Preparation of coconut shell-based carbon molecular sieves for air separation by pressure swing adsorption

A novel process for preparation of a carbon molecular sieve (CMS) was proposed. With coconut shell char as a carbon precursor and phenol formaldehyde resin (PF) as a binder, the process consists of a series of stages, i. e., forming, carbonization, activation with steam, and two-step chemical vapor deposition with benzene as a carbon source. The CMS has been used as an adsorbent in pressure swing adsorption (PSA) of air for N₂ production. The evaluation method of CMS based on PSA was developed by introducing a couple of analysis items including the amount of the effluent desorption gas in PSA and the O₂ concentration in it. In this way, the development of the effective volume and size of the micropores of CMS during the preparation stages could be followed and controlled on purpose. The coconut shell-based CMS prepared by this method has a superior compressive strength and a comparable PSA performance to those commercial CMSs.