Abstract: There exists three-phase (diesel oil/bacteria cell/aqueous phase)O/W emulsion after diesel oil biodesulfurization(BDS).For commercial application,the emulsion must be de-emulsified to yield diesel oil after BDS.In fact, this is the last process of BDS.Several de-emulsifiers applicable to this three-phase O/W emulsion,such as several typical water-soluble de-emulsifiers, methanol, ethanol, and the Rhodococcus sp. pellets which can desulfurize diesel oil were tested.Ethanol was the best, and the de-emulsification mechanism with different de-emulsifiers was discussed. 4% ethanol, as a de-emulsifier could separate oil by centrifuge because of its strong surfactivity, high hydrophilic property and appropriate density.The diesel oil recovery could be increased by centrifugal separation from 60% to almost 100%.GC-MS analysis showed ethanol addition for de-emulsification did not affect the composition of alkenes.It was also noted that the pellets of DS-3 centrifuged showed the same growth rate and dibenthiophene desulfurization activity as the original bacteria, so they could be re-used as desulfurization biocatalyst.

Key words: 柴油, 乙醇, 生物脱硫, 乳状液, 破乳

摘要： 柴油生物脱硫(BDS)反应后往往会产生稳定的O/W型三相（柴油/发酵液/菌体）乳状液，为了满足工业应用的需要，就必须将三相乳状液进行破乳，从而获得BDS反应后的柴油.分析了几种破乳剂对BDS后三相乳状液的破乳效果及破乳机理，发现几种典型的水溶性破乳剂、醇类甚至用于BDS的红球菌自身都具有良好的破乳活性，其中具有强表面活性、强亲水性和合适的密度的乙醇与离心操作相结合的方法最适宜该乳状液的破乳，破乳后离心分离的菌体与原菌具有相近的脱硫活性，可用于再次脱硫. 同时探索了乙醇作为破乳剂的最佳条件，向三相乳状液中加入4％的工业乙醇，并借助4000 r•min^-1离心力的作用可使破乳率达到97.8％.GC-MS实验证实乙醇破乳不影响油品的热值.

关键词: 柴油, 乙醇, 生物脱硫, 乳状液, 破乳