracting phase. The application of photocatalysis for deep desulfurization to successfully remove thiophenes and derivatives of benzo-thiophene and dibenzothiophene, which are the models of sulfur compounds in gasoline [16], light oil [17,18] and diesel [19], respectively, has been reported in previous literatures. The results indicated that the photodesulfurization had more reactivity than the conventional HDS to decompose steric dibenzothiophene derivatives such as 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) [17].…”

PREPARATION AND CHARACTERIZATION OF Cu-Fe/TiO2 PHOTOCATALYST FOR VISIBLE LIGHT DEEP DESULFURIZATION

“…Moreover, TiO 2 is inert to chemical corrosion, has a strong oxidizing power (with UV light) and is cost effective [17]. The successful application of photocatalysis in deep desulfurization process has been reported previously to remove thiophenes and derivatives of benzothiophene (BT) and DBT, which are the model sulfur species in gasoline [18,19], light oil [14,20] and diesel [21]. The results indicated that photodesulfurization has displayed higher activity compared to the conventional HDS in removing refractory DBT derivatives such as 4-methyldibenzothiophene (4-MDBT) and 4,6-DMDBT [14].…”