Catalyzed By Solid Acid Vegetable Oil Transesterification Preparation Of Biodiesel

The fatty acid methyl ethers can be used as biodiesel, which is a renewable, safe and environmentally friendly energy, and can be synthesized from plant oils in the presence of solid acid. Solid acid catalysts offer several advantages, they are easily separated from the reaction medium, which can be less corrosive and avoid wastewater pollution. The study of novel solid acid catalysts has been more attention in the area of biodiesel production.The solid acid catalysts ZrO₂-SO₄^2- and K₄Zn₄[Fe(CN)₆]₃ were prepared herein. The structures and characteristics of catalysts were identified by XRD, FT-IR, BET and Elemental analysis. The low acid values (soybean oil) and the oil of high acid values (jatropha curcas oil) were used as raw oil. We compared the catalytic activities of the two kinds of solid acid in different acid values of raw oil and different reaction temperature. The detail components of the bio-diesel production were analyzed by GC-MS.The catalyst ZrO₂-SO₄^2- was modified by the anionic dispersant of acrylic acid-styrene sulfonic sodium copolymer, and then appeared a higher specific surface area, a better crystalline structure and high catalytic activity than the catalyst prepared by precipitation method. The anionic dispersant of molecular weight 6068 is the best one. The optimum conditions for the transesterification of soybean oil with methanol were: the temperature of 503K,methanol/oil mole ratio of 20∶1 and catalyst dosage (catalyst/oil) of 2%. The yield of methyl esters reached over 96% after 7 hours by the catalyst ZrO₂-SO₄^2- modified by the anionic dispersant. Being used five times, the catalyst remained its good catalytic activity. Otherwise, The yield of methyl esters reached only 95.5% after 10 hours by the catalyst prepared by precipitation method.When the jatropha curcas oil of high acid value was used as raw oil, the ZrO₂-SO₄^2- lost its catalytic activity. The yield of methyl esters reached only 84% after 10 hours. After it was used five times, the yield of methyl ester declined no more than 73%. Otherwise, K₄Zn₄[Fe(CN)₆]₃ remained its good catalytic activity and stability when the oil had high acidity. The yield of methyl ester was 93% under the conditions of 463K and reaction time 10 h. After it was used five times, the yield of methyl ester still obtained 90%.Both ZrO₂-SO₄^2- and K₄Zn₄[Fe(CN)₆]₃ had good catalytic activity of transesterification. ZrO₂-SO₄^2- had more stability of high temperature and it was suitable for the raw oil of low acid value. When the Fe-Zn was used, the temperature of reaction was lower compare to ZrO₂-SO₄^2-. Fe-Zn remained its good catalytic activity and stability for the high acid value oil. It's strongly suitable for industrialization.