Sounak Roy

Role of solvents on photocatalytic reduction of nitroarenes by sol–gel synthesized TiO2/zeolite-4A

Photocatalytic valorization of harmful pollutants like nitroarenes to important intermediates like aminoarenes has been carried out with the help of TiO2 supported zeolite-4A catalyst, synthesized by polymerizable sol–gel route. A series of solvents such as water, primary and secondary alcohols have been studied for their role on photocatalytic reduction. The reduction of nitrobenzene has been found to be faster compared to that of 4-nitrophenol. The rate of reduction of nitrobenzene is independent of the type of alcohol, whereas the reduction rate of 4-nitrophenol is faster with primary alcohol compared to secondary alcohol. Reduction of 4-nitrophenol has been found to exhibit alcohol concentration dependency and the rate of reduction is dependent on initial concentration of substrate.

Structure sensitive photocatalytic reduction of nitroarenes over TiO 2

It is a subject of exploration whether the phase pure anatase or rutile TiO2 or the band alignment due to the heterojunctions in the two polymorphs of TiO2 plays the determining role in efficacy of a photocatalytic reaction. In this work, the phase pure anatase and rutile TiO2 have been explored for photocatalytic nitroarenes reduction to understand the role of surface structures and band alignment towards the reduction mechanism. The conduction band of synthesized anatase TiO2 has been found to be more populated with electrons of higher energy than that of synthesized rutile. This has given the anatase an edge towards photocatalytic reduction of nitroarenes over rutile TiO2. The other factors like adsorption of the reactants and the proton generation did not play any decisive role in catalytic efficacy.

Surface morphology and active sites of TiO2 for photoassisted catalysis

The main aim of this work is to discriminate the closely related adsorption and catalytic degradation processes that occur during a photocatalytic reaction. Very high-surface-area TiO2 and Pd-doped TiO2 were synthesized by microwave-assisted hydrothermal synthesis and used for degradation of methylene blue as a model pollutant dye. Thorough structural, morphological, and surface analyses of the synthesized catalysts were conducted to investigate key material properties that influence adsorption and catalytic performance. The adsorption capacity of the catalysts was determined by fitting adsorption data using the Langmuir isotherm model, and the photocatalytic activity of the synthesized samples was evaluated by periodically measuring the concentration of methylene blue as it was photocatalytically degraded under ultraviolet (UV) light. The results indicated that noble-metal incorporation compromised adsorption but favored catalytic performance.

A novel microwave-assisted hydrothermal route for the synthesis of ZnxTPA/γ-Al2O3 for conversion of carbohydrates into 5-hydroxymethylfurfural

Energy-efficient and sustainable processes for the production of 5-hydroxymethylfurfural (HMF) from carbohydrates are in high demand. Bivalent ion-exchanged microwave-synthesized ZnxTPA/γ-Al2O3 was employed for the direct conversion of carbohydrates into HMF. The as-synthesized samples were structurally characterized by FTIR and Raman spectroscopy, UV-Vis diffused reflectance spectroscopy, and X-ray diffraction. Thermal characterization was performed by TG-DTA. The surface morphology was analysed by FE-SEM, and surface area analysis was performed. The surface acidities of the as-synthesized catalysts were elucidated by pyridine FTIR spectra and NH3-TPD. The catalytic performance was thoroughly studied as a function of Zn2+ doping, reaction temperature, catalysts loading, and effect of solvents. Microwave-synthesized Zn0.5TPA/γ-Al2O3 exhibited excellent catalytic fructose dehydration, with 88% HMF yield at 120 °C for 2 h. The surface Bronsted acidity was found to be crucial for optimum catalytic activity.