Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1998-07-08
2001-03-27
Stockton, Laura L. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C585S025000, C585S469000
Reexamination Certificate
active
06207866
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a method for producing diarylmethane or its derivatives which are useful as high boiling point aromatic solvents and intermediate compounds for producing various kinds of chemical substances. More particularly, the invention relates to a method for producing diarylmethane or its derivatives from easily available compounds of simple structure such as alcohol, formaldehyde and aromatic compounds.
(2) Prior Art
As the methods for producing the diarylmethane, it is proposed to condense aromatic compounds with several condensing agents. For example, it is proposed that various condensing agents such as halogenated hydrocarbon, formaldehyde or its aqueous solution as formalin are condensed with aromatic compounds in the presence of a catalyst.
A method to use formaldehyde or its aqueous solution of formalin as a condensing agent is preferable because they are inexpensive. In this method, water is generated as a result of condensation. So that, it is not desirable because a by-product water sometimes impairs the activity of acid catalyst or it dilutes the catalyst. For example, in the methods disclosed in J. Frederic Waker, FORMALDEHYDE, 3rd Ed.; U.S. Pat. Nos. 3,043,886; and 2,981,765; and Japanese Laid-Open Patent Publication No. 2-134332, the condensation reaction of aromatic hydrocarbons is carried out using formaldehyde as a condensing agent and sulfuric acid or aluminum chloride as a catalyst. In examples in the above disclosure, when a catalyst such as sulfuric acid or aluminum chloride is used, the subsequent treatment for used catalyst is difficult, in addition, even when adequate reaction conditions are employed, highly condensed products having three or more benzene rings are undesirably produced in addition to an intended product.
The reaction of condensation using a condensing agent of formaldehyde and a solid acid catalyst of zeolite is disclosed in Applied Catalysis, 51, 113-115 (1989); U.S. Pat. Nos. 4,011,278; 4,306,106; 4,476,330; and 4,895,988; and Japanese Laid-Open Patent Publication No. 1-180835. In the reaction disclosed in these references, although the dilution of catalyst owing to by-product water is not caused because solid acid catalysts are used, the lowering of catalytic activity cannot be avoided. Furthermore, the condensation using a condensing agent of formalin as an aqueous solution of formaldehyde in the presence of zeolite catalyst is disclosed in the foregoing U.S. Pat. No. 4,895,988 and Japanese Laid-Open Patent Publication No. 1-180835. In these cases, the catalytic activity is not satisfactory because the condensation is done in the presence of water from the beginning stage. Accordingly, in these examples, the condensation of reactive phenol is mainly done.
Furthermore, several methods of condensation using halogenated hydrocarbons as condensing agents are well known in the prior art. Some of them are put into industrial practice. The by-products of halogenated hydrocarbons have not especially undesirable influence on the condensation reaction. However, the method involves several problems caused by the by-product hydrogen halide, such as the troubles in after-treatment, remained chlorine in the obtained product, and corrosion of apparatus. Furthermore, the problem concerning the polyhalogenated aromatic compounds produced by side reactions is posed recently.
In view of the above-described state of prior art to produce the diarylmethane which is useful as high-boiling aromatic solvents and as intermediates for various kinds of chemical products, it is eagerly wanted to propose an industrially workable method for synthesizing diarylmethane without difficulty and on a high yield using a novel condensing agent.
By the way, it is to be noted that the term “condensing agent” herein referred to means one of reactants used in the condensation reaction and it is bifunctional in the condensation. With its bifunctional property, it can couple two molecules of aromatic hydrocarbon of the other reactant in the condensation. The number of functional groups in an aromatic hydrocarbon in the condensation reaction basically corresponds to the number of hydrogen atoms connected to the benzene ring. However, all the hydrogen atoms on the benzene ring have not always the same reaction characteristics because of the orientation.
BRIEF SUMMARY OF THE INVENTION
The present inventors have found that when acetal, such as dimethoxymethane, is used as a condensing agent, a by-product of alcohol is formed in place of the by-product of water in the condensation reaction, in which formaldehyde is used as a condensing agent. As a result, it has been made possible to carry out the reaction system of condensation substantially without the existence of water. Accordingly, it is possible to avoid the occurrence of the above discussed deterioration of catalyst and the lowering of catalyst concentration.
Furthermore, when acetal is used as a condensing agent, a by-product of alcohol is produced. However, if the alcohol is discarded, the use quantity of alcohol is inevitably increases to raise undesirably the cost for the raw material. This problem has also been solved in the present invention. In other words, when acetal is synthesized from formaldehyde and alcohol, the by-product of alcohol in the condensation reaction can be recycled to the process of acetal synthesis, thereby enhancing economical efficiency. The acetal, e.g., dimethoxymethane (methylal) does not form substantially an azeotropic mixture with water. Accordingly, it is possible to separate easily the produced acetal from by-product of water which is produced in the synthesis of acetal from formaldehyde and alcohol. As a result, it is possible to recover acetal of low water content and to carry out the condensation reaction under the condition substantially without the existence of water. In view of this advantage, it is desirable to synthesize acetal from formaldehyde and alcohol.
Accordingly, the principal object of the present invention is to provide an improved method for efficiently producing diarylmethane and its derivatives using a condensing agent through a simplified process without suffering the deterioration of catalyst.
Another object of the present invention is to provide a method for easily producing diarylmethane and its derivatives using inexpensive reactants.
A further object of the present invention is to provide a method for easily producing diarylmethane and its derivatives in high yield by recovering and recycling the by-product in the condensation process.
Accordingly, the method for producing diarylmethane and its derivatives in the present invention is characterized in that dimethoxymethane and an aromatic compound are reacted together at a reaction temperature in the range of 80 to 400° C. in the presence of an acid catalyst.
Preferable example of diarylmethane and its derivatives produced in the present invention are represented by the following general formula [I]:
wherein m is an integer from 0 to 3, n is 1 or 2 and R is independently hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a hydroxyl group.
The method for producing diarylmethane and its derivatives comprises the following steps (1) to (4) using starting materials of alcohol, formaldehyde and aromatic compound:
(1) reacting alcohol with formaldehyde in the presence of an acid catalyst to obtain acetal;
(2) reacting the acetal and an aromatic compound in the presence of an acid catalyst to obtain a reaction mixture containing diarylmethane or its derivatives and alcohol;
(3) separating and recovering diarylmethane or its derivatives, and alcohol, respectively, from the reaction mixture containing diarylmethane or its derivatives and alcohol; and
(4) recycling at least a portion of the recovered alcohol to the above-mentioned step (1) to obtain acetal.
It is possible to use an aqueous solution of formaldehyde, i.e., formalin, in place of the formaldehyde itself to be used in the above step (1). In such a case, because much wat
Dohi Hideyuki
Hayashi Shozo
Inoue Satoru
Kawamata Tadanori
Nippon Petrochemicals Company Limited
Stockton Laura L.
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