Investigating the role of aliphatic olefins in fouling of thermally cracked bitumen by testing fouling tendency of model aliphatic olefin compounds in light fractions

Olefins are considered non-desirable compounds that are formed in the thermal cracking step of crude oil. Due to their high reactivity, they are linked to the fouling tendency of thermally cracked petroleum products. In this work, the role of aliphatic olefins in the fouling of thermally cracked petroleum products is studied by investigating the fouling tendency of model aliphatic olefin compounds blended with Western Canadian Select (WCS) crude, a low-fouling material, in an Alcor hot liquid process simulator (HLPS) fouling testing apparatus. The tested model olefin compounds were selected to have different types (mono-olefin, conjugated diolefins, nonconjugated diolefins), structures, and boiling points. The model olefin compounds were tested individually and in mixtures to determine the fouling tendency. Moreover, a light fraction of thermally cracked bitumen, which contains a significant concentration of olefinic species, was blended with the heavy fraction of WCS to simulate a thermal cracking derived olefin sample with a reasonable olefin content. Olefin and olefin mixture blends were tested in the Alcor HLPS unit to determine the temperature drop (Delta T) due to fouling on the heated rod of the Alcor HLPS unit that leads to a reduction in the heat transfer coefficient. All tested samples resulted in low or low-medium fouling when compared to a thermally cracked bitumen. The results indicated that aliphatic olefins, in the low boiling range, were not the sole contributor to fouling and other constituents, such as asphaltenes or high molecular weight olefins in the heavy fractions, and other properties, such as product stability (measured by P-value), might have a synergetic effect with olefins in the fouling mechanism. Therefore, the role of aliphatic olefins in fouling in petroleum products is reduced in the absence of the aforementioned constituents and properties.