Ammonia and Methane

Co-oxidation of Ammonia and Methane.—Very little has been published during the review period of fundamental value either for methane alone or for both reactants. In normal industrial practice a 10% Rh/Pt gauze catalyst operates at 1100 °C and 1—2 atm pressure. The feed mixture is fuel rich and may contain 

The process is usually operated with excess of methane to maximize yield of HCN on ammonia used. Oxygen and methane react completely and some ammonia is recovered, but the presence of nitrogen in the products indicates that some ammonia decomposition occurs. Again the proportion of hydrogen in the product indicates some cracking of the methane as well. Traces of acetonitrile and acrylonitrile may also be found but oxides of nitrogen are not found under these conditions. 

Further light on the carbon contamination has been obtained by Hori and Schmidt during a study of CO oxidation between 430 and 1230 °C at 0.1 Torr over Pt wires. They found slow transients ( 10s time constants where the system time constant was 1 s) which AES showed were due to the formation of carbonaceous films. These films were laid down between 430 and 930 °C even when the reaction mixture was oxygen rich. Simultaneously the surface became microfacetted on a 0.5 [xm size scale. 

Pan states that CH4 is more reactive than ammonia so that there is likely to be some mass transfer limitation on methane as well as ammonia. Making an assumption that the surface mole fractions of reactants will be of the order of half the bulk gas-phase levels, approximate reaction probabilities for NH3 and CH4 can be calculated. Collision rates are about 2 x 10 molecules cm s so that the reaction probability for ammonia and methane is about 10 and for oxygen about 2.5 x 10 . These are sufficiently close to the values for independent oxidation of CH4 and NH3 to make it likely that the same surface reactions are also involved in the co-oxidation. 

NH3/O2 reactions should be studied at low pressures on both clean and contaminated platinum surfaces to determine whether the relative reactivities at 1100 °C are in agreement with the hypothesis. Such experiments would also help to determine whether the methane reacts wholly at the surface or not. The balance of evidence reviewed above does slightly favour the reaction of methane solely at the surface, but definitive experiments are desirable on this point. 

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Water ammonia and methane share the common feature of an approximately tetra hedral arrangement of four electron pairs Because we describe the shape of a molecule according to the positions of its atoms rather than the disposition of its electron pairs however water is said to be bent and ammonia is trigonal pyramidal... 

Two synthesis processes account for most of the hydrogen cyanide produced. The dominant commercial process for direct production of hydrogen cyanide is based on classic technology (23—32) involving the reaction of ammonia, methane (natural gas), and air over a platinum catalyst it is called the Andmssow process. The second process involves the reaction of ammonia and methane and is called the BlausAure-Methan-Ammoniak (BMA) process (30,33—35) it was developed by Degussa in Germany. Hydrogen cyanide is also obtained as a by-product in the manufacture of acrylonitrile (qv) by the ammoxidation of propjiene (Sohio process). 

In the BMA process, methane (natural gas) and ammonia are reacted without air being present (44). The reaction is carried out in tubes that are heated externally to supply the endothermic heat of reaction very similar to a reformer. Yield from ammonia and methane is above 90%. The off-gas from the converter contains more than 20 mol % hydrogen cyanide, about 70 mol % hydrogen, 3 mol % ammonia, 1 mol % methane, and about 1 mol % nitrogen from ammonia decomposition. 

Hydrogen cyanide is produced via the Andrussaw process using ammonia and methane in presence of air. The reaction is exothermic, and the released heat is used to supplement the required catalyst-bed energy ... 

A platinum-rhodium ahoy is used as a catalyst at 1100°C. Approximately equal amounts of ammonia and methane with 75 vol % air are introduced to the preheated reactor. The catalyst has several layers of wire gauze with a special mesh size (approximately 100 mesh). 

The giant planets possess low surface temperatures and have atmospheres that extend several thousand miles. The markings on Jupiter, the largest planet, consist of cloud formations composed of methane containing a small amount of ammonia. The atmosphere of Jupiter absorbs the extreme red and infrared portions of the spectrum. These absorptions correspond to the absorption spectra of ammonia and methane, suggesting the presence of these gases in Jupiter s... 

C04-0017. Suppose that the industrial synthesis of HCN described in Example is carried out using 5.00 X 10 kg each of ammonia and methane in excess oxygen. What is the maximum mass of HCN that could be produced, and what mass of which reactant would be left over ... 

Ward BB (1987) Kinetic studies on ammonia and methane oxidation by Nitrosococcus oceanus. Arch Microbiol 147 126-133. 

Hydrogen cyanide (Table 15.1) is a colorless, flammable liquid or gas that boils at 25.7°C and freezes at minus 13.2°C. The gas rarely occurs in nature, is lighter than air, and diffuses rapidly. It is usually prepared commercially from ammonia and methane at elevated temperatures with a platinum catalyst. It is miscible with water and alcohol, but is only slightly soluble in ether. In water, HCN is a weak acid with the ratio of HCN to CN about 100 at pH 7.2, 10 at pH 8.2, and 1 at pH 9.2. HCN can dissociate into H+ and CN. Cyanide ion, or free cyanide ion, refers to the anion CN derived from hydrocyanic acid in solution, in equilibrium with simple or complexed cyanide molecules. Cyanide ions resemble halide ions in several ways and are sometimes referred to as pseudohalide ions. For example, silver cyanide is almost insoluble in water, as are silver halides. Cyanide ions also form stable complexes with many metals. 

For example, Dalton designed a system of symbols to show how atoms combine to form other substances. Figure 3.2 on the next page shows several of these symbols. As you will no doubt notice, Dalton correctly predicted the formulas for carbon dioxide and sulfur trioxide, but ran into serious trouble with water, ammonia, and methane. Dalton s attempt at molecular modelling highlights a crucial limitation with his atomic model. Chemists could not use it to explain why atoms of elements combine in the ratios in which they do. This inability did not prevent chemists from pursuing their studies. It did, however, suggest the need for a more comprehensive atomic model. 

The components of the rotational g tensor of hydrogen fluoride, water, ammonia and methane have been calculated at their equilibrium geometries with different correlated ab initio methods and two large basis sets. 

NOTTS Use cod, but not very cold water in the condenser. Due to the high freezing point oi l 1CN the use of odd water may cause it to crystallize in the condenser. This process is an improvement over the old method using ferrocyanide in that it results in a product of greater purity. Commercial HCN is currently produced by reacting ammonia and methane gases in an arc furnace. While extremely cheap and effective, it is not very suitable fir small scale production. 

The atmosphere of modern Earth is thought to be very different from that of early Earth. Scientists conjecture that Earth s first atmosphere consisted of carbon dioxide, water vapor, nitrogen, and hydrogen sulfide, with trace amounts of ammonia and methane. The gases in the atmosphere are thought to have been released from the interior of the planet by volcanic eruptions. At this early... 

Common names of chemical compounds are generally much shorter than the corresponding systematic names. The systematic names for water, ammonia, and methane, for example, are dihydrogen monoxide, H20 trihydrogen nitride, NH3 and tetrahydrogen carbide, CH4. For these compounds, which would you rather use common names or systematic names ... 

Look at the following computer-generated ball-and-stick models of water, ammonia, and methane. Each of these molecules—and every other molecule as well— has a specific three-dimensional shape. Often, particularly for biologically important molecules, three-dimensional shape plays a crucial part in determining the molecule s chemistry. 

Gases. Some gases that can harm aquatic freshwater life include chlorine, ammonia, and methane. 

Ponton [60] discusses exemplarily a miniplant concept for performing the Andrussov process, yielding hydrogen cyanide from methane, oxygen and ammonia with a platinum catalyst. HCN is a widely used but highly toxic chemical which requires extreme safety issues, in particular when it is transported or shipped. A miniplant should allow one to produce this toxic material from comparably low toxic ammonia and methane directly on-site at the customer and on-demand in small or even bigger quantities. 

Figure 6.2 Structures of water, ammonia and methane that quench orbital angular momentum...

Fig. 8 Interannual variability of the winter NAO index (averaged for November-Febru-ary), winter air temperature in Gelendzhik, temperature in the CIL core in the northeastern Black Sea (data of V.G. Krivosheya), the averaged content of oxygen in the CIL (in the layer ag = 14.45-14.60 kg m 3), and onsets in the density field of hydrogen sulfide, total manganese, ammonia, and methane (from top to bottom)...

Coucouvanis, D., Mosier, P.E. Malinak, S. Laughlin, L. Demadis, K.D. (1995) Catalytic reduction of hydrazine and acetylene to ammonia and ethylene and stoichiometric reduction of CN to ammonia and methane by Fe/M/S clusters (M =Mo, V) with structural features similar to those of the Fe/Mo/S site in nitrogenase, Plant Sci. Biotechnol. Agric. (Nitrogen Fixation Fundamentals and Applications) 27, 137-42. 

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