Hydrogen cyanide synthesis

The direct fixation of nitrogen by its reaction with CH4 in a plasma has been studied extensively At low pressure hydrogen cyanide, acetylene and hydrog i are produced A kinetic study of the reaction in the pressure range 5-30 torr 

In inductively coupled rf discharges at 1-40 mbar Nj fixation as HCN increased very much in the presence of W, Ta and Mo 2 Molybdenum was most efficient 

Hydrogen cyanide is also produced in the plasma reactions of ammonia with methane and with benzene . Bundles of Ni inserted in a microwave discharge in mixtures of benzene and ammonia at a pressure of 40 mbar lowered the total conversion of benzene, but it had little effect on the conversion of ammonia. The nickel also altered the distribution of reactant products the formation of aniline was enhanced but the formation of HCN and C2H2 were reduced. 

The presence of hydrocarbons invariably leads to a brownish-yellow polymer deposit on the plasma walls. Laser action (X. = 337 pm) is observed in tubes containing this type of deposit if the discharge is maintained in pure H2, H2O or NH3. Schoetzau and Vepfek have explained the experimentally observed gain of HCN lasers in terms of the combined effects of volume processes and wall reactions — the latter include the formation of excited HCN by the reaction of H atoms with the deposit formed by discharge-activated polymerization of hydrocarbons in the laser tube. 

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Although active safety is provided by the control systems mentioned above, passive safety is an additional important feature of a distributed plant. Due to the low inventory, even a total release of the reaction volume or an explosion would create no significant impact on the environment [139]. To prevent such scenarios, a total containment of the plant is envisaged it needs to be sealed for life . Hydrogen cyanide synthesis and chlorine point-of-sale manufacture are two examples for safety-sensitive distributed syntheses. 

Proceedings [2] short mentioniong on the Degussa variant for hydrogen-cyanide synthesis (no details) [71] sections in reviews [87,88,90,96,97,114] trade press [81]. 

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... 

Closer inspection reveals that this somewhat superficial and largely self-evident evaluation is by no means exhaustive, and concrete experimental studies on adsorptive reactors expose both additional pitfalls and benefits that are often specific for a particular reaction system and decisive for the success or otherwise of adsorptive reactor concepts. Before illustrating this point with the help of four examples with which the author is personally acquainted - the Claus reaction, the direct hydrogen cyanide synthesis from ammonia and carbon monoxide and, to a lesser extent, the water-gas shift reaction and the Deacon process - it is worthwhile briefly reviewing other reaction systems for which the potential of adsorptive reactors has been examined (Tab. 7.2). 

Direct Hydrogen Cyanide Synthesis and Water-gas Shift Reaction... 

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. 

Hydrogen cyanide synthesis 1930s Chemicals CH4 -b NH3 -b 3/2O2 — HCN -b 3H2O 90%Pt-10% Rh wire gauze... 

Platinum/rhodium Hydrogen cyanide synthesis Gauzes... 

The use of supported platinum-based catalysts in hydrogen cyanide synthesis has been described, and some are in use in certain plants. For instance, Merrill and Perry recommended natural beryl coated with platinum or a platinum alloy [12], and a range of alternative supports were considered by Schmidt and his co-workers [13], including coated foamed ceramic and monolithic substrates. They are claimed to have some advantages in ammonia oxidation [14,15]. 

Hydrogen Cyanide Synthesis in a Thermal Radiofrequency Induction Plasma... 

The major part of these catalytic processes is carried out in fixed bed reactors. Some of the main fixed bed catalytic processes are listed in Table 11.1-1. Except for the catalytic cracking of gas oil, which is carried out in a fluidized bed to enable the continuous regeneration of the catalyst, the main solid catalyzed processes of today s chemical and petroleum refining industry appear in Table 11.1-1. However, there are also fluidized bed alternatives for phthalic anhydride— and ethylene dichloride synthesis. Furthermore, Table 11.1-1 is limited to fixed bed processes with only one fluid phase trickle bed process (e.g., encountered in the hydrodesulfurization of heavier petroleum fractions) are not included in the present discussion. Finally, important processes like ammonia oxidation for nitric acid production or hydrogen cyanide synthesis, in which the catalyst is used in the form of a few layers of gauze are also omitted from Table 11.1-1. 

Sherwood TK, Gilligand ER, big SW (1960) Hydrogen cyanide synthesis from its elements and from ammonia and carbon, bid Eng Chem 52 601-604... 

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