Separation traps

All of the traps mentioned so far protect the vacuum line, pumps, pump liquids, and/or the people using the system. There can be other traps on vacuum systems whose function is not for protection, but rather as tools for chemistry. Separation traps fall into this category and can separate a mixed compound into different fractions by using the appropriate freezing temperatures.  

Separation traps are typically a collection of interlinked U-shaped traps attached off the main vacuum line by two stopcocks (see Fig. 7.35). This arrangement allows separations of the mixed compound into as many traps as your system has. Once separation is complete, any fraction of the separation may be removed from the system at any time and in any order. The contents within a trap may even be sent back to the main holding trap for further separation. The following will provide a generalized procedure for utilizing such a separation process  

After the extension line on the vacuum system has been evacuated, close all stopcocks except 14 and 12. 

Place liquid nitrogen (in a Dewar) around the holding trap. 

Stopcocks 15 and 1 can be opened and using the cold from the liquid nitrogen as a sorption pump, transfer the mixed compound into the holding trap (you may want to lightly heat the original compound to facilitate the transfer). 

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A mixture of cyclohexanone (11.8 g, 0.12 mole), ethylene glycol (8.2 g, 0.13 mole), /j-toluenesulfonic acid monohydrate (0.05 g), and 50 ml of benzene is placed in a 250-ml round-bottom flask fitted with a water separator and a condenser (drying tube). The flask is refluxed (mantle) until the theoretical amount of water (approx. 2.2 ml) has collected in the separator trap. The cooled reaction mixture is washed with 20 ml of 10 % sodium hydroxide solution followed by five 10-ml washes with water, dried over anhydrous potassium carbonate, and filtered. The benzene is removed (rotary evaporator) and the residue is distilled, affording l,4-dioxaspiro[4.5]decane, bp 65-67713 mm, 1.4565-1.4575, in about 80% yield. 

Abscheider, m. separator trap refiner. Abscheidung,/. separation elimination refining deposit secretion departure, Abscheidungs-mittel, n. means of separation precipitant, -produkt, n. secretion, -ver-fahren. n. separation process, vorrichtung, /. separator. 

Extraction System. The flow-through extraction system used in this study is shown in Figure 1. The system is operable up to 400 bar at 200°C. It consists of solvent delivery systems (Fluid 1, Fluid 2, Fluid 3), a flow-through reactor (FR), a set of separator traps (TP1, TP2), and the temperature and pressure control units. The reactor, traps, micrometering valves, and tubing connections are housed in a heated oven. 

Figure 1. Experimental system for supercritical fluid extraction. LF = line filter PG = pressure gauge SV = shut-off valve CV = check valve PHC = preheating coil TC = thermocouple MV = micrometering valve TP = separator trap subscripts r = reactor 1,2 = trap 1,2.

Diimines 3 of 2,2,4,4-tetramethylcyclobutane-l,3-dione were formed by the addition of an excess of primary amines in the presence of titanium(IV) chloride.293- 294 When one equivalent of the amine was used, the mono-imine 2 was isolated. If steric hindrance is a limiting factor, this method is preferred.294 However, an ordinary water separation trap can also be used, omitting the titanium(IV) chloride.295-296 In the latter case, the use of chiral amines such as ( + )-dehydroabietylamine, (+)-ris-2,2-dimethyl-6-phenyl-l,3-dioxan-5-arnine or (-)-a-pheny-lamine, can be used to resolve a racemic mixture of 3,7,7-trimethylbicyclo[3.2.0]hept-2-en-6-one via the corresponding imines.296... 

Batch Stirred Tank H2S04/Oleum Aromatic Sulfonation Processes. Low molecular weight aromatic hydrocarbons, such as benzene, toluene, xylene, and cumene, are sulfonated using molar quantities of 98—100% H2S04 in stirred glass-lined reactors. A condenser and Dean-Stark-type separator trap are installed on the reactor to provide for the azeotropic distillation and condensation of aromatic and water from the reaction, for removal of water and for recycling aromatic. Sulfone by-product is removed from the neutralized sulfonate by extraction/washing with aromatic which is recycled. 

Analysis is accomplished by standard vacuum-line techniques. A 1.00-mL aliquot of (CH3)3N-A1H3 in benzene solution is placed in an ampul and attached to a multipurpose vacuum line equipped with gas-separation traps and a Toepler pump and is hydrolyzed by using a mixture composed of equal amounts of water and concentrated hydrochloric acid. 

Dual particle or separate traps such as RV4+ must have attrition and fluidization properties similar to FCC catalyst. Their advantages are that they do not change the selectivity of the base catalyst and theoretically have a higher capacity for vanadium capture. Performance evaluation of dual particle traps is usually simpler. They can often be isolated from equilibrium catalyst and analyzed for vanadium capture. Confirmation of preferential pick up on integral traps tends to be a bit more qualitative. A disadvantage may be that they are more dependent on vanadium mobility than integral traps. 

In most cases preconcentration of analytes occurs with simultaneous matrix accumulation. Matrix simplification can be achieved through the sampling process, the use of a rinse solvent prior to analyte transfer, and selective transfer of front-, heart- or end-cuts of the desorbed sample extract. Dual precolumn systems allow solvent exchange and separate trapping of analytes with a wide range of breakthrough volumes. The first column of a dual precolumn system can be used to retain strongly sorbed matrix components that would contaminate the second precolumn or interfere in the separation of the transferred extract. 

Traps. Every fixture and each piece of equipment should be separately trapped by a valve or a water-sealing trap placed as close to the fixture outlet as possible, and no trap should be placed more than 2 ft from any fixture. The sizes of traps for chemical equipment depend upon the desired drain-off, but for sanitary purposes the minimum size is stipulated in the code. Closed traps must be of 4-in, size, while those for sinks, urinals, showers, and the like must not be under 2 in. 

Clow and Futrell use a 12-in. magnet which permits the use of a longer ICR cell with an additional reaction zone between the source and analyzer regions. The source region has separate trapping plates from those of the reaction-analyzer zones. Better ion transmission is achie-... 

Fig. 12.21 Schematic diagram of a hydride generation cryotrap-AAS (HC/CT/AAS-)system for speciation analysis of organometallic compounds A, four-way valve B, hydride generator C, heated transfer lines D, separation trap in liquid nitrogen E, quartz furnace with inlets for hydrogen and oxygen gas (reproduced with permission from L Randall, O. F.X. Donard,...

Refractive Index Modulation by Esc- Photorefractive behavior in polymers can be very roughly modeled by assuming a one-dimensional index of refraction change caused by the vector siun of the applied bias field and a space-charge field resulting from separated, trapped charges within the material... 

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