Nickel-doped small pore zeolite bifunctional catalysts: A way to achieve high activity and yields into olefins

• Design of bifunctional Ni-zeolites.
• Optimization of Ni introduction methology in FER zeolite.
• Ni-HFER zeolite led to a raise in the catalytic activity for both n-hexane and isobutane cracking.

The present study deals with the modification of mordenite (HMOR) and ferrierite (HFER) zeolites by nickel. XRD, XRF, nitrogen adsorption, TPR, XANES, EXAFS were used to thoroughly characterize the materials. The metal level was set to 1 wt% for all catalysts and nickel was introduced by cationic exchange following either conventional thermal heating or in the presence of microwave radiation (HFER). The metal exchange methods employed ensured to maintain the structural integrity of the zeolites. However nickel was predominantly distributed as small NiO particles on HFER for both catalysts. The rate of both n-hexane and isobutane cracking increased when nickel was introduced under microwave radiation for HFER zeolite. Likewise, the selectivity toward ethylene and propylene was enhanced by nickel presence in n-hexane cracking reaction, while no effect on selectivity was observed in isobutane cracking. These results confirm that a new bifunctional system was obtained, since both metallic and Brønsted acid sites are acting in a synergetic manner within the zeolite catalyst.

Addition of nickel to HZSM-5 increases remarkably the selectivity to ethylene and the catalysts’ catalytic activity when compared to the pristine HZSM-5. The ethylene is produced through β-scissions processes from oligomeric carbenium ions formed during the process.Figure optionsDownload high-quality image (81 K)Download as PowerPoint slide