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Raw materials And Preparation Products

Hazard Information

Material Safety Data Sheet(MSDS)

Questions And Answer

• Chemical structure

  Lewis structure
  Ball-and-stick diagram
  Space-filling model
  Urea, also known as carbamide, is an organic compound with chemical formula CO (NH2)2. This amide has two –NH2 groups joined by a carbonyl (C=O) functional group.;

• History

  Pure urea was first isolated from urine in 1727 by the Dutch scientist Herman Boerhaave, and he extracted urea from urine by working with the concentated-by-boiling residue. But if only not considering the purity of urea, the discovery of urea should be attributed to the French chemist Hilaire Rouelle, and he prepared urea (or its addition compound with sodium chloride) from urine some time before 1727.
  In 1828, just 55 years after its discovery, urea became the first organic compound to be synthetically formulated, this time by a German chemist named Friedrich Wöhler, one of the pioneers of organic chemistry. It was found when Wohler attempted to synthesis ammonium cyanate, to continue a study of cyanates which he had been carrying out for several years. On treating silver cyanate with ammonium chloride solution he obtained a white crystalline material which proved identical to urea obtained from urine.
  AgNCO + NH4Cl → (NH2)2CO + AgCl
  Synthetic urea is created from synthetic ammonia and carbon dioxide and can be produced as a liquid or a solid. The process of dehydrating ammonium carbamate under conditions of high heat and pressure to produce urea was first implemented in 1870 and is still in use today. Uses of synthetic urea are numerous and therefore production is high. Approximately one million pounds of urea is manufactured in the United States alone each year, most of it used in fertilizers. Nitrogen in urea makes it water soluble, a highly desired property in this application. ;

• Occurrence

  Urea is the chief nitrogenous end product of the metabolic breakdown of proteins in all mammals and some fishes. The material occurs not only in the urine of all mammals but also in their blood, bile, milk, and perspiration. In the course of the breakdown of proteins, amino groups (NH2) are removed from the amino acids that partly comprise proteins. These amino groups are converted to ammonia (NH3), which is toxic to the body and thus must be converted to urea by the liver. The urea then passes to the kidneys and is eventually excreted in the urine.
  
  
  Fig.1 The urea cycle in animals;

• Physical properties

  
  Fig.2 Urea crystal
  
  It is a colourless, crystalline substance that melts at 132.7°C (271°F) and decomposes before boiling. Its density is 1.32 g/cm3 and It is highly soluble in water and contains 46.7% nitrogen.;

• Chemical Properties

  The urea molecule is planar in the crystal structure, but the geometry around the nitrogens is pyramidal in the gas-phase minimum-energy structure. In solid urea, the oxygen center is engaged in two N-H-O hydrogen bonds. The resulting dense and energetically favourable hydrogen-bond network is probably established at the cost of efficient molecular packing: The structure is quite open, the ribbons forming tunnels with square cross-section. The carbon in urea is described as sp2 hybridized, the C-N bonds have significant double bond character, and the carbonyl oxygen is basic compared to, say, formaldehyde. Urea's high aqueous solubility reflects its ability to engage in extensive hydrogen bonding with water.
  Urea dissolved in water is in equilibrium with the isomeric ammonium cyanate. The resulting activity of the isocyanic acid ions do result in carbamylation (formation of long-chain carbamides, liberating ammonia molecule as byproduct) of proteins if proteins are present in the solution too. The carbamylation reaction may occurs at elevated temperatures even without catalysts. At room temperature, water solutions of urea are prone to same decomposition reaction in the presence of urease. The isomerization of urea in solution at room temperature without catalysts is a slow process (taking days to reach equilibrium), and freshly prepared, unheated solutions had negligible carbamylation rates.Urea can react with alcohols to form urethanes and react with malonic esters to make barbituric acids. ;

• Productions

  The primary raw material used to manufacture urea is natural gas, which ties the costs directly to gas prices. Consequently, new plants are only being built in areas with large natural gas reserves where prices are lower. Finished product is transported around the globe in large shipments of 30,000 metric tons. The market price for urea is directly related to the world price of natural gas and the demand for agricultural products. Prices can be very volatile, and at times, unpredictable. TCC is positioned to know the world markets and keep your prices competitive.
  Annual production of sulfuric acid
  ▼

  ▲

  World

  164 million tonnes

  China

  62 million tonnes

  India

  23 million tonnes

  Middle East

  20 million tonnes

  Rest of Asia

  18 million tonnes

  FSU

  12 million tonnes

  North America

  9.5 million tonnes

  Europe

  9.5 million tonnes
  It is expected that the global annual production will increase to over 200 million tonnes by 2018.
  1. Potash Corporation, 2013
  2. International Fertilizer Industry Association, 2014 ;

• Production methods

  Historical process
  Urea was first noticed by Hermann Boerhaave in the early 18th century from evaporates of urine. In 1773, Hilaire Rouelle obtained crystals containing urea from human urine by evaporating it and treating it with alcohol in successive filtrations. This method was aided by Carl Wilhelm Scheele's discovery that urine treated by concentrated nitric acid precipitated crystals. Antoine François, comte de Fourcroy and Louis Nicolas Vauquelin discovered in 1799 that the nitrated crystals were identical to Rouelle's substance and invented the term "urea." Berzelius made further improvements to its purificationand finally William Prout, in 1817, succeeded in obtaining and determining the chemical composition of the pure substance. In the evolved procedure, urea was precipitated as urea nitrate by adding strong nitric acid to urine. To purify the resulting crystals, they were dissolved in boiling water with charcoal and filtered. After cooling, pure crystals of urea nitrate form. To reconstitute the urea from the nitrate, the crystals are dissolved in warm water, and barium carbonate added. The water is then evaporated and anhydrous alcohol added to extract the urea. This solution is drained off and evaporated, leaving pure urea.
  
  Industrial process
  For use in industry, urea is produced from synthetic ammonia and carbon dioxide. As large quantities of carbon dioxide are produced during the ammonia manufacturing process as a byproduct from hydrocarbons (predominantly natural gas, less often petroleum derivatives), or occasionally from coal, urea production plants are almost always located adjacent to the site where the ammonia is manufactured.
  Urea can be produced as prills, granules, pellets, crystals, and solutions. The prills are formed by spraying molten urea down a tower up which air is pumped. They are slightly smaller than urea sold as granules and are particularly useful when the fertilizer is being applied by hand. In admixture, the combined solubility of ammonium nitrate and urea is so much higher than that of either component alone that it is possible to obtain a stable solution (known as UAN) with a total nitrogen content (32%) approaching that of solid ammonium nitrate (33.5%), though not, of course, that of urea itself (46%).
  
  Fig.3 Industrial process of urea
  
  Fig.4 An aerial view of a large plant in Alberta, Canada, in which ammonia is synthesized and then converted to urea.( By kind permission of Agrium Inc.)
  
  Fig.5 Prills(small spheres of urea)
  
  Fig.6 UAN(admixture of urea and ammonium nitrate)Laboratory process
  Ureas in the more general sense can be accessed in the laboratory by reaction of phosgene with primary or secondary amines, proceeding through an isocyanate intermediate. Non-symmetric ureas can be accessed by reaction of primary or secondary amines with an isocyanate.
  Also, urea is produced when phosgene reacts with ammonia:
  COCl2 + 4 NH3 → (NH2)2CO + 2 NH4Cl
  Urea is byproduct of converting alkyl halides to thiols via a S-alkylation of thiourea. Such reactions proceed via the intermediacy of isothiouronium salts:
  RX + CS(NH2)2 → RSCX(NH2)2X
  RSCX(NH2)2X + MOH → RSH + (NH2)2CO + MX
  In this reaction R is alkyl group, X is halogen and M is alkali metal.;

• Uses

  Agriculture uses
  More than 90% of world industrial production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has the lowest transportation costs per unit of nitrogen nutrient.
  In the soil, it hydrolyses back to ammonia and carbon dioxide. The ammonia is oxidized by bacteria in the soil to nitrate, which can be absorbed by the plants. Urea is also used in many multi-component solid fertilizer formulations. Urea is highly soluble in water, therefore, very suitable for use in fertilizer solutions (in combination with ammonium nitrate: UAN), e.g., in ‘foliar feed’ fertilizers. For fertilizer use, granules are preferred because of their narrower particle size distribution, an advantage for mechanical application. The most common impurity of synthetic urea, biuret, must be present at less than 2 percent of the time, as it impairs plant growth.
  
  Fig.7 Urea fertilizer and farmer’s fertilization process
  
  Pharmacaeutical
  Urea and malonic acid react to form barbituric acid. This was discovered by Adolf Bayer in 1864. But the barbiturates were not exploited as hypnotics until the early 1900's.Urea is also used in the production of various acylureas and urethanes for use as sedatives and hypnotics.
  
  Fig.8 Synthesis of barbituric acid
  
  Chemical industry
  Urea is a raw material for the manufacture of two main classes of materials: urea-formaldehyde resins and urea-melamine-formaldehyde used in marine plywood. They all have very varied uses including adhesives, laminates, moulding compounds, coatings and textile finishes.
  Urea has the ability to trap many organic compounds in the form of clathrates. The organic compounds are held in channels formed by interpenetrating helices comprising of hydrogen-bonded urea molecules. This behavior can be used to separate mixtures, and has been used in the production of aviation fuel and lubricating oils, and in the separation of paraffin.
  As the helices are interconnected, all helices in a crystal must have the same molecular handedness. This is determined when the crystal is nucleated and can thus be forced by seeding. The resulting crystals have been used to separate racemic mixtures.
  
  Laboratory uses
  Urea in concentrations up to 10 M is a powerful protein denaturant as it disrupts the noncovalent bonds in the proteins. This property can be exploited to increase the solubility of some proteins. A mixture of urea and choline chloride is used as a deep eutectic solvent, a type of ionic liquid.
  Urea can in principle serve as a hydrogen source for subsequent power generation in fuel cells. Urea present in urine/wastewater can be used directly (though bacteria normally quickly degrade urea.) Producing hydrogen by electrolysis of urea solution occurs at a lower voltage (0.37 V) and thus consumes less energy than the electrolysis of water (1.2 V).
  Urea in concentrations up to 8 M can be used to make fixed brain tissue transparent to visible light while still preserving fluorescent signals from labeled cells. This allows for much deeper imaging of neuronal processes than previously obtainable using conventional one photon or two photon confocal microscopes.
  
  Automobile systems
  Urea is used in SNCR and SCR reactions to reduce the NOx pollutants in exhaust gases from combustion, for example, from power plants and diesel engines. The BlueTec system, for example, injects water-based urea solution into the exhaust system. The ammonia produced by decomposition of the urea reacts with the nitrogen oxide emissions and is converted into nitrogen and water within the catalytic converter.
  
  Fig.9 A line diagram of the car above illustrating five key elements in the design of the exhaust system.
  1 The oxidation catalyst is used to remove unwanted hydrocarbons, ensuring that they are oxidised to carbon dioxide and water. The catalyst is usually based on platinum or palladium.
  2 Known as an NOx catalytic convertor, it contains aluminium oxide on whose surface, platinum and barium oxide are present. It traps the oxides of nitrogen. When the solid is saturated with the oxides, unburnt hydrocarbons are allowed to flow through, converting much of the mixture to nitrogen, carbon dioxide and water vapour.
  3 A filter which traps particulates (small pieces of carbon and other solids).
  4 A tank containing the solution of urea.
  5 The SCR-catalytic convertor which contains another catalyst, for example an oxide of vanadium (or tungsten) on titanium dioxide, which allows the exhaust gases, still containing some nitrogen oxides, to react with ammonia formed from the urea solution, to produce exhaust gases with only traces of the oxides. By kind permission of Daimler AG
  
  Others
  A stabilizer in nitrocellulose explosive
  A component of animal feed, providing a relatively cheap source of nitrogen to promote growth
  A non-corroding alternative to rock salt for road de-icing, and the resurfacing of snowboarding half pipes and terrain parks
  A flavor-enhancing additive for cigarettes
  A main ingredient in hair removers such as Nair or Veet
  A browning agent in factory-produced pretzels
  An ingredient in some hair conditioners, facial cleansers, bath oils, skin softeners, and lotions
  A reactant in some ready-to-use cold compresses for first-aid use, due to the endothermic reaction it creates when mixed with water
  A cloud seeding agent, along with other salts
  A flame-proofing agent, commonly used in dry chemical fire extinguisher charges such as the urea-potassium bicarbonate mixture.
  An ingredient in many tooth whitening products
  An ingredient in dish soap
  Along with ammonium phosphate, as a yeast nutrient, for fermentation of sugars into ethanol
  A nutrient used by plankton in ocean nourishment experiments for geoengineering purposes
  As an additive to extend the working temperature and open time of hide glue
  As a solubility-enhancing and moisture-retaining additive to dye baths for textile dyeing or printing;

• Hazards

  Health hazards
  Inhalation: 
  Causes irritation to the respiratory tract. Symptoms may include coughing, shortness of breath. May be absorbed into the bloodstream with symptoms similar to ingestion. 
  Ingestion: 
  Causes irritation to the gastrointestinal tract. Symptoms may include nausea, vomiting and diarrhea. May also cause headache, confusion and electrolyte depletion. 
  Skin Contact: 
  Causes irritation to skin. Symptoms include redness, itching, and pain. 
  Eye Contact: 
  Causes irritation, redness, and pain. 
  Chronic Exposure: 
  A study of 67 workers in an environment with high airborne concentrations of urea found a high incidence of protein metabolism disturbances, moderate emphysema, and chronic weight loss. 
  Aggravation of Pre-existing Conditions: 
  Supersensitive individuals with skin or eye problems, kidney impairment or asthmatic condition should have physician's approval before exposure to urea dust.
  
  Fire Hazards
  Behavior in Fire: Melting and decomposing to generate ammonia.
  Not combustible. Gives off irritating or toxic fumes (or gases) in a fire.
  https://pubchem.ncbi.nlm.nih.gov/compound/urea#section=EPA-Safer-Chemical
  
  Handling and Storage
  Keep in a tightly closed container, stored in a cool, dry, ventilated area. Protect against physical damage. Isolate from incompatible substances. Containers of this material may be hazardous when empty since they retain product residues (dust, solids); observe all warnings and precautions listed for the product. ;

• Reference

  1. https://en.wikipedia.org/wiki/Urea#Explosives
  2. https://www.chemicalbook.com/ProductChemicalPropertiesCB5853861_EN.htm
  3. https://chemistry.stackexchange.com/questions/54387/extracting-urea-from-urine/60338#60338
  4. http://www.chm.bris.ac.uk/motm/urea/urea.html 
  5. https://thechemco.com/chemical/urea/  
  6. file:///C:/Users/zl/Desktop/kurzer1956.pdf
  7. https://www.britannica.com/science/urea 
  8. http://www.expertsmind.com/topic/biochemistry/urea-cycle-96120.aspx
  9. http://sesl.com.au/blog/what-is-urea/ 
  10. http://www.essentialchemicalindustry.org/chemicals/urea.html 
  11. http://www.atmos.umd.edu/~russ/MSDS/urea.htm 
  ;

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