P. Kanta Rao

New type of carbon coated alumina supports for the preparation of highly ctive ruthenium catalysts for ammonia synthesis

In the present work advantage is taken of the beneficial property of carbon, i.e. the electron transport capacity of the graphite lattice, the ionic alkali promoter and the stability of the classical support, Al 2 O 3 , in the preparation of new ammonia synthesis catalysts based on ruthenium. Two carbon-coated aluminas were used as supports for the preparation of the catalysts

Influence of MoO3 and WO3 on the dispersion and activity of V2O5 in vanadia-silica catalysts

Abstract A series of silica-supported vanadia and molybdenum- and tungsten-promoted vanadia catalysts have been prepared and were characterized by means of low temperature oxygen chemisorption, 1 H magic angle spinning nuclear magnetic resonance, X-ray diffraction, and electron spin resonance techniques. Reactivities of these catalysts for partial oxidation of methanol were also determined under atmospheric pressure in a flow microreactor. These results suggest the formation of the “patchy monolayer” phase of V oxide at lower loadings and on top of it bulk V 2 O 5 at higher vanadium loadings. The presence of molybdenum increases the activity of the catalyst, whereas tungsten has the opposite effect. The improved activity of molybdena-vanadia catalyst was related to the better dispersion of the V oxide phase in the presence of Mo on silica surface.

ESCA characterization of copper/alumina catalysts prepared by deposition — precipitation using urea hydrolysis

Abstract X-ray photoelectron spectroscopy (XPS) has been used for the characterization of Cu/Al2O3 catalysts used for the dehydrogenation of ethanol and also for carbon monoxide adsorption studies. Various oxidation states of copper in oxidic and hydrogen-reduced catalysts have been identified using Cu(2p 3 2 ) photoelectron and Cu(LMM) Auger transitions. The Cu(2p3/2)/Al(2p) intensity ratio from XPS data can be correlated with the copper surface area, CO adsorption capacity and reaction rate of the catalyst.

Preparation of catalytically active γ-Al2O3 from a basic aluminium succinate precursor precipitated from homogeneous solution

A rapid method for making γ-alumina is described. Basic aluminium succinate and bayerite, precursors of γ-alumina, were prepared by precipitation from homogeneous solutions of aluminium chloride with and without succinic acid by urea hydrolysis at 90–95°C. The identification of basic aluminium succinate was confirmed by its infrared (IR) and nuclear magnetic resonance (NMR) spectra. The effect of the calcination temperature on the crystallographic phase, crystallite size, surface area, pore volume, mean pore radius and the acid strength distribution of these aluminas was investigated. Well crystallized γ-alumina could be obtained by calcining basic aluminium succinate at 870°C for 5 h, whereas bayerite under similar conditions yielded θ-alumina. Active aluminas prepared from basic aluminium succinate have comparatively higher surface areas than those made from bayerite. Scanning electron microscope (SEM) studies of γ-alumina made from basic aluminium succinate show that the particles are microspheroidal in shape. The activity of these aluminas for dehydration of ethanol was comparable to that of commercial alumina.

Titration of active sites for partial oxidation of methanol over V2O5/SnO2 and MoO3/SnO2 catalysts by a low-temperature oxygen chemisorption technique

Abstract The amount of oxygen chemisorbed at − 78°C on V 2 O 5 /SnO 2 and MoO 3 /SnO 2 catalysts has been found to correlate directly with the conversion of methanol at 175°C. These catalysts have shown high selectivity for the formation of formaldehyde, selectivities being over 95% for V 2 O 5 /SnO 2 and ca. 90% for MoO 3 /SnO 2 .

Measurement of surface dispersion of ruthenium on γ-Al2O3 support by low-temperature oxygen chemisorption (LTOC) technique

Presentation des resultats de la mesure de la dispersion du ruthenium sur la surface de lalumine par la technique de la chimisorption de loxygene a -78°C. Ces valeurs sont comparees a celles obtenues par chimisorption dhydrogene a la temperature ambiante.

Characterization of MoO3TiO2 catalysts by 1H magic-angle-spinning NMR spectroscopy☆

Abstract 1H MAS NMR spectra of molybedenum oxide catalysts supported on anatase and rutile polymorphs of TiO2 reveals the presence of two types of OH groups (acidic and basic) on the surface of TiO2.

Solid-state 27Al and cross-polarization 13C magic-angle spinning nuclear magnetic resonance characterisation of aluminas derived from basic aluminium succinate

Solid-state 27Al and cross-polarization (CP) 13C magic-angle spinning nuclear magnetic resonance (MAS NMR) was used to characterise aluminas obtained by calcining basic aluminium succinate at different temperatures. In basic aluminium succinate, aluminium is in the tetrahedral coordination only. However, in both X-ray amorphous and gamma-aluminas aluminium is in the tetrahedral and octahedral coordination. The intensity of the aluminium peaks is at a maximum for samples calcined at 700 degrees C. 13C CP MAS NMR indicates the bonding of Al with carbon of the carboxylate group in basic aluminium succinate. Samples calcined at 400-870 degrees C do not give 13C spectra.