Di:aryl carbonate preparation by simple process without using phosgene

摘要

Preparation of a diaryl carbonate of formula ArO-CO-OAr (I) comprises preparing (A) a dialkyl carbonate of formula RO-CO-OR (II) by reacting urea with an alkyl alcohol of formula ROH (III); (B) an alkyl aryl carbonate of formula (IV) and (I) by reacting (II) with an aromatic hydroxyl compound of formula ArOH (V); and (C) (I) by disproportionation of unreacted RO-CO-OAr (IV) from stage (B); (where R = alkyl; Ar = phenyl, optionally substituted by an alkyl, alkoxy, aryl or aryloxy group or halogen). Preferably catalysts are used in all stages. (III) formed as by-product in stage (B) is recycled to stage (A). Before use as starting material in stage (B), (II) from stage (A) is purified by: (i) distillation; (ii) separation by cooling to -40 to 20 deg C; or (iii) contact with water at 60-100 deg C. The reaction pressure is lower in stage (C) than in (B). An oxide, alkoxide, aryloxide or alkyl-substituted metal oxide, adduct with another compound or mixture containing at least one of these compounds is used in each stage. he alkyl-substituted metal oxide is a zinc (Zn), copper, lead, tin (Sn) or titanium (Ti) compound in stage (A) and a Sn or Ti compound in stages (B) and (C). Especially suitable catalysts are R'2SnO, R'2Sn(OR)2 and Sn(OR)4, adducts and mixtures in all stages and also ZnO in stage (A) and Ti(OX)4 in stages (B) and (C); R' = 1-10 C alkyl; R" = 3-6 C alkyl; X = 3-6 C alkyl or aryl.