Distillation, formaldehyde solutions Methanol, containing

A freshly-opened supply of paraformaldehyde purchased from Aldrich Chemical Company, Inc. was used by the checkers. The use of commercial formaldehyde solutions which now contain up to 15% methanol leads to the formation of several by-products which cannot be separated by distillation from the a-(hydroxymethyl)acrylate. 

Methanol containing very little formaldehyde may be obtained by the distillation of aqueous solutions which contain mixtures of the two substances in amounts up to 38 to 40 per cent. This distillate may then be used for subsequent oxidations. The residue from such a distillation contains only a trace of methanol. ... 

Selective reaction of cardol in preference to cardanol under Mannich reaction conditions with diethylenetriamine (or 4-aminobutane) and aqueous formaldehyde in methanolic solution resulted in the separation, as a lower layer, of the cardol in the form of a low polymeric Mannich base. Recovery of cardanol from the upper layer and high vacuum distillation afforded pure material containing only traces of 2-methylcardol (ref. 189). Thus technical CNSL (1 mole average mol. wt. 303g) with 40% aqueous formaldehyde (1.2 mole CHjO) and diethylenetriamine (0.125 mole) in methanol (1250ml) afforded after 30mins a dark methanol-insoluble lower... 

Procedure In a flask fitted with a reflux condenser 0.2 g of acetamide and 10 ml of 2 N NaOH are heated and distilled slowly. The distillate is collected in a flask containing 10 ml of 1% formaldehyde. The amount of liquid distilled off is made up (restored) from a dropping funnel until 20 ml of the distillate is collected. Eventually, the residue in the distillation flask is concentrated to 5 ml, neutralized with hydrochloric acid to pH 3—4, and mixed with 0.1 g of S-l-naphthylmethylthiuronium chloride. The mixture is heated until dissolved, and filtered through a folded filter, and the filtrate is allowed to cool in a refrigerator. The separated salt is filtered and washed twice with 0.5 ml of water (yield, 0.11 g mp, 142 — 143 °C). After crystallization from 4 ml of methanol the yield of pure product was 50 mg, mp 143 to 145 °C. The distillate collected in the formaldehyde solution is concentrated to 5 ml, mixed with 5 ml of a saturated picric acid solution in ethanol, and allowed to stand in a refrigerator. The picrate of hexamethylenetetramine is isolated by filtration and washed twice with 0.5 ml of water. Yield, 64 mg mp, 180—185 °C. After crystallization from 20 ml of ethanol the product (20 mg) melted at 183 °C. 

Commercially available Baker reagent grade formaldehyde contains 377o formaldehyde and 12<9Si methanol. (Therefore, a polymer solution containing 200 ppm formaldehyde also contains 65 ppm methanol.) Borden formaldehyde, uninhibited with methanol, is a special-order commodity chemical containing 36.8<9S formaldehyde. The laboratory-prepared formaldehyde was obtained by refluxing a 7.5 pH solution of paraformaldehyde and distilled water for 2 hours. After filtration, a 33.5% solution of uninhibited formaldehyde remained. 

In the incomplete conversion mode, the mixture entering the absorption unit is a solution of about 42 wt% formaldehyde and containing methanol. The bulk of the methanol, formaldehyde, and water exits the first stage of the unit. The mixture is fed into the distillation column, from which a bottom product containing up to 55 wt% formaldehyde and less than 1 wt% methanol is obtained. The formic acid content in this bottom product is reduced by using an anion-exchange unit. The methanol in the overhead product is recycled and mixed with the fresh feed. The off-gas from the absorption unit is combusted to remove the residual methanol and other organic species. Part of it is then recycled into the reactor as inert diluent. 

---