Methyl benzoate purificn. to neutral aldehyde-free prod. - comprises heating with acid bleaching earth and then with magnesium methylate and a titanate

摘要

Neutral aldehyde-free Me benzoate, (I), is recovered from crude (I) from dimethyl terephthalate prodn. by: (i) heating the crude (I) with 0.05-0.4 wt.% acid bleaching earth for 0.5-6 hrs. to 130-200 degrees C under normal pressure; (ii) cooling the prod. to 80 degrees C; (iii) adding 0.3-0.8 wt.% Mg methylate and 0.05-0.4 wt.% ester titanate and further heating 1-6 hrs. at 150-200 degrees C under normal pressure and (iv) recovering >=1 (I) fractions having purity >=98 wt.%, as head prod., by distn. at =1 atmos. pressure. (I) obtd. can be (i) used directly as lacquer solvent; (ii) converted by alcoholysis, e.g. with butanol or benzyl alcohol, to carrier cpds. which improve dyeability of polyesters, or (iii) converted by alcoholysis with diglycols, e.g. dipropylene glycol, to form PVC plasticiser. The purified prod. has acid index 0.1 mg KOH/g; has no pungent smell, and is free from aldehydes and ethers.