Zeolite Encapsulated Complexes Of Fe,Co,Ni,Cu And Pd:Synthesis , Characterization And Catalysis-2003

This thesis deals with the synthesis, characterization and catalysis activity studies of some zeolite encapsulated complexes. Encapsulation inside the zeolite cages makes the catalysts more stable. Further, the framework prevents the complexes from dimerising. Catalysis by metal complexes encapsulated in the cavities of zeolites and other molecular sieves has many features of homogeneous, heterogenous and enzymatic catalysis. Serious attempts has been made to gain product selectivity in catalysis .The catalytic activity shown by the encapsulated complexes can be correlated to the structure of the active site inside the zeolite pore. It deals with the studies on the partial oxidation of benzyl alcohol to benzaldehyde. The oxidatio was carried out using hydrogen peroxide as oxidant in presence of PdYDMG and CuYSPP as catalysts. The product (benzaldehyde) was detected using TLC and confirmed using GC.The catalytic activity of the complexes was tested for oxidation under various conditions. The operating conditions like the amount of the catalyst, reaction time, oxidant to substrate ratio, reaction temprature, and solvents have been optimized. No further oxidation products were obtained on continuing the reaction for four hours beyond the optimum time. Maximum conversion was obtained at room temperature and the percentage conversion decreased with increase in temperature. Activity was found to be dependent on the solvent used. With increasing awareness about the dangers of environmental degradation, research in chemistry is getting increasing geared to the development of “green chemistry,” by designing environmentally friendly products and processes that bring down the generation and use of hazardous substances.

Studies On Supported Cobalt (Ii), Nickel (Ii) and Copper (Ii) Complexes Of O-Phenylenediamine and Schiff Bases Derived from 3-Hydroxyquinoxaline-2-Carboxaldehyde

The thesis deals with the synthesis, characterization and catalytic activity studies of supported cobalt(ii), nickel(II) and copper(II) complexes of O-phenylenediamine and Schiff bases derived from 3-hydroxyquinoxaline -2-carboxaldehyde. Zeolite encapsulation and polymer anchoring was employed for supporting the complexes. The characterization techniques proved that the encapsulation as well as polymer supporting has been successfully achieved. The catalytic activity studies revealed that the activities of the simple complexes are improved upon encapsulation. Various characterization techniques are used such as, chemical analysis, EPR, magnetic measurements, FTIR studies, thermal analysis, electronic spectra, XRD, SEM, surface area, and GC.The present study indicated that the that the mechanism of oxidation of catechol and DTBC by hydrogen peroxide is not altered by the change in the coordination sphere around the metal ion due to encapsulation. This fact suggests outer sphere mechanism for the reactions. The catalytic activity by zeolite encapsulated complex was found to be slower than that by the neat complex. The slowing down of the reaction in the zeolite case is probably due to the constraint imposed by the zeolite framework. The rate of DTBC ( 3,5-di-tert-butylchatechol)oxidation was found to be greater than the rate of catechol oxidation. This is obviously due to the presence of electron donating tertiary butyl groups.

Studies on Lactic Acid Bacteria from Tropical Fish and Shellfish

In this study, an attempt has been made to gather enough information regarding lactic acid bacteria from fish and shellfish of tropical regions. The occurrence and distribution of lactic acid bacteria in fresh and frozen marine fish and shellfish, farmed fish and shellfish, cured and pickled fish and shellfish have been investigated. Lactic Acid Bacteria (LAB) have for centuries been responsible for the fermentative preservation of many foods. They are used to retard spoilage and preserve foods through natural fermentations. They have found commercial applications as starter cultures in the dairy, baking, meat, fish, and vegetable and alcoholic beverage industries. They are industrially important organisms recognized for their fermentative ability as well as their nutritional benefits. These organisms produce various compounds such as organic acids, diacetyl, hydrogen peroxide and bacteriocins or bactericidal proteins during lactic fermentations.Biopreservation of foods using bacteriocin producing LAB cultures is becoming widely used. The antimicrobial effect of bacteriocins and other compounds produced during fermentation of carbohydrates are well known to inhibit the growth of certain food spoiling bacteria as well as a limited group of food poisoning and pathogenic bacteria LAB like Lactobacillus plantarum are widely used as starter cultures for the Production of fish ensilage. The present study is the first quantitative and qualitative study on the occurrence and distribution of lactic acid bacteria in fresh and frozen fish and prawn. It is concluded that Lactobacillus plantaruni was the predominant lactobacillus species in fresh and frozen fish and shellfish. The ability of selected Lactobacillus cultures to grow at low temperatures, high salt content, produce bacteriocins, rapidly ferment sugars and decrease the pH make them potential candidates for biopreservation of fish and shellfish.

Studies on Some Simple and Zeolite-Y Encapsulated 3d-Transition Metal Complexes of Schiff Bases Derived From 2-Aminobenzothiazole

In this regard Schiff base complexes have attracted wide attention. Furthermore, such complexes are found to play important role in analytical chemistry, organic synthesis, metallurgy, refining of metals, electroplating and photography. Many Schiff base complexes are reported in literature. Their properties depend on the nature of the metal ion as well as on the nature of the ligand. By altering the ligands it is possible to obtain desired electronic environment around the metal ion. Thus there is a continuing interest in the synthesis of simple and zeolite encapsulated Schiff base complexes of metal ions. Zeolites have a number of striking structural similarities to the protein portion of natural enzymes. Zeolite based catalysts are known for their remarkable ability of mimicking the chemistry of biological systems. In view of the importance of catalysts in all the areas of modern chemical industries, an effort has been made to synthesize some simple Schiff base complexes, heterogenize them by encapsulating within the supercages of zeoliteY cavities and to study their applications. The thesis deals with studies on the synthesis and characterization of some simple and zeoliteY encapsulated Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes and on the catalytic activity of these complexes on some oxidation reactions. Simple complexes were prepared from the Schiff base ligands SBT derived from 2-aminobenzothiazole and salicylaldehyde and the ligand VBT derived from 2-aminobenzothiazole and vanillin (4-hydroxy-3- methoxybenzaldehyde). ZeoliteY encapsulated Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes of Schiff base ligands SBT and VBT and also of 2-aminobenzothiazole were synthesized. All the prepared complexes were characterized using the physico-chemical techniques such as chemical analysis (employing AAS and CHN analyses), magnetic moment studies, conductance measurements and electronic and FTIR spectra. EPR spectra of the Cu(II) complexes were also carried out to know the probable structures and nature of Cu(II) complexes. Thermogravimetric analyses were carried out to obtain the information regarding the thermal stability of various complexes. The successful encapsulations of the complexes within the cavities of zeoliteY were ascertained by XRD, surface area and pore volume analysis. Assignments of geometries of simple and zeoliteY encapsulated complexes are given in all the cases. Both simple and zeoliteY encapsulated complexes were screened for catalytic activity towards oxidation reactions such as decomposition of hydrogen peroxide, oxidation of benzaldehyde, benzyl alcohol, 1-propanol, 2-propanol and cyclohexanol.

Zeolite-encapsulated Co(II), Ni(II) and Cu(II) complexes as catalysts for partial oxidation of benzyl alcohol and ethylbenzene

Co(II), Ni(II) and Cu(II) complexes of dimethylglyoxime and N,N-ethylenebis(7-methylsalicylideneamine) have been synthesized in situ in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. The hybrid materials obtained have been characterized by elemental analysis, SEM, XRD, surface area, pore volume, magnetic moment, FTIR, UV-Vis and EPR techniques. Analysis of data indicates the formation of complexes in the pores without affecting the zeolite framework structure, the absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activities for hydrogen peroxide decomposition and oxidation of benzyl alcohol and ethylbenzene of zeolite complexes are reported. Zeolite Cu(II) complexes were found to be more active than the corresponding Co(II) and Ni(II) complexes for oxidation reactions. The catalytic properties of the complexes are influenced by their geometry and by the steric environment of the active sites. Zeolite complexes are stable enough to be reused and are suitable to be utilized as partial oxidation catalysts.

Synthesis and Characterisation of New Transition Metal Complexes of Schiff Bases Derived from 3-hydroxyquinoxaline-2- carboxaldehyde and Application of Some ofthese Complexes as Hydrogenation and Oxidation Catalysts

The thesis deals with studies on the synthesis, characterisation and catalytic applications of some new transition metal complexes of the Schiff bases derived from 3-hydroxyquinoxaline 2-carboxaldehyde.. Schiff bases which are considered as ‘privileged ligands’ have the ability to stabilize different metals in different oxidation states and thus regulate the performance of metals in a large variety of catalytic transformations. The catalytic activity of the Schiff base complexes is highly dependant on the environment about the metal center and their conformational flexibility. Therefore it is to be expected that the introduction of bulky substituents near the coordination sites might lead to low symmetry complexes with enhanced catalytic properties. With this view new transition metal complexes of Schiff bases derived from 3-hydroxyquinoxaline-2-carboxaldehyde have been synthesised. These Schiff bases have more basic donor nitrogen atoms and the presence of the quinoxaline ring may be presumed to build a favourable topography and electronic environment in the immediate coordination sphere of the metal. The aldehyde was condensed with amines 1,8-diaminonaphthalene, 2,3-diaminomaleonitrile, 1,2-diaminocyclohexane, 2-aminophenol and 4-aminoantipyrine to give the respective Schiff bases. The oxovanadium(IV), copper(II) and ruthenium(II)complexes of these Schiff bases were synthesised and characterised. All the oxovanadium(IV) complexes have binuclear structure with a square pyramidal geometry. Ruthenium and copper form mononuclear complexes with the Schiff base derived from 4- aminoantipyrine while binuclear square planar complexes are formed with the other Schiff bases. The catalytic activity of the copper complexes was evaluated in the hydroxylation of phenol with hydrogen peroxide as oxidant. Catechol and hydroquinone are the major products. Catalytic properties of the oxovanadium(IV) complexes were evaluated in the oxidation of cyclohexene with hydrogen peroxide as the oxidant. Here allylic oxidation products rather than epoxides are formed as the major products. The ruthenium(II) complexes are found to be effective catalysts for the hydrogenation of benzene and toluene. The kinetics of hydrogenation was studied and a suitable mechanism has been proposed.

Studies on Simple and Encapsulated Transition Metal Complexes of Schiff Bases Derived from Diaminonaphthalene

Schiff base complexes of transition metal ions have played a significant role in coordination chemistry.In the present study we have synthesized some new Mn(II),Co(II) and Cu(II) complexes of Schiff bases derived from 1,8-diaminonaphthalene.Even though we could not isolate theses Schiff bases (as they readily cyclise to form the perimidine compounds),we were able to characterize unequivacally the complexes synthesized from these compounds as complexes of Schiff Bases. We Synthesized three perimidine derivatives ,2-(quinoxalin-2-yl)-2,3-dihydro-1H-perimidine,2-(2,3-dihydro-1H-perimidin-2-yl)-6-methoxyphenol and 4-(2,3-dihyro-1H-perimidin-2-yl)-2-methoxyphenol by the condensation of 1,8-diaminonaphthalene with quinoxaline-2-carboxaldehyde,2- hydroxy-3-methoxybenzaldehyde or 4-hydroxy-3-methoxybenzaldehyde respectively.Theses compounds were used as precursor ligands for the preparation of Schiff base complexes.The complexes were characterized by using elemental analysis ,conductance and magnetic susceptibility measuremets ,infrared and UV-Visible spectroscopy ,thermogravimetric analysis and EPR spectroscopy .We also encapsulated the complexes in zeolite Y matrix and these encapsulated complexes were also characterized. We have also tried theses complexes as catalysts in the oxidation of cyclohexanol and decomposition of hydrogen peroxide.

Phytochemical investigations on ‘black glumed’ Njavara (Oryza sativa L.), the medicinal rice, as compared to staple varieties and evaluation of their antioxidant, anti-inflammatory and anticancer effects

The study was planned to investigate the bioactive compounds in Njavara compared to staple varieties and their bioactivity to substantiate the medicinal properties. Results of the study on chemical indices, antioxidant activity and antiinflammatory activity (in vivo) of Njavara black rice bran and rice in comparison with non-medicinal varieties like Sujatha and Palakkadan Matta rice bran and rice are given. The phytochemical investigation and quantification of Njavara extracts in comparison with staple varieties are detailed in this study. The last chapter is divided in three sections (A, B and C). Section A comprises the antioxidant activity by in vitro assays like DPPH, superoxide anion radical and hydrogen peroxide scavenging activity of the compounds. Also, theoretical studies using DFT were carried out based on DPPH radical scavenging activity for understanding the radical stability and mechanism of antioxidant activity. Section B comprises the anti-inflammatory activity of the identified compounds namely tricin and two flavonolignans in both in vivo and in vitro models. Section C describes the cytotoxicity of the rare flavonolignans, tricin 4’-O-(erythro-β-guaiacylglyceryl) ether and tricin 4’-O-(threo-β-guaiacylglyceryl) ether towards multiple cancer cells belonging to colon, ovarian and breast tumours.

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 .

Vanadia Supported on Rice Husk Silica Promoted Rare Earth Oxides

The selective oxidation of alkylaromatics is one of the main processes since the reaction products are important as intermediates in numerous industrial organic chemicals. Side-chain oxidation of alkyl aromatic compounds catalyzed by heterogeneous catalysts using cleaner peroxide oxidants is an especially attractive goal since classical synthetic laboratory procedures preferably use permanganate or acid dichromate as stoichiometric oxidants. In spite of many studies, there are very few which use hydrogen peroxide as a source of oxygen in the C-H activation of alkanes. Eflective utilization of ethylbenzene, available in the xylene stream of the petrochemical industry to more value added products is a promising one in chemical industry. The oxidation products of ethylbenzene are widely employed as intermediates in organic, steroid and resin synthesis.

Colour Removal From Dye-House Efiluents Using Zero-Valent iron and Fenton Oxidation

This thesis Entitled Colour removal from dye house effluents using zero valent iron and fenton oxidation.Findings reported on kinetic profile during oxidation of dyes with Fenton’s reagent are in good agreement with observations of earlier workers on other organic substrates. This work goes a step further. Critical concentration of the dye at which the reaction mechanism undergoes transition has been identified.The oxidation of Reactive Yellow showed that the initial rates for decolorization increased linearly with an increase in hydrogen peroxide concentration over the range studied. Fenton oxidation of all dyes except Methylene Blue showed that the initial rates increased linearly with an in the ferrous sulphate concentration. This increase was observed only up to an optimum concentration beyond which further increase resulted in a decrease in the initial rates. Variation of initial rates with Ferrous sulphate concentration resulted in a linear plot passing through the origin indicating that the reaction is first order with respect to ferrous sulphate.

Studies on Advanced Oxidation Processes for the Removal of Acetamiprid from Wastewater

Pollution of water with pesticides has become a threat to the man, material and environment. The pesticides released to the environment reach the water bodies through run off. Industrial wastewater from pesticide manufacturing industries contains pesticides at higher concentration and hence a major source of water pollution. Pesticides create a lot of health and environmental hazards which include diseases like cancer, liver and kidney disorders, reproductive disorders, fatal death, birth defects etc. Conventional wastewater treatment plants based on biological treatment are not efficient to remove these compounds to the desired level. Most of the pesticides are phyto-toxic i.e., they kill the microorganism responsible for the degradation and are recalcitrant in nature. Advanced oxidation process (AOP) is a class of oxidation techniques where hydroxyl radicals are employed for oxidation of pollutants. AOPs have the ability to totally mineralise the organic pollutants to CO2 and water. Different methods are employed for the generation of hydroxyl radicals in AOP systems. Acetamiprid is a neonicotinoid insecticide widely used to control sucking type insects on crops such as leafy vegetables, citrus fruits, pome fruits, grapes, cotton, ornamental flowers. It is now recommended as a substitute for organophosphorous pesticides. Since its use is increasing, its presence is increasingly found in the environment. It has high water solubility and is not easily biodegradable. It has the potential to pollute surface and ground waters. Here, the use of AOPs for the removal of acetamiprid from wastewater has been investigated. Five methods were selected for the study based on literature survey and preliminary experiments conducted. Fenton process, UV treatment, UV/ H2O2 process, photo-Fenton and photocatalysis using TiO2 were selected for study. Undoped TiO2 and TiO2 doped with Cu and Fe were prepared by sol-gel method. Characterisation of the prepared catalysts was done by X-ray diffraction, scanning electron microscope, differential thermal analysis and thermogravimetric analysis. Influence of major operating parameters on the removal of acetamiprid has been investigated. All the experiments were designed using central compoiste design (CCD) of response surface methodology (RSM). Model equations were developed for Fenton, UV/ H2O2, photo-Fenton and photocatalysis for predicting acetamiprid removal and total organic carbon (TOC) removal for different operating conditions. Quality of the models were analysed by statistical methods. Experimental validations were also done to confirm the quality of the models. Optimum conditions obtained by experiment were verified with that obtained using response optimiser. Fenton Process is the simplest and oldest AOP where hydrogen peroxide and iron are employed for the generation of hydroxyl radicals. Influence of H2O2 and Fe2+ on the acetamiprid removal and TOC removal by Fenton process were investigated and it was found that removal increases with increase in H2O2 and Fe2+ concentration. At an initial concentration of 50 mg/L acetamiprid, 200 mg/L H2O2 and 20 mg/L Fe2+ at pH 3 was found to be optimum for acetamiprid removal. For UV treatment effect of pH was studied and it was found that pH has not much effect on the removal rate. Addition of H2O2 to UV process increased the removal rate because of the hydroxyl radical formation due to photolyis of H2O2. An H2O2 concentration of 110 mg/L at pH 6 was found to be optimum for acetamiprid removal. With photo-Fenton drastic reduction in the treatment time was observed with 10 times reduction in the amount of reagents required. H2O2 concentration of 20 mg/L and Fe2+ concentration of 2 mg/L was found to be optimum at pH 3. With TiO2 photocatalysis improvement in the removal rate was noticed compared to UV treatment. Effect of Cu and Fe doping on the photocatalytic activity under UV light was studied and it was observed that Cu doping enhanced the removal rate slightly while Fe doping has decreased the removal rate. Maximum acetamiprid removal was observed for an optimum catalyst loading of 1000 mg/L and Cu concentration of 1 wt%. It was noticed that mineralisation efficiency of the processes is low compared to acetamiprid removal efficiency. This may be due to the presence of stable intermediate compounds formed during degradation Kinetic studies were conducted for all the treatment processes and it was found that all processes follow pseudo-first order kinetics. Kinetic constants were found out from the experimental data for all the processes and half lives were calculated. The rate of reaction was in the order, photo- Fenton>UV/ H2O2>Fenton> TiO2 photocatalysis>UV. Operating cost was calculated for the processes and it was found that photo-Fenton removes the acetamiprid at lowest operating cost in lesser time. A kinetic model was developed for photo-Fenton process using the elementary reaction data and mass balance equations for the species involved in the process. Variation of acetamiprid concentration with time for different H2O2 and Fe2+ concentration at pH 3 can be found out using this model. The model was validated by comparing the simulated concentration profiles with that obtained from experiments. This study established the viability of the selected AOPs for the removal of acetamiprid from wastewater. Of the studied AOPs photo- Fenton gives the highest removal efficiency with lowest operating cost within shortest time.

Sono, Photo and Sonophoto Catalytic Removal of Chemical and Bacterial Pollutants from Wastewater

The term ‘water pollution’ broadly refers to the contamination of water and water bodies (e.g. lakes, rivers, oceans, groundwater etc). Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove the harmful contaminants. This affects not only the plants and organisms living in these bodies of water but also the entire natural biological communities and the biodiversity.Advanced Oxidation Processes (AOPs) have been tested as environment-friendly techniques for the treatment of contaminated water, in view of their ability to convert pollutants into harmless end products. These techniques refer to a set of treatment procedures designed to remove organic or inorganic contaminants in wastewater by oxidation. The contaminants are oxidized by different reagents such as air, oxygen, ozone, and hydrogen peroxide which are introduced in precise, preprogrammed dosages, sequences and combinations under appropriate conditions. The procedure when combined with light in presence of catalyst is known as photocatalysis. When ultrasound (US) is used as the energy source, the process is referred as sonication. Sonication in presence of catalyst is referred as sonocatalysis. Of late, combination of light and sound as energy sources has been tested for the decontamination of wastewater in the presence of suitable catalyst. In this case, the process is referred as sonophotocatalysis. These AOPs are specially advantageous in pollution control and waste water treatment because unlike many other technologies, they do not just transfer the pollutant from one phase to another but completely degrade them into innocuous substances such as CO2 and H2O.