JP7594082B2 - Method for preparing copper-based hydrogenation catalyst, catalyst prepared therefrom and use thereof - Google Patents

Description

This application belongs to the technical field of catalytic hydrogenation, and specifically relates to a catalyst for hydrogenating acetophenone in liquid phase to prepare α-phenylethyl alcohol, as well as a method for preparing the catalyst and its use.

α-Phenylethyl alcohol is an important chemical intermediate and is widely used in industries such as medicine, fragrance manufacturing, cosmetics, food, and fine chemicals. Current methods for synthesizing α-phenylethyl alcohol mainly include microbial fermentation and acetophenone reduction/catalytic hydrogenation.

Microbial fermentation generally uses phenylalanine or fluorophenylalanine as raw materials to prepare α-phenylethyl alcohol by microbial fermentation conversion. The raw materials used in microbial fermentation are expensive, and the production costs are high. Currently, the acetophenone hydrogenation method is usually used to industrially prepare α-phenylethyl alcohol, which has the advantages of low production costs, few by-products, high product yield, and high product purity, making it suitable for mass production of α-phenylethyl alcohol.

Acetophenone hydrogenation catalysts mainly include platinum-palladium precious metal catalysts, nickel catalysts and copper catalysts. Precious metal catalysts and nickel catalysts are expensive, prone to aromatic ring saturation and hydrogenolysis of phenylethyl alcohol, and have poor selectivity for α-phenylethyl alcohol. Compared with precious metal catalysts and nickel catalysts, copper catalysts have the advantages of high activity, selectivity and low cost when used in the hydrogenation reaction of acetophenone, but they still have problems such as low catalytic strength, poor stability, easy loss of active components, and easy hydrogenolysis/dehydration side reactions (hydrogenolysis/dehydration side reactions of α-phenylethyl alcohol occur during the hydrogenation of acetophenone, which is prone to generating ethylbenzene/styrene, and the hydrogenolysis and dehydration reaction rates both increase rapidly with increasing reaction temperature).

In Patent Document 1, Ni-Sn-B/ _SiO2 catalyst is prepared by the immersion method, calcined at a low temperature, and then reduced using _KBH4 as a reducing agent. During the catalytic reaction, the maximum selectivity of phenylethyl alcohol reaches 97.5%, but the interaction between the active component Ni and the support _SiO2 is weak and is easily washed away.

Patent Document 2 discloses a Pd-C catalyst, but the catalyst has poor stability and requires constant increase in reaction temperature during application.

Patent Document 3 discloses a reduced copper catalyst and a method for preparing α-phenylethyl alcohol using the catalyst, but the method requires a liquid-phase reduction method to improve the stability of the catalyst, which makes the process complicated and expensive.

Patent Document 4 discloses a method for preparing α-phenylethyl alcohol using Raney nickel as a catalyst, but the hydrogenation product of acetophenone in this method contains a large amount of α-cyclohexylethanol, an aromatic ring hydrogenation product, and the selectivity for α-phenylethyl alcohol is low.

Therefore, it is of great significance to solve problems in the prior art, such as the low bonding strength between the catalytic active components and the support, the deactivation of the catalyst due to the loss of the active components, and the uneven dispersion of the active components, to improve the low-temperature activity of the copper-based hydrogenation catalyst, to improve the dispersion of copper in the catalyst, to reduce the loss of the active components, to improve the strength of the catalyst, to suppress the production of by-products, and to prepare a highly active and highly selective acetophenone hydrogenation catalyst.

Chinese Patent Publication No. 1557545 U.S. Pat. No. 4,996,374 Chinese Patent Publication No. 1315226 China Patent Publication No. 1911883

The following is a summary of the subject matter described in detail in the text. This summary is not intended to limit the scope of protection of the claims.

The purpose of this application is to solve the above problems in the conventional technology and to provide a method for preparing a copper-based catalyst for hydrogenating acetophenone in a liquid phase to prepare α-phenylethyl alcohol, and the prepared catalyst.

The copper catalyst of the present application is prepared by an ion exchange method using activated carbon as a carrier and metallic lithium as an auxiliary. The obtained catalyst has excellent skeletal strength and pore size distribution, and good mass and heat transfer effects, while at the same time having the advantages of high activity, high dispersion of active components, high sintering resistance, and low loss of active components.

When the catalyst described in this application is used to prepare α-phenylethyl alcohol by hydrogenating acetophenone in liquid phase, the catalyst has better low-temperature activity and can significantly reduce the production of by-products. In particular, by using the catalyst in combination with the auxiliary lithium element, Cu-Li, added to the components, the alkalinity of the catalyst can be improved, and hydrogenolysis/dehydration side reactions can be effectively suppressed, while also having advantages such as long-term stability.

In one aspect of the present application to achieve the above object, the following technical solution is adopted.
The method for preparing the catalyst is as follows:
(1) a step of immersing activated carbon in an acid solution, followed by separation and washing;
Step (2) of immersing the activated carbon treated in step (1) in an alkaline solution, followed by separation, washing and drying;
The activated carbon treated in step (2) is immersed in an ethanol-water mixed solution containing a copper salt and a lithium salt for aging, and then separated, washed, dried and calcined to obtain a copper-based hydrogenation catalyst (3).

In step (1) of the preparation method of the present application, the acid solution is an aqueous solution of acid, the concentration of which is 0.5-2 mol/L, preferably 0.8-1.5 mol/L, and the acid is one or more selected from nitric acid, hydrochloric acid, and sulfuric acid, preferably nitric acid. A low acid concentration directly affects the number of groups on the support surface. In addition, the acid solution can also remove impurities present on the support itself, so a low acid concentration will leave impurities behind, affecting the activity and selectivity of the catalyst. Conversely, a high acid concentration will destroy the support and affect its service life.

In step (1) of the preparation method of the present application, the activated carbon is either coconut shell charcoal or wood charcoal, and has an iodine value of 600-1500, preferably 800-1300, and a particle size of 4-60 mesh, preferably 8-16 mesh. The iodine value of the activated carbon is determined through experiments. A reasonable iodine value range in the present application is advantageous for promoting the progress of the hydrogenation reaction, but is disadvantageous to the reaction performance and physical performance of the catalyst.

In step (1) of the preparation method of the present application, the conditions for the immersion treatment are atmospheric pressure overdose immersion, the immersion temperature is 80-140°C, preferably 90-130°C, and the immersion time is 2-8 hours, preferably 3-6 hours. In the immersion treatment process, this step has no specific requirements for the amount of acid solution used, as long as the activated carbon carrier is completely immersed. The immersion temperature mainly promotes the formation of organic functional groups on the carrier surface, and a low or high temperature is disadvantageous.

In step (1) of the preparation method of the present application, the subsequent separation and washing after the immersion treatment can be performed by normal operating methods, and there are no specific requirements. In some examples, the separation can be performed by centrifugation, and the washing can be performed by water washing. The immersion treatment of the activated carbon carrier with an acid solution in step (1) can remove impurities from the activated carbon, while the purpose is to modify the oxygen-containing functional groups on the surface of the activated carbon. The activated carbon itself is an inert material with few surface functional groups. After high-temperature oxidation treatment in the acid solution, the oxygen-containing groups, such as functional groups such as -COOH, are increased on the surface of the activated carbon, and the modified surface is ready for the next modification.

In step (2) of the preparation method of the present application, the alkaline liquid is an alkaline water solvent containing an ammonium salt, the concentration of which is 2 to 10 wt %, preferably 3 to 8 wt %, and the ammonium salt is selected from ammonium carbonate and/or ammonium hydrogen carbonate.

In step (2) of the preparation method of the present application, the immersion treatment is carried out under normal pressure overdose conditions, the temperature is 20-60°C, preferably 30-50°C, and the immersion time is 2-8h, preferably 3-6h. In the immersion treatment process, the amount of alkaline solution used in this step is not specifically required as long as the activated carbon carrier is completely immersed, but it is necessary to ensure that the solution has a sufficient content of ions to exchange the functional groups generated by the acid-treated carrier in step (1). In step (2), the surface of the activated carbon carrier is modified using ammonium salt, and the oxygen-containing functional groups modified in the first step are replaced using NH4 ⁺ ions, for example, -COOH is converted to _-COONH4 , and the purpose of the modification is to prepare for the next copper ion exchange, otherwise it is disadvantageous to the exchange reaction of copper ions.

In step (2) of the preparation method of the present application, the drying temperature is 90-150°C, preferably 100-130°C, and the drying time is 2-8h, preferably 3-6h. The separation and washing in this step are performed by normal operating methods, and there are no specific requirements. In some examples, the separation can be performed by centrifugation, and the washing can be performed by water washing.

In step (3) of the preparation method of the present application, the ethanol water mixed solution containing the copper salt and the lithium salt has a copper salt concentration of 10-45 wt %, preferably 15-30 wt %, a lithium salt concentration of 10-40 wt %, preferably 20-30 wt %, and an ethanol concentration of 2-8 wt %, preferably 3-6 wt %, based on the total weight of the mixed solution;
Preferably, the copper salt is one or more of copper nitrate, copper chloride or copper acetate;
Preferably, the lithium salt is one or both of lithium nitrate or lithium chloride.

In step (3) of the preparation method of the present application, the immersion and aging process is preferably equal volume immersion and aging under normal pressure conditions, at a temperature of 20 to 60°C, preferably 30 to 50°C, for a time of 2 to 8 hours, preferably 3 to 6 hours.

In step (3) of the preparation method of the present application, the drying is performed at a temperature of 90 to 150° C., preferably 100 to 130° C., for a time of 2 to 8 h, preferably 3 to 6 h;
The firing temperature is 300 to 600° C., preferably 400 to 500° C., and the firing time is 2 to 8 hours, preferably 3 to 6 hours.

The separation and washing described in this step are performed by normal operating methods, and there are no specific requirements. In some examples, the separation can be performed by filtration, and the washing can be performed by water washing.

The preparation method of the present application controls the pretreatment step for the carrier, combines with an ion exchange method, and supports the active ingredient using a chemical bonding method, making it difficult for the ingredient to be washed away. As a result, the prepared catalyst has stronger bonding strength between the active ingredient and the carrier and is more stable than the catalyst prepared by the conventional impregnation method.

In the present application, the copper-based hydrogenation catalyst prepared by the above method has a composition of 3 to 10 wt %, preferably 5 to 8 wt %, copper oxide, 0.3 to 3 wt %, preferably 0.5 to 2 wt %, lithium oxide, and the remainder is activated carbon, based on the total weight of the catalyst, to obtain a supported hydrogenation catalyst, with the active component showing an eggshell-type distribution.

In another aspect, the present application further provides the use of the copper-based hydrogenation catalyst in the preparation of α-phenylethyl alcohol by liquid phase hydrogenation of acetophenone.

The method for hydrogenating acetophenone to prepare α-phenylethyl alcohol involves preparing α-phenylethyl alcohol by an acetophenone hydrogenation reaction under the action of the above-mentioned copper-based hydrogenation catalyst.

Preferably, the conditions of the hydrogenation reaction are a reaction pressure of 2-5 MPa (gauge pressure), preferably 2.5-4 MPa (gauge pressure), a reaction temperature of 60-100° C., preferably 70-90° C., a H ₂ /HPA (acetophenone) molar ratio of 2-20:1, preferably 5-15:1, and a catalyst usage of 0.2-0.6 g HPA·gcat ⁻¹ ·h ⁻¹ , preferably 0.3-0.5 g HPA·gcat ⁻¹ ·h ⁻¹ .

Preferably, the hydrogenation feedstock further contains a solvent, the solvent is ethylbenzene, and the concentration of acetophenone in the solvent is 10 to 15 wt %.

Those skilled in the art should understand that the catalyst has a corresponding catalytic activity after reductive activation, and preferably the reduced copper-based hydrogenation catalyst is used for the preparation of α-phenylethyl alcohol by hydrogenation of acetophenone.

The reduction activation of the hydrogenation catalyst is a common operation in the field. In a preferred embodiment, the reduction activation method of the catalyst described in the present application includes: maintaining the volumetric space velocity of the hydrogen and nitrogen mixed gas at 300-1000h ^- ₁ ; preferably, first, increasing the reactor temperature to 160-180°C, and desorbing the physical water adsorbed on the catalyst at a constant temperature for 1-2 hours; then, introducing the hydrogen and nitrogen mixed gas with a volume fraction of 10v% H2 or less, for example (5v%±2v%) _H2, to pre-reduce the catalyst for at least 0.5 hours, for example, 1 hour, 1.5 hours or 2 hours; then, gradually increasing the hydrogen ratio in the hydrogen and nitrogen mixed gas, for example, to 10v%, 20v%, 50v%, 100v%, and controlling the hot spot temperature of the catalyst bed layer in this process to be 220°C or less; and finally, increasing the temperature to 200-220°C and reducing under a pure hydrogen atmosphere for 2-5 hours, for example, 3 or 4 hours, to obtain an activated catalyst.

Compared with the prior art, the beneficial effects of the technical solution of the present application are as follows:
In the present application, activated carbon is used as a catalyst carrier, and copper-lithium bimetallic acts synergistically. The catalyst is prepared by ion exchange, which improves the dispersion of active components, and not only has high catalytic activity, but also has good low-temperature activity compared with conventional copper-based catalysts, and the active components are not easily washed away, improving the long-term stability of the catalyst and improving the sintering resistance of the catalyst. In addition, the catalyst adopts a carrier such as coconut shell charcoal, which has excellent skeletal strength and pore size distribution, which is favorable for the diffusion of reactants and has good mass transfer and heat transfer effects. When the catalyst is used in the preparation of α-phenylethyl alcohol by hydrogenating acetophenone, it can effectively improve the hydrogenation ability of the catalyst and inhibit side reactions such as dehydration of phenylethyl alcohol, and has the advantages of high activity and high selectivity.

Other aspects can be understood after reading and understanding the detailed description.

The method of the present application will be described in detail below with reference to examples, but is not limited to these examples.

1. Main raw materials in the examples and comparative examples Coconut shell charcoal has a particle size of 8-16 mesh, an iodine value of 800-1300, and a pore volume of 0.38 cm ³ /g. It was purchased from Woody Forest Co., Ltd.
The alumina support has a particle size of 8-30 mesh, a specific surface area of 274 m ² /g, and a pore volume of 0.86 cm ³ /g, and was purchased from Shandong Aluminum Industry;
Unless otherwise specified, all other raw materials are common commercial products, and all reagents are analytical reagents.

II. Analytical Methods for Products in Examples and Comparative Examples The element contents in the catalysts were measured using an X-ray fluorescence spectrum analyzer (XRF).
The copper ions in the hydrogenated liquid were measured using an inductively coupled plasma emission mass spectrometer (ICP).
The catalyst side pressure strength was measured using a D-III type strength measuring instrument for 50 samples, and the average value was calculated.

The moles of acetophenone contained in the raw material, the moles of phenylethyl alcohol produced, and the moles of ethylbenzene and styrene produced by side reactions were analyzed using an Agilent 7820A gas chromatograph and then calculated. The measurement conditions included using a DB-5 column and an FID detector, a vaporizer temperature of 260°C, a detector temperature of 260°C, a carrier gas of high purity _N2 , and a flow rate of 30 ml/min.

Acetophenone conversion rate=(1-number of moles of acetophenone remaining in the reaction solution/number of moles of acetophenone contained in the raw material)*100%,
Selectivity of phenylethyl alcohol=moles of phenylethyl alcohol produced/moles of acetophenone converted*100%;
The calculation method for the selectivity of ethylbenzene and styrene is the same as that for the selectivity of phenylethyl alcohol.

Example 1
Preparation of copper-based hydrogenation catalyst: (1) 50 ml of an aqueous solution of nitric acid with a concentration of 1 mol/L was prepared, 15 g of activated carbon was added to the aqueous solution of nitric acid, and the solution was heated to 90° C. and immersed in excess at a constant temperature for 4 hours, followed by centrifugation and washing with water.

(2) 50 g of an aqueous solution of ammonium carbonate with a concentration of 5 wt % was prepared, and the activated carbon treated in step (1) was added to the aqueous solution of ammonium carbonate and soaked in excess at room temperature of 25°C for 4 hours, then centrifuged, washed with water, and dried at 100°C for 4 hours.

(3) 9.13 g of a mixed solution of copper nitrate and lithium nitrate in ethanol and water was prepared, and the total weight of the mixed solution was 11.6 wt% copper nitrate, 22.7 wt% lithium nitrate, and 5 wt% ethanol. The activated carbon treated in step (2) was then added, and the mixture was aged by soaking in an equal volume at room temperature of 25°C for 4 hours, dried at 100°C for 4 hours, and then calcined at 400°C for 4 hours to obtain catalyst A with a copper oxide content of 3 wt% and a lithium oxide content of 3 wt%.

Example 2
Regarding the preparation of copper-based hydrogenation catalyst: (1) 50 ml of an aqueous hydrochloric acid solution having a concentration of 1.5 mol/L was prepared, and 15 g of activated carbon was added to the aqueous hydrochloric acid solution. The solution was heated to 90° C. and immersed in excess at a constant temperature for 4 hours, followed by centrifugation and washing with water.

(2) 50 g of an aqueous solution of ammonium bicarbonate with a concentration of 8 wt % was prepared, and the activated carbon treated in step (1) was added to the aqueous solution of ammonium bicarbonate, and the mixture was soaked in excess at room temperature of 25°C for 4 hours, then centrifuged, washed with water, and dried at 90°C for 5 hours.

(3) 7.4 g of a mixed solution of copper nitrate and lithium nitrate in ethanol and water was prepared, and the total weight of the mixed solution was 14.3 wt% copper nitrate, 4.7 wt% lithium nitrate, and 5 wt% ethanol. The activated carbon treated in step (2) was then added, and aged by immersing in an equal volume at room temperature of 25°C for 4 hours, then dried at 100°C for 4 hours, and calcined at 450°C for 4 hours to obtain catalyst B with a copper oxide content of 3 wt% and a lithium oxide content of 0.5 wt%.

Example 3
Preparation of copper-based hydrogenation catalyst: (1) 50 ml of an aqueous sulfuric acid solution with a concentration of 0.5 mol/L was prepared, 15 g of activated carbon was added to the aqueous sulfuric acid solution, and the solution was heated to 90° C. and immersed in excess at a constant temperature for 4 hours, followed by centrifugation and washing.

(2) 50 g of an aqueous solution of ammonium carbonate with a concentration of 5 wt % was prepared, and the activated carbon treated in step (1) was added to the ammonium carbonate solution and soaked in excess at room temperature of 45°C for 4 hours, then centrifuged, washed with water, and dried at 90°C for 5 hours.

(3) 10.6 g of a mixed solution of copper nitrate and lithium nitrate in ethanol and water was prepared, and the total weight of the mixed solution was 33.4 wt% copper nitrate, 9.8 wt% lithium nitrate, and 5 wt% ethanol. The activated carbon treated in step (2) was then added, and aged by immersing in an equal volume at room temperature of 30°C for 4 hours, followed by drying at 100°C for 4 hours and calcining at 400°C for 4 hours to obtain catalyst C with a copper oxide content of 10 wt% and a lithium oxide content of 1.5 wt%.

Example 4
Preparation of copper-based hydrogenation catalyst: (1) 50 ml of an aqueous solution of nitric acid with a concentration of 2 mol/L was prepared, 15 g of activated carbon was added to the aqueous solution of nitric acid, and the solution was heated to 80° C. and immersed in excess at a constant temperature for 4 hours, followed by centrifugation and washing.

(2) 50 g of an aqueous solution of ammonium carbonate with a concentration of 10 wt % was prepared, and the activated carbon treated in step (1) was added to the ammonium carbonate solution and soaked in excess at room temperature of 20°C for 4 hours, then centrifuged, washed with water, and dried at 90°C for 5 hours.

(3) 10.6 g of a mixed solution of copper nitrate and lithium nitrate in ethanol and water was prepared, and the total weight of the mixed solution was 33.4 wt% copper nitrate, 9.8 wt% lithium nitrate, and 5 wt% ethanol. The activated carbon treated in step (2) was then added, and aged by soaking in an equal volume at room temperature of 30°C for 4 hours, followed by drying at 100°C for 4 hours and calcining at 400°C for 4 hours to obtain catalyst D with a copper oxide content of 10 wt% and a lithium oxide content of 1.5 wt%.

Example 5
Preparation of copper-based hydrogenation catalyst: (1) 50 ml of an aqueous solution of nitric acid with a concentration of 2 mol/L was prepared, 15 g of activated carbon was added to the aqueous solution of nitric acid, and the solution was heated to 80° C. and immersed in excess at a constant temperature for 4 hours, followed by centrifugation and washing.

(2) 50 g of an aqueous solution of ammonium carbonate with a concentration of 10 wt % was prepared, and the activated carbon treated in step (1) was added to the ammonium carbonate solution and soaked in excess at room temperature of 20°C for 4 hours, then centrifuged, washed with water, and dried at 90°C for 5 hours.

(3) 9.1 g of a mixed solution of copper nitrate and lithium nitrate in ethanol and water was prepared, and the total weight of the mixed solution was 31.3 wt% copper nitrate, 2.3 wt% lithium nitrate, and 2 wt% ethanol. The activated carbon treated in step (2) was then added, and aged by immersing in an equal volume at room temperature of 30°C for 4 hours, followed by drying at 100°C for 4 hours and calcining at 400°C for 4 hours to obtain catalyst E with a copper oxide content of 8 wt% and a lithium oxide content of 0.3 wt%.

Comparative Example 1
With reference to the preparation method of Example 1, the only difference was that the alkaline solution immersion treatment in step (2) was not carried out, and catalyst F with a copper content of 3 wt % and a lithium oxide content of 3 wt % was obtained.

Comparative Example 2
With reference to the preparation method of Example 2, the only difference was that the acid immersion treatment in step (1) was not carried out, and catalyst G was obtained, which had a copper oxide content of 3 wt % and a lithium oxide content of 0.5 wt %.

Comparative Example 3
Referring to the preparation method of Example 1, the only difference is that lithium nitrate is not added in step (3), and catalyst H with a copper oxide content of 3 wt % is obtained.

Comparative Example 4
Referring to the preparation method of Example 2, the only difference was that lithium nitrate was replaced with 0.43 g of sodium nitrate in step (3), to obtain catalyst I with a copper oxide content of 3 wt % and a sodium oxide content of 0.5 wt %.

Comparative Example 5
Referring to the preparation method of Example 2, the only difference was that in step (3), activated carbon was replaced with an equal mass of alumina carrier, and catalyst J was obtained with a copper oxide content of 3 wt % and a lithium oxide content of 0.5 wt %.

Comparative Example 6
With reference to the preparation method of Example 1, the only difference is that the order of steps (1) and (2) is exchanged, and the alkaline solution immersion treatment of step (2) is carried out before the acid solution immersion treatment of step (1), thereby obtaining catalyst K having a copper oxide content of 3 wt % and a lithium oxide content of 3 wt %.

Comparative Example 7
8.07 g of a mixed solution of copper nitrate and lithium nitrate in ethanol and water was prepared. The total weight of the mixed solution was 13.4 wt % copper nitrate, 25.7 wt % lithium nitrate, and 3.7 wt % ethanol. Untreated activated carbon was added to the above solution, aged by immersing in an equal volume at room temperature of 25° C. for 4 hours, dried at 100° C. for 4 hours, and calcined at 400° C. for 4 hours, to obtain catalyst L having a copper oxide content of 3 wt % and a lithium oxide content of 3 wt %.

Catalyst Use Examples The copper-based hydrogenation catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 7 were respectively used in the preparation of α-phenylethyl alcohol by hydrogenation of acetophenone, and the steps are as follows:
Catalyst reduction: The catalyst is placed in a fixed bed hydrogenation reactor, and the catalyst loading is 20ml. Before using the catalyst, it is reduced under a mixed gas of nitrogen and hydrogen, and the mixed gas volumetric space velocity is kept at 300h ^-1 during the reduction process. First, the temperature of the reactor is raised to 160°C, and the physical water adsorbed on the catalyst is desorbed at a constant temperature for 2 hours. Then, a mixed gas containing hydrogen and nitrogen with a volume fraction of 5v% _H2 is introduced to perform pre-reduction for 1 hour, and the hydrogen ratio in the mixed gas of hydrogen and nitrogen is increased stepwise to 10v%, 20v%, 50v%, and 100v%, and the hot spot temperature of the catalyst bed layer during this process is controlled to be below 220°C. Finally, the temperature is raised to 220°C and reduced under a pure hydrogen atmosphere for 3 hours.

The reaction was carried out using an ethylbenzene solution of acetophenone having a hydrogenation feed composition of 15 wt % under the conditions of a pressure of 2.5 MPa (gauge pressure), a temperature of 70° C., a H ₂ /HPA molar ratio of 5:1, and a catalyst throughput of 0.3 gHPA/gcat/h.

The hydrogenated liquid was sampled at 24-h intervals and the copper ion content in the hydrogenated liquid was measured. After 1,000 hours of reaction, the catalyst was removed from the reactor and sieved using a stainless steel classification sieve with a pore size of 2 mm. The proportion of catalyst particle mass with a particle size of <1 mm to the total catalyst mass was calculated, and this was taken as the catalyst breakage rate.

The catalytic performance, hydrogenation reaction results, and average copper ion content in the hydrogenation liquid are shown in Table 1.

From Table 1, it can be seen that when catalysts A to E, H, I and J were used, no copper was detected in the hydrogenation liquid, while ICP analysis of catalysts F, G, K and L showed high copper content in the hydrogenation liquid, which indicates that the catalyst was obviously washed away. In addition, catalysts A to E have high activity and can effectively suppress side reactions such as the production of ethylbenzene by hydrogenolysis and the production of styrene by dehydration, while the activity of the catalysts in Comparative Examples 1 to 7 is low. At the same time, after a long-term stable operation of 1000 hours, the acetophenone conversion rate of catalysts A to E exceeded 99%, and the selectivity of α-phenylethyl alcohol exceeded 99%.

Example 6
The copper hydrogenation catalyst B prepared in Example 2 was used to prepare α-phenylethyl alcohol by hydrogenation of acetophenone, and the reaction temperature was adjusted according to the method of Example 4. The hydrogenation results are shown in Table 2.

From Table 2, it can be seen that when the hydrogenation reaction temperature is between 60 and 100°C, a high acetophenone conversion rate can be obtained in all cases, and the acetophenone conversion rate increases as the temperature increases, but the selectivity of α-phenylethyl alcohol decreases. The optimal condition is 70 to 80°C, and the selectivity of α-phenylethyl alcohol is above 99% in all cases, which indicates that the catalyst has good low-temperature activity.

Claims (17)

A method for preparing a copper-based hydrogenation catalyst, comprising the steps of:
(1) a step of immersing activated carbon in an acid solution, followed by separation and washing;
Step (2) of immersing the activated carbon treated in step (1) in an alkaline solution, followed by separation, washing and drying;
and (3) adding the activated carbon treated in step (2) to an ethanol-water mixed solution containing a copper salt and a lithium salt, immersing the activated carbon in the mixed solution for aging, and then isolating, washing, drying and calcining the activated carbon to obtain a copper-based hydrogenation catalyst.
The alkaline liquid is an alkaline aqueous solution containing an ammonium salt,
The copper-based hydrogenation catalyst is used in the hydrogenation reaction of acetophenone. In step (1), the acid solution is an aqueous solution of an acid, and the concentration is 0.5 to 2 mol/L, and the acid is one or more selected from nitric acid, hydrochloric acid, and sulfuric acid;
The preparation method according to claim 1, wherein the activated carbon is either coconut shell charcoal or wood charcoal, and its iodine value is 600-1500, and its particle size is 4-60 mesh. In step (1), the concentration of the acid solution is 0.8 to 1.5 mol/L, and the acid is selected from nitric acid;
3. The preparation method according to claim 1 or 2, wherein the iodine value of the activated carbon is 800-1300, and the particle size of the activated carbon is 8-16 mesh. The method according to any one of claims 1 to 3, wherein in step (1), the immersion treatment is performed at a immersion temperature of 80 to 140°C for a period of 2 to 8 hours. The method according to any one of claims 1 to 4, wherein in step (1), the immersion treatment is performed at a immersion temperature of 90 to 130°C for a period of 3 to 6 hours. The preparation method according to any one of claims 1 to 5, wherein in step (2), the concentration of the alkaline solution is 2 to 10 wt %, and the ammonium salt is selected from ammonium carbonate and/or ammonium hydrogen carbonate. The preparation method according to any one of claims 1 to 6, wherein in step (2), the concentration of the alkaline solution is 3 to 8 wt %. The method according to any one of claims 1 to 7, wherein in step (2), the soaking treatment is carried out at a soaking temperature of 20 to 60°C for a soaking time of 2 to 8 hours. The method according to any one of claims 1 to 8, wherein in step (2), the soaking treatment is carried out at a soaking temperature of 30 to 50°C for a soaking time of 3 to 6 hours. In step (3), the ethanol water mixed solution containing the copper salt and the lithium salt has a copper salt concentration of 10-45 wt %, a lithium salt concentration of 10-40 wt %, and an ethanol concentration of 2-8 wt %, based on the total weight of the mixed solution;
the copper salt being one or more of copper nitrate, copper chloride, or copper acetate;
The preparation method according to any one of claims 1 to 9, wherein the lithium salt is one or both of lithium nitrate or lithium chloride. In step (3), the immersion and aging process is carried out at a temperature of 20 to 60° C. for 2 to 8 hours;
The drying is performed at a temperature of 90 to 150° C. for 2 to 8 hours.
The preparation method according to any one of claims 1 to 10, wherein the calcination is performed at a temperature of 300 to 600°C for a time of 2 to 8h. A copper-based hydrogenation catalyst, the composition of which, based on the total weight of the catalyst, is 3-10 wt % copper oxide, 0.3-3 wt % lithium oxide, and the remainder is activated carbon;
The copper-based hydrogenation catalyst is used in the hydrogenation reaction of acetophenone . The copper-based hydrogenation catalyst according to claim 12, wherein the copper oxide in the catalyst is 5 to 8 wt % based on the total weight of the catalyst. The copper-based hydrogenation catalyst according to claim 12 or 13, wherein the lithium oxide in the catalyst is 0.5 to 2 wt % based on the total weight of the catalyst. Use of a copper-based hydrogenation catalyst prepared by the preparation method according to any one of claims 1 to 11, or a copper-based hydrogenation catalyst according to any one of claims 12 to 14, in the preparation of α-phenylethyl alcohol by hydrogenation of acetophenone in liquid phase. A method for preparing α-phenylethyl alcohol by hydrogenating acetophenone, comprising: preparing α-phenylethyl alcohol by hydrogenation reaction of acetophenone under the action of a copper-based hydrogenation catalyst prepared by the preparation method according to any one of claims 1 to 11 or a copper-based hydrogenation catalyst according to any one of claims 12 to 14;
The hydrogenation reaction conditions are a reaction pressure of 2-5 MPa (gauge pressure), a reaction temperature of 60-100° C., a H ₂ /HPA molar ratio of 2-20:1, and a catalyst usage amount of 0.2-0.6 gHPA·gcat ⁻¹ ·h ⁻¹ . The reaction pressure is 2.5 to 4 MPa (gauge pressure).
The reaction temperature is 70 to 90° C.
the _H2 /HPA molar ratio is 5-15:1;
The catalyst usage amount is 0.3-0.5 g HPA·gcat ⁻¹ ·h ⁻¹ ,
17. The method according to claim 16, wherein the raw material for the hydrogenation reaction further comprises a solvent, the solvent being ethylbenzene, and the concentration of acetophenone in the solvent is 10 to 15 wt %.