Recovery of catalyst systems from diaryl carbonate-containing reaction solutions by suspension crystallization
AssigneeBayer Aktiengesellschaft
InventorsHans-Josef Buysch, Carsten Hesse, Johann Rechner, Hans-Peter Wirges
Life of this patent
Estimating the term…
Abstract
Catalyst systems with a content of a platinum-group-metal catalyst, a co-catalyst, a quaternary salt and a base for the oxidative carbonylation of aromatic hydroxy compounds to the corresponding diaryl carbonates are according to the invention obtained as a mother liquor by suspension crystallization and can be returned into the carbonylation reaction or worked up to valuable materials. The crystallizate, which consists predominantly of diaryl carbonate and the parent aromatic hydroxy compound, is worked up to pure diaryl carbonate and pure hydroxy compound.
Claims7
A method for recovering catalyst systems containing a platinum-group-metal catalyst, a co-catalyst, a quaternary salt and a base from a reaction solution for producing diaryl carbonates of the formula
- R--O--CO--O--R (I)
- by oxidative carbonylation of the parent aromatic hydroxy compounds of the formula
- R--O--H (II),
- wherein in the formulae
- R signifies substituted or non-substituted C.sub.6 -C.sub.15 -aryl,
- and having a diaryl carbonate content of 20 to 70 wt %, relative to the total weight of the reaction solution, wherein
- a) the reaction solution is transferred from a reactor for producing the diaryl carbonate into an apparatus suitable for suspension crystallization,
- b) the suspension crystallization is initiated in said suitable apparatus by temperature reduction to form a crystallizate,
- c) said crystallizate, which consists predominantly of diaryl carbonate and the parent aromatic hydroxy compound, is separated from residual catalyst-containing mother liquor, said separated crystallizate is washed with a water-free wash solution comprising the aromatic hydroxy compound or a mixture of diaryl carbonate and aromatic hydroxy compound, and the wash solution is recycled into the production of diaryl carbonate,
- d) said crystallizate is worked up to pure diaryl carbonate and pure aromatic hydroxy compound, and
- e) said catalyst-containing mother liquor is recycled into said reactor for producing diaryl carbonate or is worked up to recover said platinum-group-metal catalyst.
Dependencies are inferred from the claim text.