Double isotherm

Accessible metal fractions were determined by hydrogen chemisorption. The volumetric adsorption experiments were performed at room temperature in a conventional vacuum apparatus. Hydrogen uptake was determined using the double isotherm method, as previously reported (3). The platinum dispersion (D ) was calculated by assuming a... 

Volumetric measurements at room temperature showed that by far the greater part of the adsorption of carbon monoxide on Au/TiC>2 occurred on the support it followed the Langmuir equation and most of it was removable by pumping.23,83 About one-third of the titania surface was able to retain it, but there was little uptake on Au/SiC>2. Use of the double-isotherm method with Au/MgO showed that adsorption onto the metal was complete at about 1 atm, but on various samples the coverage never rose above 18%. On model Au/MgO(100) the maximum coverage attained using a pulsed molecular beam at room temperature was < 10%.54... 

Fig. 12. Double isothermal wire calorimeter probe for low pressure flow system.

The CO chemisorption blank on Carbolac was found to be 0.09 cc/g when reduced at 500°C and zero when reduced at 700°C. The uptake on the Carbolac support was subtracted from the values for all the samples described in this table employing the double isotherm technique. 

Fig. 4.1 Adsorption isotherms where the monolayer is obtained (LHS) directly from the isotherm or (RHS) from application of the double isotherm method.

The catalysts were characterised by BET surface area and CO-chemisorption (carried out at 25°C), An all-glass high vacuum unit capable of producing a vaccum of lO" torr was used for this. X-ray diffraction patterns were recorded on a Phillips PW-101 difractometer using CuKa radiation. Prior to CO chemisorption experiment the catalysts were reduced in hydrogen flow at 400°C for 4h, Irreversible CO uptake was obtained by the double isotherm method. Pd- dispersion was calculated considering a 1 1 stoichiometry between CO and Pd... 

Stahlberg has presented models for ion-exchange chromatography combining the Gouy-Chapman theory for the electrical double layer (see Section V-2) with the Langmuir isotherm (. XI-4) [193] and with a specific adsorption model [194]. 

We start by noting that the Langmuir isotherm approach does not take into account the electrostatic interaction between the dipole of the adsorbate and the field of the double layer. This interaction however is quite important as already shown in section 4.5.9.2. In order to account explicitly for this interaction one can write the adsorption equilibrium (Eq. 6.24) in the form ... 

Figure 6.17. Effective double layer adsorption equilibrium isotherms for kj=l and various values of the parameter Ajll.

As shown in Figure 5.26 and also Figs. 2.6 and 2.15 there is excellent agreement between Eq. (6.40) and experiment. Equation 6.40 is also in excellent qualitative agreement with rigorous quantum mechanical calculations (Fig. 5.56). This provides solid support for the effective double layer isotherm (Eq. 6.36). 

So far we have established that the modified electrochemical Langmuir or effective double layer isotherm (Eq. 6.41)... 

Effective core potential, 269 Effective double layer characterization of, 189 isotherm, 306, 315 kinetic expressions, 316 observations of with STM, 259 stability of, 225, 351, 503 Effectiveness factor of promotion computation of, 505 definition of, 505 Electrocatalysis... 

The benefits of the method are appreciated when the textural parameters are compared. Data derived from N2-physisorption isotherms show that Fenton detemplation leads to improved textural parameters, with BET areas around 945 m g for a pore volume of 1.33 cm g , while calcination leads to reduced textural parameters (667m g 0.96cm g ). T-plot analysis, strictly speaking, is not apphcable for these bi-modal materials but it gives a good estimate. It shows that the micropore volume is doubled, which corresponds to an increase in the calculated micropore area from about... 

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