Organic compounds -- part of the class 532-570 series – Organic compounds – Nitrite esters or chalcogen analogues thereof
Reexamination Certificate
1998-10-21
2001-02-20
Higel, Floyd D. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitrite esters or chalcogen analogues thereof
Reexamination Certificate
active
06191302
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing an alkyl nitrite. More particularly, the present invention relates to a process for producing an alkyl nitrite by reaction of nitrogen oxide with an alkyl alcohol with high efficiency and high industrial stability, while effectively removing the resultant heat generated by the reaction.
The alkyl nitrite produced by the process of the present invention is useful for the production of a dialkyl oxalate by reaction of the alkyl nitrite with carbon monoxide or production of a dialkyl carbonate from the alkyl nitrite by a non-phosgene method.
2. Description of the Related Art
As methods for producing nitrite esters, Japanese Examined Patent Publication No. 61-6,057 and No. 61-26,977 disclose preparation of methyl nitrite by reacting an alcohol with nitrogen oxide in the gas phase in a production process of dimethyl oxalate, and Japanese Examined Patent Publication No. 62-47,867 and No. 63-35,617 and Japanese Unexamined Patent Publication No. 6-25,104 disclose preparation of nitrite esters by reaction of alcohols with nitrogen oxide in a gas phase.
In the reaction of a lower alkyl alcohol, for example, methyl alcohol, with a nitrogen oxide gas containing, as a principal component, nitrogen monoxide, however, a large amount of heat of reaction is generated in accordance with the following reaction:
NO+ROH+¼·O
2
→RONO+½H
2
O
Accordingly, to prepare the nitrite ester in a high yield at a high degree of safety, it is important that the reaction temperature be closely controlled within an appropriate temperature range, and a reckless run of the reaction due to the reaction heat be prevented. However, the above-mentioned prior publications are completely silent as to concrete means for removing the reaction heat and for appropriately controlling the reaction temperature, and therefore the industrial production of nitrite esters by the above-mentioned prior art was very difficult.
In Japanese Unexamined Patent Publication No. 6-298,706, it is described that the reaction heat can be removed and the reaction temperature can be controlled by injecting an alcohol liquid into a reaction region in which the nitrite ester is produced, to remove the reaction heat by a latent evaporation heat of the alcohol.
In the removal method of reaction heat in accordance with Japanese Unexamined Patent Publication No. 6-298,706, however, the reaction temperature may not always be controlled in the production of the nitrite ester, or the above-mentioned reaction may not be appropriately and fully maintained. Therefore, the production of the nitrite ester was very difficult to effect on an industrial scale and with a satisfactory reproducibility. Japanese Unexamined Patent Publication No. 1-121,251 discloses a process for producing an alkyl nitrite, and a reaction vessel for the process. In this process, a nitrite ester (an alkyl nitrite) is produced by reacting nitrogen oxide with a lower alcohol and oxygen in a reaction region including at least two sections, namely a reaction section in which a gas/liquid contact procedure and a cooling procedure are carried out, and a refining section in which a vapor-residing time long enough to enhance the conversion of oxygen be obtained and a refining capacity large enough to reduce the contents of water and nitric acid in the reaction gas.
Further, Japanese Unexamined Patent Publication No. 1-121,251 discloses concrete means for removing heat from the reaction vessel, namely, a means for withdrawing a liquid side flow from a lower packing section, a means for cooling the liquid side flow, and a means for returning the liquid side flow into the reaction vessel.
The process and apparatus of Japanese Unexamined Patent Publication No. 1-121,251 is disadvantageous in that even when the above-mentioned cooling means is used and the reaction of nitrogen oxide with an alcohol is carried out, although the removal of the reaction heat can be effected with a certain extent, the nitrite ester cannot be obtained in a high yield with a satisfactory degree of stability, and/or by-products, for example, nitric acid, are produced in a large amount, and thus the above-mentioned reaction cannot be stably carried out with a high efficiency.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for producing an alkyl nitrite by reacting an alkyl alcohol with nitrogen oxide gas containing nitrogen monoxide, in which process, the alkyl nitrite-producing reaction can be maintained at an appropriate condition, and the reaction temperature can be controlled to an appropriate level by removing the reaction heat with a high efficiency, and thus various problems which occur in conventional process can be prevented.
The above-mentioned object can be attained by the process of the present invention for producing an alkyl nitrite. The process of the present invention comprises the steps of:
(1) feeding an alkyl alcohol liquid into an upper section of a distillation column reactor in which the upper section is connected to a lower section having a bottom portion in which a liquid bottom fraction containing the alkyl alcohol is accumulated, while allowing the alkyl alcohol liquid feed to flow downward through the upper and lower sections;
(2) circulating the alkyl alcohol-containing liquid fraction through a circulating path through which the liquid bottom fraction is withdrawn from the bottom portion of the lower section of the distillation column reactor, the withdrawn liquid fraction is cooled, and then the cooled liquid fraction is returned into an upper portion of the lower section of the distillation column reactor, thereby to cause the returned liquid fraction to flow downward through the lower section of the distillation column reactor;
(3) introducing a feed gas containing nitrogen oxide into the lower section of the distillation column reactor, while allowing the fed feed gas to flow upward through the lower section of the distillation column reactor, and to come into countercurrent contact with the alkyl alcohol liquid and the alkyl alcohol-containing liquid fraction flowing downward through the lower section, whereby a gas-liquid reaction of the nitrogen oxide in the feed gas with the alkyl alcohol is effected in the lower section to produce an alkyl nitrite; and
(4) delivering a resultant gas fraction containing the alkyl nitrite from the distillation column reactor, wherein
(a) the total amount of the liquid fraction circulating through the lower section of the distillation column reactor is controlled to a level of 50 to 200 times the total amount of the alkyl alcohol fed into the distillation column reactor;
(b) the total molar amount of the alkyl alcohol fed into the distillation column reactor and the alkyl alcohol contained in the liquid fraction circulating through the lower section of the distillation column reactor is controlled in a molar ratio of 20:1 to 150:1 to the molar amount of nitrogen oxide contained in the feed gas fed into the lower section of the distillation column reactor; and
(c) the content of the alkyl alcohol in the liquid bottom fraction accumulated in the bottom portion of the distillation column reactor is maintained at a level of 15 to 60% by weight.
In the process of the present invention, the feed gas for the distillation column reactor may be supplied from a process for producing an alkyl oxalate in which carbon monoxide and an alkyl nitrite are reacted in the presence of a catalyst in a reactor to produce a gas fraction containing a dialkyl oxalate; the resultant gas fraction is fed into an absorption column in which the gas fraction is brought into contact with an absorption liquid comprising an alkyl alcohol, to produce a condensed liquid fraction containing the dialkyl oxalate absorbed in the alkyl alcohol-containing absorption liquid and a non-condensed gas fraction containing a vapor of the alkyl alcohol and gaseous nitrogen monoxide; and the non-condensed gas fraction is deli
Nishihira Keigo
Tanaka Shuji
Yoshida Shin'ichi
Burgess, Ryan & Wayne
Higel Floyd D.
Moran William R.
Sackey Ebenezer
Ube Industries Ltd.
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