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In this study, the transesterification process of 4 different vegetable oils (sunflower, rapeseed, olive oil and used frying oil) took place utilizing ethanol, in order to characterize the ethyl esters and their blends with diesel fuel obtained as fuels for internal combustion engines. All ethyl esters were synthesized using calcium ethoxide as a heterogeneous solid base catalyst. The ester preparation involved a two-step transesterification reaction, followed by purification. The effects of the mass ratio of catalyst to oil, the molar ratio of ethanol to oil, and the reaction temperature were studied on conversion of sunflower oil to optimize the reaction conditions in both stages. The rest of the vegetable oils were converted to ethyl esters under optimum reaction parameters. The optimal conditions for first stage transesterification were an ethanol/oil molar ratio of 12:1, catalyst amount (3.5%), and 80 °C temperature, whereas the maximum yield of ethyl esters reached 80.5%.

Air pollution caused by diesel emissions, especially NOx, particulate matter, carbon monoxide and unburned hydrocarbons, has been a noteworthy matter. In Europe and the United States, legislative efforts towards improving air quality not only lead manufacturers to develop and introduce further improved emission control systems, but also the trigger demanding requirements on the oil industry towards producing advanced fuels. Therefore, much work on the effects of fuel properties on the emissions and engine performance has been performed worldwide. The fuels produced by the refineries usually comply with the existing specifications. However, alterations in the fuel properties may occur through the supply chain to the service stations due to failures of the distribution system or adulteration with lower value and taxation fuels (heating oil, marine diesel or industrial solvents).

Problems with the low-temperature operability performance of biodiesel in blends with petroleum diesel are infrequent, but continue to limit the use of biodiesel during winter months. A troubling aspect of this problem is that in some cases precipitates above the blend Cloud Point (CP) have been detected and have led to plugging of fuel filters and subsequent engine stalling, as well as plugging of fuel dispenser filters. Many researchers found that the saturated monoglyceride content was a main component of the material that was found on plugged fuel filters, as well as traces of Saturated DiGlycerides (SDG), were also present on the plugged fuel filters. This is the reason which forced the organization of standardization to suggest a procedure in order to predict the content of the Saturated MonoGlycerides (SMG) even with uncertainty which can vary from −50% to +50%. The model which was used will be the same as that which was introduced in the Annex C of EN 14214+A1:2013.