Methane moderator

The critical temperature of methane is 191°K. At 25°C, therefore, the reduced temperature is 1.56. If the dividing line is taken at T/T = 1.8, methane should be considered condensable at temperatures below (about) 70°C and noncondensable at higher temperatures. However, in process design calculations, it is often inconvenient to switch from one method of normalization to the other. In this monograph, since we consider only equilibria at low or moderate pressures in the region 200-600°K, we elect to consider methane as a noncondensable component. 

Propargyl alcohol (332) and (328) react readily with isocyanates in the presence of a basic catalyst to give 4-methylene-2-oxazolidinones (334) and 4-methylene-2-imidazolinones (336), respectively (63JOC991). In the absence of sodium methoxide the intermediate methanes (333) and ureas (335) were obtained and on treatment with sodium methoxide underwent ring closure. Moderate to excellent yields were obtained. 

In summary, starting with 105°F gas at atmospheric pressure, the theoretical work necessary to liquify one pound of methane is 510.8 Btu or 352 hp/MMcfd. The simplified liquefaction process, as illustrated, uses a turboexpander/compressor and a small propane refrigeration unit. The 41.25% efficiency breaks down as follows one-fourth contributed by the turboexpander/compressor at 35.8% efficiency one-sixteenth contributed by the mechanical propane refrigeration unit at 43% efficiency, at a moderate temperature where its efficiency is high and a large fraction—eleven-sixteenths—contributed at 58.2% efficiency by compression and Joule-Thomson condensation energy. 

Radiolytic oxidation is important to the design and operation of reactors because it adversely affects key graphite properties and, by removing moderator material, may bring about the need for increased fuel enrichment. As mentioned earlier, an inhibitor (methane) is added to the coolant to reduce radiolytic oxidation to acceptable levels. However, access of the inhibitor to the inner portions of the moderator brick must be assured. Two approaches have been adopted in the AGRs to provide this access. Vertical methane access holes are provided in the fuel bricks and in the later stations, Heysham II and Tomess, a pressure drop from outside to inside the brick was established to cause an enhanced flow through the brick. The amount of inhibitor added must be restricted, however, because the carbon inhibition reaction product deposits on the fuel pin and restricts heat transfer to the coolant, thus reducing reactor efficiency. 

In the narrow sense, bis-maleimide resin means the thermosetting resin eom-posed of the bis-maleimide of methylene dianiline (BMI, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. 1). Beeause of the addition meehanism, the resin is eured without elimination, whieh is a eharacteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400 F) whieh typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

Novolacs are usually made under acidic conditions. Oxalic, sulfuric, toluene sulfonic, phenyl sulfonic, methane sulfonic, hydrochloric, and phosphoric acids are the most common catalysts, though nearly any moderately strong acid will probably do. Often selection of the acid has significant effects on the resultant polymer structure or performance. Sometimes acids are selected for their volatility, as it may be necessary to distill the acid off in some processes. 

The oxidation of nitric oxide, NO, is a reaction involved in smog production. It is moderately rapid at normal temperatures. The oxidation of methane, CHt (household gas), however, occurs so slowly at room temperature that we may say that, for all practical purposes it doesn t react at all. Again, the difference in the reaction rates must depend upon specific characteristics of the reactants, NO and CH,. 

Molybdenum and tungsten are unique in that they are resistant to sulfur, and, in fact, are commonly sulfided before use. The Bureau of Mines tested a variety of molybdenum catalysts (32). They are moderately active but relatively high temperatures are required in order to achieve good conversion, even at low space velocities. Selectivity to methane was 79-94%. Activity is considerably less than that of nickel. Although they are active with sulfur-bearing synthesis gas, the molybdenum and tungsten catalysts are not sufficiently advanced to be considered candidates for commercial use. 

The catalyst losses in either system are moderate and not excessively costly when inexpensive iron catalyst is used (as for production of liquid hydrocarbons). It is questionable, however, whether comparable losses of expensive nickel catalysts (for methanation) could be tolerated. For this reason, it is quite likely that the fluidized catalyst system will be used for methanation only after a cheap methanation catalyst is developed. 

Steam-Moderated Process. The basic idea behind this approach is to limit the extent of conversion of the methanation reaction, Reaction 1, by adding steam to the feed gases. This process simultaneously provides for (46) elimination of the CO shift, Reaction 2, to get a 3 1 H2 CO ratio from the make-up gas ratio of about 1.5 1 and avoidance of carbon laydown by operation under conditions in which carbon is not a thermodynamically stable phase (see Chemistry and Thermodynamics section above). 

The series of reactors and exchangers which methanates a raw syngas without pretreatment other than desulfurization is collectively termed bulk methanation. The chemical reactions which occur in bulk methana-tion, including both shift conversion and methanation, are moderated by the addition of steam which establishes the thermodynamic limits for these reactions and thereby controls operating temperatures. The flow sequence through bulk methanation is shown in Figure 1. 

R. T. Eddinger (Cogas Development Co.) Considering the cost and thermal inefficiency of methanation, is it realistic to consider methana-tion as the long-term competitor of moderate Btu gas having a heating value of 300-500 Btu ... 

L. Seglin We have heard today two rather novel approaches to methanation the steam-moderated RMProcess and the slurry methanation process. These are the results of new or recent R D. What can we visualize beyond that Would it be some other exotic process ... 

Dipyridiue-chromium(VI) oxide2 was introduced as an oxidant for the conversion of acid-sensitive alcohols to carbonyl compounds by Poos, Arth, Beyler, and Sarett.3 The complex, dispersed in pyridine, smoothly converts secondary alcohols to ketones, but oxidations of primary alcohols to aldehydes are capricious.4 In 1968, Collins, Hess, and Frank found that anhydrous dipyridine-chromium(VI) oxide is moderately soluble in chlorinated hydrocarbons and chose dichloro-methane as the solvent.5 By this modification, primary and secondary alcohols were oxidized to aldehydes and ketones in yields of 87-98%. Subsequently Dauben, Lorber, and Fullerton showed that dichloro-methane solutions of the complex are also useful for accomplishing allylic oxidations.6... 

Schlieren image of a very clear tulip or two-lip flame formed in a moderate length, square cross section tube (300mm long x 38.1mm on the side) from a stoichiometric methane/air mixture, with a line igniter across the left wall. 

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