Catalyst adsorptive capacity

Mr = catalyst adsorption capacity for thiophene, kmol/kg-cat Mrn = thiophene capacity for cycle n, kmol/kg-cat MWg = molecular weight of gas, kg/kmol F — pressure, Pa... 

Moreover, it was found that 1) higher amounts of CO can be bound on the catalyst active sites, under conditions compatible with the operation of PEM-FCs 2) at rising temperatures, catalyst adsorptive capacity decreases while the degree of surface heterogeneity increases since new groups of active sites appear, in the presence as well as in... 

Ammonia adsorption-desorption + Temperature Programmed Desorption (TPD) runs [11] were performed in order to study the adsorption-desorption of NH3 onto the catalyst. Experiments were typically performed at a GHSV of 92,000 h by feeding 1,000 ppm of ammonia in the presence of 2 % O2 and 1 % H2O at constant adsorption temperature (between 200 and 400 °C) when the catalyst adsorption capacity was saturated, NH3 and O2 were shut off and a temperature ramp from 50 to 550 °C at 15 °C/min was started. Temperature Programmed Reaction (TPR) runs [11] were performed to study the gas-phase reactivity on increasing temperature the reactants were fed at constant temperature, then a temperature ramp at 2, 10, or 20 °C/min was run. TPR experiments were typically carried out in the presence of oxygen (2 %) and water vapor (1 %) with GHSV between 90,000 and 230,000 h the reactant feed concentration varied between 250 and 1,000 ppm. 

We have also tried the trapping reactor system, in which ammonia is trapped on the catalyst/adsorbent and microwave is irradiated intermittently. However, due to the small specific surface area and the small ammonia adsorption capacity on the employed CuO, the trapping system was not effective compared to the continuous irradiation. Further study should be made to develop a material having high ammonia adsorption capacity and high efficiency for microwave absorption. Supported CuO on high surface area material or preparation of high surface area CuO can be effective. 

Alumina, 2 345t 5 582. See also Activated alumina Aluminum oxide (alumina) Bauxite(s) Calcined alumina Fused alumina Tabular alumina in the activated catalyst layer, 10 41 adsorption capacity vs. years of service, 1 630... 

It is important to note that adsorption does not necessarily lead to a catalytic reaction but the surface catalyzed reactions always occur through adsorption. In their catalytic action, the surfaces are specific in nature. Ni and Cu surfaces are very good catalysts for hydrogenation processes. The physical nature of a surface also influences its catalytic efficiency. Those atoms, which are at the peaks, edges etc. have high residual fields and are likely to have greater adsorption capacity. Taylor (1925) postulated that the adsorption and subsequent reaction takes place preferentially on certain parts of the surface, which are called active centers. The active center may constitute a small portion only of the total surface. Moreover, all active centers where adsorption occurs are not always catalytically effective. 

It should be noted that the effectiveness of a combustion promoter decreases with Increasing regenerator temperature. The reason is that the rate of oxidation of SO to SO increases with temperature, while the SOx adsorptive capacity of the SOx catalyst decreases. Therefore, at some temperature, the rate of oxidation of SO to SO is fast enough, without combustion promoter, to supply all the SO which the SOx catalyst can accommodate. That temperature would vary for different SOx catalyst systems. For DA-250 + Additive R it is about 1425 F. 

On the other hand, an attempt to accelerate the step of coordination of the substrate to the Cu catalyst was successful because it used the hydrophobic domain of the polymer ligand156 That was the oxidation catalyzed by polymer-Cu complexes in a dilute aqueous solution of phenol, which occurred slowly. The substrate was concentrated in the domain of the polymer catalyst and was effectively catalyzed by Cu in the domain. A relationship was found to exist between the equilibrium constant (Ka) for the adsorption of phenol on the polymer ligand and the catalytic activity (V) of the polymer-ligand-Cu complex for various polymer ligands K a = 0.21 1/mol and V = 1(T6 mol/1 min for QPVP, K a = 26 and V = 1(T4 for PVP, K a = 52 and V = 10-4 for the copolymer of styrene and 4-vinylpyridine (PSP) (styrene content 20%), and K a = 109 and V = 10-3 for PSP (styrene content 40%). The V value was proportional to the Ka value, and both Ka and V increased with the hydrophobicity of the polymer ligand. The oxidation rate catalyzed by the polymer-Cu complex in aqueous solutions depended on the adsorption capacity of the polymer domain. 

The co-existence of at least two modes of ethylene adsorption has been clearly demonstrated in studies of 14C-ethylene adsorption on nickel films [62] and various alumina- and silica-supported metals [53,63—65] at ambient temperature and above. When 14C-ethylene is adsorbed on to alumina-supported palladium, platinum, ruthenium, rhodium, nickel and iridium catalysts [63], it is observed that only a fraction of the initially adsorbed ethylene can be removed by molecular exchange with non-radioactive ethylene, by evacuation or during the subsequent hydrogenation of ethylene—hydrogen mixtures (Fig. 6). While the adsorptive capacity of the catalysts decreases in the order Ni > Rh > Ru > Ir > Pt > Pd, the percentage of the initially adsorbed ethylene retained by the surface which was the same for each of the processes, decreased in the order... 

---