Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By condensation of entire molecules or entire hydrocarbyl...
Reexamination Certificate
2000-04-19
2001-07-03
Knode, Marian C. (Department: 1764)
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By condensation of entire molecules or entire hydrocarbyl...
C585S422000, C585S455000, C585S456000
Reexamination Certificate
active
06255549
ABSTRACT:
DESCRIPTION
1. Technical Field
This invention relates to a method for producing low bromine number fraction mainly containing styrenic compound/aromatic compound adduct that is obtained by adding a styrenic compound to an aromatic compound.
2. Background Art
The styrene/alkylbenzene adduct is used as solvents for carbonless copy paper or for other purposes such as electrically insulating oil. The method for preparing a styrene/alkylbenzene adduct by adding styrene to alkylbenzene in the presence of a solid acid catalyst in a liquid phase, is proposed in U.S. Pat. No. 4,144,279; Japanese Laid-Open Patent Publication No. S55-24145 and U.S. Pat. No. 4,289,918.
According to experiments carried out by the inventors of the present application, when the addition reaction of styrene compound to alkylbenzene in the presence of a solid acid catalyst in a liquid phase was continued for a long period of time, it was observed that the bromine number of reaction product containing the adduct besides styrene compound increases. In this process, even when the bromine number was varied, the degree of conversion itself of styrene compound did not change largely almost on the same level. It is natural to consider that the reason for the increase in bromine number exists in the change in catalytic activity and the reaction among styrene molecules, rather than in the deterioration of catalyst.
The styrene/alkylbenzene adduct itself is a compound having no unsaturated double bond, however, the fact that the bromine number (JIS K 2605) of a fraction mainly containing this compound is high means that the content of unsaturated double bonds in reaction product is large. The double bonds are liable to cause oxidation and deterioration, so that the use of reaction product as a solvent is not desirable and it is wanted to find out to cope with this problem.
DISCLOSURE OF INVENTION
A first aspect of the present invention relates to a method for producing a fraction of low bromine number, which mainly contains a styrenic compound/aromatic compound adduct, by feeding reaction materials of a styrenic compound and an aromatic compound having at least one hydrogen atom directly connected to the carbon atom of aromatic ring, to a fixed-bed flow reactor packed with a solid acid catalyst in a liquid phase at a temperature in the range of 40 to 350° C. to form a styrenic compound/aromatic compound adduct and obtaining a fraction mainly containing the above adduct by distillation, wherein
the feed of reaction materials is stopped when the bromine number of the above fraction is increased up to a predetermined value relative to an initial value,
after that, in place of the reaction materials, a saturated aromatic hydrocarbon having a mean value of the proportion of aromatic ring carbons relative to total carbons in a molecule of 55% or more is fed to the reactor in a liquid phase at a temperature higher by 5 to 150° C. than that of the reaction mixture just before the above stopping of feed of reaction materials, and
then the feed of reaction materials is restarted to carry out the foregoing reaction so as to obtain a fraction of low bromine number.
A second aspect of the present invention relates to the method of producing a low bromine number fraction as described in the first aspect of the invention, in which the aromatic compound is benzene, toluene, xylene, ethylbenzene, cumene or a mixture of them.
A third aspect of the present invention relates to the method of producing a low bromine number fraction as described in the first and second aspect of the invention, in which the styrenic compound is styrene, &agr;-methylstyrene or p-methylstyrene.
In accordance with the method of the present invention, it is possible to produce a fraction of low bromine number with a convenient method to use saturated aromatic compounds.
In the following, the present invention will be described in more detail.
In the aromatic compound as a raw material for the present invention, at least one hydrogen atom is connected to the carbon atom of non-condensed or condensed benzene ring. More particularly, it is exemplified by alkylbenzenes such as benzene, toluene, xylene, ethylbenzene, cumene, trimethylbenzene, ethyltoluene, diethylbenzene and butylbenzene; naphthalenes such as naphthalene and methylnaphthalene; biphenyls such as biphenyl and methyl-biphenyl; diarylalkanes such as diphenylmethane and diphenylethane; phenols such as phenol and cresol; and their mixtures.
The styrenic compound used as another kind of raw material in the present invention is exemplified by styrene, &agr;-methylstyrene or p-methylstyrene. The method of the present invention is effective in addition reaction using a styrenic compound, however, it is not effective in the similar reaction using a halogenated compound or alcohol.
The addition reaction of styrenic compound and the above aromatic compound must be done in a liquid phase in the range of 40 to 350° C. In other words, the reaction in a vapor phase or at a temperature below 40° C. or above 350° C. is not effective because the effect to reduce the bromine number cannot be attained, and it rather contaminates reaction system, undesirably.
The pressure of reaction may be a value sufficient to maintain the reaction phase in a liquid state. In general, it can be selected from the range of 0.1 to 10 MPa. The value of WHSV (mass flow rate/mass of filled catalyst) is selected from the range of 0.1 to 500 h
−1
.
As the reactor, a flow type one having a fixed bed of solid acid catalyst can be used. It is possible to provide it with an optional heating device such as an apparatus to circulate a heating medium. The reactor may be any of single tube reactor and multi-tube reactor.
After reaction, a fraction that contains main component of styrenic compound/aromatic compound adduct is obtained by the distillation of reaction mixture taken out from the reaction system. For example, when o-xylene is added to styrene, a fraction mainly containing styrene/o-xylene adduct can be obtained. The distillation to obtain the above fraction may be any of industrially adopted methods. The specific distillation such as rectification is not desirable because it causes the increase in production cost.
As described above, the bromine number of the fraction mainly containing styrenic compound/aromatic compound adduct increases with the progress of reaction.
In the present invention, the bromine number of the above fraction is measured and the reaction is once stopped when the bromine number of the reaction mixture is increased up to a predetermined value as compared with its initial value. The upper limit of the bromine number can be determined in accordance with several conditions such as the kind of catalyst, the bromine number required of intended product, and so forth. However, when the bromine number exceeds 3 g/100 g, it is difficult to reduce the bromine number even when the method of the present invention is employed. Therefore, it is necessary to carry out the series of treatment by stopping the reaction before the bromine number increases up to 3 g/100 g.
In other words, when the bromine number is increased, the feed of raw materials is once stopped and, after that, a saturated aromatic hydrocarbon is fed to the reactor in place of the raw materials, and they are passed through the reactor and brought into contact with a solid acid catalyst. By the way, it is possible to operate the reaction as if it looks like continued, by carrying out continuously the first stage reaction and the feed of saturated aromatic hydrocarbon. In other words, the reaction between the above aromatic compound and styrene are cause to proceed to some extent, meanwhile the saturated aromatic hydrocarbon is fed, so that the once increased bromine number is reduced.
In one molecule of saturated aromatic hydrocarbon herein used, the proportion of the carbon atom number of aromatic ring relative to the total carbon atom number is 55% or more and it does not have ethylenically unsaturated double bonds. More particularly, it is exemplified by alky
Dohi Hideyuki
Hayashi Shozo
Dang Thuan D.
Hollander Law Firm, P.L.C.
Knode Marian C.
Nippon Petrochemicals Company Limited
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