Coatings, catalyst incorporation

Shi M, Anson FC. MobUities and concentration profiles of counterion catalysts incorporated in Nafion coatings on electrodes. Electrochim Acta 1998 44 1301-5. 

K > Na > Li. After neutralization or removal of the catalyst, fluid polymers are used as is or to formulate grease compounds. If a reactive end blocking group was incorporated during polymerization, the fluid polymer is then useful for making a coating, a sealant, or a Hquid mbber product. 

More recently there have been developed water- resistant phosphorus-based intumescence catalyst. This commercially available product, as an example Phos-Chek P/30 tradename from Monsanto, can be incorporated (with other water insoluble reagents) into water-resistant intumescent coatings of either the alkyd or latex-emulsion type. These intumescent coatings, formulated ac-... 

Firstly, there are technical reasons concerning catalyst and reactor requirements. In the chemical industry, catalyst performance is critical. Compared to conventional catalysts, they are relatively expensive and catalyst production and standardization lag behind. In practice, a robust, proven catalyst is needed. For a specific application, an extended catalyst and washcoat development program is unavoidable, and in particular, for the fine chemistry in-house development is a burden. For coated systems, catalyst loading is low, making them unsuited for reactions occurring in the kinetic regime, which is particularly important for bulk chemistry and refineries. In that case, incorporated monolithic catalysts are the logical choice. Catalyst stability is crucial. It determines the amount of catalyst required for a batch process, the number of times the catalyst can be reused, and for a continuous process, the run time. 

Photocatalytic oxidation of ethanol on Pt/ri02 and Nafion coated Ti02 catalysts were studied using in situ infrared IR techniques. Infrared studies show that the reaction produced acetaldehyde, acetic acid, acetate, formic acid, formate, and CO2/H2O. Modification of the Ti02 catalyst by Pt and Nafion slowed down the oxidation reaction through site blocking. Incorporation of Pt was found to favor formation of formate (HCOO ), indicating Pt decreases the rate of oxidation of formate more than that of its formation. 

The process has been commercially implemented in Japan since 1977 [1] and a decade later in the U.S., Germany and Austria. The catalysts are based on a support material (titanium oxide in the anatase form), the active components (oxides of vanadium, tungsten and, in some cases, of molybdenum) and modifiers, dopants and additives to improve the performance, especially stability. The catalyst is then deposited over a structured support based on a ceramic or metallic honeycomb and plate-type structure on which a washcoat is then deposited. The honeycomb form usually is an extruded ceramic with the catalyst either incorporated throughout the stmcture (homogeneous) or coated on the substrate. In the plate geometry, the support material is generally coated with the catalyst. 

A number of metal porphyrins have been examined as electrocatalysts for H20 reduction to H2. Cobalt complexes of water soluble masri-tetrakis(7V-methylpyridinium-4-yl)porphyrin chloride, meso-tetrakis(4-pyridyl)porphyrin, and mam-tetrakis(A,A,A-trimethylamlinium-4-yl)porphyrin chloride have been shown to catalyze H2 production via controlled potential electrolysis at relatively low overpotential (—0.95 V vs. SCE at Hg pool in 0.1 M in fluoroacetic acid), with nearly 100% current efficiency.12 Since the electrode kinetics appeared to be dominated by porphyrin adsorption at the electrode surface, H2-evolution catalysts have been examined at Co-porphyrin films on electrode surfaces.13,14 These catalytic systems appeared to be limited by slow electron transfer or poor stability.13 However, CoTPP incorporated into a Nafion membrane coated on a Pt electrode shows high activity for H2 production, and the catalysis takes place at the theoretical potential of H+/H2.14... 

Zeolite catalysts and adsorbents have also been incorporated into monolithic contactors by several routes, including extruded zeoHte/binder composites [70], wash-coated ceramic monoliths [71] and corrugated thin-sheet monoliths [72]. 

Tronconi et al. [46] developed a fully transient two-phase 1D + 1D mathematical model of an SCR honeycomb monolith reactor, where the intrinsic kinetics determined over the powdered SCR catalyst were incorporated, and which also accounts for intra-porous diffusion within the catalyst substrate. Accordingly, the model is able to simulate both coated and bulk extruded catalysts. The model was validated successfully against laboratory data obtained over SCR monolith catalyst samples during transients associated with start-up (ammonia injection), shut-down (ammonia... 

The electrode material also may be manipulated to achieve more specific or more reliably controlled performance. Specific catalysts for desired reactions may be incorporated into the electrode material or bound to the surface of the electrode. A present example is the coating of a carbon or other inert electrode with a polymer film impregnated with a mercuric salt. The resulting electrode is catalytic for reduction of metals, such as Pb2+, that are soluble in mercury. This is an area of research that could pay off through qualitative improvements in accuracy, precision, and response time. 

Two ways of incorporating titania onto Cr/silica catalysts are used, and each has certain advantages. In the simplest method the silica surface is coated with a layer of titania by allowing a titanium ester to react with the hydroxyl groups. 

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