JP2593212B2 - How to make cumene - Google Patents

Description

The present invention relates to a method for alkylating an aromatic compound.
More particularly, it relates to a method for producing cumene. Cumene synthesized by the method of the present invention is a very important compound as a raw material for phenol synthesis.

<Prior Art> Many methods are already known for alkylating an aromatic compound. For example, an alkylation method using olefins is widely performed industrially and is one of important industrial techniques. There are also many proposals for a method of alkylation using alcohols.

As a prior art of an alkylation reaction of an aromatic compound using an alcohol, the following method has been proposed.

(1) A method described in JP-A-58-159430, in which a 1,4-dialkylbenzene compound is produced using an oxide-modified zeolite as a catalyst.

(2) A method described in JP-A-61-263934, wherein p-xylene is produced by alkylating toluene with methanol using ZSM-5 type zeolite as a catalyst.

(3) US Pat. The method described in 159427.

(4) U.S. Patent US Pat. No. 6,028,097 to alkylate various aromatic compounds with alcohols using ZSM-5 type zeolite as a catalyst
The method described in P-4,011,278.

These methods are all proposals for improving the yield of the target alkyl aromatic compound by improving the catalyst.

<Problems to be Solved by the Invention> In an alkylation reaction of an aromatic compound, it is generally difficult to selectively obtain a target compound. That is, since the alkylated product generally has higher reactivity to the alkylation reaction than the starting compound, a further alkylation reaction proceeds to form a higher alkylated product, and thus selective alkylation occurs. Hateful. To that end, there have been many proposals for selective alkylation by improving the catalyst.

In the alkylation reaction of an aromatic compound, the reactivity depends on the acidity of the catalyst and the shape of the catalyst. It is said that the acid nature of the catalyst is responsible for the reaction rate, while the catalyst shape is responsible for the selectivity.

By the way, in the alkylation reaction using alcohols, water is generated. In general, a catalyst having an acidic property usually becomes weak in the presence of water. In particular, when a solid acid is used as a catalyst, the catalyst may sometimes lose its catalytic activity. Therefore, in the case where water is generated, various measures have been taken such as adopting strict reaction conditions to increase the reactivity, or using a water-resistant catalyst.

However, when the reaction conditions are strict or the catalyst is improved, for example, the catalyst is modified into a strongly acidic catalyst, the formation of higher alkylated products as described above, or the by-products of olefins due to dehydration of alcohols, etc. As a result, the selectivity of the target object decreases.

As described above, in the alkylation reaction of an aromatic compound using an alcohol as an alkylating agent, an industrial technique for selectively obtaining a desired reaction product has not been completed.

<Means for Solving the Problems> The present inventors have conducted intensive studies on a method for synthesizing a target compound with high selectivity in a method for producing cumene using an alcohol as an alkylating agent. completed.

The process of the present invention will be described in detail as follows. That is, the present inventors have been studying a method for producing cumene using alcohols, but have not found a catalyst or a reaction condition that can provide cumene with good yield. One of the reasons that cumene cannot be obtained in good yield is
It was found that alcohol was dehydrated in parallel with the alkylation reaction. Although olefins are generated in the dehydration reaction of alcohols, in fact, in the reaction with a low cumene yield, it was found that many olefins were dissolved in the reaction solution.

By the way, in the alkylation reaction of an aromatic compound, it is also known to use an olefin as an alkylating agent.

Thus, as a result of studying a method of using the olefins by-produced in this reaction again for the alkylation, the method of the present invention was found.

That is, in the process of the present invention, in producing cumene by a continuous alkylation reaction of benzene using isopropanol as an alkylating agent, the reaction mixture containing by-produced propylene discharged from the reactor is mixed with B A is divided into two parts, A and B, so that the ratio of A is greater than 1. One A is circulated again to the reactor, and the other B is discharged out of the reaction system as a reaction product mixture, and isopropanol, benzene and A method for producing cumene, characterized in that by supplying an amount of the alkylation raw material liquid corresponding to B, by-products of higher alkylated products are suppressed and the yield is improved.

According to the method of the present invention, isopropanol charged as an alkylation raw material is consumed in the alkylation reaction with a high selectivity, and the rate of conversion to propylene by a side reaction is extremely small. Therefore, the yield of the alkylated product could be improved without difficulty.

Furthermore, surprisingly, according to the method of the present invention, the production of higher alkylated products in the alkylated product is extremely suppressed, and the selectivity of the intended monoalkylated product, cumene, is greatly improved. We have found that unexpected effects appear.

An example of a schematic diagram of a reactor for carrying out the method of the present invention is shown in FIG.
Shown in the figure.

In the apparatus shown in FIG. 1, the raw material tank 1 communicates with the reactor 3 via the supply line 2, and the reactor 3 communicates with the oil / water separator 6 via the product line 4 via the pressure regulating valve 5. The upper opening 12 and the lower opening 13 of the reactor 3 are communicated by a circulation line 9, the supply line 2 is communicated with the vicinity of the upper opening 12 of the circulation line 9, and the product line 4 is located on the lower opening 13 side of the circulation line 9. Communicated. The supply line 2 includes a raw material liquid feed pump 10, and the circulation line 9 includes a reaction liquid circulation pump.
It has a configuration with 11.

The reactor 3 is filled with a solid catalyst to be described later, and the upper opening 12 is circulated from the lower opening 13 of the reactor 3 through the circulation line 9 together with the raw material supplied through the supply line 2. One part of the product is supplied. A part of the reaction product taken out from the lower opening 13 of the reactor 3 is returned to the reactor 3 by the circulation line 9, and the rest is returned to the product line 4.
To separate the reaction product 7 and generated water 8 in the oil / water separator 6 and take it out of the system.

First, to start the reaction, the reactor 3 and the upper opening of the reactor
The inside of the circulation line 9 connecting the 12 and the lower opening 13 is filled with the reaction raw material. By driving the reaction liquid circulation pump 11, the reaction liquid extracted from the lower opening 13 of the reactor is sent again to the upper opening 12 of the reactor, and the liquid in the reactor 3 system is largely circulated through the circulation line 9. The amount of liquid flowing through the circulation line 9 before the reaction liquid circulation pump 11 is adjusted to A. While performing general circulation of the reaction solution, the inside of the reactor 3 is adjusted so as to satisfy predetermined reaction conditions. When the reaction conditions reach predetermined conditions and an alkylation reaction occurs, the raw material supply pump 10 is driven to circulate through the supply line 2 the alkylated raw material liquid prepared by mixing isopropanol and benzene in the raw material tank 1 in advance. Start feeding to line 9. The supply amount of the alkylation raw material liquid is adjusted to be B. The amount of liquid flowing through the circulation line 9 from the supply line 2 to the reactor 3 is A + B. Since the reactor 3 is full of liquid at the beginning of the reaction, when a new alkylation raw material liquid is supplied, the system is pressurized and the pressure rises. Therefore, while opening the pressure regulating valve 5 connected to the product line 4 and extracting a part of the reaction solution as the reaction product 7, the pressure in the reaction system is controlled so as to be maintained at a predetermined pressure. Product line 4
The amount of reaction product flowing through is the amount corresponding to B supplied as alkylation feed.

Thus, by adjusting the flow rate of each pump to maintain the ratio of A to B in a suitable range, the object of the present invention is achieved.

 Hereinafter, the method of the present invention will be described in detail.

In the method of the present invention, a solid catalyst is used.
The catalyst used in the method of the present invention is a solid substance generally showing acidity, for example, silica alumina, activated clay,
Zeolites, strongly acidic ion exchange resins, metal oxides and the like can be mentioned.

To explain the zeolite-based catalyst in more detail,
Oxide-modified zeolite, ZSM-5 type zeolite, hydrogen ion exchanged mordenite zeolite, Y type zeolite,
US-Y type zeolites and the like, and those further modified with metal ions may be used.

Examples of metal oxides include oxides such as iron, cobalt, nickel, and chromium; oxides of titanium and zirconium; and oxides of vanadium, niobium, and antimony.

The form of the catalyst used in the method of the present invention may be either powdery or granular, but in view of the ease of separating the reaction product mixture and the catalyst, the granular catalyst is preferred.

In the method of the present invention, suitable reaction conditions are as follows. That is, the reaction temperature is in the range of 100 to 350 ° C., preferably
It is in the range of 150-300 ° C. The reaction pressure is not particularly limited as long as it is enough to keep the inside of the reaction system in a liquid phase.

In the method of the present invention, A
And the ratio of the newly supplied alkylation raw material liquid B is extremely important. The ratio of A to B is preferably in the range of 2 to 100. Particularly, 7 to 50 is preferable. If A / B is less than 2, the effect of the present invention will not be sufficiently exhibited. On the other hand, even if the A / B is made larger than 100, no further effect is obtained and it is useless to install a pump having a capacity larger than necessary.

In the method of the present invention, the supply amount of the alkylation raw material liquid is
The LHSV is in the range of 0.1 to 20 hr ^-1 , preferably 0.5 to 10 hr ^-1 .

In the method of the present invention, the proportion of the charged isopropanol and benzene in the alkylation raw material is such that the molar ratio of the aromatic compound to the alcohols is 1 to 12, preferably 1.5.
-8.

In the method of the present invention, isopropanol is used as the alcohol.

In the method of the present invention, benzene is used as the aromatic compound to be alkylated.

Among these combinations of alcohols and aromatic compounds, the reaction of alkylating benzene using isopropanol is most important industrially.

In the method of the present invention, a solvent may be used in addition to the mixed solution of isopropanol and benzene.

The solvent used is a compound which is inactive in the present alkylation reaction system. For example, hydrocarbons such as pentane, hexane, heptane, cyclopentane, and cyclohexane are exemplified.

In the method of the present invention, the reaction system is preferably a continuous reaction, and the reactor is preferably a fluidized bed system using a powdered catalyst or a fixed bed system using a granular catalyst.

<Example> Hereinafter, the present invention will be described specifically with reference to examples.

(Example 1) Inner diameter 25.4 mm, length shown in the schematic diagram of the reactor (Fig. 1)
U in the middle of a 500 mm stainless steel vertical tubular reactor
SY type zeolite (TSZ-351PAH1, Tosoh 1.5mmφ
Noodles) was filled in an amount of 50 ml. Thereafter, the reaction system was filled with benzene, and the reaction solution circulation pump was driven to start circulating the reaction solution at a flow rate of 700 ml / hr. Reaction temperature 230 in the reaction system
A mixture of benzene and isopropanol (benzene / isopropanol molar ratio: 5) was fed into the reaction system at a flow rate of 50 ml / hr while controlling the conditions at 25 ° C and a pressure of 25 kgf / cm ² G. A reaction product mixture corresponding to the supply amount of the benzene / isopropanol mixed solution was taken out of the system from a reaction solution extraction line branched from a lower circulation line of the reactor. A continuous reaction was performed for 8 hours while continuously supplying a benzene / isopropanol mixture. The reaction product mixture removed during the period of 7 to 8 hours after continuing the continuous reaction weighed 42.8 g. The reaction product mixture was a mixture of an oil phase and an aqueous phase. After separating the oil and water, the obtained oil phase was analyzed by capillary gas chromatography. As a result, the conversion of isopropanol was 99.9%, and the yield of alkylation based on the supplied isopropanol was 98.4%.

The composition of the alkylated product was cumene 21.8%, dipropylbenzene 3.3%, triisopropylbenzene 0.1%, from which the selectivity for cumene was 89.5%. Also,
The by-product rate of propylene in this alkylation reaction was 0.7
Met.

(Comparative Example 1) The procedure of Example 1 was repeated, except that the reaction liquid circulation pump was not driven. As a result, the conversion of isopropanol was 99.8%, and the alkylation yield based on isopropanol was 97.0%. The propylene by-product rate was 2.6%.

The composition of the alkylated product is cumene 19.8%, diisopropylbenzene 5.1%, triisopropylbenzene 0.2%,
Cumene selectivity was 83.4%.

(Example 2) The procedure of Example 1 was repeated, except that the catalyst was changed to H mordenite type zeolite (TSZ-640 manufactured by Tosoh Corporation). As a result, the alkylation yield based on isopropanol was 98.3%, and the selectivity for cumene in the alkylated product was 78.9%.

(Comparative Example 2) The procedure of Example 2 was repeated, except that the reaction solution was not circulated. As a result, the alkylation yield
87.6%, cumene selectivity was 73.7%.

(Example 3) The procedure of Example 1 was repeated, except that the molar ratio of benzene and isopropanol in the mixed solution of benzene and isopropanol was changed to 3 in Example 1.
As a result, the yield of the alkylation was 96.0%, and the selectivity for cumene was 80.8%.

(Comparative Example 3) The procedure of Example 3 was repeated, except that the reaction solution was not circulated. As a result, the alkylation yield
The response was 85.4% with a cumene selectivity of 54.1%. Furthermore, 14.6% of propylene was by-produced based on the charged isopropanol.

(Examples 4 to 6) Under the conditions of Example 1, the reaction solution and the circulation amount were changed. The obtained result was compared with the result of Example 1 and Comparative Example 1.
The results are shown in Table 1.

From Table 1, it can be seen that the cumene selectivity particularly improves as the reaction solution circulation amount increases.

<Effect of the Invention> In performing the alkylation reaction of benzene using isopropanol as an alkylating agent, by incorporating a circulating process of the reaction solution, propylene by-produced is returned to the reactor and the alkylation reaction is performed. The standard alkylation yield can be improved. In addition, the process according to the invention is of great industrial value, since the selectivity of the monoalkylated cumene in the alkylated product is significantly increased.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a reaction apparatus suitably used in the method of the present invention. DESCRIPTION OF SYMBOLS 1 ... raw material tank 2 ... supply line 3 ... reactor 4 ... product line 5 ... pressure regulating valve 6 ... oil-water separator 7 ... reaction product 8 …… Producted water, 9… Circulation line, 10… Feed material feed pump, 11… Reaction liquid circulation pump, 12 …… Upper opening, 13 …… Lower opening

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location // C07B 61/00 300 C07B 61/00 300

Claims (2)

(57) [Claims] In producing cumene by a continuous alkylation reaction of benzene using isopropanol as an alkylating agent, a reaction mixture containing by-produced propylene discharged from a reactor is prepared by mixing a reaction mixture containing A with B in a ratio of A to B. Is 1
A is divided into two parts, A and B, so that the larger one is circulated again to the reactor, and the other B is extracted out of the reaction system as a reaction product mixture, and an alkylation raw material solution of isopropanol and benzene is taken out. A production process for producing cumene, wherein by-products are supplied in an amount corresponding to B, whereby by-products of higher alkylated products are suppressed and the yield is improved. 2. The method according to claim 2, wherein in the alkylation reaction, A
The method for producing cumene according to claim 1, wherein the ratio is in the range of 7 to 50.