Esterification of used vegetable oils using the heterogeneous WO3/ZrO2 catalyst for production of biodiesel.

Tungsten oxide zirconia, sulfated zirconia and Amberlyst-15 were examined as a catalyst for a conversion of used vegetable oils (VOs) to fatty acid methyl esters (FAMEs). Among them, tungsten oxide zirconia was a promising heterogeneous catalyst for the production of biodiesel fuels from used VOs because of high activity in the conversion over 93% and no leaching WO(3) in the esterification reaction. The reaction conditions were optimized. A study for optimizing the reaction parameters such as the reaction temperature, stirring speed, WO(3) loading over ZrO(2) and reaction time, was carried out. The catalyst was characterized by BET, XRD, FT-IR, and NH(3)-TPD. With increasing WO(3) loading over ZrO(2), the triclinic phase of WO(3) increased and the tetragonal phase of zirconia was clearly generated. The highest acid strength of 20 wt% tungsten oxide zirconia catalyst was confirmed by NH(3)-TPD analysis and the result was correlated to the highest catalytic activity of the esterification reaction.

Fast biodiesel production with one-phase reaction.

The feasibility of fatty acid methyl ester (FAME) as a co-solvent used to increase the mass transfer between oil and methanol was investigated. FAME, as the co-solvent, does not require additional separation after the reaction because it is the end product of the reaction. To examine intermediate phenomena during the transesterification of soybean oil, the agitation speed was controlled at a slow rate. When the molar ratio of oil to methanol was 1:6 at 0.8 wt.% of KOH to oil, oil was at the bottom layer, and methanol and the catalyst were at the top layer. Under the slow agitation process, the contact surface became initially darkened with the production of FAME and glycerol. After a few minutes, the entire top layer became dark. The top layer, containing methanol, KOH, FAME, and glycerol, fell to the bottom layer and then formed the one-phase system. When 0, 5, and 10 wt.% of FAME to oil was initially introduced to the reaction mixture, the FAME content rapidly increased with the FAME concentration level. After forming the one-phase system, the rate of increase of the FAME content was very slow. The time required for the formation of the one-phase system decreased with the amount of FAME and KOH and with temperature.

Production and characterization of biodiesel from tung oil.

The feasibility of biodiesel production from tung oil was investigated. The esterification reaction of the free fatty acids of tung oil was performed using Amberlyst-15. Optimal molar ratio of methanol to oil was determined to be 7.5:1, and Amberlyst-15 was 20.8 wt% of oil by response surface methodology. Under these reaction conditions, the acid value of tung oil was reduced to 0.72 mg KOH/g. In the range of the molar equivalents of methanol to oil under 5, the esterification was strongly affected by the amount of methanol but not the catalyst. When the molar ratio of methanol to oil was 4.1:1 and Amberlyst-15 was 29.8 wt% of the oil, the acid value decreased to 0.85 mg KOH/g. After the transesterification reaction of pretreated tung oil, the purity of tung biodiesel was 90.2 wt%. The high viscosity of crude tung oil decreased to 9.8mm(2)/s at 40 degrees C. Because of the presence of eleostearic acid, which is a main component of tung oil, the oxidation stability as determined by the Rancimat method was very low, 0.5h, but the cold filter plugging point, -11 degrees C, was good. The distillation process did not improve the fatty acid methyl ester content and the viscosity.

Blending effects of biodiesels on oxidation stability and low temperature flow properties.

To improve the oxidation stability and the low temperature flow properties of a biodiesel mixture, the dependence of the oxidation stability and the cold filter plugging point (CFPP) on the fatty acid compositions was examined. Three different kinds of biodiesels, palm, rapeseed, and soybean biodiesels, were blended with the different weight ratios. The oxidation stability and the CFPP of the blended biodiesels had a close relationship with the compositions of the major fatty acid components. The oxidation stability of the blended biodiesels decreased as the total contents of the linoleic and linolenic acids increased. The correlation was obtained as Y=117.9295/X+2.5905 (0