Preparation of a heterogeneous pd catalyst and method for the production of esters by olefin alkoxycarbonylation
By preparing heterogeneous Pd catalysts carrying phosphine coordination sites and steric hindrance, the problems of catalyst stability and recovery in olefin alkoxycarbonylation were solved, realizing efficient alkoxycarbonylation reaction and stable recycling of catalysts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV
- Filing Date
- 2026-02-26
- Publication Date
- 2026-06-12
AI Technical Summary
Existing olefin alkoxycarbonylation catalysts suffer from difficulties in metal leaching and recovery, and heterogeneous catalysts have low activity, making them unsuitable for the synthesis of high-boiling-point products.
A heterogeneous Pd catalyst with abundant phosphine coordination sites and steric hindrance was prepared by coordination polymerization of phosphine ligands with inorganic zirconium salts under hydrothermal conditions, forming Pd-L1-LCP and Pd-L2-LCP catalysts for olefin alkoxycarbonylation reactions.
It achieves highly efficient alkoxycarbonylation reaction activity and catalyst stability, can be easily recycled and reused, reduces separation energy consumption, and avoids Pd sintering deactivation at high temperatures.
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Figure CN122188166A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of industrial catalysis, specifically to a method for preparing and using a heterogeneous Pd catalyst for olefin alkoxycarbonylation. Background Technology
[0002] Ester compounds are widely used in fine chemical industries such as detergents, plasticizers, pharmaceuticals, and pesticides. Alkoxycarbonylation of olefins is an important method for preparing ester compounds, offering very high atom economy. Globally, tens of millions of tons of ester compounds are produced annually using this process.
[0003] Currently, the key technical challenge in the alkoxycarbonylation process of olefins lies in how to construct efficient and stable transition metal catalysts (Rh, Pd, etc.). As early as the 1990s, William et al. (Chem. Commu., 1999, 31, 1877-1878) reported Pd2(dba)3 / d t The bpx[1,2-bis(di-tert-butylphosphine)o-xylene] / MAS (methanesulfonic acid) catalytic system not only achieved high activity in the ethylene alkoxycarbonylation reaction but also exhibited a selectivity of up to 99% for methyl propionate. Subsequently, researchers systematically optimized and modified this type of phosphine ligand, continuously constructing novel ligands to modify transition metals and enhance their alkoxycarbonylation reactivity. For example, patents CN120040504A, CN114644652A, and CN114308129A synthesized a series of complex phosphine ligands that significantly improved the activity of transition metal Pd catalysts. A series of bidentate phosphine ligands with tert-butyl functional groups (Chem. Sci., 2018, 9, 2510; Nat. Commun., 2017, 8, 14117; Science, 2019, 366, 1514-151) also achieved relatively excellent reactivity. Furthermore, patent CN114835746 synthesized a benzene-based tetradentate phosphine ligand carrying a tert-butyl functional group and complexing it with metal Pd, achieving a methyl propionate selectivity of up to 99.9% in the alkoxycarbonylation of ethylene. However, the phosphine ligand synthesis routes used above are complex, costly, and extremely unstable, being sensitive to air and heat. For short-chain olefins, the corresponding ester products have low boiling points, and the catalyst can be separated by distillation. However, for the synthesis of some high-boiling-point esters, the separation of the product from the catalyst is energy-intensive, and the metal is extremely prone to leaching at high temperatures, leading to catalyst deactivation and making recovery and reuse difficult. This greatly limits the continued advancement of industrial applications.
[0004] To improve catalyst stability and recyclability, heterogeneous catalyst construction is essential. Some studies have attempted to anchor the transition metal Pd using inorganic molecular sieves or resins. However, these supports lack the electronic and steric effects found in phosphine ligands, resulting in low olefin conversion rates. For example, the MCM-41 support, after Pd loading, exhibited only 78% conversion in the alkoxycarbonylation of hexene and methanol (Catalysts, 2019, 143, 1-16); Pd catalysts supported on activated carbon and magnetic iron oxide only achieved 81%-83% olefin conversion (Molecular Catalysis, 2020, 484, 110742). Furthermore, these catalysts still cannot prevent the formation and leaching of Pd atom clusters.
[0005] Therefore, in order to solve the problems of metal leaching, difficult recovery, and low activity of heterogeneous catalysts, it is necessary to construct an alkoxycarbonylation transition metal catalyst with abundant coordination sites and steric hindrance, and capable of stable recycling. Summary of the Invention
[0006] The present invention aims to develop a method for preparing a highly efficient, stable heterogeneous catalyst for olefin alkoxycarbonylation that carries abundant phosphine coordination sites and has certain steric hindrance, and successfully apply it to the alkoxycarbonylation reaction of olefins, exhibiting high reactivity and good cycle stability.
[0007] In order to achieve the objective of this invention, the following technical solution is adopted:
[0008]
[0009] This invention provides a Pd heterogeneous catalyst (Pd-L1-LCP, Pd-L2-LCP) for alkoxycarbonylation of olefins. The synthetic route of this catalyst is shown in the figure below. First, phosphine ligands (L1, L2) with carboxyl functional groups are coordinated and complexed with Pd salt catalyst precursors to obtain catalyst monomers. Where X represents the anion of different Pd salt precursors (anions include Cl-). - CH3COO - I - L represents a phosphine ligand L1 or L2 carrying a carboxyl functional group. The ligand is then prepared by coordination polymerization of the carboxyl functional group on the phosphine ligand with an inorganic zirconium salt in a hydrothermal reactor with the assistance of a protic acid.
[0010] Under the conditions of the heterogeneous Pd catalyst, alkoxycarbonylation was carried out using olefins, carbon monoxide, and primary alcohols as raw materials, and strong organic or inorganic acids as additives, at specific temperatures and pressures. The results showed that the prepared heterogeneous Pd catalyst exhibited excellent alkoxycarbonylation activity, with carbonylation product yields exceeding 95% and selectivity >97%. The basic reaction formula for alkoxycarbonylation is as follows:
[0011]
[0012] In the heterogeneous Pd catalyst synthesized in this invention, preferably, the molar ratio (Pd:L) of Pd to phosphine ligand (L1 or L2) is 0.001:1 to 1:1.
[0013] In the heterogeneous Pd catalyst synthesized in this invention, the preferred protic acid used is acetic acid, trifluoromethanesulfonic acid, benzoic acid, or formic acid.
[0014] In the heterogeneous Pd catalyst synthesized in this invention, preferably, the inorganic zirconium salt used is anhydrous zirconium tetrachloride and zirconium oxychloride octahydrate.
[0015] In the heterogeneous Pd catalyst synthesized in this invention, preferably, the metal Pd salt used is palladium chloride, palladium acetate, or palladium iodide.
[0016] In the heterogeneous Pd catalyst synthesized in this invention, preferably, the hydrothermal synthesis temperature is 100℃-160℃, and the hydrothermal coordination polymerization synthesis time is 8h-24h.
[0017] In the olefin alkoxycarbonylation reaction implemented in this invention, preferably, the reaction temperature is 80℃-140℃ and the reaction pressure is 1MPa-5MPa, wherein the ratio of the amount of Pd atoms in the heterogeneous Pd catalyst to the amount of olefin is Pd:olefin = 0.0001:1-0.01:1.
[0018] In the olefin alkoxycarbonylation reaction implemented in this invention, preferably, the organic or inorganic strong acid used is sulfuric acid, hydrochloric acid, formic acid, or p-toluenesulfonic acid, and the ratio of the amount of the acid used to the amount of Pd atoms is 1:1 to 1:100.
[0019] The beneficial effects of the present invention are as follows: (1) Compared with the homogeneous Pd catalysts that are widely used in the current olefin alkoxycarbonylation reaction, the present invention introduces heterogeneous Pd catalysts carrying abundant phosphine coordination sites and having certain steric hindrance. Under the premise of ensuring the activity of the precursor of olefin alkoxycarbonylation reaction, the catalyst is made heterogeneous, making the catalytic system of the present invention particularly suitable for the synthesis of high-boiling-point products. The obtained catalyst can be recovered and reused through simple phase separation. While reducing the separation energy consumption, it can effectively avoid the deactivation of Pd by sintering at high temperature.
[0020] (2) Compared with the heterogeneous Pd catalysts that have been reported for the alkoxycarbonylation reaction of olefins, the present invention retains the strong coordination sites of phosphine through the heterogeneity of phosphine ligands. Due to the presence of strong Pd-P coordination, Pd is not easily lost during the use of the catalyst, which is beneficial to maintaining the stability of the catalyst. Attached Figure Description
[0021] Figure 1 The preparation process of the catalyst developed in this invention is described below.
[0022] Figure 2 The XPS spectrum of the catalyst developed in this invention shows characteristic signal peaks of elements such as C, O, P, Cl, and Pd.
[0023] Figure 3 The XRD patterns of the catalysts developed in this invention show that the catalyst composed of L1 has obvious characteristic signal peaks at 2θ = 7° and 2θ = 22°, and the catalyst composed of L1 has obvious characteristic signal peaks at 2θ = 5° and 2θ = 8°.
[0024] Figure 4 The image shows a scanning electron microscope (SEM) image of the catalyst developed in this invention. The catalyst composed of L1 has a honeycomb spherical morphology, while the catalyst composed of L2 has a regular flower-like morphology.
[0025] Figure 5 The gas chromatogram shows the heterogeneous Pd catalyst developed in this invention applied to the alkoxycarbonylation reaction of ethylene and methanol. Detailed Implementation Plan
[0026] The present invention will be further described in detail below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Any variations or implementations are included within the technical scope of the present invention without departing from the scope of the preceding and following spirit.
[0027] Example 1
[0028] Synthesis of Pd-L1-LCP(a1): 0.1 g of phosphine ligand L1 and 10 mg of palladium chloride were placed in the lining of a clean hydrothermal reactor. Then, 15 mL of N,N-dimethylformamide was added to dissolve the contents at room temperature and stirred for 2 h. 118 mg of anhydrous zirconium tetrachloride and 0.31 g of benzoic acid were added. The mixture was then sealed and placed in an oven at 120 °C for hydrothermal coordination polymerization for 24 h. After the reaction was completed, the mixture was filtered and washed to obtain a yellow powdery heterogeneous Pd catalyst, denoted as Pd-L1-LCP(a1), with a yield of 60%.
[0029] Example 2:
[0030] Synthesis of Pd-L2-LC(b1): The specific operation steps are similar to those in Example 1. Phosphine ligand L2 and palladium chloride were loaded into the lining of a clean hydrothermal reactor. Then, N,N-dimethylformamide was added to dissolve the mixture at room temperature and stirred for 2 hours. Anhydrous zirconium tetrachloride and benzoic acid were added. The mixture was then sealed and placed in an oven at 120°C for hydrothermal coordination polymerization for 24 hours. After the reaction was completed, the mixture was filtered and washed to obtain a yellow powdery heterogeneous Pd catalyst, denoted as Pd-L1-LCP(b1), with a yield of 70%.
[0031] Examples 3-6:
[0032] Example catalyst Pd source Phosphine ligand Catalyst yield 3 Pd-L1-LCP(a2) Palladium acetate L1 62％ 4 Pd-L2-LCP(b2) Palladium acetate L2 69％ 5 Pd-L1-LCP(a3) Palladium iodide L1 58％ 6 Pd-L2-LCP(b3) Palladium iodide L2 73％
[0033] Examples 7-9
[0034] Example catalyst protic acid Phosphine ligand Catalyst yield 7 Pd-L1-LCP(a1-1) acetic acid L1 48％ 8 Pd-L1-LCP(a1-2) Formic acid L1 66％ 9 Pd-L1-LCP(a1-3) Trifluoromethanesulfonic acid L1 57％
[0035] Example 10
[0036] Synthesis of Pd-L1-LCP(a1'): The specific operating steps are the same as in Example 1, except that zirconium tetrachloride is replaced with zirconium oxychloride. Phosphine ligand L1 and palladium chloride are placed in the lining of a clean hydrothermal reactor. N,N-dimethylformamide is then added to dissolve the mixture at room temperature and stirred for 2 hours. Zirconium oxychloride and benzoic acid are then added. The reactor is sealed and placed in an oven at 120°C for hydrothermal coordination polymerization for 24 hours. After the reaction is complete, the mixture is filtered and washed to obtain a yellow powdery heterogeneous Pd catalyst, denoted as Pd-L1-LCP(a1'), with a yield of 75%.
[0037] Example 11:
[0038] Alkoxycarbonylation of ethylene and methanol: In a high-pressure reactor equipped with a magnetic stirrer, 10 mg of heterogeneous Pd catalyst Pd-L1-LCP(a1), 15 mL of methanol, and 20 mg of p-toluenesulfonic acid were added. Ethylene at 2.5 bar and carbon monoxide at 2 MPa were then introduced sequentially, and the reaction was carried out at 120 °C for 12 h. After the reaction was completed, the reactor was cooled to room temperature, and the catalyst was recovered by centrifugation. The supernatant was analyzed by gas chromatography using an internal standard (trimethylbenzene). According to the gas chromatography results, the conversion rate of ethylene was 98%, and the selectivity of the carbonylation product was 99%.
[0039] Examples 12-16:
[0040] Other operating conditions are the same as in Example 11, except that the reaction temperature is changed.
[0041] Example Reaction temperature (°C) Ethylene conversion rate (%) Carbonyl product selectivity (%) 12 100 90 97 13 110 92 98 14 130 97 98 15 140 95 96 16 160 89 95
[0042] Examples 17-20
[0043] Other operating conditions are the same as in Example 11, except that the reaction pressure is changed.
[0044] Example Reaction pressure (MPa) Ethylene conversion rate (%) Carbonyl product selectivity (%) 17 1 91 97 18 3 98 97 19 4 98 98 20 5 98 97
[0045] Examples 21-23
[0046] Other operating conditions are the same as in Example 11, except that the types of organic and inorganic strong acids are changed.
[0047] Example protic acid Ethylene conversion rate (%) Carbonyl product selectivity (%) 21 sulfuric acid 85 96 22 hydrochloric acid 93 94 23 Formic acid 96 97
[0048] Examples 24-27
[0049] Other operating conditions are the same as in Example 11, except that the type of olefin substrate is changed.
[0050] Example Olefins Olefin conversion rate (%) Carbonyl product selectivity (%) 24 Cyclohexene 97 98 25 Hexene 96 97 26 styrene 95 96
[0051] Examples 27-29
[0052] Other operating conditions are the same as in Example 11, except that the type of primary alcohol substrate is changed.
[0053] Example Primary alcohols Ethylene conversion rate (%) Carbonyl product selectivity (%) 27 ethanol 96 97 28 Butanol 95 97 29 Hexanol 95 98
[0054] Example 30
[0055] Other operating conditions are the same as in Example 11. After the reaction is completed, the catalyst is recovered by centrifugation, and fresh raw materials and additives are added and put back into the reaction.
[0056] Number of recyclings Ethylene conversion rate (%) Carbonyl product selectivity (%) 1 98 99 2 97 98 3 98 98 4 97 98
Claims
1. A method for preparing a heterogeneous Pd catalyst and its use in the alkoxycarbonylation of olefins to produce esters, characterized in that, A heterogeneous Pd catalyst containing Pd atoms is obtained by first coordinating phosphine ligands L1 or L2 with metallic Pd in solution to form a complex, and then coordinating with an inorganic zirconium salt under hydrothermal conditions with the assistance of a protic acid. This catalyst can be applied to the alkoxycarbonylation of olefins, carbon monoxide, and primary alcohols.
2. The method according to claim 1, characterized in that... The structural formula of the heterogeneous Pd catalyst is shown in the figure below (where X represents the anion of the palladium salt):
3. The catalyst preparation method according to claim 1, characterized in that... The molar ratio of Pd to phosphine ligands (L1 or L2) (Pd:L) is 0.001:1 to 1:
1.
4. The catalyst preparation method according to claim 1, characterized in that... The protic acids used are acetic acid, trifluoromethanesulfonic acid, benzoic acid, and formic acid.
5. The method for preparing the catalyst according to claim 1, characterized in that... The inorganic zirconium salts used are anhydrous zirconium tetrachloride and zirconium oxychloride octahydrate.
6. The catalyst preparation method according to claim 1, characterized in that... The metal Pd salts used are palladium chloride, palladium acetate, and palladium iodide.
7. The catalyst preparation method according to claim 1, characterized in that... The hydrothermal synthesis temperature is 100℃-160℃, and the synthesis time for hydrothermal coordination polymerization is 8h-24h.
8. The method of using the catalyst according to claim 1, characterized in that, Under the condition of the heterogeneous Pd catalyst, olefins, primary alcohols and organic and inorganic strong acid additives are added, and CO gas is introduced to carry out the catalytic reaction.
9. The method according to claim 8, characterized in that, The catalyst has a reaction temperature of 80℃-140℃ and a reaction pressure of 1MPa-5MPa. The ratio of the amount of Pd atoms in the heterogeneous Pd catalyst to the amount of olefins is Pd:olefin = 0.0001-0.
01.
10. The method according to claim 8, characterized in that, The organic and inorganic strong acids used are sulfuric acid, hydrochloric acid, formic acid, and p-toluenesulfonic acid, and the ratio of the amount of these acids to the amount of Pd atoms is 1:1 to 1:100.