(576c) Branched-Chain Alcohol Esters as Low-Temperature Biofuel Constituents

Branched-chain alcohol esters of carboxylic acid improve the cold flow properties of diesel fuels and are thus attractive biofuel constituents. This study focuses on liquid phase esterification of butyric acid as a model compound with a series of branched alcohols catalyzed by sulfuric acid and commercially available solid acid catalysts such as Amberlyst cationic exchange resins. After identifying conditions to minimize both internal and external mass transfer resistances, the effects of temperature, water content, and the mole ratio of alcohol to butyric acid in the esterification reaction have been investigated. Using an activity based, pseudo-homogeneous kinetic model, rate constants for esterification in the resin catalysts are determined for different branched chain alcohols. The effects of alcohol chain length and structure and water content on rate and catalyst reusability are described, and the implications for branched esters as advanced biofuel constituents are discussed.