Catalysts adsorption

What these successful and sometimes serendipitous applications of adsorptive catalysts have in common are the low concentrations of reactants and short cycle times , which mean that relatively small amounts of material have to be adsorbed. The integration of the adsorptive functionality does not therefore really interfere with the catalytic activity. The objective is primarily to ensure high performance in the presence of the fluctuating concentrations and flows that often characterize end-of-pipe treatment stages. 

Tawara et al.159 reported an adsorptive catalyst (Ni/ZnO) for removing sulfur in kerosene to less than O.lppmw in the temperature range between 270 and 300 °C in H2 atmosphere under a pressure of 0.60 MPa. The principle in this process is based on the following reactions ... 

MAJOR PRODUCT APPLICATIONS composites, ceramics, refractories, abrasives, copy toner, electro-optic devices, polishing, electrical and engineering components, acid adsorption, catalyst, nanocomposites... 

The rate controlling step for reaction involves methane adsorption. Catalyst structure has a marked effect on the kinetics of the reaction. Thus, under certain conditions the rate of reaction over a Ni/Kieselguhr catalyst at 911 K is first order with respect to the partial pressure of CH4 and independent of H2O and product partial P, while for other nickel catalysts the rate depends on the partial P of H2O, H2, and CO. ... 

Since nitrogen adsorption-desorption isotherms provide considerable information on the physical structure of cracking catalysts, the methods used in interpreting isotherm data will be briefly considered. In this connection it will be convenient to refer to the isotherms of some representative cracking catalysts and certain related materials presented in Fig. 2. More detailed plots of the isotherms may be found in subsequent sections. In all cases of hysteresis presented in Fig. 2 the upper portion of the hysteresis loop represents desorption and the lower curve represents adsorption. Catalyst characteristics of principal significance obtained from these plots are listed in Table I. As pointed out above the adsorption-desorption isotherms yield at once surface area, pore volume, and pore radius information. 

A Setaram C80 differential microcalorimeter coupled to an evacuable glass gas-handling system was used to monitor ammonia adsorption and associated enthalpies of adsorption. Catalyst samples (ca. 150 mg dry weight) were conditioned in the calorimeter at 100 °C under vacuum for two hours, with an empty reference cell. Successive pulses of ammonia (ca. 0.06 mmol) were introduced to the sample at 100 °C. Enthalpy changes associated with each dose were converted to molar enthalpies of adsorption and are expressed as functions of resin coverage. Further details of the technique have been reported previously. ... 

Figure L9 An iron panicle with one surface covered with a iTKWOfayef of gold atoms. When it comes to surface properties sircK is adsorption or catalysis, one monolayer of atoms is all that i> needed to carry out the necessary chemistry, Because of the very few atoms needed, such a device is Inexpensive. For other applications a thin him nf jp Id 50 layers is needed. For this reason, thin tilms arc very often utilized to carry oul surfaee Tcaclions (adsorption, catalysts] and to impart mcdianTcal properties fhardneBS. luhrica-lion). optical pmpcrtics (reflectivity, color]. and eltc-incat properties (conductivity, charge retention).

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