Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-05-31
2001-07-10
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06258923
ABSTRACT:
The present application is a U.S. non-provisional application based upon and claiming priority from Japanese Application No. HEI 11-165585, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a dialkyl carbonate, and more particularly relates to a method for efficiently manufacturing a dialkyl carbonate from CO, O
2
, and an alcohol.
Because of their excellent impact resistance and other mechanical properties, as well as their excellent heat resistance, transparency, and so on, aromatic polycarbonates have come to be used as engineering plastics in a wide range of fields in recent years.
One method for manufacturing these aromatic polycarbonates that has been put to industrial use is a so-called phosgene process, in which an aromatic dihydroxy compound such as bisphenol is reacted with phosgene by interfacial polycondensation. Unfortunately, numerous problems with this method have been indicated, e.g., extremely toxic phosgene must be used, there is the question of what to do with the large quantity of by-product sodium chloride, and the methylene chloride that is normally used as a reaction solvent can pose health and atmospheric pollution problems.
One known method for manufacturing an aromatic polycarbonate besides the phosgene process is a method (melt method) in which an alkali metal compound such as sodium hydroxide is used as a catalyst in an ester exchange reaction between an aromatic dihydroxy compound and a carbonic diester. This method has garnered attention of late because it has the advantage of allowing an aromatic polycarbonate to be manufactured at lower cost, and it is preferable in terms of environmental safety since it does not involve the use of toxic substances such as phosgene or methylene chloride.
A diaryl carbonate such as diphenyl carbonate is used as the carbonic diester in the manufacture of a polycarbonate by this melt method. As discussed in Japanese Laid-Open Patent Application H9-194430, this diaryl carbonate is manufactured by an ester exchange reaction between a dialkyl carbonate and a hydroxyl group-containing hydrocarbon such as phenol. The dialkyl carbonate that serves as a raw material for this diaryl carbonate is manufactured from carbon monoxide, oxygen, and an alcohol, using a catalyst composed of a cupric halide such as cupric chloride.
For example, when methanol is used as the alcohol, dimethyl carbonate is manufactured by the following reaction.
2CH
3
OH+CO+1/2O
2
→(CH
3
O)
2
CO+H
2
O
The cupric chloride used as the catalyst here is surmised to form cupric methoxychloride by a primary reaction:
2CuCl+2CH
3
OH+1/2O
2
→2Cu(OCH
3
)Cl+H
2
O
and to be regenerated by a secondary reaction:
2Cu(OCH
3
)Cl+CO→(CH
3
O)
2
CO+2CuCl.
The addition of a hydrohalic acid to the reaction system in order to improve the catalytic activity of the cupric halide used as the catalyst has been disclosed (see Japanese Laid-Open Patent Application H5-194327).
Nevertheless, with a method in which a cupric halide is used as a catalyst as above, the conversion rate at which the above-mentioned cupric alkoxychloride is formed is so low that the yield of the resulting dialkyl carbonate is not necessarily adequate, and furthermore some catalysts can clog the reaction tank and pipes, which is a problem in terms of manufacturing efficiency.
In light of this situation, the inventors conducted diligent investigation into a method for manufacturing a dialkyl carbonate more efficiently, and arrived at the present invention upon discovering that when
(i) a cupric halide and
(ii) a compound capable of producing a copper halide alkoxide by reaction with a cupric halide are used together as a catalyst, the reaction proceeds in a state of sustained high catalytic activity, there is no clogging of the reaction tank and pipes by the catalyst, and a carbonic diester is obtained at a high yield.
The present invention was conceived in light of the above prior art, and it is one goal thereof to provide a method for efficiently manufacturing a dialkyl carbonate from CO, O
2
, and an alcohol.
SUMMARY OF THE INVENTION
The method for manufacturing a dialkyl carbonate pertaining to the present invention is characterized in that a catalyst composed of:
(i) a cupric halide; and
(ii) a compound capable of producing a copper halide alkoxide by reaction with a cupric halide
is used in the manufacture of a dialkyl carbonate using carbon monoxide, oxygen, and an alcohol as starting raw materials.
The above-mentioned (ii) compound capable of producing a copper halide alkoxide by reaction with a cupric halide is preferably at least one type of compound selected from the group consisting of alkali metal alkoxides, alkaline earth metal alkoxides, quaternary ammonium alkoxides expressed by the following formula (1), and quaternary phosphonium alkoxides expressed by the following formula (2).
R
1
R
2
R
3
R
4
NOR
5
(1)
R
1
R
2
R
3
R
4
POR
5
(2)
(Where R
1
to R
4
may be the same as or different from each other, and are each a hydrogen atom or a C
1
to C
20
hydrocarbon group, and R
5
is a C
1
to C
20
hydrocarbon group.)
With the present invention, this (ii) compound capable of producing a copper halide alkoxide by reaction with a cupric halide is used in an amount of 0.05 to 2.0 mol with respect to the cupric halide.
Methanol is a preferred alcohol used in the method for manufacturing a dialkyl carbonate pertaining to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The method for manufacturing a dialkyl carbonate pertaining to the present invention will now be described in specified terms.
First, the starting raw materials and catalysts used in the method for manufacturing a dialkyl carbonate pertaining to the present invention will be described.
Starting Raw Materials and Catalysts
CO, O
2
, and an alcohol are used as the starting raw materials in the present invention.
There are no particular restrictions on the alcohol used as a starting raw material, but examples include methanol, ethanol, propanol, butanol, isopropanol, isobutanol, and hexanol. Of these, the use of methanol is preferred.
The catalysts in the present invention are (i) a cupric halide and (ii) a compound capable of producing a copper halide alkoxide by reaction with a cupric halide.
Examples of the (i) cupric halide include cupric chloride, cupric fluoride, cupric bromide, and cupric iodide. Of these, the use of cupric chloride is preferred.
One or more types of compound selected from the group consisting of alkali metal alkoxides, alkaline earth metal alkoxides, quaternary ammonium alkoxides expressed by the following formula (1), and quaternary phosphonium alkoxides expressed by the following formula (2) can be used favorably as the (ii) compound capable of producing a copper halide alkoxide by reaction with a cupric halide.
R
1
R
2
R
3
R
4
NOR
5
(1)
R
1
R
2
R
3
R
4
POR
5
(2)
(Where R
1
to R
4
may be the same as or different from each other, and are each a hydrogen atom or a C
1
to C
20
hydrocarbon group, and R
5
is a C
1
to C
20
hydrocarbon group.)
Specific examples of alkali metal alkoxides include sodium methoxide, lithium methoxide, potassium methoxide, rubidium methoxide, cesium methoxide, sodium ethoxide, lithium ethoxide, potassium ethoxide, rubidium ethoxide, cesium ethoxide, sodium propoxide, lithium propoxide, potassium propoxide, rubidium propoxide, cesium propoxide, sodium butoxide, lithium butoxide, potassium butoxide, rubidium butoxide, cesium butoxide, sodium pentoxide, lithium pentoxide, potassium pentoxide, rubidium pentoxide, cesium pentoxide, sodium hectoxide, lithium hectoxide, potassium hectoxide, rubidium hectoxide, cesium hectoxide, sodium heptoxide, lithium heptoxide, potassium heptoxide, rubidium heptoxide, cesium heptoxide, sodium octoxide, lithium octoxide, potassium octoxide, rubidium octoxide, cesium octoxide, sodium phenoxide, lithium phenoxide, potassium phenoxide, rubidium phenoxide, and cesium
Kimura Takato
Shimoda Tomoaki
Tanaka Masahide
Boykin Terressa M.
General Electric Company
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