Distillation: processes – separatory – Plural distillations performed on same material
Reexamination Certificate
2000-01-11
2001-03-13
Manoharan, Virginia (Department: 1764)
Distillation: processes, separatory
Plural distillations performed on same material
C159SDIG002, C159SDIG002, C203S078000, C203S080000, C210S664000, C210S500270, C210S500380, C549S368000
Reexamination Certificate
active
06200429
ABSTRACT:
The invention relates to a process for isolating trioxane from an aqueous mixture which consists essentially of trioxane, formaldehyde and water.
The preparation of trioxane results in an azeotropic mixture which consists essentially of trioxane, water and formaldehyde. Trioxane is isolated from this mixture by extraction with the aid of an entrainer, eg. chlorine-containing entrainers such as methylene chloride, or benzene. Further components of the mixture in minor amounts are, as a rule, formic acid, methylal and dimethoxydimethyl ether. The entrainer is recovered in a subsequent distillation and is returned to the extractive distillation. It is necessary for large amounts of entrainer to be employed in this process and to be recovered with high energy costs. Emissions which are inevitably produced require elaborate disposal because methylene chloride and benzene are categorized as hazardous substances.
EP-A 596 381 discloses a process for isolating trioxane by removal of water from the azeotropic mixture by pervaporation.
REFERENCES:
patent: 4125540 (1978-11-01), Sugio et al.
patent: 4952319 (1990-08-01), Yanaga et al.
patent: 4983303 (1991-01-01), Uragami
patent: 5061349 (1991-10-01), Kupppenbender et al.
patent: 5523419 (1996-06-01), Arnold
patent: 5767294 (1998-06-01), Steele et al.
patent: 596 381 (1994-05-01), None
Derwent JP 7/033762 A 95 02 03.
Bitterlich Stefan
Freyhof Reinhard
Vandenmersch Hugues
BASF - Aktiengesellschaft
Keil & Weinkauf
Manoharan Virginia
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