MethA

Metha.nol-to-Ga.soline, The most significant development in synthetic fuels technology since the discovery of the Fischer-Tropsch process is the Mobil methanol-to-gasoline (MTG) process (47—49). Methanol is efftcientiy transformed into C2—C q hydrocarbons in a reaction catalyzed by the synthetic zeoHte ZSM-5 (50—52). The MTG reaction path is presented in Figure 5 (47). The reaction sequence can be summarized as... 

Metha.no Ca.rbonyla.tion, An important industrial process cataly2ed by rhodium complexes in solution is methanol carbonylation to give acetic acid. 

Bj Preparation of 11 ji-Methoxy-A ° -Estratriene-3-ol-17-one 12.3 g of 11/3-methoxy-A -estradiene-3,17-dione were dissolved in 1,230 cc of methanol and then, under an atmosphere of nitrogen, 7.38 g of palladium hydroxide were added and the mixture was held at reflux for one hour under agitation and a nitrogen atmosphere. Then the reaction mixture was cooled to 30°C, filtered, vacuum filtered and washed with methanol. The metha-nolic solutions were concentrated to about 50 cc, allowed to stand overnight at room temperature and filtered. The precipitate formed was triturated in methanol and dried at 80°C to obtain 10.74 g (yield = 87.5%) of 11/3-methoxy-A " -estratriene-3-ol-17-one having a MP of 264°C. 

Styrene monomer was also copolymerized with a series of functional monomers by using a single-step dispersion copolymerization procedure carried out in ethanol as the dispersion medium by using azobisizobu-tyronitrile and polyvinylpyrollidone as the initiator and the stabilizer, respectively [84]. The comonomers were methyl methacrylate, hydroxyethyl acrylate, metha-crylic acid, acrylamide, allyltrietoxyl silane, vinyl poly-dimethylsiloxane, vinylsilacrown, and dimethylamino-... 

The chapter by White et al. proposes a different approach to metha-nator temperature control. Here the temperature rise is controlled by limiting the amount of reaction in each stage, and that is done by introducing steam (a product of the reaction). High initial temperatures are followed by successively lower temperatures entering each reactor in series. This is a second-generation methanation approach which may follow closely on the first-generation approaches typified by the previous three papers. 

Hydrogen chloride is a permanent irreversible poison to the metha-nation activity of C150-1-03 even though most of it is not picked up by the catalyst but is observed in the effluent gas. Only 0.02-0.04% was found on the discharged catalyst, but any amount of chloride in the feed gas is detrimental to catalyst activity. 

The poisons most likely to be encountered in an ammonia plant are those originating in the C02-removal system which precedes the metha-nator. Carry-over of a small amount of liquid into the methanator, which is almost inevitable, is not normally serious. Plant malfunction, however, can sometimes result in large quantities of C02-removal liquor being pumped over the catalyst, and this can be very deleterious. Table I lists the effects of common C02-removal liquors on methanation catalyst activity. 

Operability. All four series of experiments prove that HGR metha-nation is a usable and operable system. With a total gas recycle ratio of about 10 1 and with CO concentrations in the mixed feed entering the catalyst bed as high as 4.3% (wet basis), temperature control was excellent and no hot spots developed. It appears likely that lower recycle... 

The higher reactivity of the Raney nickel coated plates is also illustrated by the plots of catalyst temperature vs. bed length (Figure 10). The maximum bed temperature (indicative of near-completion of metha-nation) was consistently reached within a shorter distance from the gas inlet, and the slopes of the curves are correspondingly steeper for the more reactive bed of parallel plates coated with Raney nickel. 

The catalyst in an isothermal tube-wall reactor (experiment TWR-6 in Ref. 2) deactivated much more slowly than did the catalyst in the best test (experiment HGR-14) in an adiabatic HGR reactor (0.009 vs. 0.0291 %/mscf/lb), and it also produced much more methane (177 vs. 32 mscf/lb catalyst). This indicates that adiabatic operation of a metha-nation catalyst between 300° and 400°C is not as efficient as isothermal operation at higher temperature ( 400°C). 

The SASOL plant was operated with a surplus of C02 during a long term test of 4000 hrs. Of the C02 in the synthesis gas, 33.4% was metha-nated while the remaining 66.6% left the reaction system unconverted. Product gas from final methanation yielded specification grade SNG containing residual hydrogen of 0.7 vol % and residual CO of less than 0.1 vol %. The heating value was 973 Btu/standard cubic foot (scf) after C02 removal to 0.5 vol % (calc.). 

These tests demonstrated that the Lurgi Rectisol process provides an extremely pure synthesis gas which can be charged directly to the metha-nation plant without problems of sulfur poisoning of the nickel catalyst. However, in order to cope with a sudden sulfur breakthrough from Rectisol as a result of maloperation, a commercial methanation plant should be operated with a ZnO emergency catchpot on line. 

Natrium-cyano-trihydrido-borat reduziert Enamine in Methanol oder Metha-nol/Tetrahydrofuran (1 4) beipH5 (15-30 Min., 20°) zu gesattigten Aminen. Die konju-gierten Carbonyl-Gruppen in vinylogen Carbonsaure-amiden setzen die Reaktionsge-schwindigkeit herab. 

Oxo-2,2,6,6-tetramethyl-/rans-hepten-(3) wird durch den Athylendiamin-Metha-nol-Komplex des zweiwertigen Chroms (24 Stdn., 25°) mit 81%iger Ausbeute zu 2-Oxo-2,2,6,6-tetramethyl-heptan5 reduziert. 

So erhalt man z. B. aus 6-Oxo-3,3-dimethyl-cyclohexen/Athylendiamin zu 47% d.Th. 4-Oxo-l,1 -dimethyl-cyclohexan [23 Stdn./25° mit Chrom(II)-acetat, Essigsaure, Metha-... 

Polyacrylamid2 3 4 DEAE-Cellulose3 7 Glutaraldehyd + Glycidyl-metha-... 

Lopez-Berestein, G., Metha, R., Hopfer, R. L., Mills, K., Kasi, L., Metha, K., Fainstein, V., Luna, M., Hersh, E. M., and Juliano, R. L. (1983). Treatment and prophylaxis of disseminated infection due to Candida albicans in mice with liposome-encapsulated amphotericin B, J. Infect. Pis.. 147, 939-945. 

Lopez-Berestein, G., Hopfer, R. L., Metha, R., Metha, K., Hersh,... 

Adriaens P (1994) Evidence for chlorine migration dnring oxidation of 2-chlorobiphenyl by a type 11 metha-notroph. Appl Environ Microbiol 60 1658-1662. 

Methyl coenzyme M reductase plays a key role in the production of methane in archaea. It catalyzes the reduction of methyl-coenzyme M with coenzyme B to produce methane and the heterodisulfide (Figure 3.35). The enzyme is an a2P2Y2 hexamer, embedded between two molecules of the nickel-porphinoid F jg and the reaction sequence has been delineated (Ermler et al. 1997). The heterodisulfide is reduced to the sulfides HS-CoB and HS-CoM by a reductase that has been characterized in Methanosarcina thermoph-ila, and involves low-potential hemes, [Fe4S4] clusters, and a membrane-bound metha-nophenazine that contains an isoprenoid chain linked by an ether bond to phenazine (Murakami et al. 2001). 

King GM (1984) Metabolism of trimethylamine, choline and glycine betaine by sulfate-reducing and metha-nogenic bacteria in marine sediments. Appl Environ Microbiol 48 719-725. 

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