Patent ID: 7390932

Claim:
A process for preparing high-concentration gaseous formaldehyde having a molar CH 2 O:H 2 O ratio of ≧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 evaporation temperature T and the gas phase formed is taken off, wherein the evaporation temperature T obeys the relationship: T [° C.]≧T′ min [° C.] where T′ min (c)=A+B×(c/100)+C×(c/100) 2 +D×(c/100) 3 and A=+68.759, B=+124.77, C=−12.851, D=−10.095, where c is the instantaneous CH 2 O content of the aqueous formaldehyde solution during the evaporation in percent by weight and is from 20 to 99% by weight.