Comparison of physicochemical and performance properties of biodiesel fuel based on methanol and bioalcohols

Abstract

Biodiesel fuel has a number of advantages over traditional diesel fuel, among the most important of which are the bio-renewability of oil feedstock, rapid biological degradation, non-toxicity, compatibility with petroleum diesel fuel. Despite a significant amount of literary sources related to biodiesel, today there is practically no systematic data on influence of characteristics of the raw material composition on the properties of the fuel. Methanol remains the traditional alcohol for biodiesel fuel production, although the use of bio-alcohols – ethanol and butanol – would make the raw materials completely bio-renewable. Therefore, the purpose of the work was to analyze the literature data and to reveal the peculiarities of influence of nature of the raw-stuff for biodiesel production, namely the length of the hydrocarbon chain of alcohol and the fatty acid composition of the oil component, on physicochemical (density, viscosity) and performance (low-temperature properties, oxidative stability, cetane number, power and environmental performance of the diesel engine) properties of the fuel produced. The requirements of modern standards for mineral diesel and biodiesel fuel have been analyzed. Based on the analysis of literature data, it has been established that with an increase of alcohol molecular weight in the methanol-butanol series, there is a slight increase in the kinematic viscosity of the resulting fatty acid esters. The values for butyl esters are at the upper limit allowed by the standards, while the density of biodiesel fuel declines with increase of hydrocarbon chain of alcohol. The temperature of cloudiness and freezing also declines. The values of the cetane number are more dependent on the length of carbon chain of the fatty acid, and not alcohol. They grow in proportion to the increase in molecular weight of fatty acids and to the extent of reduction in number of unsaturated bonds. It has also been shown that ethyl and butyl esters of fatty acids have a higher oxidative stability and heat of combustion, demonstrate better environmental performance during operation of a diesel engine, which gives them significant advantages compared to the methyl esters used as a fuel. However, to date, butyl esters of fatty acids of vegetable oils are relatively poorly studied, and therefore require further research, especially extensive motor tests, both in pure form and in the form of mixtures with mineral fuels