JPH0521094B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention involves a gas phase contact reaction of phenol and methanol in the presence of a metal oxide to produce an ortho-methylated phenol compound.
Alternatively, the present invention relates to a method for economically recovering 2,6-xylenol. 2,6-xylenol produced by the method of the present invention is a raw material for porphenylene oxide and 2,6-xylidine, which is a raw material for agricultural chemical ingredients, while orthocresol is a raw material for pharmaceutical and agricultural products. Both are useful as industrial raw materials. (Prior art) Phenol and ethanol are brought into contact in a gas phase,
Methods for producing orthocresol and/or 2,6-xylenol are known and are practiced industrially. The conventional process will be specifically explained below with reference to FIG. 1 using production examples of 2,6-xylenol and orthocresol. Phenol and methanol react in the gas phase in the presence of a catalyst in reactor 1, and apart from the main products 2,6-xylenol and orthocresol, small amounts of 2,4-xylenol, 2,5-xylenol and 2 , 4,6-trimethylphenol, etc.
and high-boiling products are formed, forming a mixture with unreacted methanol, phenol and produced water. After cooling this high-temperature gaseous mixture in a heat exchanger 2, it is sent to a gas separation tower 3 to separate the gaseous by-products and the mixture. Here, gaseous byproducts include hydrogen gas, carbon monoxide, carbon gas,
Methane gas etc. Water passes from the bottom of the gas separation tower 3 through a line 4 and is distilled and separated in a dehydration tower 5. Methanol and water distilled from the top of the dehydration tower 5 pass through a line 6 and are distilled and separated in a methanol tower 7. The recovered methanol distilled from line 8 at the top of the methanol column is recycled and reused in the reaction system.
On the other hand, the bottom liquid of the dehydration tower 5 passes through a line 9, and unreacted phenol is separated by distillation in a phenol tower 10. The recovered phenol distilled from the line 11 at the top of the phenol column is recycled and reused in the reaction system together with the recovered methanol. The bottom liquid of the phenol column 10 passes through a line 12, and in the ortho-cresol column 13, ortho-cresol is distilled and separated as a product. The bottom liquid of the orthocresol column 13 passes through a line 15 and is distilled and separated as a product in 2,6-xylenol column 16. Byproducts containing 2,4,6-trimethylphenol, 2,4-xylenol, 2,5-xylenol, etc. are discharged from the bottom of the 2,6-xylenol column 16. As distillation columns, bubble columns, plate columns and packed columns are usually used. In addition, dehydration towers and methanol towers are usually
At normal pressure, phenol tower, orthocresol tower,
2,6-xylenol towers are often operated at reduced pressure. The conventional manufacturing method for orthocresol and 2,6-xylenol is as described above, and in some cases, when orthocresol and 2,6-xylenol are separated, extraction and separation with aliphatic saturated hydrocarbons, etc. may be performed. is also possible. On the other hand, the present inventors have investigated gaseous by-products from a reaction mixture containing ortho-methylated phenol compounds, high-boiling by-products, unreacted methanol, and phenol produced by a methylation reaction of phenol using a fluidized bed method. Separating the product, separating unreacted methanol and produced water from the resulting mixture, and further separating phenol by distillation, then separating orthocresol and 2,6-xylenol,
Thereafter, in the method for producing an ortho-methylated phenol compound in which 2,6-xylenol is separated by distillation, the fine powder catalyst scattered from the fluidized bed reactor is removed by distilling off high-boiling substances before distilling off the phenol. We have invented a method for producing ortho-methylated phenol compounds, which is characterized by discharging them out of the system together with high-boiling substances, and have already applied for a patent. Its implementation is illustrated in the flow sheet of FIG. In the flow sheet of FIG. 2, the bottom liquid of the dehydration tower 5 passes through line 9 and is introduced into the high-boiling point substance separation column 19, and the high-boiling point substance containing the fine catalyst is discharged to the outside of the system through line 20. . The flow sheet is similar to that of FIG. 1, except that the top liquid is introduced into the phenol column 10 through line 21. (Problems to be Solved by the Invention) As seen in the above example, high boiling point substances are discharged in the separation process of orthocresol and 2,6-xylenol, but they are usually not used for purposes other than as fuel. Currently, no technology has been developed to further increase added value. (Means for solving the problem) Conventionally, orthocresol and/or 2,6
- The high-boiling substances discharged in the xylenol separation process had no use other than fuel, but according to the present invention, the high-boiling substances can be very easily decomposed into useful components of orthocresol and/or 2,6-xylenol. They found the conditions to do so. That is, the present inventors have found that reduction of high boiling point substances,
As a result of intensive studies from the perspective of improving the raw material consumption rate, we found that some of the separated high-boiling substances were easily decomposed by introducing hydrogen gas under conditions of 250°C or higher, resulting in phenol, orthocresol, and Discovered the fact that it changes to 2,6-xylenol,
We have arrived at the present invention. The gist of the present invention is to produce orthocresol and/or 2,6-xylenol by performing a gas phase catalytic reaction of phenol and methanol in the presence of a metal oxide, and the reaction product, gaseous by-product, and unreacted In a method for separating methanol, unreacted phenol, produced water, and orthocresol and/or 2,6-xylenol, the high-boiling substances to be separated are decomposed by introducing hydrogen gas at a temperature of 250°C or higher to produce phenol, This is a method for recovering orthocresol and 2,6-xylenol. The catalyst applied to the gas phase reaction of methanol and phenol in the present invention contains iron, iron,
vanadium, manganese, magnesium, chromium,
Indium alone or in combination;
Alkali metals, alkaline earth metals, rare earth metals, etc. may be added to these components for use. In the case of the present invention, the molar ratio of methanol to phenol or/and orthocresol in the feedstock varies depending on the catalyst species, but ranges from 1:1 to 20
It is. Further, water vapor or an inert gas may be introduced as necessary, but in the case of water vapor, the molar ratio to phenol and/or orthocresol is preferably 1:0 to 15. The reaction temperature varies depending on the catalyst type, but is between 250 and 600℃.
A range of is preferred. The reaction can be carried out at normal pressure, reduced pressure or increased pressure. In the present invention, the high boiling point substance is 2,
It is discharged through the bottom line 18 of the 6-xylenol column 16 and, in FIG. 2, through the bottom line 20 of the high boiler separation column 19. In the present invention, the decomposition temperature of high boiling point substances is 250℃
The temperature is preferably 270°C or higher. Decomposition temperature
If the temperature is lower than 250°C, the recovery rate of orthocresol and 2,6-xylenol decreases, making it uneconomical. The higher the separation temperature, the better, but 300℃
In this case, the recovery rate of orthocresol and 2,6-xylenol from the high boiling point substance becomes almost constant. The longer the decomposition time is, the higher the recovery rate of phenol, orthocresol, and 2,6-xylenol is, but it becomes almost constant over 5 hours. Usually 2
~4 hours is chosen for economic reasons. The hydrogen gas to be introduced does not necessarily need to be of high purity, and cracked gas (32% hydrogen, other gases such as methane, carbon monoxide, and carbon dioxide gas) produced in this production reaction can also be applied to the present invention. The amount of hydrogen gas should theoretically be at least equimolar to the high boiling point substance, but if the gas-liquid contact efficiency is poor, it should be corrected.
It is natural to introduce it. The thermal decomposition method can be applied either batchwise or continuously. The operating pressure during decomposition is either normal pressure or reduced pressure. (Effects of the Invention) In the present invention, by thermally decomposing high-boiling substances discharged in the purification process of orthocresol and/or 2,6-xylenol,
Easily phenol, orthocresol and 2,
It is now possible to convert it into useful components such as 6-xylenol and recover it, which has significant effects in terms of resource conservation, such as improving the raw material consumption rate. Furthermore, by introducing hydrogen gas, the temperature conditions for thermal decomposition are lowered, heating energy is reduced, and operability is improved. (Example) Examples will be described below. Example 1 In this example, as shown in FIG. 2, the phenolic mixture passes through line 4 from the bottom of gas separation tower 3, and after distilling and separating water in dehydration tower 5, the phenolic mixture passes through line 9 to remove high boiling point The top liquid passes through line 21 and is introduced into the phenol column 10, then into the orthocresol column 13, and further into the phenol column 10.
6-xylenol is introduced into the column 16, the orthocresol product is introduced from line 14, and the 2,6-xylenol product is introduced from line 17.
- A xylenol product was obtained. At the same time, high-boiling substances were obtained from the bottom line of the high-boiling substance separation column 19. 493 The obtained high boiling point substance was placed in a four-necked flask.
The temperature inside the flask was heated to 290° C. at normal pressure using an oil bath, and at the same time, hydrogen gas with a purity close to 100% was introduced into the liquid inside the flask. A cooler was installed on the vent side to prevent decomposition products from scattering outside the system. After thermal decomposition under hydrogen gas introduction for 4 hours, a small amount of decomposition distillate was returned to the flask and its weight was measured, and it was 488 g. Table 1 shows the results of component analysis. According to this experiment, the decomposition recovery rate of the active ingredients of orthocresol 2,6-xylenol and phenol reached 30%.

[Table] Example 2 The high boiling point substance obtained in Example 1 was charged into flask 1, and the internal temperature of the flask was set at 270°C and 300°C, respectively.
The same operation as in Example 1 was performed except that the temperature was changed to 320°C and 320°C. The experimental results are shown in Table 2.

[Table] Example 3 The high-boiling substance obtained in Example 1 was charged into flask 1, the flask internal temperature was maintained at 300°C, and the heating time was 0.75 hours, 2 hours, and 6 hours. The same operation as in Example 1 was performed. The experimental results are shown in Table 3.

[Table] Comparative Example 1 The high boiling point substance obtained in Example 1 was charged into flask 1, and the operation was performed in exactly the same manner as in Example 1, except that the flask internal temperature was changed to 220°C and 240°C. . The experimental results are shown in Table 4.

[Table] Comparative Example 2 The high-boiling substance obtained in Example 1 was charged into flask 1, and the internal temperature of the flask was changed to 300°C and 320°C without introducing any hydrogen gas, etc., and decomposition was performed only by heating. The operation was exactly the same as in Example 1, except that. The experimental results are shown in Table 5.

【table】

【table】 [Brief explanation of drawings]

FIGS. 1 and 2 are process diagrams of a conventional method for producing 2,6-xylenol and orthocresol.

Claims (1)

[Claims] 1. When producing orthocresol and/or 2,6-xylenol by carrying out a gas phase contact reaction of phenol and ethanol in the presence of a metal oxide,
In a method for separating gaseous by-products, unreacted methanol, unreacted phenol, produced water, and orthocresol and/or 2,6-xylenol from a reaction product, the high-boiling substances to be separated are
Hydrogen gas is introduced and decomposed under conditions of 250℃ or higher,
A method for recovering phenol, orthocresol and 2,6-xylenol.