Mechanism And Kinetics Of Biodesulfurization Of Model Diesel Oil

Biodesulfurization (BDS) is an environmental friendly method that can remove sulfur from refractory organic compounds under ambient temperature and pressure without lowering the calorific value of the fuel and it can be potentially used in industrial desulfurization. Recently, BDS research focus on some aspect such as:the desulfurization microbial isolation; desulfurization pathway and mechanism; genetic research; desulfurization range of enzyme; enhancement of desulfurization rate and bioreactor design. In this dissertation, a desulfurization pathway of Mycobacterium sp. ZD-19 was found; the effect of final production on biodesulfurization was investigated; a method for enhancement of desulfurization rate was found; the kinetic model was established based on competitive inhibition about the desulfurization of different substrace coexistence. The main original conclusions of this dissertation are:1) A metabolic pathway for the biodesulfurization of model organosulfur compounds e.g., dibenzothiophene (DBT), is proposed. This pathway, defined as extended 4S pathway, incorporates the traditional 4S pathway with the methoxylation pathway from 2-hydroxybiphenyl (HBP) to 2-methoxybiphenyl (2-MBP). Some portion of 2-HBP is used by ZD-19 as carbon source for methoxylation. ZD-19 has ability to desulfurize DBT,4-MDBT and 4,6-DMDBT.2) The product of DBT desulfurization,2-HBP and 2-MBP have inhibition effect on cell growth and desulfurization. Meanwhile, compared with 2-HBP,2-MBP which is the end product of extended 4S pathway, has much slighter inhibition effect on the cell growth and desulfurization activity. Thus, the new pathway with 2-MBP as the end product may be an alternative for the further desulfuration of the fossil fuels.3) Nonionic surfactant Tween-80,nature surfactant soya lecithin (SL) supermolecular receptorsβ-cyclodextrin (β-CD) and ionic liquid (IL) [EMIM][BF4] are investigated and found enhancement effent on the biodesulfurization. In addition ofβ-CD could almost counteract the inhibition of 2-HBP at low concentration on cell desulfurization. 4) When DBT,4-MDBT and 4,6-DMDBT are mixed in two or three at the average concentration, there is competitive inhibition existence in biodesulfurization.5) Based on competitive inhibition theory, the kinetic model about Cx-DBTs coexistence desulfurization was established. The results showed that:prediction model could better reflect the actual desulfurization rate; the model predicted values was in good agreement with experimental values.