A process for the preparation of methyl propionate from ethylene or C2 mixtures

Abstract

The present disclosure relates to a method for preparing methyl propionate from ethylene or C2 mixed gas, comprising the following steps: mixing a heterogeneous catalyst with a liquid acid to obtain a mixed catalyst; the heterogeneous catalyst comprises a Pd precursor, a phosphine ligand and an acidic molecular sieve; the pH of the liquid acid is greater than or equal to 4; the content of the liquid acid in the mixed catalyst is 500-3000 ppm; pure ethylene or C2 mixed gas, CO and methanol are contacted with the mixed catalyst to carry out the reaction of ethylene alkoxycarbonylation to prepare methyl propionate, to obtain a liquid phase mixed product containing methyl propionate and an optional gas phase product containing ethane; wherein the C2 mixed gas comprises ethylene and ethane. The present disclosure replaces the homogeneous catalyst with the heterogeneous catalyst, develops a process for preparing high-value-added methyl propionate from widely available ethylene and low-cost C2 mixed gas, and can realize large-scale industrial production.

Description

Technical Field

[0001] This disclosure relates to the fields of efficient utilization of ethylene and separation of C2 mixed gases, and more specifically, to a method for preparing methyl propionate from ethylene or a C2 mixed gas. Background Technology

[0002] Ethylene is an important basic petrochemical product with continuously growing market demand. Currently, 95% of the ethylene on the market comes from steam cracking units primarily producing naphtha, with the remainder separated from dry gas, a byproduct of secondary refining processes. This byproduct dry gas has a high ethylene concentration and large total volume; direct combustion as fuel results in significant economic losses. Ethylene and ethane, due to their low boiling points, are difficult to separate and are directly separated from the dry gas as a C2 mixture. Currently, cryogenic separation is the main method for recovering ethylene from the C2 mixture, but this method suffers from high energy consumption, low recovery rates, and high investment costs (e.g., CN110715505A). In the past decade, the ethylene alkylation to ethylbenzene process, which does not involve cryogenic separation, has attracted considerable attention from enterprises (patent WO2005 / 026085A2), significantly reducing production costs and improving overall economic efficiency. However, the current market for ethylbenzene and its downstream product, styrene, is saturated, and the efficient and high-value-added utilization of ethylene and the C2 mixture has become a bottleneck restricting enterprise development.

[0003] Methyl propionate (MP) is a high-value-added chemical used to synthesize methyl methacrylate (MMA), which can be combined with formaldehyde to form even higher-value-added acrylic glass (PMMA) materials. Current methyl propionate synthesis processes mainly employ homogeneous catalyst systems, using highly corrosive strong acids (pH < 1). It is well known that homogeneous catalysts are difficult to separate and have high recovery costs, and the large quantities of strong liquid acid used cause severe environmental pollution, severe equipment corrosion, and high post-treatment costs. In recent years, solid acids have gained widespread attention due to their advantages of being environmentally friendly, non-corrosive, having low post-treatment costs, and high stability. Furthermore, heterogeneous catalysts are easy to separate and have low recovery costs, which can significantly reduce production costs and improve corporate economic efficiency. Currently, the transformation of oil refining towards chemical production will produce / byproduct large quantities of ethylene and C2 mixtures, presenting a huge development prospect. Previous studies have shown that the co-catalytic catalysis of solid acid with C2 mixed gas to prepare methyl propionate via alkoxy carbonylation exhibits good catalytic performance and separation effect. Based on this, a more efficient method for preparing methyl propionate from C2 mixed gas has been developed, effectively solving the problems of difficult separation by homogeneous catalysts and strong corrosiveness of liquid acids. At the same time, it addresses the current market demand for MP and MMA, as well as the separation problem of C2 mixed gas. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for preparing methyl propionate from ethylene or a C2 mixture, which uses widely available ethylene and inexpensive C2 mixture to prepare high-value-added methyl propionate, enabling large-scale industrial production; and solves the problems of difficult separation of homogeneous catalysts and strong corrosiveness of liquid acids.

[0005] To achieve the above objectives, this disclosure provides a method for preparing methyl propionate from ethylene or a C2 mixture, comprising the following steps: A heterogeneous catalyst is mixed with a liquid acid to obtain a mixed catalyst; the heterogeneous catalyst includes a Pd precursor, a phosphine ligand, and an acidic molecular sieve; the liquid acid has a pH ≥ 4 and less than 7; the content of the liquid acid in the mixed catalyst is 500~3000 ppm. The mixture of pure ethylene or a C2 gas mixture, CO, and methanol is contacted with the mixed catalyst to carry out the reaction of ethylene alkoxycarbonylation to prepare methyl propionate, yielding a liquid-phase mixed product containing methyl propionate and optionally a gas-phase product containing ethane; wherein the C2 gas mixture includes ethylene and ethane.

[0006] Optionally, the Pd precursor in the heterogeneous catalyst is selected from one or more of organic compounds containing divalent palladium ions and inorganic compounds containing divalent palladium ions. Preferably, the Pd precursor is selected from one or more of tris(dibenzylacetone)palladium, di(acetylacetone)palladium, palladium acetate, and palladium chloride.

[0007] Optionally, the phosphine ligand in the heterogeneous catalyst is selected from one or more of bisphosphine ligands containing three-coordinate P and monophosphine ligands containing three-coordinate P. Preferably, the phosphine ligand is selected from one or more of 1,2-bis(di-tert-butylphosphonite methyl)benzene, 1,2-bis(tert-butyl(pyridin-2-yl)phosphino)methyl)benzene, 1,1'-bis(di-tert-butylphosphino)-ferrocene, 1,1'-bis(tert-butyl(pyridin-2-yl)phosphino)-ferrocene, 1,1'-bis(diphenylphosphino)ferrocene, 4,5-bisdiphenylphosphine-9,9-dimethyloxanthracene, triphenylphosphine, tris(4-methoxyphenyl)phosphine, and 2-pyridyl-diphenylphosphine.

[0008] Optionally, the acidic molecular sieve is selected from one or more of the following: FAU configuration molecular sieve, BEA configuration molecular sieve, MWW configuration molecular sieve, MOR configuration molecular sieve, FER configuration molecular sieve and MFI configuration molecular sieve. Optionally, the FAU configuration molecular sieve is selected from one or two of Y-type molecular sieves, HY-type molecular sieves, and rare earth Y-type molecular sieves; the BEA configuration molecular sieve is selected from one or more of Beta-type molecular sieves, H-Beta-type molecular sieves, Beta-25-type molecular sieves, Beta-30-type molecular sieves, and Beta-50-type molecular sieves; the MWW configuration molecular sieve includes MCM-22 molecular sieves; the FER configuration molecular sieve includes ZSM-35 molecular sieves; the MFI configuration molecular sieve is selected from one or two of ZSM-5 and HZSM-5; optionally, the rare earth element in the rare earth Y-type molecular sieve is selected from one or more of La, Ce, Pr, Nd, and Sm; preferably, the rare earth element is selected from one or two of La and Ce; Preferably, the acid content of the acidic molecular sieve is 300~5000 μmol / g, more preferably 500~3500 μmol / g.

[0009] Optionally, the molar ratio of Pd precursor to phosphine ligand is 1:0.6~40; preferably 1:1~30. The weight ratio of Pd precursor to acidic molecular sieve is 1:40~800; preferably 1:46~160.

[0010] Optionally, the pH of the liquid acid is 4-6; optionally, the liquid acid is selected from one or more of propionic acid, boric acid and carbonic acid; preferably, the content of the liquid acid in the mixed catalyst is 700-2000 ppm.

[0011] Optionally, the pure ethylene or C2 mixed gas is selected from one or more of the following devices: catalytic cracking unit, catalytic pyrolysis unit, steam cracking unit, hydrocracking unit, and other devices for producing ethylene and C2 gas.

[0012] Optionally, the molar ratio of ethylene to ethane in the C2 mixed gas is 0.8 to 10:1, preferably 1 to 5:1; Optionally, the molar ratio of ethylene to CO in the pure ethylene or the C2 mixture is 1:0.5~3, preferably 1:1~2; the molar ratio of ethylene to methanol in the pure ethylene or the C2 mixture is 1:5~25, preferably 1:6~15.

[0013] Optionally, the reactor used in the reaction of ethylene alkoxy carbonylation to prepare methyl propionate is selected from one or more of the following: autoclave reactor, fixed bed reactor, tubular reactor, fluidized bed reactor, bubble bed reactor, and moving bed reactor.

[0014] Optionally, the conditions for the preparation of methyl propionate by ethylene alkoxy carbonylation include: The reaction temperature is 100~160℃, preferably 100~140℃; the reaction time is 3~20h, preferably 5~10h; the reaction pressure is 1~5.5MPa, preferably 2~4MPa. Optionally, the method further includes: The gaseous product containing ethane is directly fed into a steam cracking furnace for high-temperature cracking to generate ethylene; preferably, the concentration of ethane in the gaseous product is 76.45% by volume or more.

[0015] The present disclosure provides a method for preparing methyl propionate from ethylene or a C2 mixed gas using the above technical solution. This method uses ethylene or a C2 mixed gas as the reactant gas and utilizes a heterogeneous catalyst composed of a Pd precursor, phosphine ligand, and acidic molecular sieve. The surface structure of the heterogeneous catalyst is modulated by adding a weak acid (4 ≤ pH < 7) to the reaction system. Then, it undergoes an ethylene alkoxycarbonylation reaction with methanol and CO to prepare a liquid-phase product containing high-value-added MP and / or a gas-phase product containing a high concentration of ethane. The method provided by this disclosure is a green, environmentally friendly, and economically efficient process route, suitable for large-scale production and industrialization. It can replace difficult-to-separate homogeneous catalysts and highly corrosive liquid acids, and also achieves efficient utilization of ethylene and efficient separation of C2 mixed gas, effectively solving the current bottleneck in the development of high-value-added utilization of ethylene and C2 mixed gas in enterprises.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a chromatogram of the liquid product obtained in Example 1 of this disclosure. Detailed Implementation

[0018] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0020] For ethylene and C2 mixed gases produced from catalytic cracking units, catalytic pyrolysis units, steam cracking units, hydrocracking units, and other units producing ethylene and C2 mixed gases, a common method for utilizing these gases is to synthesize ethylbenzene from benzene using the ethylene and C2 mixed gases. This allows for efficient conversion of ethylene and efficient separation of the C2 mixed gases. However, ethylbenzene and its downstream product styrene have reached saturation, leading to decreased demand. Common methods for separating C2 mixed gases include cryogenic separation, but this method has high energy consumption and low ethylene recovery rates. Furthermore, direct combustion of the C2 mixed gas results in significant economic losses. Directly feeding it into a steam cracking furnace causes rapid self-polymerization and coking of high-concentration ethylene, greatly slowing down industrial production and impacting overall enterprise economic efficiency. Conversely, directly feeding the separated low-concentration ethylene into the steam cracking furnace with high-concentration ethane significantly reduces ethylene self-polymerization efficiency. Additionally, the methyl propionate synthesis process primarily uses homogeneous catalysts, which are difficult to separate from the product, have high recovery costs, require large quantities of strong liquid acid, cause severe environmental pollution, are highly corrosive to equipment, and incur high maintenance costs. The inventors of this disclosure have discovered through research that using a heterogeneous catalyst that is easily separable and has low recovery costs to replace the homogeneous catalytic system, and that the solid acid is non-corrosive, environmentally friendly, highly stable, and has low maintenance costs, can effectively improve the ethylene conversion rate and achieve efficient separation of ethylene and ethane by adding a weak acid with low corrosivity, while also exhibiting high selectivity for methyl propionate. The addition of the weak acid solution in this disclosure alters the Brønsted acid content and structural properties on the surface of the heterogeneous catalyst, enabling the heterogeneous catalyst to efficiently convert ethylene and achieve a high degree of separation between ethylene and ethane. The method provided in this disclosure can replace the homogeneous catalyst in the catalytic alkylation of ethylene to prepare methyl propionate, enabling industrial production and effectively solving the current bottleneck in the development of high-value-added utilization of ethylene and C2 mixed gases.

[0021] This disclosure provides a method for preparing methyl propionate from ethylene or a C2 mixture, comprising the following steps: A heterogeneous catalyst is mixed with a liquid acid to obtain a mixed catalyst; the heterogeneous catalyst includes a Pd precursor, a phosphine ligand, and an acidic molecular sieve; the liquid acid has a pH ≥ 4 and less than 7; the content of the liquid acid in the mixed catalyst is 500~3000 ppm. The mixture of pure ethylene or a C2 gas mixture, CO, and methanol is contacted with the mixed catalyst to carry out the reaction of ethylene alkoxycarbonylation to prepare methyl propionate, yielding a liquid-phase mixed product containing methyl propionate and optionally a gas-phase product containing ethane; wherein the C2 gas mixture includes ethylene and ethane.

[0022] This disclosure provides a method for preparing methyl propionate from ethylene or a C2 mixture. The method uses ethylene or a C2 mixture as the reactant gas and utilizes a heterogeneous catalyst composed of a Pd precursor, phosphine ligand, and acidic molecular sieve. The surface structure of the heterogeneous catalyst is modulated by adding a weak acid (4 ≤ pH < 7) to the reaction system. Then, it undergoes an ethylene alkoxycarbonylation reaction with methanol and CO to prepare a liquid-phase product containing high-value-added MP and / or a gas-phase product containing a high concentration of ethane. The method provided by this disclosure is a green, environmentally friendly, and economically efficient process route, suitable for large-scale production and industrialization. It can replace difficult-to-separate homogeneous catalysts and highly corrosive liquid acids, and also achieves efficient utilization of ethylene and efficient separation of the C2 mixture, effectively solving the current bottleneck in the development of high-value-added utilization of ethylene and C2 mixtures in enterprises.

[0023] In a preferred embodiment, the pH of the liquid acid is 4 to 6; using a weak acid with a pH within the range of this embodiment can further improve the ethylene conversion rate of the C2 mixed gas while reducing acid corrosion.

[0024] In one specific embodiment, the liquid acid is selected from one or more of propionic acid, boric acid, and carbonic acid; the liquid acid provided by this embodiment can have excellent control over the content and structural properties of Brønsted acid on the surface of heterogeneous catalysts.

[0025] In a preferred embodiment, the content of the liquid acid in the mixed catalyst is 700-2000 ppm. Adding liquid acid at the content specified in this embodiment can further improve the catalytic effect of the heterogeneous catalyst, and the method is more environmentally friendly.

[0026] In one embodiment, the Pd precursor in the heterogeneous catalyst is selected from one or more of organic compounds containing divalent palladium ions and inorganic compounds containing divalent palladium ions. Preferably, the Pd precursor is selected from one or more of tris(dibenzylacetone)palladium (Pd2(dba)3), di(acetylacetone)palladium (Pd(acac)2), palladium acetate (Pd(OAc)2), and palladium chloride (PdCl2). The Pd precursor used in this disclosure can be purchased through ordinary commercial channels or prepared by known methods.

[0027] In one embodiment, the phosphine ligand in the heterogeneous catalyst is selected from one or more of bisphosphine ligands containing three-coordinate P and monophosphine ligands containing three-coordinate P; preferably, the phosphine ligand is selected from 1,2-bis(di-tert-butylphosphonic acid methyl)benzene (d t bpx), 1,2-bis(tert-butyl(pyridin-2-yl)phosphino)methyl)benzene (Py tbpx), 1,1'-bis(di-tert-butylphosphino)-ferrocene (d t bpf), 1,1'-bis(tert-butyl(pyridin-2-yl)phosphino)-ferrocene (Py t bpf), 1,1'-bis(diphenylphosphine)ferrocene (dppf), bis(4-tert-butyl-2-(diphenylphosphino)phenyl)methane, triphenylphosphine (PPh3), 2-pyridyl-diphenylphosphine (PPh2Py); more preferably, the phosphine ligand is selected from 1,2-bis(di-tert-butylphosphonomethyl)benzene (dppf), 1,1'-bis(di-tert-butylphosphonic acid ... t bpx), 1,2-bis(tert-butyl(pyridin-2-yl)phosphino)methyl)benzene (Py t bpx), 1,1'-bis(di-tert-butylphosphino)-ferrocene (d t bpf), 1,1'-bis(tert-butyl(pyridin-2-yl)phosphino)-ferrocene (Py t The phosphine ligands used in this disclosure are one or more of bpf, bis(4-tert-butyl-2-(diphenylphosphine)phenyl)methane, and 2-pyridyl-diphenylphosphine (PPh2Py). The phosphine ligands used in this disclosure are commercially available or prepared using known methods.

[0028] In one specific embodiment, the acidic molecular sieve can be any acidic molecular sieve, and the acidic molecular sieve can be selected from one or more of the following: BEA configuration molecular sieve, FAU configuration molecular sieve, MWW configuration molecular sieve, MOR configuration molecular sieve, FER configuration molecular sieve and MFI configuration molecular sieve. Optionally, the BEA configuration molecular sieve is selected from one or more of Beta-type molecular sieves, H-Beta-type molecular sieves, Beta-25-type molecular sieves, Beta-30-type molecular sieves, and Beta-50-type molecular sieves; the FAU configuration molecular sieve is selected from one or two of Y-type molecular sieves, HY-type molecular sieves, and rare earth Y-type molecular sieves; the MWW configuration molecular sieve includes MCM-22 molecular sieves; the FER structure molecular sieve includes ZSM-35 molecular sieves; the MFI configuration molecular sieve is selected from one or two of ZSM-5 and HZSM-5; optionally, the rare earth element in the rare earth Y-type molecular sieve is selected from one or more of La, Ce, Pr, Nd, and Sm; preferably, the rare earth element is selected from one or two of La and Ce. The acidic molecular sieves used in this disclosure can be purchased through ordinary commercial channels or prepared by known methods.

[0029] In a preferred embodiment, the acid content of the acidic molecular sieve is 300~5000 μmol / g, preferably 500~3500 μmol / g. Using an acidic molecular sieve with the acid content of this embodiment as a heterogeneous catalyst can result in superior catalytic performance.

[0030] In one specific embodiment, the silicon-to-aluminum molar ratio of the FAU-configured molecular sieve is 4~100:1 (the silicon-to-aluminum molar ratio of Y-type molecular sieve is 4~100:1, the silicon-to-aluminum molar ratio of HY-type molecular sieve is 4~100:1, and the silicon-to-aluminum molar ratio of rare earth Y-type molecular sieve is 4~100:1); the silicon-to-aluminum molar ratio of the BEA-configured molecular sieve is 8~100:1 (the silicon-to-aluminum molar ratio of Beta-type molecular sieve is 8~100:1, the silicon-to-aluminum molar ratio of H-Beta-type molecular sieve is 8~100:1, the silicon-to-aluminum molar ratio of Beta-25-type molecular sieve is 8~100:1, and the silicon-to-aluminum molar ratio of Beta-30-type molecular sieve is 8~100:1, and the silicon-to-aluminum molar ratio of BEA-configured ... The silica-aluminum molar ratio of eta-50 molecular sieves is 8~100:1; the silica-aluminum molar ratio of MWW molecular sieves is 20~200:1 (the silica-aluminum molar ratio of MCM-22 molecular sieves is 20~200:1); the silica-aluminum molar ratio of MOR molecular sieves is 10~100:1; the silica-aluminum molar ratio of FER molecular sieves is 20~90:1 (the silica-aluminum molar ratio of ZSM-35 molecular sieves is 20~90:1); the silica-aluminum molar ratio of MFI molecular sieves is 20~100:1 (the silica-aluminum molar ratio of ZSM-5 molecular sieves and HZSM-5 molecular sieves is 20~100:1).

[0031] In one embodiment, the molar ratio of the Pd precursor to the phosphine ligand is 1:0.6~40; preferably 1:1~30; and the weight ratio of the Pd precursor to the acidic molecular sieve is 1:40~800; preferably 1:46~160. The heterogeneous catalyst with the composition provided in this embodiment exhibits superior catalytic performance in the reaction of ethylene or a C2 mixture to prepare methyl propionate, improving ethylene conversion and methyl propionate selectivity.

[0032] In one specific embodiment, the pure ethylene or C2 mixed gas is selected from one or more of the following: catalytic cracking unit, catalytic pyrolysis unit, steam cracking unit, hydrocracking unit, and other units that produce ethylene and C2 gas. The ethylene or C2 mixed gas sources to which the method provided in this disclosure is applicable are wide-ranging.

[0033] In a preferred embodiment, the molar ratio of ethylene to ethane in the C2 mixed gas is 0.8 to 10:1, preferably 1 to 5:1. The C2 mixed gas with the molar ratio of ethylene to ethane in this embodiment is more suitable for the method for preparing methyl propionate provided in this disclosure.

[0034] In one embodiment, the molar ratio of ethylene to CO in the pure ethylene or C2 mixed gas is 1:0.5~3, preferably 1:1~2; the molar ratio of ethylene to methanol in the pure ethylene or C2 mixed gas is 1:5~25, preferably 1:6~15. Reacting with the pure ethylene or C2 mixed gas in the molar ratio of CO and methanol provided in this embodiment yields better methyl propionate preparation results; when the reaction is carried out according to the preferred molar ratio in this embodiment, the ethylene conversion rate and methyl propionate selectivity are higher.

[0035] In one embodiment, the conditions for preparing methyl propionate by ethylene alkoxy carbonylation include: a reaction temperature of 100-160°C; a reaction time of 3-20 h; and a reaction pressure of 1-5.5 MPa. By carrying out the ethylene alkoxy carbonylation reaction under the optimized reaction conditions of this embodiment, higher ethylene conversion and methyl propionate selectivity can be obtained, achieving efficient utilization of ethylene and efficient separation of C2 mixtures, and yielding high-value-added methyl propionate chemical products.

[0036] In a preferred embodiment, the conditions for preparing methyl propionate by ethylene alkoxy carbonylation include: a reaction temperature of 100-140°C; a reaction time of 5-10 h; and a reaction pressure of 2-4 MPa. Using the preferred reaction conditions provided in this disclosure for ethylene alkoxy carbonylation further improves the ethylene conversion and methyl propionate selectivity.

[0037] In a preferred embodiment, the method further includes: directly feeding the ethane-containing gaseous product into a steam cracking furnace for high-temperature cracking to generate ethylene; preferably, the concentration of ethane in the gaseous product is 76.45% by volume or higher. The method provided in this disclosure can effectively separate C2 mixed gas to obtain ethane-containing gaseous products, which can be directly subjected to high-temperature cracking, thereby improving the resource utilization rate of the C2 mixed gas.

[0038] In one specific embodiment, the method for preparing methyl propionate from ethylene or a C2 mixed gas includes the following steps: First, a heterogeneous catalyst is composed of a Pd precursor, a phosphine ligand, and an acidic molecular sieve. A weak acid with low corrosiveness is added, and then the mixture is transferred to a reactor for an alkoxycarbonylation reaction. Before the reaction, the reactor is purged three times with N2 or other inert gas. Then, ethylene / mixed gas, CO, and methanol are introduced in a certain proportion, the temperature is raised to the reaction temperature, the heating is turned off after a certain reaction time, and after the reactor has completely cooled down, the gaseous and liquid phase products are analyzed by chromatography.

[0039] The present disclosure is further described in detail below through examples. The raw materials used in the examples are commercially available.

[0040] In the examples and comparative examples, the methods for calculating the ethylene conversion rate and methyl propionate selectivity are as shown in the following formulas (1) to (2): Ethylene conversion rate (%) = (Ethylene feed rate - Ethylene residue) / Ethylene feed rate × 100%, Equation (1); Selectivity of methyl propionate (%) = molar amount of methyl propionate / molar amount of all products × 100%, Equation (2).

[0041] The gaseous and liquid products after the reaction were analyzed by chromatography. The instruments and methods were as follows: the gaseous products were detected by an Agilent GC 7890B automated chromatograph using an HP-AL / S capillary column connected to an FID detector to analyze the residual ethylene content in the products. The ethylene conversion rate was calculated by comparing the residual ethylene content with the initial ethylene content. The concentrations of ethylene and ethane in the gaseous products were calculated using the chromatographic analysis results. The liquid products were detected by an Agilent GC 7890A automated chromatograph using an HP-5 column connected to an FID detector. The obtained liquid products were mixed with internal standards and then analyzed by chromatography. The molar amounts of each product were obtained by comparing the peak areas with the previously established standard curve, and the selectivity of each product was calculated accordingly.

[0042] Example 1 The Pd precursor (di(acetylacetone)palladium, Pd(acac)2, CAS number 14024-61-4) and the phosphine ligand (1,2-bis(di-tert-butylphosphonic acid methyl)benzene, d t bpx (CAS No. 121954-50-5) and acidic molecular sieve (Beta molecular sieve, acid content 1500 μmol / g, silicon-aluminum molar ratio 20:1) form a heterogeneous catalyst; wherein Pd(acac)2:d t A heterogeneous catalyst was prepared with a Pd(acac)2:Beta molecular sieve mass ratio of 1:1 (bpx molar ratio 1:1) and 1:46 (Pd:Beta molecular sieve mass ratio 1:46). The molar amount of Pd was 2 mmol. 500 ppm propionic acid was added (i.e., the liquid acid content in the mixed catalyst was 500 ppm). The resulting catalyst mixture was transferred to a 100 mL high-pressure reactor and sealed. Nitrogen was used to purge the reactor three times, followed by a C2 mixture at 1.5 MPa (ethylene:ethane molar ratio of 2:1), a CO mixture at 2.0 MPa (ethylene:CO molar ratio of 1:2), and 14.7126 g of anhydrous methanol (ethylene:methanol molar ratio of 1:8). The reaction temperature was 120 °C, the reaction pressure was 3.5 MPa, the high-pressure reactor was stirred at 600 rpm, and the reaction time was 5 h. After the reaction was completed and cooled, the gaseous and liquid products were collected for chromatographic analysis.

[0043] The chromatogram of the liquid product after the reaction in this embodiment is shown below. Figure 1 .Depend on Figure 1 It can be seen that the method provided in this disclosure can be used to prepare methyl propionate, a high-value chemical product, using a C2 mixed gas, with long-chain alkanes as the internal standard.

[0044] Example 2 The Pd precursor (di(acetylacetone)palladium, Pd(acac)2, CAS number 14024-61-4), the phosphine ligand (1,2-bis(tert-butyl(pyridin-2-yl)phosphino)methyl)benzene, Py t bpx (CAS No. 2093415-45-1) and acidic molecular sieve (Beta type molecular sieve, acid content 1500 μmol / g, silicon-aluminum molar ratio 20:1) form a heterogeneous catalyst; according to Pd(acac)2:Py t A heterogeneous catalyst was prepared with a βpx molar ratio of 1:1 and a Pd(acac)2:Beta molecular sieve mass ratio of 1:46, containing 2 mmol of Pd. 1500 ppm of propionic acid was added (i.e., the liquid acid content in the mixed catalyst was 1500 ppm). The resulting catalyst system was transferred to a 100 mL high-pressure reactor and sealed. The reactor was purged three times with nitrogen, then purged with a C2 mixture at 1.5 MPa (the molar ratio of ethylene to ethane in the C2 mixture was 2:1), followed by CO gas at 2.0 MPa (the molar ratio of ethylene to CO was 1:2), and finally 14.7126 g of anhydrous methanol (the molar ratio of ethylene to methanol was 1:8). The reaction temperature was 120 °C, the reaction pressure was 3.5 MPa, the high-pressure reactor was stirred at 600 rpm, and the reaction time was 5 h. After the reaction was completed and cooled, the gaseous and liquid products were collected for chromatographic analysis.

[0045] Example 3 The Pd precursor (di(acetylacetone)palladium, Pd(acac)2, CAS number 14024-61-4), the phosphine ligand (1,2-bis(tert-butyl(pyridin-2-yl)phosphino)methyl)benzene, Py t bpx (CAS No. 2093415-45-1) and acidic molecular sieve (Y-type molecular sieve, acid content 1360 μmol / g, silicon-aluminum molar ratio 20:1) form a heterogeneous catalyst; according to Pd(acac)2:Py tA heterogeneous catalyst was prepared with a bpx molar ratio of 1:1 and a Pd(acac)2:Y molecular sieve mass ratio of 1:46, containing 2 mmol of Pd. 1500 ppm of propionic acid was added (i.e., the liquid acid content in the mixed catalyst was 1500 ppm). The resulting catalyst system was transferred to a 100 mL high-pressure reactor and sealed. The reactor was purged three times with nitrogen, then purged with a C2 mixture at 1.5 MPa (the molar ratio of ethylene to ethane in the C2 mixture was 2:1), followed by CO gas at 2.0 MPa (the molar ratio of ethylene to CO was 1:2), and finally 14.7126 g of anhydrous methanol (the molar ratio of ethylene to methanol was 1:8). The reaction temperature was 120 °C, the reaction pressure was 3.5 MPa, the high-pressure reactor was stirred at 600 rpm, and the reaction time was 5 h. After the reaction was completed and cooled, the gaseous and liquid products were collected for chromatographic analysis.

[0046] Example 4 A heterogeneous catalyst was prepared by combining a Pd precursor (di(acetylacetone)palladium, Pd(acac)2, CAS No. 14024-61-4), a phosphine ligand (1,1'-bis(diphenylphosphine)ferrocene, dppf, CAS No. 12150-46-8), and an acidic molecular sieve (ZSM-5 type molecular sieve, acid content 1480 μmol / g, silicon-aluminum molar ratio 20:1). The heterogeneous catalyst was prepared with a Pd(acac)2:dppf molar ratio of 1:4 and a Pd(acac)2:ZSM-5 type molecular sieve mass ratio of 1:46, with a Pd molar content of 2 mmol. 1500 ppm propionic acid was added (i.e., the liquid acid content in the mixed catalyst was 1500 ppm). The resulting catalyst system was transferred to a 100 mL high-pressure reactor and sealed. The reaction mixture was purged three times with nitrogen, then purged with a C2 mixture at 1.5 MPa (ethylene:ethane molar ratio of 2:1), followed by CO gas at 2.0 MPa (ethylene:CO molar ratio of 1:2); and finally, 14.7126 g of anhydrous methanol (ethylene:methanol molar ratio of 1:8). The reaction was carried out at 120 °C and 3.5 MPa, with a high-pressure reactor stirring speed of 600 rpm for 5 h. After the reaction was completed and cooled, the gaseous and liquid products were collected for chromatographic analysis.

[0047] Example 5 The Pd precursor (di(acetylacetone)palladium, Pd(acac)2, CAS number 14024-61-4) and the phosphine ligand (1,1'-bis(di-tert-butylphosphino)-ferrocene, d t bpf (CAS No. 84680-95-5) and acidic molecular sieve (MCM-22 type molecular sieve, acid content 1400 μmol / g, silicon-aluminum molar ratio 20:1) form a heterogeneous catalyst; according to Pd(acac)2:dt A heterogeneous catalyst was prepared with a bpf molar ratio of 1:4 and a Pd(acac)2:MCM-22 molecular sieve mass ratio of 1:46, containing 2 mmol of Pd. 3000 ppm of boric acid was added (i.e., the liquid acid content in the mixed catalyst was 3000 ppm). The resulting catalyst system was transferred to a 100 mL high-pressure reactor and sealed. The reactor was purged three times with nitrogen, then purged with a C2 mixture at 1.5 MPa (the molar ratio of ethylene to ethane in the C2 mixture was 2:1), followed by CO gas at 2.0 MPa (the molar ratio of ethylene to CO was 1:2), and finally 14.7126 g of anhydrous methanol (the molar ratio of ethylene to methanol was 1:8). The reaction temperature was 120 °C, the reaction pressure was 3.5 MPa, the high-pressure reactor was stirred at 600 rpm, and the reaction time was 2 h. After the reaction was completed and cooled, the gaseous and liquid products were collected for chromatographic analysis.

[0048] Example 6 A heterogeneous catalyst was prepared by combining a Pd precursor (di(acetylacetone)palladium, Pd(acac)2, CAS No. 14024-61-4), a phosphine ligand (2-pyridyl-diphenylphosphine, PPh2Py, CAS No. 37943-90-1), and an acidic molecular sieve (MOR type molecular sieve, acid content 1490 μmol / g, silicon-aluminum molar ratio 20:1). The heterogeneous catalyst was prepared with a Pd(acac)2:PPh2Py molar ratio of 1:25 and a Pd(acac)2:MOR type molecular sieve mass ratio of 1:100, with a Pd molar content of 2 mmol. 3000 ppm of carbonic acid was added (i.e., the liquid acid content in the mixed catalyst was 3000 ppm). The resulting catalyst system was transferred to a 100 mL high-pressure reactor and sealed. The reaction mixture was purged three times with nitrogen, then purged with a C2 mixture at 1.5 MPa (ethylene:ethane molar ratio of 2:1), followed by CO gas at 2.0 MPa (ethylene:CO molar ratio of 1:2); and finally, 14.7126 g of anhydrous methanol (ethylene:methanol molar ratio of 1:8). The reaction was carried out at 120 °C and 3.5 MPa, with a high-pressure reactor stirring speed of 600 rpm for 5 h. After the reaction was completed and cooled, the gaseous and liquid products were collected for chromatographic analysis.

[0049] Example 7 A heterogeneous catalyst was prepared by combining a Pd precursor (palladium acetate, Pd(oac)2, CAS No. 3375-31-3), a phosphine ligand (triphenylphosphine, PPh3, CAS No. 603-35-0), and an acidic molecular sieve (ZSM-35 molecular sieve, acid content 1440 μmol / g, silicon-aluminum molar ratio 20:1). The heterogeneous catalyst was prepared with a Pd(oac)2:PPh3 molar ratio of 1:25 and a Pd(oac)2:ZSM-35 molecular sieve mass ratio of 1:100, with a Pd molar content of 2 mmol. 3000 ppm of carbonic acid was added (i.e., the liquid acid content in the mixed catalyst was 3000 ppm). The resulting catalyst system was transferred to a 100 mL high-pressure reactor and sealed. The mixture was purged three times with nitrogen, then purged with a C2 mixture at 1.5 MPa (ethylene:ethane molar ratio of 2:1), followed by CO gas at 2.0 MPa (ethylene:CO molar ratio of 1:2); and finally, 14.7126 g of anhydrous methanol at a ethylene:methanol molar ratio of 1:8. The reaction was carried out at 120 °C and 3.5 MPa, with a high-pressure reactor stirring speed of 600 rpm for 5 h. After the reaction was completed and cooled, the gaseous and liquid products were collected for chromatographic analysis.

[0050] Example 8 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The pH of the propionic acid used was 6.5; the rest of the process was the same as in Example 1. After the reaction was completed and the temperature was lowered, the reaction gas and liquid products were collected for chromatographic analysis.

[0051] Example 9 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The liquid acid content in the mixed catalyst was 2000 ppm; the rest of the process was the same as in Example 1. After the reaction was completed and the temperature was lowered, the reaction gas and liquid products were collected for chromatographic analysis.

[0052] Example 10 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The molar ratio of Pd precursor to phosphine ligand is 1:0.6; the mass ratio of Pd precursor to acidic molecular sieve is 1:40; the rest of the process is the same as in Example 1. After the reaction is completed and the temperature is lowered, the reaction gas and liquid products are collected for chromatographic analysis.

[0053] Example 11 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The molar ratio of Pd precursor to phosphine ligand is 1:0.2; the mass ratio of Pd precursor to acidic molecular sieve is 1:20; the rest of the process is the same as in Example 1. After the reaction is completed and the temperature is lowered, the reaction gas and liquid products are collected for chromatographic analysis.

[0054] Example 12 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The molar ratio of ethylene to ethane in the introduced C2 mixed gas was 0.8:1; the rest of the process was the same as in Example 1. After the reaction was completed and the temperature was lowered, the reaction gas and liquid products were collected for chromatographic analysis.

[0055] Example 13 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The molar ratio of ethylene to ethane in the introduced C2 mixed gas was 0.5:1; the rest of the process was the same as in Example 1. After the reaction was completed and the temperature was lowered, the reaction gas and liquid products were collected for chromatographic analysis.

[0056] Example 14 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The molar ratio of ethylene to CO in the C2 mixture is 1:2.5; the molar ratio of ethylene to methanol in the C2 mixture is 1:20; the remaining process is the same as in Example 1. After the reaction is completed and the temperature is lowered, the reaction gas and liquid products are collected for chromatographic analysis.

[0057] Example 15 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The molar ratio of ethylene to CO in the C2 mixture is 1:0.2; the molar ratio of ethylene to methanol in the C2 mixture is 1:3; the rest of the process is the same as in Example 1. After the reaction is completed and the temperature is lowered, the reaction gas and liquid products are collected for chromatographic analysis.

[0058] Example 16 This embodiment refers to the method in Embodiment 1, and the only difference from Embodiment 1 is: The conditions for preparing methyl propionate by ethylene alkoxy carbonylation include: a reaction temperature of 145°C; a reaction time of 3 h; a reaction pressure of 4.5 MPa; the remaining process is the same as in Example 1. After the reaction is completed and the temperature is lowered, the reaction gas and liquid products are collected for chromatographic analysis.

[0059] Comparative Example 1 This comparative example follows the method in Example 1, except that no acidic molecular sieve is added. The rest of the process is the same as in Example 1, and the reaction gas and liquid products are collected for chromatographic analysis.

[0060] Comparative Example 2 This comparative example follows the preparation method in Example 1, but differs from Example 1 in that no acidic molecular sieve is added, and 4500 ppm of propionic acid is added.

[0061] The test results of the above embodiments and comparative examples are listed in Table 1 below.

[0062] Table 1

[0063] According to the data in Table 1 above, we can see that: In Comparative Example 1, the catalyst used in the process of preparing methyl propionate from C2 mixed gas did not contain acidic molecular sieves. The ethylene conversion rate in Comparative Example 1 was only 0.11%, and the selectivity for methyl propionate was 0. This indicates that the catalyst in Comparative Example 1, without the addition of acidic molecular sieves, does not catalyze the reaction of ethylene in the C2 mixed gas to produce methyl propionate. In Comparative Example 2, no acidic molecular sieves were added, and 4500 ppm of propionic acid was added. The selectivity for methyl propionate in Comparative Example 2 was also 0, indicating that the catalyst in Comparative Example 2 also does not catalyze the reaction of ethylene in the C2 mixed gas to produce methyl propionate. Compared with Comparative Examples 1-2, Examples 1-16 prepared methyl propionate from ethylene or C2 mixed gas according to the method provided in this disclosure. Examples 1-16 have high ethylene conversion and high methyl propionate selectivity, and the ethane concentration in the gas phase product is also higher. Comparing Example 1 with Example 8, it can be seen that the pH of the acid solution in Example 1 is within the preferred range provided in this disclosure, the ethylene conversion rate and methyl propionate selectivity are higher in Example 1, and the ethane concentration in the gas phase product is also higher. Comparing Example 1 and Example 9, it can be seen that the content of liquid acid in the mixed catalyst used in Example 9 is within the preferred range provided in this disclosure. The ethylene conversion rate and methyl propionate selectivity in Example 9 are higher, and the ethane concentration in the gas phase product is also higher. Comparing Example 10 with Example 11, it can be seen that the feed ratio of the mixed catalyst in Example 10 is within the optimized range provided in this disclosure. Example 10 has a higher ethylene conversion and methyl propionate selectivity, and also a higher ethane concentration in the gas phase product. Further comparing Example 10 with Example 1, it can be seen that the feed ratio of the mixed catalyst in Example 1 is within the further preferred range provided in this disclosure. Example 1 has a higher ethylene conversion and methyl propionate selectivity, as well as a higher ethane concentration in the gas phase product. Comparing Example 12 with Example 13, it can be seen that in Example 12, the molar ratio of ethylene / ethane in the C2 mixed gas is within the optimized range provided in this disclosure. Example 12 also exhibits higher ethylene conversion and methyl propionate selectivity, and a higher ethane concentration in the gaseous product. Furthermore, comparing Example 12 with Example 1, it can be seen that in Example 1, the molar ratio of ethylene / ethane in the C2 mixed gas is within the further preferred range provided in this disclosure. Example 1 also exhibits higher ethylene conversion and methyl propionate selectivity, and a higher ethane concentration in the gaseous product. Comparing Example 14 with Example 15, it can be seen that the molar ratio of ethylene to CO and methanol in the C2 mixed gas in Example 14 is within the optimized range provided in this disclosure. Example 14 has a higher ethylene conversion rate and methyl propionate selectivity, and a higher ethane concentration in the gas phase product. Further comparing Example 14 with Example 1, it can be seen that the molar ratio of ethylene to CO and methanol in the C2 mixed gas in Example 1 is within the further preferred range provided in this disclosure. Example 1 has a higher ethylene conversion rate and methyl propionate selectivity, and a higher ethane concentration in the gas phase product. Comparing Example 1 with Example 16, it can be seen that the conditions for the preparation of methyl propionate by ethylene alkoxy carbonylation in Example 1 are within the preferred range provided in this disclosure. In Example 1, a higher ethylene conversion and methyl propionate selectivity can be obtained, and the ethane concentration in the gas phase product is also higher.

[0064] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0065] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0066] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing methyl propionate from ethylene or a C2 mixture, characterized in that, Includes the following steps: A heterogeneous catalyst is mixed with a liquid acid to obtain a mixed catalyst; the heterogeneous catalyst includes a Pd precursor, a phosphine ligand, and an acidic molecular sieve; the liquid acid has a pH ≥ 4 and less than 7; the content of the liquid acid in the mixed catalyst is 500~3000 ppm. The mixture of pure ethylene or a C2 gas mixture, CO, and methanol is contacted with the mixed catalyst to carry out the reaction of ethylene alkoxycarbonylation to prepare methyl propionate, yielding a liquid-phase mixed product containing methyl propionate and optionally a gas-phase product containing ethane; wherein the C2 gas mixture includes ethylene and ethane.

2. The method according to claim 1, characterized in that, The Pd precursor in the heterogeneous catalyst is selected from one or more of organic compounds containing divalent palladium ions and inorganic compounds containing divalent palladium ions. Preferably, the Pd precursor is selected from one or more of tris(dibenzylacetone)palladium, di(acetylacetone)palladium, palladium acetate, and palladium chloride.

3. The method according to claim 1, characterized in that, The phosphine ligand in the heterogeneous catalyst is selected from one or more of bisphosphine ligands containing tricoordinate P and monophosphine ligands containing tricoordinate P. Preferably, the phosphine ligand is selected from one or more of 1,2-bis(di-tert-butylphosphonite methyl)benzene, 1,2-bis(tert-butyl(pyridin-2-yl)phosphino)methyl)benzene, 1,1'-bis(di-tert-butylphosphino)-ferrocene, 1,1'-bis(tert-butyl(pyridin-2-yl)phosphino)-ferrocene, 1,1'-bis(diphenylphosphino)ferrocene, 4,5-bisdiphenylphosphine-9,9-dimethyloxanthracene, triphenylphosphine, tris(4-methoxyphenyl)phosphine, and 2-pyridyl-diphenylphosphine.

4. The method according to claim 1, characterized in that, The acidic molecular sieve is selected from one or more of the following: FAU configuration molecular sieve, BEA configuration molecular sieve, MWW configuration molecular sieve, MOR configuration molecular sieve, FER configuration molecular sieve and MFI configuration molecular sieve. Optionally, the FAU configuration molecular sieve is selected from one or two of Y-type molecular sieves, HY-type molecular sieves, and rare earth Y-type molecular sieves; the BEA configuration molecular sieve is selected from one or more of Beta-type molecular sieves, H-Beta-type molecular sieves, Beta-25-type molecular sieves, Beta-30-type molecular sieves, and Beta-50-type molecular sieves; the MWW configuration molecular sieve includes MCM-22 molecular sieves; the FER configuration molecular sieve includes ZSM-35 molecular sieves; the MFI configuration molecular sieve is selected from one or two of ZSM-5 and HZSM-5; optionally, the rare earth element in the rare earth Y-type molecular sieve is selected from one or more of La, Ce, Pr, Nd, and Sm; preferably, the rare earth element is selected from one or two of La and Ce; Preferably, the acid content of the acidic molecular sieve is 300~5000 μmol / g, more preferably 500~3500 μmol / g.

5. The method according to claim 1, characterized in that, The molar ratio of Pd precursor to phosphine ligand is 1:0.6~40; preferably 1:1~30. The weight ratio of Pd precursor to acidic molecular sieve is 1:40~800; preferably 1:46~160.

6. The method according to claim 1, characterized in that, The pH of the liquid acid is 4 to 6; optionally, the liquid acid is selected from one or more of propionic acid, boric acid and carbonic acid; preferably, the content of the liquid acid in the mixed catalyst is 700 to 2000 ppm.

7. The method according to claim 1, characterized in that, The pure ethylene or C2 mixed gas is selected from one or more of the following devices: catalytic cracking unit, catalytic pyrolysis unit, steam cracking unit, hydrocracking unit, and other devices that produce ethylene and C2 gas.

8. The method according to claim 1, characterized in that, The molar ratio of ethylene to ethane in the C2 mixed gas is 0.8 to 10:1, preferably 1 to 5:1; Optionally, the molar ratio of ethylene to CO in the pure ethylene or the C2 mixture is 1:0.5~3, preferably 1:1~2; the molar ratio of ethylene to methanol in the pure ethylene or the C2 mixture is 1:5~25, preferably 1:6~15.

9. The method according to claim 1, characterized in that, The reactor used in the reaction of preparing methyl propionate by ethylene alkoxy carbonylation is selected from one or more of the following: autoclave reactor, fixed bed reactor, tubular reactor, fluidized bed reactor, bubbling bed reactor, and moving bed reactor.

10. The method according to claim 1, characterized in that, The conditions for the preparation of methyl propionate by ethylene alkoxy carbonylation include: The reaction temperature is 100~160℃, preferably 100~140℃; the reaction time is 3~20h, preferably 5~10h; the reaction pressure is 1~5.5MPa, preferably 2~4MPa. Optionally, the method further includes: The gaseous product containing ethane is directly fed into a steam cracking furnace for high-temperature cracking to generate ethylene; preferably, the concentration of ethane in the gaseous product is 76.45% by volume or more.

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