Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic halides
Patent
1998-03-09
2000-02-08
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic halides
C07C 5158
Patent
active
060229934
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for the manufacture of phosgene by the reaction of chlorine with carbon monoxide in the presence of a carbon catalyst. More particularly, this invention relates to a process for the manufacture of phosgene with minimal production of the hazardous chemical, carbon tetrachloride.
BACKGROUND
The production of phosgene by the reaction of chlorine with carbon monoxide in the presence of a carbon catalyst is a well known process. The phosgene produced by this process will typically contain 400 to 500 ppm by weight carbon tetrachloride. This amount, evaluated on the basis of the total world-wide production of phosgene of about ten billion pounds (4.5.times.10.sup.9 kg) corresponds to co-production of about 4 to 5 million pounds (1.8.times.10.sup.6 kg to 2.3.times.10.sup.6 kg) of carbon tetrachloride with the phosgene.
Japanese patent publication (Kokoku) No. Hei 6[1994]-29129 discloses that the amount of carbon tetrachloride produced during the phosgene manufacturing process can be reduced (e.g., by about 50%) by using an activated carbon which has been washed with an acid and which contains a total of 1.5 wt. % or less of metal components comprised of transition metals, boron, aluminum and silicon.
Carbon tetrachloride has been of concern in connection with ozone depletion and global warming potentials. Therefore, there is an interest in developing phosgene processes in which the amount of carbon tetrachloride impurity is minimized.
SUMMARY OF THE INVENTION
A process for producing phosgene is provided which comprises contacting a mixture comprising carbon monoxide and chlorine with carbon. In accordance with this invention, the carbon (1) has an active metal content of less than 1000 ppm by weight, and (2) loses about 12% of its weight, or less, when sequentially heated in air for the following times and temperatures; 125.degree. C. for 30 minutes, 200.degree. C. for 30 minutes, 300.degree. C. for 30 minutes, 350.degree. C for 45 minutes, 400.degree. C. for 45 minutes, 450.degree. C. for 45 minutes and finally at 500.degree. C. for 30 minutes. Typically the contact is at a temperature of about 300.degree. C., or less.
DETAILED DESCRIPTION
The present invention relates to improving the production of phosgene produced by contacting carbon monoxide and chlorine with carbon. The improvement can be employed in connection with any of those carbon-based processes used commercially or described in the art (e.g., those processes disclosed in U.S. Pat. Nos. 4,231,959 and 4,764,308).
Phosgene is commercially manufactured by passing carbon monoxide and chlorine over activated carbon. The reaction is strongly exothermic and is usually done in multitubular reactors to more effectively control the reaction temperature. Carbon monoxide is typically added in at least a stoichiometric amount (often in stoichiometric excess) to minimize the free chlorine content of the phosgene product.
As used in connection with this invention, the term "active metals" means metals included in the group consisting of transition metals of groups 3 to 10, boron, aluminum and silicon. Carbon which contains less than about 1000 ppm by weight of active metals is employed. Iron is considered a particularly harmful active metal (i.e., the greater the amount of iron the larger the amount of carbon tetrachloride produced). It is preferred to use carbons which not only have an active metal content of less than about 1000 ppm by weight, but also contain less than about 100 ppm by weight of iron (and more preferably less than about 80 ppm by weight iron). It is also preferable to use carbons which contain less than 200 ppm by weight of sulfur and less than 200 ppm by weight of phosphorus (and more preferably less than 100 ppm by weight each, of phosphorus and sulfur).
The carbons used for the process of this invention also exhibit substantial weight stability when heated in air. More particularly, when heated in air at 125.degree. C. for 30 minutes, followed by heating at 200.degree. C. for
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Derwent Pub. Ltd., Abstract JP 6029129, Idemitsu Petroleum KK Jun. 25, 1988.
Chemical Abstract No. 65095, p. 673, vol. 94 Apr. 1980.
Cicha Walter Vladimir
Manzer Leo E.
E. I. Du Pont de Nemours and Company
Killos Paul J.
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