METHOD OF PRODUCING MONOMERIC FORMALDEHYDE Russian patent published in 1998 - IPC

FIELD: industrial organic synthesis. SUBSTANCE: method of producing formaldehyde containing 0.03-0.003 wt % of impurities with yield from 29.3 to 72.7% consists in thermal decomposition of methanol hemiformal containing 40-90 wt % formaldehyde followed by absorbing alcohol and admixtures from gas-vapor mixture by an organic solvent at temperature from 0 C to formaldehyde boiling point. Gas-vapor mixture can be subjected to partial condensation at +10 to 10 C until formaldehyde concentration in vapor phase exceeds 90%, condensation products being removed. Partial condensation and absorption stages can be conducted in presence of gas neutral toward formaldehyde or under vacuum. For instance, formaldehyde with summary impurity content 0.004 wt % and yield 29.3% is produced at 115 C from methanol hemiformal with 40% formaldehyde fed with rate 10.4 kg/h and subsequent mixing of formed gas-vapor mixture with nitrogen (2.3 cu.m/h), partial condensation of this mixture at +5 C to remove liquid fraction, and absorption from vapor fraction by white spirit at Ц25 C. EFFECT: increased purity of product. 10 cl, 1 tbl