The drive to reduce our reliance on petrodiesel has prompted the production of green diesel as an alternative, sustainable fuel. In this study, the hydrotreating of vegetable oils to produce green diesel was modeled in a two-step process where the first reactor removes the oxygen 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 and used in a kinetic study. The kinetic models simulate multiphase fixed bed hydrotreating 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. Additionally, diesel property calculation methods for cetane number and cloud point were implemented in the model to determine the value of the product fuel. 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. The model inputs and outputs were then used in Argonne National Laboratory’s Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model to evaluate greenhouse gas emissions of green diesel compared to petrodiesel. The molecular-level kinetic model based life-cycle analysis in GREET can direct future investment in green diesel with the advent of new environmental policies and economic incentives.

Molecular-level kinetic modeling of green diesel production via hydrodeoxygenation and hydroisomerization

254th National Meeting (2017)

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