Methane Andrussow process

Hydrogen cyanide is generally produced in industrial quantities by high temperature catalytic reaction between ammonia, methane, and air (the Andrussow process). The stoichiometry of the process is ... 

Hydrogen cyanide is an important building block chemical for the synthesis of a variety of industrially important chemicals, such as 2 hydroxy-4 methylthiobutyric acid, adiponitrile, nitrilotriacetic acid, lactic acid, and methyl methacrylate. The primary commercial routes to hydrogen cyanide are the reaction of methane and ammonia under aerobic (Andrussow Process) or anaerobic conditions (Degussa Process), or the separation of hydrogen cyanide as a by-product of the ammoxidation of propylene < ) The ammoxidation of methanol could represent an attractive alternate route to HCN for a number of reasons. First, on a molar basis, the price of methanol has become close to that of methane as world methanol capacity has increased. However, an accurate long term pricing picture for these two raw... 

One caveat pertains to the platinum oxide transport model It does not appear to be able to explain the differences in metal weight loss during ammonia oxidation and hydrogen cyanide synthesis by the Andrussow process. In the Andrussow process a mixture of methane, ammonia, and air is used to maintain a high temperature (1200°C) while generating hydrogen cyanide. Alternative processes require energy input, because HCN synthesis is an endothermic reaction. Thus, in both ammonia oxidation and HCN synthesis, platinum or alloy... 

Hydrogen cyanide (melting point -14°C, boiling point 26°C) is manufactured by the reaction of natural gas (methane), ammonia, and air over a platinum or platinum-rhodium catalyst at elevated temperature (the Andrussow process). 

The reactions in the Andrussow process are more complex than that shown in equation 72130. Most of the heat required for HCN formation is supplied by combustion of methane. This results in an overall reaction that is exothermic even though the endotherm of the methane-ammonia reaction is 60 kcal per mole of HCN129. The converter off-gas typically has the following composition ... 

In hydrogen cyanide synthesis using the Andrussow process, air, methane, and ammonia are fed over 15 to 50 layers of noble metal gauze at 1050 to 1150°C at near atmospheric pressure. 

For the Andrussow process the effect of diffusion limitation is to ensure that the composition of the gas phase at the catalyst surface is richer in NH3 and less rich in methane and oxygen than the bulk gas composition. This implies that the maximum HCN synthesis rates are achieved with surface CH4/NH3 and air/fuel ratios lower than those prevailing in the bulk gas phase. 

Figure 4.1 is a flow diagram of the Andrussow process [7], To avoid the decomposition of methane and ammonia, the ratio of reactants must be carefully controlled. The products are cooled where care is taken to avoid the formation of azulmic acids, polymers formed by the reaction between hydrogen cyanide, ammonia, and water. The products go to a scrubbing tower where unconverted ammonia is absorbed in sulfuric acid. The product is then absorbed in water, stripped, and distilled to produce greater than 99% HCN [8]. Yields are 70 and 60% for methane and ammonia, respectively. 

The Degussa BMA (Blausaure-Methan-Ammoniak, or hydrocyanic acid-methane-ammonia) process also is used in the production of hydrogen cyanide from methane. The difference between the Andrussow process and the Degussa process is that the latter does not use air in the synthesis of hydrogen cyanide. The reaction is as follows ... 

The Andrussow process this involves the ammoxidation of methane ... 

This reaction was first reported by Andmssov (Andrussow) in 1927. It is primarily an industrial process used to manufacture hydrogen cyanide from methane, ammonia, and oxygen over a catalyst of 90% Pt-10% Rh in the form of a pad of woven screens at 1050-1100° C and 2 atm. Therefore, this reaction is known as Andrussow process. In this process, the catalytic gauze is 3-5 mm thick, and when the high gas velocities are employed, the contact times achieved are of the order of a few milliseconds. The effluent stream contains about 8% HCN and a number of byproducts such as hydrogen, CO, and C02. It was reported that in 1978 the output of hydrogen cyanide exceeded 600 million pounds in the United States alone. ... 

There are several chemical processes that can be used to produce HCN for commercial purposes. All involve the reaction of ammonia with some type of hydrocarbon. The primary method used in the United States is called the Andrussow process, the reaction of ammonia, methane, and oxygen according to the following chemical equation ... 

Despite these high HCN yields, methanol ammoxidation technology for HCN manufacture has not displaced methane ammoxidation by the Andrussow process (see below) because of the former s inherent economic disadvantage in feedstock costs. Methanol, since it is currently manufactured on a large scale from methane-derived synthesis gas (CO and H2), is intrinsically a more expensive source of carbon than methane. 

Formaldehyde Ammoxidation. In addition to methanol ammoxidation, ammoxidation of formaldehyde is an alternative technology to the widely used Andrussow methane ammoxidation process (see section on Methane Ammoxidation) for the manufacture of HCN. 

Ammoxidation.) Formaldehyde is not an advantaged feedstock for the production of HCN because of its relatively high cost. Formaldehyde is produced commercially by the oxidation of methanol and is thus more costly than methanol [or methane, which is used in the commercial Andrussow process of methane ammoxidation to HCN (see below)] as a feedstock for HCN. Thus, formaldehyde ammoxidation has not generally been used for commercial manufacture of HCN. 

Fig. 7. Methane ammoxidation to HCN by the Andrussow process using recycle of unre-acted ammonia. Reprinted from Ref. (115), Cop5rright (1993), with permission from John Wiley Sons., Inc.

There have been no signiflcant catalyst advances for methane ammoxidation since the disclosure of the Pt/Rh catalyst by Andrussow in the 1930s (112). Advances in the technology have been in the areas of process operability process safety, especially pertaining to handling of potentially flammable and explosive hydrocarbon/oxygen gas mixtures and in product recovery and ammonia recycle. Because of its many years of safe and dependable operation and its use of low cost natural gas feedstock, the Andrussow process remains the dominant technology for the commercial manufacture of HCN. 

Andrussow Process. This process, developed by Dr. L. Andrussow in Germany in the early 1930s, has been the major process for large-scale HCN manufacture for the last three decades. (See Fig. 28.30.) The reaction of ammonia with methane to form HCN is as follows ... 

The reaction is very endothermic. The Andrussow process adds additional methane and air for in situ combustion to heat the reactants to the 1100°C reaction temperature and to provide the heat of reaction. The overall reaction then is ... 

German) prussic acid. CHN mol wt 27.03, C 44.44%, H 3.73%, N 51.83%. HCN. Prepd on a large scale by Che catalytic oxidation of ammonia-methane mixtures (Andrus-sow Process) see Andrussow, Angew. Chem. 48, 593 (1935) Maffezzoni, Chim. Ind. (Milan) 34, 460 (1952) Faith, Keyes Clark s Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Ed, (Wiley-Interscience, New York, 4th ed 1975) pp 482-486. May also be prepd by the catalytic decompn of formamide. Conveniently prepd in the laboratory by acidifying NaCN or KjtFefCN),) Glemser in Handbook of... 

Hydrogen cyanide is produced industrially by thermolysis of formamide, or from methane and ammonia on platinum-rhodium catalysts (following a process developed by Leonid Andrussow (1896-1988) in 1927 at BASF in Ludwigs-hafen) (Fig. 5.196). 

The most important process is the Andrussov oxidation invented by Leonid Andrussow at IG Farben in which methane and ammonia react in the presence of oxygen at about 1200 °C over a platinum catalyst ... 

Other Routes to HCN. The Andrussow and BMA processes are difficult to surpass on the basis of raw material cost. Methane is by far the most economical source of carbon except for coal. Ammonia is the cheapest source of nitrogen unless there is a technological breakthrough in the use of elemental nitrogen. A brief description of several processes using coal or nitrogen is presented below. However, these processes have yet to demonstrate commercial significance. 

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