Hydrogen cyanide from plants

Reaction products other than hexamethylenetetramine may apparently be obtained from ammonia and formaldehyde in special instances. Fosse s studies of the mechanism by which urea, hydrogen cyanide, and other nitrogenous compounds are formed in plants indicates that ammonia and formaldehyde may be the pi ecursors of these products -. On oxidation in the presence of ammoniacal silver and mercury salts, formaldehyde is partly converted to hydrogen cyanide, from which urea can be produced... 

In early times hydrogen cyanide was manufactured from beet sugar residues and recovered from coke oven gas. These methods were replaced by the Castner process in which coke and ammonia were combined with Hquid sodium to form sodium cyanide. If hydrogen cyanide was desired, the sodium cyanide was contacted with an acid, usually sulfuric acid, to Hberate hydrogen cyanide gas, which was condensed for use. This process has since been supplanted by large-scale plants, using catalytic synthesis from ammonia and hydrocarbons. 

Plants for the production of sodium cyanide from Andmssow process or from acrylonitrile synthesis by-product hydrogen cyanide are operating in the United States, Italy, Japan, the UK, and AustraUa. In Germany, sodium cyanide is produced from BMA hydrogen cyanide, and in AustraUa one plant uses Fluohmic process hydrogen cyanide. 

Chlorination/oxidation of cyanide wastes from heat treatment plant Mixing cyanide with acids liberates hydrogen cyanide Hydrogen cyanide... 

Emissions to the atmosphere from ammonia plants include sulfur dioxide (SOj), nitrogen oxides (NOJ, carbon monoxide (CO), carbon dioxide (COj), hydrogen sulfide (HjS), volatile organic compounds (VOCs), particulate matter, methane, hydrogen cyanide, and ammonia. The two primary sources of pollutants, with typical reported values, in kilograms per ton (kg/t) for the important pollutants, are as follows ... 

Direct hydrogen cyanide (HCN) gas in a fuel oil gasification plant to a combustion unit to prevent its release. 4. Consider using purge gases from the synthesis process to fire the reformer strip condensates to reduce ammonia and methanol. 5. Use carbon dioxide removal processes that do not release toxics to the environment. When monoethanolamine (MEA) or other processes, such as hot potassium carbonate, are used in carbon dioxide removal, proper operation and maintenance procedures should be followed to minimize releases to the environment. 

Another acrylonitrile plant supplied by-product hydrogen cyanide to various other units. An inventory of 350,000 pounds of hydrogen cyanide was eliminated by having the other units draw directly from the acrylonitrile plant. This required considerable work to resolve many issues related to acrylonitrile purity and unit scheduling. 

Hexamethylenediamine is now made by three different routes the original from adipic acid, the electrodimerization of acrylonitrile, and the addition of hydrogen cyanide to butadiene. Thus, the starting material can be cyclohexane, propylene, or butadiene. Currently, the cyclohexane-based route from adipic acid is the most costly and this process is being phased out. The butadiene route is patented by DuPont and requires hydrogen cyanide facilities. Recent new hexamethylenediamine plants, outside DuPont, are based on acrylonitrile from propylene, a readily available commodity. 

Sulfuric acid, formaldehyde, and hydrogen cyanide are pumped into a glass-lined mixer (mixer 1, Ml, of Fig. 13). Particular care is exercised so that the three charge operations are carried out in the order indicated above, to ensure the stability of the mixture at all times. In a separate segment of the plant, ethylenediamine (EDA) and dilute sodium hydroxide are charged and mixed in mixer 3 (M3 in Fig. 13). The solutions from mixer 1 and mixer 3 are pumped to the reactor (REACTOR, Rl, in Fig. 13). When the reaction is complete, the reaction mixture is tested for traces of hydrogen cyanide. Dilute solution of formaldehyde is prepared in mixture 2 and is added to the reaction mbrture, if there is any HCN present. 

When the planning algorithms are run on this plant no MSVS is found since, in the worst-case state, there are no valves that will prevent hydrogen cyanide and formaldehyde from mixing in the region of overlap. Thus the computer will try to use the methodology described in the... 

Microorganisms associated with the roots of certain plants may produce or facilitate release of phytotoxins. For example, microbes in the rhizosphere of chamise (Adenostoma fasciculatum H. A.) appear to contribute to suppression of herbs near these shrubs (21), a phenomenon previously attributed to toxins washed from the chamise foliage (22, 23). Similarly, hydrogen cyanide, a potent phytotoxin,... 

Natural biogenic processes of bacteria, fungi, and cyanogenic plants such as sorghum, soybeans, and cassava, also release cyanide into the soil (Knowles 1988 Towill et al. 1978 WHO 1992). Cyanides (reported as cyanide, hydrogen cyanide, sodium cyanide, potassium cyanide, calcium cyanide, or copper(I) cyanide) have been detected in soil samples at 187 of the 406 hazardous waste sites, in sediment samples at 97 of the 406 hazardous waste sites, and in soil gas samples at 1 of the 406 hazardous waste sites where cyanides have been detected in some environmental medium (HazDat 1996). The HazDat information used includes data from both NPL and other Superfund sites. 

Over 2,650 plant species can produce hydrogen cyanide (Seigler 1991 Swain et al. 1992). These include edible plants such as almonds, pits from stone fruits (e.g., apricots, peaches, plums, cherries), sorghum, cassava, soybeans, spinach, lima beans, sweet potatoes, maize, millet, sugarcane, and bamboo shoots (Fiksel et al. 1981). The cyanogenic glycoside content of a foodstuff is usually expressed as the amount of cyanide released by acid hydrolysis glycoside concentrations are rarely reported (WHO 1992). 

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