Desorption lineshape

Fig. 20. The effect of the precursor state on desorption lineshapes (from King, 1977). Desorption I is unaffected by the precursor state, whereas desorption 4 is most affected.

The lineshape has been shown in the equations above to be potentially coverage dependent and this is usually due to lateral interactions in the adlaycr which result in attractions or repulsions (increased, or decreased adsorption heat) between the species on the surface. Detailed descriptions of the effects of lateral interactions on desorption have been given elsewhere (King, 1978 Goltze et al., 1981 De Jong and Niemantsverdriet, 1990 Zhdanov, 1991a, b),... 

The mesostructure of the SBA-15 prepared at 80 °C was heavily disturbed after the application of the DP method, as observed using X-ray diffraction and Na adsorption-desorption measurements (data not shown). Here we only report characterization results related to the SBA-15 synthesized at 100 °C, as a lower synthesis temperature yield materials with poor hydrothermal stability [10]. Also for this material is there a significant impact on the SBA-15 textural properties by the impregnation methods. This is evident from Na adsorption-desorption measurements and X-ray diffraction as shown in Fig. 1. Physico-chemical properties derived from Na adsorption-desorption and XRD are listed in Table 1. Specifically upon inclusion of R, the surface area of SBA-15 is reduced by 20% and 70% for the Pt/SBA-15,WI and Pt/SBA-15,DP samples, respectively. However, as can be seen from the XRD data, inclusion of R by either method does not interfere with the structural ordering of the mesoporous material, as there are no significant alterations of the difftaction lineshape of the functionalized materials as compared to the parent SBA-15. Clearly, the structure of the parent SBA-15 is less affected by the WI method as compared to the influence of the DP method. 

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