The effect of residual cations in rare earth metal modified faujasite–Y zeolite has been monitored using magic angle spinning NMR spectral analysis and catalytic activity studies. The second metal ions being used are Na+, K+ and Mg+. From a comparison of the spectra of different samples, it is concluded that potassium and magnesium exchange causes a greater downfield shift in the 29Si NMR peaks. Also, lanthanum exchanged samples show migration behavior from large cages to small cages, which causes the redistribution of second counter cations. It is also observed that Mg2+ causes the most effective migration of lanthanum ions due to its greater charge. The prepared systems were effectively employed for the alkylation of benzene with 1-octene in the vapor phase. From the deactivation studies it is observed that the as-exchanged zeolites possess better stability towards reaction condition over the pure HFAU zeolite.
Suja, H; Deepa, C S; Sreeja Rani, K; Sugunan, S(Indian Journal of Chemistry, August , 2003)
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Abstract:
The present work attempts a systematic examination of the effect of sulphate content on the physico-chemical properties
and catalytic activity of sulphated zirconia and iron promoted sulphated zirconia systems. Sulphate content is estimated by
EDX analysis. The amount of sulphate incorporated has been found to influence the surface area, crystal structure and the
acid strength distribution. Ammonia TPD and adsorption studies using perylene have enabled the determination of surface
acidic properties. The results are supported by the thermodesorption studies using pyridine and 2,6-dimethylpyridine. The
catalytic activity towards benzoylation reaction has been correlated with the surface acidity of the systems.
Cyclohexanol decomposition activity of supported vanadia catalysts is ascribed to the high surface area, total acidity and interaction between supported vanadia and the amorphous support. Among the supported catalysts, the effect of vanadia over various wt% V2O5 (2–10) loading indicates that the catalyst comprising of 6 wt% V2O5 exhibits higher acidity and decomposition activity. Structural characterization of the catalysts has been done by techniques like energy dispersive X-ray analysis, X-ray diffraction and BET surface area. Acidity of the catalysts has been measured by temperature programmed desorption using ammonia as a probe molecule and the results have been correlated with the activity of catalysts.
Invertase was immobilised on microporous montmorillonite K-10 via adsorption and covalent binding. The immobilised enzymes were tested for sucrose hydrolysis activity in a batch reactor. Km for immobilised systems was greater than free enzyme. The immobilised forms could be reused for 15 continuous cycles without any loss in activity. After 25 cycles, 85% initial activity was retained. A study on leaching of enzymes showed that 100% enzyme was retained even after 15 cycles of reuse. Leaching increased with reaction temperature. Covalent binding resisted leaching even at temperatures of 70 °C.
The present work investigates on the applicability of metal promoted sulphated zirconia
catalysts for the hydroxylation of phenol under mild conditions. The percentage conversion
and product distribution was highly sensitive towards the reaction parameters like the catalyst
composition, reaction temperature, H202/ phenol ratio and the solvent used.
Sugunan, S; Bindhu, J; Disha; Jessey, V(Indian Journal of Chemistry, July , 1997)
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Abstract:
The Lewis acidity of yttrium and dysprosium exchanged
zeolite Y and ZSM-5 has been determined by titration method
using Hammett indicators. The acidity of the Y form increases
with increase in concentration of the rare earth cation in the Y
zeolite. It is independent of the amount of the rare earth ion for
ZSM-5. The data have been correlated with the activity of these
zeolites for the esterification of butanol using acetic acid.
The present work undertakes the preparation and physico-chemical characterisation of iron promoted sulphated zirconia
(SZ) with different amounts of iron loading and their application to Friedel-Crafts benzoylation of benzene, toluene and xylene
under different experimental conditions, XRD and laser Raman techniques reveal the stabilisation of the tetragonal phase of
zirconia and the existence of iron in highly dispersed form as Fe203 on the catalyst surface. The surface acidic properties were
determined by ammonia temperature programmed desorption (TPD) and perylene adsorption, The results were supported by
the TGA studies after adsorption of pyridine and 2,6-dimethylpyridine (2,6-DMP), Strong Lewis acid sites on the surface, which
are evident from TPD and perylene adsorption studies. explain the high catalytic activity of the systems towards benzoylation.
The experimental results provide evidence for the truly heterogeneous nature of the reaction. The studies also establish the
resistance to deactivation in the metal incorporated sulphated systems.
Manju, Kurian; Sugunan, S(Indian Journal of Chemistry, October , 2003)
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Abstract:
Iron, aluminium and mixed iron aluminium pillared clays have been prepared by partial hydrolysis method and doped
with IO% Mo, V and Cr. The samples have been characterised by XRD, FTIR and surface area and pore Volume
measurements. The surface acid site distribution has been determined by temperature programmed desorption of ammonia.
Vanadia incorporated systems show maximum acidity. Benzylation of o-xylene has been done as probe reaction to test
catalytic activity. Benzyl chloride is a superior benzylating agent compared to benzyl alcohol in activity and selectivity.
Cent percent selectivity towards monobenzylated product is obtained in all the cases. Fe pillared systems exhibit maximum
activity. The catalytic activities of the systems can be correlated with the amount of strong add sites. The effects of various
reaction variables on the reaction have been studied. Presence of moisture has a diminishing effect on the reaction rate.
Sugunan, S; Nishamol, K(Indian Journal of Chemistry, May , 2002)
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Abstract:
The liquid-phase Friedel-Crafts acylation of toluene using benzoyl chloride as benzoylating agent has heen carried out over Nix, Mn(l-x)Fe2 O4 (x=O, 0.2, 0.4, 0.6, 0.8 and 1.0) type systems under different reaction conditions. It is observed that the systems with high 'x' values are effective for the conversion of BOC and the selective formation of 4-MBP. Selectivity for 4-MBP over MnFe2O4 is more than 90% under the optimized reaction conditions. Sites of moderate acidity is effective in calalyzing the benzoylation reaction.
Anantaraman, R; Sugunan, S(Indian Journal of Chemistry, August , 1982)
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Abstract:
Kinetics of mercuric chloride catalysed solvolysis of benzyl chloride have been studied in water. 10% aq. ethanol, 10,20 and
30% aq. acetone and 20% aq. DMSO. The results confirm the operation of a mass law effect.
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, June , 2002)
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Abstract:
A series of supported vanadia systems have been prepared by
excess solvent technique using La203 and DY203 as supports.
Physical characterization has been carried out using XRD, FTIR,
TG studies, BET surface area measurement, pore volume analysis
etc. Cyclohexanol decomposition has been used as a test reaction
for evaluating the acid base properties of the supported system.
The oxidative dehydrogenation of ethylbenzene has been
employed as a chemical probe reaction to examine the catalytic
activity. The active species correspond to amorphous and
crystalline tetrahedral vanadyl units in the supported system.
Sankara Raman, S; Nampoori, V P N; Vallabhan, C P G; Ambadas, G; Sugunan, S(American Institute of Physics, 1995)
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Abstract:
The thermal diffusivity of y-alumina is determined by the photoacoustic method. The method is
calibrated by determining the thermal diffusivity of copper and aluminum. The effect of the
chemisorbed hydroxyl groups or thermal diffusivity is studied by degassing the sample at different
temperatures.
The heterogeneous photocatalytic degradation of methylorange over TiO2 is studied
and is found to be cost effective. Effect of Zirconium metal incorporation over titania system is investigated. Photocatalytic degradation of methylorange using solar radiation is
found to be highly economical when compared with the processes using artificial UV
radiation, which require substantial electrical power input. The characterization of titania as
well as modified zirconium metal doped titania systems are done using XRD, FTIR and
EDAX measurements. The catalytic activities of different systems are also compared and is
tried to correlate with the crystallite size and presence of dopant metal.
Shali, N B; Sugunan, S(Springer Netherlands, 2007)
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Abstract:
Lanthana modified sol-gel titania is prepared
through particulate sol-gel route and the physico-chemical
characterizations of the prepared systems were done using
X-Ray diffration, EDX, BET surface area-pore volume measurements
and TG-DTG analysis. Benzophenone was observed
to be the sole product in the TiO2 photocatalyzed
oxidation of benzhydrol in oxygen purged acetonitrile. The
influence of various parameters, like irradiation time, amount
of catalyst, concentration of the catalyst and other factors on
the photocatalytic oxidation has been investigated. The proposed
mechanism envisages the involvement of a superoxide
radical anion.
Sugunan, S; Binitha, N N(Journal of Applied Polymer Science,Wiley InterScience, March 16, 2007)
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Abstract:
In situ polymerization of aniline is done
inside the pillared clay matrix. The nonswellable pillared
clay confined matrix allows efficient polymerization that
leads to nanofibrous morphology. As a result high polymer
order and crystallinity is attained and is evident from
XRD patterns. The strong interaction between the clay
layers and polyaniline (PANI) is understood from FTIR and DRS spectra. Additionally these analytical results suggest that the prepared PANI is in the doped state. The
PANI/pillared clay nanocomposite formation gives additional
thermal stability to the polymer backbone and is clear from the DTG curves.
Transition metal-loaded (3%) nanocrystalline sulfated titania (ST) powders are prepared using the sol–gel technique. Anatase is found as the active phase in all the samples. Sulfate ion impregnation decreases the crystallite size and stabilizes the anatase phase of TiO2. Acidity of the samples is found to increase by the incorporation of sulfate ion and also by the modification by transition metal ions. All the prepared catalysts are found stable up to 700 °C.
Sugunan, S; Bindhu, Jacob; Binoy,Jose(Indian Journal of Chemistry, October , 1999)
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Abstract:
The results of a detailed study of the propionylation of anisole over various medium and large pore zeolites such as H-ZSM-5, H-beta, H-Na-beta. H-mordenite. H-Y and H-RE- Y are presented and discussed. In addition, homogenous catalysts and amorphous Si02-Al2O3 are also included for comparison, The catalyst and process parameters are optimised to enhance the conversion of propionyl chloride(PC) and selectivity to 4-methoxypropiophenone(4-MOPP).
Sugunan, S; Benny, Thomas(Indian Journal of Chemistry, February , 1995)
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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)
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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.