JPH0438737B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a method of combining phenol or/and orthocresol and methanol in the presence of a metal oxide.
The present invention relates to a method for economically separating a main product from a reaction product in a method for producing an ortho-methylated phenol compound through gas phase contact using a fluidized bed reaction.

The ortho-methylated phenol compound, such as 2,6-xylenol, produced by the method of the present invention is a raw material for polyphenylene oxide and 2,6-xylidine, which is a raw material for agricultural chemical ingredients; Orthocresol is a raw material for pharmaceutical and agricultural products, and both are useful as industrial raw materials.

(Prior Art) A method for producing an ortho-methylated phenol compound by contacting phenol or/or orthocresol with methanol in the gas phase is known and is carried out using a fixed bed reactor.

Generally, when exothermic reactions are carried out using a fixed bed reactor, local heating tends to occur, which is extremely disadvantageous in terms of reaction, so methods using a fluidized bed reactor have been proposed (in particular). Kosho 52-
46930).

Famous examples of practical applications of the fluidized bed method include the fluid catalytic cracking (FCC) process and the acrylonitrile production process, and the catalyst used must contain particles of 44μ or less to facilitate fluidity.
A mixing ratio of 20 to 40% is considered appropriate.

Therefore, one of the drawbacks of the fluidized bed method is the constant catalyst loss of fine powder particles, and it is extremely important in the fluidized bed process how to advantageously treat the dispersed catalyst.

As a method for removing the scattered catalyst, it is common sense to remove it from the condensate of the reaction product using a precoat filter, but this method is complicated and cannot be said to be an industrially advantageous process. In the example of the acrylonitrile production process, a method has been proposed in which preliminary washing with hot water is performed as a pre-process of washing with sulfuric acid to collect high-boiling substances and catalyst particles in the gas, but a method for producing ortho-methylated phenol compounds has been proposed. However, it is difficult to apply this method because the separation process is different. That is,
An economical process for blown catalyst treatment in fluidized bed reactions needs to be established through separation processes.

In the process of producing ortho-methylated phenol compounds, if the scattered catalyst from the fluidized bed reactor is introduced untreated into the separation column without being discharged to the outside of the system midway, the final product column 2,
The fine powder catalyst will be discharged from the bottom of the 6-xylenol tower, but the catalyst will accumulate inside the separation tower, significantly reducing the separation performance. Contamination of the exchanger causes a reduction in heat transfer ability, making it virtually impossible to continue continuous operation.

(Problems to be Solved by the Invention) As mentioned above, when producing an ortho-methylated phenol compound using a fluidized bed method, the actual situation is that no industrial process has been established for treating the scattered catalyst. be. In view of these circumstances, the present inventors have conducted various studies and found that phenol or/
and ortho-cresol and methanol in the presence of metal oxides to separate gaseous by-products from the reaction mixture containing the resulting ortho-methylated phenolic compounds, high-boiling by-products, and unreacted methanol and phenols. After separating unreacted methanol and produced water from the resulting mixture, and further separating phenol by distillation, orthocresol and 2,6-xylenol are separated, and then 2,6-xylenol is separated.
- In a method for producing an ortho-methylated phenol compound in which xylenol is separated by distillation, the reaction is carried out by a fluidized bed reaction, and before the phenol is separated by distillation, high-boiling substances are separated by distillation so that they are dispersed from the fluidized bed reactor. We have already invented and applied for a patent on a method for producing ortho-methylated phenol compounds, which is characterized by discharging the finely divided catalyst together with high-boiling substances from the system. According to this prior invention, there is no problem at all as a method for treating the scattered catalyst from the fluidized bed reactor, but the high boiling point substances including the fine catalyst discharged outside the system are usually incinerated. However, there are disadvantages associated with this incineration process.
This needs to be resolved.

(Means for Solving the Problems) The process of the prior invention was modified in accordance with the production example of 2,6-xylenol and orthocresol.
A detailed explanation will be given according to the flow sheet shown in the figure.

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 this high-temperature gaseous mixture is cooled by a heat exchanger 2, it is sent to a gas separation tower 3 to separate the gaseous by-products from the mixture. Here, the gaseous by-products include hydrogen gas, carbon monoxide, carbon dioxide gas, methane gas, and the like. 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 is introduced into a high-boiling substance separation column 19 through a line 9, and high-boiling substances containing fine powder catalyst are discharged out of the system through a line 20. The top liquid passes through line 21 to phenol column 1.
0 is introduced. In the phenol column, unreacted phenol is separated by distillation, and the recovered phenol distilled from the line 11 at the top of the 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 to an ortho-cresol column 13 where ortho-cresol is distilled and separated as a product. The bottom liquid of the ortho-cresol column 13 passes through a line 15 and is distilled off in a 2,6-xylenol column 16 to separate 2,6-xylenol as a product. 2,6-xylenol tower 1
From the bottom of column 6, 2, 4, 6 are passed through line 18.
-High-boiling products are discharged, including trimethylphenol, 2,4-xylenol, 2,5-xylenol, etc.

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 towers, orthocresol towers,
6-xylenol towers are often operated at reduced pressure.

The method for producing 2,6-xylenol of the prior invention is as described above, and in some cases, extraction separation using aliphatic saturated hydrocarbons, etc. is used to separate orthocresol and 2,6-xylenol. It is also possible to do so.

In the prior invention, the high boiling point substance containing the fine catalyst discharged outside the system is usually incinerated, but some ortho-methylated phenol compounds are included in this high boiling point substance. It is unsuitable as a fuel for a furnace because the metal catalyst it contains has an adverse effect during incineration, and it has the disadvantage that the type of furnace and usage conditions are restricted during incineration. That is, the catalyst used in the methylation reaction may contain two or more types of iron oxide, vanadium oxide, magnesium oxide, manganese oxide, chromium oxide, lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, etc. However, if high-boiling materials containing these oxides are used as boiler fuel, fouling of boiler conduction surfaces and other heat exchangers for heat recovery will rapidly accelerate, reducing the heat recovery rate and causing economic problems. Not the point.

In addition, the high-boiling substance system contains some useful components such as phenol, orthocresol, and 2,6-xylenol, which cannot be completely recovered by distillation. Complete recovery of these useful components by distillation requires a huge amount of steam, which is not economical.

Therefore, the present inventors have made extensive studies to solve the above problems, and as a result, have established an industrially extremely effective separation method.

That is, after the fine powder catalyst scattered from the fluidized bed reactor is separated by distillation together with the high boiling point substances, the ortho-methylated phenol compound remaining in the bottom liquid by thin film evaporation and the high boiling substances not containing the fine powder catalyst are removed from the bottom liquid by thin film evaporation. The gist of the present invention is to react phenol or/and orthocresol with methanol in the presence of a metal oxide to recover ortho-methylated phenolic compounds, high-boiling byproducts, and unreacted of methanol,
Gaseous by-products are separated from the reaction mixture containing phenol, unreacted methanol and produced water are separated from the resulting mixture, phenol is further separated by distillation, and then orthocresol and 2,6-xylenol are separated. Then, in the method for producing an ortho-methylated phenol compound in which 2,6-xylenol is separated by distillation, the reaction is carried out by a fluidized bed reaction, and furthermore, before the phenol is separated by distillation, the fine powder catalyst scattered from the reactor is heated to a high temperature. An ortho-methylated phenol compound, which is separated by distillation together with a boiling-point substance, and the ortho-methylated phenol compound remaining in the bottom liquid and high-boiling substances that do not contain a fine catalyst are recovered from the bottom liquid by thin film evaporation. This is a manufacturing method.

The catalyst applicable to the present invention is not specific, and all catalysts used for the synthesis of ortho-methylated phenol compounds are covered. For example, metal components often include two or more of iron oxide, vanadium oxide, magnesium oxide, manganese oxide, chromium oxide, lithium oxide, sodium oxide, potassium oxide, rubidium oxide, cesium oxide, and the like.

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 can 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 reaction in the present invention, anisole, 2,4
-xylenol, 2,5-xylenol, m-cresol, para-cresol, 2,4,6-trimethylphenol, and high-boiling substances having a boiling point higher than 2,4,6-trimethylphenol are produced as by-products.
In addition, the fine powder scattered from the fluidized bed reactor depends on the performance of the cyclone inside the reactor, but most of the particles are catalysts with a size of 30μ or less.

The separation process in the present invention includes a method in which water is distilled and separated in a dehydration tower, and then a phenolic mixture containing a fine catalyst is discharged from a high boiling point substance separation tower to discharge high boiling substances containing a fine catalyst to the outside of the system; There are two ways to distill the phenol: the methanol and phenol mixture containing the fine catalyst from the bottom of the gas separation tower is passed through the high-boiling substance separation column, and the high-boiling substances containing the fine catalyst are discharged to the system. It exists as a separation process before separation, but the effect is the same no matter which one is adopted.

In the present invention, the high-boiling substances separated in the high-boiling separation column 19 shown in the flow sheet of FIG. 2 are 2,6-
Many substances have boiling points approximately equal to or higher than 2,6-xylenol, and have high viscosity.

It has been found that a temperature of 280° C. or higher is effective for recovering residual phenol, orthocresol and 2,6-xylenol from such high-boiling phenolic substances. Distillation is also available as a recovery method, but the extracted components have a very high viscosity.
Handling a system containing a finely powdered catalyst at a concentration of 2 to 10% by weight is not practical because the heating heat exchanger becomes dirty. In particular, if the residence time at high temperatures becomes long, the high boiling point substances will change in quality, resulting in even higher viscosity and the handling of the residue will become extremely complicated.

Therefore, a thin film evaporator with a short residence time is selected because it can solve the above problems all at once.

The type of thin film evaporator used is not limited, and both horizontal and vertical types may be employed. By using a thin film evaporator, it is possible to recover the contained ortho-methylated phenolic compounds and high-boiling substances that do not contain fine powder catalysts, which expands the range that can be used as fuel, resulting in a resource-saving position. It will be very advantageous.

(Effects of the Invention) In the prior invention, since the high-boiling separation column contained a fine powder catalyst, the utilization of the ortho-methylated phenol compound and high-boiling substances contained therein was limited, but with the present invention, The ortho-methylated phenolic compound was easily recovered, and most of the high-boiling compounds containing no fine powder catalyst were recovered, greatly expanding the range of their use as fuels.

(Example) The present invention will be explained below with reference to Examples.

When phenol and methanol are reacted in the gas phase in the presence of a catalyst in reactor 1 according to the flow sheet shown in Figure 2, in addition to the main products of 2,6-xylenol and orthocresol, a small amount of , 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 this high-temperature gaseous mixture is cooled by a heat exchanger 2, it is sent to a gas separation tower 3 to separate the gaseous by-products from the mixture. Here, the gaseous by-products include hydrogen gas, carbon monoxide, carbon dioxide gas, methane gas, and the like. A line 4 is passed from the bottom of the gas separation tower 3 to a dehydration tower 5 where water is distilled and separated. Methanol and water collected from the top of the dehydration tower 5 pass through a line 6 and are separated by distillation in a methanol tower 7.

The recovered methanol distilled from the line 8 at the top of the methanol column 7 is recycled and reused in the reaction system.

On the other hand, the phenolic mixture containing the fine powder catalyst in the bottom liquid of the dehydration tower 5 is introduced into the high-boiling separation tower 19 through line 9, and the top liquid is introduced into the phenol tower 10 through line 21, and then through line 12. The oxocresol column 13 was further introduced into a 2,6-xylenol column 16 through a line 15, and an orthocresol product was obtained from a line 14, and a 2,6-xylenol product was obtained from a line 17. The recovered phenol distilled from the line 11 at the top of the phenol column 10 is recycled and reused in the reaction system together with the recovered methanol.

The bottom liquid of the high-boiling separation column 19 is introduced into a thin film evaporator 22 through a line 20, and the gas side is connected to a heat exchanger 2.
Part of the fuel was condensed in step 4 and passed through line 25 to obtain a fuel consisting mainly of high-boiling substances that did not contain any finely powdered catalyst. Furthermore, an active ingredient mainly consisting of an ortho-methylated phenol compound was recovered from a line 27 through a heat exchanger 26 .

A small amount of the bottom liquid side of the thin film evaporator 22 was discharged to the outside of the system through a line 23 as a higher boiling point substance containing a fine powder catalyst. The thin film evaporator used a horizontal type, and the pressure was 20 Torr. and the temperature was 290°C.

[Brief explanation of drawings]

Figure 1 is a flow sheet showing the process for producing an ortho-methylated phenol compound of the prior invention;
The figure is a flow sheet showing the process of an embodiment of the present invention.

Claims (1)

[Claims] 1 Reacting phenol or/and orthocresol with methanol in the presence of a metal oxide to produce ortho-methylated phenol compounds, high-boiling byproducts and unreacted methanol,
Gaseous byproducts are separated from the reaction mixture containing phenol, unreacted methanol and produced water are separated from the resulting mixture, phenol is further separated by distillation, and orthogresol and 2,6-xylenol are separated. Then, in the method for producing an ortho-methylated phenol compound in which 2,6-xylenol is separated by distillation, the reaction is carried out by a fluidized bed reaction, and further, before the phenol is separated by distillation, the fine powder catalyst scattered from the reactor is removed. The ortho-methylated phenol is separated by distillation together with the high-boiling point substance, and the high-boiling substance that does not contain the ortho-methylated phenol compound remaining in the bottom liquid and the fine catalyst is recovered from the bottom liquid by thin film evaporation. Method of manufacturing the compound.