(652a) Development of a Heterogeneous Guanidine Base Catalyst for the Conversion of Lipids to a Sustainable Biofuel

The production of biodiesel, a mixture of fatty acid methyl esters, has grown over the last two decades. However, due to limited feedstock supplies, excessive amounts of process wash water, and a low-value byproduct (i.e. glycerol), the biodiesel industry, and the renewable fuels industry as a whole, may see a decline in the coming years.  This research focuses on the production of a biofuel, which is similar to biodiesel, except it not only produces fatty acid methyl esters but also fatty acid glycerol carbonates (FAGCs) by replacing methanol with dimethyl carbonate (DMC). The envisioned process would use no water washing steps, could convert triglycerides and phospholipids, and would have no unwanted, or low-valued, byproducts.

            From early experiments, it was discovered that changing the methylating agent from methanol to DMC would require a change in catalyst from the typical sodium methoxide used in biodiesel manufacturing. The criteria for a novel catalyst are 1) readily able to catalyze the DMC to form the methoxy anion, 2) requires no neutralization step, and 3) able to also catalyze phosopholipid-containing feeds. 

            One of the drawbacks to the current biodiesel industry is that the process is limited to refined and degummed plant oils.  If a conversion process could be developed that would also convert phospholipids, then lower value microbial-based feedstocks could be used in place of expensive plant-derived oils. Therefore, a series of hybrid organic-inorganic composite materials was synthesized by grafting the guanidine base 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) on Mg–Al layered double hydroxide (Mg/Al LDH with a Mg/Al molar ratio of 3 to 5) intercalated with sodium dodecylsulfate (SDS). The basal spacing of SDS-LDH was controlled simply by tuning the pH of the aqueous solutions and the Mg/Al molar ratio during the catalyst preparation. In our approach, TBD is attached with a coupling agent (3-Glycidyloxypropyl) trimethoxysilane (3GPS), and N-cetyl-N,N,N-trimethylammonium bromide (CTAB) molecules added afterwards, in the SDS-LDH gallery. The catalyst materials were characterized by XRD, SEM, EDX, FTIR, and Raman spectroscopy. Based on these results, a schematic representation for the functionalization of Mg/Al LDH surface with immobilized TBD will be presented.  Results have indicated that this heterogeneous catalyst would indeed fit the initial criteria.  Development of the catalyst and a proposed mechanism for converting both triglycerides and phospholipids will be presented.