Catalyst for preparing alpha-phenethyl alcohol by hydrolyzing acetophenone and its preparation and application

Abstract

The application discloses a catalyst for preparing alpha-phenethyl alcohol through acetophenone hydrogenation and a preparation method and application thereof. The method comprises the following steps: (1) respectively preparing solution I comprising a nickel-containing salt, an aluminum-containing salt, an active agent and water and solution II comprising a sodium-containing salt, a silicon-containing salt and water; (2) adding bottom water into a reaction kettle, adjusting pH, and controlling the temperature of the reaction kettle; (3) adding solution I and solution II in parallel, adjusting flow to keep the pH value, and after the parallel flow is completed, reacting under stirring; (4) after the reaction is completed, filtering and beating, and the obtained filter cake is subjected to first drying, crushing, shaping, second drying and calcination to obtain a nickel-based catalyst. The catalyst is suitable for an alpha-phenethyl alcohol reaction generated through selective hydrogenation of acetophenone, can greatly improve the processing load of the catalyst, has high activity, and meanwhile, the selectivity of alpha-phenethyl alcohol is high, and the generation of by-products can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a catalyst for preparing alpha-phenethyl alcohol by hydrogenation of acetophenone and a preparation method and application thereof. BACKGROUND

[0002] Alpha-phenethyl alcohol is an important chemical intermediate, which is widely used in medicine, perfume manufacturing, food, fine chemical industry and other industries. The existing alpha-phenethyl alcohol synthesis methods mainly include natural extraction, microbial fermentation, organic synthesis and other methods. The raw material source of natural extraction is limited, the price of microbial fermentation is expensive, while the organic synthesis has the advantages of low production cost, less by-products, high product yield and high product purity.

[0003] There are multiple side reactions in the preparation of alpha-phenethyl alcohol by hydrogenation of acetophenone, and it is of important application value to develop a heterogeneous hydrogenation catalyst with high activity, high selectivity and easy separation. The hydrogenation catalysts mainly include noble metal catalysts such as platinum, palladium and rhodium, and non-noble metal catalysts such as nickel and copper, and the non-noble metal catalysts have the advantage of low cost.

[0004] The commonly used catalyst for preparing alpha-phenethyl alcohol by hydrogenation of acetophenone in the industry is Raney Ni catalyst, and the selectivity of the product alpha-phenethyl alcohol is only about 82%. Although the hydrogenation selectivity can be increased to 89% by adding an appropriate amount of Cr, but the heavy metal Cr is more serious to the environment pollution, and the environmental protection pressure is increased.

[0005] CN109529870A discloses a kind of acetophenone hydrogenation catalyst and its preparation method, which uses co-precipitation and extrusion forming method to prepare a multi-component catalyst containing 60-70wt% copper oxide, 22-35wt% silicon dioxide, and elements such as Mn, Bi and Pb, for catalyzing acetophenone hydrogenation reaction, under the conditions of 80℃, 2.5MPa, hydrogen ketone molar ratio 2:1 and liquid hourly space velocity 0.3h -1 The acetophenone conversion rate can reach 99.3%, and the alpha-phenethyl alcohol selectivity is 99.3%, but the catalyst reaction load is low, the product space-time yield is low, and the production cost is high.

[0006] CN1557545A discloses a kind of acetophenone hydrogenation amorphous nickel boron catalyst and its preparation method, which uses impregnation method to prepare amorphous catalyst (NiSn-B / SiO2), and uses KBH4 or KBH4 to add B element to prepare catalyst. When used for catalyzing acetophenone hydrogenation reaction, the alpha-phenethyl alcohol selectivity can reach 97.5%, but the catalyst reduction step is complicated and the cost is high.

[0007] CN115445629A discloses a catalyst for the hydrogenation of acetophenone to alpha-phenethyl alcohol and its preparation method and application. The catalyst is prepared by using alumina as the carrier, copper oxide as the active component, and various rare metals as the additives. The catalyst is used for selective hydrogenation of acetophenone. The reaction temperature is 72℃. The reaction raw material is 25% alpha-phenethyl alcohol in cumene solution. The reaction pressure (gauge pressure) is 2MPa. The hydrogen / alpha-phenethyl alcohol molar ratio is 10:1. The liquid hourly space velocity is 0.4-0.8g ACP ·g cat -1 ·h -1 Under the above conditions, the conversion rate of alpha-phenethyl alcohol is more than 98.5%, and the selectivity of phenethyl alcohol is greater than or equal to 99%. However, the catalyst has low operating load, large catalyst consumption, and high production cost.

[0008] CN1911883A discloses a synthesis method of alpha-phenethyl alcohol. Raney nickel is used as the catalyst, and acetophenone, methanol and water are used as the reaction raw materials in a certain proportion. Under different proportions of raw materials, the selectivity of alpha-phenethyl alcohol can reach 94.3% at most, and the conversion rate of acetophenone is 72.38%, which is relatively low and needs to be further improved. SUMMARY

[0009] In view of the above problems in the prior art, the present application provides a catalyst for the hydrogenation of acetophenone to alpha-phenethyl alcohol and its preparation method and application. The catalyst is suitable for the reaction of selective hydrogenation of acetophenone to alpha-phenethyl alcohol, can greatly improve the processing load of the catalyst, has high activity, and can effectively reduce the generation of by-products.

[0010] The first aspect of the present application provides a preparation method of a catalyst for the hydrogenation of acetophenone to alpha-phenethyl alcohol, comprising the following steps:

[0011] (1) respectively preparing solution I comprising a nickel-containing salt, an aluminum-containing salt, an active agent and water (preferably deionized water) and solution II comprising a sodium-containing salt, a silicon-containing salt and water (preferably deionized water);

[0012] (2) adding bottom water to the reaction kettle and adjusting the pH value while controlling the temperature of the reaction kettle;

[0013] (3) adding solution I and solution II in parallel, adjusting the flow rate to maintain the pH value, and after the parallel flow is completed, performing an aging reaction under stirring;

[0014] (4) after the reaction is completed, filtering and beating, and the obtained filter cake is subjected to first drying, crushing, molding, second drying and calcination to obtain the catalyst.

[0015] In the present application, in step (1), the nickel-containing salt is at least one of nickel nitrate and nickel sulfate, preferably nickel nitrate; the aluminum-containing salt is at least one of aluminum nitrate and aluminum sulfate, preferably aluminum nitrate; the sodium-containing salt is at least one of sodium carbonate and sodium bicarbonate, preferably sodium carbonate; and the silicon-containing salt is at least one of sodium silicate and potassium silicate, preferably sodium silicate.

[0016] In the present application, in step (1), the active agent is at least one of polyvinyl alcohol (molecular weight 50000-150000), polyethylene glycol (molecular weight 2000-6000), methyl cellulose, and polyacrylamide (molecular weight 5-12 million).

[0017] In the present application, in step (1), preferably, the active agent comprises both polyvinyl alcohol (molecular weight 50000-15000) and polyethylene glycol (molecular weight 2000-6000), and further preferably, the mass ratio of polyvinyl alcohol to polyethylene glycol is 1.0:0.5-1.5. In the present application, when both polyvinyl alcohol and polyethylene glycol are used as the active agent, they have a synergistic effect on improving the selectivity of α-phenylethanol.

[0018] In the present application, in solution I, the mass concentration of each substance is 10%-20% for the nickel-containing salt, 20%-45% for the aluminum-containing salt, and 1%-2% for the active agent, and in solution II, the mass concentration of each substance is 15%-25% for the sodium-containing salt and 1%-10% for the silicon-containing salt.

[0019] In the present application, in step (1), before use, solution I or solution II is preferably warmed to 40-50℃ and stirred uniformly.

[0020] In the present application, in step (2), an appropriate amount of bottom water is added to the reaction kettle, such as 1 / 10-1 / 5 of the effective volume of the kettle.

[0021] In the present application, in step (2), the pH value is adjusted to 7.0-10.0, preferably 8.0-10, and the temperature of the reaction kettle is controlled to 60-95℃.

[0022] In the present application, in step (2), sodium carbonate solution is used to adjust the pH value, and the mass concentration of the sodium carbonate solution is 10%-20%.

[0023] In the present application, in step (3), the co-current addition time of solution I and solution II is 1.5-2.5 h.

[0024] In the present application, in step (3), the flow rate is adjusted to maintain the pH value at 7.0-10.0, preferably 8.0-10. After the co-current addition is completed, the temperature of the aging reaction under stirring is 60-95℃, and the time is 1-3 hours.

[0025] In the present application, in step (4), the temperature of the beating is 60-95℃, and the time of each beating is 20-60 minutes.

[0026] In the present application, in step (4), the beating is preferably carried out for multiple times until the conductivity of the filtrate is <500ms / m.

[0027] In the present application, in step (4), the first drying is carried out at 100-120℃ for 5-8 hours, and the second drying is carried out at 100-120℃ for 5-8 hours; the conditions of the first drying and the second drying can be the same or different; the calcination is carried out at a temperature of 300-600℃, preferably 400-480℃, for 4-8h, preferably 4-6h.

[0028] In the present application, in step (4), the shaping is preferably extrusion shaping. An adhesive, such as silica adhesive, is preferably added during the extrusion shaping.

[0029] The second aspect of the present application provides a catalyst prepared by the above method, which comprises the following components: 60-80wt% of alumina, 1-15wt% of silicon oxide, and 10-39wt% of nickel (elemental basis), preferably 60-70wt% of alumina, 2-12wt% of silicon oxide, and 20-38wt% of nickel (elemental basis).

[0030] The third aspect of the present application provides the use of the catalyst prepared by the above method in the preparation of α-phenethyl alcohol by the hydrogenation of acetophenone.

[0031] In the present application, the use specifically refers to: adding the catalyst into a reactor, and introducing a solution of acetophenone and hydrogen gas, wherein the reaction temperature is 40-120℃, the reaction pressure is 2-6MPa, the hydrogen gas volume space velocity is 100-2000h -1 , and the reaction liquid volume space velocity is 1-20h -1 . Preferably, the reaction temperature is 60-90℃, the reaction pressure is 2-5MPa, and the reaction liquid volume space velocity is 2.5-10h -1 .

[0032] In the present application, the reactor is a fixed bed reactor. A thermocouple can be arranged in the center of the fixed bed reactor to display the bed temperature, and a program temperature controller is used to control the reaction temperature, the reaction pressure, and the reaction liquid space velocity. The catalyst is preferably loaded in the constant temperature section of the catalyst, and the catalyst is reduced by introducing a gas containing H2 at 300-500℃ for 3-8h before being cooled to the hydrogenation reaction temperature.

[0033] In the present application, the reaction raw materials are subjected to hydrogenation reaction in the presence of a solvent, and isopropyl alcohol is generally used as the solvent. The mass ratio of acetophenone to isopropyl alcohol is 1.5-2.5:8.

[0034] Compared with the prior art, the present application has the following advantages:

[0035] The catalyst preparation method is simple, and the raw materials are inexpensive. In the preparation of α-phenethyl alcohol from acetophenone by using the catalyst, the catalyst processing load can be greatly improved, the catalyst has high activity, and the selectivity of α-phenethyl alcohol is high. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be described in detail below in combination with examples, but the present application is not limited to the following examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0037] Example 1

[0038] Preparation of the catalyst:

[0039] (1) 150 g of nickel nitrate hexahydrate, 500 g of aluminum nitrate nonahydrate, 500 g of water, 10 g of polyvinyl alcohol (molecular weight 80000), and 5 g of polyethylene glycol (molecular weight 4000) are mixed to form solution I; 200 g of sodium carbonate, 50 g of sodium silicate pentahydrate, and 800 g of water are mixed to form solution II, and the temperature is raised to 45℃ and stirred for half an hour;

[0040] (2) 800 g of water is added to the reaction kettle and stirred, 20 wt% of sodium carbonate solution is added, the pH value is adjusted to 8.0, and the temperature of the reaction kettle is maintained at 85℃, and stabilized for 0.5 h;

[0041] (3) Solution I and solution II are added in parallel, the pH value is maintained at 8.0, the temperature is 85℃, and the parallel addition time is 2 h, and the stirring aging is maintained for 2 h;

[0042] (4) The filter cake is filtered and beaten for 3 times, the beating temperature is 80℃, the beating time is 30 minutes each time, the conductivity of the filtrate is measured each time, and finally the conductivity of the three washings is maintained to be less than 500 ms / m; the finally obtained filter cake is dried at 110℃ for 8 hours, and crushed to a powder of >100 mesh; 10 g of silica gel containing 30 wt% of silicon oxide is used to perform extrusion molding with the crushed particles, to obtain a strip-shaped catalyst, which is dried at 110℃ for 8 hours, and the dried catalyst is calcined in a muffle furnace at 450℃ for 4 hours, to obtain catalyst A. Catalyst A contains, based on weight: 61 wt% of aluminum oxide, 9 wt% of silicon oxide, and 30 wt% of nickel (as an element).

[0043] Application of the catalyst:

[0044] The catalyst A prepared above was used for the hydrogenation of acetophenone to α-phenethyl alcohol. The stainless steel tubular reactor was charged with 2 mL of catalyst (20-40 mesh).

[0045] The reduction was carried out at 0.3 MPa pressure using H2 and N2 mixed gas (95 v% H2 and 5 v% N2) with a volume flow ratio of 100 mL / min; the temperature was programmed to 400°C and the reduction was carried out for 8 h at this temperature, after which the temperature was naturally lowered and the reduction process was completed; after the device was evacuated, H2 was switched on and the hydrogen flow was 50 mL / min, the reaction pressure was raised to 5 MPa, and a solution of acetophenone and isopropanol (the mass ratio of acetophenone to isopropanol was 2:8) was introduced, and the liquid hourly space velocity was 2.5 h -1 , and the temperature was slowly raised to 70°C; under this condition, the hydrogenation of acetophenone to α-phenethyl alcohol was carried out, the catalyst was evaluated, and the results obtained by analyzing the reaction condensate using a gas chromatograph are shown in Table 1.

[0046] Example 2

[0047] Preparation of the catalyst:

[0048] Compared with Example 1, the main difference is that in step (1) when the solution I is prepared, 100 g of nickel nitrate hexahydrate is added, and the other steps are the same as in Example 1. Catalyst B is obtained.

[0049] Catalyst B contains, on a weight basis: 68 wt% of alumina, 12 wt% of silicon oxide, and 20 wt% of nickel as an element.

[0050] The application conditions of the catalyst are the same as in Example 1, and catalyst B is evaluated, and the results obtained by analyzing the reaction condensate using a gas chromatograph are shown in Table 1.

[0051] Example 3

[0052] Preparation of the catalyst:

[0053] Compared with Example 1, the only difference is that in step (4) the dried catalyst is calcined in a muffle furnace at 400°C for 4 hours to obtain catalyst C, which contains, on a weight basis: 61 wt% of alumina, 9 wt% of silicon oxide, and 30 wt% of nickel.

[0054] The application conditions of the catalyst are the same as in Example 1, and catalyst C is evaluated, and the results obtained by analyzing the reaction condensate using a gas chromatograph are shown in Table 1.

[0055] Example 4

[0056] Preparation of the catalyst:

[0057] Compared with Example 1, the main difference lies in step (1): when preparing solution I, 15 g of polyvinyl alcohol (molecular weight 80,000) was added, and polyethylene glycol was not added. The other steps were the same as Example 1. Catalyst D was obtained.

[0058] Catalyst D comprises, on a weight basis, 61 wt % of aluminum oxide, 9 wt % of silicon oxide, and 30 wt % of nickel as an element.

[0059] The catalyst application conditions were the same as in Example 1. Catalyst D was evaluated and the results of gas chromatography analysis of the reaction condensate were shown in Table 1.

[0060] Example 5

[0061] Preparation of catalyst:

[0062] Compared with Example 1, the main difference lies in step (1): when preparing solution I, 15 g of polyethylene glycol (molecular weight 4000) is added, and polyvinyl alcohol is not added. The other steps are the same as Example 1. Catalyst E is obtained.

[0063] Catalyst E comprises, on a weight basis, 61 wt % of aluminum oxide, 9 wt % of silicon oxide, and 30 wt % of nickel as an element.

[0064] The catalyst application conditions were the same as in Example 1. Catalyst E was evaluated and the results of gas chromatography analysis of the reaction condensate were shown in Table 1.

[0065] Example 6

[0066] The catalyst was the same as that obtained in Example 1, except that the reaction temperature was lowered from 70°C to 60°C. Other application conditions were the same as in Example 1. Catalyst A was evaluated, and the results of gas chromatography analysis of the reaction condensate were shown in Table 1.

[0067] Example 7

[0068] The catalyst was the same as that obtained in Example 1, except that the reaction temperature was increased from 70°C to 80°C. Other application conditions were the same as in Example 1. Catalyst A was evaluated, and the results of gas chromatography analysis of the reaction condensate were shown in Table 1.

[0069] Example 8

[0070] The catalyst is the same as that obtained in Example 1, except that the volumetric space velocity of the reaction liquid is increased from 2.5 h -1 Increased to 5.0h -1 The other application conditions were the same as those in Example 1. Catalyst A was evaluated and the results of the reaction condensate analysis by gas chromatography are shown in Table 1.

[0071] Example 9

[0072] The same as the catalyst obtained in Example 1, except that the reaction pressure was changed from 5.0 MPa to 4.0 MPa when the catalyst was used. The other conditions were the same as in Example 1, and catalyst A was evaluated. The results obtained by analyzing the reaction condensate with a gas chromatograph are shown in Table 1.

[0073] Example 10

[0074] Preparation of the catalyst:

[0075] The main difference compared with Example 1 is in step (1): when solution I is prepared, 150 g of nickel nitrate hexahydrate, 500 g of aluminum nitrate nonahydrate, 500 g of water, 6 g of polyvinyl alcohol (molecular weight 80,000), and 9 g of polyethylene glycol (molecular weight 4,000) are added. The other steps are the same as in Example 1. Catalyst F is obtained.

[0076] Catalyst F contains, by weight: 61 wt% of alumina, 9 wt% of silica, and 30 wt% of nickel as an element.

[0077] The application conditions of the catalyst are the same as in Example 1, and catalyst F is evaluated. The results obtained by analyzing the reaction condensate with a gas chromatograph are shown in Table 1.

[0078] Comparative Example 1

[0079] The main difference compared with Example 1 is in step (1): 150 g of nickel nitrate hexahydrate, 500 g of aluminum nitrate nonahydrate, and 500 g of water are mixed to form solution I; 200 g of sodium carbonate, 50 g of sodium silicate pentahydrate, and 800 g of water are mixed to form solution II, which is heated to 45°C and stirred for half an hour.

[0080] The other steps are the same as in Example 1, and catalyst G is obtained. Catalyst G contains, by weight: 61 wt% of alumina, 9 wt% of silica, and 30 wt% of nickel as an element.

[0081] The application conditions of the catalyst are the same as in Example 1, and catalyst G is evaluated. The results obtained by analyzing the reaction condensate with a gas chromatograph are shown in Table 1.

[0082] Comparative Example 2

[0083] The main difference compared with Example 1 is in step (1): 114 g of copper nitrate hexahydrate, 500 g of aluminum nitrate nonahydrate, 500 g of water, 10 g of polyvinyl alcohol (molecular weight 80,000), and 5 g of polyethylene glycol (molecular weight 4,000) are mixed to form solution I; 200 g of sodium carbonate, 50 g of sodium silicate pentahydrate, and 800 g of water are mixed to form solution II, which is heated to 45°C and stirred for half an hour.

[0084] Other operation steps are the same as those in Example 1 to obtain catalyst H. Catalyst H comprises 61 wt% of alumina, 9 wt% of silica and 30 wt% of copper as element.

[0085] The application conditions of the catalyst are the same as those in Example 1. Catalyst H is evaluated. The results obtained by analyzing the reaction condensate by using a gas chromatograph are shown in Table 1.

[0086] Evaluation results of each catalyst in Table 1

[0087] acetophenone conversion / % alpha-phenylethanol selectivity / % Example 1 96.73 97.62 Example 2 95.76 95.45 Example 3 98.83 94.93 Example 4 96.02 88.38 Example 5 95.40 89.90 Example 6 93.26 99.21 Example 7 98.68 94.96 Example 8 92.23 96.65 Example 9 94.85 94.81 Example 10 95.34 92.53 Comparative Example 1 99.32 75.32 Comparative Example 2 73.68 84.72

[0088] The above describes the specific embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as the disclosed content of the present application and belong to the protection scope of the present application.

Claims

1. A method for preparing a catalyst for hydrogenating acetophenone to produce α-phenylethanol, the method comprising: The following steps are involved: (1) preparing a solution I comprising a nickel-containing salt, an aluminum-containing salt, an active agent, and water, and a solution II comprising a sodium-containing salt, a silicon-containing salt, and water; (2) Add bottom water to the reactor, adjust the pH, and control the reactor temperature; (3) Add solution I and solution II in parallel, adjust the flow rate to maintain the pH value, and after the parallel flow is completed, perform aging reaction under stirring; (4) After the reaction is completed, the slurry is filtered and beaten, and the filter cake is first dried, crushed, and formed, and then second dried and calcined to obtain the catalyst; In step (1), the active agent is at least one of polyvinyl alcohol with a molecular weight of 50,000 to 150,000 and polyethylene glycol with a molecular weight of 2,000 to 6,000.

2. The preparation method according to claim 1, wherein: In step (1), the nickel-containing salt is at least one of nickel nitrate and nickel sulfate, the aluminum-containing salt is at least one of aluminum nitrate and aluminum sulfate, the sodium-containing salt is at least one of sodium carbonate and sodium bicarbonate, and the silicon-containing salt is at least one of sodium silicate and potassium silicate.

3. The preparation method according to claim 2, wherein: In step (1), the nickel-containing salt is nickel nitrate; the aluminum-containing salt is aluminum nitrate; the sodium-containing salt is sodium carbonate; and the silicon-containing salt is sodium silicate.

4. The preparation method according to claim 1, wherein: In step (1), the active agent includes both polyvinyl alcohol and polyethylene glycol.

5. The preparation method according to claim 4, characterized in that: The mass ratio of polyvinyl alcohol to polyethylene glycol is 1.0:0.5~1.

5.

6. The preparation method according to claim 1, wherein: In the solution I, the mass concentration of each substance is: nickel-containing salt 10%-20%, aluminum-containing salt 20%-45%, active agent 1%-2%. In the solution II, the mass concentration of each substance is: sodium-containing salt 15%-25%, silicon-containing salt 1%-10%.

7. The preparation method according to claim 1, wherein: In step (1), the solution I or solution II is heated to 40-50° C. and stirred evenly before use.

8. The preparation method according to claim 1, wherein: In step (2), the pH value is adjusted to 7.0-10.0, and the temperature of the reactor is controlled to 60-95°C.

9. The preparation method according to claim 1, wherein: In step (2), the pH value is adjusted to 8.0-10.

0.

10. The preparation method according to claim 1, characterized in that: In step (3), the time for adding solution I and solution II in parallel is 1.5-2.5 hours; and / or, the flow rate is adjusted to maintain the pH value at 7.0-10.

0. After the parallel flow is completed, the aging reaction is carried out at a temperature of 60-95°C and a time of 1-3 hours under stirring.

11. The preparation method according to claim 10, characterized in that: In step (3), the flow rate is adjusted to maintain the pH value between 8.0 and 10.

0.

12. The preparation method according to claim 1, characterized in that: In step (4), the first drying condition is: drying at 100-120°C for 5-8 hours; the second drying condition is: drying at 100-120°C for 5-8 hours; the roasting condition is: roasting temperature is 300-600°C, and roasting time is 4-8 hours.

13. The preparation method according to claim 12, characterized in that: In step (4), the roasting conditions are: roasting temperature is 400~480℃; roasting time is 4~6h.

14. A catalyst prepared according to the preparation method according to any one of claims 1 to 13, characterized in that: The catalyst comprises the following components: based on the weight of the catalyst, aluminum oxide accounts for 60-80 wt%, silicon oxide accounts for 1-15 wt%, and nickel accounts for 10-39 wt% as an element.

15. The catalyst according to claim 13, characterized in that The catalyst comprises the following components: based on the weight of the catalyst, aluminum oxide accounts for 60-70 wt%, silicon oxide accounts for 2-12 wt%, and nickel accounts for 20-38 wt% as an element.

16. Use of the catalyst prepared by the preparation method according to any one of claims 1 to 13 or the catalyst according to any one of claims 14 to 15 in the preparation of α-phenylethanol by hydrogenation of acetophenone.