Glucoamylase was immobilized on acid
activated montmorillonite clay via two different procedures
namely adsorption and covalent binding. The
immobilized enzymes were characterized by XRD,
NMR and N2 adsorption measurements and the
activity of immobilized glucoamylase for starch
hydrolysis was determined in a batch reactor. XRD
shows intercalation of enzyme into the clay matrix
during both immobilization procedures. Intercalation
occurs via the side chains of the amino acid residues,
the entire polypeptide backbone being situated at the
periphery of the clay matrix. 27Al NMR studies
revealed the different nature of interaction of enzyme
with the support for both immobilization techniques.
N2 adsorption measurements indicated a sharp drop in
surface area and pore volume for the covalently bound
glucoamylase that suggested severe pore blockage.
Activity studies were performed in a batch reactor. The
adsorbed and covalently bound glucoamylase retained
49% and 66% activity of the free enzyme respectively.
They showed enhanced pH and thermal stabilities. The
immobilized enzymes also followed Michaelis–Menten
kinetics. Km was greater than the free enzyme that was
attributed to an effect of immobilization. The immobilized
preparations demonstrated increased reusability
as well as storage stability.
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.
Rare earth exchanged Na–Y zeolites,
H-mordenite, K-10 montmorillonite clay and amorphous
silica-alumina were effectively employed for the
continuous synthesis of nitriles. Dehydration of benzaldoxime
and 4-methoxybenzaldoxime were carried
out on these catalysts at 473 K. Benzonitrile (dehydration
product) was obtained in near quantitative yield
with benzaldoxime whereas; 4-methoxybenzaldoxime
produces both Beckmann rearrangement (4-methoxyphenylformamide)
as well as dehydration products
(4-methoxy benzonitrile) in quantitative yields. 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
(TOS) studies show decline in the activity of the catalysts
due to neutralization of acid sites by the basic reactant
and product molecules and water formed during the
dehydration of aldoximes.
Vanadia/ceria catalysts (2–10 wt% of V2O5) were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution. Structural characterization was done with energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), BET surface area measurements, FT-IR spectroscopy and nuclear magnetic spectral analysis (51V MASNMR). XRD and 51V MASNMR results show highly dispersed vanadia species at lower loadings and the formation of CeVO4 phase at higher V2O5 loading. The catalytic activity of catalysts was conducted in liquid phase oxidation of ethylbenzene with H2O2 as oxidant. The oxidation activity is increased with loading up to 8 wt% V2O5 and then decreased with further increase in V2O5 content to 10 wt%. Different vanadia species evidenced by various techniques were found to be selective towards ethylbenzene oxidation. The CeVO4 formation associated with increased concentration of vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone.
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.
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.
Spinel systems with the composition of Cu 1−x Zn x Cr 2 O 4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h.
Sugunan, Sankaran; Binitha, N N(React Kinet.Catal.Lett.& Akademiai Kiado, March 27, 2008)
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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.
Sugunan, S; Nampoori, V P N; Radhakrishnan, P; Sanjay, G; Suja, H; Lyjo, Joseph K(Elsevier, June 28, 2008)
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Abstract:
Thermal diffusivity (TD) measurement on commercial K-10 and KSF montmorillonites was carried out by
photoacoustic technique. The TD of the montmorillonites after methylene blue adsorption changed with the
dye concentration. The repeatedly adsorbed samples showed a lesser TD than the single adsorbed samples.
After methylene blue adsorption the acid leached K-10 samples showed well defined changes in TD when
compared to the ordered KSF samples
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.
Sugunan, S; Suja, H; Sanjay, G; Joseph, L K; Nampoori, V P N; Radhakrishnan, P(Taylor & Francis, April 1, 2009)
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Abstract:
Thermal diffusivity (TD) measurements were performed on some industrially
important dyes – auramine O (AO), malachite green and methylene blue (MB) –
adsorbed K-10 montmorillonites using photoacoustic method. The TD value for
the dye-adsorbed clay mineral was observed to change with a variation in dye
concentration. The contribution of the dye towards TD was also determined. The
repeatedly adsorbed samples with MB and AO exhibited a lower TD than the
single-adsorbed samples. TD values of sintered MB samples were also obtained
experimentally. These sintered samples exhibit a higher TD, although they show
a trend similar to that of non-sintered pellets. A variation in dye concentration
and sintering temperature can be used for tuning the TD value of the clay mineral
to the desired level
Description:
Philosophical Magazine
Vol. 89, No. 10, 1 April 2009, 895–905
The present work describes the immobilization of α-amylase over well ordered mesoporous molecular sieve SBA-15 with different pore diameters synthesized by post synthesis treatment (PST) hydrothermally after reaction at 40°C. The materials were characterized by N 2 adsorption–desorption studies, small angle X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. Since α-amylase obtained from Bacillus subtilis has dimensions of 35 × 40 × 70 Å it is expected that the protein have access to the pore of SBA-15 (PST-120°C) with diameter 74 Å. The pore dimension is appropriate to prevent considerable leaching. The rate of adsorption of the enzyme on silica of various pore sizes revealed the influence of morphology, pore diameter, pore volume and pH.
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.