Thorikul Huda

Novel sulphated zirconia pillared clay nanoparticles as catalyst in microwave assisted conversion of citronellal

Preparation of novel sulphated zirconia pillared montmorillonite and saponite clays nanoparticles (SZ/MMT and SZ/SAP) were studied to find a highly active, economist and environment friendly catalysts in the conversion of citronellal into menthol. Sulphated zirconia pillared MMT was prepared by direct sulphation into zirconia pillared MMT, which is a new and fast technique. Comparative study also conducted by evaluating the activity of SZ/MMT with sulphated zirconia nanoparticle (SZ). Material characterisation was performed by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, scanning electron microscope and also surface acidity by mean pyridine adsorption Fourier transform infrared analysis and total acidity by butylammine titration. Catalytic activity of both SZ/MMT and SZ/SAP was observed in a reaction of citronellal conversion. The operation parameters consist of technique of reaction; tandem cyclisation–hydrogenation and catalytic hydrogen transfer mechanism were investigated. The results show that the pore size of catalyst and the presence of surface acidity affect significantly to increase the isomerisation as well as hydrogenation mechanism. The catalytic hydrogen transfer over microwave irradiation was observed as the more efficient process compared to the tandem cyclisation–hydrogenation from the selectivity of the product and also the other factor influencing the surface mechanism. In another aspect, the results clearly indicated the reusable properties of the sulphated zirconia pillared clay catalysts under varied conditions. Correlation between physicochemical characters and the reaction mechanism is discussed in this study.

Preparation and Characterization of Ni/Zr-Saponite as Catalyst in Catalytic Hydrogen Transfer Reaction of Isopulegol

World demand on menthol is so high and it is also a chalenge for organic synthetic chemist to develop new method of synthesis and conversion from another sources. Tandem cyclization-hydrogenation reaction towards citronellal is one important mechanism recently. Within the mechanism, hydrogenation of isopulegol is rate determining step. Considering green chemistry principles, this research deals with the use of heterogeneous catalyst in hydrogenation, Nickel (Ni) and also the use of microwave assisted organic synthesis method. An effort to improve activity and reusability of nickel in the reaction was conducted by dispersion in pillared clay materials, Ni-saponite.Nickel immobilized zirconia pillared saponite (Ni/Zr-Saponite) was prepared using pillarization-impregnation method. The composite, Zr-Saponite and Saponite were characterised by Scanning Electron Microscopy-energy dispersive x-ray (SEM-EDX), x-ray diffraction (XRD), surface acidity and surface area parameter based on nitrogen adsorption-desorption method. Catalytic hydrogen transfer of isopulegol hydrogenation was used as reaction model to show the comparison of catalytic activity.The XRD and SEM-EDX results of the composite indicate that zirconia was successfully distributed as pillar and nickel was dispersed within the pillared material. Both modifications increased the specific surface area, pore volume and surface acidity as a result of pillar formation and homogeneous distribution of the particles. Compared to raw saponite and Zr-Saponite, the composite exhibits significant improvement on total conversion of isopulegol. The presence of nickel affect the hydrogenation mechanism as showed by the product of menthol by catalytic hydrogen transfer.

Effect of Sulfation on Zirconia-Pillared Montmorillonite to the Catalytic Activity in Microwave-Assisted Citronellal Conversion

Preparation of sulfated zirconia-pillared montmorillonite was carried out in two steps; zirconia pillarization and sulfation to zirconia-pillared montmorillonite. The prepared materials were characterized by using X-ray diffraction (XRD), measurement of the specific surface area, total pore volume and pore size distribution by the N2 adsorption method, scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and surface acidity determination by using pyridine adsorption-FTIR analysis. The activity of the materials as catalysts was evaluated for a microwave-assisted conversion of citronellal. The results showed that the prepared materials had a physicochemical character that promoted high catalytic activity to convert citronellal. From varied Zr content and study of the effect of sulfation on the activity, it was found that Zr content and sulfation increase the surface acidity of the material as shown by the higher total conversion and tendency to produce menthol as a product of the tandem cyclization-hydrogenation mechanism.