Rajkumar Kore

Synthesis of Dicationic Ionic Liquids and their Application in the Preparation of Hierarchical Zeolite Beta

Piperidine- and imidazole-based dicatoinic ionic liquids have been developed for the synthesis of zeolite Beta. Hierarchical Beta has a larger surface area and pore volume than conventional Beta. Beta derived from a dicationic ionic liquid exhibited remarkably higher catalytic activity than the conventional Beta. Experimental evidence and DFT calculations suggest that only a suitable conformation of such dicationic ionic liquids is able to form zeolite Beta (see scheme).

ZSM‐5 Zeolite Nanosheets with Improved Catalytic Activity Synthesized Using a New Class of Structure‐Directing Agents

A new series of multiquaternary ammonium structure-directing agents, based on 1,4-diazabicyclo[2.2.2]octane, was prepared. ZSM-5 zeolites with nanosheet morphology (10 nm crystal thickness) were synthesized under hydrothermal conditions using multiquaternary ammonium surfactants as the zeolite structure-generating agents. Both wide-angle and small-angle diffraction patterns were obtained using only a suitable structure-directing agent under a specific zeolite synthesis composition. A mechanism of zeolite formation is proposed based on the results obtained from various physicochemical characterizations. ZSM-5 materials were investigated in catalytic reactions requiring medium to strong acidity, which are important for the synthesis of a wide range of industrially important fine and specialty chemicals. The catalytic activity of ZSM-5 materials was compared with that of the conventional ZSM-5 and amorphous mesoporous aluminosilicate Al-MCM-41. The synthesis strategy of the present investigation using the new series of structure-directing agents could be extended for the synthesis of other related zeolites or other porous materials in the future. Zeolite with a structural feature as small as the size of a unit cell (5-10 nm) with hierarchically ordered porous structure would be very promising for catalysis.

Synthesis of hierarchical Beta using piperidine based multi-ammonium surfactants

Hierarchical Beta zeolite was prepared using piperidine based structure directing agents having at least two ammonium groups in their structure. Materials exhibited very high surface area (≈1050 m2 g−1), pore volume (2.7 mL g−1), and catalytic activity hitherto reported in the literature. A density functional theoretical study shows that a suitable special orientation of piperidine rings in the structure directing agents is responsible for the formation of hierarchical Beta.

Synthesis of zeolite Beta, MFI, and MTW using imidazole , piperidine , and pyridine based quaternary ammonium salts as structure directing agents

The synthesis of zeolites is investigated using a variety of quaternary ammonium salts of imidazole, piperidine, and pyridine based structure directing agents. The materials were characterized by a complementary combination of X-ray diffraction, N2-adsorption/desorption, scanning electron microscopy, and transmission electron microscopy. Only suitable quaternary ammonium salts were able to form zeolites Beta, MFI, and MTW. Zeolites (especially Beta) obtained using these quaternary ammonium salts are nanocrystalline in nature and exhibited high surface area and pore volume compared to conventional zeolites. Experimental evidence and density functional theory studies suggest that a limited conformational freedom, provided by the cyclic structure of the quaternary ammonium salts, is an important prerequisite and acts as a structure directing agent for the synthesis of zeolites.

An efficient halometallate ionic liquid functionalized mesoporous ZSM-5 for the reduction of carbon–carbon multiple bonds

Transition metal-containing halometallate ionic liquids (ILs)-based economical catalysts have been developed for the selective reduction of carbon–carbon multiple bonds with hydrazine hydrate in ethanol under mild reaction condition. ILs have been tethered to the surface of mesoporous ZSM-5. The Mn-based halometallate IL tethered to the surface of mesoporous ZSM-5 exhibited the best activity compared to the parent halometallate ILs. It demonstrated efficient recyclability with no appreciable loss in the catalytic activity even after being recycled five times. In order to establish the reaction mechanism, ILs-hydrazine complexes were prepared and investigated in reduction reactions. The structure–activity relationship was established by their catalytic activities, physicochemical characterizations, ILs-hydrazine complex formation, and probe reactions. The catalyst also exhibited excellent activity in the reduction of alkynes to alkanes. This catalytic process demonstrated several key advantages such as mild and convenient reaction condition, low substrate to hydrazine ratio, reusability, and the cost-effectiveness of the catalyst.