Chemisorption carbon monoxide

All of these results are consistent with the notion that surface migration of titanium oxide species Is an Important factor that contributes to the suppression of carbon monoxide chemisorption. The H2 chemisorption experiments on 1-2 ML of Ft, where no migration Is observed, strongly Indicate that electronic (bonding) Interactions are also occurring. Thus, for the tltanla system, both electronic Interactions and surface site blocking due to titanium oxide species must be considered In Interpreting SMSI effects. 

Carbon monoxide chemisorption was used to estimate the surface area of metallic iron after reduction. The quantity of CO chemisorbed was determined [6J by taking the difference between the volumes adsorbed in two isotherms at 195 K where there had been an intervening evacuation for at least 30 min to remove the physical adsorption. Whilst aware of its arbitrariness, we have followed earlier workers [6,10,11] in assuming a stoichiometry of Fe CO = 2.1 to estimate and compare the surface areas of metallic iron in our catalysts. As a second index for this comparison we used reactive N2O adsorption, N20(g) N2(g) + O(ads), the method widely applied for supported copper [12]. However, in view of the greater reactivity of iron, measurements were made at ambient temperature and p = 20 Torr, using a static system. 

The effects of tin/palladium ratio, temperatnre, pressnre, and recycling were studied and correlated with catalyst characterization. The catalysts were characterized by chemisorption titrations, in situ X-Ray Diffraction (XRD), and Electron Spectroscopy for Chemical Analysis (ESCA). Chemisorption studies with hydrogen sulfide show lack of adsorption at higher Sn/Pd ratios. Carbon monoxide chemisorption indicates an increase in adsorption with increasing palladium concentration. One form of palladium is transformed to a new phase at 140°C by measurement of in situ variable temperature XRD. ESCA studies of the catalysts show that the presence of tin concentration increases the surface palladium concentration. ESCA data also indicates that recycled catalysts show no palladium sulfide formation at the surface but palladium cyanide is present. 

Dynamics of High-Temperature Carbon Monoxide Chemisorption on Platinum-Alumina by Fast-Response IR Spectroscopy... 

Throughout these studies, no product other than propane was observed. However, subsequent studies by Sinfelt et al. [249—251] using silica-supported Group VIII metals (Co, Ni, Cu, Ru, Os, Rh, Ir, Pd and Pt) have shown that, in addition to hydrogenation, hydrocracking to ethane and methane occurs with cobalt, nickel, ruthenium and osmium, but not with the other metals studied. From the metal surface areas determined by hydrogen and carbon monoxide chemisorption, the specific activities of... 

Chemisorption of Carbon Monoxide. Chemisorption of carbon monoxide on NiO(250) does not change the electrical conductivity of the sample. The same result was obtained for NiO(200) (23). The curve of differential heats of adsorption of carbon monoxide on NiO(250) presents many similarities with the curve recorded in the case of NiO(200) (20). However, a few differences are noted. The heat of adsorption of the first dose (0.08 cc. per gram) of carbon monoxide on NiO(200) is high (42 kcal. per mole) (Table II). The adsorption of the next dose on the same oxide releases only 29 kcal. per mole. The initial high value of the heat adsorption was explained by the interaction of CO with excess surface oxygen (Table I), giving C02(ainitial heat of adsorption amounts to 29 kcal. per mole (Table II). It seems, therefore, that the surface excess oxygen... 

The high degree of dispersion of platinum on alumina has also been confirmed by the hydrogen chemisorption measurements of Keavney and Adler (Kl), and by the chemisorption studies of Gruber (G2). In addition, high dispersion of platinum on silica-alumina has been observed by Hughes and associates, using a carbon monoxide chemisorption technique (H10). 

Clearly, this sequence does not provide a unique identification of the surface site(s) that is associated with the increased catalytic activity. Carbon monoxide chemisorption provides the additional information required for this determination. Based on well-established steric considerations (124), the surface sites can also be arranged in an order of decreasing CO chemisorption ability (165) ... 

Surface pretreatment also has a marked effect on CO adsorption oxygen and carbon both inhibit carbon monoxide chemisorption and weaken the metal-adsorbate bond strength. Co-adsorbed hydrogen has no observable effects. 

The Rh(lll) surface was covered with carbon by decomposing 5 x 10 7 torr of either acetylene or ethylene at 1100 K for 10 minutes and subsequent flashing to 1200 K (230. Pre-adsorbed carbon had a very strong inhibiting effect on carbon monoxide chemisorption. This is the same effect it had on the methanation rate (36). The low inelastic scattering intensity indicated relatively small CO coverages while the broad elastic peak and... 

Carbon monoxide chemisorption on Ni 7 9 11 represents an interesting case with which to check these concepts since comparable studies have been performed on Ni 001 and Ni lll and since a number of other experimental methods have been applied to this system. Electron energy loss spectroscopic (EELS) studies performed at 150 K suggest that the initial adsorption occurs in threefold and twofold bridge sites along the step edge. Beyond this point, the CO molecules begin to occupy terrace sites. (12)... 

Two studies have been reported on the use of carbon monoxide chemisorption at higher than normal pressures and ambient or higher temperatures 64,71 one71 covered an astronomic pressure range (x 1013) from UHV to 2 bar. Application of surface X-ray diffraction71 or STM64 showed lattice expansion and substantial reorganisation of the surface. 

Fig. 12. Carbon monoxide chemisorption isotherms at 25°C on the binary Cu/ZnO catalysts. The labels at the individual isotherms denote the molar composition Cu/ZnO (43).

Carbon monoxide chemisorption on copper metal is weak and for the most part reversible, and has been studied by a number of techniques... 

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