Model-Based Optimization of an Alkene Oligomerization Process to Produce High Octane Fuels

Ridha et al. [1] proposed a shale gas transformation process to convert shale gas condensate into liquid fuels via catalytic dehydrogenation followed by catalytic oligomerization. Liquid fuels are easier to transport from the remote shale gas base regions to gas processing plants than NGLs. They can also be directly sold in the regional fuel market.

This work focuses on the oligomerization reactor of the Ridha et al. [1] process, using a zeolite (H-ZSM-5) catalyst. The objective of this work is to identify the operating conditions of the reactor that would maximize the high value products. The value of the liquid product stream from oligomerization is measured in terms of barrels of octane. We use a microkinetic model that we developed to predict the concentrations of individual chemical components exiting the oligomerization reactor as a function of the operating conditions such as temperature. The oligomerization products are separated into a light stream, which is recycled, and a heavy product stream. We first calculate the octane numbers of the pure components in the product stream by the structural group contribution method reported in Albhari [2]. Then, we apply appropriate mixing rules to calculate the octane number of the product stream blend. The optimization problem aims to calculate the reactor operating conditions that would maximize the value of the product stream subject to the constraints imposed by the reaction chemistry, and by the size and dynamics of the oligomerization reactor. Operation under optimized operating conditions results in value addition for the overall NGLs to liquid hydrocarbon conversion process.

REFERENCES

[1] Ridha, T., Li, Y., Gençer, E., Siirola, J., Miller, J., Ribeiro, F., & Agrawal, R. (2018). Valorization of Shale Gas Condensate to Liquid Hydrocarbons through Catalytic Dehydrogenation and Oligomerization. Processes, 6(9), 139.

[2] Albahri, T. A. (2003). Structural group contribution method for predicting the octane number of pure hydrocarbon liquids. Industrial & Engineering Chemistry Research, 42(3), 657-662.