Methane reaction with ammonia

The oxidation and the partial oxidation method, the CO2 from an ammonia plant in a reaction with methane, and water all produce different ratios of CO and H2. In addition, CO2 can be removed by solvent extraction. So, the trick is to use two or three of these processes to get the C0 H2 ratio to about 1 2. 

Degussa developed the BMA (Blausaure-Methan-Ammoniak, or HCN-methane-ammonia) process around 1949 in cooperation with Heinrich Koppers GmbH. In the process, ammonia reacts with methane in the absence of oxygen in a gas-fired tubular reactor. US patent 5,785, 942 describes the BMA process and improvements that were made during the mid 1990 s. The reaction is46 ... 

Chemistry Due to its high toxicity, when needed for laboratory use, it is common for HCN to be used in situ. A typical procedure employing potassium cyanide and dilute sulfuric acid is outlined by Streitwieser and Heathcock (1976). A synthesis using sodium cyanide and sulfuric acid is available (Ziegler, 1941). HCN can be prepared commercially by several routes, including the reaction of ammonia/air with methane. 

However, it is worth returning to the chemistry of hexamethylenetetramine (1,3,5,7-tetraazaadamantane or l,3,5,7-tetraazatricyclo[3.3.1.H ]decane, C6H12N4, Chapter 9 and Table 10.2) that is formed by the condensation of ammonia (NH3) with methanal (formaldehyde, H2OO). As was noted as early as 1895 by M. Delepine, in a reaction now bearing his name, alkyl halides react with hexamethylenetetramine to produce A-substituted derivatives of the hexamethylenetetramine, which can then be hydrolyzed to aldehyde, ammonia, and substituted amine. Not unexpectedly, it has become clear that benzyhc and allylic halides react best (Scheme 10.30). 

The oxidation of the hydrogen is not complete so that the converter off-gas contains hydrogen. The overall reaction is carried out adiabaticaHy. This is accomphshed by the addition of air (O2). The air oxidizes a portion of the methane, making the overall reaction exothermic, even though the reaction of methane with ammonia to form hydrogen cyanide is quite endothermic. 

The Degussa process, on the other hand, reacts ammonia with methane in absence of air using a platinum, aluminum-ruthenium ahoy as a catalyst at approximately 1200°C. The reaction produces hydrogen cyanide and hydrogen, and the yield is over 90%. The reaction is endothermic and requires 251 KJ/mol. 

Oxygen-containing molecules cannot be tolerated in the ammonia synthesis, primarily because they form iron oxide that blocks the active surface. First the CO2 is removed, through a scrubber, by reaction with a strong base. The remaining CO (and CO2) is then removed by the methanation reaction, converting the CO into methane and water. Finally the water is removed by, for example, molecular sieves. Methane does not present problems because it interacts weakly with the catalyst surface. The gas mixture (Tab. 8.6) is compressed to the roughly 200 bar needed for ammonia synthesis and admitted to the reactor. 

Fig. 4.2 Comparison of amino acid yields using CH4, CO and CO2 as carbon sources with the addition of varying amounts of H2. The yields were calculated on the basis of the amount of carbon present in the reaction mixture. In all cases, the partial pressures of nitrogen, methane, carbon monoxide and carbon dioxide were lOOmmHg. For the reactions using nitrogen, the reaction vessel contained 100 mL of water, but no ammonia. Reactions involving nitrogen and ammonia were carried out using 100 mL of ammonium chloride (0.05 M). The electrical discharge experiments took 48 hours at room temperature (Schlesinger and Miller, 1983)...

Wan and Koch [78] also developed a method for producing HCN on a small scale by reaction of methane with ammonia, Scheme 10.15. 

Ammonia is synthesised from its elements nitrogen and hydrogen. The nitrogen is obtained by the fractional distillation of liquid air. The hydrogen is obtained by the reaction of methane (from natural gas) with steam. 

This enzyme [EC 1.14.13.25] catalyzes the reaction of methane with NAD(P)H and dioxygen to produce methanol, NAD(P), and water. This enzyme is reported to exhibit a broad specificity. Many alkanes can be hydrox-ylated and alkenes are converted into the corresponding epoxides. Carbon monoxide is oxidized to carbon dioxide, ammonia is oxidized to hydroxylamine, and some aromatic compounds and cyclic alkanes can also be hy-droxylated, albeit not as efficiently. 

The methanal and ammonia that split off the cage structure during the reaction with nitric acid need not be wasted. In the large-scale manufacture of cyclonite, a combination of nitric acid, ammonium nitrate, and ethanoic anhydride is used, which results in full utilization of the methanal and ammonia ... 

Another conventional ionization technique termed chemical ionization (Cl), utilizes a reagent gas (such as isobutane, methane, ammonia) to form reagent ions (Rif) which can undergo ion-molecule reactions with the compound of interest to form protonated molecules. 

The reactor can operate with either a liquid-phase reaction or a gas-phase reaction. In both types, temperature is very important. With a gas-phase reaction, the operating pressure is also a critical design variable because the kinetic reaction rates in most gas-phase reactions depend on partial pressures of reactants and products. For example, in ammonia synthesis (N2 + 3H2 O 2NH3), the gas-phase reactor is operated at high pressure because of LeChatelier s principle, namely that reactions with a net decrease in moles should be mn at high pressure. The same principle leads to the conclusion that the steam-methane reforming reaction to form synthesis gas (CH4 + H20 O CO + 3 H2) should be conducted at low pressure. 

Sodium benzenetellurolate is arylated in liquid ammonia via photoinduced reactions with aryl halides3,4. Aryl iodides reacted with sodium benzenetellurolate in the presence of copper(I) iodide in hexamethylphosphoric triamide (but not in DMF or DMSO) to produce aryl phenyl tellurium compounds5- However, lithium benzenetellurate reacted with 1,2-bromoiodobenzene and lithium methane tellurolate with 1,2-dibromobenzene in tetrahydrofuran at 20° to yield l,2-bis[organotelluro]benzenes6. 

As can be seen from the above equation, formation of HCN is in reality a hetero-bimolecular oxidative coupling reaction of methane with ammonia. The ammoxidation reactor construction is a simple fixed-bed multi-tube and the catalyst is usually a platinum or sometimes a Group V or VI metal oxide on a silica or alumina support. The HCN product is recovered by condensation and fractionation. With the reaction simplicity and yield, and widespread availability of starting materials, in-situ HCN generation is an ideal industry solution to HCN supply. (See Chapter 29 for more details.)... 

The modem industrial synthesis of liCN is based on methane ammonia reactions, although higher alkanes are used m iheShawinigan process. Ttie mechanism of these reactions probably proceeds through the formation of methylene iminc (CH2= NH) as (he intermediate, since this compound is obtained with a nickel base catalyst under similar conditions. 

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