Liquid-phase dehydration of 1-octanol, 1-hexanol and 1-pentanol to linear symmetrical ethers over ion exchange resins

Abstract

Dehydration of 1-octanol, 1-hexanol and 1-pentanol to di-n-octyl ether (DNOE), di-n-hexyl ether (DNHE) and di-n-pentyl ether (DNPE), respectively, has been studied in the liquid phase at 423K in a batch reactor on ion exchange resins as catalysts. Tested catalysts were the macroporous resins Amberlyst 15, Amberlyst 35, CT175, CT275 and CT276 (high crosslinking degree); Amberlyst 16, Amberlyst 36 and CT252 (medium crosslinking degree); Amberlyst 39 and Amberlyst 70 (low crosslinking degree), and the gel type ones CT224, Amberlyst 31, Amberlyst 121 and Dowex 50Wx4-50. Amberlyst 46, an ion-exchange resin sulfonated only at the polymer surface and Nafion NR50 were also tested for comparison purposes. Data show that the yield of linear symmetrical ethers (DNOE, DNHE and DNPE) highly depends on the resin structure so that best results are obtained on Amberlyst 121, Amberlyst 31 and Dowex 50Wx4-50 (the most swollen resins in reaction medium). The high ether yields are due both to the high alcohol conversions and especially to the very high selectivity to ethers (≥94%) shown by that resins. Finally, by comparing initial reaction rates of ether formation with those obtained on Amberlyst 46 an estimation of the fraction of sulfonic groups that take part in the reaction is given.