Hydrogenated citral catalyst as well as preparation method and application thereof

Abstract

The invention discloses a hydrogenated citral catalyst which is characterized in that the molecular formula of the hydrogenated citral catalyst is Ni-Y / bentonite, an active component nickel ion (Ni) and a transition metal ion (Y) are loaded in a bentonite carrier, the loading capacity of the nickel ion is 20-30%, and the loading capacity of the transition metal ion is 5-12%; the transition metal ions (Y) are iron ions. The method can be used for simultaneously preparing a large number of catalysts, the catalyst preparation time is greatly shortened, no organic solvent is used and generated in the process, and environmental friendliness is facilitated; the Ni-Y / bentonite catalyst prepared by the invention is a powdery solid, is suitable for heterogeneous catalytic citral hydrogenation, and has high catalytic efficiency, the conversion rate of citral reaches 82.8%, and the selectivity of citronellal reaches 100%.

Description

Technical Field

[0001] The invention relates to a monoterpene aldehyde catalyst and application thereof, and in particular to a hydrogenated citral catalyst and a preparation method and application thereof. Background Art

[0002] Citronellal is an important natural fragrance compound, which is widely found in many plant essential oils, especially citronella oil. It has a fresh citrus and herbal aroma and is widely used in spices, food, cosmetics, medicine and insect repellents. Its molecular formula is C 10 H 18 O, belongs to the monoterpene aldehyde compounds, this specific structure makes it widely used in industry and plays an important role. Under the existing technology, citronellal can be obtained by natural extraction and chemical synthesis.

[0003] The existing natural extraction method is steam distillation, which uses steam to heat plants containing citronellal and then condenses, separates and collects citronellal; however, this method has a low extraction rate and many operation steps that take a long time. Currently, there are also solvent extraction and supercritical carbon dioxide extraction. The organic solvent used in the solvent extraction method is expensive and potentially harmful to the environment; while the supercritical carbon dioxide extraction method has high equipment requirements and initial investment costs, and is complex to operate and requires professional technicians.

[0004] In the chemical synthesis method, isopulegol is used as a raw material, isopulegol is dissolved in carbon tetrachloride or other inert solvents, hydrogen chloride gas is slowly introduced under stirring, and the reaction is carried out at room temperature or slightly heated. After the reaction is completed, the solvent is removed by filtering or distillation to obtain chloroisopulegol, and then the chloroisopulegol is dissolved in isopropanol or other suitable solvents, and an appropriate amount of nickel formate or other metal catalysts are added. At a certain temperature and pressure, the reaction mixture is stirred, and after the reaction is completed, citronellal is successfully separated by distillation or extraction; however, the reaction steps of this method are relatively cumbersome, and the hydrogen chloride used is a strong acid with corrosiveness, and there are by-products such as chlorinated compounds that increase the production cost. In the prior art, citronellal is also used as a raw material, and its hydroxyl group is oxidized to an aldehyde group under the action of an oxidant and a copper-chromium catalyst, and citronellal is successfully generated; however, the strong oxidant used in this method is flammable and explosive, which is dangerous, and there are also by-products such as peroxides, carboxylic acids, etc., which lead to a decrease in yield or an increase in cost.

[0005] In summary, the prior art methods for synthesizing citronellal generally have disadvantages such as being environmentally unfriendly, having a large number of by-products, or having a long preparation time, complicated steps, and low yield, which affect its large-scale industrial application. Summary of the invention

[0006] To solve the above technical problems, the present invention provides a hydrogenated citral catalyst and a preparation method and application thereof, aiming to obtain a Ni-Y / bentonite catalyst which is simple to prepare, low in cost, good in stability and can be used for hydrogenated citral reaction.

[0007] To achieve the above purpose, the technical solution provided by the present invention is as follows:

[0008] A hydrogenated citral catalyst has a molecular formula of Ni-Y / bentonite, wherein active components nickel ions (Ni) and transition metal ions (Y) are loaded in a bentonite carrier, wherein the nickel ion loading is 20% to 30%, and the transition metal ion loading is 5% to 12%; the transition metal ions (Y) are iron ions.

[0009] Preferably, the nickel ion loading is 25%, and the transition metal ion loading is 9.2%.

[0010] The preparation method of the hydrogenated citral catalyst as described above comprises the following steps: mixing nickel nitrate hexahydrate, a transition metal salt and a carrier, fully stirring and dispersing the precipitate in a water bath, filtering and directly drying in an oven, taking out, grinding and calcining to obtain a Ni-Y / bentonite catalyst (Y represents a transition metal ion), comprising the following steps:

[0011] (1) Mixing: Weigh nickel nitrate hexahydrate, transition metal salt, and pretreated carrier bentonite and dissolve them in deionized water to obtain a mixed solution;

[0012] (2) stirring precipitation: stirring the mixed solution obtained in step (1) in a water bath, and slowly adding ammonia solution dropwise to react, adding water during the reaction to adjust the pH value to 7-8, and filtering after the reaction, washing the obtained filter cake, and drying;

[0013] (3) calcination: the material obtained after drying in step (2) is crushed and ground, and then calcined;

[0014] (4) Reduction: The material obtained after calcination in step (3) is reduced under a reducing atmosphere to obtain a Ni-Y / bentonite catalyst (a catalyst in which bentonite is loaded with nickel (Ni) and transition metal ions (Y, where Y is Fe)), which is a hydrogenated citral catalyst.

[0015] Preferably, the molar ratio of the carrier described in step (1) to the nickel ions in nickel nitrate hexahydrate is 5:1 (when the nickel loading is 25%); the molar ratio of nickel ions to transition metal salt ions is 2.5:1.

[0016] Preferably, the pretreated carrier bentonite in step (1) is prepared by placing the carrier sodium-based bentonite in a muffle furnace for calcination at a temperature of 450° C. for 4 hours.

[0017] Preferably, the transition metal salt in step (1) is ferric nitrate.

[0018] Preferably, in the water bath stirring in step (2), the water bath temperature is 80°C, the reaction time is 8h (continuous stirring during the reaction), and the stirring speed is 400r / min; the concentration of the ammonia solution is 1.2-1.4mol / L, and the ammonia solution drop rate is 1.8-2ml / min; the pH adjustment in step (2) is to add 40ml of distilled water after reacting for 5h to adjust the pH; the filtration in step (2) is vacuum filtration, and the washing is to wash the filter cake obtained by filtration with distilled water until the filtrate is neutral, and the filtration time is 20-30min; the drying in step (2) is one of oven drying and vacuum drying; the oven drying is to put it in an oven at 80°C and dry it for 8-10 hours, and the vacuum drying is to vacuum dry it for 6-8 hours.

[0019] Preferably, the calcination temperature in step (3) is 450° C., the calcination time is 4 hours, and the heating rate is 5° C. / min.

[0020] Preferably, the reducing atmosphere in step (4) is a mixture of hydrogen and nitrogen in a volume ratio of 1:9; the reducing temperature in step (4) is 450°C for 2.5 hours, and the heating rate is 5°C / min.

[0021] The hydrogenated citral catalyst prepared as above is used in the preparation of citronellal.

[0022] As used above, the operation method is to add the hydrogenated citral catalyst to citral, carry out hydrogenation reaction at 150°C, maintain the hydrogen pressure at 4.5Mpa and the stirring speed at 750r / min, react for 2 hours, and cool to room temperature after the reaction to obtain citronellal.

[0023] Preferably, 0.05 g of hydrogenated citral catalyst is added per 1 g of citral.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The method of the present invention uses bentonite as a carrier, and uses ammonia water dropwise addition and water bath stirring to fully mix and precipitate the carrier and the active component solution. The preparation process is simple to operate, uses fewer instruments, and reduces energy consumption; the carrier (bentonite) and transition metals (nickel and iron) are both cheap raw materials, which can greatly reduce the preparation cost of the catalyst in industrial applications;

[0026] (2) The method of the present invention can prepare a large amount of catalysts at the same time, greatly shortening the catalyst preparation time;

[0027] (3) No organic solvent is used or produced during the method of the present invention, which is environmentally friendly;

[0028] (4) The Ni-Y / bentonite catalyst prepared by the present invention is a powdered solid, which is suitable for heterogeneous catalytic citral hydrogenation and has high catalytic efficiency. The citral conversion rate reaches 82.8% and the citronellal selectivity reaches 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the infrared spectrum of the Ni-Fe / bentonite catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The specific embodiments are described in detail below in conjunction with the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. The raw materials and reagents used in the examples are all commercially available unless otherwise specified. Among them, the specifications of the micro-mechanical stirring reactor are MSC / MSG fast-opening type, and 8860 Agilent gas chromatograph is used for analysis.

[0031] Example 1

[0032] A preparation method of a hydrogenated citral catalyst, the operating steps are as follows:

[0033] (1) Mixing: 5 g of carrier bentonite was calcined in a muffle furnace at 450° C. for 4 h to obtain pretreated carrier bentonite; 6.19 g of nickel nitrate hexahydrate, 3.43 g of ferric nitrate nonahydrate and 5 g of the pretreated carrier bentonite were weighed and placed in a round-bottom flask; then 100 ml of deionized water was added and mixed evenly to obtain a mixed solution;

[0034] (2) stirring precipitation: the mixed solution obtained in step (1) is stirred in a water bath at 80°C, the stirring speed is 400 r / min, and 1.2-1.4 mol / L ammonia solution is slowly added dropwise to react for 8 hours, and the ammonia solution addition rate is 1.8-2 ml / min; after the reaction reaches 5 hours, 40 ml of deionized water is added to adjust the pH value to 7-8; after the reaction is completed, vacuum filter for 20-30 minutes, wash the obtained filter cake with distilled water until the filtrate is neutral, and then put the obtained filter cake into an oven at 80°C and dry it for 8 hours;

[0035] (3) Calcination: The dried material obtained in step (2) is crushed and ground, and then placed in a muffle furnace, and the temperature is raised to 450° C. and calcined for 4 h at a heating rate of 5° C. / min;

[0036] (4) Reduction: The material obtained after calcination in step (3) is placed in a tubular muffle furnace, and the temperature is raised to 450°C for reduction for 2.5 hours at a heating rate of 5°C / min under a reducing atmosphere (the reducing atmosphere is a mixture of hydrogen and nitrogen in a volume ratio of 1:9). The obtained black solid powder is a Ni-Fe / bentonite catalyst (a catalyst in which bentonite is loaded with nickel (Ni) and iron (Fe)), i.e., a hydrogenated citral catalyst; the nickel (Ni) loading in the obtained catalyst is 25% of the mass of the carrier bentonite, and the iron ion loading is 9.2% of the mass of the carrier bentonite. The obtained Ni-Fe / bentonite catalyst is subjected to infrared spectroscopy test, and the results are as follows: Figure 1 shown.

[0037] The application of the hydrogenated citral catalyst prepared by the above-mentioned preparation in the preparation of citronellal, preparation method: weigh 25g citral and 1.25g of the above-mentioned prepared Ni-Fe / bentonite catalyst and put them into a 50mL micro-mechanical stirring autoclave with a capacity, tighten the sealing bolt, connect the hydrogen pipeline, and perform three ventilation processes to ensure that the original air in the reactor is completely replaced, then pass into and maintain 4.5Mpa hydrogen, and carry out hydrogenation reaction at 150°C temperature and stirring speed of 750r / min, reaction time 2 hours, after the reaction is completed, cool to room temperature, and discharge the remaining gas in the kettle, remove the sealing protection bolt, and finally sample with a disposable sterile syringe and filter with a filter membrane to obtain citronellal. The obtained filtrate is diluted and then subjected to gas chromatographic analysis, and it is calculated that the citral conversion rate is 82.8% and the citronellal selectivity is 100%.

[0038] Comparative Example 1

[0039] A preparation method of a hydrogenated citral catalyst, the operating steps are as follows:

[0040] (1) Mixing: 5 g of carrier bentonite was calcined in a muffle furnace at 450° C. for 4 h to obtain pretreated carrier bentonite; 7.43 g of nickel nitrate hexahydrate, 3.43 g of ferric nitrate nonahydrate and 5 g of the pretreated carrier bentonite were weighed and placed in a round-bottom flask; then 100 ml of deionized water was added and mixed evenly to obtain a mixed solution;

[0041] The remaining operations were the same as steps (2) to (4) of Example 1. The nickel (Ni) loading in the obtained catalyst was 30% of the weight of the carrier bentonite, and the iron ion loading was 9.2% of the weight of the carrier bentonite.

[0042] The application of the hydrogenated citral catalyst prepared by the above-mentioned preparation in the preparation of citronellal, preparation method: weigh 25g citral and 1.25g of the above-mentioned prepared Ni-Fe / bentonite catalyst and put them into a 50mL micro-mechanical stirring autoclave with a capacity, tighten the sealing bolt, connect the hydrogen pipeline, and perform three ventilation processes to ensure that the original air in the reactor is completely replaced, then pass into and maintain 4.5Mpa hydrogen, and carry out hydrogenation reaction at 150°C temperature and stirring speed of 750r / min, reaction time 2 hours, after the reaction is completed, cool to room temperature, and discharge the remaining gas in the kettle, remove the sealing protection bolt, and finally sample with a disposable sterile syringe and filter with a filter membrane to obtain citronellal. The filtrate obtained is diluted and then subjected to gas chromatographic analysis, and it is calculated that the citral conversion rate is 68% and the citronellal selectivity is 100%.

[0043] Comparative Example 2

[0044] The application of the obtained hydrogenated citral catalyst in the preparation of citronellal is prepared by adopting the steps (1)-(5) of Example 1, and the preparation method is as follows: 25g of citral and 1.25g of the prepared Ni-Fe / bentonite catalyst are weighed and placed in a 50mL micro-mechanical stirring autoclave, the sealing bolts are tightened, the hydrogen pipeline is connected, and three ventilation treatments are performed to ensure that the original air in the reactor is completely replaced, and then 4.5Mpa hydrogen is introduced and maintained, and the hydrogenation reaction is carried out at a temperature of 150°C and a stirring speed of 750r / min. The reaction time is 2 hours and 40 minutes. After the reaction is completed, it is cooled to room temperature, and the remaining gas in the kettle is discharged, the sealing protection bolts are removed, and finally a disposable sterile syringe is used to take a sample and filtered with a filter membrane to obtain citronellal. The obtained filtrate is diluted and subjected to gas chromatography analysis, and it is calculated that the citral conversion rate is 78.8% and the citronellal selectivity is 100%.

[0045] Comparative Example 3

[0046] The application of the hydrogenated citral catalyst prepared by the steps (1)-(5) of Example 1 in the preparation of citronellal is as follows: 25g of citral and 1.5g of the Ni-Fe / bentonite catalyst prepared by Example 1 are weighed and placed in a 50mL micro-mechanical stirring autoclave, the sealing bolts are tightened, the hydrogen pipeline is connected, and three ventilation treatments are performed to ensure that the original air in the reactor is completely replaced, and then 4.5Mpa of hydrogen is introduced and maintained, and the hydrogenation reaction is carried out at a temperature of 150°C and a stirring speed of 750r / min. The reaction time is 2 hours, and the reaction is cooled to room temperature after the reaction is completed, and the remaining gas in the reactor is discharged, the sealing protection bolts are removed, and finally a disposable sterile syringe is used to take a sample and filtered with a filter membrane to obtain citronellal. The obtained filtrate is diluted and subjected to gas chromatography analysis, and it is calculated that the citral conversion rate is 82.3% and the citronellal selectivity is 94.1%.

[0047] Comparative Example 4

[0048] The application of the obtained hydrogenated citral catalyst in the preparation of citronellal is prepared by using the steps (1)-(5) of Example 1. The preparation method is as follows: 25g of citral and 1.75g ​​of the Ni-Fe / bentonite catalyst prepared in Example 1 are weighed and placed in a 50mL micro-mechanical stirring autoclave, the sealing bolts are tightened, the hydrogen pipeline is connected, and three ventilation treatments are performed to ensure that the original air in the reactor is completely replaced, and then 4.5Mpa of hydrogen is introduced and maintained, and the hydrogenation reaction is carried out at a temperature of 150°C and a stirring speed of 750r / min. The reaction time is 2 hours, and the reaction is cooled to room temperature after the reaction is completed, and the remaining gas in the kettle is discharged, the sealing protection bolts are removed, and finally a disposable sterile syringe is used to take a sample and filter with a filter membrane to obtain citronellal. The obtained filtrate is diluted and subjected to gas chromatography analysis, and it is calculated that the citral conversion rate is 79% and the citronellal selectivity is 92%.

[0049] Comparative Example 5

[0050] The application of the obtained hydrogenated citral catalyst in the preparation of citronellal is prepared by adopting the steps (1)-(5) of Example 1. The preparation method is as follows: 25g of citral and 1.25g of the Ni-Fe / bentonite catalyst prepared in Example 1 are weighed and placed in a 50mL micro-mechanical stirring autoclave, the sealing bolts are tightened, the hydrogen pipeline is connected, and three ventilation treatments are performed to ensure that the original air in the reactor is completely replaced, and then 4.5Mpa of hydrogen is introduced and maintained, and the hydrogenation reaction is carried out at a temperature of 170°C and a stirring speed of 750r / min. The reaction time is 2 hours, and the reaction is cooled to room temperature after the reaction is completed, and the remaining gas in the kettle is discharged, the sealing protection bolts are removed, and finally a disposable sterile syringe is used to take a sample and filtered with a filter membrane to obtain citronellal. The obtained filtrate is diluted and subjected to gas chromatography analysis, and it is calculated that the citral conversion rate is 81.1% and the citronellal selectivity is 84%.

[0051] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A hydrogenated citral catalyst, characterized in that: The molecular formula is Ni-Y / bentonite, wherein the active ingredients nickel ion (Ni) and transition metal ion (Y) are loaded in a bentonite carrier, wherein the nickel ion loading is 20% to 30%, and the transition metal ion loading is 5% to 12%; the transition metal ion (Y) is an iron ion.

2. The hydrogenated citral catalyst according to claim 1, characterized in that: The nickel ion loading is 25%, and the transition metal ion loading is 9.2%.

3. The preparation method of the hydrogenated citral catalyst according to claim 1, characterized in that, The following steps are included: (1) Mixing: Weigh nickel nitrate, transition metal salt and pretreated carrier bentonite and dissolve them in water to obtain a mixed solution; (2) stirring precipitation: stirring the mixed solution obtained in step (1) in a water bath, and slowly adding ammonia solution dropwise to react, adding water during the reaction to adjust the pH value to 7-8, and filtering after the reaction, washing the obtained filter cake, and drying; (3) calcination: taking the material obtained after drying in step (2) and calcining it; (4) Reduction: The material obtained after calcination in step (3) is reduced under a reducing atmosphere to obtain a Ni-Y / bentonite catalyst, which is a hydrogenated citral catalyst.

4. The method for preparing the hydrogenated citral catalyst according to claim 1, characterized in that: In step (1), when the nickel ion loading is 25% and the transition metal ion loading is 9.2%, the molar ratio of the carrier to the nickel ions in nickel nitrate is 5:1; and the molar ratio of the nickel ions to the transition metal salt ions is 2.5:

1.

5. The method for preparing the hydrogenated citral catalyst according to claim 1, characterized in that: The pretreated carrier bentonite described in step (1) is a carrier sodium-based bentonite calcined for 4 hours at a temperature of 450° C.; the transition metal salt described in step (1) is ferric nitrate.

6. The method for preparing the hydrogenated citral catalyst according to claim 1, characterized in that: The water bath temperature in the water bath stirring in step (2) is 80°C, the reaction time is 8h, and the stirring speed is 400r / min; the concentration of the ammonia solution is 1.2-1.4mol / L, and the ammonia solution drop rate is 1.8-2ml / min; the pH adjustment in step (2) is to add 40ml of water after reacting for 5h; the filtration in step (2) is vacuum filtration, and the washing is to wash the filter cake obtained by filtration with water until the filtrate is neutral, and the filtration time is 20-30min; the drying in step (2) is one of oven drying and vacuum drying; the oven drying is to put the mixture into an oven at 80°C and dry it for 8-10 hours, and the vacuum drying is to vacuum dry it for 6-8 hours.

7. The method for preparing the hydrogenated citral catalyst according to claim 1, characterized in that: The calcination temperature in step (3) is 450°C, the calcination time is 4 hours, and the heating rate is 5°C / min; the reducing atmosphere in step (4) is a mixture of hydrogen and nitrogen in a volume ratio of 1:9; the reduction temperature in step (4) is 450°C for 2.5 hours, and the heating rate is 5°C / min.

8. Use of the hydrogenated citral catalyst as claimed in any one of claims 1 to 7 in the preparation of citronellal.

9. The use of the hydrogenated citral catalyst in the preparation of citronellal according to claim 8, characterized in that: The operation method is to add the hydrogenated citral catalyst to citral, carry out hydrogenation reaction at 150° C., maintain the hydrogen pressure at 4.5 MPa and the stirring speed at 750 r / min, react for 2 hours, and cool to room temperature after the reaction to obtain citronellal.

10. Use of the hydrogenated citral catalyst in the preparation of citronellal according to claim 9, characterized in that: 0.05 g of hydrogenated citral catalyst was added per 1 g of citral.

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