No abstract

Esterification reactions are typically equilibrium limited, and face challenges with product purification. They are carried out commercially using either large excess of one of the reactants, or by removing one of the products continuously in a reactive distillation column (RDC). In the present work, we studied the kinetics of esterification reactions of dilute acetic acid with iso-amyl alcohol to produce a value added ester (iso-amyl acetate) using ion-exchange resins, Purolite® CT-175 and CT-275 as catalysts in a batch reactor. The effect of agitation speed, catalyst particle size, reaction temperature, acetic acid concentration, acetic acid to iso-amyl alcohol molar ratio and catalyst loadings were investigated to optimise the reaction conditions. The non-ideality of each species in the reacting mixture was accounted for by using the activity coefficient via the use of the UNIFAC group contribution method. The kinetic data were correlated with Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Eley-Rideal (E-R) models. The detailed kinetic data and a reliable rate expression for the esterification of acetic acid with an aliphatic alcohol (iso-amyl alcohol) would be useful for the simulation and design of an RDC for removing dilute acetic acid from aqueous streams. Another objective of this work was to evaluate the techno-feasibility of this operation through a systematic procedure of residue curve map (RCM). RCM gives a design engineer an idea of the existence of any separation boundaries imposed by the singular points corresponding to the reactive or kinetic azeotropes and thereby provide an insight into the feasibility of the desired operation. In the present study, RCM was generated for the quaternary system (acetic acid - iso-amyl alcohol - iso-amyl acetate - water) under different conditions to work out the feasibility of the operation. This map also suggests possible column sequencing or configurations to achieve a desired duty in an RDC.

With ever-growing environmental concerns, petrochemical and fine chemical industries face an omnipresent issue in recovering dilute acetic acid from its aqueous solutions. Catalytic distillation holds an ascendancy over conventional physical separation methods such as distillation and extraction. Distillation is associated with the high costs involved in vaporising the more volatile water that exists in high proportions and possesses a high latent heat of vaporisation. Extraction is limited in view of the distribution of the components in the reacting system. The implementation of catalytic distillation reduces capital and operating costs, and allows for a wider range of operating conditions. Catalytic distillation is receiving increasing attention and holds a huge potential for the recovery of acetic acid. Through the application of catalytic distillation via the reaction of acetic acid with iso-amyl alcohol, a useful ester in the form of iso-amyl acetate could be produced.In the present work towards further process development, the synthesis of iso-amyl acetate via reactive distillation is studied using Katamax® catalyst packing in the catalytic reactive section. The reactive distillation experiments were carried out at laboratory scale in a 50 mm diameter column with a catalytic packing section of 1 m and non-reactive packed enriching and stripping sections of about 1 m each. A cation exchange resin catalyst, Purolite® CT-175, was used. The experiments were conducted with the aim of achieving an optimum column configuration as well as process conditions for the synthesis of iso-amyl acetate in a reactive distillation column (RDC). Several variants of the RDC set-up e.g. total feed mole ratio, reflux ratio, location of feed points, reflux configuration and acid concentrations were explored for the recovery of dilute acetic acid and to achieve a high purity value added product, iso-amyl acetate.