PHYSICAL AND CHEMICAL PROPERTIES OF BIODIESEL FUEL AND METHODS OF THEIR CHANGE
Biodiesel (BT) has a renewable raw material base, has better environmental properties and greater operational safety than petroleum. Several biodiesel samples from various vegetable oils were synthesized and analyzed. The influence of the composition of biodiesel on its physical-chemical and operational properties was studied. It was determined that BT has a higher density, viscosity, degree of unsaturation, low temperature characteristics than hydrocarbons of petroleum fuels, which can degrade the performance of a diesel engine. It was found that the physicochemical characteristics of BTs depend on the ratio of medium- and long-chain radicals of fatty acids, as well as on the degree of their unsaturation. It was shown that in order to improve the pour point and cloud point of BT in its composition, the proportion of unsaturated acid residues should be increased, but this can worsen its oxidative stability. It was revealed that for balance, the presence of unsaturated acid radicals with one double bond (oleic and palmitooleic acids) is required in BT molecules. The content of residues of linoleic and linolenic acids (with two double bonds) should be minimal. It was found that limiting radicals of small length increase oxidative stability and cetane number, but worsen the low-temperature properties of BT. It was shown that a change in the fatty acid composition of BT by adding separately synthesized low molecular weight esters to it requires an expansion of the raw material base for biodiesel production and new hardware for the esterification reaction. Another way to change the composition of triacylglycerols of vegetable oil is to modify the plant itself by selection or genetic engineering.