METHOD FOR PREPARING FORMALIN Russian patent published in 2004 - IPC

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to technology of organic synthesis, namely, to the improved method for preparing formalin used in chemical industry, medicine and agriculture. Method involves preparing an alcoholic-aqueous-gaseous mixture by the forced evaporation of an aqueous-methanol mixture and it mixing with blowgas, formaldehyde and air followed by overheating and passing through silver catalyst at elevated temperature and the following absorption of prepared reaction gases to form the commercial product - formalin. The parent methanol and blowgas are fed into evaporator being blowgas is removed from bottom of absorption column at temperature 70-100 C and upper part of absorption column where formaldehyde in gaseous phase is added additionally in the amount 0.86-4.3 wt.-% of methanol mass in the mass ratio of the parent methanol to blowgas containing added formaldehyde additionally = 1:(0.6-0.9). Air is fed after preparing an aqueous-methanol-gaseous mixture out of evaporator. Invention provides enhancing quality of preparing formalin and to elevate its concentration, to reduce consumption norms of methanol, to prolong working life of catalyst and to provide explosion-proof of process.

EFFECT: improved preparing method.

1 dwg, 2 ex