Catalyst for selective hydrogenation of crotonaldehyde and preparation method thereof

Abstract

The present invention provides a catalyst for selective hydrogenation of crotonaldehyde and a preparation method thereof, the catalyst comprises a carrier and an active component noble metal Ir, the carrier comprises BN or gamma-Al2O3 or SiO2, and the active component noble metal Ir accounts for 0.5-10% by mass of the carrier; the preparation method of the catalyst comprises the following steps: reducing an Ir precursor through a NaBH4 reduction method to synthesize Ir nanoparticles, and loading the Ir nanoparticles on the carrier, so that the catalyst has good catalytic crotonaldehyde selective hydrogenation activity and selectivity, and has the advantages of low cost, high conversion rate and high selectivity.

Description

Technical Field

[0001] The invention relates to a chemical catalyst and a preparation method thereof, and in particular to a catalyst for selective hydrogenation of crotonaldehyde and a preparation method thereof. Background Art

[0002] α,β-unsaturated alcohols are important fine chemical intermediates. The traditional industrial preparation method uses metal hydrides to reduce α,β-unsaturated aldehydes, but there are problems such as high cost, high pollution and not conducive to large-scale production. Catalytic hydrogenation has become a more attractive alternative with its advantages of environmental protection, economy and high atom economy. However, the coexistence of C=O and C=C double bonds in α,β-unsaturated aldehyde molecules leads to challenges in selective hydrogenation, and the C=C bond is more easily hydrogenated.

[0003] In order to achieve high selectivity for the preparation of α,β-unsaturated alcohols, it is crucial to develop efficient catalysts.

[0004] Studies have shown that the d-band width of the catalyst active metal is related to the selectivity. Wide d-band metals such as Ir are more conducive to the hydrogenation of C=O bonds, thereby improving the selectivity of unsaturated alcohols. Although noble metal catalysts have strong hydrogen activation ability, single metal catalysts often find it difficult to achieve a high selectivity of more than 90%. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a catalyst for the selective hydrogenation of crotonaldehyde, which has good catalytic activity and selectivity for the selective hydrogenation of crotonaldehyde and has the advantages of low cost, high conversion rate and high selectivity.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: a catalyst for selective hydrogenation of crotonaldehyde, the catalyst is composed of a carrier and an active component precious metal Ir, the carrier includes BN or γ-Al2O3 or SiO2, and the mass percentage of the active component precious metal Ir is 0.5-10% of the carrier.

[0007] The present invention also provides a method for preparing a catalyst, so that the obtained catalyst has good catalytic activity and selectivity for selective hydrogenation of crotonaldehyde, and has the advantages of low cost, high conversion rate and high selectivity.

[0008] The technical solution of the present invention is: a method for preparing a catalyst, comprising reducing an Ir precursor by a NaBH4 reduction method to synthesize Ir nanoparticles, and loading the Ir nanoparticles onto a carrier; comprising the following steps: S1: Dissolve tetradecyltrimethylammonium bromide and H2IrCl6 in water, then quickly inject NaBH4 dissolved in ice water, and stir the reaction in a 36°C water bath for 3 hours; S2: washing and dispersing the Ir nanoparticles obtained in step S1 with ethanol; S3: adding the ethanol-dispersed Ir nanoparticles in step S2 to 0.5 g of a carrier selected from BN or γ-Al2O3 or SiO2 and mixing by ultrasonication, and then heating in a 90° C. water bath to remove ethanol, thereby obtaining a supported catalyst; S4: The supported catalyst obtained in step S3 is heated to 200°C, 300°C, and 500°C in a muffle furnace at a heating rate of 5°C / min and calcined for 4 hours to obtain a catalyst Ir / BN-X or Ir / γ-Al2O3-X or Ir / SiO2-X, wherein X represents the calcination temperature.

[0009] In summary, the present invention has the following beneficial effects: The present invention adopts BN or γ-Al2O3 or SiO2 as a carrier to load a noble metal Ir catalyst, which has good catalytic activity and selectivity for the selective hydrogenation of crotonaldehyde. The catalyst has the advantages of low cost, high conversion rate and high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is the XRD pattern of Ir / BN or Ir / γ-Al2O3 or Ir / SiO2 catalyst. DETAILED DESCRIPTION

[0011] The specific implementation modes of the present invention are further described below in conjunction with the accompanying drawings to make the technical solutions of the present invention easier to understand and grasp.

[0012] A catalyst for selective hydrogenation of crotonaldehyde, the catalyst is composed of a carrier and an active component, noble metal Ir, the carrier is BN or γ-Al2O3 or SiO2, and the mass percentage of the active component, noble metal Ir, is 0.5-10% of the carrier.

[0013] In order to obtain the above-mentioned catalyst, the present invention discloses a method for preparing the catalyst: Example

[0014] 0.84g tetradecyltrimethylammonium bromide and 0.078mmol H2IrCl6 were completely dissolved in 65mL water. 7mL NaBH4 solution dissolved in ice water was quickly injected under stirring, and the mixture was stirred for 3 hours in a 36℃ water bath. During the reaction, the color of the solution changed rapidly from brown to dark black, indicating that the Ir precursor was reduced. After the reaction, the obtained dispersion was washed once with ethanol and redispersed with ethanol to obtain an Ir nanoparticle dispersion for use. 0.5g γ-Al2O3 carrier was added to the above ethanol dispersion under ultrasonic conditions. After ultrasonic mixing, it was transferred to a 90℃ constant temperature water bath to evaporate and remove ethanol to obtain an Ir / γ-Al2O3 solid material. The obtained solid material was heated to 300℃ at a heating rate of 5℃ / min and calcined in a muffle furnace for 4 hours to obtain an Ir / γ-Al2O3-300 catalyst.

[0015] Structural characterization of catalysts: X-ray diffraction (XRD) was used to characterize the catalyst structure. Figure 1 This is the XRD spectrum of the reduced Ir / γ-Al2O3-300-300 catalyst (the second 300 here represents the catalyst test reduction temperature). Figure 1 As shown, the XRD pattern of the catalyst is highly consistent with the standard card PDF-77-0396 of Al2O3, indicating that the carrier is Al2O3 crystal phase. The weak diffraction peak observed at 2θ value of 40.7° corresponds to the (111) crystal plane of metal Ir (PDF-46-1044), indicating that the Ir active component exists in the catalyst in metallic form.

[0016] Catalyst activity evaluation: The activity evaluation of the catalyst was carried out on a fixed bed reactor. First, 0.05 g of the prepared catalyst was placed in a quartz reaction tube (inner diameter 8 mm), and the temperature was raised to 300 ° C at a heating rate of 5 ° C / min and reduced for 1 hour in an atmosphere of 18 mL / min high-purity hydrogen (99.999%). Subsequently, the temperature was naturally cooled to a reaction temperature of 80 ° C in a hydrogen atmosphere. The gas line was switched, hydrogen was introduced, and 0 ° C crotonaldehyde vapor (ice water bath conditions) was brought into the reaction tube through a bubbler to react with the catalyst in a gas-solid phase catalytic reaction. The molar ratio of hydrogen to crotonaldehyde was 100:1. The reaction tail gas was analyzed online by an online gas chromatograph GC-2014 (equipped with an FID detector and a DB-Wax capillary column (30m×0.25mm×0.25μm) to determine the product composition and evaluate the activity and selectivity of the catalyst. The catalytic reaction performance data are shown in Table 1. Example

[0017] The preparation method of the catalyst is the same as that of Example 1, except that the carrier is replaced by SiO2 from γ-Al2O3 to obtain an Ir / SiO2-300 catalyst.

[0018] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 The XRD spectrum of the reduced Ir / SiO2-300-300 catalyst (the second 300 here represents the catalyst test reduction temperature). Figure 1 As shown, the XRD pattern of the catalyst is highly consistent with the standard card PDF-82-1554 of SiO2, indicating that the carrier is a SiO2 crystal phase. The weak diffraction peak observed at a 2θ value of 40.7° corresponds to the (111) crystal plane of metal Ir (PDF-46-1044), indicating that the Ir active component exists in the catalyst in a metallic state.

[0019] Catalyst activity evaluation: The catalyst activity evaluation method is the same as in Example 1. The catalytic reaction performance data are shown in Table 1. Example

[0020] The preparation method of the catalyst is the same as that of Example 1, except that the carrier is replaced by BN instead of γ-Al2O3, and the calcination step is omitted in the preparation process to directly obtain the Ir / BN-uncalcined catalyst.

[0021] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 is the XRD pattern of the reduced Ir / BN-uncalcined-300 catalyst (the second 300 here represents the catalyst test reduction temperature). Figure 1 As shown, the XRD pattern of the catalyst is highly consistent with the standard card PDF-73-2095 of BN, indicating that the support is a BN crystal phase. The weak diffraction peak observed at a 2θ value of 40.7° corresponds to the (111) crystal plane of metal Ir (PDF-46-1044), indicating that the Ir active component exists in the catalyst in a metallic state.

[0022] Catalyst activity evaluation: The catalyst activity evaluation method is the same as in Example 1. The catalytic reaction performance data are shown in Table 1. Example

[0023] The preparation method of the catalyst is the same as that of Example 3, except that the calcination temperature is 200° C. to obtain an Ir / BN-200 catalyst.

[0024] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 The XRD spectrum of the reduced Ir / BN-200-300 catalyst (the second 300 here represents the catalyst test reduction temperature). Figure 1 As shown, the XRD structure of the catalyst is similar to that of the Ir / BN-uncalcined catalyst prepared in Example 3.

[0025] Catalyst activity evaluation: The catalyst activity evaluation method is the same as in Example 1. The catalytic reaction performance data are shown in Table 1. Example

[0026] The preparation method of the catalyst is the same as that of Example 3, except that the calcination temperature is 300° C. to obtain an Ir / BN-300 catalyst.

[0027] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 The XRD spectrum of the reduced Ir / BN-300-300 catalyst (the second 300 here represents the catalyst test reduction temperature). Figure 1 As shown, the XRD structure of the catalyst is similar to that of the Ir / BN-uncalcined catalyst prepared in Example 3.

[0028] Catalyst activity evaluation: The catalyst activity evaluation method is the same as in Example 1. The catalytic reaction performance data are shown in Table 1. Example

[0029] The preparation method of the catalyst is the same as that of Example 3, except that the calcination temperature is 500° C. to obtain an Ir / BN-500 catalyst.

[0030] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 The XRD spectrum of the reduced Ir / BN-500-300 catalyst (here 300 represents the catalyst test reduction temperature). Figure 1 As shown, the XRD structure of the catalyst is similar to that of the Ir / BN-uncalcined catalyst prepared in Example 3.

[0031] Catalyst activity evaluation: The catalyst activity evaluation method is the same as in Example 1. The catalytic reaction performance data are shown in Table 1. Example

[0032] The preparation method of the catalyst is the same as that of Example 5.

[0033] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 This is the XRD pattern of the Ir / BN-300-unreduced catalyst (“unreduced” here means that the catalyst was not subjected to reduction treatment during the test). Figure 1 As shown, the XRD structure of the catalyst is similar to that of the Ir / BN-uncalcined catalyst prepared in Example 3.

[0034] Catalyst activity evaluation: The catalyst activity evaluation method is the same as that in Example 1, except that the catalyst reduction temperature is 80° C. and the reduction time is 0.5 hours. The catalytic reaction performance data is shown in Table 1. Example

[0035] The preparation method of the catalyst is the same as that of Example 5.

[0036] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 The XRD spectrum of the reduced Ir / BN-300-200 catalyst (here 200 represents the catalyst test reduction temperature). Figure 1 As shown, the XRD structure of the catalyst is similar to that of the Ir / BN-uncalcined catalyst prepared in Example 3.

[0037] Catalyst activity evaluation: The catalyst activity evaluation method is the same as that in Example 1, except that the catalyst reduction temperature is 200° C. and the reduction time is 1 hour. The catalytic reaction performance data is shown in Table 1. Example

[0038] The preparation method of the catalyst is the same as that of Example 5.

[0039] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 The XRD spectrum of the reduced Ir / BN-300-500 catalyst (here 500 represents the catalyst test reduction temperature). Figure 1 As shown, the XRD structure of the catalyst is similar to that of the Ir / BN-uncalcined catalyst prepared in Example 3.

[0040] Catalyst activity evaluation: The catalyst activity evaluation method is the same as that in Example 1, except that the catalyst reduction temperature is 500° C. and the reduction time is 1 hour. The catalytic reaction performance data is shown in Table 1.

[0041] Embodiment 10: The catalyst was prepared by impregnation. A certain amount of H2IrCl6 solution was added to 0.5g of BN carrier to adjust the Ir loading to 2wt.%. After impregnation at room temperature for 4 hours, excess water was evaporated in a 90℃ water bath with continuous stirring. The obtained solid sample was calcined at 300℃ in air atmosphere for 4 hours to obtain Ir / BN (impregnation)-300 catalyst.

[0042] Structural characterization of catalysts: The catalyst structure was characterized by XRD. Figure 1 The XRD pattern of the reduced Ir / BN (impregnated)-300-300 catalyst (the second 300 here represents the catalyst test reduction temperature). Figure 1 As shown, the XRD structure of the catalyst is similar to that of the Ir / BN-uncalcined catalyst prepared in Example 3.

[0043] Catalyst activity evaluation: The catalyst activity evaluation method is the same as in Example 1. The catalytic reaction performance data are shown in Table 1.

[0044] Table 1: Performance of catalysts of Examples 1 to 10 Note: For example, Ir / BN-XY, where X represents the calcination temperature and Y represents the H2 reduction temperature.

[0045] It can be seen that the catalyst of the present invention has a good catalytic effect on the selective hydrogenation of crotonaldehyde, and the catalyst of Example 5 has the best catalytic effect. The catalyst has the characteristics of low cost, high conversion rate and high selectivity.

[0046] Of course, the above are only typical examples of the present invention. In addition, the present invention may also have many other specific implementations. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims

1. A catalyst for the selective hydrogenation of crotonaldehyde, characterized in that: The catalyst consists of a carrier and an active component of precious metal Ir. The carrier includes BN or γ-Al2O3 or SiO2. The mass percentage of the active component of precious metal Ir is 0.5-10% of the carrier.

2. A method for preparing the catalyst as claimed in claim 1, characterized in that: Including through The NaBH4 reduction method reduces an Ir precursor to synthesize Ir nanoparticles, and loads the Ir nanoparticles onto a carrier; the method comprises the following steps: S1: Dissolve tetradecyltrimethylammonium bromide and H2IrCl6 in water, then quickly inject NaBH4 dissolved in ice water, and stir the reaction in a 36°C water bath for 3 hours; S2: washing and dispersing the Ir nanoparticles obtained in step S1 with ethanol; S3: adding the ethanol-dispersed Ir nanoparticles in step S2 to 0.5 g of a carrier selected from BN or γ-Al2O3 or SiO2 and mixing by ultrasonication, and then heating in a 90° C. water bath to remove ethanol, thereby obtaining a supported catalyst; S4: The supported catalyst obtained in step S3 is heated to 200°C, 300°C, and 500°C in a muffle furnace at a heating rate of 5°C / min and calcined for 4 hours to obtain a catalyst Ir / BN-X or Ir / γ-Al2O3-X or Ir / SiO2-X, wherein X represents the calcination temperature.

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