Ch. Ramesh Kumar

Samarium-exchanged Heteropoly Tungstate: An Efficient Solid Acid Catalyst for the Synthesis of Glycerol Carbonate from Glycerol and Benzylation of Anisole

Samarium‐exchanged heteropoly tungstate (SmxTPA) is an efficient catalyst for the synthesis of glycerol carbonate from glycerol and urea. The catalysts with varying Sm content were prepared and characterized by FT‐IR spectroscopy, XRD, laser Raman spectroscopy, temperature‐programmed desorption of ammonia, and X‐ray photo electron spectroscopy. The activity of the catalysts is related to the Lewis and Brønsted acidity, which depends on the Sm content in the catalysts. Partially exchanged SmxTPA catalyst showed high activity, owing to a higher number of Lewis acidic sites. The catalyst exhibited consistent activity and selectivity during recycling. A plausible reaction mechanism is presented. The catalyst also exhibited high activity in the acid‐catalyzed benzylation of anisole.

Incorporation of Zn2+ ions into the secondary structure of heteropoly tungstate: catalytic efficiency for synthesis of glycerol carbonate from glycerol and urea

Zinc exchanged heteropoly tungstate (ZnxTPA) catalysts were prepared and characterized by FT-IR, X-ray diffraction, Laser Raman spectroscopy, temperature programmed desorption of ammonia and pyridine adsorbed FT-IR spectroscopy. The activity of the catalysts was evaluated for the carbonylation of glycerol using urea as a carbonylating agent. ZnxTPA catalysts showed high activity for glycerol carbonate synthesis compared to the parent TPA. The activity of ZnxTPA catalysts depended on the number of Zn2+ ions in the secondary structure of heteropoly tungstate. Catalysts with partial exchange of Zn with the protons of TPA (Zn1TPA) exhibited high activity towards glycerol carbonate synthesis. Exchange of protons of TPA with Zn2+ ions resulted in generation of Lewis acidic sites. The changes in surface and structural properties of Zn1TPA catalysts with change in calcination temperature were also evaluated. The catalytic activities of ZnxTPA catalysts were explained based on the variation in their properties. Reaction conditions such as reaction temperature, catalyst weight and glycerol to urea ratio were also optimized.

Efficient solid acid catalysts for esterification of free fatty acids with methanol for the production of biodiesel

12-Tungstophosphoric acid (TPA) with varying contents supported on SnO2 catalysts was prepared and their efficacy as solid acid catalysts for the esterification of palmitic acid with methanol was investigated. The catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), temperature programmed desorption (TPD) of NH3, Laser Raman, Brunner–Emmett–Teller (BET) surface area and scanning electron microscopy (SEM) techniques. The esterification activity depends on the amount and dispersion of TPA on SnO2 which in turn relates to the amount of acidity. Among the catalysts, 15 wt% TPA/SnO2 was the most promising one with the highest fatty acid conversion. Further, reaction parameters such as catalyst concentration, methanol to palmitic acid mole ratio and reaction temperature were also optimized. The catalyst was recycled and reused with consistent activity. A pseudo first order model was applied to correlate the experimental kinetic data and kinetic parameters were evaluated. The activation energy of the catalysts is comparable to that of mineral acids and lower than usual solid acid catalysts.

Adsorption of croconate dyes on TiO2 anatase (101) surface: A periodic DFT study to understand the binding of diketo groups#

AbstractThe adsorption of model croconate dyes on the stoichiometric TiO2 anatase (101) surface has been studied by means of periodic density functional calculations to understand the adsorption of the diketo (-COCO-) groups. Past experimental and theoretical results have shown the strong binding ability of the acid group (-COOH) to the TiO2 surface but here the theoretical studies predicts the binding strength of the diketo group to be also significant and comparable with that of the -COOH group. This may cause a competitive binding between the keto groups and the acid groups on the TiO2 surface in the case of croconate dyes and cause a reduction in the efficiency of the DSSC. Graphical AbstractAdsorption of diketo groups of model croconates in bidentate bridging fashion on the TiO2 anatase (101) surface has binding energy of 23.2 kcal/mol and 28.7 kcal/mol which is competitive to the carboxylic acid binding. There is a decrease in charge transfer to the TiO2 due to the biradical nature of the molecules leading to lesser efficiency.