Methanol adsorption study

Coutanceau C, Hahn F, Waszczuk P, Wieckowski A, Lamy C, Leger J-M. 2002. Radioactive labeling study and FTIR measurements of methanol adsorption and oxidation on fuel cell catalysts. Fuel Cells 2 153-158. 

Sobkowski J, Wieckowski A. 1972. A new approach to the radiometric study of methanol adsorption on platinum. J Electroanal Chem 34 185-189. 

Because of the importance of the surface chemistry of bone mineral in physiological systems, we have undertaken a series of gas adsorption studies on hydroxyapatite in the form of anorganic bone. In a recent publication from this laboratory (4) results of calorimetric studies of the adsorption of water and methanol vapors on bone mineral and on synthetic hydroxyapatite were reported. The adsorption potential for nitrogen on dehydrated hydroxyapatite, whether from bone or from synthetic sources, was rather profoundly altered by the addition to the surface of chemisorbed methanol or water prior to the adsorption of nitrogen at —195° C. This effect was reflected in the specific surface areas, in the BET C values, and in the resultant values of Ex — EL (net heats of adsorption) as shown in Table I of the above paper. 

The last two assumptions can be verified by studying the coverage as a function of the sweep rate used to "bum off the adsorbed molecules, and subsequently operating in a region where 0 is independent of sweep rate. In the example shown in Fig. 8J, a value of v = 5 V/s was found to be sufficient, but for the study of methanol adsorption, sweep rates as high as 800 V/s were necessary, because of the much higher bulk concentrations of adsorbate employed. 

Methanol adsorption at Mo03(010), (001), and (100) surfaces has been studied in cluster models using the semi-empirical ENHT method [230]. The calculations suggest that both molecular and dissociative adsorption may occur at the different surfaces. The stability of molecular adsorption complexes increases from the (100) surface to (001) and (010) if the latter contains oxygen... 

The TiO2(110) surface can be modified to alter the surface chemistry of adsorbed methoxides. Recently Vohs et al. [73] have reported temperature programmed desorption studies of methanol on TiO2(110)-supported V2O5. Deposited monolayer films of vanadia converted some of the adsorbed methanol to formaldehyde and water, while multilayer films of vanadia on the TiO2(110) surface were found to be inactive for methanol oxidation. Furthermore, adsorption studies of formaldehyde indicated that formaldehyde production from... 

Substrate adsorption studies as conducted with ZnS in aqueous solution were performed also with CdS, CdS--Si02 and SiOi in methanol, the solvent employed in... 

Shah and coworkers also studied methanol adsorption in sodalite and, in contrast to the case of chabazite, the HB complex with two hydrogen bonds between the methanol and the zeolite lattice was found to represent the mini-... 

R. Shah, J. D. Gale, and M. C. Payne, /. Phys. Chem., 100, 11688 (1996). Methanol Adsorption in Zeolites—A First-Principles Study. 

Haase et al. studied methanol adsorption at active sites of an acidic... 

Only for methanol adsorption in H-FER [19, 22] did the two DFT studies not lead to a consistent picture. Both simulations find a neutral adsorption complex of methanol in the 10-ring channel. In addition, Stich et al. [22] find a neutral adsorption structure for methanol in the 8-ring channel of FER. However in a dynamics run at 300 K proton transfer occurs and the average structure corresponds to the CH3OH2+ ion with two almost equal distances [22]. It is presently not dear... 

The electrochemical oxidation of methanol has been extensively studied on pc platinum [33,34] and platinum single crystal surfaces [35,36] in acid media at room temperature. Methanol electrooxidation occurs either as a direct six-electron pathway to carbon dioxide or by several adsorption steps, some of them leading to poisoning species prior to the formation of carbon dioxide as the final product. The most convincing evidence of carbon monoxide as a catalytic poison arises from in situ IR fast Fourier spectroscopy. An understanding of methanol adsorption and oxidation processes on modified platinum electrodes can lead to a deeper insight into the relation between the surface structure and reactivity in electrocatalysis. It is well known that the main impediment in the operation of a methanol fuel cell is the fast depolarization of the anode in the presence of traces of adsorbed carbon monoxide. 

A study of methanol adsorption on platinum under UHV conditions or at a gas/solid interface is also of interest. Not many papers dealing with methanol adsorption in a UHV chamber [135,136] are available. The adsorption takes place without a reaction on Pt( 111) at lo w temperatures (100 K), and based on thermal desorption experiments it was concluded that a monolayer of methanol adsorbate desorbs at 180 K. The heat of adsorption of molecular methanol was estimated to be 46 kJ mol-1 on unreconstructed Pt(l 11) [137]. Infrared spectroscopy has been applied for the study of methanol adsorption on Pt(l 11) [138], and it was shown that a 0.36 monolayer of methanol corresponds to the saturation of the desorption peak found at 180 K. The methanol multilayer coverages were also found, but had different infrared frequencies that were associated with the methyl and C-0 stretching modes (Scheme 11.1). 

This study shows that the first benzoate species formed are not active towards H2 and play the role of spectator. The others (species B) disappear under H2 flow and lead to benzaldehyde. The existence of two types of benzoate species can be related to the presence of two types of adsoiption site on Zr02, as already evidenced by methanol adsorption [9], The unreactive benzoate species seem to... 

Adsorption studies of methanol, water and ammonia, and binary mixtures of these compounds, have been used to explain the difference in the change in reaction behaviour of zeolites Rho and mordenite in the methanol amination reaction after hydrothermal treatment. It is found that the changes in the total adsorption capacities were related to the changing pore volumes and to the presence of extra-framework aluminium within the pores of the catalysts. The changes in the reaction performance of the catalysts for the methanol amination reaction were also correlated to the changes in acidity, structure and adsorption capacity of the catalysts. 

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