Method for preparing propionate through ethylene hydrogen esterification reaction

Abstract

The invention discloses a method for preparing propionate through ethylene hydrogen esterification reaction, which is characterized in that raw materials ethylene, carbon monoxide and low-carbon alcohol are subjected to hydrogen esterification reaction in the presence of a catalyst by taking propionate as a solvent to synthesize propionate, the catalyst is composed of a palladium compound, a naphthyl bidentate phosphine ligand and an acidic auxiliary agent, and the structure of the naphthyl bidentate phosphine ligand is shown in the following formula. Wherein m is 0 or 1, and n is 1 or 2; r1 is selected from phenyl, tertiary butyl, cyclohexyl, 2-pyridyl, 2-thienyl or 2-furyl, and R2 is selected from tertiary butyl, cyclohexyl, 2-pyridyl, 2-thienyl or 2-furyl. According to the method, the naphthyl bidentate phosphine is used as the ligand, the product propionate is used as the reaction solvent, the catalyst activity is high, the yield of the target product propionate is high, and byproducts are few.

Description

Technical Field

[0001] This invention belongs to the field of propionate synthesis technology, and relates to a method for preparing propionate by ethylene hydrogen esterification reaction. Background Technology

[0002] Methyl propionate and other propionate esters are important organic chemical raw materials, widely used in fragrances, lithium battery manufacturing, organic solvents, and organic synthesis. In the fragrance industry, methyl propionate is a commonly used food additive that significantly enhances and improves food flavor while also acting as a preservative. In the lithium battery industry, methyl propionate is an important electrolyte additive, characterized by high safety, good chemical and electrochemical stability, a wide liquid temperature range, environmental friendliness, and low viscosity. It effectively lowers the freezing point and viscosity of the electrolyte, improving the charge and discharge power of lithium batteries. In the organic solvent industry, methyl propionate can dissolve phenolic resins, nitrocellulose, vinyl resins, shellac resins, etc. Due to its strong solubility in oils and fats, it is often used as a solvent for coatings, paints, and nitrocellulose lacquer. In the organic synthesis industry, methyl propionate is a key intermediate for many downstream products, such as benzoyl propionate, 2-methyl-3-pentanone, and methyl methacrylate (MMA). Its most important application is the synthesis of MMA.

[0003] The production processes of methyl propionate include propionic esterification, hydrogenation of methyl acrylate, propanol / propionaldehyde oxidation, methoxycarbonylation of ethylene and methyl formate, and hydrogen esterification of ethylene, carbon monoxide, and methanol. Among these, the ethylene hydrogen esterification method has advantages such as abundant and inexpensive raw materials, simple process, compliance with atom economy, and no by-product generation, which reduces environmental pollution.

[0004] The hydrogen esterification of ethylene to propionate is an important industrial reaction. Catalysis of this reaction usually requires a catalyst system consisting of a palladium compound, an organophosphorus ligand, and an acidic catalyst. The electronic and steric properties of the organophosphorus ligand synergistically influence each step of the catalytic reaction, playing a key role in enabling palladium to efficiently catalyze the hydrogen esterification reaction.

[0005] Currently, patent documents have publicly reported related phosphine ligands such as alkylphosphine ligands, cycloalkylphosphine ligands, or bidentate phosphine ligands, such as US2005085671A1, US2001051745A1, US6476255B1, EPA0499329, EPA0495547, and EPA04489472. In particular, Lucite Company disclosed bidentate phosphine compounds based on substituted aryl bridges, such as dtbpx, i.e., 1,2-bis(di-tert-butylphosphinomethyl)benzene, which can improve conversion and reaction rate compared to previously disclosed ligands (Chem. Commun., 1999, 1877-1878; WO96 / 19434; WO2004 / 014552A1). Later, it developed bidentate phosphine ligand butphos, i.e., 2-bis(di-tert-butylphosphinomethyl)ferrocene, based on a ferrocene skeleton (Inorg. Chem. Commun., 2004, 1049-1052; CN104011007B). Evonik Degussa has disclosed ferrocene-based diphosphine ligands such as 1,1'-bis(tert-butylphenylphosphino)-ferrocene (Angew. Chem. Int. Ed., 2017, 56(19), 5267-5271; US2017 / 0022234A1) and benzene-based α,α'-bis(2-pyridyl(tert-butyl)phosphino)o-xylene (US6335471B1; CN106366126A), which exhibit better ester yields, lower isomerization, and fewer byproducts. These ligands are currently the most efficient ligands in olefin hydrogen esterification reactions, exhibiting excellent performance in hydrogen esterification reactions. In addition, Guangdong Oukai New Materials Co., Ltd. has disclosed polyphosphine ligands based on benzene skeletons for catalyzing the preparation of methyl propionate from ethylene in dry gas, with excellent catalytic effects (CN102531890A). The Lanzhou Institute of Chemical Physics has disclosed a method for preparing organic carboxylic acid esters based on aryl bidentate phosphine ligand combination catalysts, which easily forms the most spatially favorable coordination mode and a relatively stable active structure (CN111087306B). Shanghai Pujing Chemical Co., Ltd. has also disclosed a method for preparing organic carboxylic acid esters based on oxanthracene or oxanthracene-like skeletons, together with auxiliary phosphine ligands. The synergistic effect of the two ligands further improves the stability of the catalyst and extends its lifetime (CN115957823A).

[0006] Although the phosphine ligands disclosed in the above patents exhibit good performance in the ethylene hydrogen esterification reaction, the phosphine ligands used have drawbacks such as complicated production processes, high costs, and instability in air. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing propionate by ethylene hydrogen esterification reaction. Naphthyl bidentate phosphine is selected as the phosphine ligand in the palladium phosphine catalytic system, which can overcome the defects of poor stability and short service life of existing palladium phosphine catalytic systems, and develop an ethylene hydrogen esterification process with simple synthesis route, low production cost and excellent catalytic performance.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing propionate ester by ethylene hydrogen esterification reaction, characterized in that ethylene, carbon monoxide, and a lower alcohol are reacted in the presence of a catalyst, using the target product propionate ester as a solvent, to synthesize propionate ester; the catalyst is composed of a palladium compound / naphthyl bidentate phosphine ligand / acidic auxiliary, and the structure of the naphthyl bidentate phosphine ligand is as follows:

[0010]

[0011] Where m is 0 or 1, n is 1 or 2; R1 is selected from phenyl, tert-butyl, cyclohexyl, 2-pyridyl, 2-thienyl or 2-furanyl, and R2 is selected from tert-butyl, cyclohexyl, 2-pyridyl, 2-thienyl or 2-furanyl.

[0012] Furthermore, in the naphthyl bidentate phosphine ligand structure, m = 0, n = 1, R1 is selected from phenyl, tert-butyl, cyclohexyl, 2-pyridyl, 2-thienyl or 2-furanyl, and R2 is selected from tert-butyl or cyclohexyl.

[0013] Preferably, the naphthyl bidentate phosphine ligand has one of the following structural formulas:

[0014]

[0015] Furthermore, the lower alcohol is a C1-C6 monohydric saturated alcohol, selected from methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, and cyclohexanol, preferably methanol, ethanol, 1-propanol, and 1-butanol.

[0016] Further, the propionate is one of methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, hexyl propionate, isopropyl propionate, tert-butyl propionate, 3-pentyl propionate, and cyclohexyl propionate, preferably methyl propionate, ethyl propionate, propyl propionate, or butyl propionate.

[0017] Further, the palladium compound is one or more of palladium nitrate, palladium acetate, palladium acetylacetonate, palladium trifluoroacetate, palladium iodide, palladium chloride, bis(triphenylphosphine)palladium dichloride, allyl palladium chloride, tetra(triphenylphosphine)palladium, bis(dibenzylideneacetone)palladium, tri(dibenzylideneacetone)palladium, and 1,5-cyclooctadiene palladium dichloride, preferably palladium acetate, palladium acetylacetonate, or palladium chloride.

[0018] Furthermore, the acidic additive is selected from one or more of hydrochloric acid, sulfuric acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, tert-butylsulfonic acid, boric acid, or salicylic acid, preferably methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, or tert-butylsulfonic acid, and more preferably tert-butylsulfonic acid or p-toluenesulfonic acid.

[0019] Further, the molar ratio of the naphthyl bidentate phosphine ligand to the palladium compound is (1-20):1, preferably (5-15):1; the molar ratio of the acidic auxiliary agent to the palladium compound is (0.5-20):1, preferably (3-15):1.

[0020] Furthermore, based on the total mass of the reaction system, the mass concentration of palladium in the palladium compound is 50–1000 ppm, preferably 100–300 ppm.

[0021] Furthermore, the molar ratio of the raw materials ethylene, carbon monoxide and lower alcohols is (0.5-5):1:(1-5), preferably (0.5-2):1:(1.5-3).

[0022] Furthermore, the molar ratio of the lower alcohol to the propionate is 1:(1-30), preferably 1:(1-10).

[0023] Furthermore, the reaction temperature of the ethylene hydrogen esterification reaction is 60–140°C, preferably 80–120°C; the reaction pressure is 0.5–5.0 MPa, preferably 1–4 MPa; and the reaction time is 0.5–4 h, preferably 0.5–2 h.

[0024] Beneficial effects: The method for preparing propionate by the hydrogen esterification reaction of ethylene according to the present invention, using naphthyl bidentate phosphine as the catalyst ligand and the product propionate as the reaction solvent, has the advantages of high catalyst activity, high yield of the target product propionate, few by-products, and simple and efficient process, specifically including:

[0025] 1. The present invention uses a catalyst system containing naphthyl bidentate phosphine ligands. The naphthyl bidentate phosphine ligands work synergistically with palladium compounds and acidic auxiliaries. The ligand structure helps to form a stable active center, promoting the efficient conversion of ethylene, carbon monoxide and lower alcohols into propionate esters.

[0026] 2. Compared with commonly used phosphine ligands (such as alkylphosphine, cycloalkylphosphine or ferrocene skeleton ligands), the naphthyl bidentate phosphine ligand of the present invention can significantly enhance the antioxidant capacity of phosphorus atoms and the decomposition resistance of complexes, reduce the risk of catalyst deactivation, overcome the shortcomings of poor stability and short service life of existing palladium phosphine catalytic systems, and extend the catalyst's recycling cycle.

[0027] 3. The synthesis process of the naphthyl bidentate phosphine ligand of the present invention is relatively simple, the raw materials are readily available, and no complicated purification steps are required, which significantly reduces the production cost and makes it more suitable for large-scale industrial applications.

[0028] 4. The naphthyl bidentate phosphine ligand of the present invention has good planar rigidity, which can avoid ligand conformational inversion, lock the ligand conformation, ensure the specific coordination mode of the catalytic species, effectively suppress isomerization and other side reactions, thereby improving the purity and yield of the target product propionate.

[0029] 5. The ligands of this invention are applicable to a variety of low-carbon alcohols (such as methanol, ethanol, etc.) and propionate solvents, and have a wide range of substrate applicability and reaction condition adaptability, which enhances the versatility and industrial feasibility of the method. Detailed Implementation

[0030] The following detailed embodiments illustrate the implementation process and beneficial effects of the present invention, aiming to better understand the essence and characteristics of the present invention, and are not intended to limit the present invention.

[0031] In the following examples, the chromatographic analysis conditions for the products were as follows: All samples were quantitatively analyzed using a Shimadzu 7980 gas chromatograph, with the internal standard method used. An Agilent HP-5 column (30m × 0.32mm × 0.25um) was used. The chromatographic detection conditions were: vaporization chamber temperature 250℃, flame ionization detector (FID) temperature 250℃, high-purity nitrogen as the carrier gas at a constant flow rate of 2mL / min, and air and high-purity hydrogen flow rates of 200mL / min and 30mL / min, respectively, in the FID detector. The column oven temperature was programmed, held at 45℃ for 2 minutes, and then increased to 160℃ at a rate of 10℃ / min.

[0032] CO is used as the basis for calculating propionate yield: Propionate yield = molar amount of propionate produced / molar amount of CO introduced * 100%.

[0033] In the following examples, the naphthyl bidentate phosphine ligand was prepared by the following method: Under inert gas protection, aryl trifluoromethanesulfonate precursor (Ⅰ), base, palladium catalyst, 1,1'-bis(diphenylphosphine)ferrocene and solvent were added to a reaction vessel, followed by the addition of chlorinated organophosphine (Ⅱ), and the reaction was stirred at a certain temperature. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, concentrated under reduced pressure, and separated by silica gel column chromatography to obtain the desired naphthyl bidentate phosphine compound.

[0034]

[0035] Example 1

[0036] (1) Preparation of naphthyl bidentate phosphine ligand: bis[2-(tert-butylphenylphosphino)-1-naphthyl]methane (L2), the specific steps are as follows:

[0037] Under an argon atmosphere, bis(2-trifluoromethanesulfonyl-naphthyl)methane (778.4 mg, 1.38 mmol), sodium tert-butoxide (200.0 mg, 2.8 mmol), palladium acetate (16.0 mg, 0.072 mmol), 1,1'-bis(diphenylphosphine)ferrocene (40.0 mg, 0.072 mmol), 8 mL of toluene, and chloro(tert-butyl)phenylphosphine (561.8 mg, 2.8 mmol) were sequentially added to a 100 mL Shrek flask. After reacting at 110 °C for 12 hours, the reaction was stopped and cooled to room temperature. The reaction mixture was filtered through diatomaceous earth and washed with dichloromethane. The crude product was concentrated under reduced pressure and separated by silica gel column chromatography to obtain 543.5 mg of bis[2-(tert-butylphenylphosphine)-1-naphthyl]methane, in 66% yield.

[0038] 1 H NMR (400MHz, CDCl3) δ = 7.97 (ddt, J = 9.2, 7.5, 1.6Hz, 2H), 7.95-7.87 (m, 2H), 7.82 (ddd, J = 14.8, 7.5, 1.5 Hz,2H),7.68-7.54(m,6H),7.44-7.34(m,6H),7.38-7.23(m,4H),4.78(s,2H),1.20(d,J=19.8Hz,18H).

[0039] 13C NMR(100MHz, CDCl3)δ=144.79,144.63,144.34,144.18,137.00,136.87,134.08,133.95,133.48,132.86 ,132.74,131.08,129.19,128.00,127.67,127.54,125.84,124.99,124.68,28.77,27.52,20.50,20.31.

[0040] The synthetic route for bis[2-(tert-butylphenylphosphino)-1-naphthyl]methane is as follows:

[0041]

[0042] (2) Synthesis of methyl propionate:

[0043] 325 mL of methyl propionate, 6.4 mmol of bidentate phosphine ligand L2, 0.8 mmol of palladium acetate, 3.2 mmol of p-toluenesulfonic acid, and 75 mL of methanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 350 r / min, the reaction temperature was 110 °C, and the reaction was allowed to proceed for 30 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 96.1%.

[0044] Example 2

[0045] 325 mL of methyl propionate, 6.4 mmol of bidentate phosphine ligand L1, 0.8 mmol of palladium acetate, 3.2 mmol of p-toluenesulfonic acid, and 75 mL of methanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 300 r / min, the reaction temperature was 90 °C, and the reaction was allowed to proceed for 50 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 93.7%.

[0046] Example 3

[0047] 325 mL of methyl propionate, 6.4 mmol of bidentate phosphine ligand L3, 0.8 mmol of palladium acetate, 3.2 mmol of p-toluenesulfonic acid, and 75 mL of methanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 350 r / min, the reaction temperature was 110 °C, and the reaction was allowed to proceed for 35 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 95.1%.

[0048] Example 4

[0049] 325 mL of methyl propionate, 6.4 mmol of bidentate phosphine ligand L4, 0.8 mmol of palladium acetylacetone, 3.2 mmol of p-toluenesulfonic acid, and 75 mL of methanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 300 r / min, the reaction temperature was 100 °C, and the reaction was carried out for 35 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 94.9%.

[0050] Example 5

[0051] 325 mL of methyl propionate, 6.4 mmol of bidentate phosphine ligand L5, 0.8 mmol of palladium acetylacetone, 3.2 mmol of p-toluenesulfonic acid, and 75 mL of methanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 300 r / min, the reaction temperature was 90 °C, and the reaction was allowed to proceed for 50 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 93.2%.

[0052] Example 6

[0053] 325 mL of methyl propionate, 6.4 mmol of bidentate phosphine ligand L6, 0.8 mmol of palladium acetylacetone, 3.2 mmol of p-toluenesulfonic acid, and 75 mL of methanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 350 r / min, the reaction temperature was 110 °C, and the reaction was allowed to proceed for 30 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 95.4%.

[0054] Example 7

[0055] 325 mL of methyl propionate, 6.4 mmol of bidentate phosphine ligand L7, 0.8 mmol of palladium acetylacetone, 3.2 mmol of p-toluenesulfonic acid, and 75 mL of methanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 350 r / min, the reaction temperature was 110 °C, and the reaction was allowed to proceed for 35 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 95.8%.

[0056] Example 8

[0057] 325 mL of propyl propionate, 6.4 mmol of bidentate phosphine ligand L2, 0.8 mmol of palladium acetylacetone, 3.2 mmol of p-toluenesulfonic acid, and 80 mL of 1-propanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 350 r / min, the reaction temperature was 110 °C, and the reaction was carried out for 45 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC). The yield of propyl propionate was 93.9%.

[0058] Example 9

[0059] 325 mL of butyl propionate, 6.4 mmol of bidentate phosphine ligand L2, 0.8 mmol of palladium acetylacetone, 3.2 mmol of p-toluenesulfonic acid, and 95 mL of 1-butanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 350 r / min, the reaction temperature was 110 °C, and the reaction was carried out for 55 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC), and the yield of butyl propionate was 92.4%.

[0060] Example 10

[0061] 325 mL of cyclohexyl propionate, 6.4 mmol of bidentate phosphine ligand L2, 0.8 mmol of palladium acetylacetone, 3.2 mmol of p-toluenesulfonic acid, and 90 mL of cyclohexanol were added sequentially to a 2 L reaction vessel lined with polytetrafluoroethylene. The reaction vessel was then sealed and purged three times with argon gas. Ethylene and carbon monoxide gases were then introduced at a molar ratio of n(C₂H₄):n(CO) = 2:1. The stirring speed was 350 r / min, the reaction temperature was 110 °C, and the reaction was carried out for 65 min. After cooling to room temperature, the pressure was slowly released in a fume hood, the vessel was opened, weighed, and a sample was taken. The product was analyzed by gas chromatography (GC). The yield of cyclohexyl propionate was 91.6%.

[0062] Example 11

[0063] Catalyst recycling performance test: The first reaction was the same as in Example 3. After the reaction, the mixture was cooled to room temperature, slowly depressurized in a fume hood, opened, weighed, and sampled. The product was analyzed by gas chromatography (GC), and the yield of methyl propionate was 96.3%. The second reaction: After distilling off methanol and methyl propionate under reduced pressure, the catalyst remained in the reactor for reuse, under the same reaction conditions. The second step was repeated until the tenth reaction. After ten reactions, the yield of methyl propionate was 90.8%.

[0064] Example 12

[0065] Catalyst recycling performance test: The first reaction was the same as in Example 9. After the reaction, the mixture was cooled to room temperature, slowly depressurized in a fume hood, opened, weighed, and sampled. The product was analyzed by gas chromatography (GC), and the yield of butyl propionate was 92.8%. The second reaction: After distilling off methanol and methyl propionate under reduced pressure, the catalyst remained in the reactor for reuse, under the same reaction conditions. The second step was repeated until the tenth reaction. After ten reactions, the yield of butyl propionate was 88.6%.

[0066] In summary, this invention utilizes a catalyst system containing naphthyl bidentate phosphine ligands to efficiently convert ethylene, carbon monoxide, and lower alcohols into propionate esters. This method offers advantages such as short reaction time and good recyclability, and thus has significant application value.

[0067] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing propionic ester by ethylene hydrogen esterification reaction, characterized in that, Ethylene, carbon monoxide, and lower alcohols are synthesized by hydrogen esterification in the presence of a catalyst using propionate as a solvent. The catalyst consists of a palladium compound, a naphthyl bidentate phosphine ligand, and an acidic auxiliary agent. The structure of the naphthyl bidentate phosphine ligand is as follows: Where m is 0 or 1, n is 1 or 2; R1 is selected from phenyl, tert-butyl, cyclohexyl, 2-pyridyl, 2-thienyl or 2-furanyl, and R2 is selected from tert-butyl, cyclohexyl, 2-pyridyl, 2-thienyl or 2-furanyl.

2. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, In the structure of the naphthyl bidentate phosphine ligand, m = 0, n = 1, R1 is selected from phenyl, tert-butyl, cyclohexyl, 2-pyridyl, 2-thienyl, 2-furanyl, and R2 is selected from tert-butyl or cyclohexyl.

3. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The lower alcohol is a C1-C6 monohydric saturated alcohol, selected from methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, tert-butanol, 3-pentanol, and cyclohexanol.

4. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The propionate is one of methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, hexyl propionate, isopropyl propionate, tert-butyl propionate, 3-pentyl propionate, and cyclohexyl propionate.

5. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The palladium compound is one or more of palladium nitrate, palladium acetate, palladium acetylacetonate, palladium trifluoroacetate, palladium iodide, palladium chloride, bis(triphenylphosphine)palladium dichloride, allyl palladium chloride, tetra(triphenylphosphine)palladium, bis(dibenzylideneacetone)palladium, tri(dibenzylideneacetone)palladium, and 1,5-cyclooctadiene palladium dichloride.

6. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The acidic additive is selected from one or more of hydrochloric acid, sulfuric acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, tert-butylsulfonic acid, boric acid, or salicylic acid.

7. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The molar ratio of the naphthyl bidentate phosphine ligand to the palladium compound is (1-20):1; the molar ratio of the acidic auxiliary agent to the palladium compound is (0.5-20):

1.

8. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The mass concentration of palladium in the palladium compound is 50 to 1000 ppm based on the total mass of the reactants.

9. The method for preparing propionic acid by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The molar ratio of the raw materials ethylene, carbon monoxide and lower alcohols is (0.5-5):1:(1-5).

10. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The molar ratio of the lower alcohol to the propionate is 1:(1-30).

11. The method for preparing propionate ester by ethylene hydrogen esterification reaction according to claim 1, characterized in that, The ethylene hydrogen esterification reaction is carried out at a temperature of 60–140°C, a pressure of 0.5–5.0 MPa, and a time of 0.5–4 h.

Images