Methanol, activation

Influence of Mo content. The reaction of CH4 with O2 on Mo03/Si02 catalysts under specific reaction conditions leads mainly to the formation of formaldehyde and carbon oxides, with minor amounts of dimerization products and methanol. Activity and selectivity data obtained for a given set of experimental parameters were practically the same when the experiment was duplicated. For all catalysts the increase in reaction temperature resulted, as expected, in an increase in the CH4 and O2 conversions but in a decrease of the selectivity towards selective oxidation products in favor of deeper oxidation (COx) and dimerization (C2) products. A similar... 

Figure 6.33. Trends in Pt surface-area normalized electrochemical activity of various ternary alloy compositions with respect to the electrooxidation of methanol. Activity gains are seen in the order Pt, PtRu, PtRuNi, and PtRuCo (adapted from [69]).

Passive types of leak detection such as observation wells and collection sumps where product is collected and analyzed directly should work effectively with methanol. Active leak detection systems that rely on thermal conductivity and electrical resistivity sensors will not work with methanol because its properties are so different from gasoline. Another type of active leak detection system that will work with methanol or any other type of fuel relies on changes in impedance in a sensor wire as it becomes wetted with the fuel [4.5]. These leak detection systems also have the advantage that they can pinpoint the location of the leak along the length of the sensor wire. 

Sponsored by the European Community, a Ct chemistry course was organized at Aachen by Prof. Keim. Dr Bchr and Dr Roper of the Technical University of Aachen, Prof, Teyssie and Prof. Hubert of the University of Liege and Prof. L go of the University of. Milan. The three-day course devoted to the application of predominantly liom( cneous transition metal based catalysis in C molecules formed the skeleton for this botrk. In nine chapters the following topics are covered the reduction of CO and reactions with CO. the chemistry of methanol, activation of carbon dioxide, hydrocyanation. methane chemistry and carbene chemistry. 

Hagemeier C, Krtier M, Thauer RK, Warkentin E, Ermler U. Insight into the mechanism of biological methanol activation based on the crystal structure of the methanol-cobalamin methyl-transferase complex. Proc. Natl. Acad. Sci. U.S.A. 2006 103 18017-18022. 

Catalyst Sarea (m Anl-cat) Scu 3> (m /lnnl t) Methanol activity (mg-MeOHAnl-cat-h) Spedfic activity (3) (mg-MeOHAn2-cat h)... 

Only 2% side products, in decreasing order methyl formate, methane and ethanol, appeared over the CsOH-doped catalyst despite the two-fold increase in activity, and no side products were observed over the KOH doped catalyst despite the 30% enhancement of the methanol activity compared to the undoped catalyst. When CO2 was added to the synthesis gas, the increase of methanol yield was smaller over the CsOH/Cu/ZnO catalyst(Table III)than over the undoped Cu/ZnO catalyst (10), resulting in a reversal of the order of activities to undoped Cu/ZnO>(greater than) Cu/ZnO/CsOH in the CO2/CO/H2 2/28/70 synthesis gas. 

Data are given here for methanol formation from CO + H2, but the simultaneous promotion of the WGS reaction in the additional presence of H2O has been documented in ref. 38. Further, the promotion of the Cu/ZnO catalysts for methanol is ion specific as Cs>Rb>K>Na,Li (ref. 39), in the same order as the basic strength of the counterion of the surface alkali cation such as OH-. The methanol activity dependence on the concentration of the alkali surface dopant shown in Figure 3 has been explained as follows. The catalyst is bifunctional and contains a basic component (e.g. CsOH) that enhances activation of CO by... 

Fig. 5. Correlation of specific methanol activity as a function of normalized cesium surface concentration of Cs/Cu/ZnO (a) and Cs/Cu/Zn0/Cr203 ( ) catalysts tested at 250°C and 75 atm with H2/CO = 2.33 synthesis gas at GHSV = 6120 (unsupported) and 10,000 (Cr203 supported) (STP)/kg catal/hr.

Figure 1. Specific methanol activity as a function of leaclji depth in pellets. Methanol yield determined at a space velocity of 36 000 h. (a) Catalysts (e)RCDl, (a)RC,(CATX) commercial catalyst. (b)Catalysts (m)RCZD, (e)RCD2, (e)RCZ. Raney catalyst preparation conditions described in Table 1.

FIGURE 177 LCB of polymers made with three Cr/alumina catalysts that were treated with phosphate and sulfate. Alumina (600 °C) was impregnated with Cr(OAc)3, H3P04, and H2S04 in methanol, activated at 650 °C, then tested at 95 °C with 5 ppm BEt3 or AlEt3. 

During extraction with acetone and chloroform (Giusti and Wrolstad, 1996a,b), it is advisable to prepurify the extract on acidic methanol-activated C18 minicolumns (Hong and Wrolstad, 1990) before analysis by HPLC. 

Fig. 11. Structural and activity data (arbitrary units) for synthesis gas activation of NdCu at 15 bar and 423 K showing the cor relation between the growth of methanol activity and coppcr/neodymium oxide peak intensities...

Fig. 12. Variation at maximum methanol activity (Rm) with R component for catalysts derived from Z R C o alloys (12bar, 513K also including data for Zr09Al0 Cu20 and ZrCu2) (Owen et al. 1990).

Datta and coworkers measured the sorption of methanol from vapor by Nafion all over the range of methanol activities at 25 °C [274] and 30 °C [275]. The uptake of ethanol and propanol from vapor by Nafion as a function of the alcohol activities were determined at 20 °C [272] and 30 °C [276]. Zhao et al. [281] reported uptake of methanol and ethanol by Nafion, at 40 and 60 °C, up to alcohol activities close to unity. 

Fig. 8.9 Up) Model of a (a) pure fcc(lll) surface (x = 0), Se-containing surface with (b) small (x = 0.25), (c) moderate (x = 0.50), (d) high (x = 0.75) content in Se, and a fcc(lll) surface covered with a monolayer of Se (x = 1) (Bottom) Change in free energy associated with the initial activation of methanol (UMO) plotted against the ORR activity (UORR). For structures lying on the upper left part of the plot methanol activation is thermodynamically unfavorable, with UMO > UORR. For structures lying on the lower right part such as Pt, methaonol readily dehydrogenates since UMO < UORR (Source [126] reproduced with permission of Elsevier)...

Transition metal surfaces enriched with S, Se and Te, have been considered as candidates for DAFC cathode catalysts [112-115], For example, ruthenium selenium (RuSe) is a weU-studied electro-catalyst for the ORR [116, 117]. The ORR catalysis on pure Ru surfaces depends on the formation of a Ru oxide-like phase [118]. Ru is also an active catalyst for methanol oxidation. On the other hand, the activity of the ORR on RuSe is found not be affected by methanol [116]. RuS, has also been reported insensitive to methanol [119-122], DPT studies of model transition metal surfaces have provided with atomistic insights into different classes of reactions relevant to fuel cells operation, such as the hydrogen evolution [123], the oxygen reduction [124], and the methanol oxidation [125] reaction. Tritsaris, et al. [126] recently used DPT calculatimis to study the ORR and methanol activation on selenium and sulfur-containing transition metal surfaces of Ru, Rh, Ir, Pd, Co and W (Fig. 8.9). With RuSe as a starting point, the authors studied the effect of the Se on... 

Tiitsaiis GA, Greeley J, Rossmeisl J, Norskov JK (2011) Trends in oxygen reduction and methanol activation on transition metal chalcogenides. Electrochim Acta 56 9783-9788... 

Park et al. compared methanol versus formic acid electrooxidation on polycrystalline Pt and on two sizes of carbon-supported Pt (2.0 nm vs. 8.8 nm) (Fig. 3.5) [44]. The potentials were referenced to a saturated calomel electrode (SCE) (RHE, 0.242 V) in 0.05 M H2SO4 at a scan rate of 50 mV s The cyclic voltammograms were normalized to a 1 cm Pt effective area. They observed a reduction in methanol activity for particles smaller that 4 nm and an opposite effect for formic acid see Fig. 3.5. The disparity between methanol and formic acid size-dependent performance trends is due to methanol preferentially adsorbing onto three adjacent Pt atoms found on Pt(lll)-faceted surfaces during the C-H bond dissociation step... 

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