Olefin Saturation Using Asphaltenes As a Hydrogen Source

To facilitate the pipeline transport of oilsands bitumen, bitumen viscosity must be decreased. Decreasing bitumen viscosity by whatever means adds to the production cost of bitumen. One of the low cost methods to decrease bitumen viscosity is mild thermal cracking by visbreaking. Thermally cracked products are potentially fouling in nature and the maximum olefin content of upgraded bitumen is limited by pipeline specifications to reduce risk of fouling. Hydrotreating is conventionally applied to treat cracked products. A process alternative to hydrotreating that does not require an external source of H 2 was evaluated for application in partial bitumen upgrading processes that employ thermal conversion in conjunction with solvent deasphalting. The proposed olefin saturation process employs thermally induced hydrogen transfer from asphaltenes as a hydrogen source to saturate olefins in cracked naphtha. The process chemistry was demonstrated first using model olefin and hydrogen donor mixtures, then using model olefin and asphaltenes mixtures, and finally using industrially cracked naphtha and asphaltenes-rich material. The operating temperature range investigated was 250–350 °C. It was found that the main reactions of the olefins were (i) saturation, (ii) alkylation, (iii) dimerization, and (iv) double bond isomerization. The conversion of model naphtha and cracked naphtha with asphaltenes was comparable, indicating that the increased complexity of the cracked product did not measurably affect the olefin saturation. It was shown how the proposed process could be integrated in a solvent deasphalting process by replacing the asphaltenes stripper. It was possible to obtain 60 wt % 1-decene equivalent olefin conversion in a thermally cracked naphtha by reacting the cracked naphtha with asphaltenes in a 1:4 ratio at 350 °C for 3 h. The study aim was to show technical feasibility, and although a range of conditions was investigated, the study did not optimize the process.