"Catalysis by pillared montmorillonites exchanged with transition metals"

The present work is oriented to obtain a comparative evaluation of the physicochemical properties and catalytic activities of iron, aluminium and iron aluminium mixed pillared montmorillonites and their transition metal exchanged analogues. Reactions of industrial importance like Friedel Crafts alkylations, catalytic wet peroxide oxidation of phenol and MTBE synthesis have been selected for the present study. The thesis is structured into seven chapters. First chapter deals with a brief introduction and literature survey on pillared clays. Second chapter explains the materials and methods employed in the work. Results and discussions on the characterisation techniques are described in the third chapter. The subsequent three chapters describe the catalytic activities of pillared clays in the industrially important reactions. Last chapter comprises the summary of the investigations and the conclusions drawn from the earlier chapters

������catalysis by nano sulfated titania modified by transition metals"

in the present study, we have prepared and evaluated the physical and chemical properties and catalytic activities of transition metal loaded sulfated titania via the sol-gel route. Sol-gel method is widely used for preparing porous materials having controlled properties and leads to the formation of oxide particles in nano range, which are spherical or interconnected to each other. Characterization using various physico-chemical techniques and a detailed study of acidic properties are also carried out. Some reactions of industrial importance such as Friedel-Crafts reaction, fen-butylation of phenol,Beckmann rearrangement of cyclohexanone oxime, nitration of phenol and photochemical degradation of methylene blue have been selected for catalytic activity study in the present venture. The work is organized into eight chapters

Catalysis by Enzymes immobilized on Tuned Mesoporous Silica

Mesoporous silica nanoparticles provide a non-invasive and biocompatible delivery platform for a broad range of applications in therapeutics, pharmaceuticals and diagnosis. Additionally, mesoporous silica materials can be synthesized together with other nanomaterials to create new nanocomposites, opening up a wide variety of potential applications. The ready functionalization of silica materials makes them ideal candidates for bioapplications and catalysis. These properties of mesoporous silica like high surface areas, large pore volumes and ordered pore networks allow them for higher loading of drugs or biomolecules. Comparative studies have been made to evaluate the different procedures; much of the research to date has involved quick exploration of new methods and supports. Requirements for different enzymes may vary, and specific conditions may be needed for a particular application of an immobilized enzyme such as a highly rigid support. In this endeavor, mesoporous silica materials having different pore size were synthesized and easily modified with active functional groups and were evaluated for the immobilization of enzymes. In this work, Aspergillus niger glucoamylase, Bovine liver catalase, Candida rugosa lipase were immobilized onto support by adsorption and covalent binding. The structural properties of pure and immobilized supports are analyzed by various characterization techniques and are used for different reactions of industrial applications.

Catalysis by Modified Pillared Clays and Porous Clay Heterostructures

In this venture three distinct class of catalysts such as, pillared clays and transition metal loaded pillared clays , porous clay heterostructures and their transition metal loaded analogues and DTP supported on porous clay heterostructures etc. were prepared and characterized by various physico chemical methods. The catalytic activities of prepared catalysts were comparatively evaluated for the industrially important alkylation, acetalization and oxidation reactions.The general conclusions drawn from the present investigation are ��� Zirconium, iron - aluminium pillared clays were synthesized by ion exchange method and zirconium-silicon porous heterostructures were Summary and conclusions 259 prepared by intergallery template method. Transition metals were loaded in PILCs and PCHs by wet impregnation method. ��� Textural and acidic properties of the clays were modified by pillaring and post pillaring modifications. ��� The shift in 2�� value to lower range and increase in d (001) spacing indicate the success of pillaring process. ��� Surface area, pore volume, average pore size etc. increased dramatically as a result of pillaring process. ��� Porous clay heterostructures have higher surface area, pore volume, average pore diameter and narrow pore size distribution than that of pillared clays. ��� The IR spectrum of PILCs and PCHs are in accordance with literature without much variation compared to parent montmorillonite which indicate that basic clay structure is retained even after modification. ��� The silicon NMR of PCHs materials have intense peaks corresponding to Q4 environment which indicate that mesoporous silica is incorporated between clay layers. ��� Thermo gravimetric analysis showed that thermal stability is improved after the pillaring process. PCH materials have higher thermal stability than PILCs. ��� In metal loaded pillared clays, up to 5% metal species were uniformly dispersed (with the exception of Ni) as evident from XRD and TPR analysis. Chapter 9 260 ��� Impregnation of transition metals in PILCs and PCHs enhanced acidity of catalysts as evident from TPD of ammonia and cumene cracking reactions. ��� For porous clay heterostructures the acidic sites have major contribution from weak and medium acid sites which can be related to the Bronsted sites as evident from TPD of ammonia. ��� Pillared clays got more Lewis acidity than PCHs as inferred from ��- methyl styrene selectivity in cumene cracking reaction. ��� SEM images show that layer structure is preserved even after modification. Worm hole like morphology is observed in TEM image of PCHs materials ��� In ZrSiPCHS, Zr exists as Zr 4+ and is incorporated to silica pillars in the intergallary of clay layers as evident from XPS analysis. ��� In copper loaded zirconium pillared clays, copper exists as isolated species with +2 oxidation state at lower loading. At higher loading, Cu exists as clusters as evident from reduction peak at higher temperatures in TPR. ��� In vanadium incorporated PILCs and PCHs, vanadium exist as isolated V5+ in tetrahedral coordination which is confirmed from TPR and UVVis DRS analysis. ��� In cobalt loaded PCHs, cobalt exists as CoO with 2+ oxidation state as confirmed from XPS. ��� Cerium incorporated iron aluminium pillared clay was found to be the best catalyst for the hydroxylation of phenol in aqueous media due to the additional surface area provided by ceria mesopores and its redox properties. Summary and conclusions 261 ��� Cobalt loaded zirconium porous clay heterostructures were found to be promising catalyst for the tertiary butylation of phenol due to higher surface area and acidic properties. ��� Copper loaded pillared clays were found to be good catalyst for the direct hydroxylation of benzene to phenol. ��� Vanadium loaded PCHs catalysts were found to be efficient catalysts for oxidation of benzyl alcohol. ��� DTP was firmly fixed on the mesoporous channels of PCHs by Direct method and functionalization method. ��� DTP supported PCHs catalyst were found to be good catalyst for acetalization of cyclohexanone with more than 90% conversion.

Molecular computations for reactions and phase transitions: applications to protein stabilization, hydrates and catalysis

In this work we have made significant contributions in three different areas of interest: therapeutic protein stabilization, thermodynamics of natural gas clathrate-hydrates, and zeolite catalysis. In all three fields, using our various computational techniques, we have been able to elucidate phenomena that are difficult or impossible to explain experimentally. More specifically, in mixed solvent systems for proteins we developed a statistical-mechanical method to model the thermodynamic effects of additives in molecular-level detail. It was the first method demonstrated to have truly predictive (no adjustable parameters) capability for real protein systems. We also describe a novel mechanism that slows protein association reactions, called the ���gap effect.��� We developed a comprehensive picture of methioine oxidation by hydrogen peroxide that allows for accurate prediction of protein oxidation and provides a rationale for developing strategies to control oxidation. The method of solvent accessible area (SAA) was shown not to correlate well with oxidation rates. A new property, averaged two-shell water coordination number (2SWCN) was identified and shown to correlate well with oxidation rates. Reference parameters for the van der Waals Platteeuw model of clathrate-hydrates were found for structure I and structure II. These reference parameters are independent of the potential form (unlike the commonly used parameters) and have been validated by calculating phase behavior and structural transitions for mixed hydrate systems. These calculations are validated with experimental data for both structures and for systems that undergo transitions from one structure to another. This is the first method of calculating hydrate thermodynamics to demonstrate predictive capability for phase equilibria, structural changes, and occupancy in pure and mixed hydrate systems. We have computed a new mechanism for the methanol coupling reaction to form ethanol and water in the zeolite chabazite. The mechanism at 400��C proceeds via stable intermediates of water, methane, and protonated formaldehyde.

Catalysis at the University of Southampton

This is a video resource to support the teaching of catalysis at A-level. It features explanations of the underlying theory, coupled with an outline of cutting research in this area of Chemistry at the University of Southampton, which relates to the A-level topic. The video files are in the .zip folder, and instructions for how to access them can be found in the attached document. You will also find a Word document called 'Skeleton notes', which is designed to be printed out by students and completed as they watch the video. We will be seeking feedback from students who use the resource, to find out their views about its effectiveness in educational terms. If you have any comments, or if you spot any errors, please contact Dr David Read (d.read@soton.ac.uk).

Functional studies of the deubiquitinating enzymes USP19, USP4 and UCH-L1

El marcaje de prote��nas con ubiquitina, conocido como ubiquitinaci��n, cumple diferentes funciones que incluyen la regulaci��n de varios procesos celulares, tales como: la degradaci��n de prote��nas por medio del proteosoma, la reparaci��n del ADN, la se��alizaci��n mediada por receptores de membrana, y la endocitosis, entre otras (1). Las mol��culas de ubiquitina pueden ser removidas de sus sustratos gracias a la acci��n de un gran grupo de proteasas, llamadas enzimas deubiquitinizantes (DUBs) (2). Las DUBs son esenciales para la manutenci��n de la homeostasis de la ubiquitina y para la regulaci��n del estado de ubiquitinaci��n de diferentes sustratos. El gran n��mero y la diversidad de DUBs descritas refleja tanto su especificidad como su utilizaci��n para regular un amplio espectro de sustratos y v��as celulares. Aunque muchas DUBs han sido estudiadas a profundidad, actualmente se desconocen los sustratos y las funciones biol��gicas de la mayor��a de ellas. En este trabajo se investigaron las funciones de las DUBs: USP19, USP4 y UCH-L1. Utilizando varias t��cnicas de biolog��a molecular y celular se encontr�� que: i) USP19 es regulada por las ubiquitin ligasas SIAH1 y SIAH2 ii) USP19 es importante para regular HIF-1��, un factor de transcripci��n clave en la respuesta celular a hipoxia, iii) USP4 interact��a con el proteosoma, iv) La quimera mCherry-UCH-L1 reproduce parcialmente los fenotipos que nuestro grupo ha descrito previamente al usar otros constructos de la misma enzima, y v) UCH-L1 promueve la internalizaci��n de la bacteria Yersinia pseudotuberculosis.

New Ruthenium complexes containing N, P and S-donor type of ligands: coordination chemistry, characterization and application to asymetric and non-asymetric catalysis

S��ntesi de nous complexos de Ruteni amb lligands no quirals que tenen per f��rmula [Ru(phen)([9]aneS3)X] (on X = H2O, py i MeCN). Caracteritzaci�� espectrosc��pica electroqu��mica i estructural d'aquesta fam��lia de complexos. Estudi de les seves propietats catal��tiques en front a l'oxidaci�� de substrats org��nics com l'alcohol benz��lic en reaccions d'electrocat��lisi. Avaluaci�� cin��tica dels mecanismes de substituci�� entre els complexos Ru-py i Ru-MeCN. Generaci�� d'un interruptor molecular foto-indu��t. S��ntesi de nous complexos quirals de Ru atropoisom��ricament purs amb lligands oxazol��nics que tenen per f��rmula [Ru(trpy)(Ph-box-R)X] on (X = Cl, H2O, py, MeCN, 2-OH-py). Caracteritzaci�� estructural exhaustiva en estat s��lid (Raig-X) en soluci�� (RMN) i en fase gas (c��lculs DFT). Avaluaci�� de la seva activitat catal��tica en reaccions asimmetriques d'epoxidaci�� de substrats proquirals. S��ntesi de nous lligands polipirid��lics quirals amb simetria C3. Estudi de la seva qu��mica de coordinaci�� i avaluaci�� de la seva activitat catal��tica en reaccions asimmetriques d'oxidaci�� i reducci��.

Exploring the enzymatic landscape: distribution and kinetics of hydrolytic enzymes in soil particle-size fractions

The location of extracellular enzymes within the soil architecture and their association with the various soil components affects their catalytic potential. A soil fractionation study was carried out to investigate: (a) the distribution of a range of hydrolytic enzymes involved in C, N and P transformations, (b) the effect of the location on their respective kinetics, (c) the effect of long-term N fertilizer management on enzyme distribution and kinetic parameters. Soil (silty clay loam) from grassland which had received 0 or 200 kg N ha(-1) yr(-1) was fractionated, and four particle-size fractions (> 200, 200-63, 63-2 and 0. 1-2 mum) were obtained by a combination of wet-sieving and centrifugation, after low-energy ultrasonication. All fractions were assayed for four carbohydrases (beta-cellobiohydrolase, N-acetyl-beta-glucosammidase, beta-glucosidase and beta-xylosidase), acid phosphatase and leucine-aminopeptidase using a microplate fluorimetric assay based on MUB-substrates. Enzyme kinetics (V-max and K-m) were estimated in three particle-size fractions and the unfractionated soil. The results showed that not all particle-size fractions were equally enzymatically active and that the distribution of enzymes between fractions depended on the enzyme. Carbohydrases predominated in the coarser fractions while phosphatase and leucine-aminopeptidase were predominant in the clay-size fraction. The Michaelis constant (K.) varied among fractions, indicating that the association of the same enzyme with different particle-size fractions affected its substrate affinity. The same values of Km were found in the same fractions from the soil under two contrasting fertilizer management regimes, indicating that the Michaelis constant was unaffected by soil changes caused by N fertilizer management. (C) 2004 Elsevier Ltd. All rights reserved.

Anthraquinone catalysis in the glucose-driven reduction of indigo to leuco-indigo

Anthraquinone immobilised onto the surface of indigo microcrystals enhances the reductive dissolution of indigo to leuco-indigo. Indigo reduction is driven by glucose in aqueous NaOH and a vibrating gold disc electrode is employed to monitor the increasing leuco-indigo concentration with time. Anthraquinone introduces a strong catalytic effect which is explained by invoking a molecular "wedge effect'' during co-intercalation of Na+ and anthraquinone into the layered indigo crystal structure. The glucose-driven indigo reduction, which is in effective in 0.1 M NaOH at 65 degrees C, becomes facile and goes to completion in the presence of anthraquinone catalyst. Electron microscopy of indigo crystals before and after reductive dissolution confirms a delamination mechanism initiated at the edges of the plate-like indigo crystals. Catalysis occurs when the anthraquinone-indigo mixture reaches a molar ratio of 1:400 (at 65 degrees C; corresponding to 3 mu M anthraquinone) with excess of anthraquinone having virtually no effect. A strong temperature effect ( with a composite E-A approximate to 120 kJ mol(-1)) is observed for the reductive dissolution in the presence of anthraquinone. The molar ratio and temperature effects are both consistent with the heterogeneous nature of the anthraquinone catalysis in the aqueous reaction mixture.