Thermal stability and water effect on ion-exchange resins in ethyl octyl ether production at high temperature

• Addition of chlorine atoms to ion-exchange resins minimizes sulfonic group leaching.
• Amberlyst 70 and Purolite CT482 are stable up to 190 °C in ethyl octyl ether synthesis.
• Reaction rate drop is due to preferential adsorption of water on sulfonic groups.
• The catalytic activity of chlorinated resins is fully recovered on removing water.
• Activity drop is stronger in diethyl ether formation than in ethyl octyl ether one.

Thermal stability and water inhibition effects were studied at 150 and 190 °C on the chlorinated acidic polystyrene-divinylbenzene resins Amberlyst 70, Amberlyst XE804 and Purolite CT482, and the non-chlorinated one Dowex 50Wx2. Catalytic activity in the reaction between ethanol and 1-octanol to form ethyl octyl ether (EOE) was monitored for 70 h in a continuous fixed-bed reactor. Leaching of sulfonic groups at 190 °C was found to be negligible for Purolite CT482 and Amberlyst 70, but it was significant for Amberlyst XE804 and Dowex 50Wx2. The activity decay to a steady EOE reaction rate on Purolite CT482 and Amberlyst 70 has been ascribed to the reaction rate inhibition by the formed water. However, water adsorption on the catalyst also modified the resin morphology during the course of the reaction. Adsorbed water swelled the gel-phase and more acid sites became accessible for 1-octanol molecules. As a result, the activity decay of EOE and the longer byproduct di-n-octyl ether syntheses was smaller than that of the shorter one diethyl ether.

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