Biodiesel production by using various vegetable oil and animal fat mixtures

In this study, the biodiesel samples were produced by using the mixtures of vegetable oils (Sunflower and corn oils) and beef tallow. In the experimental studies, the mixtures of vegetable oils and beef tallow at different ratios were transesterified in a batch-wise system with methanol by using sodium hydroxide as catalyst. The effects of temperature, reaction time, amount of catalyst and vegetable oil / beef tallow ratio on biodiesel production were studied. An amount of catalyst ranging from 0.125 to 1 wt. % of oil was used by keeping the molar ratio of 1/6 oil to methanol in all experiments. The experiments were carried out at temperatures between 40-70 °C for different times ranging from 25 to 80 minutes. The biodiesel of sunflower and corn oils, and their mixtures with beef tallow were obtained using the blends containing 0, 5, 10 and 20% of beef tallow in volume basis. All experiments were conducted at a fixed mixing speed of 600 rpm. The biodiesel conversion increased sharply until 0.75 % catalyst amount and slightly between 0.75 % and 1.0 % with increasing reaction time for all feedstocks. Biodiesel conversions increased with increasing temperature from 40 °C to 60 °C., but decreased as temperature increased 70ºC and over. The degree of conversion decreased as the beef tallow content increased in the mixture. The density of biodiesel samples increased with the increase of beef tallow content in vegetable oils and gradually decreased with the increasing of temperature. The values of kinematic viscosity of biodiesel samples decreased with increasing temperature but decreased with the increase of beef tallow content in the vegetable oil. The values of flash point decreased with the increasing beef tallow content in the mixture while the cetane numbers increased with the increasing of beef tallow content in the mixture. The values heat of biodiesel was similar to sunflower oil and beef tallow from which they produced. It was observed from the rheological behavior of biodiesel samples that all biodiesel samples showed Newtonian behavior. The viscosities of biodiesel samples and the predicted results are in very good agreement with experimental results obtained in this study. Key Words: Biodiesel, Transesterification, Vegetable Oil, Animal Fat, Rheology