Process for a rectificative separation of (meth)acrylic acid from a hydrophobic mixture containing crude (meth)acrylic acid

摘要

A process for the sepn. of (meth)acrylic acid (I) from a mixt. contg. (a) (I), (b) inert, hydrophobic organic liq. with a higher b.pt. than (I) as main component and (c) lower aldehydes as minor components, comprises rectification with the addn. of a prim. amine and/or salts thereof (II). Also claimed are processes for the prodn. of (I) by gas-phase oxidn. of a 3C/4C starting material (III). Pref. liq. (b) contains diphenyl ether (DPE), and pref. comprises a mixt. of 70-75 wt.% DPE and 25-30 wt.% biphenyl contg. 0.1-25 wt.% (w.r.t. the mixt.) of dimethyl o-phthalate. Amine (II) is a hydrazine deriv., pref. the hydrazide of a carboxylic acid, esp. pref. adipic acid dihydrazide.