Ammonia regenerating

If polyribonucleotides are treated simultaneously with methoxylamine and bisulphite, cytidine residues are converted into 5,6-dihydro-7V4-methoxycytidine-6-sulphonate,154 and uridine into 5,6-dihydrouridine-6-sulphonate.155 Treatment with dilute ammonia regenerates the uridine residues, leaving the dihydrocytidine derivatives unaffected. When only the cytidine residues have been derivatized, pancreatic ribonuclease becomes uridyl ribonuclease, since it is unable to cleave the chain on the 3 -side of the modified cytidine.154 This allows the isolation of blocks of modified cytidine residues. T2 ribonuclease may also be used. Alternatively, a ribonuclease from Physarum polycephalum has been found to hydrolyse CpX links very slowly, allowing the isolation of cytidine blocks.156 If both uridine and cytidine residues are modified, T2 ribonuclease acts as puryl ribonuclease, allowing the isolation of cumulative blocks of pyrimidines.155 This ability to alter the specificity of nuclease cleavage is a useful tool in sequence analysis. 

The unsubstituted oxadiazole has been prepared from formamide and formamidoxime in glycol diformate used as solvent. By reacting with the solvent, ammonia regenerates formamide. The reaction takes place as follows ... 

The purest caustic solution is obtained by extraction with ammonia. The initial 50 per cent caustic solution is led to the top of an extraction tower and flows countercurrently to a mixture of 75 per cent ammonia and 25 per cent water which rises from below. The two solutions are immiscible. The ammonia solution extracts almost completely the chloride and sodium chlorate from the caustic liquor so as to leave no more than 0.08 per cent NaCl (related to 100 per cent NaOH) and practically no chlorate. Ammonia regeneration equipment complements the extraction unit. If anhydrous liquid ammonia is used instead of an ammonia solution a certain degree of concentration of the caustic solution can be achieved at the same time as ammonia also extracts water from the caustic solution. 

Ammonium peroxides.—At —10° C. dry ammonia reacts with a solution of 98 per cent, hydrogen peroxide in absolute ether to form a crystalline precipitate of the formula NH OaH or (NH4)202)H202. It melts at 14° C., and is converted by the prolonged action of ammonia into an oil, (NH4)202, which solidifies at —40° C., begins to decompose about —10° C., and melts at —2° C. It readily loses ammonia, regenerating the parent substance, NB C H.1 A crystalline, hydrated form of the composition (NH4)2O2,2H2O2,]0H2O, has been prepared. Potassium hydroxide decomposes it, with formation of ammonia and potassium peroxide. 

At the start of an operation, water or ammonium sulfite solution can be used as the scrubbing liquid. If water is used, primary ammonia and steam must be injected to the gas and the scrubbing operation must continue for several hours prior to regeneration of any ammonia. This builds up a salt solution. If a sulfite solution is used (3.0% ), ammonia regeneration can begin immediately. 

At any given flow rate of scrubber solution to the regenerator, the volume of ammonia regenerated appears to vary directly with solution pH, salt concentration, and regenerator temperature (up to about 220°F). 

Benzo[c]cinnoline is a weak base with a of 2.2 in water and 1.6 in 50% aqueous ethanol.Cryoscopic measurements show that it is dipro-tonated to some extent in 100% sulfuric acid. Well-defined quaternary salts result from heating benzo[c]cinnoline with alkyl halides and sul-fates. These are reported to decompose on treatment with ammonia, regenerating benzo[c]cinnoline, but apparently nucleophilic displacements of halogen by amines have been carried out on certain highly substituted examples in the synthesis of cationic dyestuffs. Quaternizations of benzo[c]cinnoline with a,a)-dibromo-propane and -butane are accompanied by hydrogen bromide elimination to give the cyclic iminium salts 40 and 41. When 40 is dehydrogenated, or merely refluxed in ethanol. 

An older route is based on just toluene and ammonia in the absence of air with separate catalyst regeneration (77). 

Boron trifluoride catalyst may be recovered by distillation, chemical reactions, or a combination of these methods. Ammonia or amines are frequently added to the spent catalyst to form stable coordination compounds that can be separated from the reaction products. Subsequent treatment with sulfuric acid releases boron trifluoride. An organic compound may be added that forms an adduct more stable than that formed by the desired product and boron trifluoride. In another procedure, a fluoride is added to the reaction products to precipitate the boron trifluoride which is then released by heating. Selective solvents may also be employed in recovery procedures (see Catalysts,regeneration). 

Sodium bicarbonate may be prepared by the ammonia-salt (Solvay) process. Carbon dioxide is passed through a solution of sodium chloride in ammonia water. Sodium bicarbonate is precipitated and the ammonium chloride remains in solution. The ammonium chloride is heated with lime to regenerate ammonia (see Alkali AND CHLORINE PRODUCTS). 

The mechanism of this reaction involves an activation of the ammonia and hydrogen peroxide because these compounds do not themselves react (118—121). It appears that acetamide functions as an oxygen transfer agent, possibly as the iminoperacetic acid (41) which then oxidizes the transient Schiff base formed between MEK and ammonia (40) to give the oxaziridine (42), with regeneration of acetamide ... 

Ammonium Ion Removal. A fixed-bed molecular-sieve ion-exchange process has been commercialized for the removal of ammonium ions from secondary wastewater treatment effluents. This application takes advantage of the superior selectivity of molecular-sieve ion exchangers for ammonium ions. The first plants employed clinoptilolite as a potentially low cost material because of its availability in natural deposits. The bed is regenerated with a lime-salt solution that can be reused after the ammonia is removed by pH adjustment and air stripping. The ammonia is subsequentiy removed from the air stream by acid scmbbing. 

Lauramide has been prepared by passing ammonia gas through lauric acid in the presence of metallic oxides, specifically a complex mixture of Si02—AI2O2—Fe202—CaO—SO in the ratio of 24 16 3 47 10. The oxides, which are hydrated during amidation, can be regenerated by calcination (12,13). 

The Hquor is then treated with calcium hydroxide (milk of lime) which reacts with the fixed salts, mosdy ammonium chloride, to Hberate ammonia. The Hquor is regenerated in a steam stripping operation. 

Usually best choice for desiccation of gases (<3% water) such as argon, helium, hydrogen, chlorine, hydrogen chloride, sulfur dioxide, ammonia, air, and chemical classes such as aliphatics, aromatics, halogenated compounds, oxygenated compounds (siUca gel, zeoHtes, activated alumina all alternatives some regenerable, some not). 

The anaerobic reaction of sulfur dioxide with aqueous ammonia produces a solution of ammonium sulfite [10192-30-0]. This reaction proceeds efficientiy, even with a gas stream containing as Httie as 1 wt % sulfur dioxide. The sulfur dioxide can be regenerated at a high concentration by acidulation or by stream stripping of the ammonium sulfite solution, or the sulfite can be made to precipitate and the ammonia recovered by addition of lime (243). The process can also be modified to produce ammonium sulfate for use as fertili2er (244) (see Fertilizers). In a variant of this process, the use of electron-beam radiation cataly2es the oxidation of sulfur dioxide in the presence of ammonia to form ammonium sulfate (245). 

Sodium hydrogen zirconium phosphate [34370-53-17 is an ion-exchange material used in portable kidney dialysis systems which regenerate and reckculate the dialysate solution. The solution picks up urea during the dialysis. The urea reacts with urease to form ammonia, which is absorbed by the sodium hydrogen zirconium phosphate. 

The ammonia-water absorption system was extensively used until the fifties when the LiBr-water combination became popular. Figure 11-103 shows a simplified ammonia-water absorption cycle. The refrigerant is ammonia, and the absorbent is dilute aqueous solution of ammonia. Ammonia-water systems differ from water-lithium bromide equipment to accommodate major differences Water (here absorbent) is also volatile, so the regeneration of weak water solution to strong water solution is a fractional distillation. Different refrigerant (ammonia) causes different, much higher pressures about 1100-2100 kPa absolute in condenser. 

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