A method for preparing 1,4-butanediol from ethylene glycol through electrocatalysis

Abstract

The present invention relates to a method for preparing 1,4-butanediol from ethylene glycol via 2-haloethanol. The method uses ethylene glycol as a raw material and first undergoes acid-catalyzed halogenation to obtain 2-haloethanol and 2-haloethanol acetate. The 2-haloethanol and 2-haloethanol acetate mixture is then converted into 1,4-butanediol and its ester via electrocatalytic dehalogenation coupling. The halogenation reaction uses a strong acid as a catalyst and is heated under an inert atmosphere to obtain 2-haloethanol and 2-haloethanol acetate with a total selectivity of up to 89%. The electrocatalytic reaction of the 2-haloethanol and 2-haloethanol acetate after the reaction is as follows: 2-iodoethanol and 2-haloethanol acetate, a metal complex, and a base are added to an electrolytic cell containing a solvent, wherein a Pt electrode and an oxide electrode serve as cathodes. The electrolytic cell atmosphere is replaced with an inert gas, sealed, and electrolyzed at room temperature to obtain 1,4-butanediol and 1,4-butanediol diacetate, the products of the dehalogenation coupling of 2-iodoethanol and 2-haloethanol acetate, with a selectivity of up to 91%. The overall 1,4-butanediol selectivity of the two-step process can reach 81%.

Description

Technical Field

[0001] The present invention relates to a method for preparing 1,4-butanediol by electrocatalytic ethylene glycol, and specifically relates to a two-step method for preparing 1,4-butanediol, comprising the steps of: halogenating ethylene glycol catalyzed by Amberlyst 15 acid to prepare 2-haloethanol / 2-haloethanol acetate; and preparing 1,4-butanediol and its diacetate by electrocatalytic dehalogenation coupling of 2-haloethanol / 2-haloethanol acetate. Background Art

[0002] 1,4-Butanediol (BDO) is an important fine chemical raw material, used in the production of key chemicals such as γ-butyrolactone, tetrahydrofuran, polyurethane resins, and biodegradable plastics. Due to its significant application value, various methods for its preparation have been developed.

[0003]

[0004] Currently, the primary industrial production method for BDO is the acetylene-aldehyde process. Formaldehyde and ethylene react under high pressure to produce butynediol, which is then hydrogenated in two steps to produce BDO. This process leverages my country's abundant coal resources, utilizing coal to produce coke, which is then used with limestone to produce acetylene, offering significant advantages. However, this process emits coke oven gas during the coal coking process, carbide furnace exhaust gas during the production of calcium carbide, and carbide slag during the production of acetylene from calcium carbide. From the perspective of reducing pollution at the source, the production of BDO by the carbide process is highly polluting, with high emissions and high energy consumption.

[0005] The effective utilization of biomass resources can reduce our dependence on fossil fuels. Converting biomass into high value-added products has important economic and environmental significance. In recent years, researchers have developed many methods for preparing BDO from biomass-based materials. Li et al. used 1,4-dioxane as solvent and Cu2Co1 / Al2O3 catalyst to achieve a highly selective conversion of γ-butyrolactone to BDO at 170 ° C and 5 MPa H2 (ACS Catal. 2017, 7, 7890-7901). Liu et al. used FeO xOver a modified Pd / C catalyst, succinic acid was hydrogenated at 200°C and 5 MPa H2 to produce BDO with a yield exceeding 70% (J. Mater. Chem. A, 2015, 3, 23560-23569). Li et al. converted furfural to BDO in a one-pot reaction over a Pt / TiO2-ZrO2 catalyst with a yield of 85.2% (Appl. Catal. A, 2014, 478, 252-258). Zhu et al. converted furfural-derived furan carboxylic acid to 1,4-butanediol diacetate in a one-pot reaction over a Pd / C and La(OTF)3 co-catalyst system at 180°C and 2 MPa H2, followed by simple hydrolysis to obtain BDO (Appl. Catal. A, 2020, 608, 117888). Yasushi Amada et al. used erythritol to synthesize BDO in the presence of Ir-ReO x A new method for preparing BDO from biomass was developed by direct hydrogenolysis over SiO2 catalyst (ChemSusChem, 2012, 5, 1991-1999).

[0006] While existing preparation methods are diverse, they often suffer from high energy consumption and severe pollution. Developing new BDO preparation methods to meet China's demand for a green, low-carbon economy is an urgent task. Ethylene glycol is a key chemical product. In recent years, my country has made breakthroughs in coal-based ethylene glycol technology, and biomass-based ethylene glycol technology has also significantly advanced, jointly driving the ethylene glycol industry chain. Currently, ethylene glycol production capacity is in excess, and converting it into BDO will help regulate the supply and demand relationship between ethylene glycol and BDO. Summary of the Invention

[0007] The present invention relates to a two-step method for preparing BDO from ethylene glycol via 2-haloethanol and 2-haloethanol acetate. An acid-catalyzed substitution reaction between ethylene glycol and an inorganic halide dehydroxylates the ethylene glycol and creates an activated β-carbon center. Subsequently, a metal complex-catalyzed reductive coupling of the 2-haloethanol and 2-haloethanol acetate is performed electrocatalytically. The key to preparing BDO from ethylene glycol lies in removing the hydroxyl groups from the ethylene glycol to produce a carbon radical intermediate. The present invention facilitates the formation of the carbon radical intermediate by first halogenating the hydroxyl groups to form readily leaving halogen groups. The 2-haloethanol can undergo an acid- or base-catalyzed side reaction at room temperature to produce polymers such as polyethylene glycol. Stable and selective coupling of the 2-haloethanol and 2-haloethanol acetate is a key technical challenge.

[0008] The technical solution used in the present invention is:

[0009] Ethylene glycol is converted to BDO in a two-step process via the following reaction process:

[0010]

[0011] An acid catalyst, ethylene glycol, and one or more of HX, NaX, or KX are added to a reactor. After replacing the reactor with nitrogen or argon, the reaction is stirred at 60-90°C for 0.25-20 hours. Amberlyst 15 is filtered to obtain 2-haloethanol and 2-haloethanol acetate. The separated and purified 2-haloethanol and 2-haloethanol acetate, a metal complex, a reducing agent, a base, and a solvent are added to a diaphragmless electrolytic cell with a Pt electrode as the cathode and an oxide semiconductor as the anode. The oxide semiconductor electrode is prepared by spin-coating an aqueous dispersion of TiO2 and / or Nb2O5 onto FTO (fluorine-doped tin oxide) conductive glass and calcining it in air at 400°C for 2 hours. The atmosphere in the photoreactor is replaced with one or both of N2 and Ar, sealed, and subjected to electrolysis for 0.5-10 hours. BDO is thus obtained.

[0012] In order to realize the process of preparing 2-haloethanol and 2-haloethanol acetate from ethylene glycol in the above scheme, the acid catalyst is Amberlyst 15, which is a polymer of vinylbenzenesulfonic acid and divinylbenzene, and the amount thereof is 5 to 500 g L -1 The inorganic halide is one or two of HBr, NaBr, KBr, HI, NaI or KI, and the preferred halide is one or two of HI and NaI; the amount thereof is 0.1 to 2.0 mol L -1 .

[0013] The iodination reaction of ethylene glycol consumes H + Therefore, the requirements for acid when using HI or NaI are different. When the inorganic halide is HI, the preferred amount of Amberlyst15 is 5 to 20 g L -1 The preferred amount of halide is 0.5 to 1.0 mol / L -1 , the preferred reaction time is 1 to 3 hours; and when the inorganic halide is NaI, the preferred amount of Amberlyst15 is 50 to 200 g L -1 The preferred amount of halide is 0.4 to 0.8 mol L -1 , the preferred reaction time is 2 to 6 hours.

[0014] In order to realize the electrocatalytic dehalogenation coupling of 2-haloethanol and 2-haloethanol acetate to produce BDO in the above scheme, the total concentration of 2-haloethanol and 2-haloethanol acetate is 0.02-1.0 mol L -1 The oxide semiconductor electrode is one or both of TiO2 and Nb2O5, and the amount used is 0.1 to 2 mg cm based on the anode area of ​​the electrolytic cell. -1The reducing agent is one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, triethanolamine, triethylamine, sodium formate, sodium oxalate and ammonium oxalate; the base is one or more of Na2CO3, K2CO3, KHCO3, sodium acetate, potassium acetate, Na3PO4 and Na2HPO4, and its concentration is 0.1-0.4 mol L -1 The solvent is acetonitrile or N,N-dimethylformamide; the current density is 5 to 250 mA cm -2 .

[0015] Because the electrocatalytic dehalogenation coupling of 2-haloethanol and 2-haloethanol acetate to produce BDO involves a reduction process, a reducing agent is required. The amount of reducing agent used varies significantly depending on the type of reducing agent. Therefore, when the reducing agent is one or more of methanol, ethanol, n-propanol, isopropanol, and ethylene glycol, the amount used is 1 to 100 vol%. Here, 100% represents the addition of only the reducing agent without a solvent. When the reducing agent is one or more of triethanolamine, triethylamine, sodium formate, sodium oxalate, and ammonium oxalate, the amount used is 1 to 10 times the amount of 2-haloethanol and 2-haloethanol acetate.

[0016] The role of TiO2 and Nb2O5 anode is to provide redox agents for the coupling of 2-haloethanol and 2-haloethanol acetate. In order to control the selective coupling of β-hydroxyethyl radicals generated by the reduction of 2-haloethanol to produce BDO. 2+ The complex can react with β-hydroxyethyl radicals to avoid reaction with H· on the semiconductor surface, thereby causing β-hydroxyethyl radicals to self-couple to obtain BDO. Here, the metal complex is Ni 2+ Metal complexes formed by coordination with pyridine ligands, in which Ni 2+ The precursor salt is one or both of NiCl2 and NiBr2; the pyridine complex is a tridentate nitrogen-centered coordination ligand, comprising the following structure:

[0017]

[0018] One or more of the 11 H groups in the three aromatic rings may be substituted by other groups or atoms.

[0019] The Ni 2+ The ratio of Ni to pyridine ligand is 0.5~20, 2+ It is 0.05 to 5 mol% of the total amount of 2-haloethanol and 2-haloethanol acetate.

[0020] The method for preparing BDO proposed in this invention utilizes ethylene glycol, a readily available, inexpensive raw material from the coal chemical industry, as a raw material, significantly different from existing technologies. The core of this invention lies in two key aspects: 1. Through halogenation, ethylene glycol is dehydroxylated, and in a second step, β-hydroxyethyl radicals are formed. Because the α-CH bond of the alcoholic hydroxyl group is highly reactive, the formation of this reactive radical species is very limited. Another key aspect of this invention is the use of electrocatalysis to couple 2-haloethanol with 2-haloethanol acetate. While related papers and patents report dehalogenation coupling methods for halogenated hydrocarbons and halogenated aromatic hydrocarbons, the 2-haloethanol described in this invention is highly reactive due to the presence of hydroxyl groups, allowing it to be converted to oligomers and other byproducts through thermal reactions at room temperature. Furthermore, 2-haloethanol and 2-haloethanol acetate may react with the abundant H radicals present in the reaction to produce ethanol as a byproduct. Therefore, increasing the reduction rate of 2-haloethanol and controlling the reaction selectivity of the β-hydroxyethyl radical are other key issues of this invention. The present invention transfers cathode electrons to 2-haloethanol through a metal complex to achieve the cleavage of the carbon-halogen bond, thereby generating a β-hydroxyethyl free radical. In addition, the metal complex can also react with the β-hydroxyethyl free radical to prevent the β-hydroxyethyl free radical from interacting with H· on the semiconductor surface, thereby achieving self-coupling of the β-hydroxyethyl free radical to obtain BDO.

[0021] Compared with existing methods for preparing BDO, the present invention has the following advantages:

[0022] (1) BDO is obtained from readily available ethylene glycol via 2-iodoethanol;

[0023] (2) The reaction conditions are mild, and the reaction temperature is below 110°C;

[0024] (3) The catalyst has high activity, the conversion rate can reach 100%, and the highest total selectivity is 81%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a chromatogram of the results of the ethylene glycol dehydroxylation reaction in Example 2. Among them, the retention time 3.827 min is acetic acid; 4.248 min is the internal standard hexanediol dimethyl ether; 4.617 min is ethylene glycol; 5.409 min is iodine; 6.437 min is ethylene glycol monoethyl ester; 6.561 min is 2-iodoethanol; 8.393 min is 2-iodoethanol acetate.

[0026] Figure 2 This is a chromatogram of the electrocatalytic coupling of 2-iodoethanol to BDO in Example 8. Retention time 3.1 min indicates ethanol; 3.3 min indicates acetonitrile; 4.5 min indicates the internal standard, ethylene glycol dimethyl ether; 7.5 min indicates 2-iodoethanol; 8.9 min indicates 1,4-butanediol; and 11.5 min indicates the internal standard, 1,4-dibromobutane. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0028] Example 1

[0029] The volume of the solvent was 0.1 mol L -1 of ethylene glycol, 100g L -1 Amberlyst15 and 1.2 equivalents of NaI (0.12 mol L -1 ) was added to a polytetrafluoroethylene liner containing 2 ml of acetonitrile. A magnetic stirrer was added, the reaction atmosphere was sealed, and nitrogen was replaced. The reaction was heated at 90°C for 10 hours. After completion of the reaction, GC analysis revealed a 68% conversion of ethylene glycol and a 71% overall selectivity for 2-iodoethanol and 2-iodoethanol acetate (separated by column chromatography to obtain 2-haloethanol and 2-haloethanol acetate).

[0030] Example 2

[0031] The volume of the solvent was 0.1 mol L -1 of ethylene glycol, 100g L -1 Amberlyst 15 and 2.0 equivalents of NaI (0.20 mol L -1 ) was added to a polytetrafluoroethylene liner containing 2 ml of acetonitrile. A magnetic stirrer was added, the reaction atmosphere was sealed, and nitrogen was replaced. The reaction was heated at 90°C for 10 hours. After completion of the reaction, GC analysis revealed a conversion of ethylene glycol of 75%, and a total selectivity of 2-iodoethanol and 2-iodoethanol acetate of 89%. (2-haloethanol and 2-haloethanol acetate were separated by column chromatography.)

[0032] Example 3

[0033] The volume of the solvent was 0.1 mol L -1 of ethylene glycol, 100g L -1 Amberlyst15 and 2.7 equivalents of NaI (0.27 mol L -1 ) was added to a polytetrafluoroethylene-lined container containing 2 ml of acetonitrile. A magnetic stirrer was added, the reaction atmosphere was sealed, and nitrogen was replaced with nitrogen. The reaction was heated at 90°C for 10 hours. After completion of the reaction, GC analysis revealed an ethylene glycol conversion of 84%, and a total selectivity of 2-iodoethanol and 2-iodoethanol acetate of 69%. (2-haloethanol and 2-haloethanol acetate were separated by column chromatography.)

[0034] Example 4

[0035] The volume of the solvent was 0.1 mol L -1 of ethylene glycol, 200g L -1 Amberlyst15 and 1.2 equivalents of NaI (0.12 mol L -1 ) was added to a polytetrafluoroethylene-lined container containing 2 ml of acetonitrile. A magnetic stirrer was added, the reaction atmosphere was sealed, and nitrogen was replaced with nitrogen. The reaction was heated at 90°C for 10 hours. After completion of the reaction, GC analysis revealed an ethylene glycol conversion of 83%, and a total selectivity of 71% for 2-iodoethanol and 2-iodoethanol acetate (2-haloethanol and 2-haloethanol acetate were separated by column chromatography).

[0036] Example 5

[0037] The volume of the solvent was 0.1 mol L -1 of ethylene glycol, 100g L -1 Amberlyst 15 and 2.0 equivalents of NaI (0.20 mol L -1 ) was added to a polytetrafluoroethylene-lined container containing 2 ml of acetonitrile. A magnetic stirrer was added, the reaction atmosphere was sealed, and nitrogen was replaced with nitrogen. The reaction was heated at 90°C for 1 hour. After completion of the reaction, GC analysis revealed a 56% conversion of ethylene glycol and a 59% overall selectivity for 2-iodoethanol and 2-iodoethanol acetate (separated by column chromatography to obtain 2-haloethanol and 2-haloethanol acetate).

[0038] Example 6

[0039] The volume of the solvent was 0.1 mol L -1 of ethylene glycol, 100g L -1 Amberlyst 15 and 2.0 equivalents of NaI (0.20 mol L -1 ) was added to a polytetrafluoroethylene-lined container containing 2 ml of acetonitrile. A magnetic stirrer was added, the reaction atmosphere was sealed, and nitrogen was replaced with nitrogen. The reaction was heated at 90°C for 4 hours. After completion of the reaction, GC analysis revealed a 77% conversion of ethylene glycol and a 72% overall selectivity for 2-iodoethanol and 2-iodoethanol acetate (separated by column chromatography to obtain 2-haloethanol and 2-haloethanol acetate).

[0040] Example 7

[0041] The volume of the solvent was 0.1 mol L -1 of ethylene glycol, 100g L -1 Amberlyst 15 and 2.0 equivalents of NaI (0.20 mol L -1) was added to a polytetrafluoroethylene liner containing 2 ml of acetonitrile. A magnetic stirrer was added, the reaction atmosphere was sealed, and nitrogen was replaced. The reaction was heated at 90°C for 6 hours. After completion of the reaction, GC analysis revealed an ethylene glycol conversion of 81%, and an overall selectivity of 84% for 2-iodoethanol and 2-iodoethanol acetate (2-haloethanol and 2-haloethanol acetate were obtained after column chromatography separation).

[0042] The preparation method of the oxide semiconductor electrode (P25 anode) in the following embodiment is as follows: P25 (TiO2) aqueous dispersion is loaded on FTO (fluorine-doped tin oxide) conductive glass by spin coating and calcined in air at 400℃ for 2h; based on the surface area of ​​the electrolytic cell anode, the TiO2 coating is 1.0mg cm -1 .

[0043] Example 8

[0044] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the volume of the solvent) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL of methanol and 45 mL of acetonitrile (solvent). The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 80%.

[0045] Example 9

[0046] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.4 mol L -1 % CH3COONa (relative to the solvent volume), 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2The electrolysis was carried out for 3 hours with a current of 100 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 98%, and the selectivity of 1,4-butanediol was 77%.

[0047] Example 10

[0048] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.4 mol L -1 (relative to the solvent volume) NaHCO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 100 μg / min (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion rate of 2-iodoethanol was 75%, and the yield of 1,4-butanediol was 83%.

[0049] Example 11

[0050] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2HPO4, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL of methanol and 45 mL of acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 78%.

[0051] Example 12

[0052] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.05 mol L -1(relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 100 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 92%, and the selectivity of 1,4-butanediol was 73%.

[0053] Example 13

[0054] 0.1 mol L -1 (relative to the volume of the solvent) 2-iodoethanol, 0.1 mol L -1 (relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 83%.

[0055] Example 14

[0056] 0.2 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 1 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.2 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2The electrolysis was carried out for 6 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 80%.

[0057] Example 15

[0058] 0.5 mol L -1 (relative to the volume of the solvent) 2-iodoethanol, 0.5 mol L -1 (relative to the volume of the solvent) Na2CO3, 0.8 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.8 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL of methanol and 45 mL of acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 100 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 7 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 75%.

[0059] Example 16

[0060] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 20 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 7 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 87%.

[0061] Example 17

[0062] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1(relative to the solvent volume) Na2CO3, 4 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 100 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 1.5 hours with a current of 1.5°C (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 78%.

[0063] Example 18

[0064] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 10 mL methanol and 40 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 79%.

[0065] Example 19

[0066] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the volume of the solvent) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in 5 equivalents of triethanolamine (0.5 mol L -1 ) and 50 mL of acetonitrile. Seal the electrolytic cell (added to the same electrolytic cell body) and then replace it with N2 three times to remove O2. -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 81%.

[0067] Example 20

[0068] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) 4-methoxyterpyridine were dispersed in a mixture of 10 mL methanol and 40 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 72%.

[0069] Example 21

[0070] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) 4-chloroterpyridine were dispersed in a mixture of 10 mL methanol and 40 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC. The conversion rate of 2-iodoethanol was 83%, and the yield of 1,4-butanediol was 62%.

[0071] Example 22

[0072] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1(relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 1 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 83%.

[0073] Example 23

[0074] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) of Na2CO3, 2 mol% (relative to 2-iodoethanol) of NiCl2·6H2O, and 2 mol% (relative to 2-iodoethanol) of terpyridine were dispersed in a mixture of 5 mL of methanol and 45 mL of acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 86%.

[0075] Example 24

[0076] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 0.4 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL of methanol and 45 mL of acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 10 mA cm is applied in a single electrolytic cell. -2The electrolysis was carried out for 14 hours with a current of 100 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 91%.

[0077] Example 25

[0078] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 5 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 5 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL of methanol and 45 mL of acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 200 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 40 minutes with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 95%, and the selectivity of 1,4-butanediol was 73%.

[0079] Example 26

[0080] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) Nb2O5 is the anode and Pt sheet is the cathode. In a single electrolytic cell, 20 mA cm -2 The electrolysis was carried out for 7 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 77%.

[0081] Example 27

[0082] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol, 0.2 mol L -1(relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol) CuCl2, and 0.4 mol% (relative to 2-iodoethanol) terpyridine were dispersed in a mixture of 5 mL methanol and 45 mL acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 61%.

[0083] Example 28

[0084] 0.1 mol L -1 (relative to the volume of solvent) 2-iodoethanol acetate, 0.2 mol L -1 (relative to the solvent volume) Na2CO3, 2 mol% (relative to 2-iodoethanol acetate) NiCl2·6H2O, and 0.4 mol% (relative to 2-iodoethanol acetate) terpyridine were dispersed in a mixture of 5 mL of methanol and 45 mL of acetonitrile. The electrolytic cell was sealed (added to the same cell body) and then purged with N2 three times to remove O2. 1.0 mg cm -2 (relative to the anode area) P25 is the anode and the Pt sheet is the cathode. 50 mA cm is applied in a single electrolytic cell. -2 The electrolysis was carried out for 3 hours with a current of 1000 nm (relative to the anode area). After the reaction, the products were quantified by GC, and the conversion of 2-iodoethanol was 100%, and the selectivity of 1,4-butanediol was 86%.

[0085] Example results description:

[0086] 1. Comparison of Examples 1 to 3 shows that when the addition amount of Amberlyst 15 is constant and the ratio of sodium iodide to ethylene glycol is 2, the optimal selectivity is 89%;

[0087] 2. Comparison of Examples 5 to 7 shows that the conversion of ethylene glycol is faster when the reaction time is 1 h, and slower when the reaction time is 4 to 6 h;

[0088] 3. Comparison of Examples 8 to 11 shows that the type of base has a certain influence on the rate and selectivity of the 2-iodoethanol coupling reaction, and the bases in the examples have a similar promoting effect on the reaction;

[0089] 4. Comparison of Examples 8, 12, and 13 shows that when the equivalent of the base is in excess relative to 2-iodoethanol, the selectivity for 1,4-butanediol is low;

[0090] 5. Comparison of Examples 13 to 15 shows that the 2-iodoethanol coupling method can be used with a higher 2-iodoethanol reaction concentration;

[0091] 6. Comparison of Examples 8, 16, 17, 24 and 25 shows that the 2-iodoethanol coupling method can be implemented in a wide range of electrolytic concentrations, but high currents can easily cause catalyst deactivation, thus requiring a higher terpyridine concentration to stabilize Ni. 2+ catalyst;

[0092] 7. Comparison of Examples 8, 18, and 19 shows that the 2-iodoethanol coupling method is less affected by the concentration and type of the reducing agent;

[0093] 8. Comparison of Examples 8, 20, and 21 shows that the optimal terpyridine ligand is terpyridine;

[0094] 9. Comparison of Examples 8 and 26 shows that the photoanodes of Nb2O5 and TiO2 have comparable activity and selectivity;

[0095] 10. Comparing Examples 8 and 27, it can be seen that NiCl2·6H2O has better selectivity for 1,4-butanediol than CuCl2.

Claims

1. A method for electrocatalytically preparing 1,4-butanediol from ethylene glycol, characterized by: Using ethylene glycol as raw material, ethylene glycol is first converted into 2-haloethanol and 2-haloethanol acetate, and then 2-haloethanol and 2-haloethanol acetate are converted into 1,4-butanediol and 1,4-butanediol diacetate; wherein the halide is a halide ion Br − or I − The specific process is as follows: adding a solvent, an acid catalyst, ethylene glycol, and an inorganic halide to a reactor; replacing the atmosphere in the reactor with nitrogen and / or argon, stirring and reacting at 60-120°C for 0.25-20 hours; obtaining 2-haloethanol and 2-haloethanol acetate by column chromatography, wherein the inorganic halide is one or more of HX, NaX, or KX; adding one or more of 2-haloethanol and 2-haloethanol acetate, a metal complex, a reducing agent, a base, and a solvent to a diaphragmless electrolytic cell, wherein the cathode of the electrolytic cell is a Pt electrode and the anode is an oxide semiconductor electrode; replacing the atmosphere in the electrolytic cell with one or more of N2 and Ar, sealing the cell, and conducting an electrolytic reaction for 0.5-10 hours; the main products are 1,4-butanediol and 1,4-butanediol diacetate; The following reactions are involved: ； Where X represents a halogen, the inorganic halide is in the form of HX, NaX or KX, and the halide ion is Br − or I − One or two of the acid catalyst is Amberlyst15, ie, a polymer of vinylbenzenesulfonic acid and divinylbenzene, the metal complex is Ni 2+ Metal complexes formed by coordination with pyridine ligands, in which Ni 2+ The precursor salt is one or both of NiCl2 and NiBr2; the pyridine complex is a tridentate nitrogen-centered coordination ligand, the oxide semiconductor electrode is one or both of TiO2 and Nb2O5, and the base is one or more of Na2CO3, K2CO3, KHCO3, sodium acetate, potassium acetate, Na3PO4 and Na2HPO4.

2. The method according to claim 1, wherein: The amount of the acid catalyst relative to the solvent volume is 5-500 g L -1 ; The inorganic halide is one or two of HBr, NaBr, KBr, HI, NaI or KI, and its amount relative to the solvent volume is 0.05-2.0 mol L -1 ; The solvent is acetonitrile and / or N,N-dimethylformamide.

3. The method according to claim 2, wherein: When the inorganic halide is HBr or HI, the amount of Amberlyst 15 used is 5-20 g L relative to the solvent volume. -1 , the reaction time is 1~3 h; When the inorganic halide is NaBr, KBr, NaI or KI, the amount of Amberlyst 15 used is 50-200 g L relative to the solvent volume. -1 The amount of halide used relative to the solvent volume is 0.1~0.4 mol L -1 , the reaction time is 2~6 h.

4. The method according to claim 1, wherein The steps include: The total concentration of the 2-haloethanol and 2-haloethanol acetate relative to the solvent volume is 0.02-1.0 mol L -1 ; The oxide semiconductor electrode is prepared by spin coating a TiO2 and / or Nb2O5 aqueous dispersion onto FTO (fluorine-doped tin oxide) conductive glass and calcining the solution in air at 400-500°C for 2-4 hours. The amount of TiO2 and / or Nb2O5 applied is 0.1-2.0 mg cm based on the surface area of ​​the electrolytic cell anode. -2 ; The reducing agent is one or more of methanol, ethanol, n-propanol, isopropanol, ethylene glycol, triethanolamine, triethylamine, sodium formate, sodium oxalate and ammonium oxalate; The concentration of the base relative to the solvent volume is 0.05~1 mol L -1 ; The solvent is acetonitrile and / or N,N-dimethylformamide; The current applied between the anode and cathode of a single electrolytic cell is 5~500 mA cm -2 .

5. The method according to claim 4, characterized in that: When the reducing agent is one or more of methanol, ethanol, n-propanol, isopropanol and ethylene glycol, the amount thereof is 1 to 100 vol% of the sum of the volumes of the reducing agent and the solvent. In this case, the relative solvent volume used in calculating the concentrations of the raw materials and the base is the sum of the volumes of the reducing agent and the solvent. Wherein, the amount of the reducing agent of 100 vol% represents the case where only the reducing agent is added without the solvent, that is, the reducing agent is used as both the reducing agent and the solvent. When the reducing agent is one or more of triethanolamine, triethylamine, sodium formate, sodium oxalate and ammonium oxalate, the amount thereof is 1 to 10 times the total molar amount of 2-haloethanol and 2-haloethanol acetate.

6. The method according to claim 5, characterized in that: The metal complex is Ni 2+ Metal complexes formed by coordination with pyridine ligands, in which Ni 2+ The precursor salt is one or both of NiCl2 and NiBr2; the pyridine complex is a tridentate nitrogen-centered coordination ligand, comprising the following structure: ； One or more of the 11 H groups in the three aromatic rings are substituted by one or two methyl, methoxy or halogen functional groups.

7. The method according to claim 6, characterized in that: The Ni 2+ The molar ratio of Ni to pyridine ligand is 0.5~20. 2+ It is 0.1 to 10 mol% of the total molar amount of 2-haloethanol and 2-haloethanol acetate.

8. The method according to claim 6, wherein: The Ni 2+ The molar ratio of Ni to pyridine ligand is 1~10. 2+ It is 0.5 to 5 mol% of the total molar amount of 2-haloethanol and 2-haloethanol acetate.

9. The method according to claim 8, characterized in that: The Ni 2+ The molar ratio of Ni to pyridine ligand is 2~5, 2+ It is 1 to 3 mol% of the total molar amount of 2-haloethanol and 2-haloethanol acetate.

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