An electrochemical process for the production of 1, 4-butanediol

Abstract

The application discloses an electrochemical method for preparing 1,4-butanediol. The electrochemical method for preparing 1,4-butanediol comprises the following steps: 1,4-butanediol is prepared by electrolytic reduction of bromoethanol in an electrolyte; wherein, the pH of the electrolyte is greater than or equal to 7.0; a copper-containing material is used as a working electrode of a cathode; and the electrolyte contains ligand molecules. The application changes the reaction interface environment by adding ligands with different configurations, and realizes high-yield conversion of bromoethanol into 1,4-butanediol in an aqueous phase through electrolysis. Meanwhile, bromoethanol can be obtained by oxidation of bromide ions and addition of ethylene at an anode, and ethylene can be converted into 1,4-butanediol in the whole process, thereby improving the atomic utilization rate.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic organic synthesis and relates to an electrochemical method for preparing 1,4-butanediol. Background Technology

[0002] 1,4-Butane-1,4-diol (BDO) is an important chemical product widely used in chemical, pharmaceutical, textile, paper, automotive, and daily chemical industries. Currently, there are four main methods for BDO synthesis: First, the acetylene-aldehyde method, which is the mainstream synthesis method. Using acetylene, formaldehyde, and hydrogen as raw materials, BDO is synthesized under high temperature and pressure. This method is low-cost and mature, but acetylene is prone to polymerization during the reaction. Second, the maleic anhydride method, using n-butane as a raw material, involves oxygenation, cyclization, and then hydrogenation to obtain BDO. This method can yield various chemical products, but the process is complex and has high investment costs. Third, the butadiene method, involving the addition of butadiene to acetic acid, followed by hydrogenation and hydrolysis to obtain BDO. This method uses readily available raw materials and has a relatively mild reaction, but requires a large amount of acetic acid vapor recovery, resulting in high construction costs. Fourth, the allyl alcohol method, which involves isomerization of propylene oxide to obtain allyl alcohol, formylation, and then hydrogenation to obtain BDO. This method allows for catalyst reuse and has low energy consumption, but it has many side reactions and low product yield.

[0003] Electrocatalytic synthesis of fine chemicals has attracted widespread attention due to its advantages such as mild reaction conditions and high conversion rates. However, existing methods for electrocatalytic production of BDO have low BDO yields, making large-scale industrial production difficult.

[0004] Therefore, developing a method for large-scale industrial electrocatalytic production of BDO is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention aims to provide an electrochemical method for preparing 1,4-butanediol. This invention achieves high yield and stability on a copper foam electrode by adding ligands of different configurations to the electrolyte, thereby altering the reduction microenvironment on the electrode surface.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0007] This invention provides an electrochemical method for preparing 1,4-butanediol, comprising the following steps:

[0008] In an electrolyte, bromoethanol is electrolytically reduced to prepare 1,4-butanediol; wherein:

[0009] The electrolyte has a pH ≥ 7.0;

[0010] The working electrode of the cathode is made of copper-containing material;

[0011] The electrolyte contains ligand molecules, which are selected from one or more of the ligands shown in iv below:

[0012] i. 2-Aminoimidazole, imidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazole), 2-aminobenzimidazole, 5-aminoimidazole-4-carboxamide and L-histidine;

[0013] Pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, 2,4,5-triamino-6-hydroxypyrimidine and 2,2-bipyrimidine;

[0014] 2-Aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, 2,3-diaminopyridine, and 2,2-bipyridine;

[0015] Diethylenetriamine, pentaethylenehexamine, o-phenylenediamine, and melamine;

[0016] Pyridazine, creatinine, 1,2,4-triazole-1-methylamidine hydrochloride, 1,3,5-triazine, adenine, and guanine.

[0017] In this invention, the electrolyte generally includes an electrolyte, which is generally an electrolyte that can improve the conductivity of the solution in a chemical battery and does not participate in the electrochemical reaction itself.

[0018] As an optional implementation, the electrolyte is selected from potassium trifluoroacetate.

[0019] As an optional implementation, the concentration of the electrolyte in the electrolyte solution is 0.2-0.8M, for example, 0.5M.

[0020] As an optional implementation, the electrolyte is selected from an aqueous solution of potassium trifluoroacetate.

[0021] As an optional implementation, the electrolysis time is 0.5-5 hours, for example, 1 hour.

[0022] As an optional implementation, the electrolysis temperature is 20-30°C, for example, 25°C.

[0023] As an optional implementation, the electrolysis voltage is (-0.65~-0.35) V vs RHE, for example (-0.60~-0.40) V vs RHE, and also for example -0.60 V vs RHE, -0.55 V vs RHE, -0.50 V vs RHE, -0.45 V vs RHE, or -0.40 V vs RHE.

[0024] In a preferred embodiment, the pH of the electrolyte is 7.0-10.5, for example, pH=7.0, pH=7.5, pH=8.0, pH=8.5, pH=9.0, pH=9.5, pH=10.0 or pH=10.5.

[0025] In a preferred embodiment, the concentration of the ligand molecule in the electrolyte is 1-100 mM, for example 10 mM, 25 mM, 50 mM, 75 mM or 100 mM.

[0026] In a preferred embodiment, the concentration of bromoethanol in the electrolyte is 0.05-0.4 M, for example, 0.05 M, 0.1 M, 0.2 M, 0.3 M or 0.4 M.

[0027] In a preferred embodiment, the electrolysis voltage is -0.50 V vs RHE, the concentration of bromoethanol is 0.2 M, the concentration of the ligand is 50 mM, and the pH of the electrolyte is 9.5.

[0028] In a preferred embodiment, the ligand is 2-aminoimidazole, the electrolysis voltage is -0.50 V vsRHE, the concentration of bromoethanol is 0.2 M, the concentration of the ligand is 50 mM, and the pH of the electrolyte is 9.5.

[0029] In the electrochemical method for preparing 1,4-butanediol described in this invention, in addition to generating 1,4-butanediol, byproducts such as ethylene oxide, ethanol, and ethylene may also be generated.

[0030] In a preferred embodiment, the bromoethanol is prepared by bromoethanol by oxidation with ethylene at the anode.

[0031] The bromide ion may be the bromide ion (Br) generated in the cathode reaction. - ).

[0032] The ethylene may be ethylene generated by a cathode reaction.

[0033] The ethylene may be ethylene introduced during the reaction process.

[0034] In this invention, on the anode side, bromoethanol can be formed by bromine oxidation reaction and combination with ethylene gas, which can then be converted into bromoethanol by reacting bromide ions (Br) generated in the cathode reaction. - It is recycled back into the anolyte, improving atom utilization and also realizing the conversion from ethylene to 1,4-butanediol.

[0035] In a preferred embodiment, the copper-containing material is copper foam.

[0036] In this invention, the foamed copper generally refers to a material with a large number of interconnected or non-interconnected pores distributed in a copper matrix.

[0037] In a preferred embodiment, prior to the electrolytic reduction, a pretreatment step is included, in which the foamed copper electrode is cut into a 1×2cm shape and then immersed in concentrated phosphoric acid. The immersion time in concentrated phosphoric acid can be 1-5 minutes, for example, 3 minutes.

[0038] As an optional implementation, a carbon material is used as the working electrode of the anode. The carbon material can be a carbon rod or hydrophobic carbon paper.

[0039] In a preferred embodiment, during the electrolytic reduction process, a carbon rod is used as the working electrode at the anode to achieve Br - Oxidation and addition to ethylene yield bromoethanol.

[0040] In a preferred embodiment, the ligand molecule is selected from one or more of 2-aminoimidazole, imidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazole), 2-aminobenzimidazole, 5-aminoimidazole-4-carboxamide, and L-histidine, such as 2-aminoimidazole, imidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazole), 2-aminobenzimidazole, 5-aminoimidazole-4-carboxamide, or L-histidine.

[0041] In a preferred embodiment, the ligand molecule is selected from one or more of 2-aminoimidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazole) and 2-aminobenzimidazole.

[0042] In a preferred embodiment, the ligand molecule is selected from 2-aminoimidazole and / or (S)-2-amino-3-(1H-imidazol-4-yl)propionamide.

[0043] In a preferred embodiment, the ligand molecule is selected from 2-aminoimidazole.

[0044] In a preferred embodiment, the ligand molecule is selected from one or more of pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, 2,4,5-triamino-6-hydroxypyrimidine, and 2,2-bipyrimidine, such as pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, 2,4,5-triamino-6-hydroxypyrimidine, or 2,2-bipyrimidine.

[0045] In a preferred embodiment, the ligand molecule is selected from one or more of pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, and 2,4,5-triamino-6-hydroxypyrimidine.

[0046] In a preferred embodiment, the ligand molecule is selected from one or more of 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, and 2-aminopyrimidine.

[0047] In a preferred embodiment, the ligand molecule is selected from one or more of 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, and 2-amino-4,6-dihydroxypyrimidine.

[0048] In a preferred embodiment, the ligand molecule is selected from 2,4-diamino-6-hydroxypyrimidine.

[0049] In a preferred embodiment, the ligand molecule is selected from one or more of 2-aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, 2,3-diaminopyridine and 2,2-bipyridine, for example 2-aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, 2,3-diaminopyridine or 2,2-bipyridine.

[0050] In a preferred embodiment, the ligand molecule is selected from one or more of 2-aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, and 2,3-diaminopyridine.

[0051] In a preferred embodiment, the ligand molecule is selected from 2-aminomethylpyridine and / or 2,2'-bipyridine-3,3'-diamine.

[0052] In a preferred embodiment, the ligand molecule is selected from 2-aminomethylpyridine.

[0053] In a preferred embodiment, the ligand molecule is selected from one or more of diethylenetriamine, pentaethylenehexamine, o-phenylenediamine and melamine, such as diethylenetriamine, pentaethylenehexamine, o-phenylenediamine or melamine.

[0054] In a preferred embodiment, the ligand molecule is selected from one or more of diethylenetriamine, o-phenylenediamine, and melamine.

[0055] In a preferred embodiment, the ligand molecule is selected from diethylenetriamine and / or melamine.

[0056] In a preferred embodiment, the ligand molecule is selected from diethylenetriamine.

[0057] In a preferred embodiment, the ligand molecule is selected from one or more of pyridazine, creatinine, 1,2,4-triazole-1-formamidine hydrochloride, 1,3,5-triazine, adenine, and guanine, such as pyridazine, creatinine, 1,2,4-triazole-1-formamidine hydrochloride, 1,3,5-triazine, adenine, or guanine.

[0058] In a preferred embodiment, the ligand molecule is selected from one or more of 1,3,5-triazine, adenine, and guanine.

[0059] In a preferred embodiment, the ligand molecule is selected from adenine and / or guanine.

[0060] In a preferred embodiment, the ligand molecule is selected from one or more of the ligands shown in iv below:

[0061] i. One or more of 2-aminoimidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazole) and 2-aminobenzimidazole;

[0062] One or more of the following: pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, and 2,4,5-triamino-6-hydroxypyrimidine;

[0063] One or more of 2-aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, and 2,3-diaminopyridine;

[0064] One or more of diethylenetriamine, o-phenylenediamine, and melamine;

[0065] One or more of 1,3,5-triazine, adenine, and guanine.

[0066] In a preferred embodiment, the ligand molecule is selected from one or more of the ligands shown in iv below:

[0067] i. 2-Aminoimidazole and / or (S)-2-amino-3-(1H-imidazol-4-yl)propionamide;

[0068] One or more of 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, and 2-aminopyrimidine;

[0069] 2-Aminomethylpyridine and / or 2,2'-bipyridine-3,3'-diamine;

[0070] Diethylenetriamine and / or melamine;

[0071] One or more of 1,3,5-triazine, adenine, and guanine.

[0072] In a preferred embodiment, the ligand molecule is selected from one or more of the ligands shown in iv below:

[0073] i. 2-Aminoimidazole;

[0074] One or more of 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, and 2-amino-4,6-dihydroxypyrimidine;

[0075] 2-Aminomethylpyridine;

[0076] Diethylenetriamine;

[0077] Adenine and / or guanine.

[0078] In a preferred embodiment, the ligand molecule is selected from one or more of the following group:

[0079] 2-Aminoimidazole, 2,4-diamino-6-hydroxypyrimidine, diethylenetriamine, and guanine.

[0080] In a preferred embodiment, the ligand molecule and two Cu + The binding ability E 2Cu ≤-3.95eV.

[0081] In a preferred embodiment, the ligand molecule and two Cu +The binding ability E 2Cu ≤-3.95eV and ≥-5.41eV.

[0082] In a preferred embodiment, the ligand molecule and two Cu + The binding ability E 2Cu ≤-1.69 eV, such as -1.69 eV, -2.58 eV, -3 eV, -3.39 eV, -3.56 eV, -3.63 eV, -3.87 eV, -3.99 eV, -4.04eV, -4.09 eV, -4.09 eV, -4.1 eV, -4.16 eV, -4.18 eV, -4.2 eV, -4.24 eV, -4.4 eV, -4.56eV, -4.72 eV, -4.74 eV, -4.8 eV, -5.2 eV, -5.61 eV, -5.68 eV, -5.77 eV, -5.98 eV, -6.05 eV or -6.62 eV.

[0083] In a preferred embodiment, the number of NH2 molecules Nnh2 in the ligand molecule is ≥0, for example 0, 1, 2 or 3, or the number of NH2 molecules Nnh2 in the ligand molecule is ≥0.5.

[0084] In a preferred embodiment, when the system in the ligand molecule loses an electron due to attack by an electrophilic reagent, the change in electron density at various positions, Fukin ≥ 0.07 e, for example, 0.07 e, 0.073 e, 0.08 e, 0.102 e, 0.104 e, 0.105 e, 0.113 e, 0.119 e, 0.12 e, 0.123 e, 0.135 e, 0.136 e, 0.138 e, 0.139 e, 0.139 e, 0.141 e, 0.144 e, 0.147 e, 0.151 e, 0.155 e, 0.161 e, 0.176 e, 0.178 e, 0.201 e, 0.203 e, 0.229 e, 0.229 e, or 0.343 e.

[0085] In a preferred embodiment, the change in electron density at each position, Fukip, is ≥ 0.14 e when the system in the ligand molecule gains an electron due to nucleophilic attack.

[0086] In a preferred embodiment, the highest energy molecular orbital (HOMO) of the ligand molecule is ≤ -3.773 V, for example -3.773 eV, -4.069 eV, -4.228 eV, -4.287 eV, -4.293 eV, -4.5 eV, -4.513 eV, -4.516 eV, -4.53 eV, -4.561 eV, -4.827 eV, -4.897 eV, -4.925 eV, -4.98 eV, -5.05 eV, -5.105 eV, -5.147 eV, -5.162 eV, -5.273 eV, -5.278 eV, -5.295 eV, -5.331 eV, -5.376 eV, -5.418 eV, -5.574 eV. eV, -5.765 eV, -5.768 eV or -5.925 eV.

[0087] In a preferred embodiment, the number of COOH molecules, Ncooh, in the ligand molecule is less than 0.50.

[0088] In a preferred embodiment, the ligand molecule satisfies the following condition: E 2Cu ≤-3.95 eV, Nnh2≥0.50, Fukin≥0.08 e, HOMO≥-5.55 eV.

[0089] In a preferred embodiment, the ligand molecule satisfies the following condition: E 2Cu ≤-3.95eV, Fukip≥0.13e, Fukin≥0.14e, Ncooh<0.50, E 2Cu ≥-5.41eV.

[0090] In a preferred embodiment, the electrochemical method for preparing 1,4-butanediol includes the following steps:

[0091] Using copper foam as the working electrode of the cathode, the ligand molecules are added to the electrolyte to reduce bromoethanol to 1,4-butanediol.

[0092] In a preferred embodiment, the electrochemical method for preparing 1,4-butanediol includes the following steps:

[0093] Using hydrophobic carbon paper as the working electrode with an anode, ethylene is introduced and synthesized into bromoethanol in KBr.

[0094] The carbon paper is preferably hydrophobic carbon paper.

[0095] The concentration of KBr in the electrolyte is preferably 0.1-0.5 M, for example 0.3 M.

[0096] In the process of synthesizing ethylene into bromoethanol, the current density can be 50 mA cm⁻¹. -2 .

[0097] In the process of synthesizing ethylene into bromoethanol, the Faraday efficiency can be greater than 83%.

[0098] In a preferred embodiment, the electrochemical method for preparing 1,4-butanediol includes the following steps:

[0099] In the electrolyte of bromoethanol electrocatalytic reduction, copper foam is used as the working electrode and potassium trifluoroacetate is used as the supporting electrolyte. The ligand molecules are added to change the surface reaction environment, and electrolysis is performed to obtain 1,4-butanediol.

[0100] The present invention also provides the ligand molecule as Cu + The application of stabilizers;

[0101] The ligand molecule is selected from one or more of the ligands shown in iv below:

[0102] i. 2-Aminoimidazole, imidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazole), 2-aminobenzimidazole, 5-aminoimidazole-4-carboxamide and L-histidine;

[0103] Pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, 2,4,5-triamino-6-hydroxypyrimidine and 2,2-bipyrimidine;

[0104] 2-Aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, 2,3-diaminopyridine, 2,2-bipyridine;

[0105] Diethylenetriamine, pentaethylenehexamine, o-phenylenediamine, and melamine;

[0106] Pyridazine, creatinine, 1,2,4-triazole-1-methylamidine hydrochloride, 1,3,5-triazine, adenine, and guanine.

[0107] In this invention, the term BDO refers to 1,4-butane-1,4-diol.

[0108] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0109] The reagents and raw materials used in this invention are all commercially available.

[0110] The positive and progressive effects of this invention are as follows:

[0111] This invention utilizes copper (e.g., copper foam) as the working electrode (optionally, potassium trifluoroacetate solution is also used as the supporting electrolyte) in the electrolyte for the electrocatalytic reduction of bromoethanol. Different ligand configurations are added to alter the reaction interface environment. Simultaneously, bromide ion oxidation and ethylene addition to the counter electrode can be achieved to produce bromoethanol, enabling the entire reaction process to achieve the conversion from ethylene to BDO. Compared with existing technologies, this invention offers the following advantages:

[0112] (1) Using different types of ligands, high-yield conversion of bromoethanol to BDO in aqueous phase was achieved. For example, under the action of 2-aminoimidazole, 0.2 M bromoethanol achieved a conversion rate of over 90% and a BDO yield of 50% under electrolysis conditions of 1 h.

[0113] (2) Achieve high-yield conversion of ethylene to BDO. For example: using hydrophobic carbon paper at 50 mA cm⁻¹ -2 At the specified current density, bromoethanol can be synthesized from ethylene with a Faraday efficiency greater than 83%, thereby enabling the conversion of ethylene to 1,4-butanediol throughout the entire process and improving atom utilization.

[0114] (3) The process is simple and does not require complex treatment of the catalyst.

[0115] (4) The reaction has high stability. Attached Figure Description

[0116] Figure 1 The results are the BDO yield test results of potential screening in Examples 1-1 and 6-1 to 6-4.

[0117] Figure 2 The results are the ethylene yield test results obtained by potential screening in Examples 1-1 and 6-1 to 6-4.

[0118] Figure 3 The results are the BDO yield test results screened for different substrate bromoethanol concentrations in Examples 1-1 and 7-1 to 7-4.

[0119] Figure 4 The results are the BDO yield test results screened for different 2-aminoimidazole concentrations in Examples 1-1 and 8-1 to 8-4.

[0120] Figure 5 The results of BDO conversion using 2-aminoimidazole as a ligand in Examples 1-1 and 9-1 to 9-7 are shown.

[0121] Figure 6The results of BDO conversion using imidazole as a ligand in Examples 10-1 to 10-8 are shown.

[0122] Figure 7 This is the case in Example 11 where machine learning is used to classify and filter all ligands.

[0123] Figure 8 This refers to the case in Example 11 where machine learning was used to classify and screen ligands with a BDO yield greater than 30%.

[0124] Figure 9 The number of amino groups in the ligand and the binding energy of two Cu+ ions (E) 2Cu f + Binding energy with 2 Cu+ ions (E) 2Cu The Fukui function heatmap shows that the color represents the BDO yield; part a represents the number of amino groups in the ligand and the binding energy of two Cu+ ions (E). 2Cu The Fukui function heatmap, part b is the f in the ligand. + Binding energy with 2 Cu+ ions (E) 2Cu Fukui function heatmap.

[0125] Figure 10 The results are from Example 12, showing the BDO yield under optimal conditions and the cyclic synthesis of bromoethanol by passing the gaseous product through the counter electrode.

[0126] Figure 11 The Faraday efficiency for the conversion of ethylene to 2-bromoethanol in Example 13; wherein, Figure 11 Part a in the diagram is a schematic diagram of the reaction process of ethylene converting to 2-bromoethanol. Figure 11 Part b in the figure is a comparison of the Faraday efficiency of different carbon papers under different current densities.

[0127] Figure 12 The results show the stability test results of the electrode in Application Example 1. Detailed Implementation

[0128] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but this does not limit the invention to the scope of the embodiments described. It should be understood that the specific embodiments described herein are merely illustrative or explanatory and are not intended to limit the invention. Experimental methods in the following embodiments that do not specify specific conditions are performed according to conventional methods and conditions, or as selected according to the product instructions.

[0129] In the following embodiments and comparative examples:

[0130] Anion exchange membrane: type FAB-PK-130, purchased from Wuhan Gaoshirui Technology Co., Ltd.

[0131] Copper foam: purchased from Wuzhou Sanhe New Material Technology Co., Ltd., with a thickness of 1.6mm.

[0132] Ordinary carbon paper: purchased from Zhejiang Kaifeng New Material Co., Ltd., with a specification of 100*100mm.

[0133] Hydrophobic carbon paper: Purchased from Wuhan Gaoshi Ruilian Technology Co., Ltd., carbon paper (hydrophobic) 22BB, size 100*100mm.

[0134] Gas phase analysis: The reaction is carried out in a closed environment. After electrolysis, 10 μL of gas phase is injected into the gas phase analyzer (GC-2014C, Shimadzu). The concentration of gas phase product can be obtained by comparing the peak area integral in the gas chromatograph with the standard curve of the ethylene standard sample.

[0135] 1H NMR spectroscopy analysis: The products were analyzed using a nuclear magnetic resonance (NMR, Bruker 400 MHz Avance III HD) spectrometer. For the NMR measurements, 100 μL of electrolyte was added to 400 μL of D₂O, and 100 μL of 0.1 M fumaric acid was used as a standard sample.

[0136] The reaction yield was calculated using formula (1): (1).

[0137] The conversion rate of the reaction is calculated using formula (2): (2).

[0138] The selectivity of the reaction is calculated using formula (3):

[0139] (3).

[0140] The molar concentration of a ligand (such as 2-aminoimidazole) refers to its molar concentration in the electrolyte.

[0141] The molar concentration of the substrate bromoethanol refers to its molar concentration in the electrolyte.

[0142] Example 1-1

[0143] Step 1: Prepare 0.5 M potassium trifluoroacetate (solvent is water) as electrolyte, add 50 mM 2-aminoimidazole to obtain solution 1.

[0144] Step 2: Pour the solution 1 obtained in Step 1 into a beaker, adjust the pH to 9.5 with 0.1 M dilute hydrochloric acid, and then add 0.2 M bromoethanol substrate to obtain solution 2.

[0145] Step 3: Add the obtained solution 2 to the H-type electrolytic cell, using an anion exchange membrane and copper foam as the working electrode (cathode). Before electrolysis, cut the copper foam electrode to 1×2 cm. 2 The product was pretreated by soaking in concentrated phosphoric acid for 3 min after shaping; a carbon rod was used as the counter electrode, Ag / AgCl was used as the reference, the voltage was -0.50 V vs RHE, and electrolysis was performed for 1 h (electrolysis temperature was room temperature 25℃). The product was quantitatively analyzed by 1H NMR spectroscopy.

[0146] Table 1 shows the BDO yield test results for different imidazole ligands. The only difference between the examples in Table 1 and Examples 1-1 is the type of ligand.

[0147] Table 1

[0148]

[0149] Example 2-1

[0150] Step 1: Prepare 0.5 M potassium trifluoroacetate (solvent is water) as electrolyte, add 50 mM pyrimidine to obtain solution 1.

[0151] Step 2: Pour the solution 1 obtained in Step 1 into a beaker, adjust the pH to 9.5 with 0.1 M dilute hydrochloric acid, and then add 0.2 M bromoethanol substrate to obtain solution 2.

[0152] Step 3: Add the obtained solution 2 to an H-type electrolytic cell, use an anion exchange membrane, copper foam as the working electrode, carbon rod as the counter electrode, use Ag / AgCl as the reference, voltage -0.50 V vs RHE, electrolyze for 1 h, and use nuclear magnetic resonance hydrogen spectroscopy for quantitative analysis of the product.

[0153] Table 2 shows the BDO yield test results for different pyrimidine ligands. The only difference between the examples in Table 2 and Example 2-1 is the type of ligand.

[0154] Table 2

[0155]

[0156] Example 3-1

[0157] Step 1: Prepare 0.5 M potassium trifluoroacetate (solvent is water) as electrolyte, add 50 mM 2-aminomethylpyridine to obtain solution 1.

[0158] Step 2: Pour the solution 1 obtained in Step 1 into a beaker, adjust the pH to 9.5 with 0.1 M dilute hydrochloric acid, and then add 0.2 M bromoethanol substrate to obtain solution 2.

[0159] Step 3: Add the obtained solution 2 to an H-type electrolytic cell, use an anion exchange membrane, copper foam as the working electrode, carbon rod as the counter electrode, use Ag / AgCl as the reference, voltage -0.50 V vs RHE, electrolyze for 1 h, and use nuclear magnetic resonance hydrogen spectroscopy for quantitative analysis of the product.

[0160] Table 3 shows the BDO yield test results for different pyridine / pyrrole ligands. The only difference between the examples in Table 3 and Example 3-1 is the type of ligand.

[0161] Table 3

[0162]

[0163] Example 4-1

[0164] Except for step 1, in which the ligand is changed from 2-aminoimidazole to ethylenediamine, all other steps are the same as in Example 1-1.

[0165] Table 4 shows the BDO yield test results for different diamine / polyamine ligands. The only difference between the examples in Table 4 and Example 4-1 is the type of ligand.

[0166] Table 4

[0167]

[0168] Example 5-1

[0169] Except for step 1, in which the ligand was changed from 2-aminoimidazole to guanine, all other steps were the same as in Example 1-1.

[0170] Table 5 shows the BDO yield test results for different types of ligands, such as azines, creatinine, amidines, and purines. The only difference between the examples in Table 5 and Example 5-1 is the type of ligand.

[0171] Table 5

[0172]

[0173] Electrolysis was performed under the following conditions: electrolysis potential of -0.50 V vs RHE, 0.2 M bromoethanol, ligand concentration of 50 mM, and pH = 9.5. Different types of ligand molecules from Examples 1-1 to 5-8 were electrolyzed, as shown in Tables 1-5. For the same type of ligand, those containing multiple N-coordination sites, especially NH2 derivatives, showed a more effective increase in BDO yield. Among them, the 2-aminoimidazole molecule exhibited the highest BDO yield (≈55%) and a selectivity (≈44%).

[0174] Example 6-1

[0175] Except for step 3, where the voltage is changed from -0.50 V vs RHE to -0.60 V vs RHE, all other steps are the same as in Example 1-1.

[0176] Table 6 Figure 1 , Figure 2 The table shows the test results of BDO yield and ethylene yield at different potentials. The only difference between the examples in Table 6 and Example 6-1 is the potential.

[0177] Table 6

[0178]

[0179] 2-Aminoimidazole was added as a ligand molecule, and electrolysis was performed for 1 h under different potential conditions (-0.60~-0.40 V vs RHE). The resulting products were analyzed by 1H NMR spectroscopy. The highest BDO yield was achieved at -0.50 V vs RHE, approximately 55%, with a gaseous ethylene yield of approximately 12% (e.g., ...). Figure 1 and Figure 2 (As shown).

[0180] Example 7-1

[0181] Except for step 3, where bromoethanol is changed to 0.05M, all other steps are the same as in Example 1-1.

[0182] Table 7 Figure 3 The test results for different bromoethanol concentrations are shown in Table 7. The only difference between the examples and Example 7-1 is the bromoethanol concentration.

[0183] Table 7

[0184]

[0185] Example 8-1

[0186] Except for the concentration of 2-aminoimidazole in step 1 being changed to 10 mM, all other steps are the same as in Example 1-1.

[0187] Table 8 Figure 4 The test results for different 2-aminoimidazole concentrations are shown in Table 8. The only difference between the examples and Example 8-1 is the concentration of 2-aminoimidazole.

[0188] Table 8

[0189]

[0190] Example 9-1

[0191] Except for step 2 where the pH is changed to 7.0, all other steps are the same as in Example 1-1, and the ligand is 50 mM 2-aminoimidazole.

[0192] Table 9 Figure 5 For different pH test results, the only difference between the examples in Table 9 and Example 9-1 is the pH.

[0193] Table 9

[0194]

[0195] Under the optimal electrolysis potential conditions (-0.50 V vsRHE) determined in Examples 1-1, 6-1 to 6-4, the substrate concentration (e.g.) was investigated. Figure 3 (as shown in Table 7), ligand concentration (e.g.) Figure 4 (as shown in Table 8) and pH (as shown in Table 8) Figure 5 The effect of the reaction yield (as shown in Table 9) was determined to be that the optimal electrolysis conditions were 0.2 M bromoethanol, 50 mM 2-aminoimidazole, and pH=9.5, at which the BDO yield could reach 55% and the selectivity was ≈44%.

[0196] Example 10-1

[0197] Except for replacing 2-aminoimidazole with imidazole in step 1 and changing pH to 7.0 in step 2, all other steps are the same as in Example 1-1.

[0198] Table 10 Figure 6 For different pH test results, the only difference between the examples in Table 10 and Example 10-1 is the pH.

[0199] Table 10

[0200]

[0201] In exploring the effect of N coordination on the reaction process, 2-aminoimidazole and imidazole were compared by changing the pH (e.g., Figure 5 Table 9 Figure 6 (As shown in Table 10). Under near-neutral conditions, the amino group in 2-aminoimidazole is masked, and the yields of BDO from 2-aminoimidazole and imidazole are nearly identical, demonstrating that the amino group plays an important role in the electrocatalytic production of BDO.

[0202] Example 11

[0203] Under optimal electrolysis conditions, different types of ligand molecules were electrolyzed, as shown in Tables 1-5. For the same type of ligand, those containing multiple N coordination sites, especially NH2 derivatives, showed a more effective increase in BDO yield. Ultimately, the 2-aminoimidazole molecule exhibited the highest BDO yield (≈55%) and a selectivity of ≈44%. Machine learning was used to perform statistical analysis on the ligands in Examples 1-5 (e.g., ...). Figure 7 , Figure 8 (As shown).

[0204] The machine learning process is as follows:

[0205] The machine learning for subgroup classification was performed using the RealKD software package. Specifically, 14-means clustering was used to divide each feature into 14 subsets. The boundaries between the resulting adjacent data clusters (a1, a2, ...) were used to construct inequalities such as (feature1 < a1), (feature2 ≥ a2), etc., called propositions. Then, a Monte Carlo algorithm adapted for this purpose was used to search the subgroups as combinations of propositions and logical "AND" operators, with an initial seed size of 100,000. All sampled subgroups were sorted according to a quality function. The support scores for each proposition i in the SGD subgroup S selector, ..., (i-1) & (i) & (i+1)..., are evaluated as follows:

[0206] (4)

[0207] Where s(S) -i ) is the size (support) of the subgroup, obtained by removing proposition i from the original subgroup S, and s(S) is the size of the original subgroup.

[0208] The explanation of the machine learning parameters is shown in Table 11.

[0209] Table 11

[0210]

[0211] Table 12

[0212]

[0213] Table 12 Figure 7 The image shows the case in Example 11 where machine learning was used to classify and filter all ligands. Figure 8 This refers to the case in Example 11 where machine learning was used to classify and screen ligands with a BDO yield greater than 30%.

[0214] according to Figure 7 , Figure 8 As shown in Table 12, the strength of the interaction with copper ions is the most important factor affecting the yield of BDO.

[0215] Figure 9 The number of amino groups in the ligand and the binding energy of two Cu+ ions (E) 2Cu f + Binding energy with 2 Cu+ ions (E) 2Cu The Fukui function heatmap shows that the color represents the BDO yield; part a represents the number of amino groups in the ligand and the binding energy of two Cu+ ions (E). 2CuThe Fukui function heatmap, part b is the f in the ligand. + Binding energy with 2 Cu+ ions (E) 2Cu Fukui function heatmap. (Through) Figure 9 It can be seen that in all ligand samples, the number of -NH2 atoms is an important parameter affecting the yield of 1,4-BDO, while in samples with a yield greater than 30%, f + The change in electron density at various positions when the system gains an electron due to nucleophilic attack is also an important factor affecting the yield. Because these two parameters are closely related to the binding energy between the ligand and the copper ion, analyzing the heatmaps of these two parameters and the binding energy of the ligand molecules in the sample reveals that the relationship between these three parameters and the yield is not a monotonically increasing or decreasing one, but rather an optimal range. The ligand molecule possesses a -NH2 and f... + At around 1.5 e, it is easier to achieve high-yield synthesis of 1,4-BDO.

[0216] Example 12

[0217] When performing gas-phase product analysis, the gaseous product after the reaction is analyzed. To verify the conversion of ethylene to bromoethanol, the gaseous product is passed into the anolyte, and the electrolyte is then subjected to 1H NMR spectroscopy to verify whether the liquid-phase product is bromoethanol.

[0218] Specifically:

[0219] At a potential of -0.50 V vs RHE, using 2-aminoimidazole as the ligand molecule, under optimal reaction conditions (0.2 M bromoethanol, 50 mM 2-aminoimidazole, and pH=9.5), the gaseous product of Example 1-1 was passed into the anode, and the bromide ions were oxidized at the anode to bromoethanol with ethylene, with the remaining conditions the same as in Example 1-1.

[0220] The results are as follows Figure 10 As shown, the yield of bromoethanol from ethylene is approximately 8%, while the yields of ethylene oxide, ethanol, and 1,4-butanediol are the same as in Example 1-1. Therefore, the electrochemical method for preparing BDO in this invention can achieve the conversion of ethylene into bromoethanol.

[0221] Example 13

[0222] Following the study of the 2-bromoethanol to 1,4-BDO conversion system, the feasibility of synthesizing 1,4-BDO from ethylene was subsequently explored. Specifically:

[0223] First, using 0.5 M CF3COOK as the electrolyte (solvent: water), and adding 0.3 M KBr (molar concentration refers to the concentration in the electrolyte), constant current electrolysis was performed with ordinary carbon paper and hydrophobic carbon paper as the working electrodes (anode) and a carbon rod as the counter electrode (cathode). Ethylene was introduced during the reaction, and 0.2 M 2-bromoethanol was synthesized through electrolysis. Afterwards, 50 mM 2-aminoimidazole was added to the electrolyte to adjust the pH to 9.5. Then, using copper foam as the cathode and a carbon rod as the counter electrode (anode), electrolysis was performed for 1 h at a voltage of -0.50 V vs RHE (electrolysis temperature: room temperature 25℃). Figure 11 ,in, Figure 11 Part a in the diagram is a schematic diagram of the reaction process of ethylene converting to 2-bromoethanol. Figure 11 Part b in the figure is a comparison chart of the Faraday efficiency of different carbon papers under different current densities. According to... Figure 11 It can be seen that, when using hydrophobic carbon paper, the Faradaic efficiency of ethylene to 2-bromoethanol is >80%, and at 50 mA cm⁻¹ -2 The maximum Faraday efficiency was 84.7% when the current density was increased, while the maximum Faraday efficiency was only 50% when ordinary carbon paper was used as the working electrode. This indicates that increasing the contact between ethylene and the working electrode can significantly improve the Faraday efficiency of the electrolytic synthesis of 2-bromoethanol.

[0224] As can be seen, the electrochemical method for preparing BDO in this invention can convert ethylene into 1,4-butanediol throughout the entire process, thereby improving atom utilization.

[0225] Application Example 1

[0226] In stability testing, under optimal electrolysis conditions (at -0.50 V vs RHE potential, using 2-aminoimidazole as the ligand molecule, 0.2 M bromoethanol, 50 mM 2-aminoimidazole, and pH=9.5, with other conditions the same as in Example 1-1), the reaction yield and conversion rate did not change significantly after 20 cycles (the endpoint of each cycle was: replacement with fresh electrolyte, without changing the working electrode), indicating that the method has excellent stability (e.g., ...). Figure 12 (As shown in Table 13).

[0227] Table 13

[0228]

[0229] The above description represents a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in this embodiment. Therefore, any equivalent or modified versions made without departing from the spirit of the present invention fall within the scope of protection of the present invention.

Claims

1. An electrochemical method for preparing 1,4-butanediol, characterized in that, It includes the following steps: In an electrolyte, bromoethanol is electrolytically reduced to prepare 1,4-butanediol; wherein: The electrolyte has a pH ≥ 7.0; The working electrode of the cathode is made of copper-containing material; The electrolyte contains ligand molecules, which are selected from one or more of the ligands shown in iv below: i. One or more of 2-aminoimidazolium, imidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazolium), 2-aminobenzimidazole, 5-aminoimidazol-4-carboxamide and L-histidine; One or more of the following: pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, 2,4,5-triamino-6-hydroxypyrimidine, and 2,2-bipyrimidine; One or more of 2-aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, 2,3-diaminopyridine, and 2,2-bipyridine; iv. One or more of diethylenetriamine, pentaethylenehexamine, o-phenylenediamine, and melamine; One or more of pyridazine, creatinine, 1,2,4-triazole-1-methylamidine hydrochloride, 1,3,5-triazine, adenine, and guanine.

2. The electrochemical method for preparing 1,4-butanediol as described in claim 1, characterized in that, The ligand molecule is selected from one or more of the ligands shown in iv below: i. One or more of 2-aminoimidazolium, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazolium) and 2-aminobenzimidazole; One or more of the following: pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, and 2,4,5-triamino-6-hydroxypyrimidine; One or more of 2-aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, and 2,3-diaminopyridine; One or more of diethylenetriamine, o-phenylenediamine, and melamine; One or more of 1,3,5-triazine, adenine, and guanine.

3. The electrochemical method for preparing 1,4-butanediol as described in claim 1, characterized in that, The ligand molecule is selected from one or more of the ligands shown in iv below: i. 2-Aminoimidazole and / or (S)-2-amino-3-(1H-imidazol-4-yl)propionamide; One or more of 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, and 2-aminopyrimidine; 2-Aminomethylpyridine and / or 2,2'-bipyridine-3,3'-diamine; Diethylenetriamine and / or melamine; One or more of 1,3,5-triazine, adenine, and guanine.

4. The electrochemical method for preparing 1,4-butanediol as described in claim 1, characterized in that, The ligand molecule is selected from one or more of the ligands shown in iv below: i. 2-Aminoimidazole; One or more of 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, and 2-amino-4,6-dihydroxypyrimidine; 2-Aminomethylpyridine; Diethylenetriamine; Adenine and / or guanine; Preferably, the ligand molecule is selected from one or more of the following group: 2-Aminoimidazole, 2,4-diamino-6-hydroxypyrimidine, diethylenetriamine, and guanine.

5. The electrochemical method for preparing 1,4-butanediol according to any one of claims 1-4, characterized in that, The electrochemical method for preparing 1,4-butanediol satisfies one or more of the following conditions: (1) The electrolyte in the electrolyte solution is selected from potassium trifluoroacetate; (2) The concentration of the electrolyte in the electrolyte is 0.2-0.8M; (3) The electrolysis time is 0.5-5 hours; (4) The electrolysis temperature is 20-30℃; (5) The voltage of the electrolysis is (-0.65~-0.35) V vs RHE; (6) The pH of the electrolyte is 7.0-10.5; (7) The concentration of the ligand molecule in the electrolyte is 1-100 mM; (8) The concentration of the bromoethanol in the electrolyte is 0.05-0.4 M; and (9) The bromoethanol is prepared by oxidizing bromide ions and adding ethylene at the anode.

6. The electrochemical method for preparing 1,4-butanediol as described in claim 5, characterized in that, The electrochemical method for preparing 1,4-butanediol satisfies one or more of the following conditions: (1) The concentration of the electrolyte in the electrolyte solution is 0.5 M; (2) The electrolysis time is 1 hour; (3) The electrolysis temperature is 25℃; (4) The electrolysis voltage is (-0.60~-0.40) V vs RHE, for example -0.60 V vs RHE, -0.55 V vs RHE, -0.50 V vs RHE, -0.45 V vs RHE or -0.40 V vs RHE; (5) The pH of the electrolyte is: pH=7.0, pH=7.5, pH=8.0, pH=8.5, pH=9.0, pH=9.5, pH=10.0 or pH=10.5; (6) The concentration of the bromoethanol in the electrolyte is 0.05 M, 0.1 M, 0.2 M, 0.3 M or 0.4 M; (7) The concentration of the ligand molecule in the electrolyte is 10 mM, 25 mM, 50 mM, 75 mM or 100 mM; (8) The bromide ion is the bromide ion generated in the cathode reaction; and (9) The ethylene is ethylene generated by the cathode reaction.

7. The electrochemical method for preparing 1,4-butanediol according to any one of claims 1-4, characterized in that, The copper-containing material is copper foam; and / or, a carbon material is used as the working electrode of the anode. And / or, the ligand is 2-aminoimidazole, the electrolysis voltage is -0.50 V vs RHE, the concentration of bromoethanol is 0.2 M, the concentration of the ligand is 50 mM, and the pH of the electrolyte is 9.

5.

8. The electrochemical method for preparing 1,4-butanediol as described in claim 1, characterized in that, The ligand molecule satisfies one or more of the following conditions: (1) The binding capacity E of the ligand molecule to Cu + 2Cu ≤-1.69 eV, for example -1.69 eV, -2.58 eV, -3 eV, -3.39 eV, -3.56 eV, -3.63 eV, -3.87 eV, -3.99 eV, -4.04 eV, -4.09 eV, -4.09 eV, -4.1eV, -4.16 eV, -4.18 eV, -4.2 eV, -4.24 eV, -4.4 eV, -4.56 eV, -4.72 eV, -4.74 eV, -4.8eV, -5.2 eV, -5.61 eV, -5.68 eV, -5.77 eV, -5.98 eV, -6.05 eV or -6.62 eV;​ (2) The number of NH2 molecules Nnh2 in the ligand molecule is ≥0, for example, 0, 1, 2 or 3; or, the number of NH2 molecules Nnh2 in the ligand molecule is ≥0.5; (3) When the system in the ligand molecule loses an electron due to the attack of an electrophilic reagent, the change in electron density at each position, Fukin ≥ 0.07 e, for example, 0.07 e, 0.073 e, 0.08 e, 0.102 e, 0.104 e, 0.105 e, 0.113 e, 0.119 e, 0.12 e, 0.123 e, 0.135 e, 0.136 e, 0.138 e, 0.139 e, 0.139 e, 0.141 e, 0.144 e, 0.147 e, 0.151 e, 0.155 e, 0.161 e, 0.176 e, 0.178 e, 0.201 e, 0.203 e, 0.229 e, 0.229 e, or 0.343 e; (4) The change in electron density at each position in the ligand molecule when it gains an electron due to nucleophilic attack, Fukip ≥ 0.14 e; and (5) The highest energy molecular orbital (HOMO) already occupied in the ligand molecule is ≤ -3.773 V, for example -3.773 eV, -4.069 eV, -4.228 eV, -4.287 eV, -4.293 eV, -4.5 eV, -4.513 eV, -4.516 eV, -4.53 eV, -4.561 eV, -4.827 eV, -4.897 eV, -4.925 eV, -4.98 eV, -5.05 eV, -5.105 eV, -5.147 eV, -5.162 eV, -5.273 eV, -5.278 eV, -5.295 eV, -5.331 eV, -5.376 eV, -5.418 eV, -5.574 eV. eV, -5.765 eV, -5.768 eV or -5.925 eV.

9. The electrochemical method for preparing 1,4-butanediol according to any one of claims 1-4, characterized in that, The electrochemical method for preparing 1,4-butanediol includes the following steps: using copper foam as the cathode working electrode, adding the ligand molecule to the electrolyte, and reducing bromoethanol to 1,4-butanediol; or, The electrochemical method for preparing 1,4-butanediol includes the following steps: using carbon paper as the anode working electrode, ethylene is introduced, and ethylene is synthesized into bromoethanol in KBr.

10. A ligand molecule as Cu + The application of stabilizers; The ligand molecule is selected from one or more of the ligands shown in iv below: i. 2-Aminoimidazole, imidazole, (S)-2-amino-3-(1H-imidazol-4-yl)propionamide, 2,2'-bis(4,5-dimethylimidazole), 2-aminobenzimidazole, 5-aminoimidazole-4-carboxamide and L-histidine; Pyrimidine, 2,4-diamino-6-hydroxypyrimidine, 2,6-diaminopyrimidine-4-ol, 2-amino-4,6-dihydroxypyrimidine, 2-aminopyrimidine, 2,4,5-triamino-6-hydroxypyrimidine and 2,2-bipyrimidine; 2-Aminomethylpyridine, 2,2'-bipyridine-3,3'-diamine, 2,3-diaminopyridine, 2,2-bipyridine; Diethylenetriamine, pentaethylenehexamine, o-phenylenediamine, and melamine; Pyridazine, creatinine, 1,2,4-triazole-1-formamidin hydrochloride, 1,3,5-triazine, adenine, and guanine.

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