Benzene reduction in gasoline range streams by adsorption processes using a PVDC–PVC carbon molecular sieve

A PVDC–PVC derived carbon molecular sieve (CMS-IMP12) was used for adsorbing the benzene contained in a sample of reforming gasoline from a Mexican Refinery. First an olefin free benzene enriched fraction (H-BHC) was obtained by distillation-hydrogenation. The adsorption process may be carried out in one and two-steps. In the one-step procedure, benzene was adsorbed along other hydrocarbons in a 28 mL/100gads yield. The benzene enriched fraction (BEF) contained linear and branched paraffins and cycloparaffins (56%) and benzene (43%). In the two-step procedure, linear paraffins (PEF) were selectively separated from the H-BHC by 5A molecular sieve (7 mL/100gads). Then, the paraffins free fraction (PFF, 30 mL/100gads) was submitted to a further separation using the CMS material. The resulted adsorbed product (BEF, 42 mL/100gads) was formed mainly by iso- and cycloparaffins (50%) and benzene (48%). The octane number of the one-step was lower than the two-steps benzene free fraction (BFF) (67 and 76, respectively) due to the presence of paraffins in the first one. In any case, the benzene may be recuperated from the BEF by distillation and the octane number of the recovered PEF and BFF may be improved by any commercial isomerization process.