Sugunan, S; Benny, Thomas(Indian Journal of Chemistry, February , 1995)
[+]
[-]
Abstract:
The Setschenow parameter and thermodynamic
parameters of transfer of 2- and 4- hydroxybenzoic acids
from water to salt solutions have been reported. The data
have been rationalised by considering the structure
breaking effects of the ions of the salts, the localized
hydrolysis model, the internal pressure theory and the
theory of water structure due to Symons.
The Setschenow parameter and thermodynamic parameters of transfer of 2-, 3-, and 4-methylbenzoic acids
from water to salt solutions have been reported. The data have been rationalized by considering the structure breaking
effects of the ions of the salts, the localized hydrolysis model, and the internal pressure theory.
Sugunan, S; Benny, Thomas(Journal of Solution Chemistry, 1994)
[+]
[-]
Abstract:
The Setschenow parameter and thermodynamic parameters of transfer of
2-, 3- and 4-fluorobenzoic acid from water to salt solution are reported.
The data have been rationalized by considering the structure breaking effects of the ions of the salts, the localized hydrolysis model and the internal
pressure theory.
Sugunan, S; Anantaraman, R(Indian Journal of Chemistry, December , 1982)
[+]
[-]
Abstract:
Kinetics of mercuric chloride catalysed solvolysis of l-butyl
chloride, benzyl chloride. p-methylbenzyl chloride, l-phenylethyl
chloride and triethylcarbinyl chloride have been studied in aq.
DMSO, aq. acetonitrile and aq. ethanol. The kinetic data fit a second
order rate equation in aq. DMSO. The calculated values of the
second order rate coefficients increase in the case of aq. acetonitrile
and aq. ethanol. The order in catalyst in 95%(v/v) aq. DMSO is less
than unity.
Nishamol, K; Rahna, K S; Sugunan, S(Elsevier, 2004)
[+]
[-]
Abstract:
Various compositions of chromium manganese ferrospinels were tested as catalysts for the vapour phase alkylation of aniline with methanol. The samples were prepared by room temperature co-precipitation technique and characterized by various physico-chemical methods. The acidity–basicity determination revealed that the samples possess greater amount of basic sites than acidic sites. All the ferrite samples proved to be selective and active for N-monoalkylation of aniline leading to N-methyl aniline; Cr0.6Mn0.4Fe2O4, Cr0.8Mn0.2Fe2O4 and CrFe2O4 exhibited cent percent selectivity for N-methyl aniline. Neither C-alkylated products nor any other side products were detected for all catalyst samples. The catalytic activity of the samples studied in this reaction is related to their acid–base properties and also on the cation distribution. Under the optimized reaction conditions all the systems showed constant activity for a long duration.
Iron and mixed iron aluminium pillared montmorillonites prepared by partial hydrolysis method was subjected to room temperature exchange with transition metals of the first series. The materials exhibit good structural as well as thermal stability. Exchanged metals were found to be present inside the porous network, in the environs of the pillars. Mixed pillaring resulted in the intercalation of Al 13 like polymers in which Al is partially substituted by Fe. The acidic structure was followed by temperature programmed desorption of ammonia and cumene cracking test reaction. Weak and medium sites overshadow the strong sites in all systems. However, exchange with metals increases the number of strong sites. The prepared materials are efficient catalysts for gas phase MTBE synthesis. The catalytic activity can be well correlated with the total amount of weak and medium acid sites.
Sreekumar, K; Raja, T; Kiran, B P; Sugunan, S; Rao, B S(Elsevier, 1999)
[+]
[-]
Abstract:
The reaction of aniline with methanol was carried out over Zn1-xNixFe2O4 (x= 0, 0.2, 0.5, 0.8 and 1) type systems in a
fixed-bed down-flow reactor. It was observed that systems possessing low ``x'' values are highly selective and active for mono
N-alkylation of aniline leading to N-methyl aniline. Selectivity for N-methyl aniline over ZnFe2O4 was more than 99% under
the optimized reaction conditions. Even at methanol to aniline molar ratio of 2, the yield of N-methyl aniline was nearly
55.5%, whereas its yield exceeded 67% at the molar ratio of 7. The Lewis acid sites of the catalysts are mainly responsible for
the good catalytic performance. Cation distribution in the spinel lattice influences their acido-basic properties, and hence,
these factors have been considered as helpful to evaluate the activity and stability of the systems.
Sreekumar, K; Jyothi, T M; Talawar, M B; Kiran, B P; Rao, B S(Elsevier, 2000)
[+]
[-]
Abstract:
A series of ferrites having the general formula Zn1-xCoxFe2O4 (x=0, 0.2, 0.5, 0.8 and 1.0)were prepared by soft
chemical route. The materials were characterized by adopting various physico-chemical methods. The reaction of aniline
with methanol was studied in a fixed-bed reactor system as a potential source for the production of various methyl anilines.
It was observed that systems possessing low ‘ x’ values are highly selective and active for N-monoalkylation of aniline
leading to N-methylaniline. Reaction parameters were properly varied to optimize the reaction conditions for obtaining
N-methylaniline selectively and in better yield. Among the systems Zn0.8Co0.2Fe2O4 is remarkable due to its very high
activity and excellent stability. Under the optimized conditions N-methylaniline selectivity exceeded 98%. Even at a
methanol to aniline molar ratio of 2, the yield of N-methylaniline was nearly 50%, whereas its yield exceeded 71% at the
molar ratio of 5. ZnFe2O4, though executed better conversion than Zn0.8Co0.2Fe2O4 in the initial period of the run,
deactivates quickly as the reaction proceeds. The Lewis acidity of the catalysts is mainly responsible for the good
performance. Cation distribution in the spinel lattice influences their acido-basic properties and, hence, these factors have
been considered as helpful parameters to evaluate the activity of the systems.
Rare earth metal ion exchanged (La3+, Ce3+, RE3+) KFAU-Y zeolites were prepared by simple ion-exchange methods and have
been characterized using different physico-chemical techniques. In this paper a novel application of solid acid catalysts in the dehydration/
Beckmann rearrangement of aldoximes; benzaldoxime and 4-methoxybenzaldoxime is reported. Dehydration/Beckmann
rearrangement reactions of benzaldoxime and 4-methoxybenzaldoxime is carried out in a continuous down flow reactor at
473K. 4-Methoxybenzaldoxime gave both Beckmann rearrangement product (4-methoxyphenylformamide) and dehydration product
(4-methoxybenzonitrile) in high overall yields. The difference in behavior of the aldoximes is explained in terms of electronic
effects. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows
nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream studies show a fast decline in the
activity of the catalyst due to neutralization of acid sites by the basic reactant and product molecules.
Sugunan, S(Indian Journal of Chemistry, February , 1983)
[+]
[-]
Abstract:
Solubilities of 4-nitrobenzoic acid at 25°, 35° and 42°C have
been determined in water and in the presence of several concentrations
of electrolytes. The free energies, enthalpies and entropies
of transfer are also reported. The data have been rationalized
by considering the structure-breaking effects of the ions of
the salts and the requirement of the localized hydrolysis model.
The theory of Symons is not satisfactory to rationalise the
experimental data.
Rice husk silica was utilized as the promoter of ceria for preparing supported vanadia catalysts. Effect of vanadium content was investigated with 2–10 wt.% V2O5 loading over the support. Structural characterization of the catalysts was done by various techniques like energy dispersive X-ray (EDX), X-ray diffraction (XRD), BET surface area, thermal analysis (TGA/DTA), FT-infrared spectroscopy (FT-IR), UV–vis diffused reflectance spectroscopy (DR UV–vis), electron paramagnetic spectroscopy (EPR) and solid state magnetic resonance spectroscopies (29Si and 51V MASNMR). Catalytic activity was studied towards liquid-phase oxidation of benzene. Surface area of ceria enhanced upon rice husk silica promotion, thus makes dispersion of the active sites of vanadia easier. Highly dispersed vanadia was found for low V2O5 loading and formation of cerium orthovanadate (CeVO4) occurs as the loading increases. Spectroscopic investigation clearly confirms the formation of CeVO4 phase at higher loadings of V2O5. The oxidation activity increases with vanadia loading up to 8 wt.% V2O5, and further increase reduces the conversion rate. Selective formation of phenol can be attributed to the presence of highly dispersed active sites of vanadia over the support.
Ramankutty, C G; Sugunan, S; Bejoy, Thomas(Elsevier, September 9, 2002)
[+]
[-]
Abstract:
Preparation of simple and mixed ferrospinels of nickel, cobalt and copper and their sulphated analogues by the room temperature coprecipitation method yielded fine particles with high surface areas. Study of the vapour phase decomposition of cyclohexanol at 300 °C over all the ferrospinel systems showed very good conversions yielding cyclohexene by dehydration and/or cyclohexanone by dehydrogenation, as the major products. Sulphation very much enhanced the dehydration activity over all the samples. A good correlation was obtained between the dehydration activities of the simple ferrites and their weak plus medium strength acidities (usually of the Brφnsted type) determined independently by the n-butylamine adsorption and ammonia-TPD methods. Mixed ferrites containing copper showed a general decrease in acidities and a drastic decrease in dehydration activities. There was no general correlation between the basicity parameters obtained by electron donor studies and the ratio of dehydrogenation to dehydration activities. There was a leap in the dehydrogenation activities in the case of all the ferrospinel samples containing copper. Along with the basic properties, the redox properties of copper ion have been invoked to account for this added activity.
Sunajadevi, K R; Sugunan, S(Elsevier, September , 2005)
[+]
[-]
Abstract:
Titania, sulfated titania and chromium loaded sulfated titania were prepared by sol–gel method and characterized using different technique. Phenol is nitrated regioselectively by nitric acid using chromium loaded sulfated titania catalysts. A remarkable ortho selectivity is observed in solid state nitration to yield exclusively ortho-nitrophenol. Compared to the conventional process, phenol nitration over solid acid catalyst is a clean and environment friendly process. Catalytic activity well correlates with the Brönsted acid sites of these catalysts.
Sugunan, S; Rahna, K S(Indian Journal of Chemistry, July , 2002)
[+]
[-]
Abstract:
The incorporation of transition metal oxide pillars such as those of iron and chromium along with Al2O3, pillars within
the interlayers of a montmorillonite clay is investigated. The surface acidity of these catalysts has been evaluated for the first
time employing the equilibrium adsorption of an electron donor, perylene, and the results are compared with those obtained
by temperature programmed desorption of ammonia. The principle is based on the ability of a catalyst surface site to accept
a single electron from an electron donor like perylene to form charge transfer complexes and the amount of adsorbed species
is measured quantitatively by UV-vis spectroscopy. Fina1ly, an attempt has been made to correlate the acidity determined by
the two independcnt methods and the catalytic activity of present systems in the benzoylation of toluene with benzoyl
chloride. Incorporation of Fe and Cr has changed the properties of AI pitlared montmorillonite. Fe pillared systems have
been found to be vcry good catalysts for benzoylation reaction
Sugunan, S; Kumaree Seena, C R(Indian Journal of Chemistry, May , 1998)
[+]
[-]
Abstract:
We have investigated the changes in surface acidity/basicity
and catalytic pro~erties of samarium oxide due to surface modification
by SO42- ion. The acidity/basicity of the catalysts is
determined by titration method using Hammett indicators.
Esterification of acetic acid by n-butanol is chosen as a test
reaction. Sm203, owing to its high basicity and low acidity, does
not catalyze the reaction. But sulphated Sm20J catalyzes the
esterification reaction effectively. Activation temperature does
not have much effect on the acidity of sulphated samaria.
Sugunan, S; Anto, Paul(Indian Journal of Chemistry, April , 1997)
[+]
[-]
Abstract:
The surface acidity/basicity of binary oxides of Zr and La and the ternary oxides of Zr, La and Al are
reported. The data have been correlated with their catalytic activity towards liquid phase reduction of
cyclohexanone.
Sugunan, S; Bindhu, Jacob(Indian Journal of Engineering & Materials Sciences, June , 1997)
[+]
[-]
Abstract:
The surface acidity and basicity of ternary oxides of
AI, Ce and Dy have been determined using a set of
Hammett indicators. The data have been correlated
with the catalytic activity of these oxides towards the
liquid phase reduction of cyclohexanone in 2-propanol.
The reaction is favoured by the higher basicity of
the ternary oxide.
Sugunan, S; Ampili, S; Bindhu, Jacob; Rani, Varghese(Indian Journal of Chemistry, February , 1996)
[+]
[-]
Abstract:
The surface acidity and basicity of ternary oxides of
La, Ce and AI have been determined using a set of
Hammett indicators. The data have been correlated
with the catalytic activity of these oxides towards the
liquid phase reduction of cycIohexanone in 2-propanol.
Sugunan, S; Sunitha, Kurur; Anto, Paul(Indian Journal of Chemistry, December , 1994)
[+]
[-]
Abstract:
The surface acidity and basicity of oxides of Sm and Zr
and their mixed oxides have been determined using a set of
Hammett indicators. The data have been correlated with
the catalytic activity of these oxides towards the liquid
phase reduction of cyclo-hexanone in 2-propanol.
Sugunan, S; Devika Rani, G; Unnikrishnan, P A(Indian Journal of Engineering & Materials Sciences, October , 1995)
[+]
[-]
Abstract:
Acid/base strength distribution of Y2O3 and its mixed
oxides with alumina catalysts are measured on Hammett
acidity function scale and expressed in terms of H0max
value. Basicity of Y2O3 increases with increase in activation
temperature and for mixed oxides the basicity increases
with increase in concentration of Y2O3, in the catalyst.