Olefin Saturation Using Asphaltenes As a Hydrogen Source

Abstract

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 H2 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.

Application of Ethylene Tar as an Additive in Visbreaking of Petroleum Vacuum Residue

“…It is worth noting that both light and medium (<350 °C) and heavy (350−500 °C) distillate fractions of oil, industrial solvents, and byproducts can be effective H-donors in visbreaking and under certain conditions, even asphaltenes can function as a source of hydrogen. 34,35 3.2. Characterization of Visbreaking Products.…”

Storage Stability of Products from Visbreaking of Oilsands Bitumen

“…Such thermal hydrogenation of alkenes was demonstrated for the treatment of cracked naphtha using asphaltenes as hydrogen source. 45…”

“…The longer residence time at temperatures sufficiently high for a high rate of hydrogen transfer could be responsible for alkene saturation. Such thermal hydrogenation of alkenes was demonstrated for the treatment of cracked naphtha using asphaltenes as hydrogen source …”

Processing Unconventional Oil: Partial Upgrading of Oilsands Bitumen

“…One potential application of this concept that was evaluated was to employ the asphaltenes separated by solvent deasphalting as a hydrogen source for transfer to cracked naphtha from thermal conversion by a process such as visbreaking. It was reported that this olefin-treating concept was technically feasible and that 60% olefin conversion in cracked naphtha could be achieved by soaking the cracked naphtha with asphaltenes in a 1:4 ratio for 3 h at 350 °C . The asphaltenes used in the process became a sacrificial hydrogen donor.…”

“…It was reported that this olefin-treating concept was technically feasible and that 60% olefin conversion in cracked naphtha could be achieved by soaking the cracked naphtha with asphaltenes in a 1:4 ratio for 3 h at 350 °C. 76 The asphaltenes used in the process became a sacrificial hydrogen donor.…”