Nitrogen generation

Most nitrogen generators process compressed air at 7 to 20 atm. pressure and deliver the nitrogen-rich product within one to two atmospheres of the feed pressure. The degree of pretreatment of the air supplied to the membrane varies with the membrane employed and manufacturer. The performance of some membranes is sensitive to the moisture content of the air. In these cases, the compressed air is dried before processing. Other membranes are sensitive to organic vapors and oils that are removed by carbon filters or absorption beds. 

Most generators are also supplied with filtration systems to remove condensate, mist, and any particulates that might plug the membrane flow channels or fiber bores. Since the permeability and selectivity of the membranes can be highly temperature dependent, most applications require the air feed to be temperature controlled in order to control the product nitrogen quality or the membrane s performance. The nitrogen product is typically delivered under pressure and flow regulation to a receiver from which it is dispensed to users on demand. The coproduced permeate is typically simply vented back to the atmosphere. 

Controlled atmosphere storage - Membranes are used to maintain controlled 

Tank and process equipment inerting - Many offshore platforms, marine terminals, refinery and chemical tank farms are supplied with membrane-generated nitrogen. 

Industrial gas sales - Many membrane suppliers are owned by or affiliated with industrial gas companies. They use onsite nitrogen generators to supply nitrogen to meet customer demand from baseload to total site nitrogen requirements, frequently supplemented with hquid nitrogen supply or backup. 

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Fig. 3. Pressure swing adsorption nitrogen generation system. CMS = carbon molecular sieve.

C-H activation a to nitrogen generates f3-amino acid derivatives (Figure 5). Therefore, the reaction can be considered to be a surrogate of the Mannich reaction. 

The only available evidence to support this is the fate of intermediates generated from the reaction of A-acyloxy-A-alkoxyamides with cysteine derivatives in methanol described in Section IV.C.3.b. The nucleophilic thiol reacts preferentially at the sulfur atom rather than at nitrogen, generating the hydroxamic ester and the disulfide (Scheme 24). 

Many nitrogen generator devices are commercially available to produce high purity gas in small amounts. In these, nitrogen is obtained from compressed air. It is separated from other air components by selective permeation through polymeric hollow fiber membranes after prefiltration. 

Dry diazodicyanoimidazole is highly explosive, however one can work safely with its solutions. When heated to 80°C in solution, 26 loses nitrogen, generating a highly electrophilic intermediate (Scheme 12) (73JA2695). Its chemical characteristics more resemble carbonium ions than aryne or carbodiimide. 

The reaction is completed within five minutes at room temperature. Thus, measurement of the volume of nitrogen generated can be used in amino add determinations. 

A third biosynthetic pathway to /-alanine 3 by oxidation of spermidine 13 and spermine 1 has been recently elucidated in yeast [17]. This reaction starts by transformation of L-methionine 15 to decarboxyadenosylmethionine (dcAdoMet, 16). The latter alkylates putrescine 12 at one or both nitrogens generating spermidine 13 and spermine 1 which are oxidized to 3-aminopropanal 14 and further to /-alanine (Scheme 1.6.4). 

Nitrogen generator (or equivalent cylinder with regulator) for heater/evaporator... 

A heater/evaporator with separate aluminium heating blocks (three sizes compatible with the vials glassware) and 6-position nitrogen purge concentrator with tubing for connection to nitrogen generator... 

Heater/evaporator to be used with pure nitrogen from a nitrogen generator (optional item) or a nitrogen cyhnder... 

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