Reliability of the synthesis of C10–C16 linear ethers from 1-alkanols over acidic ion-exchange resins

Abstract

More-than-nine-carbon-atom-containing linear ethers such as ethyl octyl ether (EOE), di-n-pentyl ether (DNPE), di-n-hexyl ether (DNHE) or di-n-octyl ether (DNOE) increase the quality of the diesel blends making them environmentally friendly. In this work, dehydration of 1-pentanol, 1-hexanol and 1-octanol to DNPE, DNHE and DNOE, respectively, as well as the reaction between 1-octanol and ethanol to give EOE are shown to be a good path for obtaining these linear ethers. Acidic macroreticular and gel-type polystyrene-divinylbenzene (PS-DVB) ion-exchange resins have been tested as catalysts for these reactions in liquid phase at 423 K. In the dehydration reactions of 1-pentanol, 1-hexanol and 1-octanol, as a rule, selectivity to linear ether decreased with the length of the ether over macroreticular resins of high and medium DVB%. On the contrary, no differences in selectivity to DNPE, DNHE and DNOE were observed over gel-type and macroreticular resins of low DVB%. In the reaction for obtaining EOE from ethanol and 1-octanol, EOE synthesis competes with those of DNOE and diethyl ether. The best selectivity to EOE and DNOE were found in gel-type and macroreticular resins of low DVB% too. Swelling of the resin in the polar reaction medium was found to be a decisive factor to enhance the selectivity to long linear ethers. Therefore, Amberlyst 121 and CT 224 are proposed to catalyze the synthesis of these ethers; Amberlyst 70 is suggested as the best one for working above 423 K.