Zeolite encapsulated complexes of ruthenium: synthesis, characterisation and catalytic activity studies

The work presented in this thesis is mainly centered on the synthesis and characterization of some encapsulated transition metal complexes and the catalytic activity of the synthesized complexes in certain organic reactions.thesis deals with the catalytic activity of ruthenium-exchanged zeolite and the zeolite encapsulated complexes of SSC, SOD, SPD, AA, ABA, DMG, PCO, PCP, CPO and CPP in the hydroxylation of phenol using hydrogen peroxide. The products were analyzed with a GC to determine the percentage conversion and the chromatograms indicate the presence of different products like hydroquinone, catechol,benzoquinone, benzophenone etc. The major product formed is hydroquinone. From the screening studies, RuYSSC was found to be the most effective catalyst for phenol hydroxylation with 94.4% conversion and 76% hydroquinone selectivity. The influence of different factors like reaction time, temperature, amount of catalyst, effect of various solvents and oxidant to substrate ratio in the catalytic activity were studied in order to find out the optimum conditions for the hydroxylation reaction. The influence of time on the percentage conversion of phenol was studied by conducting the reactions for different durations varying from one hour to four hours. There is an induction period for all the complexes and the length of the induction period depends on the nature of the active components. Though the conversion of phenol and selectivity for hydroquinone. increases with time, the amount of benzoquinone formed decreases with time. This is probably due to the decomposition of benzoquinone formed during the initial stages of the reaction into other degradation products like benzophenones. The effect of temperature was studied by carrying out the reaction at three different temperatures, 30°C, 50°C and 70°C. Reactions carried at temperatures higher than 70°C result either in the decomposition of the products or in the formation of tarry products. Activity increased with increase in the amount of the catalyst up to a certain level. However further increase in the weight of the catalyst did not have any noticeable effect on the percentage conversion. The catalytic studies indicate that the oxidation reaction increases with increase in the volume of hydrogen peroxide till a certain volume. But further increase in the volume of H202 is detrimental as some dark mass is obtained after four hours of reaction. The catalytic activity is largely dependent on the nature of the solvent and maximum percentage conversion occurred when the solvent used is water. The intactness of the complexes within the zeolite cages enhances their possibility of recycling and the activities of the recycled catalysts show only a slight decrease when compared to the fresh samples .

Studies on fungal flora with special reference to Yeasts in the Cochin backwaters

Man's concern with environmental deterioration is one of the major reasons for the increased interest in marine and estuarine microbes. Microbes form an important link in the biogeochemical cycling and their cyclinq activites often determine to a large measure the potential productivity of an ecosystem In the recycling of the nutrients in the estuary, bacteria and fungi therefore play a particularly significant role.The allochthonous plant materials contain biopolymers such as cellulose, lignin, humus etc., that are difficult to degrade into simpler substances. The fungi have the ability to degrade _substances, thereby making them available for cycling within the system. The present study is devoted to find the composition and the activity of myco populations of Cochin backwater. For convenience the thesis is divided into eight chapters. The opening chapter briefly reviews the literature and projects the importance of work and the main objectives. Second chapter discusses the materials and methods. In the third chapter the systematic and taxonomy of estuarine yeasts are examined in detail since this information is scarcely available for our waters. The general ecological aspects of the yeasts and filamentous fungi in the area of study are examined in the fourth chapter using appropriate statistical techniques. A special reference to the fungi in a small mangrove ecosystem is attempted in the fifth chapter. The biochemical studies are discussed in the sixth chapter and the penultimate chapter provides an overall discussion. In the last chapter the summary of the work is presented.

Studies on planktonic ostracods of the northern indian ocean

Planktonic ostracod of the Indian Ocean have not been studied in detail although extensive studies have been made on them from other oceans, particularly Atlantic. with this view, the present study was undertaken, to throw; some light on the systematics and distribution oi’ planktonic ostracods in this region, This study provides iniormation regarding the distribution or each species in the Northern Indian Ocean, specially in the Bay of Bengal which is the least explored, as far as planlctunio ostracods are concerned. It may also furnish us with the data regarding the nature of ostracod production in this area, which directly reflects on the total productivity as they play an important role in the rapid recycling or organic substances, iaecal pellets and even flocculants In the present study the main objectives are; (1) Proper detemination of the species or planktonic Ostraooda that occur in the area or investigation, (2) to explain the pattern oi’ distribution, (3) to estimate their abundance and to some extent seasonal variation, and (4) to correlate their distribution with the physics-chemical factors of the environment

“Studies on extracellular enzyme production during growth of Pleurotus sp. on lignocellulosic agriwaste and the utilization of spent mushroom substrate”

Commercially, Pleurotus spp. of mushroom are cultivated in bags. After mushroom cultivation, spent substrate remains as residual material. Proper recycling of spent substrate is beneficial for our economy. Spent substrate can be utilized for various other value added purposes through the proper knowledge of its components. Composition of various components depends on the activity of extracellular enzymes in the spent substrate. The present study was conducted to know the enzyme profile of some major extracellular enzymes - cellulase, hemicellulase (xylanase), pectinase and ligninase (lignin peroxidase and laccase) and to estimate cellulose, hemicellulose, pectin and lignin in the substrate. The use of spent substrate as a source of fibre and ethanol, and in the biodegradation of phenol by Pleurotus spp. was also investigated

“A comparative study of medium and large pore zeolites in alkylation reactions”

Zeolites have established themselves as industrial catalysts for over two decades for a variety of hydrocarbon processing reactions where acidity and shape selectivity are important factors. As solid catalysts, zeolites may be advantageous and superior compared to their homogenous counterparts due to their characteristic properties. It is only in recent years that the utility of zeolites for organic synthesis is recognized for producing specific organic intermediates and fine chemicals in high selectivity. In this thesis an attempt has been made to compare the catalytic activity of some medium and large pore zeolites in a few alkylation and acylation reactions. The work reported in the present study is basically centered around the following zeolites namely, ZSM-5, mordenite, zeolite Y and beta. The major reactions carried out were benzoylation of o-xylene, propionylation of toluene and anisole and benzylation of oxylene. . The programme involves the synthesis, modifications and characterization of the zeolite catalysts by various methods. The influence of various parameters such as non-framework cations, Si/Al ratio of zeolites, temperature of the reaction, catalyst concentration, molar ratio of the reactants and recycling of the catalysts were also examined upon the conversion of reactants and the formation of the desired products in the alkylation/ acylation reactions. The general conclusions drawn by us from the results obtained are summarized in the last chapter of the thesis. Zeolite beta ofi'ers interesting opportunities as a potential catalyst in alkylation reactions and the area of catalysis by medium and large pore zeolites is very fascinating and there is plenty of scope for further research in this field. Moreover, zeolite based catalysts are effective in meeting current industrial processing and more stringent environment pollution limits.

Regional climate model applications on sub-regional scales over the Indian monsoon region: The role of domain size on downscaling uncertainty

Regional climate models are becoming increasingly popular to provide high resolution climate change information for impacts assessments to inform adaptation options. Many countries and provinces requiring these assessments are as small as 200,000 km2 in size, significantly smaller than an ideal domain needed for successful applications of one-way nested regional climate models. Therefore assessments on sub-regional scales (e.g., river basins) are generally carried out using climate change simulations performed for relatively larger regions. Here we show that the seasonal mean hydrological cycle and the day-to-day precipitation variations of a sub-region within the model domain are sensitive to the domain size, even though the large scale circulation features over the region are largely insensitive. On seasonal timescales, the relatively smaller domains intensify the hydrological cycle by increasing the net transport of moisture into the study region and thereby enhancing the precipitation and local recycling of moisture. On daily timescales, the simulations run over smaller domains produce higher number of moderate precipitation days in the sub-region relative to the corresponding larger domain simulations. An assessment of daily variations of water vapor and the vertical velocity within the sub-region indicates that the smaller domains may favor more frequent moderate uplifting and subsequent precipitation in the region. The results remained largely insensitive to the horizontal resolution of the model, indicating the robustness of the domain size influence on the regional model solutions. These domain size dependent precipitation characteristics have the potential to add one more level of uncertainty to the downscaled projections.

High Styrene–Rubber Ionomers, an Alternative to Thermoplastic Elastomers

High styrene rubber ionomers were prepared by sulfonating styrene–butadiene rubber of high styrene content (high styrene rubber) in 1,2-dichloroethane using acetyl sulfate reagent, followed by neutralization of the precursor acids using methanolic zinc acetate. The ionomers were characterized using X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), dynamic mechanical analysis (DMA), and also by the evaluation of mechanical properties. The FTIR studies of the ionomer reveal that the sulfonate groups are attached to the benzene ring. The NMR spectra give credence to this observation. Results of DMA show an ionic transition (Ti) in addition to glass–rubber transition (Tg). Incorporation of ionic groups results in improved mechanical properties as well as retention of properties after three cycles of processing

Utilization of waste expanded polystyrene: Blends with silica-filled natural rubber

Expanded polystyrene (EPS) constitutes a considerable part of thermoplastic waste in the environment in terms of volume. In this study, this waste material has been utilized for blending with silica-reinforced natural rubber (NR). The NR/EPS (35/5) blends were prepared by melt mixing in a Brabender Plasticorder. Since NR and EPS are incompatible and immiscible a method has been devised to improve compatibility. For this, EPS and NR were initially grafted with maleic anhydride (MA) using dicumyl peroxide (DCP) to give a graft copolymer. Grafting was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy. This grafted blend was subsequently blended with more of NR during mill compounding. Morphological studies using Scanning Electron Microscopy (SEM) showed better dispersion of EPS in the compatibilized blend compared to the noncompatibilized blend. By this technique, the tensile strength, elongation at break, modulus, tear strength, compression set and hardness of the blend were found to be either at par with or better than that of virgin silica filled NR compound. It is also noted that the thermal properties of the blends are equivalent with that of virgin NR. The study establishes the potential of this method for utilising waste EPS

Brachyuran Crabs of Cochin Backwaters- Diversity, Habitat Ecology and Systematics, with special emphasis to Genus Scylla

Among the decapod crustaceans, brachyuran crabs or the true crabs occupy a very significant position due to their ecological and economic value. Crabs support a sustenance fishery in India, even though their present status is not comparable to that of shrimps and lobsters. They are of great demand in the domestic market as well as in the foreign markets. In addition to this, brachyuran crabs are of great ecological importance. They form the conspicuous members of the mangrove ecosystems and play a significant role in detritus formation, nutrient recycling and dynamics of the ecosystem. Considering all these factors, crabs are often considered to be the keystone species of the mangrove ecosystem. Though several works have been undertaken on brachyuran crabs world –wide as well as within the country, reports on the brachyuran crabs of Kerala waters are very scanty. Most of the studies done on brachyuran fauna were from the east coast of India and a very few works from the west coast. Among the edible crabs, mud crabs belonging to genus Scylla forms the most important due to their large size and taste. They are being exported on a large scale to the foreign markets like Singapore, Malaysia and Hong Kong. Kerala is the biggest supplier of live mud crabs and Chennai is the major centre of live mud crab export. However, there exists considerable confusion regarding the identification of mud crabs because of the subtle morphological differences between the species.In this context, an extensive study was undertaken on the brachyuran fauna of Cochin Backwaters, Kerala, India, to have a basic knowledge on their diversity, habitat preference and systematics. The study provides an attempt to resolve the confusion pertaining in the species identification of mud crabs belonging to Genus Scylla. Diversity study revealed the occurrence of 23 species of brachyuran crabs belonging to 16 genera and 8 families in the study area Cochin Backwaters. Among the families, the highest number of species was recorded from Family Portunidae .Among the 23 crab species enlisted from the Cochin backwaters, 5 species are of commercial importance and contribute a major share to the crustacean fishery of the Cochin region. It was observed that, the Cochin backwaters are invaded by certain marine migrant species during the Post monsoon and Pre monsoon periods and they are found to disappear with the onset of monsoon. The study reports the occurrence of the ‘herring bow crab’ Varuna litterata in the Cochin backwaters for the first time. Ecological studies showed that the substratum characteristics influence the occurrence, distribution and abundance of crabs in the sampling stations rather than water quality parameters. The variables which affected the crab distribution the most were Salinity, moisture content in the sediment, organic carbon and the sediment texture. Besides the water and sediment quality parameters, the most important factor influencing the distribution of crabs is the presence of mangroves. The study also revealed that most of the crabs encountered from the study area preferred a muddy substratum, with high organic carbon content and high moisture content. In the present study, an identification key is presented for the brachyuran crabs occurring along the study area the Cochin backwaters and the associated mangrove patches, taking into account the morphological characters coupled with the structure of third maxillipeds, first pleopods of males and the shape of male abdomen. Morphological examination indicated the existence of a morphotype which is comparable with the morphological features of S. tranquebarica, the morphometric study and the molecular analyses confirmed the non existence of S. tranquebarica in the Cochin backwaters.

New studies on the versatile roles of Polyaniline and its composites in polymer based optoelectronic and energy storage devices

From the early stages of the twentieth century, polyaniline (PANI), a well-known and extensively studied conducting polymer has captured the attention of scientific community owing to its interesting electrical and optical properties. Starting from its structural properties, to the currently pursued optical, electrical and electrochemical properties, extensive investigations on pure PANI and its composites are still much relevant to explore its potentialities to the maximum extent. The synthesis of highly crystalline PANI films with ordered structure and high electrical conductivity has not been pursued in depth yet. Recently, nanostructured PANI and the nanocomposites of PANI have attracted a great deal of research attention owing to the possibilities of applications in optical switching devices, optoelectronics and energy storage devices. The work presented in the thesis is centered around the realization of highly conducting and structurally ordered PANI and its composites for applications mainly in the areas of nonlinear optics and electrochemical energy storage. Out of the vast variety of application fields of PANI, these two areas are specifically selected for the present studies, because of the following observations. The non-linear optical properties and the energy storing properties of PANI depend quite sensitively on the extent of conjugation of the polymer structure, the type and concentration of the dopants added and the type and size of the nano particles selected for making the nanocomposites. The first phase of the work is devoted to the synthesis of highly ordered and conducting films of PANI doped with various dopants and the structural, morphological and electrical characterization followed by the synthesis of metal nanoparticles incorporated PANI samples and the detailed optical characterization in the linear and nonlinear regimes. The second phase of the work comprises the investigations on the prospects of PANI in realizing polymer based rechargeable lithium ion cells with the inherent structural flexibility of polymer systems and environmental safety and stability. Secondary battery systems have become an inevitable part of daily life. They can be found in most of the portable electronic gadgets and recently they have started powering automobiles, although the power generated is low. The efficient storage of electrical energy generated from solar cells is achieved by using suitable secondary battery systems. The development of rechargeable battery systems having excellent charge storage capacity, cyclability, environmental friendliness and flexibility has yet to be realized in practice. Rechargeable Li-ion cells employing cathode active materials like LiCoO2, LiMn2O4, LiFePO4 have got remarkable charge storage capacity with least charge leakage when not in use. However, material toxicity, chance of cell explosion and lack of effective cell recycling mechanism pose significant risk factors which are to be addressed seriously. These cells also lack flexibility in their design due to the structural characteristics of the electrode materials. Global research is directed towards identifying new class of electrode materials with less risk factors and better structural stability and flexibility. Polymer based electrode materials with inherent flexibility, stability and eco-friendliness can be a suitable choice. One of the prime drawbacks of polymer based cathode materials is the low electronic conductivity. Hence the real task with this class of materials is to get better electronic conductivity with good electrical storage capability. Electronic conductivity can be enhanced by using proper dopants. In the designing of rechargeable Li-ion cells with polymer based cathode active materials, the key issue is to identify the optimum lithiation of the polymer cathode which can ensure the highest electronic conductivity and specific charge capacity possible The development of conducting polymer based rechargeable Li-ion cells with high specific capacity and excellent cycling characteristics is a highly competitive area among research and development groups, worldwide. Polymer based rechargeable batteries are specifically attractive due to the environmentally benign nature and the possible constructional flexibility they offer. Among polymers having electrical transport properties suitable for rechargeable battery applications, polyaniline is the most favoured one due to its tunable electrical conducting properties and the availability of cost effective precursor materials for its synthesis. The performance of a battery depends significantly on the characteristics of its integral parts, the cathode, anode and the electrolyte, which in turn depend on the materials used. Many research groups are involved in developing new electrode and electrolyte materials to enhance the overall performance efficiency of the battery. Currently explored electrolytes for Li ion battery applications are in liquid or gel form, which makes well-defined sealing essential. The use of solid electrolytes eliminates the need for containment of liquid electrolytes, which will certainly simplify the cell design and improve the safety and durability. The other advantages of polymer electrolytes include dimensional stability, safety and the ability to prevent lithium dendrite formation. One of the ultimate aims of the present work is to realize all solid state, flexible and environment friendly Li-ion cells with high specific capacity and excellent cycling stability. Part of the present work is hence focused on identifying good polymer based solid electrolytes essential for realizing all solid state polymer based Li ion cells.The present work is an attempt to study the versatile roles of polyaniline in two different fields of technological applications like nonlinear optics and energy storage. Conducting form of doped PANI films with good extent of crystallinity have been realized using a level surface assisted casting method in addition to the generally employed technique of spin coating. Metal nanoparticles embedded PANI offers a rich source for nonlinear optical studies and hence gold and silver nanoparticles have been used for making the nanocomposites in bulk and thin film forms. These PANI nanocomposites are found to exhibit quite dominant third order optical non-linearity. The highlight of these studies is the observation of the interesting phenomenon of the switching between saturable absorption (SA) and reverse saturable absorption (RSA) in the films of Ag/PANI and Au/PANI nanocomposites, which offers prospects of applications in optical switching. The investigations on the energy storage prospects of PANI were carried out on Li enriched PANI which was used as the cathode active material for assembling rechargeable Li-ion cells. For Li enrichment or Li doping of PANI, n-Butyllithium (n-BuLi) in hexanes was used. The Li doping as well as the Li-ion cell assembling were carried out in an argon filled glove box. Coin cells were assembled with Li doped PANI with different doping concentrations, as the cathode, LiPF6 as the electrolyte and Li metal as the anode. These coin cells are found to show reasonably good specific capacity around 22mAh/g and excellent cycling stability and coulombic efficiency around 99%. To improve the specific capacity, composites of Li doped PANI with inorganic cathode active materials like LiFePO4 and LiMn2O4 were synthesized and coin cells were assembled as mentioned earlier to assess the electrochemical capability. The cells assembled using the composite cathodes are found to show significant enhancement in specific capacity to around 40mAh/g. One of the other interesting observations is the complete blocking of the adverse effects of Jahn-Teller distortion, when the composite cathode, PANI-LiMn2O4 is used for assembling the Li-ion cells. This distortion is generally observed, near room temperature, when LiMn2O4 is used as the cathode, which significantly reduces the cycling stability of the cells.