Acids, adsorption

Methanol, Formaldehyde, and Formic Acid Adsorption/Oxidation on a Carbon-Supported Pt Nanoparticle Fuel Cell Catalyst A Comparative Quantitative OEMS Study... 

Consider the extraction of energy from the tail gases from a nitric acid adsorption tower, such as that described in Chapter 4, Example 4.4. 

Li, W.K., Gong, X.Q., Lu, G., and Selloni, A. (2008) Different reactivities of Ti02 polymorphs comparative DFT calculations of water and formic acid adsorption at anatase and brookite Ti02 surfaces. Journal of Physical Chemistry C, 112 (17), 6594-6596. 

The acidic character of 5A zeolite as a function of the calcium content has been explored by different techniques propylene adsorption experiments, ammonia thermodesorption followed by microgravimetry and FTIR spectroscopy. Propylene is chemisorbed and slowly transformed in carbonaceous compounds (coke) which remain trapped inside the zeolite pores. The coke quantities increase with the Ca2+ content. Olefin transformation results from an oligomerization catalytic process involving acidic adsorption sites. Ammonia thermodesorption studies as well as FTIR experiments have revealed the presence of acidic sites able to protonate NH3 molecules. This site number is also correlated to the Ca2+ ion content. As it has been observed for FAU zeolite exchanged with di- or trivalent metal cations, these sites are probably CaOH+ species whose vas(OH) mode have a spectral signature around 3567 cm"1. 

Uranium coprecipitated with aluminium phosphate, precipitate dissolved in nitric acid Adsorption onto colloidal ferric hydroxide... 

Amino acids Adsorption on ferric oxide Io exchange chromatography (IEC) 3 ig/l [511,512]... 

Humic acids Adsorption on macroretic-ular resin XAD-2 — — [448-450]... 

Adsorption of acetic acid on Pt(lll) surface was studied the surface concentration data were correlated with voltammetric profiles of the Pt(lll) electrode in perchloric acid electrolyte containing 0.5 mM of CHoCOOH. It is concluded that acetic acid adsorption is associative and occurs without a significant charge transfer across the interface. Instead, the recorded currents are due to adsorption/desorption processes of hydrogen, processes which are much better resolved on Pt(lll) than on polycrystalline platinum. A classification of adsorption processes on catalytic electrodes and atmospheric methods of preparation of single crystal electrodes are discussed. 

As shown in Figure 4, the increase in adsorption of acetic acid on Pt(lll) occurs in the potential range of 0.15 to 0.3 V, which roughly coincides with position of the current-potential peak of the voltammogram recorded in the same solution. An interdependence can thus be sought between acetic acid adsorption... 

In reviews on formic acid decomposition, Mars and coworkers194,198 wrote that the formation and decomposition of formate anions were monitored by infrared spectroscopy. These studies were carried out by Fahrenfort, Sachtler, and coworkers188,193 for the case of formates on metals produced by formic acid adsorption—Cu, Ni, Pd, Rh, Pt, and Zn and in the case of metal oxides, Hirota et al. investigated ZnO,187,189,190,197 while Scholten et al. studied MgO.199,200 The infrared... 

Madix and coworkers—facile formate formation/decomposition over Cu (110). In 1979-1981, Madix and coworkers219 220 226 studied formic acid adsorption and decomposition over Cu(l 10) and they showed facile formate production. TPD studies indicated that formate decomposed to yield C02 and H2 at temperatures as... 

Bowker et al.301 published spectroscopic and kinetic studies of formic acid adsorption on Cu(110). They observed that, at —73 °C, the sticking coefficient is high (0.9) but becomes low at 27 °C (0.1). The adsorption state switches from monodentate (—73 °C) to bidentate at 27 °C. 

Avena, M. J. and Koopal, L. K. (1999). Kinetics of humic acid adsorption at solid-water interfaces, Environ. Sci. Technol., 33, 2739-2744. 

The situation is quite different in the case of an acetic acid-water system. The energy of acetic acid adsorption on platinum is low and therefore the voltammetric curves taken in the absence and in the presence of acetic acid in the supporting electrolyte are nearly the same. However, radiometric data show that C-labeled acetic acid is adsorbed on the electrode surface. Most likely the acetic acid molecules are adsorbed on the top of the water molecules populating the electrode surface. Simultaneously recorded voltammetric and counting rate data are shown in Fig. 8. 

As Smith (300) has shown by infrared spectroscopy, carboxylic acids are adsorbed either by hydrogen bonding of the carboxyl group or by proton transfer to the surface. Carboxylate absorptions were observed in the spectra. Very likely O " or OH ions acted as proton acceptors although no OH absorption bands could be detected after carboxylic acid adsorption. The isoelectric point of pure anatase is near pH 6.6 (305). 

Interest in studying formic acid adsorption on metals by XPS and UPS was stimulated largely by its use as a probe molecule for investigating the role of the electronic factor in heterogeneous catalysis as in the work of Schwab (70), Dowden and Reynolds (71), Eley and Leutic (72), and Fahren-fort et al. (73). The advantages of XPS and UPS are fourfold. 

Temperature programmed desorption studies of formic acid decomposition by metals was reviewed recently by Madix (7d) the significance of formate formation is paramount to the discussion. This is also apparent in the recent electron energy loss spectra of formic acid adsorption on Cu(lOO) reported by Sexton (77). 

Meyer, M.L. and Bloom, P.R. Boric and silicic acid adsorption and desorption by a humic acid, 7 Thrirorr. Qual., 26(l) 63-69, 1997. 

Typical procedure used was to take 1.0 g of alumina (as an example) powder and add 10 mL of solution of detergent with varying concentration. The mixture was shaken, and the concentration of detergent was estimated by a suitable method. It was found that equilibrium was obtained after 2-4 h. The detergent such as dodecylammonium chloride was found to adsorb 0.433 mM/g of alumina with a surface area of 55 m2/g. The surface area of alumina, as determined from stearic acid adsorption (and using the area/molecule of 21 A2 from monolayer), gave this value of 55 m2/g. These data can be analyzed in more detail ... 

Gelissen, I. C., and M. A. Eastwood. Taurocholic acid adsorption during non-starch polysaccharide fermentation an in vitro study. Brit J Nutr 1995 74(2) 221-228. 

Waszczuk etal. [173] have performed radiometric and voltammetric studies of benzoic acid adsorption on a pc-Ag electrode in contact with 0.1 M HCIO4 solution. The electrodes were obtained by electroplating Ag black onto a vacuum-deposited silver substrate. Benzoic acid appeared to be surface active in the entire range of potentials available at Ag in aqueous solutions. Adsorption of benzoic acid increased as the potential became more positive and this surface process was... 

Fig. 11. Typical dissolution curve of stearic acid adsorption on the surface of a CaC03 filler r=1.8 pm...

Coal liquefaction Fischer-Tropsch synthesis Synthesis of methanol Hydrogenation of oils Alkylation of methanol and benzene Polymerization of olefins Hydrogenation of coal oils, heavy oil fractions, and unsaturated fatty acids Adsorption of S02 in an aqueous slurry of magnesium oxide and calcium carbonate S02 or removal from tail gas Wet oxidation of waste sludge Catalytic desulfurization of petroleum fractions Wastewater treatment... 

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