Equilibrium surface coverage

Some statements referring to nonuniform surfaces are valid irrespective of the form of the distribution function of surface sites with respect to their AGa° values. Using the relative number of site, s, as an independent variable, we obtain the following expression (40) for the equilibrium surface coverage, 9 ... 

According to the assumption made, c is identical for all surface sites. Thus, adsorption coefficients of gases A and A are mutually proportional. Equilibrium surface coverage by gas A is... 

It can be easily seen that the equilibrium surface coverage by gas A ... 

With an H2S/H2 ratio in the gas of 1 ppb, the equilibrium surface coverage of nickel at 500°C is around 70%. This means that all sulfur in the feed is quantitatively adsorbed on the nickel catalyst of a prereformer. The result is not only the deactivation of the prereformer catalyst even at very low sulfur levels, but also the protection of downstream catalysts from poisoning. Sulfur uptake on the catalyst will initially take place as shell poisoning and because of pore diffusion restrictions, it may take years before sulfur reaches the center of the particle. ... 

This equation can be used to derive an expression for the equilibrium surface coverage. For Eq. (19). then and z = 1, /(0) = the adsorption isotherm is... 

Thus we have an expression relating the current density (/) to the cell potential (V) in terms of the equilibrium surface coverage (0o) and the concentration of oxygen at the surface of the electrode (r. o2o ) To complete the derivation, Langmuir s isotherm for chemisorption is introduced to relate the equilibrium surface coverage to the concentration of the adsorbed species ... 

Calculate the equilibrium surface coverage according to the Langmuir isotherm for the nitrogen example of problems 1 and 2. The heat of adsorption is lOkcal/mol, the sticking probability is unity, and... 

Derive the Langmuir isotherm expressions for the equilibrium surface coverages, and of two gases competitively adsorbed on the same surface [equations (3-13)]. 

Brunauer et al. (1938) proposed the following isotherm, which accounts for the effects of temperature and pressure on equilibrium surface coverage ... 

From this equation one can derive an equilibrium surface coverage of the... 

Recall from our previous section on incomplete reaction processes that the ratio of the rate constants for the forward and reverse reaction processes yields the equilibrium constant K for the reaction. Thus, in the case of an incomplete reaction, this equilibrium constant, in concert with the gas-phase CO concentration, would determine the equilibrium surface coverage of CO. This equation is known as the Langmuir isotherm and it is one of a number of physical models that is Irequently encomitered when describing gas-solid adsorption processes. 

We will now examine how the equilibrium surface coverages depend on the adsorption strength of the adsorbing molecule and the influence of temperature and pressure. The equilibrium coverage is given by the requirement that the Gibbs free energy of adsorption is zero ... 

For a steady-state condition at equilibrium potential the rates of both reactions are zero, and the changes in surface coverage 0 with time are dB/dt = 0. The equilibrium surface coverage 0, can be estimated as ... 

As noted in the previous section, the simulation chemical potential, pgcmc, must be interpreted in the context of how the CE Hamiltonian is defined. Additional insight can be gained from understanding how the simulation chemical potential relates to other measurable quantities as well as to the equilibrium surface coverage. 

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