Dehydrogenation methanol

S. Neophytides, and C.G. Vayenas, Non-Faradaic Electrochemical Modification of Catalytic Activity 2. The case of Methanol Dehydrogenation and Decomposition on Ag, J. Catal. 118, 147-163 (1989). 

Methane oxidation and partial oxidation, electrochemical promotion of, 308 dimerization, 470 reforming, 410 Methanol dehydrogenation electrochemical promotion of, 403 selectivity modification, 404 Methanol oxidation electrochemical promotion of 398 selectivity modification, 400 Microscopy... 

Pal B, Torimoto T, Iwasaki K, Shibayama T, Takahashi H, Ohtani B (2004) Size and structure-dependent photocatalytic activity of jingle-beU-shaped silica-coated cadmium sulfide nanoparticles for methanol dehydrogenation. J Phys Chem B 108 18670-18674... 

Maurer, R., Claivaz, C., Eichtner, M., Schubert, K., Renken, A., A micro-structured reactor system for the methanol dehydrogenation to water-free formaldehyde, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 100-105 (5-9 March 2000), AIChE Topical Conf Proc., Atlanta, USA. 

Elementary Reaction Thermodynamics at the Aqueous, Electrified Interface Methanol Dehydrogenation... 

The presence of solution at a metal surface, as has been discussed, can significantly influence the pathways and energetics of a variety of catalytic reactions, especially electrocatalytic reactions that have the additional complexity of electrode potential. We describe here how the presence of a solution and an electrochemical potential influence the reaction pathways and the reaction mechanism for methanol dehydrogenation over ideal single-crystal surfaces. 

Figure 4.12 The upper plots (a, c, e, g) show the free energies (calculated by (4.4) from DFT) versus the estimated potential for reactants and products involved in the first, second, third, and fourth consecutive methanol dehydrogenation steps, as indicated, over Pt(lll) from Cao et al. [2005]. Filled symbols in (a) refer to the energy and potential for the system tq = Q. The lower plots (b, d, f, h) show the corresponding reaction energies for the first, second, third, and fourth consecutive methanol dehydrogenation steps, as indicated.

The elementary reaction energies and thermodynamics for methanol dehydrogenation have been shown to be significantly influenced by electrode potential. The oxidation pathways become much more favorable at higher potentials. The relative barriers of O—H to C—H bond activation decrease with increasing potential, which decreases the overall selectivity to CO and CO2 and increases the yield of formaldehyde. This is consistent with experimental studies. The oxidation of CO intermediates appears to occur via adsorbed hydroxyl intermediates. The hydroxyl intermediates are more weakly held to the surface than atomic oxygen, and thus have significantly lower barriers for the oxidation of CO. 

These trends agree well with recent theoretical studies, which found that several neighboring (three) Pt atoms are required for methanol dehydrogenation [Desai et al., 2002 Greeley and Mavrikakis, 2002, 2004 Okamoto et al., 2003 Cao et al., 2005], while these requirements are less stringent for formaldehyde dehydrogenation [Desai et al., 2002 Greeley and Mavrikakis, 2002]. 

Methanol dehydrogenation to ethylene and propylene. In some remote ioca-tions, transportation costs become very important. Moving ethane is almost out of the question. Hauling propane for feed or ethylene itself in pressurized or supercooled vessels is expensive. Moving naphtha or gas oil as feed requires that an expensive olefins plant with unwanted by-products be built. So what s a company to do if they need an olefins-based industry at a remote site One solution that has been commercialized is the dehydrogenation of methanol to ethylene and propylene. While it may seem like paddling upstream, the transportation costs to get the feeds to the remote sites plus the capital costs of the plant make the economics of ethylene and its derivatives okay. 

Dehydrogenation of methanol, dehydrogenation of propane, metathesis of ethylene and butylene, and cat crackers. (Other crackers in refineries produce olefins too.)... 

The results presented here indicate that a new methanol dehydrogenation reaction path is opened when the Mo(l 12) surface is modified by a p(lx2) oxygen layer. The result of the CO adsorption experiment suggests that main electronic effect of oxygen modifier is restricted to the metal atoms directly bonded with the oxygen atoms. TTiis leads to a concept of the selective blocking of the surface atoms to create new active structures, which can provide a powerful mean to control catalytic reaction paths. 

The metallic Cu clusters on Mo02 (denoted Cu/Mo-CTAB) were completely inactive for CO PROX at 90 °C (Table 2.2). Metallic Cu clusters on ZnO (Cu/Zn-CTAB) and Si02 (Cu/Si-CTAB) were active for the methanol dehydrogenation but they were inactive for the PROX reaction. Similarly prepared Cu/Zr-CTAB, Cu/Fe-CTAB and Cu/Al-CTAB catalysts were also inactive for the PROX reaction. In contrast, the new Cu/Ce-CTAB catalyst exhibited tremendous activity with the feed C0/02/H2/He = 1 1 50 48 (mol.%) (Table 2.2), whereas the activities of conventional impregnated Cu/Ce02 and Cu/Ce203 catalysts and co-precipitated Cu-Ce catalysts were much lower. 

Observation of the CHX and COads species as a result of the interaction between methanol and a palladium surface indicates that the methanol decomposition occurs via two routes (1) scission of the C-O bond in methanol with the formation of CHX species (x = 0-3), and (2) methanol dehydrogenation giving COads- The contribution of CO bond scission with the formation of carbonaceous species is negligible under UHV conditions, especially at low exposures, but it increases strongly at higher pressures. These XPS results indicate unambiguously that the pathway of methanol C-O bond scission can take place on the atomically smooth surface of palladium, but that high methanol partial pressures are necessary to form a noticeable amount of carbon species produced by the methanol C-O bond scission. 

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