Preparation Of Biodiesel And Bioconversion Of The By-producing Glycerol

Biodiesel, an alternative diesel fuel, is made from renewable biological resourse such as vegetable oils, animal fats, and microbial lipid. 1,3-Propanediol (1,3-PD) is a valuable chemical intermediate that is potentially used as a monomer to produce polyesters, polyethers and polyurethanes. Bioconversion of glycerol to 1,3-PD is adopted in producing 1,3-PD nowsdays.In this paper, several kinds of catalysts for preparing of biodiesel were studied, and the parameters of processes of using different catalysts were compared. The two-step method was proposed: the first step was an esterification of waster cooking oil (WCO) catalyzed by FeCl₃, and the second step was catalyzed by alkali. The optimal conditions of the first step were as follows: 2 % of FeCl₃ (wt %), 11:1 of methanol to WCO (mol/mol) and 5 h of reaction time. In the second step, 1 % of KOH (wt %), 6:1 of methanol to WCO (mol/mol) and 1h of reaction time were adopted. The yield of biodiesel obtained was 93.6%, while the traditional acidic-catalyzed and Fe₂ (SO₄)₃ method were 43% and 86%, respectively. This two-step method had the advantages of high yield, recycling catalysts easily, few waste and so on.An enzyme membrane reactor that immobilized free lipase in the space of fiber was used to prepare biodiesel. After 36h reaction the content of biodiesel was 30.8%. Because of the high viscosity of oil, most fibres were adhesive; the contacting area between reactants and lipase was greatly decreased in this case. Another reason for low transesterification was the agglomeration of the lipase in fibres. Further research should be done to resolve these problems.The bioconversion of biodiesel-based crude glycerol into 1, 3-propanediol by Klebsiella pneumoniae (CGMCC 2028) was studied in batch, fed-batch and continous fermentations under microaerobic conditions. Experimental results showed that the cells could grow well when crude glycerol as sole carbon source. The biomass was increased when enhancing flow rate of air, while the concentration of 1, 3-propanediol was decreased. The rate of aerating air was maintained at 0.1vvm before the log phase of growth and decreased to 0.01vvm later, the final concentration of 1, 3-propanediol was 59.2g/L, and the molar yield was 45%. The cost analysis demonstrated that crude glycerol from biodiesel production was cheaper for industrial production of 1, 3-propanediol than refined glycerol. In continous fermentation, when the concentraton of glycerol in feed medium was 80g/L, the concentration of 1, 3-PD reached 22-28g/L. The phenomenon that Klebsiella pneumoniae was inhibited by the produces of fermentation was studied. The experimental results showed that the concentration of 3-Hydroxypropionaldehyde was high. 3-HPA is an intermediate, which is poisonous to the cell growth; it can be translated by 1, 3-propanediol oxidoreductase (PDOR). It can be deduced that the activity of PDOR was inactived or the amount of PROD was decreased.