M. Jhansi

Bio: M. Jhansi is an academic researcher from Indian Institute of Technology Kanpur. The author has contributed to research in topics: Catalysis & Heterogeneous catalysis. The author has an hindex of 2, co-authored 2 publications receiving 25 citations.

Development of heterogeneous catalyst by ionically bonding macrocyclic Zr–Zr complex to montmorillonite clay for depolymerization of polypropylene

Abstract: The homonuclear macrocyclic Zr–Zr complex was synthesized by reacting 2,6-diformyl-4-methylphenol with 1,2-phenylenediamine and zirconium oxychloride. The heterogeneous complex catalyst was prepared by ionically bonding it on zirconium pillared montmorillonite. The heterogeneous complex catalyst was shown to be stable at the depolymerizing temperature of polypropylene and the reaction product was a waxy solid alone without forming liquid and gaseous material. The FTIR analysis of this solid was shown to have exactly the same IR of the polypropylene indicating that the depolymerization occurs predominately by first formation of polymer radicals by random scission of the polypropylene chain. The chain radical, thus generated, combines with the catalyst to give a radical cation complex and the movement of this along its chain by bond shift reaction produces low molecular waxy product. Experiments have shown that the molecular weight of this waxy product depends upon the reaction temperature as well as the residence time and all its physical properties (melting point and solubility) can be matched with those of the paraffin wax.

Kinetic study of oxidation of cyclohexanol using bimetallic iron–copper macrocyclic complex catalyst

Abstract: Commercial catalysts for oxidation of cyclohexanol to cyclohexanone are known to deactivate at high temperature with time. A macrocyclic FeCu complex covalently bonded to modified alumina support was prepared for oxidation of cyclohexanol using molecular oxygen. The catalyst was shown to be thermally stable and does not deactivate for atleast hundred hours of usage for oxidation of cyclohexanol. The reaction has been carried out using molecular oxygen without any solvent, coreactant or cocatalyst in the temperature range of 125–250 °C at 27 atm. An irreversible first order reaction mechanism has been proposed and optimal rate constants were determined.

Catalytic processing of plastic waste on the rise

Abstract: Summary Approximately 80% of the >350 Mt of plastics produced annually is turned into waste, which equals 30% of the European electricity consumption. Chemocatalytic strategies giving life to fuels, chemicals, and monomers promise to transform plastic pollution, barely addressed by incineration and mechanical recycling, into an opportunity. Under the motto “catalysis generates plastics and should handle their fate,” this review integrates fundamentals and applications of catalytic transformations of seven major plastics. Following algorithmic analysis of >400 articles and patents, it outlines relevant systems for 13 frontrunner routes based on heterogeneous, homogeneous, and biocatalysis. Given the predominance of off-the-shelf catalysts, it stresses transposable state-of-the-art systems of developed fields to foster design of materials. Based on recent system engineering analyses, it highlights more sustainable paths for implementation, unattended by current trends in industry and academia. It closes with a unified view and critical thoughts on research priorities to accelerate progress toward a sustainable plastic economy.

An efficient and one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles catalyzed via solid acid nano-catalyst

Abstract: A simple highly versatile and efficient synthesis of 2,4,5-trisubstituted imidazoles is achieved by three component cyclocondensation of 1,2-dicarbonyl compounds, aldehydes and NH4OAc, as ammonia source using clays, zeolite, nano-crystalline sulfated zirconia (SZ) as catalyst in ethanol at moderate temperature Moreover, the utility of this protocol was further explored conveniently for the one-pot, four component synthesis of 1,2,4,5-tetrasubstituted imidazoles in high yields, short reaction times and milder conditions, easy work-up and purification of products by non-chromatographic methods The catalysts can be recovered for the subsequent reactions and reused without any appreciable loss of their efficiency

Preparation and characterization of mesoporous silica supported cobalt oxide as a catalyst for the oxidation of cyclohexanol

Abstract: Cobalt oxide catalysts supported on mesoporous silica SBA-15 were prepared by the “two-solvent” method and compared with analogous catalysts prepared by the more conventional methods of impregnation and adsorption. Cobalt nitrate was used as the precursor. The catalysts were characterized by N 2 adsorption–desorption, XRD, FTIR, XPS, TPR, ICP-MS, TEM and DR UV–vis. Their activity for the oxidation of cyclohexanol was determined by GC and GC–MS. The effect of metal loading on the morphology and catalytic activity of the catalysts was investigated. The catalyst with the lowest cobalt content exhibited the highest catalytic activity for cyclohexanol oxidation due to the better accessibility of the reactants to the catalytic sites.

Selective hydrogenation of phenol and related derivatives

Abstract: The selective hydrogenation of phenol and related derivatives to cyclohexanone and analogues remains a challenging task. In the present minireview, we highlight the research advances in this field. The first part introduces the significance, pathways and mechanisms of these reactions. The main part summarizes the reactions using different kinds of media (vapor phase, organic solvents, supercritical carbon dioxide, ionic liquids and water) and catalyst systems (non-supported catalysts and supported catalysts with metal oxides, polymers, carbon materials, mesoporous silica, metal–organic frameworks and graphitic carbon nitride etc. as the supports). Then the influence of factors such as the acid–base properties of the support, the chosen promoter and metal precursor, the structure sensitivity and deactivation are discussed in detail. The final section summarizes the kinetic studies.

Selective phenol hydrogenation to cyclohexanone over alkali–metal-promoted Pd/TiO2 in aqueous media

Abstract: Selective phenol hydrogenation to cyclohexanone is an important process in both the chemical industry and renewable feedstock processing. However, the direct hydrogenation of phenol to cyclohexanone at mild conditions remains challenging. Here, we report an easily manufactured catalyst, alkali–metal-promoted Pd/TiO2, achieves 99% phenol conversion and 99% cyclohexanone selectivity at mild conditions of 80 °C and an extremely low H2 pressure of 0.06 MPa in water. By contrast, only about 18–36% phenol conversion is achieved using Pd/TiO2 that without addition of alkali metal at the same conditions. The kinetic studies and TOF values indicate that K or Na metals indeed promote the phenol conversion without changing cyclohexanone selectivity. Further studies suggest that the change of electronic structures over Pd NPs that induced by alkali metal is the main reason for enhanced phenol conversion. This result, combined with DFT calculations, suggest that phenol hydrogenation occurs both along the direct hydrogenation pathway and the dissociation and hydrogenation pathway over Pd/TiO2, and that the main pathway over alkali–metal-promoted Pd/TiO2 catalysts is the dissociation and hydrogenation pathway.