Deactivation of macroporous ion-exchange resins by acetonitrile and inhibition by water in the simultaneous synthesis of ethyl tert-butyl ether (ETBE) and tert-amyl ethyl ether (TAEE)

Abstract

The deactivating effect of acetonitrile (ACN) and ACN/water mixtures on the feed stream has been investigated for the simultaneous syntheses of ethyl tert-butyl ether (ETBE) and tert-amyl ethyl ether (TAEE) over the ion-exchange resins Amberlyst™35 (A-35) and Purolite®CT-275 (CT-275). Experiments were performed in a fixed bed catalytic reactor free of mass transfer effects. The explored range of temperature was 313–353 K and ACN concentrations in the ethanol feed stream ranged from 0–4000 ppm. The deactivation effect of ACN was similar for A-35 and CT-275. Two different periods are distinguished in the deactivation evolution: an initial stage in which activity does not decrease, due to the release of previously adsorbed water, followed by an exponential-like activity decay, due to the neutralization of active sites by ACN-derived compounds. Deactivation is favored by poison concentration and temperature, following a selective poisoning pattern through which the most accessible sites are neutralized readily. Several deactivation kinetic models have been tested to describe the activity loss, the best being a first order model. The estimated activation energy for the overall deactivation process is 33.1 ± 1.4 kJ mol⁻¹. In addition, the inhibitory effect of water at concentrations from 1000 to 5000 ppm has been evaluated finding that models based on Langmuir and Freundlich isotherms can describe the experimental observations.