Drying of powders

The drying of powder was formerly one of the most hazardous operations, but since the causes of danger have been eliminated by new methods it is now no more dangerous than any other of the processes for manufacturing nitrocellulose powder. The following rules must always be observed ... 

For reason of economy, formed pieces should be dried as quickly as possible however, the drying rate is limited by the risk of undesirable deformation or cracking resulting from excessively fast removal of water. This is the principal difference compared with the drying of powders and materials where loss of cohesion is not detrimental. 

Titanium sulfate supported on zirconia catalysts were prepared by drying of powdered Zr(OH)4 with titanium sulfate aqueous solution followed by calcining in air at high temperature. The characterization of prepared catalysts was performed using Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by the measurement of surface area. The addition of titanium sulfate to zirconia shifted the phase transition of ZrOa from amorphous to tetragonal to higher temperature because of the interaction between titanium sulfate and zirconia. The catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation were correlated with the acidity of catalysts measured by ammonia chemisorption method. 

For drying of powders in the particle size range of 50-2000 pm, fluidized beds compete successfully with other more traditional dryer types, for example, rotary, tunnel, conveyor, or continuous tray (see Table 8.1). 

This heating and drying techniqne, developed by EA Technology [35], was tested for drying of powders, crystals. 

Pneumatic dryer for the finish drying of powders or granulated materials starch, flour, proteins, distillery residues, aspartame, guar gum, methionine... 

Prepare a solution of 12 5 g. of hydroxylamine hydrochloride in 20 ml. of water contained in a too ml. conical flask. Dissolve 7 g. of powdered sodium hydroxide in 20 ml. of water, cool the solution in ice-water, and then add it to that of the hydroxylamine hydrochloride. Place a thermometer in the mixed solution, and chill the flask in ice-water until the temperature of the solution is between 5 and 10 . Now add 12 ml. (9 5 gO of dry acetone (preferably from a burette to ensure... 

Place I g. of powdered 3,5-dinitrobenzoyl chloride in a small conical flask, add 2 5 ml. of dry methanol, and warm on a water-bath until the solid has dissolved. Cool and filter off the 3,5-dinitrobenzoate which has separated. Recrystallise from ethanol or petroleum (b.p. 60-80°). The ester separates in colourless crystals, m.p. 108°. Yield,... 

A 1500 ml. flask is fitted (preferably by means of a three-necked adaptor) with a rubber-sleeved or mercury-sealed stirrer (Fig. 20, p. 39), a reflux water-condenser, and a dropping-funnel cf. Fig. 23(c), p. 45, in which only a two-necked adaptor is shown or Fig. 23(G)). The dried zinc powder (20 g.) is placed in the flask, and a solution of 28 ml. of ethyl bromoacetate and 32 ml. of benzaldehyde in 40 ml. of dry benzene containing 5 ml. of dry ether is placed in the dropping-funnel. Approximately 10 ml. of this solution is run on to the zinc powder, and the mixture allowed to remain unstirred until (usually within a few minutes) a vigorous reaction occurs. (If no reaction occurs, warm the mixture on the water-bath until the reaction starts.) The stirrer is now started, and the rest of the solution allowed to run in drop-wise over a period of about 30 minutes so that the initial reaction is steadily maintained. The flask is then heated on a water-bath for 30 minutes with continuous stirring, and is then cooled in an ice-water bath. The well-stirred product is then hydrolysed by the addition of 120 ml. of 10% sulphuric acid. The mixture is transferred to a separating-funnel, the lower aqueous layer discarded, and the upper benzene layer then... 

Transfer the quinoline chlorozincate to a beaker, add a small quantity of water, and then add 10% sodium hydroxide solution until the initial precipitate of zinc hydroxide completely redissolves, and the free quinoline separates. Transfer the mixture to a separating-funnel, wash out the beaker with ether, adding the washings also to the solution in the funnel, and then extract the quinoline twice with ether. Dry the united ethereal extracts by adding an ample quantity of powdered potassium hydroxide and... 

Dinitrobenzoylation. To 0 5 g. of powdered 3,5-dinitro benzoyl chloride (preparation, p. 240) in a dry test-tube, add 2 ml. of dry methanol and warm the mixture until a clear solution is obtained. Cool and filter off the solid ester which separates. Recrystallise from petroleum (b.p. 60-80 ), and take the m.p. (M.ps., pp. 536, 537.)... 

Bromoform. Commercial bromoform should be shaken thoroughly with water, separated, dried over powdered anhydrous sodium sulphate and then fractionally distilled under reduced pressure using a water-condenser. It should be stored in a dark cupboard. It is an excellent solvent, has the advantage of a high Constant, and very seldom causes association of the solute. 

Cuprous bromide. The solid salt may be prepared by dissolving 150 g. of copper sulphate crystals and 87 5 g. of sodium bromide dihydrate in 500 ml. of warm water, and then adding 38 g. of powdered sodium sulphite over a period of 5-10 minutes to the stirred solution. If the blue colour is not completely discharged, a little more sodium sulphite should be added. The mixture is then cooled, the precipitate is collected in a Buchner funnel, washed twice with water containing a little dissolved sulphurous acid, pressed with a glass stopper to remove most of the liquid, and then dried in an evaporating dish or in an air oven at 100 120°. The yield is about 80 g. 

Place a mixture of 1 0 g. of the hydrocarbon, 10 ml. of dry methylene chloride or ethylene dichloride or syw.-tetrachloroethane, 2 5 g. of powdered anhydrous aluminium chloride and 1-2 g. of pure phthalic anhydride in a 50 ml. round-bottomed flask fitted with a short reflux condenser. Heat on a water bath for 30 minutes (or until no more hydrogen chloride fumes are evolved), and then cool in ice. Add 10 ml. of concentrated hydrochloric acid cautiously and shake the flask gently for 5 min utes. Filter oflf the solid at the pump and wash it with 10-15 ml. of cold water. Boil the resulting crude aroylbenzoic acid with 10 ml. of 2 -5N sodium carbonate solution and 0 2 g. of decolourising carbon for 5 minutes, and filter the hot solution. Cool, add about 10 g. of crushed ice and acidify... 

Into a 1-litre beaker, provided with a mechanical stirrer, place 36 - 8 g. (36 ml.) of aniline, 50 g. of sodium bicarbonate and 350 ml. of water cool to 12-15° by the addition of a little crushed ice. Stir the mixture, and introduce 85 g. of powdered, resublimed iodine in portions of 5-6 g, at intervals of 2-3 minutes so that all the iodine is added during 30 minutes. Continue stirring for 20-30 minutes, by which time the colour of the free iodine in the solution has practically disappeared and the reaction is complete. Filter the crude p-iodoaniline with suction on a Buchner funnel, drain as completely as possible, and dry it in the air. Save the filtrate for the recovery of the iodine (1). Place the crude product in a 750 ml. round-bottomed flask fitted with a reflux double surface condenser add 325 ml. of light petroleum, b.p. 60-80°, and heat in a water bath maintained at 75-80°. Shake the flask frequently and after about 15 minutes, slowly decant the clear hot solution into a beaker set in a freezing mixture of ice and salt, and stir constantly. The p-iodoaniline crystallises almost immediately in almost colourless needles filter and dry the crystals in the air. Return the filtrate to the flask for use in a second extraction as before (2). The yield of p-iodoaniline, m.p. 62-63°, is 60 g. 

Triturate 20 g. of dry o-toluidine hydrochloride and 35 5 g. of powdered iodine in a mortar and then grind in 17 -5 g. of precipitated calcium carbonate. Transfer the mixture to a conical flask, and add 100 ml. of distilled water with vigorous shaking of the flask. Allow the mixture to stand for 45 minutes with occasional agitation, then heat gradually to 60-70° for 5 minutes, and cool. Transfer the contents of the flask to a separatory funnel, extract the base with three 80 ml. portions of ether, diy the extract with anhydrous calcium chloride or magnesium sulphate, and remove the excess of solvent. The crude 5-iodo-2-aminotoluene separates in dark crystals. The yield is 32 g. Recrystallise from 50 per cent, alcohol nearly white crystals, m.p. 87°, are obtained. 

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