Lipase-Catalyzed Synthesis Of Lubricant Base Oils

Lubricant is composed of base oil and additives. Quality of lubricant is determined by base oil. Environment friendly lubricants are including vegetable oil and synthetic esters. Because of vegetable oil has many disadvantages, synthetic esters draw attention. Synthetic esters such as dibasic acid esters and polyolesters show attractions due to their applications in lubricants. These favourable ecological properties together with their well established technical performance recommend them as suitable base oils for the lubricant products. The traditional production of lubricant base oil uses acid and alcohol with the catalyst of oil of vitriol or alkali under relatively severe conditions, which have many problems, for example, many side-products and high energy consumption. As esterification catalysts, enzymes have several characteristic features when compared with conventional chemical catalysts with respect to high catalytic activity, lack of undesirable side reactions and operation under mild conditions. The high selectivity of biocatalyst is useful for reducing side reactions, leading to easier separation. In addition to their easier separation, enzymes are attractive for commercial applications because of their ability to operate under the mild conditions of ambient temperature and pressure. These advantages are favorable for the establishment green chemistry.In this paper, synthesis of dibasic acid esters in solvent-free system or using product as solvent, by immobilized lipase from Candida sp.99-125were studied.In solvent-free system, the conditions of enzymatic synthesis of ethylhexyl sebacate were optimized with98.8%esterification degree acheived. Using product as solvent, the conditions of enzymatic synthesis of bis(2-ethylhexyl) sebacate were optimized with77.83%esterification degree acheived.5L membrane reactor for synthesis of bis(2-ethylhexyl) sebacate was designed and a scale-up reaction was studied. The esterification degree was97.6%in batch reactor. The reuse study showed that the enzyme can be used at least thirty times in batch reactor without significant loss in its activity. The end product bis(2-ethylhexyl) sebacate was obtained after purification with purity of98.7%and the recovery of90.8%. Acid value of the product was0.046mg/KOH. The dibasic acid esters produced did not have pollution and the determined tribological, physico-chemical properties of the lubricant proved that it was an environmental friendly product, suitable even for special lubrication processes, such as the low temperature.In this paper, synthesis of polyolesters by immobilized lipase from Candida sp.99-125in solvent system was also studied. Setting trimethylol propane caprylic acid ester as an example, the influences of the molar ratio of substrates, reaction temperature, the amount of immobilized lipase and reaction time on the reaction were also investigated. Under the optimal condition, esterification degree of trimethylol propane and caprylic acid was89.8%.