Butyric acid esterification kinetics over Amberlyst solid acid catalysts: The effect of alcohol carbon chain length

► Rates of butyric acid esterification are characterized for linear alcohols. ► Alcohol steric effect, polarity, and hydroxyl concentration affect esterification rate. ► Kinetic model presented for butyric acid esterification with 2-ethylhexanol. ► Biodiesel cloud point substantially reduced by addition of butyrate esters. The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid.