Potassium desorption, effect

The UPS spectra of Fig. 3.20 indicate that heating of CO on clean Fe(l 10) to 390 K leads mainly to desorption only a fraction of the CO dissociates. Substantially less CO desorbs from the potassium-promoted surface, however, and, after heating to 500 K, all CO on the surface has dissociated. Thus, potassium enhances CO bonding to the surface and promotes its dissociation. We discuss promoter effects in more detail in Chapter 9 and in the Appendix. 

Despite these widespread applicahons, ILM is not equally well suited for all classes of analytes. Due to the need for increased laser energies/fluences for the ionizahon/desorption process, ILMs may only be of restricted suitability for some classes of analytes. For example for proteins, an extensive peak broadening caused potenhally by the combination of extended neutral losses (e.g., of ammonia or water) and alkali-ion-adduct formation can be observed. On the other hand, the increased tendency of the ILM to favor sodium and potassium adduct formation makes it ideally suited for the measurement of carbohydrates [38,40], whereas in proteomics, this tendency of adduct formahon is again an unwanted effect. 

The experimencal results of COj adsorption on K-covered Ag(lll) will be reported in this chapter. The work is an extension of an earlier work in this laboratory and resolves several issues raised in that work. More TPD experiments have been performed to investigate coadsorption of water and COj, coadsorpcion of CO and COj, CO2 adsorption and desorption as a function of potassium coverage, and effects of residual contamination in UHV on COj adsorption. Some XPS and HREELS data were obtained in the previous work, but no systematic analysis and discussion of the data was perfoimied until now. Moreover, previous and new TPD spectra are analyzed more quantitatively. Based on the present study, a model of COj adsorption on Ag(lll) will be suggested. 

The roles of alkali, alkali earth and rare earth metal oxides seem different from the structural promoters. These oxides are able to increase the specific activity per unit surface area, while decrease the heat-resisting and anti-toxic ability. Thus, they are called as electronic promoters. Because the diameter of K+ ions is quite large, it is not possibly for K to enter into the lattice of magnetite. After reduction, K2O diffuses to the surface of crystallite. The surface potassium is able to accumulate with various forms during reduction and operations, to accelerate the recrystallization effect, but due to the electron, negative alkali metals decrease the effusion work of iron atoms, and accelerate the adsorption of dinitrogen or desorption of ammonia and finally are able to increase the specific activity per unit surface area. 

The Catacarb process, which was disclosed by Eickmeyer (1962), is licensed by Eickmey-er and Associates of Prairie Village, Kansas. For most applications the Catacarb process utilizes a catalyzed hot potassium carbonate solution however, potassium borate solutions are used for the removal of hydrogen sulfide in the absence of carbon dioxide (Gangriwala and Chao, 1985). The solutions contain undisclosed additives that catalyze absorption and desorption of acid gases, particularly carbon dioxide. The additives, which include a corrosion inhibitor, are claimed to have no effect on reformer or methanation catalysts that the purified gas may pass through downstream of the Catacarb absorber (Morse, 1968). 

Arsenite Solutions. Addition of essentially stoichiometric proportions of arsenic trioxide to aqueous sodiiun or potassium carbonate solutions results in a marked increase in the rate of absorption and desorption of carbon dioxide, as compared with conventional carbonate solutions. Figure 5-31 illustrates this phenomenon by comparing, qualitatively, the rate of absorption of carbon dioxide at 1 atm partial pressure and room temperature in 40% potassium carbonate and in a typical solution used in the Giarrunarco-Vetrocoke process (Riesen-feld and Mullowney, 1959). The effects of the more rapid absorption and desorption are appreciable savings in regeneration heat, reduction in equipment size, and production of treated gas of higher purity than is possible with ordinary hot carbonate solutions. 

Laser desorption FTMS. Analysis of amine-terminated EO/PO copolymers with molecular weight in the 600-2000 range effectively gives the complete homolog distribution, including the number of moles of EO and PO in each homolog. Both [M + H] and [M + K] ions are seen, presumably because potassium salts often remain in the product as neutralized alkoxylation catalyst (104). 

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