Ammonia from methane, production

Ammonia is by far the largest scale chemical product derived from methane. Production of ammonia and its downstream products nitric acid, urea, and ammonium nitrate, which currently rank 6th, 14th, 15th, and 17th in American volume of production, are discussed in Chapter 11. Two other petrochemicals derived from methane, methanol and formaldehyde, currently rank 21st and 24th in volume in the United States at about 4 million tonnes per year each. Details of their production will be outlined here. 

Amm oxida tion, a vapor-phase reaction of hydrocarbon with ammonia and oxygen (air) (eq. 2), can be used to produce hydrogen cyanide (HCN), acrylonitrile, acetonitrile (as a by-product of acrylonitrile manufacture), methacrylonitrile, hen onitrile, and toluinitnles from methane, propylene, butylene, toluene, and xylenes, respectively (4). 

It is convenient to divide the petrochemical industry into two general sectors (/) olefins and (2) aromatics and their respective derivatives. Olefins ate straight- or branched-chain unsaturated hydrocarbons, the most important being ethylene (qv), [74-85-1] propjiene (qv) [115-07-17, and butadiene (qv) [106-99-0J. Aromatics are cycHc unsaturated hydrocarbons, the most important being benzene (qv) [71-43-2] toluene (qv) [108-88-3] p- s.y en.e [106-42-3] and (9-xylene [95-47-5] (see Xylenes and ethylbenzene) There are two other large-volume petrochemicals that do not fall easily into either of these two categories ammonia (qv) [7664-41-7] and methanol (qv) [67-56-1]. These two products ate derived primarily from methane [74-82-8] (natural gas) (see Hydrocarbons, c -c ). 

As mentioned in Chapter 2, methane is a one-carhon paraffinic hydrocarbon that is not very reactive under normal conditions. Only a few chemicals can he produced directly from methane under relatively severe conditions. Chlorination of methane is only possible by thermal or photochemical initiation. Methane can be partially oxidized with a limited amount of oxygen or in presence of steam to a synthesis gas mixture. Many chemicals can be produced from methane via the more reactive synthesis gas mixture. Synthesis gas is the precursor for two major chemicals, ammonia and methanol. Both compounds are the hosts for many important petrochemical products. Figure 5-1 shows the important chemicals based on methane, synthesis gas, methanol, and ammonia. ... 

In gas separation with membranes, a gas mixture at an elevated pressure is passed across the surface of a membrane that is selectively permeable to one component of the mixture. The basic process is illustrated in Figure 16.4. Major current applications of gas separation membranes include the separation of hydrogen from nitrogen, argon and methane in ammonia plants the production of nitrogen from ah and the separation of carbon dioxide from methane in natural gas operations. Membrane gas separation is an area of considerable research interest and the number of applications is expanding rapidly. 

C16-0020. Chemists are optimistic that a catalyst will be found for the production of ammonia from hydrogen and nitrogen under standard conditions. In contrast, no hope exists of developing a catalyst for the production of hydrogen from methane and steam under standard conditions. Explain. 

HCN is produced commercially by the reaction of ammonia, methane, and air over a platinum catalyst or from the reaction of ammonia and methane. HCN is also obtained as a by-product in the manufacture of acrylonitrile and may be generated during many other manufacturing processes (Pesce 1994). In 1999, there were 34 companies operating 47 HCN production facilities in... 

Nitric acid is made from methane by first reacting CH4 with H2O to form syngas. Water is added to the CO + Hz mixture to form H2 and CO2 which is easily separated. Hydrogen is reacted with N2 from a liquid air plant. Ammonia is oxidized to NO over a Pt catalyst, and additional air is added to form NO2, and the product is dissolved in water. 

If the rich gas from the CRG reactor is passed over another bed of high-nickel catalyst at a lower temperature, the equilibrium of the five components is reestablished. Carbon oxides react with hydrogen to form methane and the calorific value of the gas is increased. It should be noted that this methanation step differs from that encountered in ammonia synthesis gas production because of the high steam content the temperature rise is reduced and there is no possibility of temperature runaway as the... 

Ozone decomposition in airplanes Selective catalytic reduction of NOx Arrays of corrugated plates Arrays of fibers Gauzes Ag Methanol -> formaldehyde Pt/Rh NO production from ammonia HCN production from methane Foams Catalytic membranes reactors... 

Gauzes are the state of the art for many millisecond-reactions performed in industry. The best-known examples are the oxidation of ammonia to NO for the production of nitric acid and the Andrussov process, in which HCN is produced from methane and ammonia (32) ... 

The reaction takes place under fuel-rich conditions to maintain a nonflammable feed mixture. Typical feed composition is 13% to 15% ammonia, 11% to 13% methane and 72% to 76% air on a volumetric basis. Control of feed composition is essential to guard against deflagrations as well as to maximize the yield. The yield from methane is approximately 60% of theoretical. Conversion, yields, and productivity of the HCN synthesis are influenced by the extent of feed gas preheat, purity of the feeds, reactor geometry, feed gas composition, contact time, catalyst composition and purity, converter gas pressure, quench time and materials of construction. 

Fig. 7.7. Flowsheet for the production of hydrogen from methane for ammonia synthesis and fuel cell applications indicating the potential for rationalization using an adsorptive reactor.

---