JPH0739353B2 - How to prevent catalyst deterioration - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for partially hydrogenating a monocyclic aromatic hydrocarbon to produce a corresponding cycloolefin, more specifically, a method for use in the reaction. The present invention relates to a method for preventing deterioration of a ruthenium catalyst.

Cyllohexanes 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) Regarding the partial hydrogenation method of such monocyclic aromatic hydrocarbons,
For example, (1) a method in the presence of a ruthenium catalyst and a neutral or acidic aqueous solution containing a Group Ia metal, a Group IIa metal, Mn, Zn, or a chloride or sulfate of ammonia (JP-A-
142536) or in the presence of a catalyst previously treated with an aqueous solution containing salts of these metals (JP-A-51-98243), (2) ruthenium catalyst and cobalt, nickel, copper carbonate. Alternatively, a method carried out in the presence of an aqueous solution of a basic carbonate, (3) a method carried out in the presence of water and an alkaline agent using a reduced cation of at least one Group VIII element of the periodic table as a catalyst (Japanese Patent Publication No. −22
No. 850), etc., and generally, the coexistence of water or an aqueous solution increases the selectivity and yield of the corresponding cycloolefin, which is a preferable method.

(Problems to be Solved by the Invention) However, according to the studies by the present inventors, in the method of coexisting such an aqueous solution, the corrosion of the material in the liquid contact part such as the reactor is caused by the anion and the alkali of the additive. It was revealed that the progress of the metal and the elution of the metal from the reactor cause a decrease in the activity and selectivity of the catalyst, and it was found to be a considerable obstacle to practical use.
In particular, a decrease in the activity and selectivity of the catalyst makes it difficult to obtain cycloolefins in a stable manner and economically disadvantageous. Therefore, a method of preventing this catalyst deterioration is extremely important.

On the other hand, regarding the influence of the material of such a reactor on the reaction, there is no principle or quantitative treatment, and in the commonly used austenitic stainless steel, the adverse effect on the reaction is due to the iron as the main component. On the other hand, it is presumed that ruthenium catalysts poisoned with iron are more effective in improving the selectivity of cycloolefins (J. Chem. Tech. Biotechnol. 32: 691-708 '). 8
There are various interpretations such as 2), and it can be said that the actual situation is that no realistic reaction system is selected.

(Means for Solving the Problems) In order to solve the problems, the inventors of the present invention arrived at the present invention by studying and quantifying the effects of reactor materials and metal ions on the reaction in detail. is there. That is, in the reaction system, by carrying out the reaction in a reaction atmosphere in which iron does not accumulate on the catalyst in an amount of 2% by weight or more with respect to the catalyst, the desired cycloolefins can be obtained with high selectivity, high yield, and long duration. The present invention has been completed based on the finding that the catalyst can be produced under stable catalytic activity for a period of time.

The monocyclic aromatic hydrocarbon in the present invention refers to benzene, toluene, xylenes and other lower alkylbenzenes. These raw materials are introduced into the reaction system after the iron content contained therein is removed by an appropriate method such as a filter treatment or an adsorption treatment. The partial hydrogenation reaction is carried out continuously or batchwise by a liquid phase suspension method of a ruthenium catalyst, water and a raw material. The water used is optionally added with suitable additives such as metal salts and alkaline agents. Usually, the hydrogen pressure is 1 to 200 kg / cm ² G, preferably
A 10~100kg / cm ² G, the reaction temperature is room temperature to 250 DEG ° C., preferably from 100 to 200 ° C..

According to the study of the present inventors, when the partial hydrogenation reaction is continued for a long time under such conditions, when a material mainly containing iron as a reactor material such as austenitic stainless steel is used, the liquid contact surface It was found that more eluting iron economically accumulated on the ruthenium catalyst, and the activity and selectivity of the catalyst were significantly impaired. What's more remarkable is that
The amount of iron accumulated on such a catalyst is incomparably larger than the amount of iron in coexisting water, in other words, the iron concentration in water decreases due to the adsorption force of the catalyst, and It was found that a situation such as promoting dissolution was reached. Therefore, the accumulation of iron on the catalyst continues until the catalyst loses its adsorptive power, but a catalyst that adsorbs a large amount of such eluted iron is no longer practical as a catalyst for the partial hydrogenation reaction. is not.

The correlation between the amount of iron accumulated on the ruthenium catalyst and the decrease in activity and selectivity is clarified for the first time by the present invention, and is an extremely important knowledge for practical use. It is not clear why the accumulation of iron reduces the activity or selectivity of the reaction, but it is effective for the accumulated iron to greatly change the concentration and properties of the reaction active sites on the surface of ruthenium and to convert it to cycloolefin. It is considered that the number of active sites is reduced.

Therefore, the smaller the amount of iron entrained in the raw material and the amount of iron eluted from the reactor itself having iron as a constituent component into the reaction solution, the longer the activity and selectivity of the catalyst are extended. Therefore, it can be said that it is a preferable reaction atmosphere. From an industrial or economic point of view, it is common for operations such as regeneration and partial disposal of deteriorated catalysts to be part of the process, so the price of such precious metal catalysts,
The rate of iron accumulation on the catalyst must be controlled by taking into account the costs of regeneration and disposal, but the period until the upper limit of iron accumulation that can maintain the activity and selectivity of the catalyst is at least reached. Unless it is more than 500 hours, it is not practical. The upper limit of the amount of iron that can maintain the activity and selectivity of the catalyst depends on the form of the catalyst and the type of carrier, but is 2% by weight or less based on ruthenium.

In order to set up such an environment, it is most simple and effective to devise the material of the liquid contact part.

For example, when an alkaline agent is used as an additive to water, nickel, zirconium, tantalum or alloys containing these as a main component can be listed as a material having strong alkali resistance, but from a practical and economical point of view. Nickel is preferred.

Further, when further considering the economical aspect, an anticorrosive agent generally called a passivating agent such as a chromate salt, a morbudate salt, a tungstate salt when a material containing iron as a main component, for example, an austenitic stainless steel is used. The method of suppressing the elution of iron by adding such as to the reaction system is
It is extremely effective and practical. In this method, it is practically difficult to completely suppress the accumulation of iron on the catalyst, but the time to reach the above-mentioned upper limit of iron accumulation can be greatly increased.

(Effect) As in the present invention, by reacting in a reaction atmosphere in which iron does not substantially accumulate on the catalyst, the partial hydrogenation reaction of a monocyclic aromatic hydrocarbon is maintained for a long period of time while maintaining activity and selectivity. You can do it.

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

Example 1 Catalyst with 1% ruthenium supported on lanthanum hydroxide 3.5
g, 280 ml of water, 7.0 g of sodium hydroxide, 70 mg of zinc oxide, and 140 ml of benzene were charged into an autoclave with an internal volume of 1 having a nickel plating on the inner surface, and 170 with stirring.
A partial hydrogenation reaction of benzene was carried out at ℃ and hydrogen pressure of 50 kg / cm ² G. The reaction solution was withdrawn over time, and the organic phase was analyzed by gas chromatography. The benzene conversion rate was 40%.
It took 27 minutes to obtain the cyclohexene selectivity of 75.0%.

The other product was cyclohexynsan.

After the completion of the reaction, the catalyst was recovered and the iron concentration in the catalyst was measured and found to be 21 ppm (weight).

Example 2 The same catalyst as in Example 1 40 g, water 800 ml, sodium hydroxide 20
g, zinc oxide 400 mg as an auxiliary tank with an oil-water separation tank, and put it in a continuous flow reactor with a nickel plating on the wetted part, and at 150 ° C, hydrogen pressure 50 kg / cm ² G Benzene containing no hydrogen was supplied at 2 / Hr to continuously carry out the partial hydrogenation reaction of benze. Distribution reaction started 10
The conversion rate of benzene after 33 hours is 33% and the selectivity of cyclohexene is 70%. After 100 hours, the conversion rate is 32% and the selectivity is 70%.
%, And after another 500 hours, conversion rate 31%, selectivity 71%,
Cyclohexene was obtained stably with almost no change in conversion or selectivity. Also, the catalyst after 500 hours was taken out and the heat concentration in the catalyst was measured and found to be 42 ppm.

Comparative Example 1 Assuming that iron was mixed in from the raw material, Example 1 was repeated except that an aqueous solution of ferrous sulfate was constantly added to the reaction system so that the iron amount was 1 mg / Hr. The same operation was performed. Table 1 shows the transition reaction time, conversion rate, selectivity and transition of iron concentration in the catalyst.

Comparative Example 2 The same operation as in Example 2 was performed, except that the liquid contacting part made of SUS316 was used as the continuous flow reactor. Table 2 shows transitions of the flow reaction time, conversion rate, selectivity and iron concentration in the catalyst.

Example 3 Except that 160 mg of sodium chromate was added as a passivating agent to the reaction system and 100 mg was added additionally every 200 hours thereafter.
The same operation as in Comparative Example 2 was performed. The results are shown in Table 3.

Claims (1)

[Claims] 1. When a monocyclic aromatic hydrocarbon is partially hydrogenated with hydrogen in a liquid phase in the coexistence of a ruthenium catalyst and water and a zinc compound, nickel, zirconium and tantalum are mainly used as materials for the liquid contact portion of the reactor. 2% by weight of iron relative to the ruthenium catalyst is added to the ruthenium catalyst by adding an anti-corrosion agent that acts as a passivating agent to the reaction system using an alloy with iron as a component or austenitic stainless steel. A method for preventing catalyst deterioration, which is characterized in that the reaction is performed in a reaction atmosphere that does not accumulate the above.