Conversion of Naphthenic Hydrocarbons Over Hzm-12 Zeolites - Activity and Selectivity to Light Olefins Depending on Their Acid and Textural Properties and on the Size of the Processed Molecule

Abstract The activity and selectivity to light olefins during conversion of naphthenic hydrocarbons over HZSM-12 zeolites depending on the textural and acid properties and the size of the processed molecule were studied. In Two ZSM-12 zeolites were synthesized under hydrothermal conditions with similar Si/Al ratio. To generate intracrystalline mesoporosity, the synthesized ZSM-12 zeolites, identified as HZ12 and MZ12, were subsequently desilicated by alkaline treatment (AT) generating the hierarchical HZ12-AT and MZ12-AT zeolites. After to obtain their protonic form, the samples were characterized by XRD, SEM, EDS, N2 physisorption, 27Al MAS NMR and NH3-TPD. XRD and N2 sorption measurements confirmed, respectively, that the MTW structure of the ZSM-12 zeolite was preserved and that after the AT occurred an increase in the mesoporous volume, consequently increasing the specific external surface area, besides with an increase in the concentration of weak acid sites in the alkaline treated sample under more severe conditions. The catalytic evaluation shows an increase in the conversion of cyclohexane, methylcyclohexane and ethylcyclohexane over the more mesoporous MZ12-AT zeolite with the yield to light olefins increasing with the increase of the length of the substitutive alkyl group in the naphthenic molecule, being this behavior more pronounced over the MZ12-AT sample.