Pressure nitrogen

Recombination reactions are highly exothermic and are inefficient at low pressures because the molecule, as initially formed, contains all of the vibrational energy required for redissociation. Addition of an inert gas increases chemiluminescence by removing excess vibrational energy by coUision (192,193). Thus in the nitrogen afterglow chemiluminescence efficiency increases proportionally with nitrogen pressure at low pressures up to about 33 Pa (0.25 torr) (194). However, inert gas also quenches the excited product and above about 66 Pa (0.5 torr) the two effects offset each other, so that chemiluminescence intensity becomes independent of pressure (192,195). 

Pure zirconium tetrachloride is obtained by the fractional distillation of the anhydrous tetrachlorides in a high pressure system (58). Commercial operation of the fractional distillation process in a batch mode was proposed by Ishizuka Research Institute (59). The mixed tetrachlorides are heated above 437°C, the triple point of zirconium tetrachloride. AH of the hafnium tetrachloride and some of the zirconium tetrachloride are distiUed, leaving pure zirconium tetrachloride. The innovative aspect of this operation is the use of a double-sheU reactor. The autogenous pressure of 3—4.5 MPa (30—45 atm) inside the heated reactor is balanced by the nitrogen pressure contained in the cold outer reactor (60). However, previous evaluation in the former USSR of the binary distiUation process (61) has cast doubt on the feasibHity of also producing zirconium-free hafnium tetrachloride by this method because of the limited range of operating temperature imposed by the smaH difference in temperature between the triple point, 433°C, and critical temperature, 453°C, a hafnium tetrachloride. 

Properties. Under nitrogen pressure hexagonal boron nitride melts at about 3000°C but sublimes at about 2500°C at atmospheric pressure. Despite the high melting point, the substance is mechanically weak because of the relatively easy sliding of the sheets of rings past one another (3). The theoretical density is 2.27 g/mL and the resistivity is about 10 H-cm. 

Nitrogen pressur- Check line integrity and all fittings, couplings, ization of lines or etc. before transfer is started equipment that are not sealed tight. CCPS G-22 CCPS G-29... 

The nitrogen line pressure is set to a level much less than the experimental pressure. With the nitrogen cylinder open, a check valve prevents the feed gas from getting into the nitrogen cylinder. When the surge check valve cuts off the synthesis gas feed, the unit becomes depressurized. Then pressure drops below the nitrogen pressure level, nitrogen flow will start and flush out the system. 

With all leaks stopped, and the reactor under test pressure with nitrogen, set the nitrogen pressure regulator to the lowest pressure on the controller, but above 0.3 atmosphere or 5 psig. Now open the flow controller and set the N2 flow to 66 mL/s, equivalent to 10.5 mols/hr rate, to start the flow. Also start heating the unit. 

The nitrogen supply used to purge the metal cabinet was also used to blow out the dryers. When the iiiirngcn supply pressure fell occasionally, solvent from the dryers entered ihrtmgh leaking valves into the nitrogen supply line,, ind into the metal cabinet. Low nitrogen pressure allowed air diffusion into the cabinet. 

Bee.iusa the nitrogen pressure was unreliable, it was difficult to maintain a pressure of 0.5 inch water gauge in the metal cabinet. Workers complained that the safety switch kept isolating the electricity supply, so an electrician reduced the setpoint first to 0.25-inch and then to zero, thus effeciocly bypassing the switch. The setpoint could not be seen unless the cover of the switch was removed and the electrician told no one what he had done. The workers though I lie wa,s a good electrician who had prevented spurious trips. Solvent and air leaked into the cabinet, as ilready described, and the next time the electricity supply was switched there was an explosion. 

The system is a storage tank designed to hold a flammable liquid under a low positive nitrogen pressure (see Figure 5.1). This pressure is controlled by PICA-1. A relief valve is fitted which operates if overpressurization occurs. Liquid is fed to the tank from a tank truck, and is subsequently supplied to the process by the pump P-1. 

A) Preparation of 1-Methyl-2-Picolinium Chloride 98 ml of cx-picoline is dissolved in 200 ml of methanol, cooled and 85 ml (at -68°C) of methyl chloride is added. The solution is charged to an autoclave, sealed and the nitrogen pressure of 300 psig is established. The mixture is heated at 120° to 130°C for 2 hours, cooled and opened. The resulting solution is then evaporated to dryness in vacuo, yielding a residue of 110 g. This residue is then dissolved in 50 ml of water and extracted with two 50 ml portions of ether. The aqueous phase is then diluted to 150 ml with water and an assay for ionic chloride is performed which indicates the presence of chloride ion equivalent to 721 mg/ml of 1-methyl-2-picolinium chloride. 

The temperature is then increased to 270-300°C and the pressure to approximately 16 atmospheres, which favors the formation of the polymer. The pressure is finally reduced to atmospheric to permit further water removal. After a total of three hours, nylon 66 is extruded under nitrogen pressure. 

Further studies revealed that the yields of l//-azepines could be increased substantially by carrying out the thermolysis of the sulfonyl azide in a nitrogen atmosphere under pressure.62-158159 For example, thermolysis of tosyl azide in benzene at 155-160 C and a nitrogen pressure of 11.5 atmospheres produced l-tosyl-l//-azepine in 5% yield, which rose to 48% under a nitrogen pressure of 82-89 atmospheres.158 The reaction temperature was critical as no azepine was formed at 140-145°C-regardless of the nitrogen pressure.160... 

Attempts to increase the yield of l//-l-benzazepines by carrying out the reactions under high nitrogen pressure were only marginally successful. For example, in dichloromethane solution and 10 kbar nitrogen pressure for seven days, the yield of dimethyl 1-methyl-l //-benzazepine-3,4-dicarboxylate is increased to only 20%.144... 

PA-4,6 salt is prepared from adipic acid and 1,4-tetramethylenediamine as described for the PA-6,6 salt (Example la). PA-4,6 salt (20 g), 2 mL water, and 0.2 mL 1,4-tetramethylenediamine (2.1 mol % excess) are added to a 100-mL glass container in an autoclave. The autoclave is flushed with nitrogen, closed, and given a starting nitrogen pressure of 5 bar. The autoclave is heated over a period of 60 min to 180° C and maintained at that temperature for 100 min, when the pressure is increased to about 8 bar. The pressure is then gradually released, the reaction mass cooled, and the material removed from the autoclave. The prepolymer is crushed into small particles (0.1—0.2 mm) (see Example lb). This prepolymer has a relative viscosity (r]rd) of 1.3 as measured in 96% sulfuric acid (1% solution at 25° C). 

Figure 6. Glow discharge in nitrogen Pressure = 0.3 mm Hg nickel cathode ions are sampled from the cathode % yield refers to % total ions observed. At very low discharge currents the distinct glow in front of the cathode disappears, and a continuous glow corona) is obtained throughout the discharge tube...

A stainless steel cannula with a 2-mm. inside diameter and both ends sharpened is inserted through the septum into the receiving flask above the surface of the liquid, and a stream of nitrogen is passed briefly through the stopcock and out the cannula to remove air. The other end of the cannula is then inserted through the septum on the reaction vessel, the end of the cannula in the receiver is pushed below the surface of the liquid, and the solvent is forced into the reaction vessel with nitrogen pressure. 

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