Tubes packing

Macroscopic properties often influence tlie perfoniiance of solid catalysts, which are used in reactors tliat may simply be tubes packed witli catalyst in tlie fonii of particles—chosen because gases or liquids flow tlirough a bed of tliem (usually continuously) witli little resistance (little pressure drop). Catalysts in tlie fonii of honeycombs (monolitlis) are used in automobile exliaust systems so tliat a stream of reactant gases flows witli little resistance tlirough tlie channels and heat from tlie exotlieniiic reactions (e.g., CO oxidation to CO,) is rapidly removed. 

Any free bromine can be removed by passing the evolved gas through a U tube packed with glass beads covered with moist violet phosphorus (Figure 113). 

The furnace and thermostatic mortar. For heating the tube packing, a small electric furnace N has been found to be more satisfactory than a row of gas burners. The type used consists of a silica tube (I s cm. in diameter and 25 cm. long) wound with nichrome wire and contained in an asbestos cylinder, the annular space being lagged the ends of the asbestos cylinder being closed by asbestos semi-circles built round the porcelain furnace tube. The furnace is controlled by a Simmerstat that has been calibrated at 680 against a bimetal pyrometer, and the furnace temperature is checked by this method from time to time. The furnace is equipped with a small steel bar attached to the asbestos and is thus mounted on an ordinary laboratory stand the Simmerstat may then be placed immediately underneath it on the baseplate of this stand, or alternatively the furnace may be built on to the top of the Simmerstat box. 

The furnace. For heating the tube packing, a small electric furnace E is used, similar to that described in the carbon and hydrogen determination. It is 22 cm. in length and 1 5 cm. in diameter. The furnace is maintained at 680 C., as before, by a calibrated Simmerstat and its temperature is checked from time to time with a bimetal pyrometer. 

The fiimace E is now switched on, and takes about 20 minutes before the combustion tube packing has reached the required temperature. After 15 minutes, carbon dioxide is again passed for 5 minutes, and the apparatus tested as before for the appearance of micro-bubbles. If these are not at first obtained, the sweeping-out process must be continued until they do appear. Now that the combustion-tube packing is heated up to the required temperature and the apparatus filled with carbon dioxide, all air being swept out, the combustion may be started. 

By employing a shghtly modified funnel, the glass nail can be utilised, in conjunction with a drying p. tube packed with desiccant, for drying the product... 

Stage one - the reaction happens in the form of a reflux with a dry set-up. You will need a 2000ml reaction flask, a condenser and a drying tube packed with calcium chloride or other drying agent. The reaction needs to be stirred in a big way, so before we add the ingredients make sure you have a clean stirrer bar ready, I prefer the eggy shape bars as they tend to be less noisy. 

The saturated calomel electrode (SCE), which is constructed using an aqueous solution saturated with KCl, has a potential at 25 °C of -hO.2444 V. A typical SCE is shown in Eigure 11.8 and consists of an inner tube, packed with a paste of Hg, HgiCli, and saturated KCl, situated within a second tube filled with a saturated solution of KCl. A small hole connects the two tubes, and an asbestos fiber serves as a salt bridge to the solution in which the SCE is immersed. The stopper in the outer tube may be removed when additional saturated KCl is needed. The shorthand notation for this cell is... 

Packed Tubes Cocurrent flow of immiscible hquids through a packed tube produces a one-stage contact, characteristic of hne mixers. For flow of isobutanol-water through a 0.5-in diameter tube packed with 6 in of 3-mm glass beads, Leacock and Churchill [Am. Jn.st. Chem. Eng. J., 7, 196 (1961)] find... 

The original flask used for the enamine formation can be used after the attachment of a Y-shape tube fitted with a dropping funnel and a reflux condenser protected with a tube packed with a drying agent such as anhydrous calcium chloride. 

Cyclohexene can be prepared on a large scale still more rapidly and efficiently by the distillation of cyclohexanol over silica geP or, better, activated alumina. Using a 25-mm. tube packed with 8- to 14-mesh activated alumina (Aluminum Company of America) and heated to 380-450 over a 30-cm. length, 1683 g. of cyclohexanol was dehydrated in about four hours. After separating the water, drying with sodium sulfate, and fractionating with a simple column, 1222 g. (89 per cent yield) of cyclohexene, b.p. 82-84 , was obtained. 

U-Tube/ Packed Floatmg Head/ Packed Floatmg Tubesheet/ Internal Floatmg Head (AH these tvpes have removable bundles) ... 

The product is analyzed by vapor phase chromatography using a 6-ft., f-in. O.D. copper tube, packed with 5% Bentone-34 (Wilkins Instrument Co.) and 0.5% XF-1150 (General Electric Silicone Products) on Diatoport-S (80-100 mesh) (F and M Co.) flow rate of helium 60 ml./min., oven temperature 85°. This column separates m-cymene (retention time 12 minutes) from />-cymene (retention time 10 minutes) but does not resolve the ortho isomer. The purity of the distilled w-cymene is above 98%. 

An elegant extension of these intramolecular acylnitrene-induced ring expansions has been used for the synthesis of cyclopent[h]azepines.2 2-Haloindan-l-yl azidoformates 14 (X = Cl, Br), when subjected to pyrolysis at 300 °C in a hot tube packed with calcium oxide and copper turnings, produce cyclopent[6]azepine (15), as a dark turquoise oil, in excellent yield. Lesser yields (30 and 50%, respectively) of the 4-bromo and 3-methoxy derivatives can be similarly obtained. 

Wash the SPE tube packing with three 200-/a1 aliquots of water, dry it with nitrogen for 5 min, and elute the drugs with three 100-ju-1 aliquots of 90 parts ethanol and 10 parts diethyl ether. Concentrate the recovered drugs by evaporating some or all of the solvent before analysis by GC/MS. (See Supelco Bulletin 810B.)... 

The solid phase extraction cartridge (SPEC) is another somewhat vainglorious name given to a short inert plastic tube packed with an adsorbent, usually a reversed phase or an ion exchange resin. The particle size of the packing is often significantly larger than that used... 

Into a size 6A porcelain boat (88 X 13 X 10 mm.) is placed 10.0 g. (0.0113 mol) of Ag2ReBr6 (as much as 15 g. may be processed readily), and the boat is positioned near the sealed end of a 25 X 300 mm. Pyrex tube fitted with an inner 29/44 S.T. sleeve joint. The tube is connected to a mechanical vacuum pump (capable of reducing the pressure to ca. 50 p) via either a trap cooled by liquid nitrogen or a trap cooled by a Dry Ice-isopropyl alcohol slush, which is in turn connected to an 11-mm. Vycor combustion tube packed with copper gauze and maintained at 600° by means of a furnace. (Either protective system between the tube and the pump will serve to remove bromine, one of the reaction products.)... 

CL sensors based on immobilization of nonenzyme reagents have been extensively studied in recent years. Nakagama et al. [63] developed a CL sensor for monitoring free chlorine in tap water. This sensor consisted of a Pyrex tube, packed with the uranine (fluoresceine disodium) complex immobilized on IRA-93 anion-exchange resin, and a PMT placed close to the Pyrex tube. It was used for monitoring the concentration of free chlorine (as HCIO) in tap water, up to 1 mmol/L, with a detection limit of 2 nmol/L. The coefficient of variation (n =... 

To create a useful CFD simulation the model geometry needs to be defined and the proper boundary conditions applied. Defining the geometry for a CFD simulation of a packed tube implies being able to specify the exact position and, for nonspherical particles, orientation of every particle in the bed. This is not an easy task. Our experience with different types of experimental approaches has convinced us that they are all too inaccurate for use with CFD models. This leads to the conclusion that the tube packing must either be computergenerated or be highly structured so that the particle positions can be calculated analytically. 

Fig. 21. Randomly packed tube packed with reforming catalyst.

Since hydrogen chloride is evolved in the early stages of this distillation, no effort is made to control the pressure. The vacuum pump is protected from the hydrogen chloride by insertion of a 1.5 X 15-in. glass tube packed with sodium hydroxide pellets in the vacuum line. The purpose of this distillation is to remove dissolved hydrogen chloride and the zinc chloride catalyst it should be completed as rapidly as possible, under the best vacuum attainable, with no attempt at fractionation. The distillate may be fractionally distilled for further purification if... 

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