Oxygenate methanol

GP 4] [R 11] For methanol conversion over sputtered silver catalyst, no catalyst deactivation at high oxygen methanol ratios (e.g. over 0.2 1) was observed, different from findings in the literature with conventional catalysts and reactors (8.5 vol.-% methanol 10-90% oxygen balance helium 510 °C 10 ms slightly > 1 atm) [72]. 

In order to recognize the pattern of reactivity of alcohols on modified nickel surfaces, it is essential to know the reaction pathways exhibited by less reactive surfaces. Initially the dehydrogenation of CH3OH was studied on copper (4 ) and silver (5 ) single crystal surfaces. On Cu(110), following the preadsorption of submonolayer quantities of atomic oxygen, methanol reacted via the following sequence (4,6) ... 

Many substances can be partially oxidized by oxygen if selective catalysts are used. In such a way, oxygen can be introduced in hydrocarbons such as olefins and aromatics to synthesize aldehydes (e.g. acrolein and benzaldehyde) and acids (e.g. acrylic acid, phthalic acid anhydride). A selective oxidation can also result in a dehydrogenation (butene - butadiene) or a dealkylation (toluene -> benzene). Other molecules can also be selectively attacked by oxygen. Methanol is oxidized to formaldehyde and ammonia to nitrogen oxides. Olefins and aromatics can be oxidized with oxygen together with ammonia to nitriles (ammoxidation). 

Degussa AG Dimethyl terephthalate (DMT) p-Xylene, oxygen, methanol Liquid oxidation with homogeneous catalysis, mild-noncorrosive conditions 30 NA... 

Degussa AG Terephthalic acid p-Xylene, oxygen, methanol, water Hydrolysis of DMT, no organic solvent used, no corrosion problems 1 1984... 

ADH also oxygenates methanol into toxic formaldehyde. Consequently, ethanol should be administered in order to inhibit the breakdown of methanol in cases of methanol intoxication. 

In the literature there has been much debate regarding the role of the lattice or extralattice Ti in Ti silicalite for a variety of oxidation reactions. In order to have a more precise idea of the role of the lattice or surface Ti and more specifically of the role of the coordination sphere of Ti, a series of monopodal and tripodal titanium surface complexes (i. e., =SiOTi(OR)3 and ( SiOIsTiOR) were derived by the reaction of the Ti alkyl (Structure 1) and hydride species with water, oxygen, methanol, and tert-butanol. The resulting complexes were then used in the epoxidation of 1-octene by tert-butyl hydroperoxide. Tripodal complexes, especially (=SiO)3Ti( Bu), were found to be significantly more active and more selective for the epoxidation of 1-octene than their monopodal counterparts [22]. 

Figure 6 TDS (dashed) and TPRS (full) of oxygen/methanol on electrolytic silver. Heating rate 1.3 K/s...

Fig. 2. Simulated yields of oxygenates (methanol and formaldehyde) vs. oxygen conversion in different heat-transfer regimes. (1) Adiabatic, T0 = 723 K (2) isothermal, T = 723 K (3) isothermal, T = 803 K (4) isothermal, T = 893 K.

In spite of the above listed complications, there is distinct progress in the kinetic description of alkane (first of all methane) partial oxidation over metal catalysts in some particular cases. One bright example of this kind is represented by a recent publication by Mhadeshwar and Vlachos (2005) summarizing their achievements in the modeling of methane transformations and related reactions of oxygenates (methanol and formaldehyde) over a Rh surface. Among them ... 

Fuel cell Hydrogen-oxygen, methanol-oxygen... 

FIGURE 5. Relationship between log rate of quenching and ionization potentials of amines for quenching of singlet oxygen (methanol solution) [reprinted, with permission, from R. H. Young, R. L. Martin, D. Feriozi, D. Brewer, and R. Kayser, Photochem. Photobiol., JT, 233 (1973)1. 

Autothermal reforming of methanol, also known as Oxidative Methanol Reforming (OMR), is one such method. This process is distinguished from steam reforming of methanol by the co-feeding of oxygen to the reactor system. The stoichiometry of the reaction at an oxygen/methanol ratio of 0.25 is shown in Equation 1. 

For authothermal methanol reforming, an appropriate ratio between oxygen/ methanol and water/methanol needs to be controlled to achieve autothermal operation while avoiding carbon formation (Kamarudin, Baud, Som, Takriff, 2004). 

A methanol-oxygen pre-treatment of the copper-catalysts at high temperatures is necessaiy to obtain catalytic oscillations in the copper/oxygen/methanol-system. For the pre-treatment the sample can be either treated with methanol-ojQrgen mixtures or alternating with oxygen and methanol at temperatures above 730 K. In a methanol-oxygen-helium flow (methanol to ojq gen ratio around 2 1, T > 730 K) the... 

Methanol dehydrogenates to methyl formate over fresh WC and P-W2C powders with selectivities higher than 90% (109,110). The dominant side reaction is the decomposition to synthesis gas. Over WC and P-W2C modified with oxygen, methanol selectively dehydrates to dimethylether at 473 K and at higher reaction temperatures, C2-C4 olefins are produced (47). Thus, the dehydrodimerization of methanol apparently requires WC sites. These sites are titrated by chemisorbed oxygen. Thus, oxygen on the surface inhibits the formation of methyl formate and introduces a surface acid function WO that catalyzes dehydration by carbenium-ion type catalysis. 

Mechanistic Aspects. Plausible mechanistic schemes for the production of the oxygenates methanol, ethylene glycol, and polyalcohols from synthesis gas... 

In the Absence of Oxygen Methanol, Ethanol, 2-Propanol, and t-Butyl Alcohol Alcohols such as methanol, ethanol, and 2-propanol are converted with Pt/Ti02 to the corresponding dehydrogenation products such as formaldehyde, acetaldehyde, and acetone, respectively, with the formation of equimolar H2. t-Butyl alcohol is converted into 2,5-dimethyl-2,5-hexanediol with the formation of H2 through intermolecular dimerization since t-butyl alcohol has no alpha-hydrogen. In these oxidative reactions, alcohols are oxidized by photoformed holes, while photoexcited electrons reduce water (or H" ) to form H2 [4]. 

Direct partial oxidation of methane to Ci oxygenates (methanol and formaldehyde) could be a promising alternative for the use of abundant natural gas... 

Thermal batteries have lower maintenance requirements than the other battery systems, such as oxygen-methanol and hydrazine battery systems. 

One difference between the two modes of operation is the reaction temperature. The complete conversion mode operates at a slightly higher temperature (680720°C), whereas the incomplete conversion mode operates at 600650°C. The lower temperature of the latter mode, coupled with the lower oxygen-methanol ratio, reduces the extent of the undesirable overoxidation reactions [Eqs. (14) and (15)]. The complete conversion mode is used in the BASF process and has an overall yield of 89.590.5 mol%, whereas the incomplete conversion mode is used in the ICI, Bordena, and Degussa processes and has an overall yield of 9192 mol% [17]. 

---