Phthalic anhydride treatment in the presence of hbr in an aluminum vessel

摘要

Phthalic anhydride is both recovered from a reaction mixture containing phthalic anhydride, hydrogen bromide and water vapour, and refined, in an apparatus the surfaces of which comprise aluminium or an alloy thereof in which aluminium is the major constituent. Specified aluminium alloys are those containing Mn, Mg, Si, Ni, Cr, Ti, Cu or Zn. The recovery apparatus may comprise a condenser for liquifying or solidifying phthalic anhydride from the product gases which result from the oxidation of o-xylene with O2 containing gas in the presence of a bromine promoter. The refining apparatus may comprise a distillation apparatus. The recovery and refining processes are preferably carried out under conditions in which no substantial amount of free liquid water containing HBr comes into contact with said surfaces.