Product Value Modeling for an NGL to Liquid Transportation Fuel Process

Light alkanes from shale resources can potentially be converted to an easy-to-transport liquid hydrocarbon product by catalytic dehydrogenation followed by catalytic oligomerization. The chemical species in the liquid product and their concentrations depend on the process design, operating conditions, and choice of catalyst(s). In order to optimize process design and catalyst selection, it is important to be able to evaluate the economic value of the liquid product stream as a function of design variables and operating conditions. As an initial effort in addressing this challenge, the mixture octane number, a key property in determining the value of a gasoline blend stock, is considered. An approach is outlined for the estimation of the mixture octane number using a functional group contribution method and appropriate mixing rules, and this estimation procedure is interfaced with a microkinetic oligomerization reactor model. This combined microkinetic and octane number modeling approach is demonstrated using two case studies involving ethylene and propylene as feed streams, with product streams characterized in terms of octane number, molecular size distribution, and degree of branching. Results of this type are expected to provide guidance on catalyst development and process optimization.