Catalyst composition for preparing unsaturated carboxylate from carbon dioxide and ethylene

Abstract

The invention discloses a catalyst composition for preparing unsaturated carboxylates from carbon dioxide and ethylene, and relates to the technical field of catalyst compositions. By mass fraction, the raw materials of the catalyst composition include: 1 part of ligand, 0.5-2 parts of metal source catalyst and 50-400 parts of alkoxide. The invention provides a ligand of a novel structure, a catalyst composition for preparing unsaturated carboxylates from carbon dioxide and ethylene, which can effectively catalyze the production process of unsaturated carboxylates and effectively catalyze the carboxylation of carbon dioxide and ethylene. Unsaturated carboxylates are prepared by one-step reaction of carbon dioxide and ethylene. The catalyst composition of the present invention can be easily synthesized from inexpensive precursors, is stable to air and humidity, and has a high catalyst conversion number, which can reach more than 500.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst compositions, in particular to a catalyst composition for preparing unsaturated carboxylic acid salts from carbon dioxide and ethylene. Background Art

[0002] Carbon dioxide in the atmosphere is of great significance to the earth's ecosystem. Photosynthesis, food production, etc. are inseparable from carbon dioxide. Today's fossil fuels also originate from carbon dioxide millions of years ago. However, with the increasingly accelerated global industrialization process, the sudden increase in the world's population, the substantial improvement in human living standards, and the massive consumption of energy, the global carbon dioxide emissions have also increased year by year. At present, it has exceeded the load of the ecosystem and cannot achieve a virtuous cycle. Many studies have shown that the large-scale emission of carbon dioxide and its large accumulation in the atmosphere are important causes of global climate deterioration. For example, the "greenhouse effect" that causes global warming is caused by the large-scale emission of carbon dioxide, which in turn has caused a series of environmental problems that threaten the survival of life on Earth, such as melting glaciers, desertification, and species extinction.

[0003] Since carbon dioxide is a cheap, non-toxic and abundantly available C1 resource, the development of carbon dioxide for the production of organic chemicals has huge industrial benefits worldwide. People have always focused on how to effectively capture, fix and convert carbon dioxide. At present, people have achieved some success in converting carbon dioxide into certain chemical products, such as using carbon dioxide to produce polycarbonates, cyclic carbonates, salicylic acid and urea. However, due to the high kinetic inertness and thermodynamic stability of carbon dioxide, the amount of carbon dioxide currently consumed in chemical reactions is less than 1% of the total global emissions.

[0004] Carbon dioxide has been used as a precursor required in the production process of chemicals, such as in the production of unsaturated carboxylates, especially acrylic acid and its derivatives. Acrylic acid and its derivatives are further used as precursors for the synthesis of acrylate polymers. Acrylate polymers are widely used in many fields such as coatings, adhesives, chemical building materials, sanitary products, paper processing, polishing, leather, fibers, detergents, sealants, paints, etc. SAP (super absorbent resin) is mainly composed of sodium polyacrylate, and the global SAP production capacity is about 5 million tons. In 2020, the global SAP consumption is about 3.4 million tons, and it is expected to grow to 4.4 million in 2025. In the future, SAP will develop towards high performance, composite, functional and degradable trends.

[0005] Typically, unsaturated carboxylic acids and their derivatives can be produced by carboxylation of carbon dioxide and small molecule ethylene. The raw materials used in this production process are cheap and can be produced in large quantities in the petrochemical industry. Although carbon dioxide has long been one of the optional raw materials for preparing sodium acrylate and its derivatives to produce acrylate polymers, the application of ethylene in this process has been less than 10 years.

[0006] The metal centers for preparing unsaturated carboxylates from carbon dioxide and ethylene are mainly nickel and palladium. However, the ligands currently disclosed in the production process for preparing unsaturated carboxylates from carbon dioxide and ethylene are mainly bisphosphine, dinitrogen and carbene ligands, and this type of ligand has not further improved the TON of the catalytic system. Ligands play an important role in the coupling reaction of carbon dioxide and ethylene. The structure of the ligand directly affects the selectivity of the coupling reaction. Therefore, it is particularly important to design and synthesize ligands with new structures, which is also a hot topic in this field. Summary of the invention

[0007] Based on the above content, the present invention provides a catalyst composition for preparing unsaturated carboxylates from carbon dioxide and ethylene. By developing a ligand with a new structure, a catalyst composition for preparing unsaturated carboxylates from carbon dioxide and ethylene is prepared, which can effectively catalyze the carboxylation of carbon dioxide and ethylene, and greatly improve the catalyst conversion number while preparing unsaturated carboxylates by one-step reaction of carbon dioxide and ethylene.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] One of the technical solutions of the present invention is a catalyst composition for preparing unsaturated carboxylic acid salts from carbon dioxide and ethylene. The raw materials of the catalyst composition include, by weight, 1 part of a ligand, 0.5-2 parts of a metal source catalyst and 50-400 parts of an alkoxide; the structural formula of the ligand is shown in Formula I:

[0010]

[0011] In formula I, R1 is selected from one of ethyl, vinyl, phenyl or cyclohexyl;

[0012] R2, R3 and R4 are independently selected from one of alkyl, cycloalkyl, aryl and arylalkyl; wherein the cycloalkyl, aryl and aryl moieties in arylalkyl may be unsubstituted or may have 1, 2, 3 or 4 identical or different substituents, for example, C l , Br, I, F, C1-C8 alkyl or C1-C4 alkoxy, or a secondary amine having the general formula N(R7)2, wherein R7 is an alkyl group having 1-4 carbon atoms.

[0013] Furthermore, R1 is selected from one of ethyl, vinyl and phenyl; R2, R3 and R4 are independently selected from one of methyl, ethyl, tert-butyl, phenyl, cyclohexyl and 2,4,6-trimethylphenyl.

[0014] Furthermore, the structural formula of the ligand is shown in any one of Formula II to Formula VII:

[0015]

[0016] In the formula, Mes represents mesityl, and Me represents methyl.

[0017] Further, the metal source catalyst is MX2 or MX3, wherein X is a halide, a pseudohalide, a carboxylate, an alkoxyl, a carbonate, a sulfate, a nitrate, a hydroxide, an acetylacetonate, a cyclopentadiene, and a corresponding adduct with a solvent or water, and M is a transition metal; the alkoxide comprises a general formula O-CR5(R6)2, having a direct bond to [O - ] a secondary or tertiary carbon atom of a group, wherein R5 is H, C1-C 10 Alkyl and C3-C 10 One of the cycloalkyl groups; wherein R6 is C1-C 16 The hydrocarbon group, any two or three R6 and the secondary or tertiary carbon atoms to which they are bonded together form one or more 3-8 membered carbocyclic rings; preferably, the R6 is C1-C 16 Alkyl, C3-C 16 Cycloalkyl and C6-C 14 More preferably, R6 is C1-C 10 Alkyl, C 3- C 10 A cycloalkyl group.

[0018] Further, the alkoxide comprises one selected from O-tert-butyl, O-sec-propyl, O-sec-butyl, O-cyclopropyl, O-((1-methyl)-cyclopropyl), O-cyclohexyl and O-((1-methyl)-cyclohexyl) subunits. Preferably, the alkoxide is isopropoxide or tert-butoxide.

[0019] Further, the metal source catalyst is a nickel source catalyst or a palladium source catalyst; preferably, the nickel source catalyst is selected from [Ni(COD)2], NiF2, NiCl2, NiBr2, NiI2, [Ni(OAc)2], [Ni(Ph3P)2(Cl)2], [Ni((PPh2)2Fc)(Cl)2], [Ni(CO)4], [Ni(PPh3)2(CO)2], [Ni(NO3)2], [Ni(OH)2], [Ni(PPh3)4], [Ni(CF3COO)2], [Ni(SO4)], [Ni(P(OPh)3)4], [Ni(C7H 15 [Ni(PbO)2], [Ni(PbO)3], [Ni(PbO)4], [Ni(PbO)5], [Ni(PbO)6], [Ni(PbO)7], [Ni(PbO)8], [Ni(PbO)9], [Ni(PbO)10], [Ni(PbO)11], [Ni(PbO)12], [Ni(PbO)13], [Ni(PbO)14], [Ni(PbO)15], [Ni(PbO)16], [Ni(PbO)17], [Ni(PbO)18], [Ni(PbO)19], [Ni(PbO)20], [Ni(PbO)21], [Ni(PbO)22], [Ni(PbO)23], [Ni(PbO)24], [Ni(PbO)25], [Ni(PbO)26], [Ni(PbO)27], [Ni(PbO)28], [Ni(PbO)29], [Ni(PbO)3 2], [Pd(PPh3)4], [Pd(COD)(Cl)(Me)], [Pd(Phen)(OAc)2], [Pd2(PtBu3)2(Br)2], [Pd(C6H5CN)2(Cl)2], [Pd(PCy3)2(Cl)2], [Pd(PPh3)2(Cl)2], [Pd(TMEDA)(Cl)2], [Pd(TMEDA)(CH3)2], [Pd3(OAc)6], [Pd(CF3COO)2] and [Pd(COD)(Cl)2]. More preferably, the nickel source catalyst is [Ni(COD)2]; the palladium source catalyst is PdCl2 or [Pd(OAc)2].

[0020] The second technical solution of the present invention is a method for preparing unsaturated carboxylic acid salts by one-step reaction of carbon dioxide and ethylene, comprising the following steps:

[0021] The catalyst composition is dissolved in a solvent to obtain a mixture; ethylene and carbon dioxide are added to the mixture to react to obtain an unsaturated carboxylate.

[0022] Furthermore, the molar ratio of ethylene to carbon dioxide is 1:2-4.

[0023] Further, the reaction temperature is 100°C-180°C, and the reaction time is 10-25 hours. Preferably, the reaction temperature is 130°C-150°C.

[0024] Further, the solvent is an aprotic organic solvent. Preferably, the solvent is a cyclic alkyl ether having 4-8 carbon atoms, a dialkyl ether having 2-12 carbon atoms, a cycloalkyl alkyl ether having 4-12 carbon atoms, an aryl alkyl ether having 7-16 carbon atoms, a biaryl having 12-16 carbon atoms, a diaryl ether having 12-16 carbon atoms, a C6-C 10 C1-C8 alkyl esters of aromatic monocarboxylic acids, C6-C 10 The solvent is one of di-C1-C8 alkyl esters of aromatic dicarboxylic acids, dialkyl carbonates having 3-13 carbon atoms, diethers consisting of dioxyalkylene groups having 2-8 carbon atoms and two C1-C8 alkyl groups, benzene in which 1-4 hydrogen atoms are replaced by 1-4 C1-C4 alkyl groups, alkanes having 5-18 carbon atoms, and mixtures thereof. More preferably, the solvent is one of tetrahydrofuran, anisole, phenyl butyl ether, dibutyl ether, biphenyl, a mixture of N-dodecyl pyrrolidone, N-ethyl pyrrolidone, N-methyl pyrrolidone and diphenyl ether, cyclopentyl methyl ether, dibutyl phthalate, butyl benzoate, diethyl carbonate, dibutyl glycol ether, dibutylformamide, dimethylacetamide, toluene, 2-methyltetrahydrofuran, monochlorobenzene, and mixtures thereof.

[0025] The selection principle of the aprotic organic solvent of the present invention is as follows: (I) it is chemically inert relative to the carboxylation of ethylene; (II) the base and the carboxylation catalyst have good solubility therein. Therefore, the available aprotic organic solvent is in principle a chemically inert non-polar solvent, such as aliphatic, aromatic or aromatic aliphatic hydrocarbons, or ethers, such as octane and higher alkanes, benzene, toluene, xylene, chlorobenzene and anisole. The reaction medium may contain, for example, an aprotic organic solvent selected from the following group: aromatic hydrocarbons, halogenated aromatic hydrocarbons, alkylated aromatic hydrocarbons, alkanes, ethers, dimethylformamide, dimethyl sulfoxide and mixtures thereof. Examples of suitable ethers are dimethyl ether, diethyl ether, di-tert-butyl ether, di-n-butyl ether, tetrahydrofuran and 2-methyltetrahydrofuran.

[0026] The method for preparing unsaturated carboxylic acid salts by one-step reaction of carbon dioxide and ethylene can be carried out in a reactor, including but not limited to a fixed bed reactor, a batch reactor or a continuous reactor.

[0027] The present invention discloses the following technical effects:

[0028] The present invention provides a ligand with a novel structure, which is used for preparing a catalyst composition for producing unsaturated carboxylates from carbon dioxide and ethylene, and can effectively catalyze the production process of unsaturated carboxylates and effectively catalyze the carboxylation of carbon dioxide and ethylene, thereby realizing the one-step reaction of carbon dioxide and ethylene to prepare unsaturated carboxylates.

[0029] The catalyst composition of the present invention can be easily synthesized from cheap precursors, is stable to air and humidity, and has a high catalyst conversion number, which can reach more than 500 at the highest.

[0030] The catalyst compositions commonly used in the prior art generally contain reducing agents such as zinc, L-ascorbic acid or sodium citrate, etc. The presence of reducing agents can promote the 2+ or Ni 2+ The present invention reduces the compound and still obtains a higher catalyst conversion number when the addition of reducing agent is omitted. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 For Example 1 1 H-NMR spectrum. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0035] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0036] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0037] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0038] Unless otherwise specified, the "parts" described in the present invention are all based on mass parts.

[0039] The structural formulas of the ligands used in the embodiments of the present invention are shown in Formula II to Formula VII:

[0040]

[0041] The following abbreviations are used in the embodiments of the present invention:

[0042] DBF dimethylformamide

[0043] DMAc dimethyl

[0044] DMI 1,3-Dimethyl-2-imidazolidinone

[0045] CHP N-cyclohexylpyrrolidone

[0046] Cyclohexyl

[0047] NaOCy Sodium cyclohexanol

[0048] NaOiPr 2-Propanol Sodium

[0049] NaOsecBu 2-Butanol Sodium

[0050] NaOtBuSodium tert-butoxide

[0051] NaOtPentoxideSodium tert-pentoxide

[0052] NDP N-dodecyl pyrrolidone

[0053] NEP N-Ethylpyrrolidone

[0054] NMP N-Methylpyrrolidone

[0055] THF Tetrahydrofuran

[0056] TON Turnover number with respect to transition metal; number of moles of unsaturated carboxylate obtained per mole of transition metal.

[0057] Examples 1-13 (Raw material types, dosages and reaction conditions are shown in Table 1)

[0058] In the 60mL steel autoclave in the glove box, add transition metal source, ligand II and alkoxide and the solid mixture obtained is dissolved in the solvent.The autoclave is taken out from the glove box and under 800rpm stirring and at 25 ℃, 10 bar ethylene and 40 bar carbon dioxide are added.After stirring at 800rpm and 145 ℃ of temperature, the autoclave is cooled to 20 ℃, the pressure is released and the reaction mixture, i.e. the crude reaction product is transferred to a 100mL glass bottle.The residue in the autoclave container is reclaimed and transferred to a glass bottle with 15mL D2O.In this two-phase mixture, 3-(trimethylsilyl)-2,2,3,3-d4 propionic acid sodium salt (0.13mmol, 0.0216g), additional 10mL D2O and 40mL Et2O are added.The organic phase, i.e. the second liquid phase contains a carboxylation catalyst and can be recycled.By the aqueous phase, i.e. the first liquid phase, aliquots are collected, centrifuged and passed through 1 H-NMR analysis was used to determine TON. 1 H-NMR spectrum showed that the aqueous phase contained unsaturated carboxylic acid salt (sodium acrylate), alcohol by-product and water (see Figure 1 ). All volatiles were removed from the aqueous phase in vacuo to give the desired sodium acrylate as a residue. The residue was dissolved in D2O and tested for the second 1 H-NMR spectrum. 1 The absence of resonances of the methyl protons of the alcohol in the H-NMR spectrum indicates that isopropanol or tert-butanol by-products are quantitatively removed upon evaporation of the aqueous phase.

[0059] Table 1

[0060] Example Transition metal source (mmol) Alkoxide (mmol) Ligand (mmol) Ethylene (bar) <![CDATA[CO2 (bar)]]> Solvent (ml) Time (h) Temperature(℃) TON 1 <![CDATA[Pd(OAc)2(0.1)]]> NaOtBu(20) Ligand II (0.11) 10 40 DMAc(30) 20 145 60 2 <![CDATA[Pd(OAc)2(0.1)]]> NaOtBu(20) Ligand II (0.11) 10 40 NMP(30) 20 145 62 3 <![CDATA[Pd(OAc)2(0.1)]]> NaOtBu(20) Ligand II (0.11) 10 40 DMI(30) 20 145 90 4 <![CDATA[Pd(OAc)2(0.1)]]> NaOtBu(20) Ligand II (0.11) 10 40 NEP(30) 20 145 70 5 <![CDATA[Pd(OAc)2(0.1)]]> NaOtBu(20) Ligand II (0.11) 10 40 DBF(30) 20 145 180 6 <![CDATA[Pd(OAc)2(0.1)]]> NaOtBu(20) Ligand II (0.11) 10 40 CHP(30) 29 145 390 7 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand II (0.011) 10 40 CHP(30) 5 145 300 8 <![CDATA[PdCl2(0.01)]]> NaOiPr(25) Ligand II (0.011) 10 40 CHP(30) 20 145 160 9 <![CDATA[PdCl2(0.2)]]> NaOtBu(15) Ligand II (0.22) 10 40 DBF(30) 20 145 60 10 <![CDATA[PdCl2(0.2)]]> NaOiPr(15) Ligand II (0.22) 10 40 DBF(30) 20 145 70 11 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand II (0.011) 10 40 CHP(30) 20 145 526 12 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand II (0.011) 10 40 DBF(30) 106 145 300 13 <![CDATA[PdCl2(0.2)]]> NaOtBu(25) Ligand II (0.22) 10 40 DBF(30) 20 145 180

[0061] Examples 14-19 (Raw material types, dosages and reaction conditions are shown in Table 2)

[0062] In the 60mL steel autoclave in the glove box, add transition metal source, ligand and alkoxide and the solid mixture obtained is dissolved in the solvent.Autoclave is taken out from the glove box and under 700rpm stirring and at 25 ℃, 10 bar ethylene and 30 bar carbon dioxide are added.After stirring at 700rpm and 145 ℃ of temperature, autoclave is cooled to 20 ℃, releases pressure and reactant mixture, i.e. crude reaction product is transferred to a 100mL glass bottle.Residue in the autoclave container is reclaimed and transferred to a glass bottle with 30mL H o.By water, i.e. the first liquid phase collects aliquots, uses H pO acidification and is analyzed by HPLC to measure TON.HPLC chromatogram shows that water contains acetic acid, which is the acid formed by acidification carboxylation product (acrylate).

[0063] Table 2

[0064] Example Transition metal source (mmol) Alkoxide (mmol) Ligand (mmol) Ethylene (bar) <![CDATA[CO2 (bar)]]> Solvent (ml) Time (h) Temperature(℃) TON 14 <![CDATA[Ni(COD)2(0.1)]]> NaOtBu(5) Ligand II (0.11) 10 30 DBF(30) 16 145 26 15 <![CDATA[NiCOD)2(0.2)]]> NaOtBu(20) Ligand II (0.22) 10 30 DBF(30) 16 145 30 16 <![CDATA[Ni(COD)2(0.1)]]> NaOsecBu(5) Ligand II (0.11) 10 30 DBF(30) 16 145 20 17 <![CDATA[Ni(COD)2(0.1)]]> NaOiPr(5) Ligand II (0.11) 10 30 DBF(30) 16 145 38 18 <![CDATA[Ni(COD)2(0.1)]]> NaOCy(5) Ligand II (0.11) 10 30 DBF(30) 16 145 20 19 <![CDATA[Ni(COD)2(0.1)]]> NaOCy(5) Ligand II (0.11) 10 30 DBF(30) 16 145 6

[0065] Examples 20-24 (Raw material types, dosages and reaction conditions are shown in Table 3)

[0066] In the 60mL steel autoclave in the glove box, add transition metal source, other ligands except II and alkoxide and the solid mixture obtained is dissolved in the solvent.The autoclave is taken out from the glove box and 10 bar ethylene and 40 bar carbon dioxide are added under 800rpm stirring and at 25 ℃.After stirring at 800rpm and 145 ℃ of temperature, the autoclave is cooled to 20 ℃, the pressure is released and the reaction mixture, i.e. the crude reaction product is transferred to a 100mL glass bottle.The residue in the autoclave container is recovered and transferred to a glass bottle with 15mL D2O.In this two-phase mixture, 3-(trimethylsilyl)-2,2,3,3-d4 propionic acid sodium salt (0.13mmol, 0.0216g), additional 10mL D2O and 40mL Et2O are added.The organic phase, i.e. the second liquid phase contains a carboxylation catalyst and can be recycled.By the aqueous phase, i.e. the first liquid phase, aliquots are collected, centrifuged and passed through 1 H-NMR analysis was used to determine TON. 1 H-NMR spectrum showed that the aqueous phase contained unsaturated carboxylic acid salt (sodium acrylate), alcohol byproduct and water. All volatiles were removed from the aqueous phase in vacuo to obtain the desired sodium acrylate as a residue. The residue was dissolved in D2O and tested for the second 1 H-NMR spectrum. 1 The absence of resonances of the methyl protons of the alcohol in the H-NMR spectrum indicates that isopropanol or tert-butanol by-products are quantitatively removed upon evaporation of the aqueous phase.

[0067] Table 3

[0068] Example Transition metal source (mmol) Alkoxide (mmol) Ligand (mmol) Ethylene (bar) <![CDATA[CO2 (bar)]]> Solvent (ml) Time (h) Temperature(℃) TON 20 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand III (0.11) 10 40 CHP(30) 20 145 206 21 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand IV (0.11) 10 40 CHP(30) 20 145 362 22 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand v (0.11) 10 40 CHP(30) 20 145 560 23 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand VI (0.11) 10 40 CHP(30) 20 145 270 24 <![CDATA[PdCl2(0.01)]]> NaOtBu(25) Ligand VII (0.11) 10 40 CHP(30) 20 145 532

[0069] Comparative Example 1

[0070] With ethylene and carbon dioxide as co-components, when the pressures of C2H4 and CO2 are 10 bar and 40 bar respectively and the reaction temperature is 145°C, alkoxide, reducing agent and additives are added, and TON can reach 24 within 20-25 hours. The role of the reducing agent is to convert the by-product Pd 2 +Restore to Pd 0 The specific parameters are compared with those of Example 22 of the present invention as shown in Table 4.

[0071] Table 4

[0072] catalyst Ligand reducing agent Alkoxide additive Solvents TON Comparative Example Pd complexes dcpe Trisodium Citrate NeA Triphenylphosphine CHP 24 The present invention <![CDATA[PdCl2]]> Ligand V none NeA none CHP 560

[0073] The advantage of the present invention is that the new ligand with strong coordination and strong electron-donating ability can effectively inhibit the formation of by-products, thereby realizing the one-step preparation of sodium acrylate without adding a reducing agent. At the same time, the maximum conversion number of the catalyst composition of the present invention is as high as 560.

[0074] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A catalyst composition for preparing unsaturated carboxylic acid salts from carbon dioxide and ethylene, characterized in that: The raw materials of the catalyst composition include, by weight: 1 part of ligand, 0.5-2 parts of metal source catalyst and 50-400 parts of alkoxide; the structural formula of the ligand is shown in any one of Formula II to Formula VII: ； The metal source catalyst is a palladium source catalyst; the palladium source catalyst is PdCl2 or [Pd(OAc)2]; the alkoxide is isopropoxide or tert-butoxide.

2. A method for preparing unsaturated carboxylates by one-step reaction of carbon dioxide and ethylene, characterized in that: The following steps are involved: The catalyst composition according to claim 1 is dissolved in a solvent to obtain a mixture; ethylene and carbon dioxide are added to the mixture for reaction to obtain an unsaturated carboxylate.

3. The method according to claim 2, characterized in that The molar ratio of ethylene to carbon dioxide is 1:2-4.

4. The method according to claim 2, characterized in that: The reaction temperature is 100° C.-180° C., and the reaction time is 10-25 hours.

5. The method according to claim 2, characterized in that: The solvent is an aprotic organic solvent.

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