Catalytic Hydrotreatment for the Development of Renewable Transportation Fuels

摘要

Biologically-derived feedstocks are a highly desirable source of renewable transportation fuel. They can be grown renewably and can produce fuels similar in composition to conventional fossil fuels. They are also versatile and wide-ranging. Plant oils can produce renewable diesel and wood-based pyrolysis oils can be made into renewable gasoline. Catalytic hydrotreatment can be used to reduce the oxygen content of the oils and increase their viability as a "drop-in" transportation fuel, since they can then easily be blended with existing petroleum-based fuels. However, product distribution depends strongly on feedstock composition and processing parameters, especially temperature and type of catalyst. Current literature contains relatively little relevant information for predicting process-level data in a way that can be used for proper life cycle or techno-economic assessment. For pyrolysis oil, the associated reaction pathways have been explored via experimental studies on model compounds in a bench scale hydrotreatment reactor. The reaction kinetics of each compound were studied as a function of temperature and catalyst. This experimental data is used to determine rate constants for a hybrid, lumped-parameter kinetic model of paradigm compounds and pyrolysis oil, which can be used to scale-up this process to simulate larger, pilot-scale reactors. For plant oils, some appropriate data was found in the literature and adapted for a preliminary model, while some experimental data was also collected using the same reactor constructed for the pyrolysis oil studies. With a systematic collection of kinetic data, hydrotreatment models can be developed that can predict important life cycle assessment inputs, such as hydrogen consumption, energy consumption and greenhouse gas production, which are necessary for regulatory and assessment purposes. As a demonstration of how this model can be incorporated into assessment tools, a technoeconomic analysis was performed on the hydrothermal liquefaction of lignin from a pulp mill, with some of the products sent to a refinery to create biofuel and some of the products used to create BTEX. The process-level model developed earlier was used to model hydrotreatment reactors used to generate commodity chemical co-products from phenolic compounds. Overall, this process showed promise and, with improving separations technology, could be a valuable source of revenue for pulp mills and refiners. However, in order to be truly profitable, the minimum selling price of the biofuel would need to be between $3.52 and $3.96 per gallon.