Aldehyde liquid phase hydrogenation catalyst and preparation method thereof

Abstract

This invention discloses an aldehyde liquid-phase hydrogenation catalyst and its preparation method. The catalyst of this invention is a spinel-structured K-Cu. a Cr₂O₄ / SiO₂ catalyst; the molar ratio of Cu / Cr is 0.5–1.0, the mass fraction of SiO₂ in the total catalyst is 10–15 wt%, and the mass fraction of K₂O in the total catalyst is 0.4–0.6 wt%; where 'a' represents Cu a The number of Cu atoms in the Cr2O4 oxide. The catalyst prepared by this invention has a high content of coordinatingly unsaturated copper ions, exhibiting high aldehyde conversion, high alcohol selectivity, and high stability under low copper content conditions, and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of catalytic hydrogenation technology, specifically relating to an aldehyde liquid-phase hydrogenation catalyst and its preparation method. Background Technology

[0002] Butanol and octanol are important raw materials for the synthesis of fine chemical products, mainly used in the production of plasticizers, solvents, dehydrating agents, dispersants, petroleum additives, and synthetic fragrances. Currently, the most widely used butanol carbonyl synthesis process uses propylene, syngas, and hydrogen as raw materials. Under the action of a catalyst, mixed butyraldehyde is generated. The catalyst is separated and recycled. n- / isobutyraldehyde is separated and hydrogenated to produce n-butanol and isobutanol, which are then separated by distillation to obtain n-butanol and isobutanol. n-Butyraldehyde undergoes condensation and dehydration to produce octenal, which is then hydrogenated to produce crude octanol, which is then distilled to obtain the final product, octanol. There are two processes for hydrogenating aldehydes to produce butanol and octanol: gas-phase and liquid-phase methods. The gas-phase method is characterized by mild reaction conditions and simple industrial equipment, but the raw materials need to be pre-vaporized, and there are more byproducts and higher energy consumption. Liquid-phase hydrogenation has low energy consumption, high production capacity, and high product quality, but it requires higher reaction pressure and has higher equipment costs.

[0003] Currently, research on the liquid-phase hydrogenation of butyraldehyde and octenaldehyde mainly focuses on nickel-based catalysts.

[0004] Patent CN103506123B discloses an aldehyde hydrogenation catalyst with a nickel mass fraction of 15%-30% prepared by co-precipitation method, which can be used for liquid-phase hydrogenation of propionaldehyde, butyraldehyde or octenal.

[0005] Zhao Lili et al. (Journal of Chemical Engineering of Chinese Universities, 2017, 31(06): 1333-1339) studied the effect of acidity and alkalinity on the performance of supported Ni-based catalysts in the liquid-phase hydrogenation of octenal.

[0006] Copper-chromium catalysts are widely used in the liquid-phase hydrogenation reaction of furfural. For example, CN106582671A, CN105498788B, CN107952444A, and CN107970942B disclose copper-chromium catalysts with different compositions and preparation methods, which are used in the liquid-phase hydrogenation reaction of furfural to furfuryl alcohol and exhibit high catalytic activity and furfuryl alcohol selectivity.

[0007] However, existing studies have shown that copper-chromium catalyst systems have high copper content, resulting in high levels of heavy component impurities in the liquid-phase hydrogenation reaction of butyraldehyde or octenal. Therefore, developing a suitable catalyst preparation method to promote good dispersion of copper species and to create a highly active and selective liquid-phase aldehyde hydrogenation catalyst with low copper content that can operate stably under liquid-phase feed conditions has practical application value.

[0008] Spinel oxides have a unique spatial structure and can be represented as AB₂O₄, A 2+For tetrahedral coordination, B 3+ The ions are octahedral coordinated. However, when the A / B molar ratio exceeds 0.5, the ions deviate from the ideal distribution and exhibit a disordered distribution. This disordered ion distribution promotes the formation of more coordinate-unsaturated Cu atoms. 2+ Improving catalyst performance is an ideal choice for constructing highly efficient copper-chromium liquid-phase hydrogenation catalysts. Summary of the Invention

[0009] Objective of this invention: To address the shortcomings of existing technologies, this invention provides an aldehyde liquid-phase hydrogenation catalyst and its preparation method. The catalyst prepared by this invention exhibits high aldehyde conversion rate, high alcohol selectivity, and high stability.

[0010] Technical solution: The objective of this invention is achieved through the following technical solution:

[0011] This invention provides a method for preparing an aldehyde liquid-phase hydrogenation catalyst, wherein the catalyst is a spinel-structured K-Cu. a Cr2O4 / SiO2 catalyst; the molar ratio of Cu / Cr is 0.5-1.0, the mass fraction of SiO2 in the total catalyst is 10-15 wt%, and the mass fraction of K2O in the total catalyst is 0.4-0.6 wt%.

[0012] Where a represents Cu a The number of Cu atoms in Cr2O4 oxide.

[0013] The present invention also provides a method for preparing the aldehyde liquid-phase hydrogenation catalyst, comprising the following steps:

[0014] (1) Cu salt, Cr salt and silica sol were dissolved in an aqueous ethanol solution to prepare a mixed solution. An alkaline solution was added to the mixed solution and hydrothermal synthesis was carried out. The oxide precursor was obtained by centrifugation, washing and drying.

[0015] (2) The oxide precursor obtained in step (1) is impregnated in K salt solution, dried and calcined to obtain the catalyst.

[0016] Preferably, in step (1), the Cu salt, Cr salt, and K salt are selected from one or two of the corresponding metal nitrates or acetates.

[0017] Furthermore, the Cu salt, Cr salt, and K salt are selected from the nitrates of the corresponding metals.

[0018] Preferably, in step (1), the molar concentration of metal ions in the mixed solution is 0.2-1.0 mol / L. More preferably, it is 0.4-0.6 mol / L.

[0019] Preferably, in step (1), the alkaline solution is selected from an aqueous solution of at least one of sodium hydroxide or potassium hydroxide.

[0020] Furthermore, the molar concentration of the alkaline solution is 8-12 mol / L, and more preferably 8-10 mol / L.

[0021] Preferably, in step (1), the ethanol-water solution has an ethanol volume concentration of 10-15%; the silica sol is a low-sodium or sodium-free silica sol. Although alkali metals can reduce the strong acid sites of the catalyst to a certain extent to improve product selectivity, the residual sodium content in the silica sol is uncertain. Excessive sodium will reduce the acidic site centers of the catalyst, thereby affecting the catalyst activity; choosing a low-sodium or sodium-free silica sol can avoid the influence of Na ions. In this invention, a quantitative amount of alkali metal K is selected for modification.

[0022] Preferably, in step (1), the hydrothermal synthesis temperature is 150-170℃ and the time is 12-18h.

[0023] Preferably, in step (2), the impregnation treatment is performed by placing the oxide precursor in a K salt solution and letting it stand at room temperature for 24 hours using an equal-volume impregnation method.

[0024] Furthermore, the volume of the K salt solution is calculated based on the pore volume of the oxide precursor, and the volume of the K salt solution can be slightly higher than the pore volume of the oxide precursor.

[0025] Preferably, in steps (1) and (2), the drying temperature is 100-120°C and the drying time is 12-24 hours.

[0026] Furthermore, the drying temperature is 100°C and the drying time is 12 hours.

[0027] Preferably, in step (2), the roasting temperature is 480-520℃ and the roasting time is 2-6h.

[0028] A preferred embodiment of the present invention comprises the following steps in the preparation method of the catalyst:

[0029] (1) Prepare an ethanol aqueous solution of a certain volume concentration, weigh out an appropriate amount of soluble Cu salt, Cr salt and silica sol and dissolve them in the ethanol aqueous solution to prepare a mixed solution, weigh out an appropriate amount of alkali and dissolve it in deionized water to prepare an alkali solution.

[0030] (2) The alkaline solution was added dropwise to the mixed solution and transferred to a stainless steel reactor with a polytetrafluoroethylene liner. Hydrothermal synthesis was carried out at a certain temperature. The oxide precursor was obtained by centrifugation, washing and drying.

[0031] (3) Prepare a K salt solution, place the oxide precursor in the K salt solution for equal volume impregnation, and let it stand at room temperature for 24 hours; after impregnation, dry and calcine to obtain the catalyst.

[0032] The present invention also provides the application of the above-mentioned aldehyde liquid-phase hydrogenation catalyst in the liquid-phase hydrogenation of butyraldehyde or octenaldehyde.

[0033] Beneficial effects:

[0034] (1) This invention provides an aldehyde liquid-phase hydrogenation catalyst. The catalyst exhibits high aldehyde conversion, high alcohol selectivity and high stability under low copper content conditions, and has a wide range of industrial applications.

[0035] (2) This invention provides an aldehyde liquid-phase hydrogenation catalyst. By adjusting the Cu / Cr molar ratio to be slightly higher than that of standard spinel (Cu / Cr ratio of 0.5), a non-stoichiometric copper-rich copper-chromium spinel structure is formed, resulting in more coordinated unsaturated Cu. 2+ After reduction, the site reveals more active sites.

[0036] (3) The present invention provides an aldehyde liquid-phase hydrogenation catalyst, which reduces the strong acidity of the catalyst surface by alkali metal modification, weakens the polymerization reaction, and makes the catalyst exhibit high alcohol selectivity. Attached Figure Description

[0037] Figure 1 This is a TEM image of the catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0038] The technical solution of the present invention will be described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0039] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0040] The silica sol used in the embodiments and comparative examples of this invention was purchased from Shandong Kehan ​​Silicon Source New Material Co., Ltd. as the acidic KHAS-30 silica sol series.

[0041] Example 1

[0042] 0.3 mol of copper nitrate, 0.6 mol of chromium nitrate, and 23.2 g of 30% silica sol were weighed and dissolved in 1800 mL of 12% ethanol aqueous solution to obtain mixed solution I. 3.6 mol of sodium hydroxide was weighed and dissolved in 360 mL of deionized water to obtain aqueous solution II. Aqueous solution II was added dropwise to mixed solution I while stirring. The resulting solution was transferred to a stainless steel reactor equipped with polytetrafluoroethylene and placed in a static oven at 150 °C for hydrothermal treatment for 12 h. The resulting sample was centrifuged, washed, and dried at 100 °C for 12 h to obtain the oxide precursor.

[0043] Weigh 0.60 g of potassium nitrate and dissolve it in 16 mL of water. Place the dried oxide precursor in the potassium salt solution, let it stand at room temperature for 24 h, dry it at 100 °C for 12 h, and then calcine the sample at 500 °C for 4 h to obtain the catalyst.

[0044] The finished catalyst contains 10% SiO2 and 0.4% K2O by mass.

[0045] A Cu / Cr ratio of 0.5 readily yields copper-chromium spinel. In the catalyst prepared in Example 1, the Cu / Cr ratio is higher than 0.5, resulting in some Cu existing in a disordered form within the spinel, forming Cu-rich spinel. TEM images of the catalyst are shown below. Figure 1 .

[0046] Example 2

[0047] Weigh 0.4 mol of copper nitrate, 0.5 mol of chromium nitrate, and 28.0 g of 30% silica sol, and dissolve them in 1800 mL of 12% ethanol aqueous solution to obtain mixed solution I; weigh 3.5 mol of sodium hydroxide and dissolve it in 350 mL of deionized water to obtain aqueous solution II; add aqueous solution II dropwise to mixed solution I while stirring. Transfer the resulting solution to a stainless steel reactor equipped with polytetrafluoroethylene and place it in a static oven at 150℃ for hydrothermal treatment for 12 h. After centrifugation and washing, the obtained sample is dried at 100℃ for 12 h to obtain the oxide precursor.

[0048] Weigh 0.75g of potassium nitrate and dissolve it in 25mL of water. Place the dried oxide precursor in the potassium salt solution and let it stand at room temperature for 24h. Then dry it at 100℃ for 12h. Finally, calcine the sample at 500℃ for 3h to obtain the catalyst.

[0049] The finished catalyst contains 12% SiO2 and 0.5% K2O by mass.

[0050] Example 3

[0051] 0.6 mol of copper nitrate, 0.6 mol of chromium nitrate, and 37.5 g of 30% silica sol were weighed and dissolved in 2350 mL of 11% ethanol aqueous solution to obtain mixed solution I. 4.5 mol of sodium hydroxide was weighed and dissolved in 450 mL of deionized water to obtain aqueous solution II. Aqueous solution II was added dropwise to mixed solution I while stirring. The resulting solution was transferred to a stainless steel reactor equipped with polytetrafluoroethylene and placed in a static oven at 150 °C for hydrothermal treatment for 12 h. The resulting sample was centrifuged, washed, and dried at 100 °C for 12 h to obtain the oxide precursor.

[0052] Weigh 1.20 g of potassium nitrate and dissolve it in 30 mL of water. Place the dried oxide precursor in the potassium salt solution, let it stand at room temperature for 24 h, dry it at 100 °C for 12 h, and then calcine the sample at 500 °C for 4 h to obtain the catalyst.

[0053] The finished catalyst contains 12% SiO2 and 0.6% K2O by mass.

[0054] Example 4

[0055] Weigh 0.4 mol of copper nitrate, 0.5 mol of chromium nitrate, and 35.0 g of 30% silica sol, and dissolve them in 1800 mL of 10% ethanol solution to obtain mixed solution I. Weigh 3.5 mol of sodium hydroxide and dissolve it in 350 mL of deionized water to obtain aqueous solution II. Add aqueous solution II dropwise to mixed solution I while stirring. Transfer the resulting solution to a stainless steel reactor equipped with polytetrafluoroethylene and place it in a static oven at 170℃ for hydrothermal treatment for 12 h. Centrifuge and wash the obtained sample, then dry it at 100℃ for 12 h to obtain the oxide precursor.

[0056] Weigh 0.75 g of potassium nitrate and dissolve it in 20 mL of water. Place the dried oxide precursor in the potassium salt solution, let it stand at room temperature for 24 h, dry it at 100 °C for 12 h, and then calcine the sample at 520 °C for 4 h to obtain the catalyst.

[0057] The finished catalyst contains 15% SiO2 and 0.5% K2O by mass.

[0058] Example 5

[0059] Weigh 0.4 mol of copper nitrate, 0.5 mol of chromium nitrate, and 35.0 g of 30% silica sol, and dissolve them in 1800 mL of 15% ethanol aqueous solution to obtain mixed solution I; weigh 3.5 mol of sodium hydroxide and dissolve it in 350 mL of deionized water to obtain aqueous solution II; add aqueous solution II dropwise to mixed solution I while stirring. Transfer the resulting solution to a stainless steel reactor equipped with polytetrafluoroethylene and place it in a static oven at 160℃ for hydrothermal treatment for 18 h. After centrifugation and washing, the obtained sample is dried at 100℃ for 12 h to obtain the oxide precursor.

[0060] 0.60 g of potassium nitrate was dissolved in 25 mL of water. The dried oxide precursor was placed in the potassium salt solution and allowed to stand at room temperature for 24 h. It was then dried at 100 °C for 12 h. Finally, the sample was calcined at 480 °C for 4 h to obtain the catalyst.

[0061] The finished catalyst contains 15% SiO2 and 0.4% K2O by mass.

[0062] Comparative Example 1

[0063] 0.6 mol of copper nitrate, 0.6 mol of chromium nitrate, and 37.5 g of 30% silica sol were weighed and dissolved in 2350 mL of deionized water to obtain aqueous solution I. 4.5 mol of sodium carbonate was weighed and dissolved in 3750 mL of deionized water to obtain aqueous solution II. Aqueous solution II was added dropwise to aqueous solution I under stirring in a 60°C water bath to induce co-precipitation. The final precipitation endpoint was pH 8.0. After co-precipitation, the mixture was aged at 65°C for 30 min, washed, and dried at 100°C for 12 h to obtain the oxide precursor.

[0064] The subsequent impregnation and roasting process is the same as in Example 3.

[0065] Comparative Example 2

[0066] 0.2 mol of copper nitrate, 0.6 mol of chromium nitrate, and 30.8 g of 30% silica sol were weighed and dissolved in 1800 mL of 12% ethanol aqueous solution to obtain mixed solution I. 3.3 mol of sodium hydroxide was weighed and dissolved in 330 mL of deionized water to obtain aqueous solution II. Aqueous solution II was added dropwise to mixed solution I while stirring. The resulting solution was transferred to a stainless steel reactor equipped with polytetrafluoroethylene and placed in a static oven at 150 °C for hydrothermal treatment for 12 h. The resulting sample was centrifuged, washed, and dried at 100 °C for 12 h to obtain the oxide precursor.

[0067] Weigh 0.66 g of potassium nitrate and dissolve it in 12 mL of water. Place the dried oxide precursor in the potassium salt solution, let it stand at room temperature for 24 h, dry it at 100 °C for 12 h, and then calcine the sample at 500 °C for 4 h to obtain the catalyst.

[0068] Example 6

[0069] In a fixed-bed reactor used in the laboratory, 20 mL of samples prepared in Examples 1-5 and Comparative Example 1 were taken for butyraldehyde liquid-phase hydrogenation activity evaluation. The evaluation conditions were: reaction pressure 2.0 MPa, feed liquid hourly space velocity 2.0 h⁻¹. -1 The ratio of hydrogen to aldehyde was 15, and the ratio of butyraldehyde to butanol was 1:9. The evaluation results are shown in Table 1.

[0070] Table 1 Catalyst performance evaluation results

[0071] catalyst Butyraldehyde conversion rate / % Butanol selectivity / % Example 1 97.85 99.44 Example 2 99.28 99.42 Example 3 98.64 99.32 Example 4 98.29 98.71 Example 5 98.82 99.23 Comparative Example 1 94.23 96.35 Comparative Example 2 86.35 97.21

[0072] Example 7

[0073] In a fixed-bed reactor used in the laboratory, 20 mL of the sample prepared in Example 2 was taken for butyraldehyde liquid-phase hydrogenation stability evaluation, and the evaluation conditions were the same as in Example 6. The evaluation results are shown in Table 2.

[0074] Table 2 Catalyst Stability Evaluation

[0075]

[0076] Example 8

[0077] In a fixed-bed reactor used in the laboratory, 20 mL of samples prepared in Examples 1-5 and Comparative Example 1 were taken for evaluation of the octenal liquid-phase hydrogenation activity. The evaluation conditions were: reaction pressure 2.4 MPa, feed liquid hourly space velocity 2.0 h⁻¹. -1 The ratio of hydrogen to aldehyde was 25, and the ratio of octenal to isooctyl alcohol was 1:9. The evaluation results are shown in Table 3.

[0078] Table 3 Catalyst Performance Evaluation

[0079] catalyst Octenal conversion rate / % Isooctyl alcohol selectivity / % Example 1 97.11 99.20 Example 2 99.30 99.37 Example 3 98.37 98.89 Example 4 98.15 99.03 Example 5 98.94 98.99 Comparative Example 1 93.12 95.87 Comparative Example 2 85.17 96.29

[0080] Example 9

[0081] In a fixed-bed reactor used in the laboratory, 20 mL of the sample prepared in Example 2 was taken for octenal liquid-phase hydrogenation stability evaluation, and the evaluation conditions were the same as in Example 8. The evaluation results are shown in Table 4.

[0082] Table 4 Catalyst Stability Evaluation

[0083]

[0084] The results above show that the spinel structure K-Cu provided by this invention... aCr2O4 / SiO2 catalysts can achieve high aldehyde conversion, high alcohol selectivity, and high stability in the liquid-phase hydrogenation reaction of aldehydes.

[0085] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. An aldehyde liquid-phase hydrogenation catalyst, characterized in that, The catalyst is a spinel-structured K-Cu. a Cr2O4 / SiO2 catalyst; the molar ratio of Cu / Cr is 0.5-1.0, the mass fraction of SiO2 in the total catalyst is 10-15 wt%, and the mass fraction of K2O in the total catalyst is 0.4-0.6 wt%. Where a represents Cu a The number of Cu atoms in Cr2O4 oxide.

2. A method for preparing the aldehyde liquid-phase hydrogenation catalyst according to claim 1, characterized in that, Includes the following steps: (1) Cu salt, Cr salt and silica sol were dissolved in an aqueous ethanol solution to prepare a mixed solution. An alkaline solution was added to the mixed solution and hydrothermal synthesis was carried out. The oxide precursor was obtained by centrifugation, washing and drying. (2) The oxide precursor obtained in step (1) is impregnated in K salt solution, dried and calcined to obtain the catalyst.

3. The preparation method according to claim 2, characterized in that, In step (1), the Cu salt, Cr salt, and K salt are selected from one or two of the corresponding metal nitrates or acetates.

4. The preparation method according to claim 2, characterized in that, In step (1), the alkaline solution is selected from an aqueous solution of at least one of sodium hydroxide or potassium hydroxide.

5. The preparation method according to claim 2, characterized in that, In step (1), the volume concentration of ethanol in the aqueous ethanol solution is 10-15%; the silica sol is a low-sodium or sodium-free silica sol.

6. The preparation method according to claim 2, characterized in that, In step (1), the hydrothermal synthesis is carried out at a temperature of 150-170℃ for 12-18 hours.

7. The preparation method according to claim 2, characterized in that, In step (2), the impregnation treatment is carried out by using an equal volume impregnation method, placing the oxide precursor in a K salt solution and letting it stand at room temperature for 24 hours.

8. The preparation method according to claim 2, characterized in that, In steps (1) and (2), the drying temperature is 100-120℃ and the drying time is 12-24h.

9. The preparation method according to claim 2, characterized in that, In step (2), the roasting temperature is 480-520℃ and the roasting time is 2-6h.

10. The application of the aldehyde liquid-phase hydrogenation catalyst according to claim 1 in the liquid-phase hydrogenation of butyraldehyde or octenaldehyde.

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