Andrussow process for HCN

Bodke AS, Olschki DA, Schmidt LD. Hydrogen addition to the Andrussow process for HCN synthesis. Appl Catal A General 2000 201 13-22. 

How does the BMA process differ from the Andrussow process for HCN production Speculate 12.6 on added dangers of the BMA process versus the Andrassow process. 

Let us take the bond conservation idea introduced in the previous section for AH, and apply it to CH,-NH with x,y = 0-2 surface intermediates. These intermediates occur, for example, during the Degussa and Andrussow process for HCN synthesis from CH4 and We may assume that the C and... 

The unreacted ammonia is removed from the crude by scrubbing with sulfuric acid for disposal as ammonium sulfate. Similarly to the Andrussow process, the HCN is separated from the crude via absorption into water with H2SO4 added as inhibitor against polymerization. The vent gas from the HCN absorber consists of ... 

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... 

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 ... 

Six processes are presently of economic significance the Andrussow process is currently the principal HCN manufacturing process in the world, the BMA process is practiced by two companies and provides high yield and selectivity by using a complex reaction system, the Fluohmic process is of interest in locations where electricity is inexpensive, the formamide process is useful for sites with inexpensive carbon monoxide, the BP (British Petroleum) acrylonitrile process produces HCN as a byproduct, and the methanol process. 

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. 

Hazardous Product. The synthesis of hydrogen cyanide (HCN) is an example of a fast, high-temperature process that generates a hazardous gas. Researchers at the Institut fiir Microtechnik Mainz, Germany, aimed to develop a portable on-site, on-demand HCN-generating unit [1]. The Andrussow process was selected for generating HCN on the microscale. The reaction can be written as... 

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. 

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. 

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. 

At the current time, almost all HCN is produced on a large scale using one of two methods the Andrussow process or the Degussa process (see descriptions below). In addition to nylon manufacture, HCN is used for synthesis of many specialty chemicals. Companies, such as DuPont, currently supply the HCN for these processes via transport of HCN in... 

In this method, platinum is coated on the inside of alumina tubes, which are then placed in a fired furnace. The product HCN in this method is of a higher concentration than in the Andrussow process, and no wastewater is produced. A disadvantage is the large financial investment needed for the process. 

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 gas feed for ammonia oxidation is normally oxygen rich ( 10% NHa/air stoicheiometric ratio 14% NHs/air) but the Andrussow HCN process is operated on the fuel-rich side of stoicheiometric [(CH4 + NH3VO2 = 1.5]. The likely surface chemistry under both conditions is therefore of interest. 

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. 

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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