A supported heterogeneous catalyst, its preparation method and use

Abstract

The application discloses a supported heterogeneous catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: step 1, mixing a cobalt salt and a rare earth metal salt in a solvent to obtain a mixed solution, and adding hydrated citric acid to react to obtain a gel; step 2, mixing the gel after aging with a carrier precursor in deionized water, drying to remove water, and calcining to obtain the supported heterogeneous catalyst. In the synthesis aspect of the catalyst, the rare earth metal is introduced as an additive to improve the catalytic performance; in the carrier selection aspect, the selection of the carrier precursor is relatively innovative. The obtained catalyst has the characteristics of being beneficial to separation and recovery, high propylene conversion rate, high isobutyl aldehyde selectivity and low catalyst deactivation.

Description

Technical Field

[0001] This invention relates to the field of isobutyraldehyde preparation technology, specifically to a supported heterogeneous catalyst, its preparation method, and its application. Background Technology

[0002] The hydroformylation reaction was first discovered by Roelen in 1938 during his Fischer-Tropsch synthesis research at Ruhr Chemical Company in Germany. It is a catalytic process in which olefins react with syngas (CO and H2) in the presence of a catalyst to produce aldehydes or alcohols. Given its wide range of applications, economic benefits, and significant theoretical implications, this reaction is widely recognized as one of the most important petrochemical technologies today. Among industrialized hydroformylation reactions, the hydroformylation of propylene is the most representative, serving not only as a key step in the production of butanol and octanol, but also for the preparation of a variety of commercially valuable chemical products.

[0003] Both the main product, n-butyraldehyde, and the byproduct, isobutyraldehyde, of the propylene hydroformylation reaction have significant application value. n-Butyraldehyde can be converted to n-butanol via hydrogenation, which is widely used as a key intermediate in the synthesis of butyl esters. Isobutyraldehyde, traditionally considered a byproduct, has seen its industrial value increasingly prominent with the rapid development of downstream industries such as neopentyl glycol. Currently, isobutyraldehyde is an important raw material for neopentyl glycol synthesis, with continuously growing market demand and a widening supply gap. Therefore, developing efficient and economical propylene hydroformylation catalysts has become a key technological challenge for promoting the development of the neopentyl glycol industry. In existing technologies, catalytic systems with phosphine as a ligand and rhodium (Rh) as a metal center have exhibited significant catalytic activity in the propylene hydroformylation reaction and have been widely applied industrially. For example, patent CN102826967 uses rhodium-triphenylphosphine as a catalyst; patent CN116209651A uses rhodium-bisphosphine ligand as a catalyst; patent US20230357115A1 uses rhodium-phosphonocyclopentane-phosphite catalyst; and patent CN115124572A uses rhodium-multidentate phosphine ligand microcatalyst.

[0004] While this catalytic system exhibits excellent activity and selectivity, it faces three key limitations in industrial applications: 1) the high cost of the precious metal rhodium significantly increases production costs; 2) the toxicity and environmental risks associated with phosphine ligands; and 3) the homogeneous system leads to difficulties in catalyst recovery and significant loss of precious metals. These factors collectively affect the economic viability and sustainability of this technology. Therefore, the development of heterogeneous catalysts has emerged. For example, patent CN104475161A discloses a method for preparing a hydroformylation catalyst using Rh supported on ferromagnetic nanoparticles, but the catalyst still uses phosphine ligands and exhibits low selectivity. Another example is patent CN107537481A, which discloses an Rh catalyst supported on nano-zinc oxide, with low rhodium content but lacking regioselectivity.

[0005] In view of this, in order to overcome the problems of separation and recovery, loss of precious metals and low selectivity of traditional homogeneous catalytic systems and heterogeneous catalytic systems, this invention provides a novel high-efficiency heterogeneous catalyst suitable for the hydroformylation of propylene to isobutyraldehyde, providing an innovative solution for achieving efficient, economical and environmentally friendly industrial catalytic processes. Summary of the Invention

[0006] This invention addresses the problems of precious metal loss and low isobutyraldehyde selectivity in the catalytic system of the propylene hydroformylation reaction by providing a method for preparing a heterogeneous catalyst. This catalyst exhibits high catalytic activity and high isobutyraldehyde selectivity, while also possessing good stability. Furthermore, the catalyst and reaction products are easily separated in this preparation method, making it highly valuable for industrial applications.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a supported heterogeneous catalyst, comprising the following steps: Step 1: Mix cobalt salt and rare earth metal salt in a solvent to obtain a mixed solution, and add hydrated citric acid to react and obtain a gel; Step 2: After aging the gel, mix it with the carrier precursor in deionized water, dry it to remove moisture, and then calcine it to obtain the supported heterogeneous catalyst.

[0008] This invention selects rare earth metal salts as catalyst promoters to enhance the catalytic activity of the catalyst. The core role of rare earth metals lies in the precise control of the electronic structure and surface properties of cobalt-based catalysts, optimizing the catalyst's adsorption and activation capabilities for reactants. This results in a significant increase in the selectivity of the catalyst for isobutyraldehyde in the propylene hydroformylation reaction. On the other hand, rare earth metals can act as structural promoters, effectively inhibiting the possible agglomeration and sintering of cobalt active species during the reaction, thus improving the catalyst's resistance to deactivation and its lifespan. Simultaneously, using a cheaper Co-based heterogeneous catalyst avoids dependence on expensive rhodium (Rh) metals and also avoids the problems of difficult rhodium recovery and significant loss, achieving high catalytic activity and isobutyraldehyde selectivity in a non-precious metal catalyst.

[0009] The cobalt salt includes one or more of cobalt nitrate, cobalt acetate, cobalt sulfate, and cobalt chloride; The rare earth metal salts include one or more of lanthanum nitrate, cerium nitrate, neodymium nitrate, and erbium nitrate; The molar concentration of cobalt salt in the mixed solution is 0.1-2 mol / L, and the molar concentration of rare earth metal salt in the mixed solution is 0.1-2 mol / L. The carrier precursor includes one or more of tetraethoxysilane, tetrabutyl titanate, aluminum n-butoxide, and zirconium n-butoxide. The selected carriers are all liquid metal alkoxides, which can mix with the active metal component at the molecular level during the hydrolysis stage, thus better loading the active component. Tetraethoxysilane is preferred, as the silica carrier formed by this precursor is chemically inert and will not trigger side reactions such as cracking, isomerization, or polymerization during the hydroformylation reaction.

[0010] The reaction temperature in step 1 is 50-80℃, and the reaction time is 2-4 hours. The molar amount of hydrated citric acid is 1-2 times the molar amount of the metal element in the mixed solution. Adding too much or too little hydrated citric acid will affect gel formation.

[0011] In step 2, the aging temperature is 90-120℃ and the aging time is 10-14 h; In step 2, the drying process involves stirring at 70-90℃ to evaporate moisture, followed by drying at 80-100℃ for 8-14 hours. And / or, the calcination is performed at 550-750℃ for 2-6 h.

[0012] The supported heterogeneous catalyst contains 2-5 wt% cobalt and 0.5-2 wt% rare earth metals.

[0013] The present invention also provides a supported heterogeneous catalyst prepared by the preparation method described above.

[0014] The present invention also provides the application of the supported heterogeneous catalyst in the hydroformylation reaction of propylene.

[0015] The application of the supported heterogeneous catalyst in the hydroformylation reaction of propylene specifically includes the following steps: isobutanol is prepared by catalytic reaction of propylene and syngas as raw materials under the action of the supported heterogeneous catalyst; wherein the syngas is a mixture of hydrogen and carbon monoxide.

[0016] Before the reaction, the catalyst is activated under the following conditions: nitrogen flow rate of 50-150 mL / min, 160-200℃, and 1-5MPa for 1-4 hours.

[0017] The catalytic reaction is carried out at a temperature of 150-200℃, with a molar ratio of propylene, CO, and H2 of 1~4:1~5:1~5 and a gas flow rate of 100-500 mL / min.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) In terms of the synthesis of the catalyst in this invention, rare earth metals are introduced as promoters to improve catalytic performance; in terms of the selection of the support, common supports are selected, especially the selection of the support precursor is relatively innovative. The obtained catalyst has the characteristics of being conducive to separation and recovery, high propylene conversion rate, high isobutyraldehyde selectivity, and catalyst not being easily deactivated.

[0019] (2) Existing technologies mainly rely on homogeneous catalysts formed by expensive rhodium (Rh) metal centers and phosphine ligands. This results in extremely high production costs and difficulties in rhodium metal recovery, leading to significant losses. In this invention, cobalt (Co) is used as the main active component, eliminating the use of the precious metal rhodium. Using the inexpensive and readily available transition metal cobalt to replace the precious metal rhodium significantly reduces the raw material cost of the catalyst; at the same time, the catalyst is heterogeneous, which facilitates recovery.

[0020] (3) In this invention, rare earth metal oxides are introduced as additives, which not only synergistically enhance the catalytic activity of cobalt, but also significantly improve the selectivity of the target product "isobutyraldehyde", which is difficult to achieve with traditional non-precious metal catalysts. Attached Figure Description

[0021] Figure 1 The image shows a scanning electron microscope (SEM) image of the catalyst prepared in Example 1. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0023] All raw materials used in the following specific implementation methods were purchased from the market.

[0024] Example 1 A mixed solution of cobalt nitrate (1 mol / L) and lanthanum nitrate (0.2 mol / L) in ethanol was prepared, and 5 g of hydrated citric acid was added. The mixture was heated in a water bath at 70°C for 2 h to obtain a translucent gel.

[0025] A semi-transparent gel was aged in an oven at 80°C for 12 h to obtain a catalyst precursor. 2 g of the catalyst precursor and 10 g of tetraethoxysilane were added to 80 mL of deionized water. After stirring and evaporating most of the water at 70°C, the mixture was dried in an oven at 100°C for 12 h. After grinding, the mixture was calcined in a muffle furnace at 550°C for 5 h to obtain the Co-La / SiO2 catalyst. The microstructure of the catalyst is shown in the image. Figure 1 As shown.

[0026] The reaction performance of the catalyst prepared above was evaluated in a high-pressure fixed-bed reactor. The catalyst loading was 10 mL. Before feeding, N2 was introduced to activate the catalyst under the following conditions: temperature 200℃, pressure 2 MPa, N2 flow rate 100 mL / min, and time 2 h. Pure propylene and syngas were used as feedstocks in the reaction. The feedstock gas flow rate was 200 mL / min, the molar ratio of propylene, CO, and H2 was 1:1.2:1.2, the reaction temperature was 200℃, and the reaction pressure was 1 MPa.

[0027] After the reaction temperature stabilized for 0.5 h, the product was collected from the condenser after the reactor. GC gas chromatography was used to perform qualitative and quantitative analysis on the product after the reaction, and the conversion rate of propylene and the selectivity of isobutyraldehyde were calculated.

[0028] Example 2 The 0.2 mol / L lanthanum nitrate in Example 1 was replaced with 0.2 mol / L cerium nitrate, and the other steps were the same as in Example 1.

[0029] Example 3 The 0.2 mol / L lanthanum nitrate in Example 1 was replaced with 0.2 mol / L neodymium nitrate, and the other steps were the same as in Example 1.

[0030] Example 4 Replace the 0.2 mol / L lanthanum nitrate in Example 1 with 0.2 mol / L erbium nitrate, and follow the same steps as in Example 1.

[0031] Example 5 Prepare an ethanolic solution containing 1 mol / L cobalt nitrate and 0.2 mol / L lanthanum nitrate, add 5 g of hydrated citric acid, and heat in a water bath at 80°C for 2 h to obtain a translucent gel.

[0032] The translucent gel was aged in an oven at 80°C for 12 h to obtain a catalyst precursor. 2 g of the catalyst precursor and 11.8 g of aluminum n-butoxide were added to 80 mL of deionized water. After stirring and evaporating a large amount of water at 70°C, the mixture was dried in an oven at 100°C for 12 h. After grinding, the mixture was calcined in a muffle furnace at 550°C for 5 h to obtain the Co-La / Al2O3 catalyst.

[0033] The reaction performance of the prepared catalyst was evaluated in a high-pressure fixed-bed reactor. The catalyst loading was 10 mL. Before feeding, N2 was introduced to activate the catalyst under the following conditions: temperature 200 °C, pressure 2 MPa, N2 flow rate 100 mL / min, and time 2 h. Pure propylene and syngas were used as feedstocks in the reaction. The feedstock gas flow rate was 200 mL / min, the molar ratio of propylene, CO, and H2 was 1:1.2:1.2, the reaction temperature was 200 °C, and the reaction pressure was 1 MPa.

[0034] After the reaction temperature stabilized for 0.5 h, the product was collected from the condenser after the reactor. GC gas chromatography was used to perform qualitative and quantitative analysis on the product after the reaction, and the conversion rate of propylene and the selectivity of isobutyraldehyde were calculated.

[0035] Example 6 The 0.2 mol / L lanthanum nitrate in Example 1 was replaced with 0.2 mol / L cerium nitrate, and the other steps were the same as in Example 5.

[0036] Example 7 The 0.2 mol / L lanthanum nitrate in Example 1 was replaced with 0.2 mol / L neodymium nitrate, and the other steps were the same as in Example 5.

[0037] Example 8 The 0.2 mol / L lanthanum nitrate in Example 1 was replaced with 0.2 mol / L erbium nitrate, and the other steps were the same as in Example 5.

[0038] Example 9 A 1 mol / L cobalt nitrate and 0.2 mol / L lanthanum nitrate ethanol solution was prepared, and 5 g of hydrated citric acid was added. The mixture was heated in a water bath at 80 °C for 2 h to obtain a translucent gel. The translucent gel was aged in an oven at 80 °C to obtain a catalyst precursor. 2 g of the catalyst precursor and 18.4 g of n-butoxide zirconium were added to 80 mL of deionized water. After stirring and evaporating most of the water at 70 °C, the mixture was dried in an oven at 100 °C for 12 h. After grinding, the mixture was calcined in a muffle furnace at 550 °C for 5 h to obtain the Co-La / ZrO2 catalyst.

[0039] The reaction performance of the prepared catalyst was evaluated in a high-pressure fixed-bed reactor. The catalyst loading was 10 mL. Before feeding, N2 was introduced to activate the catalyst under the following conditions: temperature 300 °C, pressure 2 MPa, N2 flow rate 100 mL / min, and time 2 h. Pure propylene and syngas were used as feedstocks in the reaction. The feedstock gas flow rate was 200 mL / min, the molar ratio of propylene, CO, and H2 was 1:1.2:1.2, the reaction temperature was 200 °C, and the reaction pressure was 1 MPa.

[0040] After the reaction temperature stabilized for 0.5 h, the product was collected from the condenser after the reactor. GC gas chromatography was used to perform qualitative and quantitative analysis on the product after the reaction, and the conversion rate of propylene and the selectivity of isobutyraldehyde were calculated.

[0041] Example 10 Replace the 0.2 mol / L lanthanum nitrate in Example 1 with 0.2 mol / L cerium nitrate, and follow the same steps as in Example 9.

[0042] Example 11 The 0.2 mol / L lanthanum nitrate in Example 1 was replaced with 0.2 mol / L neodymium nitrate, and the other steps were the same as in Example 9.

[0043] Example 12 Replace the 0.2 mol / L lanthanum nitrate in Example 1 with 0.2 mol / L erbium nitrate, and follow the same steps as in Example 9.

[0044] Comparative Example 1 A 1 mol / L cobalt nitrate ethanol solution was prepared, and 5 g of hydrated citric acid was added. The solution was heated in a water bath at 80°C for 2 hours to obtain a translucent gel. The translucent gel was aged in an oven at 80°C for 12 hours to obtain a catalyst precursor. 2 g of the catalyst precursor and 10 g of tetraethoxysilane were added to 80 mL of deionized water. After stirring and evaporating most of the water at 70°C, the solution was dried in an oven at 100°C for 12 hours. After grinding, the solution was calcined in a muffle furnace at 550°C for 5 hours to obtain the Co / ZrO2 catalyst.

[0045] The reaction performance of the prepared catalyst was evaluated in a high-pressure fixed-bed reactor. The catalyst loading was 10 mL. Before feeding, N2 was introduced to activate the catalyst under the following conditions: temperature 200 °C, pressure 2 MPa, N2 flow rate 100 mL / min, and time 2 h. Pure propylene and syngas were used as feedstocks in the reaction. The feedstock gas flow rate was 200 mL / min, the molar ratio of propylene, CO, and H2 was 1:1.2:1.2, the reaction temperature was 200 °C, and the reaction pressure was 1 MPa.

[0046] After the reaction temperature stabilized for 0.5 h, the product was collected from the condenser after the reactor. GC gas chromatography was used to perform qualitative and quantitative analysis on the product after the reaction, and the conversion rate of propylene and the selectivity of isobutyraldehyde were calculated.

[0047] Comparative Example 2 Replace 10 g of tetraethoxysilane in Comparative Example 1 with 11.8 g of aluminum n-butoxide, and follow the same steps as in Comparative Example 1.

[0048] Comparative Example 3 Replace 10 g of tetraethoxysilane in Comparative Example 1 with 18.4 g of zirconium n-butoxide, and follow the same steps as in Comparative Example 1.

[0049] Table 1. Catalytic evaluation results of the catalysts prepared in the examples and comparative examples.

[0050] As can be seen from Examples 1-12 and Comparative Examples 1-3 in the table, the propylene conversion rate and isobutyraldehyde selectivity of the catalyst are significantly improved after the introduction of rare earth metal oxides, and the catalyst activity is significantly improved.

[0051] Example 13 The catalysts prepared in Examples 1 and 5 were subjected to long-term treatment in a high-pressure fixed-bed reactor for 100 h. The catalyst loading was 10 mL. Pure propylene and syngas were used as feedstocks, with a feedstock gas flow rate of 200 mL / min, a molar ratio of propylene, CO, and H2 of 1:1.2:1.2, a reaction temperature of 200 °C, and a reaction pressure of 1 MPa. Performance evaluation was performed, and the product was collected from the condenser after the reactor. GC gas chromatography was used for qualitative and quantitative analysis of the reaction products, and the conversion rate of propylene and the selectivity of isobutyraldehyde were calculated.

[0052] Table 2. Evaluation results of catalysts after long-term treatment

[0053] Compared with the catalysts in Table 1 before treatment, the catalysts after long-term treatment showed no significant changes in propylene conversion and isobutyraldehyde selectivity, highlighting the excellent stability of the catalysts.

Claims

1. A method for preparing a supported heterogeneous catalyst, characterized in that, Including the following steps: Step 1: Mix cobalt salt and rare earth metal salt in a solvent to obtain a mixed solution, and add hydrated citric acid to react and obtain a gel; Step 2: After aging the gel, mix it with the carrier precursor in deionized water, dry it to remove moisture, and then calcine it to obtain the supported heterogeneous catalyst.

2. The method for preparing the supported heterogeneous catalyst according to claim 1, characterized in that, The cobalt salt includes one or more of cobalt nitrate, cobalt acetate, cobalt sulfate, and cobalt chloride; And / or, the rare earth metal salt includes one or more of lanthanum nitrate, cerium nitrate, neodymium nitrate, and erbium nitrate; And / or, the molar concentration of cobalt salt in the mixed solution is 0.1-2 mol / L, and the molar concentration of rare earth metal salt in the mixed solution is 0.1-2 mol / L; And / or, the carrier precursor includes one or more of tetraethoxysilane, tetrabutyl titanate, aluminum n-butoxide, and zirconium n-butoxide.

3. The method for preparing the supported heterogeneous catalyst according to claim 1, characterized in that, The reaction temperature in step 1 is 50-80℃, and the reaction time is 2-4 hours. And / or, the molar amount of the hydrated citric acid is 1-2 times the molar amount of the metal element in the mixed solution.

4. The method for preparing the supported heterogeneous catalyst according to claim 1, characterized in that, In step 2, the aging temperature is 90-120℃ and the aging time is 10-14 h; In step 2, the drying process involves stirring at 70-90℃ to evaporate moisture, followed by drying at 80-100℃ for 8-14 hours. And / or, the calcination is performed at 550-750℃ for 2-6 h.

5. The method for preparing the supported heterogeneous catalyst according to claim 1, characterized in that, The supported heterogeneous catalyst contains 2-5 wt% cobalt and 0.5-2 wt% rare earth metals.

6. The supported heterogeneous catalyst prepared by the preparation method according to any one of claims 1-5.

7. The application of the supported heterogeneous catalyst according to claim 6 in the hydroformylation reaction of propylene.

8. The application according to claim 7, characterized in that, The method includes the following steps: preparing isobutanol by catalytic reaction of propylene and syngas as raw materials under the action of the supported heterogeneous catalyst as described in claim 6; wherein the syngas is a mixture of hydrogen and carbon monoxide.

9. The application according to claim 8, characterized in that, Before the reaction, the catalyst is activated under the following conditions: nitrogen flow rate of 50-150 mL / min, 160-200℃, and 1-5MPa for 1-4 hours.

10. The application according to claim 8, characterized in that, The catalytic reaction is carried out at a temperature of 150-200℃, with a molar ratio of propylene, CO, and H2 of 1~4:1~5:1~5 and a gas flow rate of 100-500 mL / min.

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