Desulphurization of sour crude oil by sulfur utilizing bacteria through the 4S pathway
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Date
2018
Authors
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Publisher
Universiti Teknologi Malaysia
Abstract
Crude oil is the most highly demanded raw fuel source in a global value chain. Biodesulphurisation (BDS) has a good potential alternative over hydrodesulphurisation, particularly for upgrading and improving sour crude oil with low capital needs. This present study, has successful showed the potential of the eight desulphurising bacteria through the targeting of C-S bond specific cleavage in sulphur removal from dibenzothiophene (DBT) and sour crude oil. These bacteria were isolated using selective enrichment method from three Iraqi sour crude oil samples originated from Al-Ahdb, Al-Basrah and Nieft Kaine while a soil sample from Al-Basrah. Phylogenetic analysis of these bacteria showed that they have 16S rDNA sequences closely related to B.cereus (CHA1, CHA2, CHA4 and SsD1), A. tumefaciens (CBD1), S. maltophilia (CNK1 and SsT2) and R. pusense (SsE3). Desulphurising activity was quantitatively monitored by detecting the amount of 2-hydroxylbiphenyl produced and sulphite SO3-2 as desulphurisation end products using Gibb’s assay and titration method, respectively. S.maltophilia CNK1 showed the greatest desulphurisation and formation rate of 2-HBP rate in comparison with all bacterial cultures. Maximum BDS rate (12 µmol/gDCW h-1) was obtained using DBT in the culture at pH 7.0, added with 5 g/L glucose as carbon source, 0.2% (w/v) casein or malt extract as nitrogen source, incubated with agitation speed (180 rpm) at 30?C. The production of 2-HBP as a result from the C-S cleavage of DBT was confirmed through the depletion of DBT using HPLC analysis. S. maltophilia CNK1 also displayed the greatest sour crude oil desulphurisation activity. Its ability to carry out of the BDS in crude oil was tested in the shake flask and bioreactors cultures. Removal of organic sulphur from crude oil was improved by ~50% in the bioreactor compare to those in the shake flasks. Desulphurisation activity by CNK1 was further enhanced using the stirred tank and airlift reactor with 10% v/v loading of AHD and BSH crude oil, with the total sulphur reduction rate of 47.21% and 52.61%, and GC/FID was detection of organic sulphur removal about (50.20 and 50.20 and 50.20 and 71.84%), respectively
Description
Thesis (PhD. (Biosciences))
Keywords
Petroleum, Petroleum—Sulfur content, Petroleum—Refining—Desulfurization