I. Suryanarayana

An efficient reusable silver-exchanged tungstophosphoric acid heterogeneous catalyst for solvent-free intermolecular hydroamination of alkynes

Hydroamination of alkynes with both aromatic and aliphatic amines proceeds efficiently in the presence of silver-exchanged tungstophosphoric acid (AgTPA) catalyst under solvent-free conditions to afford ketimines in excellent yields.

A Comparison of Structure and Catalytic Functionality of 12-Molybdophosphoric Acid and Its Ammonium Salt in the Ammoxidation of 2-Methylpyrazine to 2-Cyanopyrazine

Two series of catalysts have been prepared by calcination of 12-molybdophosphoric acid or its ammonium salt at various temperatures, in the region of 300–500 °C. The catalysts have been characterized by nitrogen adsorption, XRD, FTIR spectroscopy and TG/DTA analysis to delineate changes in the solid phase associated with high-temperature treatment. Ammoxidation of 2-methylpyrazine has been carried out on these catalysts in a continuous, vapor phase, fixed-bed reactor, in the reaction temperature range of 360–420 °C. The used catalysts have also been subjected to characterization to ascertain the extent of formation of the salt from its decomposition products. The ammonium salt has shown higher activity, selectivity and better stability, when compared with its parent acid, up to a calcination temperature of 450 °C. However, at temperatures higher than the decomposition temperature the activity of the salt decreases considerably, possibly due to the formation of an undesired species mediated by Mo in the reduced state, thus setting a limit to the calcination temperature.

Studies on microwave irradiated Pd/Nb2O5 catalysts: Effect of palladium chloride precursor on the chlorobenzene hydrodechlorination activitya

Catalysts containing 10 wt. % Pd supported on Nb2O5 were prepared by microwave irradiation and conventional electrical heating, using palladium chloride as the precursor for Pd. Whereas higher residual chloride content decreased the activity and stability of the microwave irradiated catalyst, formation of PdO during calcination in air improved the performance of the conventionally heated catalyst. Calcination after microwave irradiation offers the highest activity and stability.

In situ synthesis by salt–surface interaction and the catalytic functionality of the ammonium salt of 12-tungstophosphoric acid

The ammonium salt of 12-tungstophosphoric acid, with the Keggin structure, has been synthesized in situ on niobium phosphate (NbP) by salt–surface interaction; the catalyst exhibits high selectivity to benzaldehyde in the vapor phase air oxidation of benzyl alcohol.

In Situ Synthesis of the Ammonium Salt of 12-Molybdophosphoric Acid on Niobium Phosphate by Salt-Surface Interaction: The Ammoxidation Functionality of the Catalyst in the Transformation of 2-Methylpyrazine to 2-Cyanopyrazine

The ammonium salt of 12-molybdophosphoric acid (AMPA) has been synthesized, in situ, on niobium phosphate by interacting the phosphate of the support with the molybdenum of the salt. The formation of AMPA, with the popular Keggin structure, is confirmed by X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. The in situ synthesized catalysts exhibited higher ammoxidation activity than the bulk AMPA, showing optimum conversion at 10 wt% Mo loading. The selectivity to nitrile increased with increasing loading.

Interaction-induced enhancement in the activity and selectivity of a titania-supported ammonium salt of a 12-molybdophosphoric acid catalyst during ammoxidation of 2-methylpyrazine.

A titania-supported ammonium salt of 12-molybdophosphoric acid has been synthesized, and the salt-support interaction, which enhanced the reaction rate, has been correlated with the activity of the catalyst in the ammoxidation of 2-methylpyrazine.