Redox catalyst design

Examination of the cyclic voltammetry (CV) of the Zn-porphyrin dendrimers in THF and CH2C12 with Bu4N+PF6 (0.1 m) electrolyte revealed first oxidation potentials up to 300 mV (THF) less positive than the corresponding values obtained for the unshielded tetraester, Zn-porphyrin core. These preliminary electrochemical experiments suggested dendritic encapsulation of redox-active chromophores can effectively influence the electrophone environment controlled and well-conceived cascade architecture can lead to new avenues of selective redox catalyst design. 

The determination of catalyst composition and the kinetics of epoxide opening constitute the experimental basis for any mechanistic discussion and catalyst design. For this purpose, Zn-reduced THF solutions of the prepar-atively important 21 [44-46], 22 [47], 23, and 24 were analyzed by cyclic voltammetry, a technique uniquely suited to the investigation of redox active... 

Crucial to the success of reactions designed to produce hydrogen via intermolecular electron transfer reactions is the addition of an efficient redox catalyst which allows reduction of protons by the reduced form of the relay (e.g. MV+) formed by the initial photochemical electron transfer. 

The success in this domain has therefore largely been determined by the development of redox catalysts mediating hydrogen and o -gen formation and thus avoiding these radical intermediates. In fact, only throu drastic improvement of previously known and discovery of new redox catalysts has the design of a cyclic water decomposition system operating on four quanta of visible li t become feasible. The performance of these catalysts has to... 

Transition metals exchanged into Y-zeolite offer a basis upon which to build an understanding of the important parameters involved in designing zeolitic redox catalysts. Y-zeolite was chosen for this study because it is the most thoroughly characterized catalytic zeolite. Thus, one can address such questions as what non-framework cation sites are occupied, whether the cations move between sites, whether interactions between the cations themselves are important and how these factors relate to the kinetics of catalytic reactions. 

DeNOx reaction involves a strongly adsorbed NH3 species and a gaseous or weakly adsorbed NO species, but differ in their identification of the nature of the adsorbed reactive ammonia (protonated ammonia vs. molecularly coordinated ammonia), of the active sites (Br0nsted vs. Lewis sites) and of the associated reaction intermediates [16,17]. Concerning the mechanism of SO2 oxidation over DeNOxing catalysts, few systematic studies have been reported up to now. Svachula et al. [18] have proposed a redox reaction mechanism based on the assumption of surface vanadyl sulfates as the active sites, in line with the consolidated picture of active sites in commercial sulfuric acid catalysts [19]. Such a mechanism can explain the observed effects of operating conditions, feed composition, and catalyst design parameters on the SO2 SO3 reaction over metal-oxide-based SCR catalysts. 

Insufficient information exists currently for complex selective reactions, limited to phenomenological results with few electrocatalysts and reactants. The design of polymetallic clusters and of catalysts with controlled crystallite size, the exploration of redox catalysts, the tailoring of the physical catalyst structure, and the selection of reactors and operating conditions to enhance or suppress multiple reaction paths await further study. The exploitation of unconventional reduction or oxidation potential regimes for specificity control, which has been only occasionally attempted or appreciated, appears to be especially attractive. 

Use of Stoichiometric Reactions in the Design of Redox Catalyst for Carbon Dioxide Reduction... 

The NASICON structure was chosen because it can be readily synthesized, is thermally very stable, and can accommodate a large fraction of vacancies and cation substitutions [9-12], In addition, this structure possesses two features which should be important for the catalyst design as envisioned above. First, it is a phosphate and hence expected, owing to its acidic nature, to stabilize the lower oxidation states of transition metals, e.g., V second, owing to its structure, layered octahedral metal centers with variable valence are separated from each other by redox inactive tetrahedral phosphate groups, i.e., the structure provides for isolation of descrete layers. 

Designing Industrial Redox Catalysts for Selective Autoxidations of Hydrocarbons - A New Paradigm... 

The prospect of advancing chemical sensor technology, modelling electron-transfer processes in biological systems and producing new redox catalysts has led to considerable interest in the design and syntheses of redox-active macrocyclic receptor molecules that contain a redox centre in close proximity to a host binding site. ... 

Meyer D, Buhler B, Schmid A (2006) Process and catalyst design objectives for specific redox biocatalysis. Adv Appl Microbiol 59 53-91... 

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