Catalyst impregnation, theory

In the case of functionalized olefins, i.e, where Ri and/or R2 are not simple alkyl chains, it is better to use a Re207/Al203 catalyst. Such catalysts can be prepared by pore-volume impregnation with an aqueous solution of ammonium perrhenate. It is observed that the turnover frequency, i.e. the activity per Re atom, increases considerably with Re207 loading up to monolayer coverage of the alumina surface (about 18 wt.% Re207 for an alumina of 200 m2/g). A theory... 

Another alternative that would help to raise catalyst utilization would be to make CLs of extremely thin two-phase composites. Electroactive Pt (eventually deposited on a substrate) should form the electronically conductive phase. The remaining volume should be filled with liquid water. Since the layer is only a two-phase composite, not impregnated with ionomer, the problem of the protonic contact resistance at the PEM CL interface could be mitigated, making the CCL insensitive to the type of PEM. Using Pois-son-Nemst-Planck theory, it could be shown that close to 100% of the catalyst would be utilized, since transport of oxygen and protons would be unproblematic for such thicknesses ( 100 nm) [129],... 

The effective bed conductivity has a static or zero-flow term, which is usually about 5k when the particles are a porous inorganic material such as alumina, silica gel, or an impregnated catalyst, and kg is the thermal conductivity of the gas. The turbulent flow contribution to the conductivity is proportional to the mass flow rate and particle diameter, and the factor 0.1 in the following equation agrees with the theory for turbulent diffusion in packed beds ... 

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