Dimethylacetals of ketones; cyclohexanone, acetophenone,
and benzophenone have been prepared by reacting
ketones with methanol under mild reaction conditions.
Large pore zeolites (H-Y and its rare earth metal, Ce3+, La3+,
and RE3+ modified forms), and mesoporous clay (K-10
montmorillonite and its cerium exchanged counterpart) with
regular pore structure, silica and silica-alumina have been
used as catalysts. Clay catalysts are found to be much more
active than zeolites, thanks to slightly bigger pore size. The
nature of the pores of the solid acid catalysts determine acetalization
efficiency of a particular catalyst. As evidenced
by the reaction time studies, the catalyst decay is greater
over the zeolites than over the clays. Carrying out the reaction
with ketones of different molecular sizes it is shown
that K-10 clays and rare earth exchanged H-Y zeolites are
promising environmentally friendly catalysts for their use in
the production fine chemicals.
Three enzymes, α-amylase, glucoamylase and invertase, were immobilized on acid activated montmorillonite K 10 via two independent techniques, adsorption and covalent binding. The immobilized enzymes were characterized by XRD, N2 adsorption measurements and 27Al MAS-NMR spectroscopy. The XRD patterns showed that all enzymes were intercalated into the clay inter-layer space. The entire protein backbone was situated at the periphery of the clay matrix. Intercalation occurred through the side chains of the amino acid residues. A decrease in surface area and pore volume upon immobilization supported this observation. The extent of intercalation was greater for the covalently bound systems. NMR data showed that tetrahedral Al species were involved during enzyme adsorption whereas octahedral Al was involved during covalent binding. The immobilized enzymes demonstrated enhanced storage stability. While the free enzymes lost all activity within a period of 10 days, the immobilized forms retained appreciable activity even after 30 days of storage. Reusability also improved upon immobilization. Here again, covalently bound enzymes exhibited better characteristics than their adsorbed counterparts. The immobilized enzymes could be successfully used continuously in the packed bed reactor for about 96 hours without much loss in activity. Immobilized glucoamylase demonstrated the best results.
Sugunan, S; Anto, Paul(Indian Journal of Chemistry, December , 1997)
[+]
[-]
Abstract:
The surface acidity and basicity of mixed oxides of Zr and Y
and their mixed oxides have been determined by titration method
using Hammett indicators. The acid base properties are evaluated
on a common scale of acid strength. Liquid phase reduction of
cyclohexanone has been selected as a model reaction to correlate
catalytic activity.
Sugunan, S; Rani, G D; Unnikrishnan, P A(J. Mater. Sci. Technol., 1994)
[+]
[-]
Abstract:
The electron donor properties of Pr6O11 activated at 300. 500 and 800°C are reported from the studies
on adsorption of electron acceptors of various electron affinity (7. 7, 8, 8-tetracyanoquinodimethane.
2, 3. 5, 6-tetrachloro-l, 4-benzoquin one. p-dinitrobenzene. and
m-dinitrobenzene) in three solvents (acetonitrile, 1,4-dioxan and ethyl acetate). The extent of electron
transfer during adsorption is understood from magnetic measurements and ESR spectral data. The corresponding
data on mixed oxides of Pr and Al are reported for various compositions, The acid / base
properties of these oxides are determined using a set of Hammett indicators.
Sugunan, S; Chemparathy, G V; Anto, Paul(Indian Journal of Engineering & Materials Sciences, 1996)
[+]
[-]
Abstract:
The surface acidity and basicity of binary oxides of Zr with Ce and La are determined using a series of Hammet indicators and Ho,,max values are reported. The generation of new acid sites habe been ascribed to the charge imbalance of M1-O-M2 bonds, where M1 and M2 are metal atoms. Both Bronsted and Lewis acid sites contribute to the acidity of the oxides
Sugunan, S; Devika Rani, G(Journal of Materials Science Letters, 1993)
[+]
[-]
Abstract:
The electron donor properties of Nd2O3 activated at 300, 500 and 800°C were investigated
through studies on the adsorption of electron acceptors of various electron affinities - 7, 7, 8,8-tetracyanoquinodimethane (2.84 eV). 2, 3, 5, 6-tetrachloro-l , 4-benzoquinone (2.40 eV).
p-dinitrobenzene (1.77 eV), and m-dinitrobenzene (1.26 eV) in solvents acetonitrile and
1, 4-dioxan. The extent of electron transfer during adsorption has been found from magnetic
measurements and electronic spectral data. The corresponding data on mixed oxides of
neodymium and aluminium are reported for various. compositions. The acid-base properties of
catalysts were also determined using a set of Hammett indicators.
Sugunan, S; Nisha, K; Rekha, R; Rahna, K S; Suja, H; Deepa, C S(Indian Journal of Chemistry, July , 2000)
[+]
[-]
Abstract:
The pillared montmorillonite has been prepared by exchanging
Na+ in the interlayer of montmorillonite with Al hydroxy cation followed
by calcination. Pillared clays are also prepared after exchanging
Na' ions with Ce, La, Sm-ions and then pillarcd with aluminium
oxides, The surface characterisation of the prepared catalysts has been
done using XRD and surface area measurements. To probe the acidic
property of the system, temperature programmed desorption (TPD)
of NH, has been done. Toluene alkylation by benzyl chloride has
been carried out for the evaluation of catalytic activity. The most
active system is found to be mixed Al/Zr pillarcd montrnorillonite.
Sugunan, S; Bindhu, Jacob(Indian Journal of Chemistry, October , 1999)
[+]
[-]
Abstract:
The acidity of the various rare-earth exchanged zeolite-Y
catalysts has been examined by titration method using Hammett
indicators and is correlated with the catalytic activity of the
samples in the benzylation of 0-xylene.
Surface acidity/Basicity of mixed oxides of La and Zn activated at three different temperatures were determined. The data have been correlated with the catalytic activity for liquid phase reduction of cyclohexanone in isopropanol.
Sugunan, S; Seena, C R K(Indian Journal of Chemistry, September , 1999)
[+]
[-]
Abstract:
The surface acidity/ basicity of TiO2 (rutile) and its sulphate modified
form have been determined by titration method using Hammett
indicators after activation at different temperatures. The electron
donating properties of these oxides are also studied from the adsorption
of electron acceptors of different electron affinity values. The
data have been correlated with the catalytic activity of these oxides
towards esterification of acetic acid using n-butanol, reduction of
cyclohexanone in isopropanol and oxidation of cyclohexanol in benzophenone.
Catalytic activity for esterification and oxidation reaction
parallels the acidity while that for reduction reaction parallels
the basicity of these oxides.
Sugunan, S; Seena, Kumaree C R(Indian Journal of Chemistry, November , 1999)
[+]
[-]
Abstract:
The changes in surface acidity/basicity and catalytic activity of cerium oxide due to surface modification by sulphate ion have been
investigated. Electron donor properties of both the modified and unmodified oxides have been studied using electron acceptors of
various electron affinity values, viz. 7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro--l, 4-benzoquinone. p-dinitrobenzene and
m-dinitrobenzene in order to find out whether the increase in acidity on suphation is due to the generation of new acidic sites or they are
formed at the expense of some of the basic sites. The surface acidity/basicity has been determined using a set of Hammett indicators.
The data have been correlated with the catalytic activity of the oxides for esterification of acetic acid using l-butanol, reduction of
cyclohexanone with 2- propanol and oxidation of cyclohexanol using benzophenone.
Sugunan, S; Kumaree Seena, C R(Indian Journal of Chemistry, August , 1998)
[+]
[-]
Abstract:
The surface electron donor properties of sulphate modified stannic oxide have been determined from the
adsorption of electron acceptors of various electron affinities on the oxide surface. The acid base properties of
stannic oxide have been determined by titration method using Hammett indicators. Catalytic activities of the
oxide for esterification of acetic acid using n-butanol.reduction of cyclohexanone in 2-propanol and oxidation of
cyclohexanol with benzophenone have been studied. The data have been correlated with the surface electron
donor properties of these oxides. The activity for reduction and oxidation decreases and that for esterification
reaction increases on modification with sulphate ion. It has heen found that electron donating capacity decreased
when stannic oxide was modified with sulphate ion.
Description:
Note:Indian Journal of Chemistry
Vol. 37A, August 1998, pp. 669 - 673
Sugunan, Sankaran; Binitha, N N(React Kinet.Catal.Lett.& Akademiai Kiado, March 27, 2008)
[+]
[-]
Abstract:
Linear alkylbenzene sulfonic acid, the largest-volume synthetic surfactant, in addition to its excellent performance , is important due to its biodegradable environmental friendliness, as it has a straight chain and is prepared by the sulphonation of linear alkylbenzenes (LAB). To ensure environmental protection, the commercial benzene alkylation catalysts HF or AICI3 are replaced and we have developed a clean LAB production process using a pillared clay catalyst capable of not only replacing the conventional homogeneous catalyst, but also having high selectivity for the best biodegradable 2-phenyl LAB isomer .Pillared clay catalysts having high Bronsted acidity show efficient conversion in gas phase alkylation of benzene with 1-octene with a good 2-phenyl octane selectivity.
Jyothi, T M; Rao, B S; Sugunan, S; Sreekumar, K(Indian Journal of Chemistry, December , 1999)
[+]
[-]
Abstract:
Alkylation of phenol with methanol has been carried out over
Sn-La and Sn-Sm mixed oxides of varying compositions at 623 K
in a vapour phase flow reactor. It is found that the product
selectivity is greatly influenced by the acid-base properties of the
catalysts. Ortho-cresol formation is favoured over catalysts with
weak acid sites whereas formation of 2,6-xylenol occurs in the
presence of stronger acid sites. The cyclohexanol decomposition
reaction and titrimetric method using Hammett indicators have
been employed to elucidate the acid-base properties of the
catalysts.
Description:
Indian Journal of Chemistry
Vol. 38A, December 1999, pp. 1253-1255
Sugunan, S; Sherly, K B(Indian Journal of Chemistry, August , 1993)
[+]
[-]
Abstract:
The electron donating properties of La2O3 activated at 300, 500 and 800·C and its mixed oxides with
alumina are reported from the studies on adsorption of electron acceptors of varying electron affinity on
La203. The electron acceptors with their electron affinity values given in parenthesis are:
7,7,8,8-tetracyanoquinodimethane (2.84 eV), 2,3,5,6-tetrachloro-I,4-benzoquinone (2.40 eV) and
p-dinitrobenzene(l.77eV). The basicity of the oxide has been determined by titration with n-butylamine and
Ho.max values are reported. The limit of electron transfer from the oxide to the electron acceptor is between
2.40 and 1.77 eV. It is observed that La203 promotes the surface electron properties of alumina without
changing its limit of electron transfer.
Bejoy, Thomas; Prathapan,S; Sugunan, S(Elsevier, September , 2005)
[+]
[-]
Abstract:
In this paper, a novel application of solid acid catalysts in the Beckmann rearrangement of E,E-cinnamaldoxime in the synthesis of an important heterocyclic compound; isoquinoline is reported. E,E-Cinnamaldoxime under ambient reaction conditions on zeolite catalysts underwent Beckmann rearrangement to produce isoquinoline in yields of ca. 86–95%. Cinnamonitrile and cinnamaldehyde were formed as by-products. LaH-Y zeolite produces maximum amount of the desired product (yield 95.6%). However, the catalysts are susceptible for deactivation due to the basic nature of the reactants and products, which neutralize the active sites. H-Y zeolite is more susceptible (22% deactivation in 10 h) for deactivation compared to the cerium-exchanged counterpart (18% deactivation in 10 h). Thus, the optimal protocol allows isoquinoline to be synthesised in excellent yields through the Beckmann rearrangement of cinnamaldoxime. The reaction is simple, effective, does not involve any other additives, and environmentally benign.
Sugunan, S; Suja, H; Deepa, C S; Sreeja Rani, K; Ouseph, M V(Indian Journal of Chemistry, November , 2002)
[+]
[-]
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.
Sugunan, S; Renuka, N K(Indian Journal of Chemistry, February , 2001)
[+]
[-]
Abstract:
Vapour phase methylation of phenol is carried out over La2O3 supported vanadia systems of various composition. The structural features and physico chemical characterisation of the catalysts are investigated. Orthovanadates are formed in addition to surface vanadyl species on the metal oxide support. No V2O5 crystallites are detected. The acid base properties of the oxides are studied by Hammett indicator method and decomposition of cyclohexanol.The data are correlated with the catalytic activity and selectivity of the products. Ring alkylation is found to be predominant over these catalysts.
Sugunan, S; Sherly, K B(Indian Journal of Chemistry, October , 1994)
[+]
[-]
Abstract:
Lanthanum oxide, La2O3 has been found to be an effective
catalyst for the liquid phase reduction of cyclohexanone.
The catalytic activities of La2O3 activated
at 300, 500 and 800·C and its mixed oxides with
alumina for the reduction of cyclohexanone with
2-propanol have been determined and the data parallel
that of the electron donating properties of the catalysts.
The electron donating properties of the catalysts have
been determined from the adsorption of electron acceptors
of different electron affinities on the surface of
these oxides.
The catalytic activity of some of the ABO3 (A = La, Pr
and Sm, B= Cr, Mn, Fe, Co and Ni) perovskite-type oxides
for the liquid phase reduction of ketone and oxidation of
alcohol in 2-propanol medium has been studied. The data
have been correlated with the surface electron donor
properties of these oxides. The surface electron donor
properties have been determined from the adsorption of
electron acceptors of varying electron affinities on the
oxide surface.