(693c) Insight into the Reactions of Upgrading Bio Aldehydes to High Value Aromatic Precursors

Terephthalic acid and phthalic anhydride are high value and high market commodity chemicals, used in polyester and plasticizers industry. These chemicals are currently produced from oxidation of p-xylene and o-xylene that are derived from the crude oil based resources. In this work, 4-methylbenzaldehyde and 2-methylbenzaldehyde, precursor of terephthalic acid and phthalic anhydride, were synthesized from biomass derived acetaldehyde through catalytic aldol condensation. The conversion of acetaldehyde to methyl benzaldehyde reaction takes place in two step reaction mechanism. The first step is the acetaldehyde condensation to form crotonaldehyde, and the second step is the conversion of crotonaldehyde to methylbenzaldehyde. Crotonaldehyde is an α,β-unsaturated C4 aldehyde, which contains two positions (C=C and C=O) to form the C-C bond. Therefore, the position of the C-C bond formation plays major factor in determining the product selectivity. In this research, various acid-base catalyst with different strengths, such as hydrotalcite and ZnZr, were investigated to understand how the nature of the basic and acid site control the reaction pathway to improve the product selectivity. In addition, several reactants with different unsaturated bond were incorporated as model reactants for reaction pathway study. The spent catalysts were characterized to elucidate the deactivating mechanism. This presentation will discuss the reaction mechanism and the catalyst selection for this chemistry to produce the highest methyl benzaldehyde generation under various operating conditions.