Ureas oxidation

Patzer, II IF., WoUson, Jr S. K. Yao, S. J. 1990. Reactor control and reaction kinetics for electrochemical urea oxidation. Chemical Engineering Science 45(8) 2777-2784. 

Amstutz et al. [16] compared indirect nitrogen oxidation in synthetic solutions representing fresh and stored urine. They used thermally prepared IrOa anodes. During electrolysis of fresh urine, 72 % of the nitrogen was removed, and 24 % was converted to nitrate. The current efficiency for urea oxidation was 70 %. However, in stored urine, only about 3 % of anmumia was removed, and 9 % was oxidized to nitrate. The researchers showed that the high carbmiate concentrations were responsible for the low ammonia oxidation in stored urine. They argued that carbonate oxidation prevented the formatiOTi of chlorine. 

This equation indicates that every molecule of urea requires 9/2 molecules of oxygen for complete oxidation. The oxygen required for the reactions depletes the receiving water of oxygen, causing the death of aquatic life. 

The alkylurea 576 and oxamide 577 are formed by oxidative carbonylation of amines under CO pressure using Pd/C as a catalyst[518]. The urea formation proceeds under atmospheric pressure using PdCh and CuCl2[519]. The mono-and double carbonylations of / -aminoethanol (578 and 579) afford the cyclic carbamate (oxazolidinones) 580 and oxamide (morpholinediones) 581 [520,521]. 

Phosphorus pentachloride Aluminum, chlorine, chlorine dioxide, chlorine trioxide, fluorine, magnesium oxide, nitrobenzene, diphosphorus trioxide, potassium, sodium, urea, water... 

Urea reacts with formaldehyde compounds such as monomethylolurea, NH2CONHCH2OH, dimethylolurea, HOCH2NHCONHCH2OH, and others, depending on the mol ratio of formaldehyde, to urea and upon the pH of the solution. Hydrogen peroxide and urea give a white crystalline powder, urea peroxide, CO(NH2 (2 -H2 02, known under the trade name of Hypersol, an oxidizing agent. 

Another modification of this process was reported in 1988 (84). In this process, a precondensate of THPC and urea, plus excess urea, are neutralized to a pH of about 5.7, and the buffer salt is added. The fabric is then given a standard pad-dry-cure process followed by oxidation and laundering. The principal advantage of this modification is a reduction in both formaldehyde vapors and phosphine-like odors released during processing (84). 

LRC-100Finish. The use of LRC-100 flame retardant for 50/50 polyester cotton blends has been reported (144). It is a condensation product of tetrakis(hydroxymethyl)-phosphonium salt (THP salt) and A/A7,A7 -trimethylphosphoramide [6326-72-3] (TMPA). The precondensate is prepared by heating the THP salt and TMPA in a 2.3-to-l.0-mole ratio for one hour at 60—65°C. It is appUed in conjunction with urea and trimethylolmelamine in a pad-dry-cure oxidation wash procedure. Phosphoms contents of 3.5—4.0% are needed to enable blends to pass the FF 3-71 Test. 

Phosphonium Salt—Urea Precondensate. A combination approach for producing flame-retardant cotton-synthetic blends has been developed based on the use of a phosphonium salt—urea precondensate (145). The precondensate is appUed to the blend fabric from aqueous solution. The fabric is dried, cured with ammonia gas, and then oxidized. This forms a flame-resistant polymer on and in the cotton fibers of the component. The synthetic component is then treated with either a cycUc phosphonate ester such as Antiblaze 19/ 19T, or hexabromocyclododecane. The result is a blended textile with good flame resistance. Another patent has appeared in which various modifications of the original process have been claimed (146). Although a few finishers have begun to use this process on blended textiles, it is too early to judge its impact on the industry. 

Hair straightening compositions based on mixtures of ammonium bisulfite [10192-30-0] and urea [57-13-6] have been introduced and have found some apphcation in the Caucasian hair market. The reformulation of the cystine cross-links in bisulfite-reduced hair is best accompHshed by a rinse, pH 8—10, rather than by the use of oxidizing agents (66). 

By fai the largest (ca 85% of the total) volume chemical blowing agent is azodicaibonamide (44), made by the oxidation of hydiazodicaiboxamide [110-21 -4] (51) using chlorine or sodium chlorate. The hydrazo precursor is made by refluxing an aqueous solution of urea and hydrazine (172) ... 

S. H. Timbedake, G. T. Hong, M. Simson, and M. ModeU, "Supercritical Water Oxidation for Wastewater Treatment Preliminary Study of Urea... 

Glucose [50-99-7] urea [57-13-6] (qv), and cholesterol [57-88-5] (see Steroids) are the substrates most frequentiy measured, although there are many more substrates or metaboUtes that are determined in clinical laboratories using enzymes. Co-enzymes such as adenosine triphosphate [56-65-5] (ATP) and nicotinamide adenine dinucleotide [53-84-9] in its oxidized (NAD" ) or reduced (NADH) [58-68-4] form can be considered substrates. Enzymatic analysis is covered in detail elsewhere (9). 

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