Abstract
Biodiesel produced by the transesterification of vegetable oils (sunflower oil) with methanol is a promising alternative fuel to diesel because of the limited resources of fossil fuel and environmental concerns. A base or acid catalyst is usually used to improve the reaction rate and yield. In this work, comparative studies on homogeneous (NaOH) and heterogeneous (CaO based) catalysts were undertaken at the same reaction conditions (1% catalyst dosage, oil/methanol mole ratio = 1/9, 333K water bath). It was found that the NaOH took a shorter time to achieve 95% oil conversion than CaO based catalysts. However, CaO-based catalysts could replace such conventional homogeneous catalysts, because they are reusable and inexpensive. However, Ca2+ leaching from the catalyst was detected. Carbon was introduced as the CaO catalyst support and this gave a significant reduction in the Ca2+ ions released to biodiesel. In the methanolysis of sunflower oil with NaOH and CaO-based catalysts, reaction orders and activation energies were also assessed. In addition, a microwave heating method was considered. Results show that microwave heating fails for CaO- based catalysts, but does work for the NaOH (which takes <1 min) to give 95% conversion (when 1% catalyst dosage, oil/methanol mole ratio = 1/9). Microemulsions may be considered as alternative fliels that achieve better fuel economy and lower pollutant emissions. Hence, the essential features of water-in-diesel (D)/biodiesel (BD) microemulsions systems have been considered with varying level of surfactant (S), cosurfactant (COS), S/COS ratio, D/(S+COS) ratio and H2O concentration. The physicochemical properties of the various W/D(BD) microemulsion have been examined (i.e. viscosity, conductivity and droplet size). The engine performance and engine emission (CO, NO, HC and particulate matters) characteristics between these prepared fuels (D, D/BD blends, W/D and W/D(BD) microemulsions) were measured and compared. Results presented show that the microemulsion fuels give lower levels of emission of NO, HC and particulates that represent an environmental and health hazard, and lower fuel consumption (due to better burning efficiency) but an increased level of CO emissions (because of the "microexplosions"). On the other hand D/BD blends produced lower concentrations of the HC, particles and CO in the exhaust than neat diesel. However, the fuel consumptions and NOx emissions of blend fuels performed a little higher than diesel fuel operation. Cerium (Ce) fuel-borne (FBC) and water-borne (WBC) catalyst have been introduced as an alternative way to reduce diesel emission particulates (DEPs). The effect of and mode of action of FBCs and WBCs for DEPs structure have been evaluated by EELS, diffraction, TEM and SEM. The rate of DEP oxidation was studied by DSC and TGA, where results indicated that the oxidation activation energy did not change but the oxidation temperature (the temperature for the reaction of carbon with oxygen) was lowered with Ce dosing.