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.
The influence of the chemical composition and silylation of mesoporous MCM-41 materials on the photochromic
behaviour of adsorbed spiropyran (BIPS) and 6-nitrospiropyran was studied. Upon incorporation, the spiropyrans
underwent ring opening to form either zwitterionic merocyanine or its corresponding O-protonated form. In all
silica MCM-41 or in the MCM-41 containing aluminium, the O-protonated merocyanine was predominantly
formed. In the case of MCM-41 modified by silylation of the OH groups, a mixture of zwitterionic merocyanine
and spiropyran was present. The photochromic response was studied by means of steady-state irradiation and by
laser flash photolysis. Steady-state irradiation (λ > 450 nm) of the solid samples gives rise in all cases to an intensity
decrease of the absorption bands corresponding to either the protonated or the unprotonated merocyanine form
(reverse photochromism). In contrast, laser flash photolysis at 308 nm of spiropyrans supported on silylated
MCM-41 allows observation of the photochemical ring opening of residual spiropyran to the corresponding
zwitterionic form (normal photochromism).
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, February , 2002)
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Abstract:
Sm2O3 - vanadia catalysts have been prepared by wet
impregnation method using NH4VO3 solution. The surface
properties of the prepared catalysts have been studied using FTIR.
XRD. surface area and pore volume data. The acid-base properties
of the system have been investigated by titrimetric method using
Hammett indicators. adsorption of electron acceptors as well as
decomposition of cyclohexanol. Phenol alkylation reaction by
methanol has been carried out to investigate the catalytic activity.
It has been observed that the selectivity of the products depends
upon the composition of the supported system
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, April , 2002)
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Abstract:
Physico-chemical characterization of DY203/V2O5 systems prepared through wet impregnation method has been carried
out using various techniques like EDX, XRD, FTIR. thermal studies, BET surface area, pore volume and pore size
distribution analysis. The amount of vanadia incorporated has been found to influence the surface properties of dysprosia.
The spectroscopic results combining with X-ray analysis reveal that vanadia species exist predominantly as isolated
amorphous vanadyl units along with crystalline dysprosium orthovanadate. Basicity studies have been conducted by
adsorption of electron acceptors and acidity and acid strength distribution by temperature programmed desorption of
ammonia. Cyclohexanol decomposition has been employed as a chemical probe reaction to examine the effect of vanadia on
the acid base property of Dy2O3. Incorporation of vanadia titrates thc Lewis acid and base sites of Dy2O3, while an
enhancement of Bronsted acid sites has been noticed. Data have been correlated with the catalytic activity of these oxides
towards the vapour phase methylation of phenol
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.
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.
Sugunan, S; Rahna, K S(Indian Journal of Chemistry, July , 2002)
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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
Ramankutty, C G; Sugunan, S; Bejoy, Thomas(Elsevier, September 9, 2002)
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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.
Iron pillared Montmorillonite has been synthesised and it is then wet impregnated with vanadia with different vanadia
composition. These catalysts are characterised using conventional techniques such as XRD analysis,FTIR analysis and
surface area and pore volume measurements. Acidity is measured using spectrophotometric monitoring of adsorption of
perylene, thermogravimetric desorption of 2.6 dimethylpyridine and temperature programmed desorption of ammonia.
Activity studies are done in the liquid phase. It has been concluded that Lewis acidic sites are responsible for the benzylation
of toluene when the benzylating agent is benzyl chloride while Bronsted acidic sites are responsible when the reagent is
benzyl alcohol.
Sugunan, S; Suja, H; Deepa, C S; Sreeja Rani, K; Ouseph, M V(Indian Journal of Chemistry, November , 2002)
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Abstract:
Surface acidity of phosphate modified La2O3,CeO2 and SnO2 has been estimated by titrimetric Method using Hammett Indicators.Mixed Oxides of tin and lanthanum have also been prepared and subjected to phosphate modification.Surface characterizartion of the samples has been carried out using XRD, surface area,thermal analysis and IR spectroscopy.
Phosphate content in the samples has been chemically estimated. The catalytic activity for benzylation and esterification reaction has also been investigated.
Mohammed Yusuff, K K; Rani, Abraham(Elsevier,Journal of Molecular Catalysis A: Chemical 198 (2003) 175–183, December 2, 2002)
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Abstract:
Copper(II) complexes of two biologically important ligands, viz., embelin (2,5-dihydroxy-3-undecyl-2,5-cyclohexadien
1,4-dione) and 2-aminobenzimidazole were entrapped in the cages of zeolite Y by the flexible ligand method. The capability
of these compounds in catalyzing the reduction of oxygen (industrially known as deoxo reaction) was explored and the
results indicate an enhancement of the catalytic properties from that of the simple copper ion exchanged zeolite. These
point to the ability of the ligands in enhancing the oxygen binding capability of the metal ion. Elemental analyses, Fourier
transform infrared (FTIR), diffuse reflectance and EPR spectral studies, magnetic susceptibility measurements, TG, surface
area analyses and powder X-ray diffraction studies were used in understanding the presence, composition and structure of
the complexes inside the cages. The study also reveals the increased thermal and mechanical stability of the complexes as a
result of encapsulation.
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.
Smitha, V K; Suja, H; Joyce, Jacob; Sugunan, S(Indian Journal of Chemistry, February , 2003)
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Abstract:
Preparation and physico-chemical characterization or
phosphate modified zirconia systems and their application to
Friedel-Crafts benzylation and benzoylation of toluene have been
reported. The influence of transition metals on the surface
properties and catalytic activity has also been discussed.
Sreekumar, K(Indian academy of science, February 24, 2003)
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Abstract:
Significant results of our experimental investigations on the dependence of pH on real time
transmission characteristics on recording media fabricated by doping PVC with complexed methylene blue
are presented. The optimum pH value for faster bleaching was found to be 4×5. In typical applications, the
illumination from one side, normal to the surface of this material, initiates a chemical sequence that records
the incident light pattern in the polymer. Thus direct imaging can be successfully done on this sample. The
recorded letters were very legible with good contrast and no scattering centres. Diffraction efficiency
measurements were also carried out on this material.
Mohammed Yusuff, K K; Mayadevi, S; Preetha, G Prasad(Taylor & Francis, May 5, 2003)
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Abstract:
Two series of transition metal complexes of Schiff bases derived from
quinoxaline-2-carboxaldehyde with semicarbazide (QSC) and furfurylamine
(QFA) were synthesised and characterised by elemental analyses,
molar conductance and magnetic susceptibility measurements, IR, electronic
and EPR spectral studies. The QSC complexes have the general
formula [M(QSC)Cl2]. A tetrahedral structure has been assigned for the
Mn(II), Co(II) and Ni(II) complexes and a square-planar structure for the
Cu(II) complex. The QFA complexes have the formula [M(QFA)2Cl2].
An octahedral structure has been assigned for these complexes. All of
the complexes exhibit catalytic activity towards the oxidation of 3,5-di-tert-butylcatechol (DTBC) to 3,5-di-tert-butylquinone (DTBQ) using
atmospheric oxygen. The cobalt(II) complex of the ligand QFA was
found to be the most active catalyst.
Thomas Lee, S; Suresh, Kumar P; Unnikrishnan, K P; Nampoori, V P N; Girijavallabhan, C P; Sugunan, S; Radhakrishnan, P(Department of Applied Chemistry, May 15, 2003)
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Abstract:
In this communication, we discuss the details of fabricating an off-line fibre
optic sensor (FOS) based on evanescent wave absorption for detecting trace
amounts of Fe3+ in water. Two types of FOS are developed; one type uses
the unclad portion of a multimode silica fibre as the sensing region whereas
the other employs the microbent portion of a multimode plastic fibre as the
sensing region. Sensing is performed by measuring the absorption of the
evanescent wave in a reagent medium surrounding the sensing region. To
evaluate the relative merits of the two types of FOS in Fe3+ sensing, a
comparative study of the sensors is made, which reveals the superiority of
the latter in many respects, such as smaller sensing length, use of a double
detection scheme (for detecting both core and cladding modes) and higher
sensitivity of cladding mode detection at an intermediate range of
concentration along with the added advantage that plastic fibres are
inexpensive. A detection limit of 1 ppb is observed in both types of fibre and
the range of detection can be as large as 1 ppb–50 ppm. All the
measurements are carried out using a LabVIEW set-up.
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.
Mohammed Yusuff, K K; Suja, N R(Journal of Applied Polymer Science,Wiley InterScience, August 10, 2003)
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Abstract:
Two novel polystyrene-supported Schiff
bases, PSOPD and PSHQAD, were synthesized. A polymerbound
aldehyde was condensed with o-phenylenediamine
to prepare the Schiff base PSOPD, and a polymer-bound
amine was condensed with 3-hydroxyquinoxaline-2-carboxaldehyde
to prepare the Schiff base PSHQAD. This article
addresses the study of cobalt (II), nickel (II), and copper (II)
complexes of these polymer-bound Schiff bases. All the complexes
were characterized, and the probable geometry was suggested using elemental analysis, diffuse reflectance ultraviolet,
Fourier transform infrared spectroscopy, thermal
studies, surface area studies, and magnetic measurements.