Monatomic dispersion catalyst for preparing linear aldehyde from olefin as well as preparation method and application of monatomic dispersion catalyst

Abstract

The invention belongs to the field of catalysts, and particularly relates to a molecular sieve packaged monatomic dispersion rhodium-based catalyst for preparing high-value linear aldehyde and derivatives thereof through hydroformylation of C3-C18 alpha-olefin and olefin in the C3-C18 alpha-olefin as well as a preparation method and application of the molecular sieve packaged monatomic dispersion rhodium-based catalyst. According to the catalyst, catalytic active metal rhodium and organic amine are utilized to form a monatomic complex, the monatomic complex is synergistically used as a template agent for molecular sieve synthesis, and strong base is utilized to promote molecular sieve nucleation and growth, so that precise monatomic-scale packaging of catalytic active metal in molecular sieve pore channels is realized; and a key intermediate for linear hydroformylation of olefin (isomerization) is confined through a special topological structure of the molecular sieve, so that efficient hydroformylation reaction is realized, and relatively high conversion rate, conversion frequency, total conversion number and linear selectivity are achieved. The catalyst does not need to be pre-activated by high-temperature hydrogen before being used, and has the same selectivity as a homogeneous catalyst Xantphos-rhodium; and the method has the advantages of easy separation, stable recycling of common equipment and the like.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst technology and relates to a single-atom dispersed catalyst for preparing linear aldehydes from olefins, a preparation method and application thereof, and more specifically to a molecular sieve-encapsulated single-atom dispersed rhodium-based catalyst for preparing high-value linear aldehydes and their derivatives through the hydroformylation of C3-C18 α-olefins and their internal olefins (isomerization), a preparation method and application thereof. Background Art

[0002] The hydroformylation reaction, discovered by Roelen in 1938, synthesizes aldehydes from olefins and synthesis gas (carbon monoxide and hydrogen). With 100% atom economy, it has developed into the largest homogeneous catalytic reaction in industrial application, with an annual output of over 16 million tons of high-value-added linear aldehydes and their derivatives. It is a core technology for the production of fine chemicals such as detergents (with an annual output value exceeding US$46.2 billion) and plasticizers (with an annual output value exceeding US$13.9 billion).

[0003] The linear selective hydroformylation of olefins is an industrial production technology for the synthesis of C3-C21 straight-chain aldehydes and their derived alcohol esters. Currently, the main industrially used hydroformylation catalysts are cobalt and rhodium phosphine ligand complexes, which are mainly used for the hydroformylation of C2-C8 α-olefins. The main products include propionaldehyde, butyraldehyde, valeraldehyde, heptanal, octanal, nonanal, and other derivative chemicals. The first generation of catalysts was cobalt without added ligands, and the catalytic reaction conditions were harsh (temperature 110-180 o C, pressure 200-300 atmospheres), the operating cost and safety risks are high, and it has been basically eliminated. There are very few cobalt-based hydroformylation units still in operation. The second generation catalyst is a cobalt complex with an electron-donating monophosphine ligand added. The selectivity is improved and it can be operated under milder conditions (temperature 160-200 oC, pressure 50-100 atmospheres), is developed, applied, and monopolized by Shell in the Netherlands, and catalytic technology information is never disclosed. A third-generation catalyst, developed, applied, and owned by companies such as DuPont in the United States, BASF in Germany, and Mitsubishi in Japan, uses rhodium and a monodentate organophosphine ligand (triphenylphosphine) as a catalyst. It can convert α-olefins into linear aldehydes at relatively low pressures (<50 atmospheres), but relies on the addition of a ligand in an amount several tens of times the metal to stabilize the dominant complex and achieve relatively modest selectivity. An improved third-generation catalyst, developed, applied, and monopolized by Eastman and Dow in the United States, uses rhodium and a bidentate phosphine ligand (such as Bisbi and UC-44) as a catalyst. It primarily produces butyraldehyde, valeraldehyde, and butanol, which are used in high-value-added plasticizers. A fourth-generation catalyst, developed, applied, and owned by Ruhrchemie-Rhodium Onepoulenc, is a rhodium-water-soluble monodentate phosphine ligand (TPPTS) complex. Because it is a two-phase catalytic reaction system, also known as heterogeneous catalysis technology, it is only applicable to the hydroformylation of propylene and 1-butene, and is operated on a small scale. Unfortunately, domestic fine chemical companies lack proprietary catalysts and production processes. Most use third-generation rhodium-triphenylphosphine catalysts licensed from European and American companies. Compared to the improved third-generation rhodium-bidentate phosphine catalysts commonly used internationally, these catalysts are costly and subsequent R&D is limited by external resources.

[0004] Homogeneous catalysts are usually recycled by distillation separation. When using C5 and above olefins as raw materials, due to the high boiling point of the product, the phosphine ligand is more likely to decompose and coordinate dissociate during the high-temperature distillation separation process, which also causes disadvantages such as leaching of precious metals and discharge of phosphorus-containing waste.

[0005] Heterogeneous catalysts typically have low synthesis costs, easy product separation, and stable catalyst recycling. Over 85% of industrial catalytic processes utilize heterogeneous catalysts. Therefore, the development of highly stable, active, and selective heterogeneous catalysts for the hydroformylation of olefins to expand the production of long-chain linear aldehydes and their derived alcoholic acid esters has attracted widespread attention from both academia and industry. This is particularly true for the hydroformylation of more widely available and inexpensive olefins and their internal olefins, such as post-ether C4s and long-chain olefins from the downstream coal chemical industry, to produce high-value new chemical materials.

[0006] Due to their potential advantages, heterogeneous catalysts have seen rapid development in hydroformylation reactions in recent years. However, their activity and selectivity have not yet reached the level of industrial application. Early reports of heterogeneous catalysts, such as rhodium-based catalysts supported on inorganic supports, immobilized metal phosphine ligand complexes, and rhodium-based catalysts encapsulated on porous supports, have been reported for hydroformylation reactions. However, the activity, chemoselectivity, and regioselectivity of heterogeneous catalysts are generally lower than those of homogeneous catalysts. In particular, heterogeneous catalysts lack linear selectivity, typically producing a 1-3:1 mixture of linear and branched aldehydes. This is far from the requirement of more than 96% linear aldehyde for industrial applications, and therefore lacks potential for application (Chem., 2022, 8, 2630-2658). In recent years, Nature, 2024,629,597-602; J. Am. Chem. Soc., 2025, 147, 3, 2726-2736; Nat. Catal., 2024, 7, 666–677 and CN115999629B disclosed molecular sieve-encapsulated 0.5-1.2 nm sub-nano rhodium cluster catalysts for the hydroformylation of α-olefins to produce aldehydes. Molecular sieves with different topological structures were used to encapsulate noble metal sub-nanoclusters, and organic ligands were used to coordinate and modify the sub-nano metal clusters exposed on their surfaces, achieving efficient hydroformylation of α-olefins with high conversion (up to 98%), chemical selectivity (up to 95.8%), and very high product normal-to-iso ratio (linear / branched aldehyde selectivity up to 565 / 1). Unfortunately, the sub-nanometer rhodium cluster catalyst has a low utilization efficiency of precious metal atoms, and requires the addition of organic ligands to modify the unencapsulated external metal. It needs to be pre-activated in a hydrogen atmosphere before use, which is inconvenient to use. The total conversion number needs to be further improved, and it has not been used in the hydroformylation of internal olefins.

[0007] To address the above difficulties, the present invention develops a single-atom dispersed catalyst for olefin-to-linear aldehyde production, as well as its preparation method and application. The catalyst is used for the hydroformylation of C3-C18 α-olefins and their internal olefins (isomerization) to produce high-value linear aldehydes, and can be used in kettle and fixed-bed reactors. Summary of the Invention

[0008] To address the technical challenges, the present invention aims to provide a single-atom-dispersed catalyst for olefin production of linear aldehydes, its preparation method, and its application. Specifically, it provides a molecular sieve-encapsulated single-atom-dispersed rhodium-based catalyst for the hydroformylation of C3-C18 α-olefins and their internal olefins (isomerization) to produce high-value linear aldehydes, as well as its preparation method and application. This innovative single-atom-dispersed rhodium-based catalyst utilizes a catalytically active metal rhodium to form a single-atom complex with an organic amine, which synergistically serves as a template for molecular sieve synthesis. A strong base is then used to promote molecular sieve nucleation and growth, achieving precise single-atom encapsulation of the catalytically active metal within the molecular sieve pores. Furthermore, the unique topological structure of the molecular sieve confines key intermediates in the linear hydroformylation of olefins (isomerization), ensuring high activity, high chemoselectivity, high conversion rate, high conversion frequency, high total conversion number, and very high linear selectivity for the efficient hydroformylation of α-olefins and their internal olefins. The catalyst described herein is a heterogeneous single-atom catalyst, thus overcoming the drawbacks of homogeneous catalysts, such as the difficulty in separating the product from the catalyst, and the low precious metal utilization efficiency, low activity, and poor selectivity of conventional heterogeneous catalysts. In addition, the single-atom catalyst described in the present invention has cheap and easily available raw materials for preparation, simple synthesis steps, easy to scale up production, does not require high-temperature hydrogen atmosphere pre-activation treatment before use, has mild reaction conditions, does not require the use of organic ligands in the reaction, is easy to separate the reaction products, can be operated without solvent, can be stably recycled, is suitable for common equipment such as autoclave and fixed bed, etc., has good catalytic activity, stability and selectivity, and has industrial promotion and application value.

[0009] The active metal rhodium in the catalyst of the present invention is confined in the molecular sieve pores in the form of single-atom sites. The synthesis method has the advantages of cheap and readily available raw materials, simple preparation, simple post-processing, and suitability for industrial production. In addition, the single-atom catalyst has the characteristics of high reaction activity, high aldehyde selectivity, high linear selectivity, and high stability, and has great practical value.

[0010] In order to achieve the above objectives, the technical solutions of the present invention are as follows.

[0011] A molecular sieve-encapsulated single-atom dispersed catalyst for preparing linear aldehydes from olefins. The synthetic raw materials include a molecular sieve template, a silicon source, a soluble rhodium salt, a metal strong base compound, an organic amine compound and deionized water.

[0012] Furthermore, the molecular sieve template is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, 1.8-octanediamine, tetrabutylammonium bromide or trioctylamine.

[0013] Furthermore, the silicon source is one or more combinations of tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, sodium silicate, sodium metasilicate or methyl orthosilicate.

[0014] Furthermore, the soluble rhodium salt is rhodium chloride, rhodium nitrate or rhodium sulfate.

[0015] Furthermore, the metal strong base compound is one or more combinations of potassium hydroxide, sodium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate or potassium carbonate.

[0016] Furthermore, the organic amine compound is one or a combination of ethylenediamine, N,N'-dimethylethylenediamine, N,N'-tetramethylethylenediamine, 1,2-cyclohexanediamine, dimethylamine, diethylamine, trimethylamine, triethylamine, triethanolamine, ethanolamine or propanolamine.

[0017] A method for preparing a molecular sieve-encapsulated single-atom dispersed catalyst for olefin-to-linear aldehyde production comprises the following steps: Step 1: adding a molecular sieve template and a metal base compound to deionized water and stirring at room temperature to obtain a solution 1; Step 2: adding a silicon source to solution 1 and stirring at room temperature to obtain solution 2; Step 3, adding 0.48 mol / L soluble rhodium salt aqueous solution and organic amine compound to solution 2, and stirring at room temperature to obtain solution 3; Step 4: Transfer solution 3 to a hydrothermal synthesis reactor, place it in an oven for high-temperature reaction for a period of time, take it out and separate the solid sample by centrifugation, wash the sample with deionized water and ethanol, and dry it at 70°C overnight to obtain a dry solid sample; Step 5: calcining the dried solid sample at high temperature in an air atmosphere to obtain a monoatom-dispersed catalyst for preparing linear aldehydes from olefins.

[0018] Furthermore, the mass fraction of the strong base corresponding to the metal is 0-1.0%.

[0019] Furthermore, the molar ratio of the metal strong base compound to the silicon source is 0.04-0.15:1.

[0020] Furthermore, the molar ratio of the molecular sieve template to the silicon source is 0.2-1.0:1.

[0021] Furthermore, the molar ratio of the soluble rhodium salt to the silicon source is 0.0005-0.0065:1.

[0022] Furthermore, the volume ratio of the organic amine compound to the 0.48 mol / L soluble rhodium salt aqueous solution is 0.6-6.0:1.

[0023] Furthermore, the mass fraction of the active metal rhodium is 0.06-0.2%.

[0024] Furthermore, the mass ratio of the molecular sieve template to deionized water is 0.4-0.8:1.

[0025] Furthermore, in step 1, the stirring time is 5 to 15 minutes.

[0026] Furthermore, the stirring time in step 2 is 5 to 10 hours.

[0027] Furthermore, the stirring time in step 3 is 10 to 30 minutes.

[0028] Furthermore, in step 4, the oven temperature is 140° C. to 200° C., and the reaction time is 60 to 90 hours.

[0029] Furthermore, the calcination temperature in step 5 is 500° C. to 700° C., and the calcination time is 3 to 5 hours.

[0030] The monoatom dispersed catalyst for preparing linear aldehydes from olefins provided by the present invention can be used in the preparation of high-value linear aldehydes by hydroformylation of C3-C18 α-olefins and their internal olefins (isomerization).

[0031] The specific operation of the olefin hydroformylation reaction is as follows: molecular sieve-encapsulated single-atom catalyst, olefin and solvent are added to a reactor equipped with a magnetic stirrer, carbon monoxide and hydrogen are introduced, and the reaction is carried out at the reaction pressure and reaction temperature.

[0032] Furthermore, the molecular sieve encapsulated single-atom catalyst is directly used in the reaction without the need for high-temperature preactivation in a hydrogen atmosphere.

[0033] Furthermore, the olefin is C4-C 18 One or a mixture of α-olefins and internal olefins.

[0034] Furthermore, the solvent is one or more of no solvent, target aldehyde product, toluene, xylene, 1,4-dioxane, tetrahydrofuran, methanol, ethanol, and isopropanol.

[0035] Furthermore, the molar ratio of olefin to active metal rhodium is 100-1,000,000:1.

[0036] Furthermore, the molar ratio of carbon monoxide to hydrogen is 1 to 3:1.

[0037] Furthermore, the reaction pressure is 0.5~5.0MPa.

[0038] Furthermore, the reaction temperature is 30-120°C.

[0039] Compared with the prior art, the present invention has the following beneficial effects.

[0040] 1. The present invention provides a single-atom dispersed catalyst for the preparation of linear aldehydes from olefins, which is a type of single-atom catalyst with novel structure and low cost. The single-atom catalyst is a molecular sieve-encapsulated single-atom catalyst, composed of a single-atom catalytically active center (single-atom rhodium) and a molecular sieve carrier, wherein the catalytically active center is single-atom rhodium. The single-atom catalyst utilizes catalytically active metals and organic amines to form a single-atom complex that acts as a template for molecular sieve synthesis. At the same time, a strong base is added to promote the nucleation and growth of the molecular sieve, thereby achieving precise single-atom-level encapsulation of the catalytically active metal in the molecular sieve pores. The single-atom catalyst utilizes the special topological structure of the molecular sieve to confine key intermediates in the linear hydroformylation of olefins (isomerization), thereby achieving efficient hydroformylation of α-olefins and their internal olefins. The molecular sieve is used to load and confine supramolecules to regulate the selectivity of the hydroformylation reaction.

[0041] 2. The molecular sieve encapsulated single-atom catalyst synthesis method of the present invention has the advantages of cheap and readily available raw materials, simple synthesis steps, easy scale-up production, no need for high-temperature hydrogen atmosphere pre-activation treatment before use, mild reaction conditions, no need for the use of organic ligands in the reaction, easy separation of reaction products, solvent-free operation, stable recycling, and applicability to common equipment such as kettle and fixed bed. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The molecular sieves encapsulated single atom catalyst Rh in each embodiment of the present invention and the comparative example x K y -MFI spectra (a, XRD diffraction pattern; b, FTIR spectrum).

[0043] Figure 2 The molecular sieve encapsulated single atom catalyst Rh prepared in Example 1 of the present invention 0.07 K 0.79 -MFI spectrum (a, HR-TEM lattice image; b, HAADF-STEM rhodium single atom dispersion image; c, rhodium single atom encapsulated in molecular sieve pores image; d, rhodium single atom encapsulated in molecular sieve pores comparison display image; e, HR-TEM element distribution image). DETAILED DESCRIPTION

[0044] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0045] A molecular sieve-encapsulated single-atom dispersed catalyst for preparing linear aldehydes from olefins. The synthetic raw materials include a molecular sieve template, a silicon source, a soluble rhodium salt, a metal strong base compound, an organic amine compound and deionized water.

[0046] Furthermore, the molecular sieve template is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, 1.8-octanediamine, tetrabutylammonium bromide or trioctylamine, etc., which is used to control the synthesis of molecular sieves with characteristic topological structures.

[0047] Furthermore, the silicon source is one or more combinations of tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, sodium silicate, sodium metasilicate or methyl orthosilicate; preferably, tetraethyl orthosilicate.

[0048] Furthermore, the soluble rhodium salt is rhodium chloride, rhodium nitrate or rhodium sulfate; preferably, rhodium chloride.

[0049] Furthermore, the metal strong base compound is one or more combinations of potassium hydroxide, sodium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate or potassium carbonate; preferably, potassium hydroxide.

[0050] Furthermore, the organic amine compound is one or more of ethylenediamine, N,N'-dimethylethylenediamine, N,N'-tetramethylethylenediamine, 1,2-cyclohexanediamine, dimethylamine, diethylamine, trimethylamine, triethylamine, triethanolamine, ethanolamine or propanolamine; preferably, ethylenediamine, N,N'-dimethylethylenediamine; more preferably, ethylenediamine.

[0051] A method for preparing a molecular sieve-encapsulated single-atom dispersed catalyst for olefin-to-linear aldehyde production comprises the following steps: Step 1: adding a molecular sieve template and a metal base compound to deionized water and stirring at room temperature to obtain a solution 1; Step 2: adding a silicon source to solution 1 and stirring at room temperature to obtain solution 2; Step 3, adding 0.48 mol / L soluble rhodium salt aqueous solution and organic amine compound to solution 2, and stirring at room temperature to obtain solution 3; Step 4: Transfer solution 3 to a hydrothermal synthesis reactor, place it in an oven for high-temperature reaction for a period of time, take it out and separate the solid sample by centrifugation, wash the sample with deionized water and ethanol, and dry it at 70°C overnight to obtain a dry solid sample; Step 5: calcining the dried solid sample at high temperature in an air atmosphere to obtain a monoatom-dispersed catalyst for preparing linear aldehydes from olefins.

[0052] Furthermore, the mass fraction of the strong base corresponding to the metal is 0-1.0%; preferably, 0.7-0.9%.

[0053] Furthermore, the molar ratio of the metal strong base compound to the silicon source is 0.04-0.15:1; preferably, the molar ratio is 0.08-0.12:1.

[0054] Furthermore, the molar ratio of the molecular sieve template to the silicon source is 0.2-1.0:1; preferably, 0.2-0.6:1.

[0055] Furthermore, the molar ratio of the soluble rhodium salt to the silicon source is 0.0005-0.0065:1; preferably, the molar ratio is 0.0005-0.0010:1.

[0056] Furthermore, the volume ratio of the organic amine compound to the 0.48 mol / L soluble rhodium salt aqueous solution is 0.6-6.0:1; preferably, the volume ratio is 4.0-6.0:1.

[0057] Furthermore, the mass fraction of the active metal rhodium is 0.06-0.2%; preferably, 0.06-0.1%; more preferably, 0.07-0.09%.

[0058] Furthermore, the mass ratio of the molecular sieve template to deionized water is 0.4-0.8:1; preferably, the mass ratio is 0.5-0.6:1.

[0059] Furthermore, in step 1, the stirring time is 5 to 15 minutes; preferably, the stirring time is 5 to 10 minutes.

[0060] Furthermore, the stirring time in step 2 is 5 to 10 hours; preferably, the stirring time is 5 to 7 hours.

[0061] Furthermore, the stirring time in step 3 is 10 to 30 minutes; preferably, the stirring time is 15 to 25 minutes.

[0062] Furthermore, the oven temperature in step 4 is 140° C. to 200° C., preferably 165° C. to 190° C.; and the reaction time is 60 to 90 hours, preferably 70 to 80 hours.

[0063] Furthermore, the calcination temperature in step 5 is 500° C. to 700° C., preferably 500° C. to 600° C.; and the calcination time is 3 to 5 hours, preferably 4 to 5 hours.

[0064] The monoatom dispersed catalyst for preparing linear aldehydes from olefins provided by the present invention can be used in the preparation of high-value linear aldehydes by hydroformylation of C3-C18 α-olefins and their internal olefins (isomerization).

[0065] The specific operation of the olefin hydroformylation reaction is as follows: molecular sieve-encapsulated single-atom catalyst, olefin and solvent are added to a reactor equipped with a magnetic stirrer, carbon monoxide and hydrogen are introduced, and the reaction is carried out at the reaction pressure and reaction temperature.

[0066] Furthermore, the molecular sieve encapsulated single-atom catalyst is directly used in the reaction without the need for high-temperature preactivation in a hydrogen atmosphere.

[0067] Furthermore, the olefin is C4-C 18 One or a mixture of α-olefins and internal olefins.

[0068] Furthermore, the solvent is one or more of no solvent, target aldehyde product, toluene, xylene, 1,4-dioxane, tetrahydrofuran, methanol, ethanol, and isopropanol; preferably, the solvent is no solvent, target aldehyde product, toluene, and xylene; more preferably, no solvent or target aldehyde product.

[0069] Furthermore, the molar ratio of olefin to active metal rhodium is 100-1,000,000:1, preferably 200-400,000:1.

[0070] Furthermore, the molar ratio of carbon monoxide to hydrogen is 1 to 3:1; preferably the molar ratio is 1:1.

[0071] Furthermore, the reaction pressure is 0.5-5.0 MPa; preferably 1.0-4.0 MPa, more preferably 1.0 MPa, 2.0 MPa or 3.0 MPa.

[0072] Furthermore, the reaction temperature is 30-120°C; preferably 60-100°C, more preferably 60°C, 70°C, 80°C, 90°C or 100°C.

[0073] Example 1.

[0074] A single-atom dispersed catalyst for olefins to linear aldehydes (molecular sieve encapsulated single-atom catalyst Rh 0.07 K 0.79 -MFI), prepared from tetrapropylammonium hydroxide, tetraethyl orthosilicate, rhodium chloride, potassium hydroxide, ethylenediamine and deionized water.

[0075] The molecular sieve encapsulates the single-atom catalyst Rh x K y -MFI preparation method is: Step 1: Add 16.24 g of tetrapropylammonium hydroxide (40% aqueous solution) and 0.2 g of potassium hydroxide to 12 g of deionized water and stir at room temperature for 5 minutes.

[0076] Step 2: 8.24 g of tetraethyl orthosilicate was added to the above solution and stirred at room temperature for 6 h.

[0077] Step 3: Add 50 μL of 0.48 mol / L soluble rhodium salt aqueous solution and 300 μL of ethylenediamine to the above solution and stir at room temperature for 20 min.

[0078] Step 4: Place the above solution in an oven and bake at 180°C for 72 hours. After taking it out, separate the sample by centrifugation. Wash the sample with deionized water and ethanol and dry it at 70°C overnight to obtain a solid sample.

[0079] Step 5: calcining the solid sample at 550 ° C for 4 h to obtain the molecular sieve encapsulated single atom catalyst Rh 0.07 K 0.79 -MFI.

[0080] Molecular sieve encapsulated single atom catalyst Rh 0.07 K 0.79 -MFI has a rhodium mass fraction of 0.07%, a potassium mass fraction of 0.79%, and a K / rhodium ratio of 11.29 (data obtained by ICP analysis).

[0081] Example 2.

[0082] According to the preparation method in Example 1, the mass of potassium hydroxide in step 1 was adjusted to 0.1 g to prepare Rh 0.08 K 0.74 -The mass fraction of rhodium in MFI is 0.08%, the mass fraction of potassium is 0.5%, and the K / rhodium ratio is 6.25.

[0083] Comparative Example 1.

[0084] According to the preparation method in Example 1, the 0.48 mol / L soluble rhodium salt aqueous solution in step 3 was adjusted to 150 μL to prepare Rh 0.15 K 0.76 -The mass fraction of rhodium in MFI is 0.15%, the mass fraction of potassium is 0.76%, and the K / rhodium ratio is 5.07.

[0085] Comparative Example 2.

[0086] According to the preparation method in Example 1, the rhodium loading was increased to prepare the molecular sieve encapsulated nanocatalyst, and the 0.48 mol / L soluble rhodium salt aqueous solution in step 3 was adjusted to 300 μL to prepare Rh 0.13 K 0.58 -The mass fraction of rhodium in MFI is 0.13%, the mass fraction of potassium is 0.58%, and the K / rhodium ratio is 4.46.

[0087] Comparative Example 3.

[0088] According to the preparation method in Example 1, the rhodium loading was increased to prepare the molecular sieve encapsulated nanocatalyst, and the 0.48 mol / L soluble rhodium salt aqueous solution in step 3 was adjusted to 500 μL to prepare Rh 0.14 K 0.28 -The mass fraction of rhodium in MFI is 0.14%, the mass fraction of potassium is 0.28%, and the K / rhodium ratio is 2.00.

[0089] Comparative Example 4.

[0090] According to the preparation method in Example 1, the rhodium loading was increased to prepare the molecular sieve encapsulated nanocatalyst, and the 0.48 mol / L soluble rhodium salt aqueous solution in step 3 was adjusted to 500 μL without adding potassium hydroxide to prepare Rh 0.16 The mass fraction of rhodium in K0-MFI is 0.16%, the mass fraction of potassium is 0, and the K / rhodium ratio is 0.

[0091] Structural testing: The above molecular sieve encapsulates the single atom catalyst Rh x K y -MFI spectrum analysis, the spectrum is as follows Figure 1 shown.

[0092] Figure 1 (a) is the XRD diffraction pattern, which shows the formation of MFI zeolite structure. The XRD diffraction peak positions of all prepared samples are similar, and no other peaks appear, indicating that the introduction of potassium hydroxide and rhodium metal has no effect on the topological structure of MFI zeolite. No diffraction peaks of rhodium nanoparticles are seen, indicating that rhodium is highly dispersed in the zeolite channel. In addition, compared with other single-atom catalysts, Rh 0.07 K 0.8 -MFI exhibits significant diffraction peaks, indicating that the addition of a large amount of potassium hydroxide during the preparation process promotes the nucleation and growth of the molecular sieve, which is more conducive to the encapsulation of single-atom catalytic active centers.

[0093] The structural characteristics of the prepared samples were further analyzed by FTIR spectroscopy. Figure 1 (b) shows that the fundamental lattice vibration peaks of the molecular sieve are located between 1500 and 400 cm -1 Between 1236cm -1 The vibration peaks are the asymmetric stretching vibrations of the tetrahedral O-Si-O external connections, located at 1075 and 795 cm -1 The two vibration peaks belong to the Si-0-Si internal stretching vibration and external symmetric vibration, located at 689cm -1 The vibration peak at 551 cm belongs to the internal symmetric stretching vibration of the tetrahedron. -1 The vibration peak at is attributed to the five-membered ring five silicon structure; the comparison sample Rh x K0-MFI, sample Rh x K>0 -MFI was prepared by adding potassium hydroxide to promote the nucleation and growth of molecular sieves. It can be observed that the -1 and 1075cm -1 The vibration peaks at , confirm that the rhodium atoms are better embedded in the molecular sieve channels.

[0094] Encapsulating the single-atom catalyst Rh in molecular sieves x K y -MFI and increasing rhodium loading to prepare molecular sieve encapsulated nanocatalysts, and BET and EA test analysis were performed. The analysis results are shown in Table 1.

[0095] Table 1 BET and EA test results of the catalysts of various examples and comparative examples.

[0096] From Table 1, the catalyst Rh 0.07 K 0.79 -MFI, Rh 0.15 K 0.76 -MFI and Rh 0.08 K 0.74 -MFI results show that when the K mass fraction is close, the rhodium mass fraction increases within a certain range, and the specific surface area, pore volume and pore size all decrease, which indicates that excessive rhodium loading within a certain range may block the channels of the molecular sieve.

[0097] From Table 1, the catalyst Rh 0.15 K 0.76 -MFI, Rh 0.13 K 0.58 -MFI and Rh 0.14 K 0.28 -MFI results show that when the rhodium mass fraction is close, the K mass fraction increases within a certain range, and the specific surface area, pore volume and pore size all increase. This shows that the increase in K loading within a certain range is conducive to promoting nucleation and growth, thereby increasing the pore structure of the molecular sieve.

[0098] Figure 2 The molecular sieve encapsulated single atom catalyst Rh prepared in Example 1 of the present invention 0.07 K 0.79 - Characteristic spectrum of MFI. Figure 2 a shows the clear lattice of MFI-zeolite with channels of approximately 1.01 nm (d(101) = 1.01 nm). Figure 2be shows the single-atom dispersion of rhodium atoms in the zeolite pores, especially the high-angle annular dark-field transmission electron microscopy (HAADF-STEM) image, which proves the atomic dispersion of rhodium atoms in the form of bright spots. The calculated average size of rhodium atoms is about 0.2nm, which is smaller than the cross-channels of zeolite, indicating that the rhodium atoms are located inside the zeolite channels. Figure 2 bd).

[0099] Applications of olefin hydroformylation reaction: A stainless steel reactor was charged with catalyst and olefin. After connecting the gas lines and fully displacing the gases, a mixture of carbon monoxide and hydrogen (1:1) was introduced to the reactor to a specific pressure. The reactor was heated to the reaction temperature. After the reaction was complete, the reactor was cooled to room temperature and samples were taken for determination of substrate conversion and product selectivity using gas chromatography (GC). The results are shown in Table 2.

[0100] Table 2 Evaluation results of each catalyst for the linear hydroformylation reaction of representative olefins (isomerization).

[0101] The reaction conditions are as follows: solvent: xylene, catalyst: 60 mg, olefin: 1 mmol, CO / H2 (40 bar), 80°C, 12 h; decane is added as an internal standard; for the comparative example Rh-Xantphos, S / C = 600, 2 h.

[0102] From the results of 1-2 in Table 2, we can see that under the conditions of 40 bar synthesis gas, xylene was used as solvent and 1-octene was tested at 80°C. It was observed that the molecular sieve encapsulated single atom catalyst Rh 0.07 K 0.79 -MFI and Rh 0.08 K 0.74 -MFI exhibited excellent activity, chemical selectivity, and linear selectivity, with conversion rates ranging from 99.1% to 99.8%, chemical selectivity for aldehydes ranging from 70.0% to 70.5%, a ratio of linear aldehydes to branched aldehydes ranging from 22.8% to 42.9%, a TON per pass of 2430, and an average TOF of 202.5%. h-1 The chemical selectivity of 70.0% is mainly due to the fact that isomerization is much faster than the hydroformylation process. Therefore, in the experiment, it was observed that olefins were almost completely converted within the first three hours, while the chemical selectivity of aldehydes continued to increase with time.

[0103] From the results of No. 3-6 in Table 2, we can see that compared with the molecular sieve encapsulated single atom catalyst, the molecular sieve encapsulated nanocatalyst Rh 0.15 K 0.76 -MFI, Rh 0.13 K 0.58 -MFI, Rh0.14 K 0.28 -MFI and Rh 0.16 Under the same conditions, the activity of K0-MFI is basically the same or significantly reduced, while the chemical selectivity of aldehydes and the selectivity of linear aldehydes are significantly reduced. The conversion rate is between 63.1-99.9%, the chemical selectivity of aldehydes is between 28.0-68.3%, and the ratio of linear aldehydes to branched aldehydes is between 3.0-5.7.

[0104] From the results of No. 7 in Table 2, it can be seen that the industrial homogeneous catalyst Rh-Xantphos tested in comparison achieved similar average conversion numbers and linear aldehyde selectivity, demonstrating the high performance of the novel molecular sieve-encapsulated single-atom catalyst of the present invention.

[0105] From the results of No. 8-13 in Table 2, we can see that the new molecular sieve encapsulates the single atom catalyst Rh 0.07 K 0.79 -MFI can be applied to the efficient linear hydroformylation of 1-hexene, 1-heptene, 1-nonene, 1-decene, 1-undecene and 1-dodecene to produce high-value linear aldehydes, with conversion rates between 99.0-99.9%, aldehyde chemical selectivity between 68.2-75.3%, and the ratio of linear aldehydes to branched aldehydes between 42.0-53.9.

[0106] From the results of No. 14-17 in Table 2, we can see that the new molecular sieve encapsulates the single atom catalyst Rh 0.07 K 0.79 -MFI can be applied to the efficient isomerization linear hydroformylation of 2-octene, 3-octene, 4-octene and mixed C4s to produce high-value linear aldehydes, with a conversion rate of 90.0-99.9%, aldehyde chemical selectivity of 70.0-97.3%, and a ratio of linear aldehyde to branched aldehyde of 42.0-65.9.

[0107] The present invention does not describe in detail parts that belong to the common knowledge of those skilled in the art. The above-described embodiments are merely descriptions of preferred embodiments of the present invention. The preferred embodiments do not describe all details in detail, nor are they limited to the specific embodiments described. Without departing from the spirit of the present invention, various modifications and improvements made by those skilled in the art to the technical solution of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A molecular sieve encapsulated single atom dispersed catalyst for olefin to linear aldehyde production, characterized in that: The synthetic raw materials include molecular sieve template, silicon source, soluble rhodium salt, metal strong base compound, organic amine compound and deionized water.

2. The molecular sieve encapsulated monoatom dispersed catalyst for olefin to linear aldehyde production according to claim 1, characterized in that: The molecular sieve template is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, 1.8-octanediamine, tetrabutylammonium bromide or trioctylamine.

3. The molecular sieve encapsulated monoatom dispersed catalyst for olefin to linear aldehyde production according to claim 1, characterized in that: The silicon source is one or more combinations of tetraethyl orthosilicate, tetrapropyl orthosilicate, tetrabutyl orthosilicate, sodium silicate, sodium metasilicate or methyl orthosilicate; and the soluble rhodium salt is rhodium chloride, rhodium nitrate or rhodium sulfate.

4. The molecular sieve encapsulated monoatom dispersed catalyst for olefin to linear aldehyde production according to claim 1, characterized in that: The metal strong base compound is one or more combinations of potassium hydroxide, sodium hydroxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate or potassium carbonate; the organic amine compound is one or more combinations of ethylenediamine, N,N'-dimethylethylenediamine, N,N'-tetramethylethylenediamine, 1,2-cyclohexanediamine, dimethylamine, diethylamine, trimethylamine, triethylamine, triethanolamine, ethanolamine or propanolamine.

5. A method for preparing a molecular sieve-encapsulated monoatom-dispersed catalyst for olefin-to-linear aldehyde conversion, characterized in that: The steps include: Step 1: adding a molecular sieve template and a metal base compound to deionized water and stirring at room temperature to obtain a solution 1; Step 2: adding a silicon source to solution 1 and stirring at room temperature to obtain solution 2; Step 3, adding 0.48 mol / L soluble rhodium salt aqueous solution and organic amine compound to solution 2, and stirring at room temperature to obtain solution 3; Step 4: Transfer solution 3 to a hydrothermal synthesis reactor, place it in an oven for high-temperature reaction for a period of time, take it out and separate the solid sample by centrifugation, wash the sample with deionized water and ethanol, and dry it at 70°C overnight to obtain a dry solid sample; Step 5: calcining the dried solid sample at high temperature in an air atmosphere to obtain a monoatom-dispersed catalyst for preparing linear aldehydes from olefins.

6. The method for preparing a molecular sieve-encapsulated monoatom-dispersed catalyst for preparing linear aldehydes from olefins according to claim 5, characterized in that: The mass fraction of the strong base corresponding to the metal is 0~1.0%; the molar ratio of the metal strong base compound to the silicon source is 0.04~0.15:1; the molar ratio of the molecular sieve template to the silicon source is 0.2~1.0:1; the molar ratio of the soluble rhodium salt to the silicon source is 0.0005~0.0065:1; the volume ratio of the organic amine compound and the 0.48moL / L soluble rhodium salt aqueous solution is 0.6~6.0:1; the mass fraction of the active metal rhodium is 0.06~0.2%; the mass ratio of the molecular sieve template to the deionized water is 0.4~0.8:

1.

7. The method for preparing a molecular sieve-encapsulated monoatom-dispersed catalyst for preparing linear aldehydes from olefins according to claim 5, characterized in that: In step 1, the stirring time is 5 to 15 minutes; in step 2, the stirring time is 5 to 10 hours; in step 3, the stirring time is 10 to 30 minutes.

8. The method for preparing a molecular sieve-encapsulated monoatom-dispersed catalyst for preparing linear aldehydes from olefins according to claim 5, characterized in that: In step 4, the oven temperature is 140° C. to 200° C., and the reaction time is 60 to 90 hours; in step 5, the calcination temperature is 500° C. to 700° C., and the calcination time is 3 to 5 hours.

9. Use of a molecular sieve-encapsulated monoatom-dispersed catalyst for preparing linear aldehydes from olefins according to any one of claims 1 to 4, characterized in that: The catalyst is used in the preparation of high-value linear aldehydes by hydroformylation of C3-C18 alpha-olefins and internal olefins.

10. The use of a molecular sieve encapsulated monoatom dispersed catalyst for preparing linear aldehydes from olefins according to claim 9, characterized in that: The specific operation of the olefin hydroformylation reaction is as follows: molecular sieve-encapsulated single-atom catalyst, olefin and solvent are added to a reactor equipped with a magnetic stirrer, carbon monoxide and hydrogen are introduced, and the reaction is carried out at the reaction pressure and reaction temperature; The molar ratio of olefin to active metal rhodium is 100-1,000,000:1; the molar ratio of carbon monoxide to hydrogen is 1-3:1; the reaction pressure is 0.5-5.0 MPa; and the reaction temperature is 30-120°C.

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