Molecular arrangement in diesel/biodiesel blends: A Molecular Dynamics simulation analysis

Biodiesel is an important biofuel which has attracted attention because it can partially or totally replace petrodiesel fuel. Based on environmental, economic and social issues, government policy in many countries has mandated the addition of biodiesel to petrodiesel fuel, promoting the use of diesel/biodiesel blends. In this context, we evaluated the molecular interactions between native diesel molecules (n-paraffins, isoparaffins, naphthenes, aromatics, and heteroatomics) and four different methyl esters (from stearic acid, oleic acid, linoleic acid and linolenic acid), the most representative biodiesel molecules. We applied Molecular Dynamic simulations to obtain a detailed picture of the interactions and to quantitatively compute the accumulation of diesel molecules around the methyl esters by distribution functions. The results revealed that the diesel molecules accumulated around the fatty acid methyl esters at a distance of about 2.2 Å due to the non-polar interactions as well as at approximately 1.8 Å as a result of the hydrogen bonds formed between carbazole and esters. The data also demonstrated that the ester molecules diffuse into the blends less than the diesel molecules. In summary, the present investigation contributes to the fundamental understanding of the interactions between biodiesel and diesel molecules, revealing the arrangement and behavior of the diesel and biodiesel molecules in the diesel/biodiesel fuel blend.