Chemistry of inorganic compounds – Carbon or compound thereof
Patent
1998-12-17
2000-04-25
Griffin, Steven P.
Chemistry of inorganic compounds
Carbon or compound thereof
4234151, 423416, 423439, 423440, 562840, 562847, C01B 3100, C01B 3128, C01B 3136, B01J 27224
Patent
active
060541075
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for the manufacture of phosgene by the reaction of chlorine (Cl.sub.2) with carbon monoxide (CO) in the presence of a 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, needs to be evaluated on the basis of the total world-wide production of phosgene which is 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.
A Japanese patent publication (Kokoku) Patent No. Hei 6[1994]-29129 discloses that the amount of carbon tetrachloride produced during the phosgene manufacturing process can be reduced by about 50% to about 150 ppm by weight 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 shown to have both significant 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.
Silicon carbide has long been known as a material which has high thermal and chemical stability, has excellent heat and electrical conducting properties and as an abrasive which is almost as hard as diamond. Silicon carbide can be commercially prepared electrochemically using the Acheson process. The product so produced has a surface area of less than 1 m.sup.2 /g; its use as a catalyst support has been limited partly because of this low surface area. Recently, high surface area (60 to 400 m.sup.2 /g) silicon carbides have been prepared (M. J. Ledoux et al., J. Catal., 114, 176-185 (1988)). These high surface area materials are used as catalyst supports or carriers.
SUMMARY OF THE INVENTION
A process for producing phosgene is provided which comprises contacting a mixture comprising carbon monoxide and chlorine at a temperature of about 300.degree. C. or less. with a catalyst comprising silicon carbide and having a surface area of at least 10 m.sup.2 .multidot.g.sup.-1.
DETAILED DESCRIPTION
The present invention relates to improving the production of phosgene produced by contacting carbon monoxide and chlorine. Surprisingly, we have found that silicon carbide itself can be used as a catalyst for the manufacture of phosgene. The improvement can be employed in connection with the operating conditions used for any of the carbon-based processes previously used commercially or described in the art (e.g., those processes disclosed in U.S. Pat. Nos. 4.231,959 and 4,764,308 for the production of phosgene).
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 added in at least a stoichiometric amount (often in stoichiometric excess) to minimize the free chlorine content of the product phosgene.
The reaction temperature and the silicon carbide are chosen to provide phosgene which contains about 300 ppm or less by weight of carbon tetrachloride. Preferably, the phosgene contains less than about 250 ppm or less by weight of carbon tetrachloride; most preferably, the phosgene contains less than about 100 ppm or less by weight of carbon tetrachloride.
Any silicon carbide-containing catalyst with a surface area greater than about 10 m.sup.2 /g (e.g., about 20 m.sup.2 /g, or more) may be used in the process of this invention. However, silicon carbide compositions having surface
REFERENCES:
patent: 4231959 (1980-11-01), Obrecht
patent: 4764308 (1988-08-01), Sauer et al.
patent: 4914070 (1990-04-01), Ledoux et al.
Sato Kyoichi, Production of Phosgene, Abstract 63156040, Jan. 10, 1990.
Derwent Publications Ltd., Abstract JP 09 059 012A, Mar. 4, 1997.
Marc J. Ledoux et al., New Synthesis and Uses of High-Specific-Surface SiC as a Catalytic Support that is Chemically Inert and Has High Thermal Resistance, Journal of Catalysis, 114, 176-185, 1988.
Cicha Walter Vladimir
Manzer Leo Ernest
E. I. Du Pont de Nemours and Company
Griffin Steven P.
Nave Eileen E.
LandOfFree
Phosgene manufacturing process does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Phosgene manufacturing process, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Phosgene manufacturing process will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-991103