E927b (Carbamide) = UREA = UREA HYDROGEN PEROXIDE = CARBONYLDIAMIDE
CAS-Number : 57-13-6
EC-Number : 200-315-5
Molecular Formula: CH4N2O.H2O2 or CH6N2O3
E927b (Carbamide), also known as Urea, is an organic compound with chemical formula CO(NH2)2.
E927b (Carbamide) has two –NH2 groups joined by a carbonyl (C=O) functional group.
E927b (Carbamide) serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals.
E927b (Carbamide) is a colorless, odorless solid, highly soluble in water, and practically non-toxic.
Dissolved in water, E927b (Carbamide) is neither acidic nor alkaline.
The body uses E927b (Carbamide) in many processes, most notably nitrogen excretion.
The liver forms E927b (Carbamide) by combining two ammonia molecules (NH3) with a carbon dioxide (CO2) molecule in the urea cycle.
E927b (Carbamide) is widely used in fertilizers as a source of nitrogen (N) and is an important raw material for the chemical industry.
Friedrich Wöhler discovered that E927b (Carbamide) can be produced from inorganic starting materials, which was an important conceptual milestone in chemistry in 1828.
It showed for the first time that a substance previously known only as a byproduct of life could be synthesized in the laboratory without biological starting materials, thereby contradicting the widely held doctrine of vitalism, which stated that only living organisms could produce the chemicals of life.
E927b (Carbamide) is synthesized in the body of many organisms as part of the urea cycle, either from the oxidation of amino acids or from ammonia.
In this cycle, amino groups donated by ammonia and l-aspartate are converted to E927b (Carbamide), while l-ornithine, citrulline, l-argininosuccinate, and l-arginine act as intermediates.
E927b (Carbamide) production occurs in the liver and is regulated by N-acetylglutamate.
E927b (Carbamide) is then dissolved into the blood (in the reference range of 2.5 to 6.7 mmol/L) and further transported and excreted by the kidney as a component of urine.
In addition, a small amount of E927b (Carbamide) is excreted (along with sodium chloride and water) in sweat.
The cycling of and excretion of E927b (Carbamide) by the kidneys is a vital part of mammalian metabolism.
Besides E927b (Carbamide)'s role as carrier of waste nitrogen, urea also plays a role in the countercurrent exchange system of the nephrons, that allows for reabsorption of water and critical ions from the excreted urine.
E927b (Carbamide) is reabsorbed in the inner medullary collecting ducts of the nephrons, thus raising the osmolarity in the medullary interstitium surrounding the thin descending limb of the loop of Henle, which makes the water reabsorb.
E927b (Carbamide) is an amide compound with chemical formula (NH2)2CO.
E927b (Carbamide) plays an important role in mammals' metabolism and has various industrial applications.
The basic E927b (Carbamide) process is the so-called Bosch–Meiser developed in 1922, which consists of two main reactions:
The first reaction is fast exothermic and happens at high temperature and pressure to produce ammonium carbamate (H2N-COONH4).
This component is decomposed through a slow endothermic reaction in the second stage to form ammonia.
For producing one tonne of E927b (Carbamide), 0.735–0.750 t CO2 is consumed.
One of the key applications of E927b (Carbamide) is in fertilizers where E927b (Carbamide) reacts with water, releasing CO2 and ammonia to the soil.
Furthermore, the amount of CO2 emissions in the E927b (Carbamide) production process is 2.27 t of CO2-eq. per tonne of CO2 utilized.
Consequently, the concept of CO2 utilization in E927b (Carbamide) production is not recognized as a carbon reduction measure.
The analysis of coproduction of E927b (Carbamide) and power from coal was performed by Bose et al. using Aspen Plus.
The performance of the plant was evaluated based on the amount of CO2 utilized.
The results showed that the economic breakeven for CO2 utilization is below 5% and 10% for CO conversion efficiencies at 95% and 90%, respectively, within the water gas shift reactor.
Pérez-Fortes et al. modeled and evaluated E927b (Carbamide) production from industrial CO2.
They evaluated the process efficiency, the amount of utilized CO2, the utility requirements, and investment costs.
The amount of CO2 emissions was 0.6 t per tonne of CO2 utilized.
In aquatic organisms the most common form of nitrogen waste is ammonia, whereas land-dwelling organisms convert the toxic ammonia to either E927b (Carbamide) or uric acid.
E927b (Carbamide) is found in the urine of mammals and amphibians, as well as some fish.
Birds and saurian reptiles have a different form of nitrogen metabolism that requires less water, and leads to nitrogen excretion in the form of uric acid.
Tadpoles excrete ammonia, but shift to urea production during metamorphosis.
Despite the generalization above, the E927b (Carbamide) pathway has been documented not only in mammals and amphibians, but in many other organisms as well, including birds, invertebrates, insects, plants, yeast, fungi, and even microorganisms.
E927b (Carbamide) is readily quantified by a number of different methods, such as the diacetyl monoxime colorimetric method, and the Berthelot reaction (after initial conversion of E927b (Carbamide) to ammonia via urease).
These methods are amenable to high throughput instrumentation, such as automated flow injection analyzers and 96-well micro-plate spectrophotometers.
E927b (Carbamide) describes a class of chemical compounds that share the same functional group, a carbonyl group attached to two organic amine residues:
Examples include E927b (Carbamide) peroxide, allantoin, and hydantoin.
Ureas are closely related to biurets and related in structure to amides, carbamates, carbodiimides, and thioE927b (Carbamide)s.
The E927b (Carbamide) molecule is planar.
In solid E927b (Carbamide), 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 E927b (Carbamide) is described as sp2 hybridized, the C-N bonds have significant double bond character, and the carbonyl oxygen is basic compared to, say, formaldehyde.
E927b (Carbamide)'s high aqueous solubility reflects E927b (Carbamide)'s ability to engage in extensive hydrogen bonding with water.
By virtue of its tendency to form porous frameworks, urea has the ability to trap many organic compounds.
In these so-called clathrates, the organic "guest" molecules are held in channels formed by interpenetrating helices composed of hydrogen-bonded E927b (Carbamide) molecules.
This behaviour can be used to separate mixtures, e.g., in the production of aviation fuel and lubricating oils, and in the separation of hydrocarbons.
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.
E927b (Carbamide), also known as Urea, is a safe, useful compound with a significant history.
E927b (Carbamide) is a naturally occurring molecule that is produced by protein metabolism and found abundantly in mammalian urine.
In 1828, the German chemist Friedrich Wöhler, then at the Polytechnic School (now Technical University) of Berlin, published a seminal article in which he demonstrated that a biomolecule, E927b (Carbamide), can be synthesized from a nonbiological starting material.
Wöhler prepared the inorganic compound ammonium cyanate in the lab, then heated it, causing it to isomerize to E927b (Carbamide).
Now known as the “Wöhler synthesis”, the reaction helped to disprove the concept of vitalism, which held that “organic” molecules can be made only by living organisms.
In a reaction similar to the Wöhler synthesis, ammonium carbamate can be converted to E927b (Carbamide) and water.
This is the basis of the process that has been used to produce E927b (Carbamide) industrially for almost a century.
Ammonia and carbon dioxide (CO2) react exothermically to produce the carbamate salt, which is then heated to form urea.
The heat produced in the first reaction drives the second.
Typically, ammonia and E927b (Carbamide) are manufactured in the same plant so that some of the carbon dioxide byproduct from ammonia production can be used to make E927b (Carbamide).
Global E927b (Carbamide) production capacity is ≈220 million t/year.
Why is E927b (Carbamide) produced in such large quantities?
The answer is that, other than ammonia, E927b (Carbamide) has the highest nitrogen content of all industrial chemicals and is in high demand as a fertilizer.
In the soil, E927b (Carbamide) decomposes back to ammonia (actually ammonium ion) and carbon dioxide.
Nitrogen-fixing bacteria oxidize ammonium to nitrate, which is readily taken up by the roots of crops.
In addition to its high nitrogen content, E927b (Carbamide) is particularly useful because E927b (Carbamide) can be applied as a solid in pellet form; and E927b (Carbamide)'s unusually high solubility in water allows E927b (Carbamide) to be incorporated into solutions with other plant nutrients.
E927b (Carbamide), also called Urea, the diamide of carbonic acid.
E927b (Carbamide)'s formula is H2NCONH2.
E927b (Carbamide) is the chief nitrogenous end product of the metabolic breakdown of proteins in all mammals and some fishes.
E927b (Carbamide) 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 E927b (Carbamide) by the liver.
E927b (Carbamide) then passes to the kidneys and is eventually excreted in the urine.
E927b (Carbamide) is a colourless, crystalline substance that melts at 132.7° C (271° F) and decomposes before boiling.
E927b (Carbamide) was first isolated from urine in 1773 by the French chemist Hilaire-Marin Rouelle.
E927b (Carbamide)'s preparation by the German chemist Friedrich Wöhler from ammonium cyanate in 1828 was the first generally accepted laboratory synthesis of a naturally occurring organic compound from inorganic materials.
E927b (Carbamide) is now prepared commercially in vast amounts from liquid ammonia and liquid carbon dioxide.
These two materials are combined under high pressures and elevated temperatures to form ammonium carbamate, which then decomposes at much lower pressures to yield E927b (Carbamide) and water.
Because E927b (Carbamide)'s nitrogen content is high and is readily converted to ammonia in the soil, E927b (Carbamide) is one of the most concentrated nitrogenous fertilizers.
E927b (Carbamide) is an organic compound commonly known as urea, the primary byproduct of nitrogen metabolism in mammals and amphibians.
E927b (Carbamide) is characterized as a water-soluble, colorless, and odorless granular substance in E927b (Carbamide)'s pure state, but in the presence of moisture, E927b (Carbamide) will give off a slight ammonia smell.
Synthesized from ammonia and carbon dioxide in the liver, E927b (Carbamide) travels to the kidneys via the blood, where E927b (Carbamide) is excreted in urine.
This compound can also be made artificially from inorganic materials.
Friedrich Wöhler was the first to make this discovery when he accidentally created E927b (Carbamide) from potassium cyanate and ammonium sulfate in 1828.
Although Wöhler had intended to synthesize ammonium cyanate and not E927b (Carbamide), his discovery nonetheless proved invaluable.
Prior to this event, the scientific community held that the biochemistry of living things differed from non-organic matter and could not be duplicated.
Known as the principle of vitalism, this concept stemmed from the belief that non-living things lacked the vital force, or the unknown element that sparks life.
In effect, Wöhler contributed to setting this theory aside and paved the way for the study of organic chemistry.
E927b (Carbamide) is a diamide of carbonic acid since E927b (Carbamide) contains two amide groups.
In addition, E927b (Carbamide)'s synthesis is completed through an anabolic process, which requires the utilization of small molecules from other agents.
In this case, carbon dioxide, aspartate, ammonia, and water provide the metabolic pathway.
This process, known as the urea (E927b (Carbamide)) cycle, is vital to the elimination of ammonia, which would otherwise accumulate in toxic amounts.
Since this substance is inexpensively produced from synthetic ammonia and carbon dioxide, E927b (Carbamide) is manufactured on a wide scale for a variety of commercial uses.
Being a rich source of nitrogen, the majority is made for the fertilizer industry.
E927b (Carbamide) is also highly water-soluble due to its ability to form multiple hydrogen bonds.
Once applied to soil, E927b (Carbamide) quickly reverts into ammonia and carbon dioxide through hydrolysis.
USES and APPLICATIONS of E927b (Carbamide):
More than 90% of world industrial production of E927b (Carbamide) is destined for use as a nitrogen-release fertilizer.
E927b (Carbamide) has the highest nitrogen content of all solid nitrogenous fertilizers in common use.
Therefore, E927b (Carbamide) has a low transportation cost per unit of nitrogen nutrient.
E927b (Carbamide) breaks down in the soil to give ammonium.
The ammonium is taken up by the plant.
In some soils, the ammonium is oxidized by bacteria to give nitrate, which is also a plant nutrient.
E927b (Carbamide) is sometimes pretreated or modified to enhance the efficiency of E927b (Carbamide)'s agricultural use.
One such technology is controlled-release fertilizers, which contain urea encapsulated in an inert sealant.
Another technology is the conversion of E927b (Carbamide) into derivatives, such as formaldehyde, which degrades into ammonia at a pace matching plants' nutritional requirements.
E927b (Carbamide) is a raw material for the manufacture of two main classes of materials:
E927b (Carbamide)-formaldehyde resins and E927b (Carbamide)-melamine-formaldehyde used in marine plywood.
E927b (Carbamide) can be used to make urea nitrate, a high explosive that is used industrially and as part of some improvised explosive devices.
-E927b (Carbamide) has important uses as a fertilizer and feed supplement, as well as a starting material for the manufacture of plastics and drugs.
E927b (Carbamide) is used in Selective Non-Catalytic Reduction (SNCR) and Selective Catalytic Reduction (SCR) reactions to reduce the
NOx pollutants in exhaust gases from combustion from diesel, dual fuel, and lean-burn natural gas engines.
The BlueTec system, for example, injects a water-based E927b (Carbamide) solution into the exhaust system.
Ammonia (NH3) first produced by the hydrolysis of E927b (Carbamide) reacts with nitrogen oxides (NOx) and is converted into nitrogen gas (N2) and water within the catalytic converter.
The conversion of noxious NOx to innocuous N2 is described by the following simplified global equation:
4 NO + 4 NH3 + O2 → 4 N2 + 6 H2O
When E927b (Carbamide) is used, a pre-reaction (hydrolysis) occurs to first convert it to ammonia:
NH2CONH2 + H2O → 2 NH3 + CO2
Being a solid highly soluble in water (545 g/L at 25 °C), E927b (Carbamide) is much easier and safer to handle and store than the more irritant, caustic and hazardous ammonia (NH3), so E927b (Carbamide) is the reactant of choice.
Trucks and cars using these catalytic converters need to carry a supply of diesel exhaust fluid, also sold as AdBlue, a solution of E927b (Carbamide) in water.
E927b (Carbamide)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 E927b (Carbamide) and choline chloride is used as a deep eutectic solvent (DES), a substance similar to ionic liquid.
When used in a deep eutectic solvent, E927b (Carbamide) gradually denatures the proteins that are solubilized.
-E927b (Carbamide) can in principle serve as a hydrogen source for subsequent power generation in fuel cells.
E927b (Carbamide) present in urine/wastewater can be used directly (though bacteria normally quickly degrade E927b (Carbamide)).
Producing hydrogen by electrolysis of E927b (Carbamide) solution occurs at a lower voltage (0.37 V) and thus consumes less energy than the electrolysis of water (1.2 V).
-E927b (Carbamide) 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.
E927b (Carbamide)-containing creams are used as topical dermatological products to promote rehydration of the skin.
E927b (Carbamide) 40% is indicated for psoriasis, xerosis, onychomycosis, ichthyosis, eczema, keratosis, keratoderma, corns, and calluses.
If covered by an occlusive dressing, 40% E927b (Carbamide) preparations may also be used for nonsurgical debridement of nails.
E927b (Carbamide) 40% "dissolves the intercellular matrix" of the nail plate.
Only diseased or dystrophic nails are removed, as there is no effect on healthy portions of the nail.
This drug (as E927b (Carbamide) peroxide) is also used as an earwax removal aid.
-More than 90% of urea production goes into agriculture.
The remaining ≈20 million made annually goes into animal feed (cattle, among others, can convert E927b (Carbamide) into protein), E927b (Carbamide)–formaldehyde resins, emollients for skin care, and barbituric acid manufacture.
-E927b (Carbamide)’s strongly negative heat of solution in water is the basis of instant-cold packs, in which plastic pouches contain E927b (Carbamide) and water in separate compartments.
-When the seal between them is broken, intermixing produces short-term cooling for aching joints and muscles.
-E927b (Carbamide) is an antiseptic and deodorizing component.
E927b (Carbamide) is included to the composition of creams and lotions as the moisturizing component.
-E927b (Carbamide) is used for the dry, sensitive skin.
-E927b (Carbamide) has also been studied as a diuretic.
E927b (Carbamide) was first used by Dr. W. Friedrich in 1892.
In a 2010 study of ICU patients, E927b (Carbamide) was used to treat euvolemic hyponatremia and was found safe, inexpensive, and simple.
-The blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood that comes from E927b (Carbamide).
E927b (Carbamide) is used as a marker of renal function, though E927b (Carbamide) is inferior to other markers such as creatinine because blood E927b (Carbamide) levels are influenced by other factors such as diet, dehydration, and liver function.
-E927b (Carbamide) has also been studied as an excipient in Drug-coated Balloon (DCB) coating formulation to enhance local drug delivery to stenotic blood vessels.
E927b (Carbamide), when used as an excipient in small doses (~3 μg/mm2) to coat DCB surface was found to form crystals that increase drug transfer without adverse toxic effects on vascular endothelial cells.
-E927b (Carbamide) labeled with carbon-14 or carbon-13 is used in the E927b (Carbamide) breath test, which is used to detect the presence of the bacterium Helicobacter pylori (H. pylori) in the stomach and duodenum of humans, associated with peptic ulcers.
The test detects the characteristic enzyme urease, produced by H. pylori, by a reaction that produces ammonia from urea.
-An ingredient in diesel exhaust fluid (DEF), which is 32.5% E927b (Carbamide) and 67.5% de-ionized water.
DEF is sprayed into the exhaust stream of diesel vehicles to break down dangerous NOx emissions into harmless nitrogen and water.
-A component of animal feed, providing a relatively cheap source of nitrogen to promote growth
-E927b (Carbamide) hydrogen peroxide appears as a solid or paste-like semisolid.
-A non-corroding alternative to rock salt for road de-icing.
E927b (Carbamide) is often the main ingredient of pet friendly salt substitutes although E927b (Carbamide) is less effective than traditional rock salt or calcium chloride.
-Used to make plastics.
-A main ingredient in hair removers such as Nair and Veet
-A browning agent in factory-produced pretzels
-Used An ingredient in some skin cream, moisturizers, hair conditioners, and shampoos
-Used A cloud seeding agent, along with other salts.
-Used A flame-proofing agent, commonly used in dry chemical fire extinguisher charges such as the E927b (Carbamide)-potassium bicarbonate mixture
-Used as a diuretic agent.
-Used An ingredient in many tooth whitening products
-Used An ingredient in dish soap
-Along with diammonium phosphate, as a yeast nutrient, for fermentation of sugars into ethanol
-A nutrient, E927b (Carbamide), used by plankton in ocean nourishment experiments for geoengineering purposes
-Used as an additive to extend the working temperature and open time of hide glue
-Used as a solubility-enhancing and moisture-retaining additive to dye baths for textile dyeing or printing.
-Used as an optical parametric oscillator in nonlinear optics.
E927b (Carbamide) can be produced as prills, granules, pellets, crystals, and solutions.
For E927b (Carbamide)'s main use as a fertilizer E927b (Carbamide) is mostly marketed in solid form, either as prills or granules.
The advantage of prills is that, in general, they can be produced more cheaply than granules and that the technique was firmly established in industrial practice long before a satisfactory urea granulation process was commercialized.
However, on account of the limited size of particles that can be produced with the desired degree of sphericity and their low crushing and impact strength, the performance of prills during bulk storage, handling and use is generally considered inferior to that of granules.
High-quality compound fertilizers containing nitrogen co-granulated with other components such as phosphates have been produced routinely since the beginnings of the modern fertilizer industry, but on account of the low melting point and hygroscopic nature of E927b (Carbamide) it took courage to apply the same kind of technology to granulate E927b (Carbamide) on its own.
But at the end of the 1970s three companies began to develop fluidized-bed granulation.
-Widely used in fertilizers as a source of nitrogen and is an important raw material for the chemical industry.
-With formaldehyde E927b (Carbamide) gives methylene–urea fertilizers, which release nitrogen slowly, continuously, and uniformly, a full year’s supply being applied at one time.
-Although E927b (Carbamide) nitrogen is in nonprotein form, it can be utilized by ruminant animals (cattle, sheep), and a significant part of these animals’ protein requirements can be met in this way.
-The use of E927b (Carbamide) to make urea–formaldehyde resin is second in importance only to E927b (Carbamide)'s use as a fertilizer.
-E927b (Carbamide) reacts with alcohols to form urethanes and with malonic esters to give barbituric acids.
With certain straight-chain aliphatic hydrocarbons and their derivatives, E927b (Carbamide) forms crystalline inclusion compounds, which are useful for purifying the included substances.
-E927b (Carbamide) is an organic compound with the chemical formula (NH2)2CO extensively used in proteomics and molecular biology.
-E927b (Carbamide) has several other applications.
In veterinary medicine, for instance, E927b (Carbamide) is used as a topical antiseptic and a diuretic.
-Large amounts of E927b (Carbamide) are also used for the synthesis of barbiturates.
-E927b (Carbamide) is also sometimes used to enhance the protein content of cattle and sheep feed.
-In manufacturing, E927b (Carbamide) is used to make urea-formaldehyde plastics and E927b (Carbamide) resin as an adhesive for laminated plywood and particleboard.
-Used a potent emollient and keratolytic agent.
-E927b (Carbamide) is also used to stabilize explosives and, when combined with barium hydroxide, to deter the effects of acid rain when applied to limestone monuments.
-Blood Urea nitrogen (BUN) has been utilized to evaluate renal function.
-E927b (Carbamide) was once used as a flame retardant for clothing and to induce the glycation process needed for commercial baked goods to brown.
-E927b (Carbamide)'s known by several trade names, including isourea, carbonyl diamide, and carbonyldiamine.
-An inexpensive compound, E927b (Carbamide) is incorporated in mixed fertilizers as well as being applied alone to the soil or sprayed on foliage.
-E927b (Carbamide) is a powerful protein denaturant via both direct and indirect mechanisms.
REACTIONS of E927b (Carbamide):
E927b (Carbamide) is basic.
As such E927b (Carbamide) is protonates readily.
E927b (Carbamide) is also a Lewis base forming complexes of the type [M(urea)6]n+.
Molten E927b (Carbamide) decomposes into ammonia gas and isocyanic acid:
(H2N)2CO → NH3 + HNCO
Via isocyanic acid, heating E927b (Carbamide) converts to a range of condensation products including biuret, triuret, guanidine, and melamine:
(H2N)2CO + HNCO → H2NCONHCONH2
In aqueous solution, E927b (Carbamide) slowly equilibrates with ammonium cyanate.
This hydrolysis cogenerates isocyanic acid, which can carbamylate proteins.
E927b (Carbamide) reacts with malonic esters to make barbituric acids.
E927b (Carbamide) formed by the breakdown of protein in the liver.
The kidneys filter E927b (Carbamide) out of the blood and into the urine.
E927b (Carbamide) can also be made in the laboratory.
A topical form of E927b (Carbamide) is being studied in the treatment of hand-foot syndrome (pain, swelling, numbness, tingling, or redness of the hands or feet that may occur as a side effect of certain anticancer drugs).
Also called E927b (Carbamide).
E927b (Carbamide)s in the more general sense can be accessed in the laboratory by reaction of phosgene with primary or secondary amines:
COCl2 + 4 RNH2 → (RNH)2CO + 2 [RNH3]Cl
These reactions proceed through an isocyanate intermediate.
Non-symmetric E927b (Carbamide)s can be accessed by the reaction of primary or secondary amines with an isocyanate.
E927b (Carbamide) can also be produced by heating ammonium cyanate to 60 °C.
[NH4][OCN] → (NH2)2CO
PRODUCTİON of CARBAMIIDE:
E927b (Carbamide) is produced on an industrial scale:
In 2012, worldwide production capacity was approximately 184 million tonnes.
For use in industry, E927b (Carbamide) 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 (water shift reaction), E927b (Carbamide) production plants are almost always located adjacent to the site where the ammonia is manufactured.
Although natural gas is both the most economical and the most widely available ammonia plant feedstock, plants using E927b (Carbamide) do not produce quite as much carbon dioxide from the process as is needed to convert their entire ammonia output into urea.
In recent years new technologies such as the KM-CDR process have been developed to recover supplementary carbon dioxide from the combustion exhaust gases produced in the fired reforming furnace of the ammonia synthesis gas plant, allowing operators of stand-alone nitrogen fertilizer complexes to avoid the need to handle and market ammonia as a separate product and also to reduce their greenhouse gas emissions to the atmosphere.
The basic process, developed in 1922, is also called the Bosch–Meiser E927b (Carbamide) process after its discoverers.
Various commercial urea processes are characterized by the conditions under which E927b (Carbamide) forms and the way that unconverted reactants are further processed.
The process consists of two main equilibrium reactions, with incomplete conversion of the reactants.
The first is carbamate formation: the fast exothermic reaction of liquid ammonia with gaseous carbon dioxide (CO2) at high temperature and pressure to form ammonium carbamate ([H2N−CO2][NH4]):
2 NH3 + CO2 ⇌ [H2N−CO2][NH4]
(ΔH = −117 kJ/mol at 110 atm and 160 °C)
The second is E927b (Carbamide) conversion: the slower endothermic decomposition of ammonium carbamate into E927b (Carbamide) and water:
[H2N−CO2][NH4] ⇌ (NH2)2CO + H2O (ΔH = +15.5 kJ/mol at 160–180 °C)
The overall conversion of NH3 and CO2 to E927b (Carbamide) is exothermic, the reaction heat from the first reaction driving the second.
Like all chemical equilibria, these reactions behave according to Le Chatelier's principle, and the conditions that most favour carbamate formation have an unfavourable effect on the E927b (Carbamide) conversion equilibrium.
The process conditions are, therefore, a compromise: the ill-effect on the first reaction of the high temperature (around 190 °C) needed for the second is compensated for by conducting the process under high pressure (140–175 bar), which favours the first reaction.
Although it is necessary to compress gaseous carbon dioxide to this pressure, the ammonia is available from the ammonia plant in liquid form, which can be pumped into the system much more economically.
To allow the slow E927b (Carbamide) formation reaction time to reach equilibrium a large reaction space is needed, so the synthesis reactor in a large E927b (Carbamide) plant tends to be a massive pressure vessel.
Because the E927b (Carbamide) conversion is incomplete, the product must be separated from unchanged ammonium carbamate.
In early "straight-through" E927b (Carbamide) plants this was done by letting down the system pressure to atmospheric to let the carbamate decompose back to ammonia and carbon dioxide.
Originally, because it was not economic to recompress the ammonia and carbon dioxide for recycle, the ammonia at least would be used for the manufacture of other products, for example ammonium nitrate or sulfate.
(The carbon dioxide was usually wasted.)
Later process schemes made recycling unused ammonia and carbon dioxide practical.
This was accomplished by depressurizing the reaction solution in stages (first to 18 – 25 bar and then to 2 – 5 bar) and passing it at each stage through a steam-heated carbamate decomposer, then recombining the resultant carbon dioxide and ammonia in a falling-film carbamate condenser and pumping the carbamate solution into the previous stage.
The "total recycle" concept has two main disadvantages.
The first is the complexity of the flow scheme and, consequently, the amount of process equipment needed.
The second is the amount of water recycled in the carbamate solution, which has an adverse effect on the equilibrium in the E927b (Carbamide) conversion reaction and thus on overall plant efficiency.
The stripping concept, developed in the early 1960s by Stamicarbon in The Netherlands, addressed both problems.
It also improved heat recovery and reuse in the process.
The position of the equilibrium in the carbamate formation/decomposition depends on the product of the partial pressures of the reactants.
In the total recycle processes, carbamate decomposition is promoted by reducing the overall pressure, which reduces the partial pressure of both ammonia and carbon dioxide.
It is possible, however, to achieve a similar effect without lowering the overall pressure—by suppressing the partial pressure of just one of the reactants.
Instead of feeding carbon dioxide gas directly to the reactor with the ammonia, as in the total recycle process, the stripping process first routes the carbon dioxide through a stripper
(a carbamate decomposer that operates under full system pressure and is configured to provide maximum gas-liquid contact).
This flushes out free ammonia, reducing its partial pressure over the liquid surface and carrying it directly to a carbamate condenser (also under full system pressure).
From there, reconstituted ammonium carbamate liquor passes directly to the reactor.
That eliminates the medium-pressure stage of the total recycle process altogether.
The stripping concept was such a major advance that competitors such as Snamprogetti — now Saipem — (Italy), the former Montedison (Italy), Toyo Engineering Corporation (Japan), and Urea Casale (Switzerland) all developed versions of it.
Today, effectively all new urea plants use the principle, and many total recycle urea plants have converted to a stripping process.
No one has proposed a radical alternative to the approach.
The main thrust of technological development today, in response to industry demands for ever larger individual plants, is directed at re-configuring and re-orientating major items in the plant to reduce size and overall height of the plant, and at meeting challenging environmental performance targets.
It is fortunate that the E927b (Carbamide) conversion reaction is slow.
If it were not it would go into reverse in the stripper.
As it is, succeeding stages of the process must be designed to minimize residence times, at least until the temperature reduces to the point where the reversion reaction is very slow.
Two reactions produce impurities.
Biuret is formed when two molecules of E927b (Carbamide) combine with the loss of a molecule of ammonia.
2 NH2CONH2 → H2NCONHCONH2 + NH3
Normally this reaction is suppressed in the synthesis reactor by maintaining an excess of ammonia, but after the stripper, it occurs until the temperature is reduced.
Isocyanic acid results from the thermal decomposition of ammonium cyanate, which is in chemical equilibrium with urea:
NH2CONH2 → [NH4][NCO] → HNCO + NH3
This reaction is at its worst when the urea solution is heated at low pressure, which happens when the solution is concentrated for prilling or granulation.
HISTORY of E927b (Carbamide):
E927b (Carbamide) was first discovered in urine in 1727 by the Dutch scientist Herman Boerhaave, although this discovery is often attributed to the French chemist Hilaire Rouelle as well as William Cruickshank.
Boerhaave used the following steps to isolate E927b (Carbamide):
*Boiled off water, resulting in a substance similar to fresh cream
*Used filter paper to squeeze out remaining liquid
*Waited a year for solid to form under an oily liquid
*Removed the oily liquid
*Dissolved the solid in water
*Used recrystallization to tease out the E927b (Carbamide)
In 1828, the German chemist Friedrich Wöhler obtained E927b (Carbamide) artificially by treating silver cyanate with ammonium chloride.
AgNCO + NH4Cl → (NH2)2CO + AgCl
This was the first time an organic compound was artificially synthesized from inorganic starting materials, without the involvement of living organisms.
The results of this experiment implicitly discredited vitalism — the theory that the chemicals of living organisms are fundamentally different from those of inanimate matter.
This insight was important for the development of organic chemistry.
His discovery prompted Wöhler to write triumphantly to Berzelius: "I must tell you that I can make E927b (Carbamide) without the use of kidneys, either man or dog. Ammonium cyanate is E927b (Carbamide)." In fact, this was incorrect.
These are two different chemicals with the same overall chemical formula N2H4CO, which are in chemical equilibrium heavily favoring urea under standard conditions.
Regardless, with his discovery, Wöhler secured a place among the pioneers of organic chemistry.
E927b (Carbamide) was first noticed by Herman Boerhaave in the early 18th century from evaporates of urine.
In 1773, Hilaire Rouelle obtained crystals containing E927b (Carbamide) 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 "E927b (Carbamide)".
Berzelius made further improvements to its purification and finally William Prout, in 1817, succeeded in obtaining and determining the chemical composition of the pure substance.
In the evolved procedure, E927b (Carbamide) 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 E927b (Carbamide) nitrate form.
To reconstitute the E927b (Carbamide) 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 E927b (Carbamide).
This solution is drained off and evaporated, leaving pure E927b (Carbamide).
PHYSICAL and CHEMICAL PROPERTIES of E927b (Carbamide):
Molecular weight : 60,06 g/mol
Appearance Form: powder
Odor Threshold: Not applicable
pH: 7,5 - 9,5 at 480 g/l at 25 °C
Melting point/freezing point:
Melting point/range: 132 - 135 °C
Initial boiling point and boiling range: Decomposes below the boiling point.
Flash point: Not applicable
Evaporation rate: No data available
Flammability (solid, gas): No data available
Upper/lower flammability or explosive limits: No data available
Vapor pressure: < 0,1 hPa at 25 °C
Vapor density: No data available
Relative density: 1,33 at 20 °C
Water solubility: 624 g/l at 20 °C completely soluble:
Partition coefficient: n-octanol/water
log Pow: < -1,73 at 22 °C - Regulation (EC) No. 440/2008,
Autoignition temperature: > 134 °C
Decomposition temperature: No data available
Viscosity, kinematic: No data available
Viscosity, dynamic: No data available
Explosive properties: No data available
Oxidizing properties: No data available
Other safety information:
Dissociation constant: < 0,6
Molecular Weight: 94.07
Hydrogen Bond Donor Count: 4
Hydrogen Bond Acceptor Count: 3
Rotatable Bond Count: 0
Exact Mass: 94.03784206
Monoisotopic Mass: 94.03784206
Topological Polar Surface Area: 110 Å²
Heavy Atom Count: 6
Formal Charge: 0
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 2
Compound Is Canonicalized: Yes
Formulated from analytical grade reagent.
Choice of two concentrations.
Reproducibility from lot to lot.
Exactly pre-weighted in pouches.
Dissolve and use in minutes.
Chemicals: Analytical grade.
Format: Exactly pre-weighed powder.
Volume: 100 ml.
Three years after production date.
FIRST AID MEASURES of E927b (Carbamide):
-Description of first-aid measures
*In case of skin contact:
Take off immediately all contaminated clothing.
Rinse skin withwater/ shower.
*In case of eye contact:
After eye contact:
Rinse out with plenty of water.
Remove contact lenses.
Make victim drink water (two glasses at most).
Consult doctor if feeling unwell.
-Indication of any immediate medical attention and special treatment needed:
No data available
ACCIDENTAL RELEASE MEASURES of E927b (Carbamide):
Do not let product enter drains.
-Methods and materials for containment and cleaning up:
Collect, bind, and pump off spills.
Take up dry.
Dispose of properly.
Clean up affected area.
FIRE FIGHTING MEASURES of E927b (Carbamide):
*Suitable extinguishing media:
Carbon dioxide (CO2)
*Unsuitable extinguishing media:
For this substance/mixture no limitations of extinguishing agents are given.
Suppress (knock down) gases/vapors/mists with a water spray jet.
Prevent fire extinguishing water from contaminating surface water or the ground water system.
EXPOSURE CONTROLS/PERSONAL PROTECTION of E927b (Carbamide):
--Ingredients with workplace control parameters:
--Personal protective equipment:
Use Safety glasses.
Material: Nitrile rubber
Minimum layer thickness: 0,11 mm
Break through time: 480 min
Material: Nitrile rubber
Minimum layer thickness: 0,11 mm
Break through time: 480 min
-Control of environmental exposure:
Do not let product enter drains.
HANDLING and STORAGE of E927b (Carbamide):
-Conditions for safe storage, including any incompatibilities:
STABILITY and REACTIVITY of E927b (Carbamide):
The product is chemically stable under standard ambient conditions (room temperature).
-Conditions to avoid:
no information available
Urea hydrogen peroxide
E927b (Carbamide) PEROXIDE
Hydrogen peroxide E927b (Carbamide)
Hydrogen peroxide urea
Urea compound with hydrogen peroxide (1:1)
E927b (Carbamide) peroxide, solution
Urea hydrogen peroxide adduct
Hydrogen peroxide-Urea adduct
E927b (Carbamide) peroxide [USP]
Urea, compd. with hydrogen peroxide (H2O2) (1:1)
Urea, compd. with hydrogen peroxide (1:1)
E927b (Carbamide) peroxide (USP)
Murine Ear Drops
hydrogen peroxide; urea
Ear Wax Treatment
Auro Ear Wax Remover
per E927b (Carbamide)
Hydrogen peroxide, compd. with urea (1:1)
E927b (Carbamide) Peroxide Otic Solution
Murine ear drops (TN)
WLN: ZVZ & QQ
hydrogen peroxide urea adduct
Urea hydrogen peroxide, 97%
hydrogen peroxide - urea (1:1)
Urea, compd. with peroxide (1:)
Urea compound with hydrogen peroxide
Hydrogen peroxide-Urea adduct, tablet
Hydrogen Peroxide Urea
Hydrogen peroxide-urea compound (1:1)
(H2 N)2 C O (H2 O2)
Hydrogen peroxide, compd. with urea(1:1)
Urea, compd. with hydrogen peroxide(1:1)
Urea hydrogen peroxide
Hydrogen peroxide-Urea adduct, USP, 96.0-102.0%
Hydrogen peroxide-Urea adduct, powder, 15-17% active oxygen basis
Hydrogen peroxide-Urea adduct, purum p.a., "rapid-soluble", tablet (1 g each)