مسعود مفرحی

Fossil fuels are the most common sources of energy in the world. However, development of industry and technology, increasing demand for energy, reducing fossil fuel reserves (sources) and rising fossil fuel prices led countries to look for alternative fuels. Biofuels are suitable alternative fuels. Bioethanol and biodiesel are the most common biofuels that three is more attention to biodiesl. Commercial prodection of biodiesel was performed by transesterification reaction between triglycride and alcohol (like methanol and ethanol) in the presence of homogeneous (liquid) alkali catalyst. Limits and disadvantages of homogeneous catalysts were leading to synthesis and use of heterogeneous catalysts. In this study, K/SnO2 and K/SnO2-SBA-15, as heterogeneous and supported catalysts were produced and used in biodiesel production by vgetable oils. Supports of catalysts were acidic and were impregnated by alkali metal (potassium). The effect of different parameter like amount of impregnated metal, molar ratio of alcohol to oil, concentration of catalysts, time and temperature of reaction were considered for two catalysts. For K/SnO2 catalyst, molar ratio of K:Sn=2:1, Temperature of 65 °C, molar ratio of 12:1, 3 wt% of catalyst, the reaction time of 1.5 h were determined as the optimum conditions of trans-esterification reaction. The yield of reaction was 97.5% at the optimum conditions. Some properties such as density, viscosity, cetan number and flash point were calculated for produced fuel with this catalyst. The calculated values for these parameters were in accordance with reported standard value. Support of K/SnO2-SBA-15 (SnO2-SBA-15) was synthesis with different method (direct and indirect synthesis) with different molar ratio of K:Sn (K:Sn = 5, 20). The supports were impregnated by different amount of potassium with KOH and K2CO3 as precursor. The efficiency of the catalyst under similar conditions with K/SnO2 catalyst was negligible. Increasing temperature and time