Hydrogenation catalyst for preparing tetrahydrocurcumin as well as preparation method and application of hydrogenation catalyst

Abstract

The invention discloses a hydrogenation catalyst for preparing tetrahydrocurcumin as well as a preparation method and application of the hydrogenation catalyst. The catalyst contains an active component Pd and a carrier modified aluminum oxide. The invention also provides a method for continuously preparing tetrahydrocurcumin by using the hydrogenation catalyst, which comprises the following steps: carrying out hydrogenation reaction on a curcumin solution with a certain concentration and hydrogen in a fixed bed reactor under certain reaction conditions under the action of the catalyst to prepare a tetrahydrocurcumin hydrogenation solution; and desolventizing and recrystallizing the hydrogenation liquid to obtain the finished product tetrahydrocurcumin. According to the method provided by the invention, the hydrogenation catalyst has higher activity, and when the curcumin is hydrogenated to prepare tetrahydrocurcumin, the raw material conversion rate can reach 100%, and the product selectivity can reach 99% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemistry and relates to a hydrogenation catalyst for preparing tetrahydrocurcumin and a preparation method and application thereof. Background Art

[0002] Tetrahydrocurcuminoids (THC) is the main product of curcumin metabolism in the human body and is obtained by hydrogenation of curcumin. THC has good stability in aqueous solution and is more easily absorbed through the gastrointestinal tract than curcumin. Tetrahydrocurcumin and curcumin have basically the same effects. Compared with curcumin, tetrahydrocurcumin is more stable and has higher antioxidant properties, so it has higher bioavailability and is more widely used. Tetrahydrocurcumin has the effects of whitening and rejuvenating the skin, resisting skin aging, anti-wrinkle and anti-inflammatory. At present, the chemical synthesis method of tetrahydrocurcumin mainly uses curcumin as the raw material and hydrogenates tetrahydrocurcumin, with the focus on the catalyst. The reaction equation is as follows: Patent CN104496779A uses platinum-iron nickel hydroxide composite nanoparticle catalyst to prepare tetrahydrocurcumin. The purity of tetrahydrocurcumin is unknown, the product color is light yellow, and the raw material conversion rate is low. Patent CN114031488A uses palladium carbon catalyst and Raney nickel to prepare tetrahydrocurcumin, and the product selectivity is low. Patent CN117586111A uses nickel alumina catalyst and fixed bed reaction technology, and the product selectivity is low. The catalysts used in the above preparation processes do not have a clear metal content. Patent CN111018705A uses acetylation to prepare intermediates, and then catalytic hydrogenation of the intermediates, and then deacetylation to synthesize tetrahydrocurcumin. This preparation process uses a kettle reaction, with a long process flow and complicated operations.

[0003] In summary, the existing chemical synthesis of tetrahydrocurcumin has the problems of easy raw material residue and low product selectivity. At present, the selectivity of the disclosed products is generally lower than 98%. Therefore, it is necessary to develop a catalyst for curcumin hydrogenation with low production cost and high selectivity and a method for continuous hydrogenation synthesis of tetrahydrocurcumin. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a highly selective hydrogenation catalyst, which has low production cost and high catalytic activity. At the same time, a method for preparing tetrahydrocurcumin by continuous hydrogenation is provided, which overcomes the deficiencies of the prior art and provides a production route with convenient operation and high degree of automation.

[0005] According to a first aspect of the present invention, the present invention provides a hydrogenation catalyst, which comprises a modified carrier and an active component loaded on the modified carrier, wherein the active component is Pd, and the carrier is alkaline earth metal modified alumina.

[0006] According to the method of the present invention, the hydrogenation catalyst is based on the total amount, and its weight percentage is composed of: the weight content of the active component is 0.3-2.0%, and the balance is the carrier.

[0007] According to the method of the present invention, the alkaline earth metal in the hydrogenation catalyst is magnesium, calcium, strontium, barium, and radium, and the weight content of the alkaline earth metal is 0.5-3% based on the total amount of the carrier.

[0008] According to the method of the present invention, the catalyst is characterized in that: the catalyst specific surface area is 170-230m 2 / g, pore volume is 0.4-0.8cm 3 / g.

[0009] The present invention also provides a method for preparing a hydrogenation catalyst for preparing tetrahydrocurcumin, the method comprising the following steps: (1) forming a compound containing an alkaline earth metal element and a carrier and / or a carrier precursor, drying or not drying the resulting mixture, and then calcining the mixture to obtain an alkaline earth metal-modified alumina carrier; (2) contacting the modified alumina support with a solution containing a Pd compound at a certain temperature to obtain an impregnated support, and drying the impregnated support; (3) Activating the Pd-containing carrier under a reducing atmosphere to obtain the catalyst of the present invention.

[0010] According to the preparation method of the catalyst of the present invention, the types of compounds of the active component elements of the catalyst can be selected from a wide range. According to the present invention, the compounds of the active component elements can be selected from one or more of palladium chloride and palladium acetate.

[0011] According to the preparation method of the catalyst of the present invention, the optional range of the types of the compound containing alkaline earth metal elements is relatively wide. According to the present invention, the compound of the alkaline earth metal element is preferably selected from one or more of nitrates and acetates.

[0012] According to the catalyst preparation method of the present invention, the drying conditions in the catalyst preparation step (1) include: temperature of 90-110° C., time of 4-8 h; the calcination conditions include: temperature of 600-800° C., time of 6-8 h.

[0013] According to the preparation method of the catalyst of the present invention, the impregnation temperature in the catalyst preparation step (2) is 40-80°C for 6-8h, and the drying temperature is 120-160°C for 4-8h; According to the catalyst preparation method of the present invention, the reducing atmosphere in the catalyst preparation step (3) is pure hydrogen or a mixture of hydrogen and an inert gas, the reduction temperature is 100-150° C., the reduction pressure is 0.1-3 MPa, and the reduction time is 6-10 h.

[0014] According to a second aspect of the present invention, the present invention also provides a method for preparing tetrahydrocurcumin by continuous hydrogenation of curcumin, the method comprising the following steps: a curcumin solution of a certain concentration and hydrogen are subjected to a hydrogenation reaction under certain reaction conditions in a fixed bed reactor under the action of a catalyst to prepare a tetrahydrocurcumin hydrogenated liquid, and the hydrogenated liquid is subjected to desolventization and recrystallization to obtain a finished tetrahydrocurcumin.

[0015] According to the method for preparing tetrahydrocurcumin by continuous hydrogenation of the present invention, the hydrogenation raw material is a curcumin solution diluted by a solvent. For the diluting solvent, as long as it can form a uniform solution with curcumin and does not participate in the reaction during the hydrogenation process. In the present invention, the solvent is one of methanol, ethanol, acetone, etc.

[0016] According to the method of the present invention, in the curcumin solution, the weight content of curcumin is 1-10%.

[0017] According to the method of the present invention, the fixed bed reactor hydrogenation feedstock passes through the hydrogenation reactor from top to bottom.

[0018] According to the method of the present invention, the conditions of the hydrogenation stage include: a temperature of 40-80°C, a pressure of 0.5-5MPa, a molar ratio of H2 to the hydrogenation raw material curcumin of 5.0-10.0, and a liquid hourly space velocity of the curcumin of 0.1-2.0h -1 .

[0019] Beneficial effects of the method of the present invention (1) The hydrogenation catalyst has low cost and high catalyst activity and selectivity; the conversion rate reaches 100% and the selectivity reaches more than 99%.

[0020] (2) The hydrogenation catalyst has an appropriate surface area and pore volume, so that reactant and product molecules can quickly enter and exit the catalyst pores, thus avoiding the production of excessive hydrogenation products; (3) By introducing alkaline earth metals, the acid sites on the support surface are regulated, the adsorption of the catalyst on the carbon-oxygen double bonds is weakened, and the reaction of the carbon-oxygen double bonds on the catalyst surface is weakened, thereby greatly improving the selectivity of the catalyst; (4) A fixed bed reactor is used for continuous hydrogenation, thus avoiding complicated operation; since the invented catalyst has high activity, good stability and long life, fixed bed continuous hydrogenation can be realized to prepare tetrahydrocurcumin.

[0021] Compared with the prior art, the method of the present invention has the following advantages: simple process, strong operability, high reaction selectivity, and can realize the continuous hydrogenation of curcumin to prepare tetrahydrocurcumin. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Example 6 Catalyst Stability Investigation Results Figure 2 Comparative Example 3 Catalyst Stability Investigation Results DETAILED DESCRIPTION

[0023] The present invention is further described below by a specific example of preparing tetrahydrocurcumin by hydrogenation of curcumin, but the present invention is not limited to the example.

[0024] Example 1 Catalyst preparation: (1) After 3.67 g of magnesium nitrate and macroporous pseudo-boehmite (16.16 g in terms of Al2O3) were fully mixed, extruded, and then the obtained product was dried at 100°C for 8 h, and then calcined at 800°C for 8 h to obtain a magnesium-modified carrier; (2) 0.17 g of palladium chloride was weighed and dissolved in 80 mL of water, and the above solution was impregnated with the magnesium-modified carrier at a temperature of 40°C for 8 h, and the impregnated carrier was dried at a drying temperature of 120°C for 8 h; (3) The impregnated carrier was activated in a reducing atmosphere, and activated in a 10% H2 / N2 (v / v) reducing atmosphere at a temperature of 150°C, a pressure of 3.0 MPa, and a time of 8 h to obtain a 0.5 wt% Pd, 3.0 wt% Mg catalyst CAT-A. The catalyst specific surface area is 195 m 2 / g, pore volume 0.47cm 3 / g.

[0025] Curcumin hydrogenation: A 3 wt% acetone solution of curcumin was pumped into a gas-liquid mixer by a raw material pump, and then into a fixed bed reactor for reaction in the presence of catalyst CAT-A. The hydrogenation reaction conditions were: reaction temperature of 40 °C, pressure of 0.5 MPa, and curcumin liquid hourly space velocity of 0.1 h -1 The molar ratio of hydrogen to curcumin is 5, the conversion rate of curcumin is 99.7%, and the selectivity of tetrahydrocurcumin is 99.1%. After the hydrogenation reaction is completed, it enters the gas-liquid separator through the heat exchanger for gas-liquid separation, and the gas enters the hydrogen circulation system. The hydrogenated liquid is concentrated and recrystallized to obtain the finished curcumin product with a product purity of 99.2%.

[0026] Example 2 Catalyst preparation: (1) After 0.61g magnesium nitrate and macroporous pseudo-boehmite (19.26g in terms of Al2O3) are fully mixed, extrusion is performed, and then the obtained product is dried at 90°C for 4h, and then calcined at 600°C for 6h to obtain a magnesium-modified carrier; (2) 0.03g palladium acetate is weighed and dissolved in 40mL water, and the above solution is impregnated with the magnesium-modified carrier at an impregnation temperature of 80°C for 8h, and the impregnated carrier is dried at a drying temperature of 160°C for 4h; (3) The impregnated carrier is activated in a reducing atmosphere, and the activation treatment is carried out in a 10% H2 / N2 (v / v) reducing atmosphere: the temperature is 120°C, the pressure is 2.0MPa, and the time is 6h, to obtain a 0.3wt% Pd, 0.5wt% Mg catalyst CAT-B. The catalyst specific surface area is 217m 2 / g, pore volume 0.59cm 3 / g.

[0027] Curcumin hydrogenation: A 5 wt% acetone solution of curcumin was pumped into a gas-liquid mixer by a raw material pump, and then into a fixed bed reactor for reaction in the presence of catalyst CAT-B. The hydrogenation reaction conditions were: reaction temperature of 50 °C, pressure of 2 MPa, and curcumin liquid hourly space velocity of 0.5 h -1 The molar ratio of hydrogen to curcumin is 7, the conversion rate of curcumin is 99.5%, and the selectivity of tetrahydrocurcumin is 99.3%. After the hydrogenation reaction is completed, it enters the gas-liquid separator through the heat exchanger for gas-liquid separation, and the gas enters the hydrogen circulation system. The hydrogenated liquid is concentrated and recrystallized to obtain the finished curcumin with a product purity of 99.3%.

[0028] Example 3 Catalyst preparation: (1) 0.87 g of calcium acetate and macroporous pseudo-boehmite (18.80 g in terms of Al2O3) were fully mixed and extruded, and the resulting product was dried at 110°C for 4 h, and then calcined at 700°C for 6 h to obtain a calcium-modified carrier; (2) 0.87 g of palladium chloride was weighed and dissolved in 60 mL of water, and the solution was impregnated with the calcium-modified carrier at a temperature of 60°C for 8 h, and the impregnated carrier was dried at a drying temperature of 120°C for 8 h; (3) The impregnated carrier was activated in a reducing atmosphere, and activated in a 10% H2 / N2 (v / v) reducing atmosphere at a temperature of 150°C, a pressure of 3.0 MPa, and a time of 8 h to obtain a 1.0 wt% Pd, 1.0 wt% Ca catalyst CAT-C. The catalyst specific surface area is 187 m 2 / g, pore volume 0.48cm 3 / g.

[0029] Curcumin hydrogenation: A 1 wt% acetone solution of curcumin was pumped into a gas-liquid mixer by a raw material pump, and then into a fixed bed reactor for reaction in the presence of catalyst CAT-C. The hydrogenation reaction conditions were: reaction temperature of 50 °C, pressure of 1 MPa, and curcumin liquid hourly space velocity of 0.1 h -1 The molar ratio of hydrogen to curcumin is 7, the conversion rate of curcumin is 100%, and the selectivity of tetrahydrocurcumin is 99.2%. After the hydrogenation reaction is completed, it enters the gas-liquid separator through the heat exchanger for gas-liquid separation, and the gas enters the hydrogen circulation system. The hydrogenated liquid is concentrated and recrystallized to obtain the finished curcumin with a product purity of 99.3%.

[0030] Example 4 Catalyst preparation: (1) After 0.85g of calcium acetate and macroporous pseudo-boehmite (18.48g in terms of Al2O3) are fully mixed, extrusion is performed, and then the obtained product is dried at 110°C for 4h, and then calcined at 700°C for 6h to obtain a calcium-modified carrier; (2) 0.67g of palladium chloride is weighed and dissolved in 60mL of water, and the above solution is impregnated with the calcium-modified carrier at a temperature of 60°C for 8h, and the impregnated carrier is dried at a drying temperature of 120°C for 8h; (3) The impregnated carrier is activated in a reducing atmosphere, and the activation treatment is carried out in a 10% H2 / N2 (v / v) reducing atmosphere: the temperature is 150°C, the pressure is 3.0MPa, and the time is 8h, to obtain a 2.0wt% Pd, 1.0wt% Ca catalyst CAT-D. The catalyst specific surface area is 172m 2 / g, pore volume 0.45cm 3 / g.

[0031] Curcumin hydrogenation: A 10 wt% acetone solution of curcumin was pumped into a gas-liquid mixer by a raw material pump, and then into a fixed bed reactor for reaction in the presence of catalyst CAT-D. The hydrogenation reaction conditions were: reaction temperature of 70 °C, pressure of 1 MPa, and curcumin liquid hourly space velocity of 0.1 h -1 The molar ratio of hydrogen to curcumin is 15, the conversion rate of curcumin is 100%, and the selectivity of tetrahydrocurcumin is 99.4%. After the hydrogenation reaction is completed, it enters the gas-liquid separator through the heat exchanger for gas-liquid separation, and the gas enters the hydrogen circulation system. The hydrogenated liquid is concentrated and recrystallized to obtain the finished curcumin with a product purity of 99.4%.

[0032] Example 5 Catalyst preparation: (1) After 1.22 g of magnesium nitrate and macroporous pseudo-boehmite (18.61 g in terms of Al2O3) are fully mixed, extrusion is performed, and the resulting product is dried at 110°C for 4 h, and then calcined at 700°C for 6 h to obtain a magnesium-modified carrier; (2) 0.17 g of palladium chloride is weighed and dissolved in 60 mL of water, and the above solution is impregnated with the magnesium-modified carrier at a temperature of 60°C for 8 h, and the impregnated carrier is dried at a drying temperature of 120°C for 8 h; (3) The impregnated carrier is activated in a reducing atmosphere, and the activation treatment is performed in a 10% H2 / N2 (v / v) reducing atmosphere: the temperature is 150°C, the pressure is 3.0 MPa, and the time is 8 h, to obtain a 0.5 wt% Pd, 1.0 wt% Mg catalyst CAT-E. The catalyst specific surface area is 210 m 2 / g, pore volume 0.68cm 3 / g.

[0033] Curcumin hydrogenation: A 5 wt% acetone solution of curcumin was pumped into a gas-liquid mixer by a raw material pump, and then into a fixed bed reactor for reaction in the presence of catalyst CAT-E. The hydrogenation reaction conditions were: reaction temperature of 50 °C, pressure of 1 MPa, and curcumin liquid hourly space velocity of 1.0 h -1 The molar ratio of hydrogen to curcumin is 15, the conversion rate of curcumin is 99.6%, and the selectivity of tetrahydrocurcumin is 99.2%. After the hydrogenation reaction is completed, it enters the gas-liquid separator through the heat exchanger for gas-liquid separation, and the gas enters the hydrogen circulation system. The hydrogenated liquid is concentrated and recrystallized to obtain the finished curcumin with a product purity of 99.3%.

[0034] Comparative Example 1 The catalyst preparation process is the same as that of Example 1, except that the carrier is not modified with alkaline earth metal Mg. A 0.5 wt% Pd catalyst S-CAT-1 is obtained. The specific surface area of ​​the catalyst is 202 m 2 / g, pore volume 0.52cm 3 / g. The hydrogenation reaction conditions are the same. The conversion rate of curcumin is 99.5%, and the selectivity of tetrahydrocurcumin is 91.2%. The hydrogenated liquid can be concentrated and recrystallized to obtain the finished curcumin with a purity of 91.8%.

[0035] Comparative Example 2 The catalyst preparation process was the same as in Example 1, except that small-pore alumina powder was used instead of large-pore pseudo-boehmite to prepare 0.5 wt% Pd catalyst S-CAT-2. The catalyst specific surface area was 146 m 2 / g, pore volume 0.32cm 3 / g. The hydrogenation reaction conditions are the same. The conversion rate of curcumin is 98.7%, and the selectivity of tetrahydrocurcumin is 93.6%. The hydrogenated liquid can be concentrated and recrystallized to obtain the finished curcumin with a purity of 93.7%.

[0036] Example 6 The catalyst CAT-A of Example 1 was used to investigate the stability of catalyst activity.

[0037] Curcumin hydrogenation: A 3 wt% acetone solution of curcumin was pumped into a gas-liquid mixer by a raw material pump, and then into a fixed bed reactor for reaction in the presence of catalyst CAT-A. The hydrogenation reaction conditions were: reaction temperature of 40 °C, pressure of 0.5 MPa, and curcumin liquid hourly space velocity of 0.1 h -1 The molar ratio of hydrogen to curcumin is 5. The reaction results are shown in Figure 1 .

[0038] Test method: Conversion and selectivity were determined by liquid chromatography.

[0039] Comparative Example 3 The catalyst S-CAT-A of Comparative Example 1 was used to investigate the catalyst activity stability. The test conditions were the same as those of Example 6. The reaction results are shown in Figure 2 .

[0040] It can be seen from the examples and comparative example 1 that the catalyst provided by the present invention has significantly improved selectivity. The comparison between example 1 and comparative example 2 shows that when the pore structure of the catalyst provided by the present invention is controlled within a limited range, the reactant and product molecules can quickly enter and exit the catalyst pores, thereby improving the catalytic activity; the results of the catalyst stability test of example 6 and comparative example 3 show that the catalyst of the present invention has good activity and stability.

[0041] The stability comparison test shows that the conversion rate of the catalyst of the present invention reaches 100% and the selectivity reaches 99%, and it remains stable after 30 days of operation.

[0042] The catalyst whose carrier is not modified with alkaline earth metal has a selectivity of 91%. The conversion rate and selectivity show a downward trend with the operating time, and the stability is poor.

[0043] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A hydrogenation catalyst for preparing tetrahydrocurcumin, comprising a modified carrier and an active component loaded on the modified carrier, wherein the active component is Pd, characterized in that The carrier is alkaline earth metal modified alumina.

2. the hydrogenation catalyst for preparing tetrahydrocurcumin according to claim 1, is characterized in that Based on the total amount of the catalyst, its weight percentage composition is: the active component content is 0.3-2.0%, and the balance is the carrier.

3. the hydrogenation catalyst for preparing tetrahydrocurcumin according to claim 1, is characterized in that Based on the total amount of the modified alumina carrier, the weight content of the alkaline earth metal is 0.5-3%.

4. the hydrogenation catalyst for preparing tetrahydrocurcumin according to claim 1, is characterized in that The alkaline earth metal is one of magnesium, calcium, strontium, barium and radium.

5. the hydrogenation catalyst for preparing tetrahydrocurcumin according to claim 1, described catalyst is characterized in that: catalyst specific surface area is 170-230m 2 / g, pore volume is 0.4-0.8cm 3 / g.

6. A method for preparing a hydrogenation catalyst for preparing tetrahydrocurcumin, comprising the following steps: (1) forming a compound containing an alkaline earth metal element and a carrier and / or a carrier precursor, drying or not drying the resulting mixture, and then calcining the mixture to obtain an alkaline earth metal-modified alumina carrier; (2) contacting the modified alumina support with a solution containing a Pd compound at a certain temperature to obtain an impregnated support, and drying the impregnated support; (3) activating the Pd-containing carrier under a reducing atmosphere to obtain a hydrogenation catalyst for preparing tetrahydrocurcumin.

7. The preparation method of the hydrogenation catalyst for preparing tetrahydrocurcumin according to claim 6, is characterized in that The alkaline earth metal element is one of magnesium, calcium, strontium, barium and radium, and the alkaline earth metal compound is one or more of nitrates and acetates of alkaline earth metals.

8. The method for preparing the hydrogenation catalyst for preparing tetrahydrocurcumin according to claim 6, wherein The drying conditions in step (1) include: a temperature of 90-110° C. and a time of 4-8 hours; the roasting conditions include: a temperature of 600-800° C. and a time of 6-8 hours; the impregnation temperature in step (2) is 40-80° C. and a time of 6-8 hours, and the drying temperature is 120-160° C. and a time of 4-8 hours; the reducing atmosphere in step (3) is pure hydrogen or a mixed gas of hydrogen and an inert gas, the reducing temperature is 100-150° C., the reducing pressure is 0.1-3 MPa, and the reducing time is 6-10 hours.

9. A method for preparing tetrahydrocurcumin by continuous hydrogenation of curcumin, comprising the steps of: a curcumin solution of a certain concentration and hydrogen are subjected to a hydrogenation reaction in a fixed bed reactor under certain reaction conditions in the presence of any catalyst of claims 1-5 to obtain a tetrahydrocurcumin hydrogenated liquid, and the hydrogenated liquid is subjected to desolvation and recrystallization to obtain a finished tetrahydrocurcumin.

10. The method for preparing tetrahydrocurcumin by continuous hydrogenation of curcumin according to claim 9, characterized in that The solvent of the curcumin solution is one of methanol, ethanol and acetone; the hydrogenation conditions include: temperature of 40-80°C, pressure of 0.5-5MPa, molar ratio of H2 to the hydrogenation raw material curcumin of 5.0-10.0, liquid hourly space velocity of the curcumin of 0.1-2.0h -1 , the weight content of curcumin in the curcumin solution is 1-10%.

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