UCLA

Most sources agree that a solely renewable energy future is years off at best and therefore carbon based fuel sources will continue to play a substantial role in energy production. For this reason, this research focused on one path towards improving the efficiency and total usability of carbon based resources. Current processing methods for biofuels produce many short chain heavily oxygenated hydrocarbons at low yield. These molecules require further upgrading to be useful as fuels or chemical intermediates, primarily, C-C bond formation to form longer hydrocarbon chains and hydro-deoxygenation to remove O-atoms. This research focuses on discovering catalyst site requirements for the selective formation of C-C bonds between aldehyde molecules with the removal of O-atoms via dehydration/hydrogenation steps with H-atoms derived from alkanes. Kinetic experiments show that butyraldehyde can be converted to 2-ethyl-2-hexenal, via acid-catalyzed aldol-condensation at 200oC under a 4 kPa partial pressure of butyraldehyde on the acid site of BEA zeolite at a selectivity of 94% and rate of 8.16 x 10-10 mol s-1 Al-1. The selectivity shifts toward aromatization products (triethylbenzene and xylenes) at a selectivity of 20% and cracking products (propene and pentene) at a selectivity of 18% as temperature increases from 200oC to 300oC. Addition of H-atoms as isobutane increases the rate of production of 2-ethyl-2-hexenal (from 8.16 x 10-10 mol s-1 Al-1 to 8.54 x 10-10 mol s-1 Al-1 ) but shifts the selectivity towards triethylbenzene (from 6% to 14%).

Using a metal hydrogen transfer catalyst (in the form of Zn-exchanged BEA) causes a shift in the selectivity of butyraldehyde reactions toward 2-ethyl-2-hexenal (from 94% to 98%) which indicates metal catalyzed hydrogen transfer to unsaturated species formed during aldol-condensation. Using a different metal hydrogen transfer catalyst (in the form of Co-exchanged BEA) causes a shift in the selectivity of butyraldehyde reactions from 2-ethyl-2-hexenal (from 94% to 84%) towards cracking products (16% C4 products from butyraldehyde, 17% C5 products with the addition of isobutane) .