Preparation of n-amyl acetate via esterification of acetic acid and n-amyl alcohol using [HSO3-pmim][HSO4]/SiO2 as catalyst: Catalyst preparation, characterization and reaction kinetics

Abstract

In order to present a green method to produce n-amyl acetate, a novel supported ionic liquids (ILs) catalyst [HSO3-pmim][HSO4]/SiO2 was synthesized by sol–gel method and was used to catalyze the esterification reaction of acetic acid and n-amyl alcohol. The kinetic equations for the esterification were established based on ideal quasi homogeneous (IQH) model and Langmuir-Hinshelwood-Hougen-Watson (LHHW) model. The parameters in the equations were obtained from kinetic experimental data fit using fourth order to fifth order Runge-Kutta algorithm. The morphology, surface elements, structural stability, pore diameter, specific surface area, thermal stability and distribution of acid strength of the fabricated catalysts were characterized in detail, while immobilization yield, corrosiveness and stability of the catalyst were also evaluated. The reaction kinetic performances of [HSO3-pmim][HSO4]/SiO2 were compared with conventional catalysts like sulfuric acid, P-toluenesulfonic acid, [HSO3-pmim][HSO4] and [HSO3-pmim][HSO4]/Silica gel by the reaction kinetic experiments. The equilibrium conversion of acetic acid in the presence of [HSO3-pmim][HSO4]/SiO2 was increased by 10.8% after immobilization. The mean absolute squared error of the kinetic equations of the esterification based on LHHW model and IQH model were 3.87 × 10-5 and 1.49 × 10-4 respectively. LHHW model based on the solid–liquid reaction mechanism were in better agreement with the experimental results. This concept of recyclable supported IL catalyst provides promising applications prospects for the industrial production of n-amyl acetate.