COMPARISON OF BI-MOLECULAR DECOMPOSITION PATHWAYS FOR CARBOXYLIC ACIDS OF RELEVANCE TO BIOFUELS

摘要

The thermal deoxygenation of carboxylic acids is an important step in the conversion of biomass into aliphatic hydrocarbons suitable for use in renewable biofuels and as petrochemical replacements. Decarboxylation, a primary decomposition pathway under pyrolysis conditions, represents an ideal conversion process for this purpose, because it eliminates two atoms of oxygen for every carbon atom removed. The dehydration of organic acids represents a direct pathway to ketene and ketene derivatives (RR'C=C=0). The major industrial use of ketene is in the production of acid anhydrides and diketene derivatives, which are themselves important precursors in the synthesis of a wide range of value added chemicals.Ketones are also used in the preparation of p-lactones and P-lactams via [2+2] cycloaddition reactions with ketones and imines, respectively. Thus, it is critical to understand the branching ratios between decarboxylation and dehydration. The uni-molecular, gas-phase, thermal decomposition of carboxylic acids occurs through two competing 4-centered, pericyclic mechanisms: decarboxylation and dehydration. See Reactions 1 and 2, shown for acetic acid. (Note: Acetic acid will be the acid discussed in this pre-print).