Preparation of carbon molecular sieves from macadamia nut shells

In this paper, we present a new approach in the preparation of carbon molecular sieves (CMS). Samples of CMS were prepared from macadamia nut shells by a sequence of three stages. First, activated carbon samples were produced by pyrolysis followed by physical activation with carbon dioxide. They were then treated with coke deposition via benzene thermal cracking. It was found that coke deposition in this step occurred mainly at the pore mouths of micropores, leaving most of the pore interior unchanged. The coke deposition process was allowed to proceed until all micropores became inaccessible to nitrogen molecules, resulting in very low BET surface area, contributed mainly by the meso- and macropores. In the third stage, we subjected these samples to an additional activation step, which was necessary to refine the opening of the pore mouth. The CMS samples prepared by this method have a micropore volume of the order of 0.19 cc/g, compared to 0.24 cc/g of the original base activated carbon. They are capable of separating CS2 from iso-C5H12, the molecular diameters of which are 3.7 and 4.9 Angstrom, respectively.