Controlling the curing process of novolac phenolic resin during preparation of carbon molecular sieve membrane for propylene/propane separation

Abstract

A carbon molecular sieve (CMS) membrane was prepared for propylene/propane separation using a phenolic resin as a cost-effective polymer precursor. However, to achieve a desirable separation performance, the pre-treatment process of phenolic resin should be affordably carried out. In this study, novolac phenolic resin was cured with hexamine as a curing agent. The curing conditions were varied in terms of the curing time and concentration of the curing agent, both of which led to a higher degree of crosslinking of the phenolic resin, resulting in improved thermal stability. The propylene/propane separation factor of 6.33 for the CMS membrane derived from the phenolic resin cured for 1 h increased to 18.5 when the curing time was 4 h, whereas the propylene permeance decreased from 153 to 53.5 GPU. A similar trend was observed for higher concentrations of the curing agent. Moreover, the long-term stability of the CMS membrane was significantly improved after prolonged curing with a higher concentration of the curing agent. The CMS membranes derived from cured phenolic resins possess more selective carbon structures and better structural stabilities.