Basf Aktiengesellschaft

Eckard Stroefer

Hans Hasse

Thomas Grützner

Ulrich Steinbrenner

Neven Lang

Michael Ott

Process for preparing high-concentration gaseous formaldehyde having a molar CHO:HO ratio of &#x2267;0.6 from an aqueous formaldehyde solution by evaporation of at least part of the solution, in which the aqueous formaldehyde solution is heated to a vaporization temperature T and the gas phase formed is taken off, wherein the evaporation temperature T obeys the relationship:T[&#xb0; C.]&#x2267;T'[&#xb0; C.]where T&#x2032;(c)=A+B&#xd7;(c/100)+C&#xd7;(c/100)+D&#xd7;(c/100)andA=+68.759, B=+124.77, C=&#x2212;12.851, D=&#x2212;10.095,where c is the instantaneous CHO content of the aqueous formaldehyde solution during the evaporation in percent by weight and is from 20 to 99% by weight.

Method for preparing highly concentrated, gaseous formaldehydes

Method of stabilizing high-concentration formaldehyde solutions having a CHO content of &#x3e;70% by weight against precipitation of solids, which comprises heating the high-concentration formaldehyde solution at a heating rate of at least 5&#xb0; C./min to a temperature of from 80&#xb0; C. to 200&#xb0; C. immediately after it has been prepared and storing it at a temperature in this range.

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Mannheim, Germany

Eckard Stroefer