Process for the manufacture of biacetyl-free methyl methacrylate

Details Process for the manufacture of biacetyl-free methyl methacrylate Process for the manufacture of biacetyl-free methyl methacrylate

1995-06-05

1996-12-17

Killos, Paul J.

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C07C 6748

Patent

active

055855148

ABSTRACT:
A process for producing methyl methacrylate comprises: (a) reacting acetone cyanohydrin with sulphuric acid or an oleum, in order to obtain methacrylamide; (b) reacting the methacrylamide thus obtained either directly, or after it has been isolated, with methanol in the presence of water; (c) separating the methyl methacrylate from the sulphuric acid, ammonium sulphate and water mixture by distillation; (d) removing the unreacted methanol by liquid-liquid extraction; (e) distilling the washed methyl methacrylate in two stages: (e1) firstly, in order to remove the remaining traces of water, of methanol and of low-boiling-point impurities; then (e2) in order to separate the pure methyl methacrylate from the high- boiling-point impurities. An improved purification step comprises conducting, step (e) in the presence of at least one non-aromatic 1,2-diamine which is capable of reacting, under acid catalysis, with the biacetyl present as impurity in the methyl methacrylate and of reducing the content thereof, the said non-aromatic 1,2-diamine being introduced at a point such that its contact time with the methyl methacrylate is sufficient for it to be able to react substantially with the biacetyl present.

REFERENCES:
patent: 4304925 (1981-12-01), Watanabe et al.
patent: 4668818 (1987-05-01), Lipp et al.
patent: 5468899 (1995-11-01), Bauer et al.

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