Drying by hydrolysis

Drying by hydrolysis. The production of extremely dry (99 -9-(- per cent.) ethyl alcohol from commercial absolute alcohol (99-f percent.) is possible by taking advantage of the fact that the hydrolysis of an ester consumes water. Thus if the absolute alcohol is treated with a little sodium in the presence of an ester of high boiling point e.g., ethyl... 

If either dry powders or inverse emulsions are not properly mixed with water, large lumps of polymer form that do not dissolve. This not only wastes material, but can also cause downstream problems. This is especially tme for paper where visible defects may be formed. Specialized equipment for dissolving both dry polymers and inverse emulsions on a continuous basis is available (22,23). Some care must be taken with regard to water quaUty when dissolving polyacrylamides. Anionic polymers can degrade rapidly in the presence of ferrous ion sometimes present in well water (24). Some cationic polymers can lose charge by hydrolysis at high pH (25). 

Hydrolysis of Dimethyl Terephthalate. Hoechst Celanese and Eormosa Chemical Eibers Corp. produce a polymer-grade terephthahc acid by hydrolysis of high purity dimethyl terephthalate. Hbls-Troisdorf AG hcenses a process with this step (70). Hydrolysis occurs at 260—280°C and 4500—5500 kPa (45—55 atm) in a hydrolysis reactor without catalysis. The overhead methanol and water vapor is separated and the methanol is returned to the dimethyl terephthalate section for reuse. The reactor hquid is crystallized, cycloned, washed, and further cooled. Einahy, the slurry is centrifuged and dried. The product has less than 25 ppm of 4-formylbenzoic acid and very low levels of other impurities. There may be several hundred parts per million of monomethyl terephthalate, which is incompletely hydrolyzed dimethyl terephthalate. 

Sol-Gel Techniques. Sol-gel powders (2,13,15,17) are produced as a suspension or sol of coUoidal particles or polymer molecules mixed with a Hquid that polymerizes to form a gel (see Colloids SoL-GELtechnology). Typically, formation of a sol is foUowed by hydrolysis, polymerization, nucleation, and growth. Drying, low temperature calciaation, and light milling are subsequently required to produce a powder. Sol-gel synthesis yields fine, reactive, pseudo-crystalline powders that can be siatered at temperatures hundreds of degrees below conventionally prepared, crystalline powders. 

The products of these reactions with maleic anhydride, termed maleated oils, react with polyols to give moderate mol wt derivatives that dry faster than the unmodified oils. For example, maleated, esterified soybean oil is a drying oil with a drying rate comparable to that of a bodied linseed oil with a similar viscosity. Maleated linseed oil can be converted to a water-dilutable form by hydrolysis with aqueous ammonium hydroxide to convert the anhydride groups to ammonium salts of the diacid. Such products have not found significant commercial use, but similar reactions with alkyds and epoxy esters are used on a large scale to make water-dilutable derivatives. 

SG sols were synthesized by hydrolysis of tetraethyloxysilane in the presence of polyelectrolyte and surfactant. Poly (vinylsulfonic acid) (PVSA) or poly (styrenesulfonic acid) (PSSA) were used as cation exchangers, Tween-20 or Triton X-100 were used as non- ionic surfactants. Obtained sol was dropped onto the surface of glass slide and dried over night. Template extraction from the composite film was performed in water- ethanol medium. The ion-exchange properties of the films were studied spectrophotometrically using adsorption of cationic dye Rhodamine 6G or Fe(Phen) and potentiometrically by sorption of protons. 

Citraconic anhydride [616-02-4] M 112.1, m 8-9°, b 47°/0.03mm, 213°/760mm, d4 1.245, ng 1.472. Possible contamination is from the acid formed by hydrolysis. If the IR has OH bands then reflux with AC2O for 30 min, evaporate then distil the residue in a vacuum otherwise distil in a vacuum. Store in a dry atmosphere. [Biochem J 191 269 1980.]... 

NaHC03 H2O, dry (MgS04), filter, evaporate and distil residue. Identified by hydrolysis to the acid and determining the neutralisation equiv (theor 80.0). The acid has m 155-157° efferv [Hauser, Abramovitch and Adams J Am Chem Soc 64 2715 1 942 Bush and Beauchamp J Am Chem Soc 75 2949 1953]. 

Aluminium fluoride (anhydrous) [7784-18-4] M 84.0, m 250°. Technical material may contain up to 15% alumina, with minor impurities such as aluminium sulfate, cryolite, silica and iron oxide. Reagent grade AIF3 (hydrated) contains only traces of impurities but its water content is very variable (may be up to 40%). It can be dried by calcining at 600-800° in a stream of dry air (some hydrolysis occurs), followed by vacuum distn at low pressure in a graphite system, heated to approximately 925° (condenser at 900°) [Henry and Dreisbach J Am Chem Soc 81 5274 1959]. 

Di-/i-butyltin oxide [SI8-08-6] M 248.9, m >300 . It is prepd by hydrolysis of di-n-butyltin dichloride with KOH. Hence wash with a little aq M KOH then H2O and dry at 80 /10mm until the IR is free from OH bands. [Cummings Aust J Chem 18 98 7965.]... 

Lithium methylate (lithium methoxide) [865-34-9] M 38.0. Most probable impurity is LiOH due to hydrolysis by moisture. It is important to keep the sample dry. It can be dried by keeping in a vacuum at 60-80° under dry N2 using an oil pump for a few hours. Store under N2 in the cold. It should not have bands above 3000cm-> IR has VKBr 1078, 2790, 2840 and 2930cm-. [JOrgChem 21 156 7956.]... 

Acetylated polysaccharides form part of the structure of wood, the acetyl radical constituting some 2-5Vo by weight of the dry wood. Hydrolysis to free acetic acid occurs in the presence of moisture at a rate varying from one species to another a wood of lower acetyl content can liberate acetic acid much faster under given conditions than another wood of higher content Small quantities of formic, propionic and butyric acids are also formed but their effects can be neglected in comparison with those of acetic acid. There is a broad, but only a broad, correlation between the corrosivity of a wood and its acidity. The chemistry of acetyl linkage in wood and of its hydrolysis has been examined in some detail. ... 

Thermally stable AI2O3 was synthesized as in ref. 5, by hydrolysis of A1 isopropoxide (99.99+% Aldrich Chemicals) dissolved in 2-methylpentane-2,4-diol. The resulting solid was filtered, washed in 2-propanol, and dried in air at 373 K. Then, it was calcined in flowing dry air, while the temperature was raised at 1 K/min to 733 K, when 2.4% HjO was introduced to the flowing air. Afterwards, the temperature ramp was continued to 973 K. The sample was kept at 973 K for 2 h in 7% water. The isoelectric point of the resulting y-Al Oj was pH 8. The BET surface areas were 205 to 235 mVg, and the average pore size radius was around 8.3 nm... 

All copolymers were prepared by solution polymerization, under adiabatic conditions, giving at least 99.9% conversions. The polymer gels were granulated and then dried at 90 °C to a residual water content of 10 to 12%. The active polymer content of each sample was calculated from the initial weight of the comonomers and the weight of the dried gel. Hydrolysis of the polymers was determined by conductometric titration to be less than 0.2% of the acrylamide charge. The molecular weight of the polymers was 8-10 million as determined by intrinsic viscosity measurements. 

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