METHOD OF PRODUCING HIGHLY CONCENTRATED METHYLAL Russian patent published in 2011 - IPC C07C43/303 C07C41/56 C07C41/50 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing highly concentrated methylal from formaldehyde and methanol via a reaction-fractionation method involving preliminary mixing of aqueous solution of formaldehyde and methanol, feeding the obtained mixture into a pre-reaction zone, followed by feeding the mixture of unreacted initial reagents, the formed methaylal and water into a fractionation column, having a reaction-fractionation zone lying above the fractionation column still, feeding an extraction agent into the fractionation zone of the column lying above the reaction-fractionation zone, condensing a product containing over 98 wt % methylal tapped from the top of the column, cleaning the methylal from impurities, characterised by that methanol is fed for preliminary mixing in amount of 95-50% of the amount required for implementing the method, and the remaining portion of methanol in amount of 5-50% of the amount required to implement the method is fed into the fractionation column below the reaction-fractionation zone and purification of methylal is carried out via azeotropic rectification with isopentane which is fed in amount of 15-50% in terms of the amount of the purified methylal, with extraction of the desired methylal as a bottom product, and the top product in form of the mixture of isopentane primarily with methylal, methanol and water, followed by condensation and demixing the top product into hydrocarbon and water layers, returning a portion of the hydrocarbon layer into the azeotropic rectification column as reflux liquid, and the remaining portion of the hydrocarbon layer is fed into this column and the water layer is returned into the fractionation column below the reaction-fractionation zone.

EFFECT: use of present method reduces the number of steps of purifying methylal from impurities and reduces residual content of methanol and formaldehyde in residual water.

4 cl, 4 ex, 1 dwg