(592h) Mild Pyrolysis of P3HB/Switchgrass Blends for the Production of Bio-Oil Enriched With Crotonic Acid

Boateng, A. A., USDA-ARS
Dorado, C., Agricultural Research Service, USDA
Schweitzer, D., Metabolix Inc.
Sparks, K., Metabolix
Snell, K., Metabolix, Inc.

Poly-3-hydroxybutyrate (P3HB) is a naturally occurring polyester that is produced by some microorganisms as a method of carbon and energy storage. In addition to being utilized as a renewable, biodegradable substitute for plastics produced from petroleum, it can be thermally degraded in situ to crotonic acid in high yield. Crotonic acid can be used as a platform chemical enabling an alternative access to high-valued industrial and fine chemicals. For example, it can be reduced to n-butanol for chemical or fuel applications or oxidized to maleic anhydride. Other targets available through simple transformations include propylene and acrylic acid. In the work presented in this presentation, the mild pyrolysis of switchgrass/P3HB blends that mimic P3HB-producing switchgrass lines was studied in a pilot scale fluidized bed reactor with the goal of simultaneously producing crotonic acid and switchgrass-based pyrolysis oils to be further converted to biofuels. While pure P3HB decomposes under distillation conditions to provide a near quantitative yield of crotonic acid, pyrolysis of P3HB-containing switchgrass requires an additional crotonic acid purification step. Factors such as pyrolysis temperature, residence time, flow rates and particle size of the P3HB were studied for their effects on the recovery of crotonic acid as a component of the pyrolysis oil produced from the mixture. Effects of the presence of P3HB and crotonic acid on the switchgrass bio-oil in terms of chemical composition and properties will also be examined. Furthermore, efforts to isolate pure crotonic acid from the switchgrass bio-oil will be discussed. Finally, an example of the utility of crotonic acid as a chemical feedstock will be briefly discussed. Hydrogenation of the n-butyl ester of crotonic acid was found to produce n-butanol in excess of 90 % yield over commercial Cu-based catalysts under the optimized conditions.