عنوان مقاله [English]
Due to a huge increase in world energy consumption, the limited traditional fossil energy resources, and increased environmental concerns, a requirement for alternative energy sources has been paid great attention in recent years. Biodiesel is known as a nontoxic, renewable and environmental-friendly biodegradable fuel that is free from sulfur and aromatic compounds. The biodiesel production by transesterification of vegetable oils has the potential to solve the above problems and concerns. Nanocatalysts are considered as important material in chemical processes, energy production and energy savings, and prevent environmental pollution. In this study, the characteristics and performance of TiO2 nanoparticles (TNPs) and one commonly used catalyst for
alkaline-catalyzed transesterification, i.e., sodium hydroxide, were evaluated using waste olive oil. The present method affords nontoxic and non-corrosive medium, high yield of biodiesel, clean reaction and simple experimental and isolation procedures. The catalyst can be recycled by simple filtration and reused without any significant reduction in its activity. The process variables
that influence the transesterification of triglycerides, such as volume ratio of methanol to waste olive oil, type and loading of catalyst, reaction time and reaction temperature, were investigated. High catalysis activity and a much more specific surface TNPs were found to be more superior to sodium hydroxide under the same conditions. The results showed that TNPs as catalyst can improve the biodiesel production up to 87.8\% in the same condition in which the efficiency is 76.4\% for sodium hydroxide as a homogeneous catalyst. The effect of biodiesel/diesel blend fuels on engine exhaust emissions in a Robin engine was evaluated. The testing results show that the B20 blend fuel (including 20\% and 80\% v/v biodiesel and diesel fuel, respectively) reduced (HC) and carbon monoxide (CO) emissions to 28.9 and 20.6\% compared to the petroleum diesel fuel, respectively. In addition, in this study, the effective use of biodiesel to reduce air pollutant emissions was approved, although a slight increase in
nitrogen oxides emissions than pure diesel fuel was observed that quite what was expected due to increasing combustion temperature.