Состав добавки для улучшения характеристик современного дизельного топлива

Abstract

The aim of the study was to create an essential composition that improves the environmental and performance properties of contemporary diesel fuel obtained by deep oil refining including the stages of hydrotreating and hydrodesulphurisation. In order to improve the environmental properties of contemporary diesel fuels, such as cetane number and tribological characteristics, a mixture of biodiesel and low molecular weight ethers was proposed for application. Biodiesel was obtained by the transesterification reaction of triacylglycerols from non-edible (rancid) sunflower oil and methanol. By a quantum chemical calculation, the most likely attack direction of a nucleophilic reagent on a triacylglycerol molecule was determined as via a β-carbonyl carbon atom. During the chemical reaction, the absence of cis-trans isomerisation of double bonds was established in the radicals of unsaturated carboxylic acids presented in composition of both the triacylglycerols of vegetable oil and biodiesel molecules. Low molecular weight esters were obtained via the esterification reaction. The physico-chemical properties are determined for several ester mixtures consisting of biodiesel (30–90%) admixed by different saturated esters of lower molecular weight. As the content of saturated low molecular weight esters in mixtures increases, the physico-chemical characteristics of ester mixtures (for example, viscosity, density, cloud point and pour point) tend to improve. However, if the content of low-boiling saturated ethers increases to 60–70%, the boiling point becomes too low, leading to engine interruptions, e.g. the formation of air blocks. In the case of a decrease in the content of low-boiling saturated ethers to 10–30%, ester mixtures are characterised by a heavier fractional composition, as well as a density and viscosity exceeding the levels necessary for the uninterrupted operation of a diesel engine. As a result of the analysis of physico-chemical indicators, the composition of an ester mixture is proposed comprising 50 % vol. of biodiesel and 50 % vol.of low molecular weight saturated esters. The physico-chemical characteristics of such a mixture meet the requirements of the interstate standard for diesel fuels. Thus, the addition of the developed mixture of esters will lead to an increase in the cetane number of hydrotreated diesel fuels, subsequently reflecting in improvement of their lubricating and environmental characteristics.