| Combustion of petroleum leads to the release of toxic sulfur dioxides into the environment, contributing significantly to air pollution and being the principal cause of acid rain, so crude oil needs to undergo desulfurization. Hydrodesulfurization (HDS), a chemical method, is a high pressure and high temperature catalytic process that uses hydrogen gas to reduce the sulfur in petroleum fractions to hydrogen sulfide. Hydrodesulfurization units are expensive to construct and to operate. In addition, the same processes do not work on organosulfur. On the other hand, biocatalytic progresses are cheap, operate under mild condition, and are endowed with high selectivity. There has been a considerable effort to develop petroleum desulfurization using bioprogresses. This makes biodesulfurization (BDS) an alternative means in place of HDS for petroleum desulfurization.We do some research on Rhodococcus strain lawq which has specific degradation ability of dibenzothiophene (DBT) in field of ferment, desulfurization of resting cells and immobilized cells.The best growing conditions of strain lawq are 33℃, pH7 (at beginning), 48-hour ferment. It was shown the ferment of strain lawq could be influenced by dissolved oxygen. The optical ferment medium and growing conditions for strain lawq in shaking flask were determined. The best carbon source, nitrogen source and sulfur source are glycerol, ammonium chloride and DBT, respectively by 2g/L, 2g/L and 0.2mmol/L. There were no distinct effects on growth and ability of desulfurization of strain lawq, when we added surfactants, amino acid and vitamin into ferment medium. Using the resting cell to desulfur is the major way of biodesulfurization in the world. Firstly, we research on biodesulfurization of simulant system (DBT dissolve in water and ethanol). The best reaction conditions of desulfurization of simulant system were determined. The optical cell concentration, reactant concentration, reaction temperature, pH and reaction time are 25 (A620), below 5mmol/L, 30℃,7.0 and 4h,respectively, in shaking flask. Under the best conditions, the ratio of desulfurization could reach 40%. Secondly, we studied the biodesulfurization of gasoline and diesel oil provided by Yangzi company. The conditions of gasoline desulfurization is as follows: the cell condition is 35 (A620), the ratio of water to gasoline is 8, the rotate speed is 200r/min, the reaction time is 32h. Under the conditions, the ratio of desulfurization could reach 53%. The conditions of diesel oil desulfurization is as follows: the cell condition is 35 (A620), the ratio of water to diesel oil is 9, the rotate speed is 250r/min, the reaction time is 40h. Under the conditions, the ratio of desulfurization could reach 48%.The technology of immobilizing cells is one of the new technology in bioengineering. We do some elementary research on biodesulfurization of simulant system and oil system. Firstly, we studied the capability of immobilized cells with the different carriers, and we confirmed the sodium alginate as the carrier. The best conditions of immobilization are as follows: the concentration of sodium alginate is 2%, the concentration of calcium chloride is 2%, the quantity of cell is 10%. Secondly, we studied the desulfurization of simulant system and oil system. The immobilized cell have longer reaction time and lower sensitive of temperature and pH compared with the resting cell in shaking flask of simulant system. We studied the desulfurization in the FBR. It shown that there is no distinct effect of the velocity of flow on biodesulfurization, however, the aerate influence the performance of desulfurization greatly in the FBR. The best conditions of desulfurization of simulant system in FBR is as follows: the temperature is 35℃, pH is 7, the reaction time is 48h, the quantity of immobilized cell is 50g, the volume of solution is 150ml, the reactant concentration is below 5mmol/L, the aerate is 60ml/min. Under the condition, the ratio of desulfurization could reach 30%. Using the immobilized cell t...
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