C. S. Swamy

Bio: C. S. Swamy is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Catalysis & Intermetallic. The author has an hindex of 7, co-authored 16 publications receiving 104 citations.

Mossbauer investigation of magnesium ferrite-aluminate

Abstract: The magnesium ferrite-aluminate series MgAlxFe2-xO4 (x=0.2, 0.4 and 0.7) has been synthesised, the lattice constants determined and the applicability of Vegard's law has been tested. The Mossbauer spectra have been recorded from 77K to a temperature well above the Neel point. The Neel temperature decreases linearly with the increase of aluminium concentration. The centre shifts are found to be independent of the aluminium concentration. The Mossbauer spectra have also been recorded at 4.2K in an external magnetic field of 4.2 T applied parallel to the direction of the gamma rays. For x=0.2 the canting of Fe spins is observed only on the A site and the B-site Fe spins have a collinear spin structure. This is the only spinel ferrite where the spin canting has been clearly observed on the A site alone when the B-site Fe spins have a collinear spin structure. For x=0.4 and x=0.7 both A- and B-site Fe ions have a noncollinear spin structure. The distribution of hyperfine fields at the A and B sites has been analysed in terms of supertransferred hyperfine fields from neighbouring ions.

Methylation of pyridine over zeolites

Abstract: Methylation of pyridine was carried out on H-Y, Na-Y, HZSM-5, Mordenite, ZSM-22, SAPO-5, MgAlPO-11 and Zeolite Beta. The major products formed in the gas phase reaction were 2-picoline, 3-picoline and/or 4-picoline along with other alkylated products in certain cases. From the results it was envisaged that the 2-picoline and 4-picoline may be obtained by the Ladenburg rearrangement via N-alkylation whereas the 3-picoline may be obtained by an initial hydrogenation route. The selectivity for the various products varied from one catalyst to the other thereby proving the complexity of the reaction mechanism due to the size and shape effects of the pores in the zeolite matrix.

Kinetics of the alkylation of phenol with methanol over catalysts derived from hydrotalcite-like anionic clays

Abstract: Vapor phase alkylation of phenol with methanol was carried out over catalysts derived from a series of hydrotalcite (HT)-like compounds of the form M(II)Al-HT; where M(II)=Mg, Mn, Co, Ni, Cu and Zn with M(II)/Al atomic ratios of2–5. The kinetic parameters such as rate constant (k), apparent activation energy (Ea) and Arrhenius frequency factor (Ao) for the disappearance of phenol were evaluated employing a power law equation assuming pseudo-first order kinetics. The kinetic parameters were found to be in good agreement with phenol conversion. The existence of the compensation effect between Ea and ln Ao was tested.

Studies on the catalytic decomposition of N2O on rare earth nickelates

Abstract: Decomposition of nitrous oxide has been studied on Ln2NiO4 (Ln=La, Nd or Pr) in the temperature range 380–460°C at 50 and 100 Torr initial pressures of the reactant gas. A multicenter adsorption model has been proposed to explain the observed kinetic behavior.

Reaction of benzyl alcohol over the hydrogen storage intermetallic compound Mg2Cu

Abstract: The reaction of benzyl alcohol over the hydrogen storage intermetallics Mg2Cu was studied in the temperature range of 573–773 K. Benzaldehyde and toluene, the major products, were produced by dehydrogenation and disproportionation reactions, respectively. Anthracene, stilbene and benzyltoluenes were also formed due to benzylation reaction. Since the benzylation course was strongly influenced by shape selectivity considerations, these were produced in minor amounts. Below 673 K, Mg2Cu behaves like metals while above 673 K it behaves like oxide systems in its catalytic properties.

Heterogeneous catalytic decomposition of nitrous oxide

Abstract: An overview is given on the ongoing activities in the area of the decomposition of nitrous oxide, N2O, over solid catalysts. These catalysts include metals, pure and mixed oxides, supported as well as unsupported, and zeolitic systems. The review covers aspects of the reaction mechanism and kinetics, focusing on the role of surface oxygen, the inhibition by molecular oxygen, water and other species, poisoning phenomena and practical developments.

Structure and Reactivity of Perovskite-Type Oxides

Abstract: Publisher Summary This chapter discusses the structure and reactivity of perovskite-type oxides. Perovskite-type oxides have the general formula ABO 3 (A, cation of larger size) and are structurally similar to CaTiO 3 , the mineral that gave its name to that group of compounds. These materials are first studied because of their important physical properties such as ferro-, piezo-, and pyroelectricity, magnetism and electrooptic effects. The most numerous and most interesting compounds with the perovskite structure are oxides. Some hydrides, carbides, halides, and nitrides also crystallize with this structure. The chapter reviews only the study of oxides and their behavior in the gas solid interface and in heterogeneous catalysis. An important characteristic of perovskites, mentioned in the chapter, is their susceptibility of partial substitution in both A and B positions. This provides a wealth of isomorphic compounds that can easily be synthesized. Given the extensive range of possibilities in the tailoring of their chemical and physical properties, there is no doubt that new reactions can be studied, where these oxides can participate as catalytic agents.

Magnetic properties of nanostructured ferrimagnetic zinc ferrite

Abstract: Nanostructured ZnFe2O4 ferrites with different grain sizes were prepared by high energy ball milling for various milling times. Both the average grain size and the root mean square strain were estimated from the x-ray diffraction line broadening. The lattice parameter initially decreases slightly with milling and it increases with further milling. The magnetization is found to increase as the grain size decreases and its large value is attributed to the cation inversion associated with grain size reduction. The Fe-57 Mossbauer spectra were recorded at 300 K and 77 K for the samples with grain sizes of 22 and 11 nm. There is no evidence for the presence of the Fe2+ charge state. At 77 K the Mossbauer spectra consist of a magnetically ordered component along with a doublet due to the superparamagnetic behaviour of small crystalline grains with the superparamagnetic component decreasing with grain size reduction. At 4.2 K the sample with 11 nm grain size displays a magnetically blocked state as revealed by the Mossbauer spectrum. The Mossbauer spectrum of this sample recorded at 10 K in an external magnetic field of 6 T applied parallel to the direction of gamma rays clearly shows ferrimagnetic ordering of the sample. Also, the sample exhibits spin canting with a large canting angle, maybe due to a spin-glass-like surface layer or grain boundary anisotropies in the material.

Catalytic decomposition of nitrous oxide on metal exchanged zeolites

Abstract: The catalytic decomposition of nitrous oxide to nitrogen and oxygen was studied over a number of catalysts. Copper and cobalt exchanged ZSM-5, mordenite, zeolite beta, ZSM-11 and ferrierite are much more active than other cation-exchanged zeolites (Cu-Y, Co-Y, Co-erionite, Cu-L, Co-L, Ni-ZSM-5, Mn-ZSM-5) and metal oxides (CuO/Al2O3, and CoO/Al2O3). For noble metal catalysts, a cation exchanged ZSM-5 has higher activity than the Al2O3 supported form. Rhodium is the most active catalyst, but surprisingly Pt-ZSM-5 is one of the least active catalysts of all. Also, the effects of oxygen and nitric oxide addition, metal loading, and pretreatment upon the catalyst activity were evaluated.

Adsorption of Carbon Dioxide onto Hydrotalcite-like Compounds (HTlcs) at High Temperatures

Abstract: The adsorption capacities of carbon dioxide on six commercial hydrotalcite-like compounds and the main factors (aluminum content, anion type, water content, and heat treatment temperature) influencing their adsorption capacity at high temperatures have been investigated using a gravimetric technique. There is an optimum aluminum content and heat treatment temperature for the adsorption capacity. The carbonate anion favors adsorption of carbon dioxide compared to OH-, and a low content of water also improves the adsorption capacity. The carbon dioxide adsorption capacity is mainly dependent on the microporous volume, interlayer spacing, and layer charge density of the hydrotalcite-like compounds.