JPH09151151A - Production of 4-methoxyphenol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain 4-methoxyphenol in high conversion and selectivity in a low cost by allowing hydroquinone to react with methanol under specific conditions. SOLUTION: Hydroquinone and methanol are allowed to react with each other in the presence of a solid acid catalyst such as silica-alumina by using a flow reactor at 200-350 deg.C under a pressure of 0.5-10Mpa. The molar ratio of methanol to hydroquinone is 3-30, and they are continuously fed to the solid acid catalyst and the weight time space velocity(WTSV) is set to 0.5-30hr<-1> . 4-Methoxyphenol is useful, for example, as a polymerization inhibitor for acrylic or methacrylic acid derivatives, a storage stabilizer for photosensitive materials, an antioxidant, an ink corrosion inhibitor, an acrylamide gel collapse preventive, a fiber-swelling agent and further as a synthetic intermediate for agrochemicals, medicines, dyes and the like.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing 4-methoxyphenol, and more specifically, to 4-methoxyphenol from hydroquinone and methanol at a high conversion rate, a high selectivity and a low cost, and industrially. In particular, the present invention relates to a manufacturing method.

[0002]

BACKGROUND OF THE INVENTION 4-Methoxyphenol is used as a polymerization inhibitor for acrylic acid-based or methacrylic acid-based compounds, for example, storage stabilizers for photosensitive materials, antioxidants, corrosion inhibitors for inks, acrylamide gels. It is a very useful compound, for example, it is used as a disintegration preventive, a fiber swelling agent, and as a synthetic intermediate for agricultural chemicals, pharmaceuticals, dyes, and the like. This 4-methoxyphenol has hitherto been industrially produced by methylating hydroquinone with dimethylsulfate, but in this method, a large amount of waste sulfuric acid is generated and dimethylsulfate is extremely toxic. Therefore, it has drawbacks such as complicated handling. Therefore, various methods for producing 4-methoxyphenol without using such dimethylsulfate have been studied. For example, (1) reacting hydroquinone and methanol under atmospheric pressure in the presence of an acid catalyst such as sulfuric acid or heteropolyacid. Method (Japanese Patent Laid-Open No. 4-305546),
(2) A method of reacting a mixture of hydroquinone and benzoquinone with methanol in the presence of an acidic dehydration catalyst such as an acidic sulfonated cation exchange resin at room temperature to reflux temperature under normal pressure (JP-B-60-41649). , (3)
A method of reacting hydroquinone and methanol in a gas phase using an Al-BP-Si-O composite oxide catalyst (Japanese Patent Publication No. 55-6618) has been proposed.

However, since the above method (1) is a reactive distillation method, it is necessary to set fine conditions such as the vapor rate, and further, when the inventors conducted a follow-up experiment, the conversion of hydroquinone was found. Is about 40% and the selectivity of 4-methoxyphenol is about 50%, which is higher than the values described in the publication (hydroquinone conversion rate of about 88%, 4-methoxyphenol selectivity of about 97%). It was quite low. Further, in this additional test, about 7% of phenol was produced as a light component, and about 35% of dehydrated dimer of hydroquinone or 4-methoxyphenol was produced as a heavy component. On the other hand, the method (2) has the advantage that the reaction conditions are mild and the conversion and selectivity are relatively high, but it is expensive, unstable and highly toxic to benzoquinone as compared with 0.05 of hydroquinone. This is not always an advantageous method for industrial implementation, because it requires about 0.1 to 0.1 times the weight, the recovery operation is complicated, and the reaction takes a long time. Furthermore, since the method (3) is a gas phase reaction, hydroquinone is precipitated in the low temperature part of the reaction system,
There is a possibility that it may be clogged, and since dimethyl ether of hydroquinone is considerably by-produced, the selectivity of 4-methoxyphenol is not so high.

[0004]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional methods for producing 4-methoxyphenol, and the conversion of hydroquinone and the selectivity of 4-methoxyphenol are both high and low. It is an object of the present invention to provide an industrially advantageous method capable of producing 4-methoxyphenol at high cost with high productivity.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that hydrquinone and methanol are continuously supplied to a solid acid catalyst layer, and liquid phase is obtained under specific reaction conditions. It was found that the reaction can achieve the purpose. The present invention has been completed based on such findings. That is, the present invention provides (1) continuously supplying hydroquinone and methanol to the solid acid catalyst layer,
The present invention provides a method for producing 4-methoxyphenol, which is characterized in that a liquid phase reaction is carried out under the conditions of a pressure of 0.5 to 10.0 MPa and a temperature of 200 to 350 ° C. Further, a preferred embodiment for carrying out the present invention is (2) pressure 2.0 to 7.0.
The above method (1) in which a liquid phase reaction is carried out under the conditions of MPa and a temperature of 205 to 300 ° C., and (3) space-time velocity by weight (WHS).
V) The liquid phase reaction is carried out at a molar ratio of 0.5 to 30 hr ⁻¹ and a methanol / hydroquinone molar ratio of 3 to 30 (1), (2)
Method, (4) the molar ratio of methanol / hydroquinone is 5
To (25) above, and (5) the method of (1) to (4) above, wherein the solid acid catalyst is at least one selected from silica alumina, silica magnesia, silica zirconia, and synthetic zeolite. ,.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention is a method for producing 4-methoxyphenol by reacting hydroquinone and methanol under pressure in a liquid phase flow system using a solid acid catalyst. The solid acid catalyst used in the method of the present invention is not particularly limited, and conventionally known ones such as silica alumina, silica magnesia, silica zirconia, synthetic zeolite, heteropoly acid, various sulfates, various phosphates, and phosphoric acid. Examples include supported diatomaceous earth. here,
Examples of synthetic zeolite include Y-type zeolite and ZS
M-5 type zeolite and the like are preferably mentioned, and examples of the heteropolyacid include silicotungstic acid having silicon as a central atom, silicomolybdic acid, phosphotungstic acid having phosphorus as a central atom, and phosphomolybdic acid. Among these, silica alumina, silica magnesia, silica zirconia and synthetic zeolite are particularly preferable from the viewpoint of catalytic activity and life. These solid acid catalysts may be used alone or in combination of two or more. The shape of the catalyst is not particularly limited, and any shape such as spherical, pellet-like, powder-like, and granular can be used, but spherical, pellet-like, or granular ones are packed in a column or the like, It is preferable to continuously pass hydroquinone and methanol. Even the powder form can be packed in a column and operated in a fluidized bed form.

The proportion of methanol and hydroquinone used is
The methanol / hydroquinone molar ratio is preferably selected so as to be in the range of 3 to 30. When this molar ratio is less than 3, heating and stirring operation is required to obtain a uniform mixture of methanol and hydroquinone, which is not preferable, and when it exceeds 30, the basic unit of methanol is lowered, and the productivity of 4-methoxyphenol is also reduced. It becomes too low, which is not preferable. From the viewpoint of the balance between the conversion of hydroquinone and the selectivity of 4-methoxyphenol, more preferable methanol /
The molar ratio of hydroquinone is in the range of 5-25. As a method of supplying hydroquinone and methanol to the solid acid catalyst layer, since the melting point of hydroquinone is as high as 169 ° C., hydroquinone is dissolved in methanol to prepare a methanol solution of hydroquinone, and this solution is continuously added to the solid acid catalyst layer. It is advantageous to supply The weight hourly space velocity (WHSV) is usually selected in the range of 0.5 to 30 hr ^-1 . When this WHSV is less than 0.5 hr ^-1 , the basic unit of methanol is extremely lowered, the selectivity of 4-methoxyphenol is too low, and the productivity is poor, which is not preferable, and when it exceeds 30 hr ^-1 , hydroquinone is obtained. The conversion rate of the catalyst becomes too low, and a special device is required to remove the heat of reaction in the vicinity of the catalyst layer inlet. A more preferable WHSV is in the range of ¹ to 20 hr ^{−1 in} terms of the selectivity and productivity of 4-methoxyphenol, the conversion rate of hydroquinone, and the utility cost.

In this liquid phase flow reaction, the reaction temperature is selected in the range of 200 to 350 ° C. This temperature is 20
If the temperature is below 0 ° C, the reaction hardly progresses, and at 350 ° C
If it exceeds, the amount of by-products will increase, the selectivity of 4-methoxyphenol will remarkably decrease, and the activity of the catalyst will decrease significantly due to coking and the like. From the standpoint of balance between the conversion of hydroquinone and the selectivity of 4-methoxyphenol, the preferred reaction temperature is in the range of 205 to 300 ° C, particularly 220 to 270 ° C. Furthermore, the reaction pressure is 0.5 so that at least a part of methanol can exist as a liquid phase depending on the reaction temperature.
It is selected in the range of up to 10.0 MPa. This pressure is 0.5M
If it is less than Pa, methanol cannot exist as a liquid phase at the reaction temperature, and a pressure exceeding 10.0 MPa is not necessary. If it exceeds 10.0 MPa, the equipment cost becomes too high, which is economically disadvantageous. Is. The preferable reaction pressure is in the range of 2.0 to 7.0 MPa from the viewpoints of maintaining sufficient liquid phase of methanol and economical efficiency. Further, in the present invention, hydrous methanol containing up to about 50% by weight of water as methanol can also be used. In this case, under the same reaction conditions, the conversion of hydroquinone decreases as the content of water increases, but by increasing the reaction temperature, the conversion is increased, and when methanol containing no water is used. Approximately the same hydroquinone conversion and 4-methoxyphenol selectivity can be obtained. In addition, when the solid acid catalyst deteriorates due to long-term operation and the catalyst activity decreases, it is possible to obtain a temperature of 450 to 60 under air flow.
It can be regenerated by baking at a temperature of about 0 ° C. The reaction mixture obtained by such a liquid phase flow reaction is subjected to known means conventionally used, for example, distillation treatment, to obtain unreacted methanol;
4-dimethoxybenzene; 4-methoxyphenol and unreacted hydroquinone can be recovered. Further, the recovered methanol and hydroquinone can be recycled to the reaction system and reused.

[0009]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. 1 is a schematic view of the apparatus used in the experiment, and FIG. 2 is a detailed view of the reactor body. The experimental operation was performed as follows. First, stainless steel reactor 1
After filling the c portion of (inner diameter 10 mm, length 50 cm, thermocouple tube outer diameter 3 mm double tube, inner volume 36 ml) with 16.66 g of α-alumina, the upper portion b had a diameter of 0.8 to 1 .
12.55 g of a silica-alumina catalyst [N631 manufactured by JGC Chemicals Co., Ltd.] sieved to 2 mm was charged, and 14.38 g of α-alumina was further charged on the upper part a. afterwards,
While activating the air A at a rate of 300 ml / min through the flow meter 10, the catalyst was activated at 500 to 550 ° C. for 2 hours for calcination. Then, after cooling to room temperature, the tank 2
Then, a methanol solution of hydroquinone was introduced by the pump 3, and the inside of the reaction system was liquid-sealed and controlled by the pressure regulator 6 so as to have a predetermined pressure. Next, after adjusting the pump stroke so as to attain a predetermined WHSV, the reaction system was heated to a predetermined temperature and a liquid phase flow reaction was performed. As for the reaction temperature, the heater output was controlled so that the target temperature was reached at the three points of points A, B and C of the reactor body shown in FIG. The reaction temperature can be measured at all points on the catalyst layer by sliding a thermocouple. The reaction mixture flowing out of the reactor 1 is the condenser 7
After being cooled by, it is supplied to the product liquid receiving tank 4 through the filter 8 and the pressure regulator 6. After weighing this product solution,
Analyzed by gas chromatography. On the other hand, the produced gas is dried ice /
It was aggregated and collected with an isopropanol refrigerant and weighed. In addition, B is nitrogen, 11 is a nitrogen flow meter, C is a waste gas, and 9 is a pressure gauge. In addition, in gas chromatography analysis, DB1701 (30 m × 0.25 mm) is used as a column.
φ) was used.

Examples 1 to 10 Under the conditions of a methanol / hydroquinone molar ratio of 30 or 10, a target reaction temperature of 250 ° C. and a reaction pressure of 4.1 MPa,
The WHSV was changed as shown in Table 1 and the liquid phase flow reaction was performed for the operating time shown in Table 1 to determine the liquid recovery rate, the gas recovery rate in some cases, the hydroquinone conversion rate, and the product liquid composition.
The composition of the product liquid is the weight% of each component when the remaining components excluding unreacted methanol and hydroquinone are 100. The reaction conditions and results are shown in Table 1. FIG.
4 and FIG. 4 are graphs showing the relationship between the WHSV and the hydroquinone conversion rate and the composition of the product solution at the methanol / hydroquinone molar ratios of 30 and 10, respectively.

[0011]

[Table 1]

[0012]

[Table 2]

The abbreviations used in the tables and figures have the following meanings (the same applies hereinafter). HQ: Hydroquinone DMB: 1,4-dimethoxybenzene Me-DMB: Nuclear methylated 1,4-dimethoxybenzene MQ: 4-methoxyphenol (methoquinone) Me-MQ: Nuclear methylated metquinone Me-HQ: Nuclear Methylated hydroquinone As can be seen from the table and the figure, when the methanol / hydroquinone molar ratio is 30, the hydroquinone conversion rate decreases as the WHSV increases, and the 4-methoxyphenol content (selectivity) increases. There is a tendency to increase. On the other hand, when the molar ratio of methanol / hydroquinone is 10, and the WHSV is 4 hr ⁻¹ or more, the hydroquinone conversion rate and the 4-methoxyphenol content (selectivity) are almost constant. This is probably because the higher the WHSV, the higher the temperature of the catalyst layer due to heat generation. In the figure, ○
Indicates the HQ conversion rate (%), Δ indicates the ratio of DMB in the production liquid (% by weight), and □ indicates the ratio of MQ in the production liquid (% by weight) (the same applies to the following figures).

Examples 11 and 12 Methanol / hydroquinone molar ratio 30, pressure 4.1 MP
a and WHSV 0.85 hr ⁻¹ , the target reaction temperature was set to 200 ° C. (Example 11) and 230 ° C. (Example 12) and the liquid phase flow reaction was performed for the operating time shown in Table 2. The recovery rate, hydroquinone conversion rate and product composition were determined.
The reaction conditions and results are shown in Table 2. The reaction conditions and results of Example 1 are also shown in Table 2. FIG. 5 is a graph showing the relationship between the reaction temperature, the hydroquinone conversion rate, and the composition of the product solution.

[0015]

[Table 3]

As is apparent from the table and the figures, when the reaction temperature is 200 ° C., the hydroquinone conversion rate is as small as about 4%, and it is understood that the reaction hardly progresses below 200 ° C. Examples 13 and 14 Target reaction temperature 250 ° C., reaction pressure 4.1 MPa and WHS
Under the condition of V1.0-1.1 hr ^-1 , the molar ratio of methanol / hydroquinone was 20 (Example 13) and 10 (Example 1).
4) and the liquid phase flow reaction was performed for the operating time shown in Table 3 to determine the liquid recovery rate, hydroquinone conversion rate and product liquid composition. The reaction conditions and results are shown in Table 3. The reaction conditions and results of Example 1 are also shown in Table 3. FIG. 6 is a graph showing the relationship between the molar ratio of methanol / hydroquinone, the conversion of hydroquinone, and the composition of the product solution.

[0017]

[Table 4]

From the tables and figures, it can be seen that as the molar ratio of methanol / hydroquinone increases, the conversion of hydroquinone increases and the content (selectivity) of 4-methoxyphenol decreases. Examples 15 to 21 A liquid phase flow reaction was performed under the reaction conditions shown in Table 4 using water-containing methanol, and the liquid recovery rate, the gas recovery rate in some cases, the hydroquinone conversion rate, and the product liquid composition were determined. The results are shown in Table 4. The reaction conditions and results of Example 6 are also shown in Table 4.

[0019]

[Table 5]

[0020]

[Table 6]

As can be seen from this table, under the same reaction conditions, the hydroquinone conversion rate decreases as the water content in methanol increases, but the hydroquinone conversion rate can be increased by raising the reaction temperature. . Example 22 Using a used catalyst as a catalyst, a liquid phase flow reaction was carried out under the reaction conditions shown in Table 5. In this case, the catalyst activation treatment was not performed. The results are shown in Table 5. After completion of the above experiment, the catalyst was calcined at 500 to 550 ° C. for 4 hours while flowing air into the reactor at 300 ml / min for regeneration treatment, and then liquid phase flow reaction was performed under the same reaction conditions as above. Was carried out. The results are shown in Table 5.

[0022]

[Table 7]

From this table, it can be seen that the cereal mina catalyst can be regenerated by calcining while circulating air. Comparative Examples 1 to 8 After hydroquinone-containing methanol solution was evaporated through a preheating section, silica alumina (manufactured by JGC Chemical Co., Ltd., N631) 10.76 g was used together with 300 ml / min of nitrogen.
Reactor packed with (same as used in the examples)
Was supplied by downflow, and a gas phase flow reaction was carried out under the reaction conditions shown in Table 6 at a pressure of 0.1 MPa. The results are shown in Table 6.

[0024]

[Table 8]

[0025]

[Table 9]

[Note] In Comparative Example 1, the reactor was blocked after one hour of operation, and it was impossible to continue operation further.
In Comparative Example 2, the reactor inlet was blocked after the operation time was 1.3 hours, and it was impossible to continue the operation any further. In Comparative Example 4, when the target temperature was changed from 280 ° C to 250 ° C, the reactor outlet was blocked. In Comparative Example 8, the reactor was clogged after an operating time of 2.5 hours. As can be seen from Table 6, with respect to the 4-methoxyphenol content (selectivity) in the product liquid at the same hydroquinone conversion rate, this gas phase normal pressure distribution reaction was compared with the liquid phase pressure distribution reaction of Example. In this case, the former has a much lower 4-methoxyphenol content (selectivity). It is also found that in the gas-phase normal-pressure flow reaction, hydroquinone may be precipitated and clogged in the low temperature part of the reaction system.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, 4-methoxyphenol can be industrially advantageously produced from hydroquinone and methanol by a liquid-phase pressure distribution reaction with high conversion, high selectivity and low cost. it can. The 4-methoxyphenol obtained by the method of the present invention includes, for example, a polymerization inhibitor such as an acrylic acid-based or methacrylic acid-based compound, a storage stabilizer for a light-sensitive material, an antioxidant, an ink corrosion inhibitor, an acrylamide gel. It is used as a disintegration preventive, fiber swelling agent, etc., and also as a synthetic intermediate for agricultural chemicals, pharmaceuticals, dyes and the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus used in an experiment in the present invention.

FIG. 2 is a detailed view of a reactor body in the apparatus of FIG.

FIG. 3 is a graph showing an example of the relationship between WHSV, hydroquinone conversion rate, and product liquid composition in the method of the present invention.

FIG. 4 is a graph showing another example of the relationship between WHSV, hydroquinone conversion rate, and product liquid composition in the method of the present invention.

FIG. 5 is a graph showing an example of the relationship between the reaction temperature, the hydroquinone conversion rate, and the composition of the product liquid in the method of the present invention.

FIG. 6 is a graph showing an example of the relationship between the methanol / hydroquinone molar ratio, the hydroquinone conversion rate, and the composition of the product liquid in the method of the present invention.

[Explanation of symbols]

 1: Reactor 2: Hydroquinone-containing methanol solution tank 3: Pump 4: Product solution receiving tank 5: Trap 6: Pressure regulator 7: Condenser 8: Filter 9: Pressure gauge 10: Flowmeter 11: Flowmeter A: Air B: Nitrogen C: Waste gas a: α-alumina filling part b: Silica-alumina catalyst filling part c: α-alumina filling part a: Temperature control point B: Temperature control point C: Temperature control point

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C07C 41/09 7419-4H C07C 41/09 // C07B 61/00 300 C07B 61/00 300

Claims (5)

[Claims] 1. Hydroquinone and methanol are continuously supplied to a solid acid catalyst layer to obtain a pressure of 0.5 to 10.0 MPa and a temperature of 2.
A method for producing 4-methoxyphenol, which comprises subjecting a liquid phase reaction to a condition of 00 to 350 ° C. 2. A pressure of 2.0 to 7.0 MPa and a temperature of 205 to 3
The method according to claim 1, wherein the liquid phase reaction is carried out under the condition of 00 ° C. 3. Weight hourly space velocity (WHSV) 0.5 to 30 h
The method according to claim 1, wherein the liquid phase reaction is carried out at a molar ratio of r ^-1 and methanol / hydroquinone of 3 to 30. 4. A methanol / hydroquinone molar ratio of 5 to 5.
25. The method according to claim 3, which is 25. 5. The method according to claim 1, wherein the solid acid catalyst is at least one selected from silica alumina, silica magnesia, silica zirconia, and synthetic zeolite.