Anil Kumar Sinha

Structurally stabilized organosilane-templated thermostable mesoporous titania.

Structurally thermostable mesoporous anatase TiO2 (m-TiO2) nanoparticles, uniquely decorated with atomically dispersed SiO2, is reported for the first time. The inorganic Si portion of the novel organosilane template, used as a mesopores-directing agent, is found to be incorporated in the pore walls of the titania aggregates, mainly as isolated sites. This is evident by transmission electron microscopy and high-angle annular dark field scanning transmission electron microscopy, combined with electron dispersive X-ray spectroscopy. This type of unique structure provides exceptional stability to this new material against thermal collapse of the mesoporous structure, which is reflected in its high surface area (the highest known for anatase titania), even after high-temperature (550 °C) calcination. Control of crystallite size, pore diameter, and surface area is achieved by varying the molar ratios of the titanium precursor and the template during synthesis. These mesoporous materials retain their porosity and high surface area after template removal and further NaOH/HCl treatment to remove silica. We investigate their performance for dye-sensitized solar cells (DSSCs) with bilayer TiO2 electrodes, which are prepared by applying a coating of m-TiO2 onto a commercial titania (P25) film. The high surface area of the upper mesoporous layer in the P25-m-TiO2 DSSC significantly increases the dye loading ability of the photoanode. The photocurrent and fill factor for the DSSC with the bilayer TiO2 electrode are greatly improved. The large increase in photocurrent current (ca. 56%) in the P25-m-TiO2 DSSC is believed to play a significant role in achieving a remarkable increase in the photovoltaic efficiency (60%) of the device, compared to DSSCs with a monolayer of P25 as the electrode.

Silica-Immobilized Highly Dispersed Oxo–Rhenium and its Catalytic Activity for the Direct Synthesis of Nitrones

A novel covalently attached silica‐immobilized oxo–rhenium catalyst was prepared by the reaction of perrhenic acid and 3‐chloropropyl functionalized mesoporous SBA‐15, in which the oxo–rhenium species is chemically bonded to the support, preventing leaching. The prepared silica‐immobilized oxo–rhenium was found to be an efficient and recyclable catalyst for the one‐pot condensation/oxidation of aldehydes and primary amines to nitrones in high yields using urea–hydrogen peroxide as a terminal oxidant under mild reaction conditions.

CHAPTER 9:Process Intensification for Hydroprocessing of Vegetable Oil

Hydroprocessing of vegetable oils can be effectively done in microchannel reactors using hydroprocessing catalyst coatings. Hydroprocessing catalysts, Ni–Mo/Al2O3 and Ni–Mo/SiO2–Al2O3, during processing of vegetable oil in a microchannel reactor effectively produced more oligomerized (>C18) and heavy (C15–C18) hydrocarbon products (>95% yield). The naphtha ( 99%) is in the first 50% volume of the microchannel plate. The simulation results indicate better heat and mass transfer inside the microchannel reactor whereas a non-uniform, thermal runaway heat and concentration profile was observed in the fixed-bed reactor, which favors secondary cracking reactions.