A molybdenum oxide modified iridium-based catalyst for selective hydrogenation of cinnamaldehyde to prepare cinnamyl alcohol, and a preparation method and application thereof

Abstract

The application discloses a molybdenum oxide modified iridium-based catalyst for preparing cinnamyl alcohol by selectively hydrogenating cinnamyl aldehyde as well as a preparation method and application of the catalyst. The catalyst is synthesized by a wet impregnation method, and the active component is Ir. A bimetallic catalyst is prepared by adding a second metal additive Mo and simultaneously loading on fumed silica. The second metal additive is introduced to improve the Ir metal dispersion and change the electronic structure, thereby improving the activity on cinnamyl aldehyde and the selectivity on cinnamyl alcohol. The catalyst exhibits good activity and selectivity in selective hydrogenation of cinnamyl aldehyde. The preparation method is simple in operation, and the preparation method is universal and easy to be applied to industrial production.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, its preparation method, and its application. Background Technology

[0002] Cinnamaldehyde (CAL), a typical conjugated carbonyl compound, can yield various products upon hydrogenation, including cinnamyl alcohol (COL) and hydrogenated cinnamaldehyde (HCAL). COL, in particular, has higher added value due to its crucial role in the synthesis of fragrances, functional materials, and pharmaceuticals. From a reaction perspective, the conjugated structure of the C=C and C=O double bonds in the CAL molecule leads to competitive adsorption behavior on catalytic surfaces. Because the C=C bond has a lower hydrogenation energy barrier and stronger π-bond interactions, it is thermodynamically and kinetically dominant, causing the reaction to preferentially proceed along the C=C hydrogenation pathway to generate HCAL. Therefore, achieving preferential activation of the C=O bond depends not only on the catalyst's control over the reactant adsorption configuration but also on the surface electronic structure and interfacial chemical environment.

[0003] Bimetallic catalysis is considered an effective approach to modulate reaction selectivity. By introducing a second metal component, the electronic structure and geometry of the catalyst can be modulated at the atomic scale, thereby constructing a synergistic interface with specific adsorption sites. Previous studies have shown that noble metal-transition metal combinations can modulate the d-band structure of noble metals through electron transfer effects, while simultaneously enhancing interactions with carbonyl oxygen, thus promoting the preferential adsorption and activation of C=O bonds.

[0004] However, existing selective hydrogenation catalysts for cinnamaldehyde still have the following shortcomings: (1) Although single-metal noble metal catalysts (such as Ir, Pt, Pd) have certain hydrogenation activity, they lack effective means to control the competitive hydrogenation of C=C and C=O bonds in cinnamaldehyde molecules, and the selectivity of C=O bond selective hydrogenation to prepare cinnamyl alcohol is generally low; (2) Although some bimetallic catalysts can improve C=O bond selectivity through electronic or geometric effects, the preparation process is complicated (such as atomic layer deposition, pyrolysis of complex organic precursors, etc.), making it difficult to achieve large-scale production. Moreover, the introduction of the second metal often comes at the cost of catalyst activity, making it difficult to achieve both high conversion rate and high selectivity; (3) Existing catalysts have insufficient thermal stability and are prone to metal sintering and agglomeration under high-temperature reduction or reaction conditions, resulting in a reduction of active sites and catalytic performance degradation. Therefore, developing a selective hydrogenation catalyst for cinnamaldehyde with a simple preparation method, good activity and selectivity, and good thermal stability is still a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, its preparation method, and its application. This catalyst improves the dispersion of Ir by introducing a second metal promoter Mo, thereby altering the electronic coordination environment of Ir. This not only significantly enhances the activity of the catalyst but also improves the selectivity for cinnamyl alcohol to a certain extent.

[0006] The first aspect of the object of the present invention is achieved as follows: a catalyst for the selective hydrogenation of cinnamaldehyde to prepare cinnamyl alcohol, comprising an active component, a metal promoter and a support; wherein the active component is Ir, the metal promoter is Mo, and the support is fumed silica; wherein the loading of Ir is 1~10 wt% and the loading of Mo is 0.1~5 wt%.

[0007] The second aspect of the object of the present invention is achieved as follows: a method for preparing a catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, characterized by comprising the following steps:

[0008] S1) IrCl3·3H2O and (NH4)6Mo7O 24 The precursor solutions were prepared by dissolving them separately in deionized water and then dripping them into gaseous SiO2 using a wet impregnation method.

[0009] S2) After the mixture is stirred evenly, it is dried to obtain a solid powder;

[0010] S3) The solid powder is subjected to reduction heat treatment under a hydrogen reducing atmosphere to obtain an Ir-Mo bimetallic catalyst.

[0011] Furthermore, in step S1), the mass ratio of the load of Ir to the load of Mo is 1:0.05 to 1:0.5.

[0012] Furthermore, the stirring time in step S2) is 10~12h; the drying is rotary evaporation drying at a temperature of 70~90℃.

[0013] Furthermore, the hydrogen reducing atmosphere described in step S3) is a mixture of H2 / Ar, H2 / N2, or H2 / He, wherein the volume content of hydrogen is 3~50 vol.

[0014] Furthermore, the reduction heat treatment temperature in step S3) is 400~1000 ℃, the heating rate is 1~20℃ / min, and the reduction heat treatment time is 1~4h.

[0015] The third aspect of the object of the present invention is achieved as follows: a catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, or the application of a catalyst prepared by the above preparation method in a selective hydrogenation reaction, for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol.

[0016] Furthermore, the selective hydrogenation reaction is carried out in a batch reactor. The catalyst, cinnamaldehyde, and a mixed solvent of isopropanol and water are added to the reactor. After being replaced with hydrogen, the reactor is pressurized to the reaction pressure and heated to the reaction temperature. The reaction is carried out under stirring conditions.

[0017] Furthermore, the volume ratio of isopropanol to water in the mixed solvent is 6:1.

[0018] Furthermore, the reaction temperature is 80~120 ℃, the reaction pressure is 0.5~4 MPa, the stirring rate is 600~1000 rpm, and the reaction time is 1~2 h.

[0019] Compared with existing technologies, the advantages of this invention are as follows: The catalyst prepared by this invention employs a simple and easy-to-operate wet impregnation method to simultaneously impregnate Ir and Mo metals onto gaseous SiO2. This preparation method is universal, simple to operate, and easy to industrialize. Compared to single-metal Ir catalysts, the introduction of a second metal promoter improves the dispersion of Ir and alters its electronic coordination environment. This not only significantly enhances the catalyst's activity but also improves the selectivity for cinnamyl alcohol to a certain extent. This invention provides a high-conversion, high-selectivity catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is the reaction equation for the hydrogenation reaction of cinnamaldehyde in this invention.

[0022] Figure 2 The sample characterization and performance study of the 5%Ir-0.5%Mo / SiO2-400 ℃ catalyst prepared in Example 1 of this invention.

[0023] Figure 3 The sample characterization and performance study of the 5%Ir-0.5%Mo / SiO2-600 ℃ catalyst prepared in Example 2 of this invention.

[0024] Figure 4The sample characterization and performance study of the 5%Ir-0.5%Mo / SiO2-800 ℃ catalyst prepared in Example 3 of this invention.

[0025] Figure 5 The sample characterization and performance study of the 5%Ir-0.25%Mo / SiO2-400 ℃ catalyst prepared in Example 4 of this invention.

[0026] Figure 6 This study investigates the characterization and performance of the 5%Ir-1%Mo / SiO2-400 ℃ catalyst prepared in Example 5 of this invention.

[0027] Figure 7 This study investigates the characterization and performance of the 5%Ir-5%Mo / SiO2-400 ℃ catalyst prepared in Example 6 of this invention.

[0028] Figure 8 The sample characterization and performance study of the 5%Ir / SiO2-400 ℃ catalyst prepared in Example 7 of this invention.

[0029] Figure 9 The sample characterization and performance study of the 0.5%Mo / SiO2-400 ℃ catalyst prepared in Example 8 of this invention.

[0030] Figure 10 This is a comparison of the catalyst performance of different Ir-Mo ratios in this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 The diagram illustrates the reaction equation for the selective hydrogenation reaction of cinnamaldehyde according to the present invention. The diagram shows the competitive hydrogenation pathways of the C=C and C=O double bonds in the cinnamaldehyde (CAL) molecule: the target pathway is the selective hydrogenation of the C=O bond to generate cinnamyl alcohol (COL); the side reaction pathway is the preferential hydrogenation of the C=C bond to generate hydrogenated cinnamaldehyde (HCAL). This invention utilizes the electronic modulation effect of the Ir-Mo bimetallic catalyst to achieve preferential adsorption and activation of the C=O bond, thereby achieving highly selective preparation of cinnamyl alcohol.

[0033] Example 1:

[0034] a. Mix an IrCl3•3H2O solution containing 10 mg Ir with a (NH4)6Mo7O solution containing 1 mg Mo. 24 The solution was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 400 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 5%Ir-0.5%Mo / SiO2-400 °C catalyst.

[0035] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0036] Figure 2 The sample characterization and performance study of the 5%Ir-0.5%Mo / SiO2-400 ℃ catalyst prepared in Example 1 of this invention are shown in the left figure, which represents the catalyst performance evaluation, and the right figure represents the XRD characterization of the catalyst. In a 120 min reaction at 400 ℃, the substrate conversion rate of the 5%Ir-0.5%Mo / SiO2-400 ℃ catalyst increased from 40% to nearly 100%, while the product selectivity remained stable at approximately 85%. Its XRD spectrum showed only a weak Ir characteristic peak, demonstrating that the metal active component was highly dispersed.

[0037] Example 2:

[0038] The catalyst preparation process was modified so that the reduction temperature of 400 °C in Example 1 was changed to 600 °C, while the other conditions were the same as in Example 1.

[0039] a. Mix an IrCl3•3H2O solution containing 10 mg Ir with a (NH4)6Mo7O solution containing 1 mg Mo. 24 The solution was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 600 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 5%Ir-0.5%Mo / SiO2-600 °C catalyst.

[0040] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0041] Figure 3 The sample characterization and performance study of the 5%Ir-0.5%Mo / SiO2-600 ℃ catalyst prepared in Example 2 of this invention are shown in the left figure, which represents the catalyst performance evaluation, and the right figure represents the XRD characterization of the catalyst. In a 120 min reaction at 120 ℃, the substrate conversion rate of the 5%Ir-0.5%Mo / SiO2-600 ℃ catalyst increased from approximately 38% to nearly 100%, while the product selectivity remained stably at approximately 80%. Its XRD spectrum showed only a weak Ir characteristic peak, demonstrating that the metal active component was highly dispersed.

[0042] Example 3:

[0043] The catalyst preparation process was modified so that the reduction temperature of 400 °C in Example 1 was replaced with 800 °C, while the other conditions were the same as in Example 1.

[0044] a. Mix an IrCl3•3H2O solution containing 10 mg Ir with a (NH4)6Mo7O solution containing 1 mg Mo. 24 The solution was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 800 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 5%Ir-0.5%Mo / SiO2-800 °C catalyst.

[0045] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0046] Figure 4The sample characterization and performance study of the 5%Ir-0.5%Mo / SiO2-800 ℃ catalyst prepared in Example 3 of this invention are shown in the left figure, which represents the catalyst performance evaluation, and the right figure represents the XRD characterization of the catalyst. In a 120 min reaction at 800 ℃, the substrate conversion rate of the 5%Ir-0.5%Mo / SiO2 catalyst increased from approximately 42% to nearly 100%, while the product selectivity remained stable at approximately 80%. Its XRD spectrum showed only a weak Ir characteristic peak, demonstrating that the metal active component was highly dispersed.

[0047] Example 4:

[0048] The catalyst preparation process uses (NH4)6Mo7O containing 1 mg Mo from Example 1. 24 Change to (NH4)6Mo7O containing 0.5 mg Mo. 24 The remaining conditions are the same as in Example 1.

[0049] a. Mix an IrCl3•3H2O solution containing 10 mg Ir with a (NH4)6Mo7O solution containing 1 mg Mo. 24 The solution was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 400 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 5%Ir-0.25%Mo / SiO2-400 °C catalyst.

[0050] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0051] Figure 5 The sample characterization and performance study of the 5%Ir-0.25%Mo / SiO2-400 ℃ catalyst prepared in Example 4 of this invention are shown in the left figure, which represents the catalyst performance evaluation, and the right figure represents the XRD characterization of the catalyst. In a 120 min reaction at 400℃, the substrate conversion rate of the 5%Ir-0.25%Mo / SiO2-400 ℃ catalyst increased from approximately 40% to nearly 100%, while the product selectivity remained stable at approximately 42%. Due to its tendency to over-hydrogenate, resulting in very low selectivity, its XRD spectrum only showed a weak Ir characteristic peak, indicating that the metal active component was highly dispersed.

[0052] Example 5:

[0053] The catalyst preparation process uses (NH4)6Mo7O containing 1 mg Mo from Example 1. 24 Change to (NH4)6Mo7O containing 2 mg Mo 24 The remaining conditions are the same as in Example 1.

[0054] a. Mix an IrCl3•3H2O solution containing 10 mg Ir with a (NH4)6Mo7O solution containing 2 mg Mo. 24 The solution was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 400 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 5%Ir-1%Mo / SiO2-400 °C catalyst.

[0055] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0056] Figure 6 The left figure shows the catalyst performance evaluation, and the right figure shows the XRD characterization of the catalyst prepared in Example 5 of this invention. The substrate conversion rate of the 5%Ir-1%Mo / SiO2-400℃ catalyst increased from about 20% to nearly 90% in a 120 min reaction at 400℃, while the product selectivity remained stable at about 85%. Its XRD spectrum showed only a weak Ir characteristic peak, indicating that the active metal component was highly dispersed.

[0057] Example 6:

[0058] The catalyst preparation process uses (NH4)6Mo7O containing 1 mg Mo from Example 1. 24 Change to (NH4)6Mo7O containing 10mg Mo 24 The remaining conditions are the same as in Example 1.

[0059] a. Mix an IrCl3•3H2O solution containing 10 mg Ir with a (NH4)6Mo7O solution containing 10 mg Mo.24 The solution was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 400 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 5%Ir-5%Mo / SiO2-400 °C catalyst.

[0060] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0061] Figure 7 The left figure shows the catalyst performance evaluation, and the right figure shows the XRD characterization of the catalyst prepared in Example 6 of this invention. The substrate conversion rate of the 5%Ir-5%Mo / SiO2-400℃ catalyst increased from about 22% to nearly 90% in a 120 min reaction at 120 min, while the product selectivity remained stable at about 85%. Its XRD spectrum showed only a weak Ir characteristic peak, indicating that the active metal component was highly dispersed.

[0062] Example 7:

[0063] The catalyst preparation process uses (NH4)6Mo7O containing 1 mg Mo from Example 1. 24 The method was changed to omit the introduction of Mo, with all other conditions remaining the same as in Example 1.

[0064] a. A solution containing 10 mg IrCl3•3H2O was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 400 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 5% Ir / SiO2-400 °C catalyst.

[0065] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0066] Figure 8 The left figure shows the catalyst performance evaluation, and the right figure shows the XRD characterization of the catalyst prepared in Example 7 of this invention. The substrate conversion rate of the 5%Ir / SiO2-400 ℃ catalyst increased from about 15% to nearly 40% in a 120 min reaction at 120 ℃, while the product selectivity remained stable at about 78%. Its XRD spectrum showed obvious characteristic peaks of metallic Ir.

[0067] Example 8

[0068] The catalyst preparation process was changed from the IrCl3•3H2O containing 10 mg Ir in Example 1 to the one without the introduction of Ir, while the other conditions were the same as in Example 1.

[0069] a. (NH4)6Mo7O containing 1 mg Mo 24 The mixture was added dropwise to 200 mg SiO2, and deionized water was added and stirred for 12 h. The solvent was removed by rotary evaporation at 80 °C to obtain a uniform solid powder. The obtained solid powder was transferred to a quartz boat, placed in a tube furnace, and nitrogen was introduced as a protective gas. The tube furnace was heated to 400 °C at a rate of 5 °C / min, held at that temperature for 2 h, and then allowed to cool naturally to room temperature to obtain a 0.5% Mo / SiO2-400 °C catalyst.

[0070] b. Add 0.05 mol / L cinnamaldehyde, 30 mL isopropanol:water = 6:1, 20 mg catalyst, and 1 mL ethylbenzene to a 100 mL mechanically stirred reactor. After sealing the reactor, purge it five times with pure H2 to completely remove any residual air. Then, introduce pure H2 into the reactor to 2 MPa, raise the temperature to 120 °C, and start stirring (800 rpm). During the reaction, periodically take 0.5 mL samples for gas chromatography analysis.

[0071] Figure 9The left figure shows the catalyst performance evaluation, and the right figure shows the XRD characterization of the 0.5%Mo / SiO2-400 ℃ catalyst prepared in Example 8 of this invention. The catalyst exhibits no catalytic activity at 400 ℃, and its XRD spectrum only shows broad and diffuse peaks of the SiO2 support. No characteristic diffraction peaks corresponding to the Mo species were observed, indicating that the Mo component is highly dispersed.

[0072] As can be seen from Examples 1, 2 and 3, although the reduction temperature was changed, the catalyst performance remained stable, indicating that the catalyst has strong resistance to sintering.

[0073] As can be seen from Examples 1, 4, 5, and 6, the performance of the catalyst is affected by the different proportions of the second metal Mo added. Furthermore, the catalyst performance exhibits a volcano-shaped trend with different Ir-Mo ratios. The optimal catalyst is 5%Ir-0.5%Mo / SiO2-400 °C in Example 1.

[0074] Examples 1, 7, and 8 show that 0.5% Mo / SiO2 at 400 °C has no significant catalytic activity for the hydrogenation of cinnamaldehyde, and 5% Ir / SiO2 at 400 °C has low activity. However, 5% Ir-0.5% Mo / SiO2 at 400 °C improves both activity and selectivity. This indicates that the introduction of a second metal can indeed improve catalytic performance.

[0075] Figure 10 This is a comparison of the catalyst performance of different Ir-Mo ratios according to the present invention. The TOF bar chart shows the conversion frequency of the 5Ir-xMo / SiO2 catalysts with different Mo doping amounts: the TOF value of the single metal 5Ir / SiO2 is the lowest, and the TOF is significantly improved after the introduction of Mo. Among them, the TOF of 5Ir-0.5Mo / SiO2 reaches the peak and is marked with a red pentagram. Further increasing the Mo doping amount leads to a continuous decrease in TOF, proving that appropriate Mo doping can significantly improve the catalytic activity of Ir sites, while excessive Mo will cause activity inhibition.

[0076] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A molybdenum oxide-modified iridium-based catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, characterized in that, It includes an active component, a metal additive, and a support; the active component is Ir, the metal additive is Mo, and the support is fumed silica; wherein the loading of Ir is 1~10 wt%, and the loading of Mo is 0.1~5 wt%.

2. A method for preparing a molybdenum oxide-modified iridium-based catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, characterized in that, Includes the following steps: S1) IrCl3·3H2O and (NH4)6Mo7O 24 The precursor solutions were prepared by dissolving them separately in deionized water and then dripping them into gaseous SiO2 using a wet impregnation method. S2) After the mixture is stirred evenly, it is dried to obtain a solid powder; S3) The solid powder is subjected to reduction heat treatment under a hydrogen reducing atmosphere to obtain an Ir-Mo bimetallic catalyst.

3. The method for preparing a molybdenum oxide-modified iridium-based catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol according to claim 2, characterized in that, In step S1), the mass ratio of the load of Ir to the load of Mo is 1:0.05 to 1:0.

5.

4. The method for preparing a molybdenum oxide-modified iridium-based catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol according to claim 2, characterized in that, The stirring time in step S2) is 10-12 h; the drying is rotary drying at a temperature of 70-90 ℃.

5. The method for preparing a molybdenum oxide-modified iridium-based catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol according to claim 2, characterized in that, The hydrogen reducing atmosphere described in step S3) is a mixture of H2 / Ar, H2 / N2, or H2 / He, wherein the volume content of hydrogen is 3~50 vol.

6. The method for preparing a molybdenum oxide-modified iridium-based catalyst for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol according to claim 2, wherein the temperature of the reduction heat treatment in step S3) is 400~1000 ℃, the heating rate is 1~20℃ / min, and the reduction heat treatment time is 1~4 h.

7. The application of the molybdenum oxide-modified iridium-based catalyst of claim 1 for the selective hydrogenation of cinnamaldehyde to cinnamyl alcohol, or the catalyst prepared by any one of claims 2-6, in the selective hydrogenation reaction, characterized in that... Used for the selective hydrogenation of cinnamaldehyde to prepare cinnamyl alcohol.

8. The application of the catalyst according to claim 7 in selective hydrogenation reactions, characterized in that, The selective hydrogenation reaction is carried out in a batch reactor. The catalyst, cinnamaldehyde, and a mixed solvent of isopropanol and water are added to the reactor. After being replaced with hydrogen, the reactor is pressurized to the reaction pressure and heated to the reaction temperature. The reaction is carried out under stirring conditions.

9. The application of the catalyst according to claim 8 in selective hydrogenation reactions, characterized in that, The volume ratio of isopropanol to water in the mixed solvent is 6:

1.

10. The application of the catalyst according to claim 8 in selective hydrogenation reactions, characterized in that, The reaction temperature is 80~120 ℃, the reaction pressure is 0.5~4 MPa, the stirring rate is 600~1000 rpm, and the reaction time is 1~2 h.

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