Hydrotreatment of Olefins in Thermally Processed Bitumen under Mild Conditions

The stabilization of olefins in a thermally processed bitumen is a focal area for the development of bitumen partial upgrading technologies. Although a number of approaches have been proposed, including alkylation, oligomerization, and adsorption, hydrotreatment is still the most effective strategy for treating olefins in thermally cracked products such as coker naphtha. In our previous work, we studied the hydrogenation of model olefin compounds to understand their reactivity under mild conditions. This paper is a follow-up study focusing on the hydrotreatment of olefins in a thermally processed bitumen using a bench-scale continuous hydroprocessing unit. Two different scenarios were investigated: (1) hydrotreating the olefin-rich light fraction (IBP-280 °C) of the thermally processed bitumen product and (2) hydrotreating the whole product. The cracked feedstock was prepared by processing oil sand bitumen under visbreaking conditions. It was found that on-specification product for olefin content (<1.0 wt % 1-decene equivalent) could be obtained by hydrotreating the light fraction at lower temperatures (∼275–300 °C) and with less hydrogen as compared to hydrotreating the whole bitumen product, for which temperatures close to 325 °C are required in addition to about double the hydrogen input. Hydrotreating the whole product, however, brings the benefit of markedly reducing the total acid number and increasing the American Petroleum Institute gravity, which can be helpful to achieve the product quality goals of partial upgrading. Product characterization by advanced techniques such as 1 H NMR and two-dimensional gas chromatography has revealed interesting reactivity patterns of olefins, sulfur compounds, and aromatics during mild hydrotreatment.