58 research outputs found
Murine T-Cell Transfer Colitis as a Model for Inflammatory Bowel Disease.
No full textInflammatory bowel disease (IBD) is a group of severe chronic inflammatory conditions of the human gastrointestinal tract. Murine models of colitis have been invaluable tools to improve the understanding of IBD development and pathogenesis. While the disease etiology of IBD is complex and multifactorial, CD4+ T helper cells have been shown to strongly contribute to the disease pathogenesis of IBD. Here, we present a detailed protocol of the preclinical model of T-cell transfer colitis, which can easily be utilized in the laboratory to study T helper cell functions in intestinal inflammation
An exploration of Silsesquioxanes and Zeolites using High-Speed experimentation
No full textCombinatorial Chemistry and High-Speed Experimentation techniques allow the rapid preparation and testing of large numbers of samples by using automated workstations. These techniques are increasingly applied to various fields of chemical research and particularly to catalysis. In this project, High-Speed Experimentation techniques were used to study two families of compounds with a silicon-oxygen framework: silsesquioxanes and zeolites. Silsesquioxanes are inorganic-organic hybrid materials with broad applications as model compounds for silica surfaces and as ligands in coordination chemistry and catalysis. Here, the synthesis of incompletely condensed silsesquioxanes as precursors for titanium catalysts active in the epoxidation of alkenes was optimised by means of High-Speed Experimentation techniques. This thorough study led to the identification of a number of trends, to new and more efficient methods to synthesise known silsesquioxanes and to the discovery of new silsesquioxane precursors for active catalysts. The most interesting results were reproduced at a conventional laboratory scale and the silsesquioxane products were fully characterised. One of these silsesquioxane structures was used to prepare an osmium complex that proved to be a useful model compound for a known heterogeneous catalyst and an active and safe homogenous catalyst for the dihydroxylation of alkenes. Zeolites are microporous crystalline materials with applications as heterogeneous catalysts, ion-exchangers and molecular sieves. The synthesis of aluminium-rich zeolite beta was investigated by means of High-Speed Experimentmation techniques in order to identify the lowest Si/Al ratio to obtain pure zeolite beta with hydrothermal methods.Applied Science
Chiral dirhodium catalysts immobilised in porous hosts: Synthesis and performance
No full textThe main objective of this research is to modify the catalytic properties of homogeneous chiral dirhodium catalysts upon immobilisation on the porous support materials silica, MCM-41 and TUD-1. The catalysts were immobilised via ligand exchange of one chiral ligand with a carboxylate tether group. This influences the enantio- and trans/cis selectivity of the catalysts in the cyclopropanation reaction of styrene with ethyl or tert-butyl diazoacetate and the Si-H insertion reaction of dimethylphenylsilane with methyl phenyldiazoacetate. The results show that it is possible to influence the selectivity of these catalysts by immobilising them. Leaching of the catalyst from the carrier materials remains a problem. Full conversions are still possible upon recycling, but analysis shows that a significant amount of rhodium leaches. In some cases the active catalyst leaches, in others the filtrate is not active, so non-active rhodium leaches. Future work needs to be addressed to the optimisation of the constraint induced by the pore walls as well as to the problem of leaching. The former would be greatly facilitated by computational modelling studies and the latter by ligands that are giving a more stable complex (e.g. four- or six-dentate ones).Applied Science
Functionalized TUD-1: Synthesis, characterization and (photo-)catalytic performance
No full textThe new mesoporous material; TUD-1 is chosen of which the synthesis, characterization, and functionalization for (photo)-catalytic performance are extensively investigated in this study. The synthesis of the new catalytic materials M TUD-1 (M = Ti, V, Cr, Mo, Fe, Co and Cu) is carried out through an easy one-pot synthesis procedure, mainly depends on the addition of a small organic, cost-effective template triethanolamine together with the desired metal source and the silica source. The product; M-TUD-1 is a three-dimensional, open structured mesoporous siliceous material. The amount of metal added during the synthesis played the essential rule in the formation of different active site species (i.e. isolated, nano-particles and/or bulk crystals of metal oxide) in the TUD-1 matrix. The prepared materials are characterized by various characterization techniques (physical: X-ray diffraction, N2 sorption measurements SEM and HR-TEM and chemical: 29Si NMR, elemental analysis, and UV-VIS- and Raman spectroscopy). And their catalytic performance is tested in four different catalytic applications: selective photo-oxidation of propane, selective oxidation of cyclohexane, Friedel-Crafts benzylation of benzene, and laughing gas (N2O) decomposition. Indeed, the three-dimensional open structure of M-TUD-1 increases the accessibility to the active sites and hence, the (photo-)catalytic performance of M TUD-1 is ranked against their peers under comparable conditions: In the photo-oxidation of propane, Ti-TUD-1 exhibits a 2-2.5 times higher acetone selectivity than commercial TiO2. In the same reaction, Cr-TUD-1 is 5-6 times more active than SiO2 supported Cr at the same chromium loading. An important observation is that certain products (acetone, water) are less strongly adsorbed on TUD-1 than on zeolite-Y. In Friedel-Crafts benzylation of benzene, Fe-TUD-1 shows unique activity, which is benchmarked against other reported micro- (ZSM-5) and mesoporous systems (MCM-41 and HMS). In N2O decomposition, the activity reported over M-TUD-1 is less than reported for analogous M-ZSM-5. However, M-TUD-1 shows a better behaviour as a support than other mesoporous materials e.g. M-SBA-15, M-MCM-41. In conclusion, the present study shows that TUD-1 is not only just an interesting, but also an important support which can contain, in a controllable way, different active sites species, and that it can play a significant role in different catalytic application.Applied Science
Inorganic oxides with mesoporosity or combined meso-and microporosity and process for the preparation thereof
No full textBimodal inorganic material that in a pore size distribution plot has distinct mesopore and micropore peaks. A process for producing a bimodal material or a material that contains essentially only mesopores involves heating an inorganic oxide in the presence of material that bonds to the inorganic oxide by hydrogen bonding. The micropores may or may not include a crystalline structure.Applied Science
Fully coordinated silica nanoclusters: (SiO2)(N) molecular rings
No full textA new form of finite silica with edge-sharing SiO2 units connected in a ring is proposed. High-level density-functional calculations for (SiO2)(N), N = 4-14, show the rings to be energetically more stable than the corresponding (SiO2)(N) linear chains for N > 11. The rings display frequency modes in remarkable agreement with infrared bands measured on dehydrated silica surfaces indicating their potential as models of strained extended silica systems. Silica rings, if synthesized, may also be useful precursors for new bulk-silica polymorphs with tubular or porous morphologies
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