Fuel and Fuel Additives from Biomass

Synthesis of transportation fuel or fuel additives from straw and other agricultural and forestry waste products is a green and sustainable energy solution. The thesis presents a series of new catalytic technologies for this purpose.

Ethanol is already widely used as a renewable fluid transportation fuel, but predominantly produced from corn and sugar cane which may also be used as food. In this project, a catalytic system for synthesis of methyl acetate (MA) from ligno-cellulosic biomass, obtained from agricultural waste products, was developed. MA is a precursor for production of ethanol. More specifically, the porous catalyst H-mordenite catalyzed dimethyl ether (DME) carbonylation to yield MA. Improved activity of the catalyst was observed with optimal loading (1 wt%) of copper impregnated onto the H-mordenite. This improved activity from 65 to 81 % in two hours with about 97 % selectivity. A known drawback of H-mordenite as a catalyst is deactivation by pore filling, but here the active lifetime of the catalyst was increased by desilication followed by recrystallization.

Another renewable bio-fuel is γ–valerolactone (GVL). In the project, GVL was synthesized from levulinic acid (LA) and its methyl ester (MLA) using a novel bimetallic catalyst consisting of Au-core Pt-shell nanoparticles supported on graphitized carbon black (Au@ Pt/G-CB). The catalyst efficiently catalyzed the LA to GVL reaction under relatively mild conditions in water to give quantitative yields of GVL.

A well-known initial treatment of ligno-cellulosic biomass is pyrolysis which gives pyrolysis liquid, also known as bio-oil. Bio-oil is a dark brown fluid with a strong smoky odour. It is not directly usable in its initial form but contains more than 300 compounds, the majority being aldehydes. These can be a source of carbonyl compounds as an alternative to using fossil based feedstocks. In the project, an inexpensive copper oxide catalyst was developed and tested for the aerobic oxidation of alcohols to carbonyl compounds. A reaction mechanism involved in the oxidation process was also proposed and experimentally supported. Further, imination of these carbonyl compounds with primary amines using copper oxide and silver nanoparticles supported on alumina (Ag/Al2O3) is presented.

Finally, hydrogenation of imines was studied with Ag/Al2O3 to obtain the corresponding secondary amines. The prepared nanocatalyst proved highly efficient, yielding excellent conversion and selectivity towards the reduction of both aromatic and aliphatic imines under relatively mild reaction conditions. The versatility of the nanocatalyst is demonstrated by application to synthesis of secondary amines via a tandem reaction with high selectivity (up to 98 %) towards the targeted product.