(174e) Kinetic Modeling of the Production of Green Diesel Via Hydroprocessing

Due to environmental and government policy concerns, green diesel production has been proposed to be a viable and sustainable alternative to petrodiesel. In this study, the hydroprocessing of plant oils to produce green diesel was modeled in a two-step process: a hydrodeoxygenation unit followed by a hydroisomerization unit. The first reactor removes oxygen in the oils and the second reactor isomerizes and cracks the paraffin product. Reaction networks that include the detailed triglyceride, free fatty acid, and paraffin hydroprocessing chemistry to produce paraffin-rich diesel range fuels were generated. Due to the large number of possible isomers and parallel reaction pathways, the networks were analyzed to minimize solution time and maximize kinetic information. The reaction networks were used in a kinetic study that simulates multiphase fixed-bed hydroprocessing units under plug-flow conditions with side-by-side reaction and vapor-liquid equilibrium. Linear free-energy relationships and literature data were used to reduce and tune the parameters of the catalyst-based rate laws. The kinetic model was supplemented with diesel property calculation models for cetane number and cloud point. This allowed for the optimization of process conditions like liquid hourly space velocity, reactor temperature, and hydrogen pressure to reach the combustion and cold-flow property targets of the product fuel.