(297c) Conversion of Phospholipids to Renewable Diesel: Reaction Pathways and Effects On Hydrotreating Catalysts

Recent research has identified the use of lipids for the production of green fuels via heterogeneous catalytic hydrotreating. These green fuels, which are comprised of the same types of compounds as petroleum-based fuels, could be produced from a wide variety of plant, animal, and microbial lipid sources and could replace significant amounts of petroleum fuels. These lipid feedstocks would be comprised of mainly free fatty acids, acylglycerides, and phospholipids. Inasmuch, traditional petroleum refining using hydrotreating with transition metals embedded on Al2O3 catalysts have had difficulties in cracking compounds with inorganic species, such as phosphorus. However, combinations of Co-Mo have shown to have better success over Ni-Mo in terms of poisoning of the catalyst.

This study focuses on the cracking of model phospholipid compounds, namely phosphatidic acid, phosphatidylglycerol, and phosphatidylethanolamine, on sulfided hydrotreating catalysts. Reaction pathways were determined from product formation using a pulsed-type microreactor with online mass spectrometry. In addition, catalysts were analyzed for changes in surface characteristics upon reaction with the phospholipids. Thermogravimetric analysis has been used to determine coking amounts and for Hoffman reactions using propylamine to investigate changes in acid site densities. Changes in transition metals and buildup of inorganic phosphorus content on the catalyst surface were determined using inductively couple plasma mass spectrometry. A time-on-stream analysis was used to determine the long-term consequences that phospholipid reactions have on hydrotreating catalysts in cyclical reaction/regeneration processes.

Hydrotreating reactions showed a formation of C15 to C18 hydrocarbons stemming from the fatty acid chains, which were 16 and 18 carbons in length. The ratio of odd to even hydrocarbons (0.35) indicated that hydrodeoxygenation and decarbonylation mechanisms dominated over decarboxylation. In regards to phosphatidylglycerol, the glycerol backbone was first cracked and transformed to n-propenal via hydrodeoxygenation, followed by the formation of n-propanol via hydrogenation.

This research demonstrates the utility of using microbial-based feedstocks, which contain phospholipids, as a renewable source for transportation fuels. Reacting of phospholipids along with acylglycerides, without the need for pretreatment, realizes significant savings in processing. This paper will demonstrate the hydrotreating reaction pathways and the catalyst surface characterizations of pre and post reactions.