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Biotechnology in the Refinery
Published in Wael Ahmed Ismail, Jonathan Van Hamme, Hydrocarbon Biotechnology, 2023
Nour Sh. El-Gendy, James G. Speight
The desulfurization capability of B. subtilis Wb600 on light crude oil was examined by Nezammahalleh (2015). The Wb600 strain utilized the sulfur-containing compounds of the oil as a source of sulfur without degrading the HC skeleton and produced biosurfactants, which facilitated the transfer of the organic sulfur compounds into the aqueous phase. It decreased the total sulfur content of the light crude oil to about 40% during 35 h with an oil/water ratio of 0.2. Mohamed et al. (2015) reported a 10% reduction in sulfur content of heavy crude oil (with initial S content of 3%) in batch BDS at 30°C and 250 rpm, within 7 days, using resting cells of Rhodococcus sp. strain SA11 collected in the exponential phase of DBT cultures. Moreover, total sulfur and sulfur speciation analyze of the hexane-soluble fraction of the heavy crude oil (i.e., the de-asphaltened oil fraction or the maltenes) revealed 18% total sulfur reduction including a wide range of thiophene derivatives such as DBT, benzothiophene, and their alkylated derivatives. Adlakha et al. (2016) reported a viscosity reduction of 31.28% with 76% BDS of heavy oils in a batch BDS of 1/3 oil/water ratio using growing cells of Gordonia sp. IITR100 at 30°C and 250 rpm, within 7 days. Martínez et al. (2016) reported the enhancement of oil BDS by engineered synthetic bacterial consortia.
Wastewater Treatment
Published in Suresh C. Ameta, Rakshit Ameta, Garima Ameta, Sonochemistry, 2018
Arpita Pandey, Arpita Paliwal, Rakshit Ameta
Crude oil contains numerous aromatic sulphur-containing compounds such as sulphides, thiophenes, benzothiophene, dibenzothiophene (DBT), and their substituted derivatives. During distillation and refining of crude oil, these compounds end up in the gasoline and diesel fractions. Combustion of these compounds in vehicle engines results in the generation of SO2 and particulate matter emission. Growing concerns over air pollution created by these emissions have led to stringent restrictions on the sulphur content of the liquid fuels (Bolla et al., 2014).
Phosphomolybdic acid-based sulfur-containing metal–organic framework as an efficient catalyst for dibenzothiophene oxidative desulfurization
Published in Journal of Sulfur Chemistry, 2022
Haifeng Ji, Shuting Liu, Hongfei Shi, Weidong Wang
With the increasing improvement of international environmental protection regulations, the sulfide content of fuel oil is strictly regulated. International standards in all countries require that the sulfur content of fuel oil products should not be higher than 10 ppmw [1]. With increasingly stringent emission standards for sulfur content in fuel oil, reducing sulfur content in fuel oil has become a common goal for the refining industry. Thiophene sulfur compounds account for more than 70% of the organic sulfur content in oil products, and their main components are benzothiophene (BT), dibenzothiophene (DBT) and their derivatives, which are difficult to remove by hydrodesulfurization due to their inactive chemical properties [2]. Oxidative desulfurization (ODS) is widely regarded as a promising process of deep desulfurization [3–5]. The oxidation process use molecular oxygen (O2) and hydrogen peroxide (H2O2) as oxidants under mild conditions, which can oxidize thiophene compounds in oil and convert them into the corresponding sulfoxide or sulfone products. Meanwhile, the polar sulfoxide and sulfone products are extracted and removed from the oil by polar solvents (CH3CN, DMF). Oxidative desulfurization is simple and easy, with low energy consumption and high efficiency of conversion and desulfurization, so researchers are keen to develop high-efficiency solid catalysts for ODS [6–8].
Variation in cell surface characteristics and extracellular polymeric substances during the biodegradation of monocyclic and heterocyclic aromatic hydrocarbons in single and multi-substrate systems
Published in Environmental Technology, 2018
Akashdeep Singh Oberoi, Ligy Philip
Effect of benzofuran (O-Heterocyclic) and benzothiophene (S-Heterocyclic) on the cell surface characteristics in multi-substrate system with benzene and toluene was investigated. Dual substrate system consisted of mixture of benzofuran with either benzene or toluene (500 mg/L). Substrate degradation and the bacterial growth profile in dual substrate system are shown in Figure 5(a–c). It has been observed that the presence of benzofuran inhibited the degradation of both benzene and toluene, with a pronounced effect on benzene. Complete degradation of benzene (500 mg/L) in individual substrate system occurred in 132 h while in the presence of benzofuran it took 192 h. CSH was 75.1 ± 1.71% and 80.1 ± 1.62% in the presence of benzene and toluene alone, while CSH was reduced to 67.7 ± 1.65% and 70.6 ± 2.47%, respectively, in the presence of benzofuran (Figure 6(a)). These variations could be explained on the basis of EPS secreted by the bacterial cells. In single substrate systems, proteins constituted the major fraction of EPS while in the presence of benzofuran a significant decrease in protein concentration was observed. On the other hand, carbohydrate concentration increased for toluene from 8.84 to 35.95 mg/g for benzofuran–toluene system as shown in Figure 6(b). A decrease in CSH serves as a defense mechanism resulting in the repulsion between outer cell surface and hydrophobic compounds, thereby resulting in a slower diffusion of these compounds into the cell membrane [46,47]. The decrease in the CSH might have resulted in slower degradation of benzene and toluene. There was a distinct increase in the total EPS concentration of 35.02% and 35.29% in benzofuran–toluene and benzofuran–benzene systems, respectively. An increase in EPS concentration did not favor for enhanced degradation of the hydrophobic hydrocarbons. A similar variation in cell surface characteristics and degradation was observed in dual substrate systems involving benzene or toluene with benzothiophene. The total increase in EPS content was more in benzothiophene containing systems (Figure 6(b)). Results from the present study clearly indicate that variation in cell surface characteristics is dependent not only on the initial pollutant concentration and hydrophobicity but also on the toxicity of pollutants. Toxicity of benzothiophene and benzofuran even at very low concentration are indicative from their EC50 values (<3.5 mg/L) reported in several studies described above [29]. Thus, there is a possibility that interaction between benzothiophene/benzofuran and MAHs could result in enhanced toxicity allowing the bacterial cells to alter their cell surface characteristics by modifying the protein/carbohydrate ratio resulting in either an increase or a decrease in CSH and CSC.