Temperature-programmed desorption methanol

Specific surface areas of the catalysts used were determined by nitrogen adsorption (77.4 K) employing BET method via Sorptomatic 1900 (Carlo-Erba). X-ray difiraction (XRD) patterns of powdered catalysts were carried out on a Siemens D500 (0 / 20) dififactometer with Cu K monochromatic radiation. For the temperature-programmed desorption (TPD) experiments the catalyst (0.3 g) was pre-treated at diflferent temperatures (100-700 °C) under helium flow (5-20 Nml min ) in a micro-catalytic tubular reactor for 3 hours. The treated sample was exposed to methanol vapor (0.01-0.10 kPa) for 2 hours at 260 °C. The system was cooled at room temperature under helium for 30 minutes and then heated at the rate of 4 °C min . Effluents were continuously analyzed using a quadruple mass spectrometer (type QMG420, Balzers AG). 

Choisnet, J Abadzhieva, N Stefanov, P Klissurski, D Bassat, JM Rives, V Minehev, L. X-ray photoeleetron spectroscopy, temperature-programmed desorption and temperature-programmed reduction study of LaNiOs and La2Ni04+s catalysts for methanol oxidation. J. Chem. Soc., Faraday Transactions, 1994, Volume 90, 1987-1991. 

Figure 8. Temperature Programmed Desorption of methanol from the ferric molybdate (dashed line) and the manganese pyrophosphate (solid line) catalysts determined gravimetrically.

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... 

Scheme 4. Temperature programmed desorption/reaction of methanol on HZSM-5 [65].

Poulston, S., Rowbotham, E., Stone, P., Parlett, P. and Bowker, M. (1998) Temperature-programmed desorption studies of methanol and formic add decomposition on copper oxide surfaces. Catal. Lett., 52, 63-67. 

Further infonnatioii on the catalytic properties of stoichiometric and nonstoichiometric CaHAp may be obtained from studies on the adsorption and dehydrogenation of methanol. WiA stoichiometric CaHAp methanol decomposes at 600°C to produce predominantly carbon monoxide (Table 1) whose selectivity diminishes as the Ca/P ratio decreases while those to formaldehyde and dimethyl ether increase. Infrared spectra show that methoxy groups are formed on the surface of both the stoichiometric and nonstoichiometric catalysts. The results from temperature-programmed desorption experiments together with those from infrared spectroscopy suggest that the acidic sites found on the nonstoichiometric CaHAp catalyze the dissociative adsorption whereas the basic sites on the stoichiometric analogue catalyze the C-H bond scission and formation of CO and H. ... 

On metals to the right hand side of the transition series the alkoxides are reasonably stable. They decompose in a partial oxidative fashion on IB metals to produce formaldehyde and an example of temperature programmed desorption from methanol adsorbed on copper with predosed oxygen is... 

INITIAL STEPS IN METHANOL CONVERSION AND AN ALTERNATIVE HOMOLOGATION MECHANISM A small amount of methane (ca. 1C%) is formed in methanol conversion, and appears to be one of the first products formed (ref. 11). When a small amount of methanol is sorbed onto ZSM-5 zeolite, the lattice is methylated (ref. 5). Subsequent temperature-programmed desorption gives dimethyl ether and desorbed methanol first, then (at 250-300°C) methane (stable) and formaldehyde (unstable), and finally aromatic products (ref. 22-23). 

Crystalline borosilicate molecular sieves have been the object of an intensive investigation effort since they were reported in the open literature at the Fifth International Conference on Zeolites by Taramasso, et al. (1) A wide range of structures containing framework boron have been synthesized. The physical properties of these borosilicate molecular sieves have been studied by such techniques as X-ray diffraction, infrared and nuclear magnetic resonance spectroscopies, and temperature programmed desorption of ammonia. In addition, the catalytic performance of borosilicate molecular sieves has been reported for such reactions as xylene isomerization, benzene alkylation, butane dehydroisomerization, and methanol conversion. This paper will review currently available information about the synthesis, characterization, and catalytic performance of borosilicate molecular sieves. 

The temperature-programmed desorption of H2 turned out to be a new tool for the determination of Cu metal surface areas [6]. For industrial purposes, the interaction of hydrogen with copper surfaces is a significant elementary step in methanol synthesis. Moreover, adsorp-tion/desorption kinetics on copper single crystal surfaces is an interesting topic in surface physics... 

Low energy (55 eV) electron irradiation of multilayers of methanol on silver has been used in conjunction with temperature-programmed desorption of the products as a method to identify radiolysis products. In this case several products such as methoxymethanol were identified . The primary photochemical process in the methanol system is thought to involve the fission of a C—H bond forming a heteroatom stabilized cation such as 6. In addition to methoxymethanol glycolaldehyde (5) or methyl formate are also detected. Apparently the methanol system is unreactive to UV irradiation either at 240 nm or at 355 nm . 

Larsen G, Raghavan S, Marquez M, Lotero E Tungsta supported on zirconia and alumina catalysts temperature programmed desorption/reaction of methanol and pyridine drifts studies. 

Acidity and cataljdic properties of MeAPO-5 (Me = Mn, Co, Ni, Mg, Zn, Zr) have been studied by TPD (temperature-programmed desorption) of ammonia, by FTIR spectroscopy and by the catal3d ic effectiveness in the conversion of methanol (308). NiAPO-5 exhibits the best catalytic results in the formation of lower olefins. This is explained by the presence of sufficiently high density of Br0nsted sites of moderate strength and of comparatively small portions of strong acid Lewis sites. The acid sites are formed by the substitution of aluminum by Ni(II) ions. 

Farneth, W, Ohuchi, R, Staley, R., et al. (1985). Mechanism of Partial Oxidation of Methanol over Molybdenum(VI) Oxide as Studied by Temperature-programmed Desorption, J. Phys. Chem., 89, pp. 2493-2497. 

Methanol oxidation was investigated recently by IRAS (Infrared Reflection Absorption Spectroscopy) and TPD (Temperature Programmed Desorption)... 

Diagne, C., Idiiss, H., Pepin, I., Hindermann, J.P., and Kiennemann, A. Temperature-programmed desorption studies on Pd/Ce02 after methanol and formic acid adsorption and carbon monoxide-hydrogen reaction. Appl. Catal 1989, 50, 43-53. 

Ceckiewicz, in Fourier transform infrared spectroscopy (FTIR) studies of methanol sorption on zeolite at 25 50°C, observed the propylene band pattern but failed to detect ethylene [96]. Upon temperature-programmed desorption, however, C -C olefins were identified. In the suggested MTO scheme (Fig. 16), the propylene was nominated as a primary product (ie, obtained directly from MeOH or DME), and the formation of the other products occurs via two parallel routes. 

Novakova J, Kubelkova L, Habersberger K, Dolejsek Z. Catalytic activity of dealuminated-Y and H-ZSM-5 zeohtes measured by the temperature-programmed desorption of small amounts of preadsorbed methanol and by the low-pressure low reaction of methanol. J Chem Soc, Faraday Trans I 1984 80 1457. 

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