Recovery of di:methyl terephthalate and intermediates - from bottom prods. of the crude distn. by oxidn. of xylol and toluic acid and reaction with methanol (BR 22.9.81)

摘要

Recovery of dimethylterephthalate (DMT) and intermediates obtd. as bottom prods. from DMT prodn., is by mutual air oxidn. of p-xylol and p-toluic acid methyl ester in the presence of heavy metal oxidn. catalysts at 140-180 deg.C and 3-11 bar in the liq. phase, followed by esterification of the resulting acids with methanol, recovery of the ester by distn. and removal of the oxidn. catalyst by extn. The high-boiling bottom prods. are now heat-treated at 220-300 deg.C in the presence of 0.02-4 wt.% of a soluble cpd. of Ti, Zr, Mn, Fe, Ni, Zn, Al, Si, B, Ge, Sn or Pb as decomposition catalysts, and recovering the resulting DMT and intermediate prods., then returning the recovered material to the process. Process allows recovery of larger amts. of DMT and intermediate prods. from the crude distn. residues in shorter reaction times and lower temps. than with previous processes. The use of large volume reactors and increased heating units is avoided. Prods. are used as raw material for polyester prodn. for film and fibre making.