JPS6330432A - Hydrogenation of aromatic ketone - Google Patents

Abstract

PURPOSE:In the production of a alkylarylcarbinol by hydrogenation of an aromatic ketone, a combination of Raney nickel catalyst with an organic amine cocatalyst enables the increase in the reaction rate with inhibition of side- reactions and no salt precipitation. CONSTITUTION:The catalytic hydrogenation of an aromatic ketone of the formula (R<1> is 1-5C straight-chain or branched alkyl, 1-2C alkoxy; R2 is 1-2C lower alkyl) is conducted in the presence of 2-20wt%, preferably 5-10wt%, based on the ketone, of Raney nickel catalyst and 0.2-0.8wt%, preferably 0.4-0.6wt%, based on the Ni catalyst, of an organic amine cocatalyst, preferably pyridine or triethylamine, at a temperature of 100-200 deg.C, preferably 150-180 deg.C under a pressure of 50-150, preferably 70-100kg/cm<2>G. Thus, side-reactions such as hydrogenolysis are inhibited without precipitation of the cocatalyst and the objective an alkylarylcarbinol is obtained in a shortened time.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for hydrogenating aromatic ketones.

In particular, the present invention relates to a method for producing alkylaryl carbinols by hydrogenating aromatic ketones.

More specifically, in the method of hydrogenating aromatic ketones,
The present invention relates to a hydrogenation method characterized by using a Raney nickel catalyst and an organic amine promoter in combination.

(Prior Art) and (Problems to be Solved by the Invention) The production of carbinol by the hydrogenation reaction of aromatic ketones differs from the hydrogenation reaction of aliphatic ketones in that not only the carbonyl group but also the aromatic ring participates in the reaction. Furthermore, since the hydrogenation product carbinol has benzyl alcohol type water, it is susceptible to subsequent hydrogenolysis of the hydroxyl group, which complicates the process.

Therefore, the desired product is usually obtained by selecting an appropriate catalyst and reaction conditions.

When Raney nickel catalysts are used for the hydrogenation of aromatic ketones, e.g.
rg, Chera, 261625 (1961)
) reported hydrogenation of acetophenone in ethanol solvent using Raney nickel (W-6) to obtain methylphenyl carbinol in nearly 100% yield.

However, Raney nickel (W-
6) is a highly active catalyst prepared in the laboratory and is unsuitable for use in industrial scale production.

On the other hand, it is known that the reaction rate is improved by a small amount of alkaline additive [Kusano et al. Pharmaceutical Research 30
Volume 261 (Showa 33)].

The effect of this alkaline additive is not only to improve the reaction rate but also to suppress hydrogenolysis of benzyl alcohol type hydroxyl groups.

For example, it has been reported that methylphenyl carbinol is quantitatively produced under relatively mild reaction conditions by adding sodium acetate to a Raney nickel catalyst [Yoken Fine Chemical ■Technical Report [Hydrogenation Reaction Using Raney Catalyst JP]
42 (1980)].

As this alkali additive, alkali metal salts of organic acids such as sodium acetate, and other alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide) are generally considered to be effective [New Experiments] Chemistry Course Volume 15 Oxidation and Reduction (It) P4o8 pages].

However, organic amines, which are also basic substances, generally poison the catalyst in many cases, so their selection must be made carefully, and in fact, there have been no reports on the hydrogenation of aromatic ketones using Raney nickel catalysts.

However, since alkali metal salts of organic acids or alkali metal hydroxides have very low solubility in aromatic ketones, a solvent such as methanol or ethanol is required.

In general, when the solvent is separated and recovered in the post-isolation process of the product, alkali metal salts of organic acids such as sodium acetate or alkali metal hydroxides are precipitated from the crude alkylaryl carbinol that remains as the bottom liquid. I'll come.

This also applies to alkylaryl carbinol, such as sodium acetate! This is because the alkali metal salts or alkali metal hydroxides have only a small solubility.
The generation of this precipitated salt causes problems such as clogging of the perforated plate tower and fouling of the reboiler itself in the subsequent rectification process of alkylaryl carbinol.

Therefore, in order to remove this precipitate, operations such as filtration and decantation are performed, but this is not preferable in industrial scale production because it complicates the process.

Therefore, the inventor of the present invention made repeated studies to solve the above-mentioned problem, and
It was discovered that by adding and using pyridine or triethylamine as a co-catalyst to the Raney nickel catalyst, the hydrogenation of aromatic ketones proceeds rapidly with fewer side reactions such as hydrogenolysis of alkylaryl carbinol. 0 Completed the present invention. I let it happen.

(Structure of the Invention) That is, the present invention is based on the general formula (1) (wherein R' represents a C1 to C5 straight chain or branched alkyl group or a C1 to C2 lower alkoxy group;
2 represents a C1-C2 lower alkyl group, the hydrogenation method for an aromatic ketone is characterized by using a Raney nickel catalyst and an organic amine promoter in combination. .

Pyridine and triethylamine to be added are both liquid substances at room temperature, and are unlikely to cause a problem of precipitation.

Furthermore, the action of these organic amines as catalyst poisons poses almost no problem in the practice of the present invention.

The conditions for implementing 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.

A solvent may or may not be used, but when used, alcohols such as methanol and ethanol are preferred;
The amount used is preferably 0.6 parts by weight or less based on the aromatic ketone.

If no solvent is used, strong stirring is required because the dispersibility of Raney nickel is not good, and the use of more than 0.6 parts by weight of solvent is preferable because it increases the recovery energy and recovery time and above all reduces the production capacity. do not have.

The concentration of Raney nickel catalyst used is 2 to 20% by weight, preferably 5 to 10% by weight, based on the aromatic ketone,
At 2t less than 2% by weight, the reaction rate is low, and at 20% by weight
When a larger number of catalysts are used, the water J decomposition reaction of the generated alkylaryl carbinol becomes more likely to occur.

Any commercially available Raney nickel catalyst may be used.

The base promoter, pyridine or triethylamine, is preferably used in an amount of 0.2 to 0, atia parts, preferably 0.4 to 0.6 parts, of the Raney nickel catalyst.

When the amount is less than 0.4 parts by weight, the promoter effect is not sufficient and the reaction rate is low.

On the other hand, if the amount exceeds 0.6 weight and 1 part, the life of the catalyst may be shortened.

The temperature at which the hydrogenation reaction is carried out can range from 100°C to 200°C, more preferably from 150°C to 180°C.

If it is less than that, the time required for the reaction will be longer, and on the other hand, 18
At temperatures above 0''C, side reactions of aromatic ketones, such as hydrogenolysis of hydrogenated alkylarylcarbinol in the aromatic nucleus, are more likely to occur.

The hydrogenation pressure may be in the range of 50 to 150 KG/cm 2 G, more preferably 70 to 1o.

KG/cm　2G, about.

At low pressures, the reaction rate is low, and at high pressures, there is a risk of n1 reaction, and above all, manufacturing equipment that can withstand high pressures is required.

The Raney nickel catalyst is separated and removed from the resulting reaction crude liquid by filtration, and then the reaction mixture is led to a rectification step.

If a solvent is used, a solvent recovery step is required prior to rectification of the alkylaryl carbinol product.

Both this process and the precision process can be carried out without any problem by using a common distillation apparatus.

Therefore, the present invention does not require any special equipment and can be carried out easily by using conventional general reaction and purification equipment.

Examples will be given below to explain the present invention in detail.

Example-1 In a 1L autoclave equipped with a magnetic stirrer, 4-isobutylacetophenone 2009, methanol 100g, and pyridine 109. 20 g of Raney nickel was added to the H2 pressure cuff at 0 G/cm2G, and hydrogenation was carried out with stirring at 140° C. for 4 hours.

The reaction crude liquid was analyzed by gas chromatography and it was confirmed that 4-isobutylacetophenone was not detected.

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

Thus, 215 g of concentrate was obtained.

This concentrated liquid was rectified using a 30-stage glass perforated plate column under reduced pressure (5 Torr) at a reflux ratio of 3, and 176 g of methyl (4-
Isobutyl) phenyl carbinol was obtained.

Purity 98.11 Yield 8
7% Example-2 Using the same autoclave as Example-1, 200 g of acetophenone, 5 methanol (1, 1 triethylamine)
5g, Raney nickel 30SF to pressure cuff 0 G/cm2
G. The reaction was carried out at a temperature of 140° C. for 4 hours.

Gas chromatography revealed that 95% of the raw material acetophenone had been converted to methylpheno-)lecarpinol.

Claims (1)

[Claims] i) General formula (1) ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (1) (In the formula, R^1 is a straight chain or branched alkyl group from C1 to C5, a lower C1 to C2 (representing an alkoxy group, while R^2 represents a C1-C2 lower alkyl group), characterized in that a Raney-nickel catalyst and an organic amine cocatalyst are used in combination. A method for hydrogenating aromatic ketones. ii) The method for hydrogenating aromatic ketones according to claim i), wherein the organic amine cocatalyst is pyridine or triethylamine.