JPH0798757B2 - Method for producing cycloolefin - Google Patents

Description

The present invention relates to a method for partially reducing monocyclic aromatic hydrocarbons to produce corresponding cycloolefins, particularly cyclohexenes, with high selectivity and high yield. It is about.

Cyclohexenes are highly valuable as intermediate raw materials for organic chemical industrial products, and are especially important as polyamide raw materials and lysine raw materials.

(Prior Art) As a method for producing such a cyclohexene, for example,
(1) A method of using a catalyst composition containing water and an alkaline agent and an element of Group VIII of the periodic table (Japanese Patent Publication No. 56-22850), (2) Supported on nickel, cobalt, chromium, titanium or zirconium oxide. Using ruthenium catalyst prepared as above, using alcohol or ester as additive (JP-B-52-3933), (3) using ruthenium catalyst containing copper, silver, cobalt or potassium, and water and phosphate compound Method (Japanese Patent Publication No. 56-4536), (4) Neutral containing a ruthenium catalyst and a salt of at least one cation selected from Group IA metals, Group IIA metals of the periodic table, manganese, zinc and ammonia. Alternatively, a method of carrying out the reaction in the presence of an acidic aqueous solution (Japanese Patent Publication No. 50-142).
536), (5) a solid catalyst containing at least one of ruthenium and rhodium as a main component is a metal of Group IA of the periodic table,
A method in which the reaction is carried out in the presence of water using an aqueous solution containing a salt of at least one cation selected from the group consisting of Group IIA metals, manganese, iron and zinc (JP-A-51- No. 98243), (6) a method of carrying out a reaction by using a ruthenium catalyst and adding at least one of zinc oxide and zinc hydroxide as an activating component to the reaction system (Japanese Patent Laid-Open No. Sho 62-242, pp.
59-184138) and the like have been proposed.

(Problems to be Solved by the Invention) However, in these conventionally known methods, in order to increase the selectivity of the target cyclohexenes, it is necessary to significantly suppress the conversion rate of the raw materials, and the reaction rate is extremely high. In general, the yield and productivity of cyclohexenes are low, such as being small, and it is not a practical method for producing cyclohexenes under the present circumstances.

(Means for Solving the Problems) In order to solve the above problems, the present inventors have aimed to improve the selectivity and yield of cyclohexenes by using a hydrogenation catalyst in a partial reduction method of monocyclic aromatic hydrocarbons. As a result of intensive studies, the present invention has been achieved. That is, a reduced product of ruthenium containing iron in advance is used as a hydrogenation catalyst, and the reaction is carried out under acidic conditions in the presence of water and at least one water-soluble zinc compound. It has been found that cyclohexenes can be obtained with different selectivities and yields.

Hereinafter, specific embodiments of the present invention will be described.

The monocyclic aromatic hydrocarbons as the raw material of the present invention are called benzene, toluene, xylenes and lower alkylbenzenes.

The hydrogenation catalyst in the present invention is a reduced product of ruthenium containing iron in advance.

More specifically, such a catalyst is a reduced product obtained by previously adding an iron compound to a valuable ruthenium compound and then reducing it, and ruthenium is reduced to a metallic state. Valuable ruthenium compounds that can be used include, for example, salts such as chlorides, nitrates and sulfates, complexes such as ammine complex salts, hydroxides and oxides, but especially trivalent or tetravalent ruthenium compounds are available. If easy Moreover, it is preferable because it is easy to handle. A wide range of iron compounds can be used such as oxides, nitrates, salts such as sulfates, hydroxides and oxides.

It is not always clear why such a catalyst is effective as a catalyst for producing cycloolefin, but
It can be considered that in the process of reducing the valuable ruthenium compound to the metal state, the coexisting iron compound appears or increases active sites advantageous for the production of cycloolefin.

The iron content is adjusted to 0.01 to 50% by weight, preferably 0.1 to 20% by weight, based on ruthenium which is the main component in the catalyst of the present invention. Therefore, the main components of the catalyst are
It is ruthenium only, iron is not a carrier.

Regarding the partial hydrogenation reaction using the above-mentioned catalyst containing iron, Journal of Chemical Technical Biotechnology (J. Chem. Tech. Biotechnol.), Vol. 32, 69.
As described on pages 1 to 708 (1982), the reaction is carried out under alkaline conditions, the yield of cyclohexene is less than 20% at the maximum, and the present invention is different in terms of components and effects. It's completely different.

Further, in JP-A-51-98243, there is a description that it is preferable to use a ruthenium catalyst previously treated with an aqueous solution containing an iron cation salt, but there is no description regarding the presence or absence of iron. Further, the treatment of the catalyst is all performed on the reduced catalyst, which is fundamentally different from the catalyst used in the present invention, and a valuable ruthenium compound and an iron compound in the present invention are added. Since the diffraction angle of the X-ray diffraction of the reduced product obtained by reducing the mixture of 1) is shifted to a higher angle side than that of ruthenium metal, the reduced catalyst can be treated with an aqueous solution containing an iron cation salt. It is clear that it is fundamentally different from the treated one.

Further, the smaller the average crystallite size of the reduced product, the more useful the present invention is, and specifically, 200 Å or less, preferably 100 Å or less is desirable for improving the selectivity of cycloolefin.

Here, the crystallite diameter of the catalyst is determined by the general method, that is, the spread of the diffraction line width obtained by the X-ray diffraction method,
It is calculated from the formula of er. Specifically, CuKα
When the X-ray source is used as an X-ray source, the diffraction angle (2θ) is 44
It is calculated from the spread of the diffraction line with a maximum in the vicinity of °.

As described above, the average crystallite size is 200 Å or less, preferably 100
It is Å or less, and the lower limit is larger than the theoretical crystal unit, and is realistically 10 Å or more.

Valuable ruthenium compounds containing iron in the present invention, using a mixed solution of iron and ruthenium compounds,
It may be obtained as a solid by a general coprecipitation method or the like, or may be obtained in the state of a homogeneous solution. The catalyst in the present invention is a valuable ruthenium compound containing such iron,
It is adjusted by reducing ruthenium to a metallic state, and as a reducing method, a general ruthenium reducing method can be applied.

For example, a method of reducing with hydrogen in the gas phase, a method of reducing with hydrogen or a suitable chemical reducing agent such as NaBH ₄ or formalin in the liquid phase is preferably applied,
A method of reducing with hydrogen in a gas phase or a liquid phase is particularly preferable. When reducing with hydrogen in the gas phase, it is advisable to avoid extremely high temperature or to dilute hydrogen with other inert gas in order to avoid increasing the crystallite size. When the reduction is carried out in the liquid phase, the valuable ruthenium compound solid containing iron may be dispersed in water or alcohols, or may be carried out in the form of a homogeneous solution. At this time, stirring, heating and the like may be appropriately performed in order to promote the reduction better. Instead of water, an aqueous alkali solution or an appropriate aqueous metal salt solution such as an aqueous alkali metal salt solution may be used.

In the present invention, the coexistence of water is necessary. Although the amount of water varies depending on the reaction mode, it can be made to coexist 0.01 to 100 times by weight with respect to the monocyclic aromatic hydrocarbon generally used. However, under the reaction conditions, the organic liquid phase containing raw materials and products as main components and the liquid phase containing water are 2
It is necessary to form a phase, and the coexistence of a very small amount of water or a coexistence of a very large amount of water that forms a homogeneous phase under the reaction conditions reduces the effect, and the amount of water is too large. Since it becomes necessary to enlarge the reactor, it is practically desirable to coexist 0.5 to 20 times by weight.

The present invention requires the presence of at least one water-soluble zinc compound in addition to the hydrogenation catalyst and water. As the water-soluble zinc compound, various salts, for example, weak acid salts such as carbonates and acetates, and strong acid salts such as hydrochlorides, nitrates and sulfates are used. Further, zinc oxide and zinc hydroxide are also effectively used. The amount used is 1 × 10 ^{−5 to} 0.3 times by weight, preferably 1 × 10 ^{−4 to} 0.1 times by weight, relative to water coexisting during the reaction. It is not particularly necessary that the zinc compound used be completely dissolved in water coexisting during the reaction.

Examples of such coexistence of a zinc compound in water are described in, for example, JP-A-50-142536.
As the catalyst, a catalyst carrying ruthenium or rhodium is used, and the catalyst itself is different from the present invention, and the selectivity of cycloolefin is low, which is a great difference from the present invention. Further, also in the example in which at least one of zinc oxide and zinc hydroxide is added (JP-A-59-184138), the catalyst used is different and it is said that it is preferable to carry out under alkaline conditions. Again, it is different from the present invention.

In addition to the water-soluble zinc compound, various metals, for example, salts of Group IA elements, Group IIA elements and manganese, cobalt, copper, etc. of the periodic table are used in the reaction system as in known methods already proposed. May coexist.

Furthermore, some means for improving the dispersibility of the catalyst, for example, an inert powder, may coexist during or after the preparation of the catalyst.

Further, in the present invention, preferable results are obtained by reacting the coexisting aqueous phase under acidic conditions. When the aqueous phase is neutral or alkaline, the reaction rate is significantly reduced, and it is difficult to obtain a realistic production method. In addition, in order to make it acidic, ordinary acids such as hydrochloric acid, nitric acid, sulfuric acid, acetic acid,
It is safe to add phosphoric acid, etc. In particular, sulfuric acid is extremely effective in increasing the reaction rate. The pH of the aqueous phase thus introduced into the reaction system is 0.5 to less than 7, preferably 2 to 6.5.

The partial reduction reaction in the method of the present invention is usually carried out continuously or batchwise by a liquid phase suspension method, but can also be carried out by a stationary phase system. The reaction conditions are appropriately selected depending on the type and amount of the catalyst and additives used, but the hydrogen pressure is usually 1 to 200 kg / cm ² G, preferably 10 to 100 kg / cm ² G. The reaction temperature is room temperature to 250 ° C, preferably 100 to 200 ° C
Is the range. The reaction time may be appropriately selected by setting a substantial target value for the selectivity and yield of the desired cyclohexene, and is not particularly limited, but is usually several seconds to several hours.

(Effects of the Invention) According to the present invention, cycloolephin can be obtained with a high selectivity and yield which have never been obtained, and is industrially extremely valuable.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 5.0 g of ruthenium chloride (RuCl ₃ .3H ₂ O) and ferric chloride
1.1 g was dissolved in 500 ml of water and stirred, 70 ml of a 30% caustic soda aqueous solution was added thereto as soon as possible, and the mixture was brought to 80 ° C. and stirred for 2 hours. After cooling to room temperature, let stand and remove the supernatant, then 500m of 5% caustic soda solution
Washing with stirring, standing and removal of the supernatant were repeated 3 times using 1. The liquid containing the remaining black precipitate was made up to 500 ml with a 5% caustic soda solution, charged into an autoclave with an internal volume of 1 and having Teflon coating on the inner surface, and the total pressure was adjusted to 50 kg / cm ² G with hydrogen for 12 hours at 150 ° C. Reduced. After cooling, the obtained black precipitate was washed with water to remove caustic soda. This was vacuum dried under a nitrogen atmosphere to obtain 2.3 g of a black hydrogenation catalyst. When this catalyst was analyzed by X-ray diffractometry, crystal growth was observed and its average crystallite system was 51Å. On the other hand, the iron content in this catalyst was determined by the fluorescent X-ray method to be 2.4% by weight. In addition, in X-ray diffraction, the peak position of the (101) diffraction line of ruthenium was found to shift to the higher angle side, so the iron-containing form of this catalyst was different from the mixture or adsorption of iron compounds. It is clear that

0.4 g of the above catalyst, 320 ml of water, 14.4 g of ZnSO ₄ .7H ₂ O and 80 ml of benzene were charged into an autoclave having an internal volume of 1 with Teflon coating on the inner surface, and the temperature was raised to 150 ° C.
Hydrogen was injected under pressure to a total pressure of 50 kg / cm ² G, and the reaction was carried out under high speed stirring. The reaction liquid was withdrawn with time and the composition of the oil phase was analyzed by gas chromatography. The results are shown below.

The by-product was cyclohexane.

Comparative Example 1 The same operation as in Example 1 was performed except that 0.5 g of ruthenium metal (average crystallite size of 500 Å or more) manufactured by Nippon Engelhard Co., Ltd. was used as a hydrogenation catalyst. The results are shown below.

The effectiveness of the hydrogenation catalyst in the process of the invention is clear.

Comparative Example 2 In the same manner as in Example 1 except that metallic ruthenium having an average crystallite size of 59Å was prepared in the same manner as in Example 1 without ferric chloride at the time of preparing the catalyst and used as the hydrogenation catalyst. It was made to react. The results are shown below.

From this, the superiority of the catalyst in the method of the present invention is clear for the catalysts having almost the same average crystallite size.

The X-ray diffraction patterns of the catalysts used in Example 1 and Comparative Example 2 are shown in FIGS. 1 and 2, respectively. The operating conditions for obtaining the X-ray diffraction diagrams of FIGS. 1 and 2 are as follows, and silicon powder was used as the internal standard.

X-ray Cu-Kα ray Rad 40 KV × 30 mA Comparative Example 3 Prepared by adsorbing ruthenium chloride on ferric tetroxide and reducing with hydrogen by a usual equilibrium adsorption method. The same reaction as in Example 1 was carried out except that 4.0 g of a hydrogenation catalyst supporting 1% by weight of ruthenium was used. The results are shown below.

From this, it is apparent that the metal ruthenium catalyst having iron as a carrier and the catalyst of the present invention are greatly different from each other.

Examples 2 to 7 Table 1 shows the results of carrying out the same reaction as in Example 1 in various aqueous solutions while changing the crystallite size of ruthenium and the iron content of the hydrogenation catalyst.

Example 8 The same operation as in Example 1 was performed except that 1.6 ml of 1 N H ₂ SO ₄ was added. The results are shown below.

It can be seen that the addition of acid can greatly increase the reaction rate.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of the catalyst used in Example 1, and FIG. 2 is an X-ray diffraction diagram of the catalyst used in Comparative Example 2.

Claims (2)

[Claims] 1. A reduced product of ruthenium containing iron in advance as a hydrogenation catalyst when partially reducing monocyclic aromatic hydrocarbons with hydrogen in the coexistence of water, wherein the iron content is relative to that of ruthenium. A process for producing cycloolefin, which comprises carrying out the reaction under acidic conditions in the presence of at least one water-soluble zinc compound using a catalyst of 0.01 to 50% by weight. 2. The method for producing cycloolefin according to claim 1, wherein the hydrogenation catalyst has an average crystallite size of 200 Å or less.