The effect of the metal oxide catalyst in the dimerization of waste vegetable oil was investigated. The high efficiency and recyclability has allowed different metal oxides to be used as catalysts in numerous synthetic reactions. Herein, clay, aluminum, titanium, calcium, magnesium and silicon oxide micro/nanoparticles are used in a Diels-Alder reaction to catalyze the production of the dimer acids. The metal oxides assist the electron transfers during cyclization to produce the desired product. Liquid chromatography mass spectroscopy (LC-MS) and gel permeation chromatography (GPC) were used to verify the production of dimer acids. For the confirmation of cyclization, compounds were analyzed using the nuclear magnetic resonance (NMR) spectroscopy. From the analysis, silylated or pristine clay showed its effectiveness as a catalyst in dimerization. Furthermore, alumina and alumina/silica composite showed successful performance in the reaction to yield cyclic dimer acids. These result suggested that metal oxides and montmorillonite might be used in synthesis of dimer acids for the recycle of waste vegetable oils.

Esterification of soybean oil with methanol was investigated. First of all, liquid-liquid equilibriums for systems of soybean oil and methanol were measured at temperatures ranging from 40 to 65oC. Profiles of conversion of soybean oil with time were determined from the glycerine content in reaction mixtures for the different kinds of catalysts, such as NaOH, CaO, Ca(OH)2, MgO, Mg(OH)2, and Ba(OH)2. The effects of dose of catalyst, cosolvent and reaction temperature on final conversion were examined. Esterification of waste vegetable oil with methanol was investigated and compared to the case of soybean oil. Solubility of methanol in soybean oil was substantially greater than that of soybean oil in methanol. When the esterification reaction of soybean oil was catalyzed by solid catalyst, final conversion was strongly dependent on the alkalinity of the solid catalyst, and increased with the alkalinity of the metal. Hydroxides from the alkali metals were more effective than oxides. When Ca(OH)2 was used for the esterification catalyst, maximum value of final conversion was measured at dose of 4%. When CHCl3 as a cosolvent, was added into the reaction mixture of soybean oil which catalyzed by Ba(OH)2, maximum value of final conversion was appeared at dose of 3%. When waste vegetable oil was catalyzed by NaOH and solid catalysts, high final conversion, over 90%, and fast reaction rate were obtained.