JPH085824B2 - Method for producing alkyl aryl carbinol - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an alkylaryl carbinol.

In particular, the present invention relates to a method for producing an alkylaryl carbinol by hydrogenating an aromatic ketone.

More specifically, in the method of hydrogenating an aromatic ketone, when a Raney nickel catalyst and a basic cocatalyst dissolved in an organic solvent having a low boiling point are used together, the basic cocatalyst is easily dissolved even after the organic solvent is distilled off. The present invention relates to a method for producing an alkylarylcarbinol, which is characterized in that a non-reducing high-boiling compound capable of being present and having a boiling point higher than that of the alkylarylcarbinol coexist.

(Prior Art) Unlike the hydrogenation reaction of an aliphatic ketone, the production of carbinol by the hydrogenation reaction of an aromatic ketone generally involves not only a carbonyl group but also an aromatic ring. Further, carbinol as a hydrogenation product is benzyl. Since it has an alcohol-type hydroxyl group, it is liable to undergo hydrogenolysis of the hydroxyl group, which makes it complicated.

Therefore, it is common practice to obtain the desired product by selecting an appropriate catalyst and reaction conditions.

When a Raney nickel catalyst is used for hydrogenating an aromatic ketone, for example, XADomingnoy et al. (J. Org. Chem. 26 1625 (19
61)) reported that hydrogen acetophenone was hydrogenated in an ethanol solvent using Raney nickel (W-6) to obtain methylphenylcarbinol in a yield of almost 100%.

However, Raney Nickel (W-6) proposed by Adkins et al.
Is a lab-prepared very active catalyst which is unsuitable for use in industrial scale production.

On the other hand, it is known that the reaction rate is improved by adding a small amount of alkali additive [Kusano et al.
Volume 261 (Showa 33)]. The effect of the alkali additive is not only the effect of improving the reaction rate but also the effect of suppressing the hydrogenolysis of the benzyl alcohol type hydroxyl group.

As the alkali additive, alkali metal salts of organic acids such as sodium acetate and other alkali metal hydroxides (eg sodium hydroxide, potassium hydroxide) are generally said to be effective [New Experimental Chemistry]. Lecture Volume 15 Oxidation and Reduction [II] Page 408].

In this case, since the alkali metal hydroxide has a strong basicity, it may cause an increase of by-product impurities or cause a corrosion problem of the reactor. Therefore, a basic substance such as sodium acetate is preferable as the alkali additive. For example, it has been reported that methylphenylcarbinol is quantitatively produced under relatively mild reaction conditions by adding sodium acetate to a Raney nickel catalyst [Kawaken Fine Chemicals Co., Ltd. technical report “Raney catalyst hydrogenation reaction]. ] P42 (1980)]. However, in practice, alkali metal salts of organic acids such as sodium acetate have very low solubility in aromatic ketones, so hydrogenation is carried out in the presence of a low boiling point catalyst such as methanol or ethanol. (Problems to be solved by the invention) However, if a low boiling point solvent such as methanol or ethanol is separated and recovered in the subsequent step of isolating and purifying the product, the crude alkylaryl carbinol remaining in the bottom liquid becomes sodium acetate or the like. Alkali metal salt or alkali metal hydroxide of the organic acid is precipitated.

This is because the alkali metal salt or alkali metal hydroxide of an organic acid such as sodium acetate has a small solubility in the alkylaryl carbinol itself, and this precipitated salt is generated continuously. Clogging of the perforated plate tower in the rectification process of
In addition, problems such as stains on the reboiler itself occur.

Therefore, operations such as filtration and decantation are carried out in order to remove these precipitates, but this is not preferable because the process becomes complicated in manufacturing on an industrial scale.

Therefore, the present inventor has conducted extensive studies to solve the above-mentioned problems, finally found a solution thereof, and completed the present invention.

(Structure of the Invention) That is, the present invention provides the following general formula (A). The aromatic ketone represented by the formula (B) is hydrogenated in the presence of a low-boiling solvent, a hydrogenation catalyst and a basic cocatalyst. In the method for producing an alkylaryl carbinol represented by, a non-reducing high boiling point compound capable of easily dissolving a basic cocatalyst and having a boiling point higher than that of the main product, alkyl aryl carbinol A method for producing an alkylaryl carbinol, characterized in that R'is a linear or branched alkyl group of C1 to C5 or a lower alkoxy group of C1 to C2 in the general formula (A) and the general formula (B). While R ²
Represents a lower alkyl group of C1 to C2)]. The essence of the present invention is that even after the alkali metal salt of an organic acid such as sodium acetate dissolved in a low boiling point organic solvent such as methanol or ethanol in the hydrogenation reaction charge solution is distilled off the low boiling point organic solvent such as methanol or ethanol. Coexistence of a sufficient amount of non-reducing high-boiling compound to dissolve can prevent the precipitation of salt after the hydrogenation reaction and after the completion of the desolvation step, and has no effect on the reaction results. is there. The method for carrying out the present invention will be described below.

 The aromatic ketones used as raw materials include the following.

Acetophenone, 4-methylacetophenone, 4-ethylacetophenone, 4-isobutylacetophenone, 4
-Methoxyacetophenone, 4-hydroxyacetophenone, propiophenone, 4-methylpropiophenone, 4-ethylpropiophenone, 4-hydroxypropiophenone and the like.

As the low boiling point organic solvent, methanol or ethanol can be used, and it is preferable to use 0.2 to 1 part by weight, preferably 0.3 to 0.6 part by weight, relative to the aromatic ketone. If the amount of the solvent is less than that, the reaction yield decreases, and if the amount is more than that, the recovery amount increases, the recovery energy and the recovery time become long, which is not preferable. Although various catalysts are used as the hydrogenation catalyst, it is preferable to use a Raney nickel catalyst that is inexpensive and has high activity. The Raney nickel catalyst is used in a concentration of 2 to 20% by weight, preferably 5 to 10% by weight, based on the aromatic ketone.
If the amount is less than 20% by weight, the reaction rate is low, and if the amount of the catalyst is more than 20% by weight, the hydrogenolysis reaction of the produced alkylaryl carbinol proceeds easily. The Raney nickel catalyst may be any one that is commercially available.

The base cocatalyst is preferably sodium acetate or potassium acetate. The base cocatalysts such as sodium acetate and potassium acetate are used in the range of 0.2 to 0.7 parts by weight, preferably 0.3 to 0.5 parts by weight, of the Raney nickel catalyst.

If the amount is less than 0.3 parts by weight, the co-catalyst effect cannot be said to be sufficient and the reaction rate is low.

On the other hand, if the amount exceeds 0.5 parts by weight, the precipitation of salt becomes remarkable, and above all, the usage rate becomes large, which is not economical as it is not recovered and the life of the catalyst may be shortened.

The requirement for the non-reducing high-boiling compound added to the reaction system is that it has a solubility in sodium acetate, potassium acetate, etc. even after distilling an organic solvent such as methanol or ethanol, and the boiling point of alkylallyl carbinol produced by hydrogenation. It must have a higher boiling point and be stable enough that it will not be hydrogenated. Glycerin (bp 290 ℃) is an example that meets these requirements. Of course, other than glycerin, it is optional as long as it satisfies the requirement. The amount added is sufficient to dissolve the cocatalyst even after distilling a low-boiling organic solvent such as methanol or ethanol, and is preferably about 10 times the weight of sodium acetate or potassium acetate. If the amount added is too small, salt precipitation will occur, and if it is too large, the concentration of the aromatic ketone charged to the reactor will decrease, and the production capacity will decrease. As the hydrogenation reaction conditions, the reaction conditions generally used for hydrogenating aromatic ketones can be applied. That is, the temperature for carrying out the hydrogenation reaction can be carried out in the range of 100 ° C to 200 ° C, but more preferably 150 to 180 ° C.

Otherwise, the reaction time will be longer, and conversely 18
At temperatures above 0 ° C, side reactions of aromatic ketones, such as hydrogenolysis of aromatic hydrogenated alkylaryl carbinols, are more likely to occur.

The hydrogenation pressure is about 100-150 kg / cm2G. At low pressure, the reaction rate is low, and at high pressure, there is a fear of side reactions and above all, manufacturing equipment that can withstand high pressure is required.

The Raney nickel catalyst is separated and removed from the thus obtained crude reaction liquid by filtration, and a low boiling point organic solvent recovery process such as methanol and ethanol is carried out, and then the rectification process is conducted.

Both the low-boiling point organic solvent recovery step and the rectification step can be carried out without any problems by using an ordinary general distillation apparatus.

The bottom liquid of the distillation column after recovering the low-boiling organic solvent is separated into uniform or two layers due to the mutual solubility of the non-reducing high-boiling compound and the alkylallyl carbinol, but no further precipitation of the cocatalyst is observed. The rectification of alkylallyl carbinol can be performed as it is. Therefore, the present invention can be easily carried out by using a conventional general reaction and purification apparatus without requiring any special equipment.

Also, since the co-catalyst is dissolved in the lower layer of the two-layer separated liquid, it can be recycled and used as it is in the next reaction. Hereinafter, the present invention will be described in detail with reference to Examples.

Example-1 1 L of an autoclave equipped with a magnetic stirrer, 360 g of acetophenone, 120 g of methanol, 100 of glycerin
g, Raney nickel catalyst 20 g and sodium acetate promoter 1
0 g was charged, and hydrogenation reaction was carried out while stirring at a hydrogen gas pressure of 90 kg / cm 2 and a temperature of 120 ° C. for 2 hours. The reaction crude liquid was analyzed by gas chromatography and it was confirmed that acetophenone was not detected.

After the Raney nickel catalyst was removed from the crude reaction liquid by suction filtration, methanol was distilled off at atmospheric pressure using a rotary evaporator.

 Thus, a concentrated solution of 352 g in the upper layer and 94 g in the lower layer was obtained.

Gas chromatographic analysis of the upper and lower two layers revealed that the upper layer was 97.55% pure methylphenylcarbinol and the lower layer was 92.67% pure glycerin. Example-2 Using the same autoclave as in Example-1, 4 isobutylacetophenone 200 g, methanol 100 g, glycerin 100
g, Raney nickel catalyst 20 g and sodium acetate promoter 1
Fill with 0g, hydrogen gas pressure 70KG / cm 2G., Temperature 140 ℃ 1
Allowed to react for hours.

The liquid obtained by filtering the Raney nickel catalyst from the obtained reaction crude liquid was uniform. Methanol was distilled off from this homogeneous solution with a rotary evaporator at atmospheric pressure. The concentrated liquid after distilling off methanol was also separated into two layers, but no precipitation of the sodium acetate promoter was observed. The results of gas chromatography analysis are shown below. Upper layer 203g 96.38% pure methyl (4-isobutyl) phenylcarbinol Lower layer 108g 90.67% pure glycerin The concentrated liquid separated into the upper and lower two layers is used as it is under reduced pressure (5 Torr) using a 30-column glass perforated plate tower. ) Fractionation was performed at a reflux ratio of 3 to obtain methyl (4-isobutyl) phenylcarbinol.

Main fraction: (column top temperature 111-112 ° C) 179g Purity: 98.23% Yield: 88.5% Example-3 Reaction was carried out in the same manner as in Example-2, and the concentrated liquid after catalyst separation and methanol distillation was removed. The upper and lower layers were separated. .

Since the sodium acetate co-catalyst was recovered in this lower layer solution, 100 g of the lower layer solution, 100 g of recovered methanol, 200 g of 4-isobutylacetophenone and 20 g of Raney nickel catalyst were used in the same autoclave as used in Example 1 for hydrogen gas pressure. The reaction was carried out at 70 KG / cm 2 G. and a temperature of 140 ° C. for 1.5 hours.

In this case, both the reaction charge and the reaction crude were separated into two layers. After the reaction crude liquid was filtered to remove the Raney nickel catalyst, methanol was distilled off, and the upper layer liquid was analyzed by gas chromatography, whereupon 4-isobutylacetophenone was not detected and 96.4% of methyl (4-isobutyl) phenylcarbinol was found. was detected. Comparative Example The reaction was performed in exactly the same manner as in Example 2 except that 200 g of glycerin was not used, and when Raney nickel catalyst separation and methanol distillation were carried out, crystals of the sodium acetate promoter were deposited. The precipitated salt had very poor filterability, and the bottom liquid was transferred by decantation, followed by rectification under reduced pressure. There is a loss during liquid transfer when performing decantation,
The yield of methyl (4-isobutyl) phenylcarbinol was 83.0%.

Claims (3)

[Claims] 1. The following general formula (A): The aromatic ketone represented by the formula (B) is hydrogenated in the presence of a low-boiling solvent, a hydrogenation catalyst and a basic cocatalyst. In the method for producing an alkylaryl carbinol represented by, a non-reducing high boiling point compound capable of easily dissolving a basic cocatalyst and having a boiling point higher than that of the main product, alkyl aryl carbinol A method for producing an alkylaryl carbinol, which comprises coexisting with. (In the general formula (A) and the general formula (B), R'is C1 to
A straight-chain or branched alkyl group up to C5, a lower alkoxy group of C1 to C2, while R ² represents a lower alkyl group of C1 to C2) 2. The method according to claim 1, wherein the hydrogenation catalyst is Raney nickel. 3. The method according to claim 1, wherein the basic catalyst is sodium acetate or potassium acetate.
The manufacturing method according to the item.