Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic halides
Patent
1999-06-16
2000-04-25
Killos, Paul J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic halides
C07C 5158
Patent
active
060546123
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.
A process for producing phosgene using carbon having an active metal content of less than 1000 ppm and a weight loss of about 12% or less in the WVC temperature test has been described (see U.S. application Ser. No. 60/012,021 and International Application No. PCT/US96/17526).
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 a micropore to macropore ratio of 3.5 or less; (2) loses about 16% 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; and (3) has a surface area of at least 10 m.sup.2 /g. Also, in accordance with this invention, the active metal content of the carbon may be 1000 ppm or more. 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.
The carbon materials useful as catalysts for this invention are porous (i.e., a surface area of at least 10 m.sup.2 /g) and contain both micropores and macropores. As used in connection with this invention, the term "micropore" means a pore size of 20 .ANG. (2 nm) or less and the term "macropore" means a pore size of greater than 20 .ANG. (2 nm). The total pore volume and the pore volume distribution can be determined by mercury porosimetry. The micropore volume (cc/g) is subtracted fro
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Fairley, Dupont Recognizes Leaders, Chemical Week, p. 32, Oct. 2, 1996.
Fairley, Flexibility Drives DuPont CCl.sub.4 Reductions, Chemical Week, p. 58, Oct. 23, 1996.
Boppart et al., Understanding Activated Carbons, Chemical Processing, pp. 79-82, Sep. 1996.
Derwent Abstract re: JP 06 029 129B, Idemitsu Petrochem KK, Apr. 4, 1994.
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Chemical Abstract No. 65095, p. 673, vol. 94 Dec. 26, 1970.
Cicha Walter V.
Manzer Leo Ernest
E. I. Du Pont de Nemours and Company
Killos Paul J.
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