CN112830449B - Reversible liquid organic hydrogen storage method based on manganese catalytic hydrogenation and dehydrogenation reaction - Google Patents
Reversible liquid organic hydrogen storage method based on manganese catalytic hydrogenation and dehydrogenation reaction Download PDFInfo
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Abstract
The invention discloses a reversible liquid organic hydrogen storage method based on manganese catalytic hydrogenation and dehydrogenation reactions. The method for storing and releasing hydrogen provided by the invention comprises the following steps: 1) under the catalysis of a manganese complex, carrying out dehydrogenation reaction on N, N ' -dimethyl ethylenediamine and methanol to obtain N, N ' -diformyl-N, N ' -dimethyl ethylenediamine and hydrogen, and realizing the release of the hydrogen; 2) under the catalysis of a manganese complex, N, N ' -diformyl-N, N ' -dimethylethylenediamine and hydrogen are subjected to hydrogenation reaction to obtain N, N ' -dimethylethylenediamine, so that the hydrogen is stored. The use of manganese complexes to catalyze the dehydrogenation and hydrogenation of liquid organic hydrogen storage materials to generate and store hydrogen is also within the scope of the present invention, i.e., the dehydrogenation and hydrogenation reactions are reversible. The hydrogen storage system provided by the invention has the hydrogen storage density of 5.3%, and can obtain the diamide product with the selectivity of 97% for the dehydrogenation system, and the purity of the generated hydrogen can reach more than 99.9%.
Description
Technical Field
The invention relates to a reversible liquid organic hydrogen storage method based on manganese catalytic hydrogenation and dehydrogenation reactions, and belongs to the technical field of catalytic processes.
Background
Hydrogen has long been considered as one of the most promising sustainable energy carriers due to its high energy density, it can be efficiently converted into electrical energy by fuel cells, and it produces only water during combustion. In recent years, significant progress has been made in the research on hydrogen production from renewable energy sources and high-efficiency hydrogen fuel cells. However, hydrogen has not been widely used as an energy source due to its great challenges in storage. In view of the economic and safety problems of compressed liquid hydrogen and low-temperature liquid hydrogen, the technology of storing hydrogen in chemical bonds through reversible catalytic hydrogenation/dehydrogenation has a great application prospect. In the early days, formic acid, formaldehyde and methanol have been extensively studied as hydrogen carriers, but these liquid carriers are releasing H 2 While CO is generated 2 Is consumed, resulting in H 2 Cannot be reloaded again; in addition, the use of stoichiometric alkali and the low hydrogen storage density of formic acid (4.3 wt%) further limit the development of this approach. Therefore, in order to develop a more efficient hydrogen storage system, researchers developed a strategy for Liquid Organic Hydrogen Carriers (LOHCs) that passed H 2 -rich liquid organic compounds and H 2 Interconversion between the hydrogenation and dehydrogenation of lean liquid organic compounds enables storage and release of hydrogen. LOHCs early studies focused on cycloalkanesAnd the dehydrogenation and hydrogenation between aromatic hydrocarbons, but often require harsh reaction conditions (usually>At 250 deg.c). In order to reduce the endothermic heat, LOHCs systems based on nitrogen-containing organic hydrides (e.g., nitrogen heterocycles) have been developed, which have a high hydrogen storage density (5.3 to 7.3 wt%). In recent years, Milstein and Prakash task group reported a novel LOHCs system, which uses inexpensive amines and alcohols as hydrogen carriers, and realizes storage and release of hydrogen by dehydrogenation of the hydrogen carriers to form amide bonds and hydrogenation through ruthenium catalysis, but the selectivity of amide bond formation during dehydrogenation of the system is often poor.
In addition to the development of a renewable and inexpensive liquid molecular hydrogen carrier, it is also an important goal to develop economically efficient, sustainable and highly efficient catalysts for LOHCs systems. All reported hydrogen storage systems to date use noble metal catalysts. Therefore, it is of great importance to develop a high-efficiency catalytic system based on abundant and low-toxicity non-noble metals.
Disclosure of Invention
The invention aims to provide a novel manganese catalytic hydrogenation and dehydrogenation system for realizing a reversible conversion method of N, N ' -dimethylethylenediamine-methanol and N, N ' -diformyl-N, N ' -dimethylethylenediamine as liquid organic hydrogen storage materials; the hydrogen storage system has 5.3 percent of hydrogen storage density and can realize a reversible dehydrogenation adding process under the catalysis of a manganese catalyst; the selectivity of the dehydrogenation system can be up to 97% to obtain the diamide product, and the purity of the generated hydrogen can reach more than 99.9%.
The invention firstly provides a method for storing and releasing hydrogen, which comprises the following steps:
1) under the catalysis of a manganese complex, carrying out dehydrogenation reaction on N, N ' -dimethyl ethylenediamine and methanol to obtain N, N ' -diformyl-N, N ' -dimethyl ethylenediamine and hydrogen, and realizing the release of the hydrogen;
the dehydrogenation reaction simultaneously obtains N-formyl-N, N' -dimethylethylenediamine and 1, 3-dimethyl-1, 3-imidazolidine;
2) under the catalysis of the manganese complex, carrying out hydrogenation reaction on N, N ' -diformyl-N, N ' -dimethylethylenediamine and hydrogen to obtain N, N ' -dimethylethylenediamine, and realizing the storage of the hydrogen;
the hydrogenation reaction simultaneously produces N-formyl-N, N' -dimethylethylenediamine and 1, 3-dimethyl-1, 3-imidazolidine.
The reaction equations of the dehydrogenation reaction and the hydrogenation reaction related to the present invention are respectively shown in formula (1) and formula (2):
wherein [ Mn ] represents the manganese complex.
The dehydrogenation reaction conditions were as follows:
in the presence of a strong base;
the strong base can be potassium tert-butoxide, potassium methoxide or potassium hydroxide;
the dosage of the strong base is 2.7-8% of the molar weight of the N, N' -dimethylethylenediamine, and specifically can be 2.7-4%, 2.7%, 4% or 8%;
the solvent for dehydrogenation reaction can be high boiling point solvent such as dioxane, toluene, xylene or mesitylene;
the dosage of the solvent is as follows: 0.25 to 1.5mmol of N, N' -dimethylethylenediamine: 0-1 mL of solvent, and when the amount of the substrate is increased, moderate yield and selectivity can be obtained even when the solvent is not added;
the using amount of the manganese complex can be 1-2% of the molar amount of the N, N' -dimethylethylenediamine, and specifically can be 1.34-2%, 1.34% or 2%;
the dehydrogenation reaction is carried out at the temperature of 150-165 ℃ for 8-16 hours.
The conditions of the hydrogenation reaction were as follows:
in the presence of a strong base;
the strong base can be potassium tert-butoxide;
the dosage of the strong base is 2.5-20% of the molar weight of the N, N '-diformyl-N, N' -dimethylethylenediamine, such as 2.5% or 20%;
the solvent for the hydrogenation reaction is a high boiling point solvent such as dioxane, toluene, xylene or mesitylene;
the dosage of the solvent is as follows: 0.25 to 0.5mmol of N, N '-diformyl-N, N' -dimethylethylenediamine: 0.2-2 mL of a solvent;
the manganese complex can be used in an amount of 2 to 3%, such as 2%, of the molar amount of the N, N '-diformyl-N, N' -dimethylethylenediamine;
the temperature of the hydrogenation reaction is 90-180 ℃, and the time is 6-16 hours.
Further, the present invention also provides an organic liquid hydrogen storage system for storing and releasing hydrogen gas, comprising:
1) n, N' -dimethylethylenediamine and methanol;
2) n, N '-diformyl-N, N' -dimethylethylenediamine;
3) a manganese complex;
under the catalysis of the manganese complex, the N, N' -dimethylethylenediamine and the methanol are subjected to a dehydrogenation reaction to release hydrogen; the N, N '-diformyl-N, N' -dimethylethylenediamine is subjected to a hydrogenation reaction to store hydrogen gas under the catalysis of the manganese complex.
For the hydrogen storage system, 1 molecule of N, N ' -dimethylethylenediamine and 2 molecules of methanol can theoretically generate 1 molecule of N, N ' -diformyl-N, N ' -dimethylethylenediamine and release 4 molecules of hydrogen gas under the catalysis of the catalyst, and in conclusion, the hydrogen storage density for the hydrogen storage system is: {4 XMw (Hydrogen) /[1×Mw (N, N' -dimethylethylenediamine) +2×Mw (methanol) ]} × 100%, i.e., [4 × 2.02/(1 × 88.15+2 × 32.04)]×100％＝5.3％。
The application of the manganese complex in catalyzing dehydrogenation reaction and hydrogenation reaction of the liquid organic hydrogen storage material to generate hydrogen and store the hydrogen also belongs to the protection scope of the invention, namely the dehydrogenation reaction and the hydrogenation reaction are reversible reaction;
the liquid organic hydrogen storage material comprises the following components:
1) a mixture of N, N' -dimethylethylenediamine and methanol;
2) n, N '-diformyl-N, N' -dimethylethylenediamine.
The structure of the manganese complex related by the invention is shown as formula I-formula VII:
wherein iPr represents an isopropyl group, and Ph represents a phenyl group.
The catalytic dehydrogenation reaction is preferably a manganese complex represented by formula VI, and the catalytic hydrogenation reaction is preferably a manganese complex represented by formula VI or formula IV.
The manganese complexes of the invention can be prepared according to known methods, such as:
reacting pentacarbonyl manganese bromide with NNP ligand or PNP ligand under the protection of inert atmosphere, wherein the NNP ligand and the PNP ligand can be prepared by adopting the existing method;
the reaction is carried out in a solvent, which may be at least one of toluene, xylene, and tetrahydrofuran.
The invention achieves the following technical effects:
1. the novel manganese catalytic system provided by the invention can catalyze the reversible interconversion of diamine-methanol and diamide as hydrogen storage materials.
2. The hydrogen storage system has 5.3 percent of hydrogen storage density, and can obtain the diamide products with selectivity of 97 percent for the dehydrogenation system, and the generated hydrogen can reach the purity of 99.9 percent.
Drawings
FIG. 1 is an X-ray diffraction single crystal structure of a manganese complex represented by formula VII.
Detailed Description
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
In the following examples, Me represents a methyl group, tBu represents a tert-butyl group, nBu represents a n-butyl group, Ph represents a phenyl group, Bn represents a benzyl group, Cy represents a cyclohexyl group, iPr represents an isopropyl group, PE represents petroleum ether, EA represents ethyl acetate, TLC represents thin layer chromatography, NMR represents nuclear magnetic resonance, and HRMS represents high resolution mass spectrometry.
The ligand bis [2- (diisopropylphosphino) ethyl ] in the examples below]Amine (a) iPr PNP) available from Alfa-Aesar reagent, purity>95 percent; the remaining ligands were synthesized as described in the reference: (J.Am.chem.Soc.2017,139, 11941-11948.; Angew.chem.Int.Ed.2018,57, 13439-13443.).
Mn(CO) 5 Br purchased from Alfa-Aesar reagent, Ltd in purity>97% of the total amount of the above-mentioned components were used as they were.
All solvents used were purchased from Shanghai national pharmaceutical Agents, purified and dried by standard methods prior to use.
Firstly, preparing an imidazole-NNP ligand:
1. synthesis of 2-chloro-N, N-bis (trimethylsilyl) ethylamine
2-Chloroethylamine hydrochloride (4.6g,40mmol), triethylamine (NEt) were added to a Schlenk bottle 3 18mL,132mmol) and 50mL of dichloromethane, adding a solution of trimethylchlorosilane (TMSCl,90mmol,9.8g,11.4mL) in dichloromethane (20mL) to the obtained system, and stirring the reaction at room temperature for 12 h; after the reaction is finished, removing excessive triethylamine, trimethylchlorosilane and dichloromethane under reduced pressure, adding 60mL of normal hexane into the obtained residue, stirring for 30min at room temperature, and filtering to remove NEt 3 HCl, and after n-hexane was removed by rotary evaporation of the filtrate using a rotary evaporator, the filtrate was distilled under reduced pressure using an oil pump to obtain a fraction of the objective product (yield 6.0g, yield 68%).
1 H NMR(400MHz,CDCl 3 )δ3.37–3.21(m,2H),3.18–2.99(m,2H),0.14(s,18H). 13 C NMR(101MHz,CDCl 3 )δ47.38,44.83,1.89。
2. Synthesis of diphenylphosphinoethylamine
Under the condition of argon protection and the temperature of-78 ℃, adding a tetrahydrofuran solution (20mL) of diphenylphosphine hydrogen (1.86g,10mmol) into a Schlenk bottle, then slowly dropwise adding an n-hexane solution (2.5mol/L,4.4mL,11mmol) of n-butyllithium, after dropwise adding, slowly heating a reaction system to room temperature, and stirring for 2 hours at the room temperature; then cooling the Schlenk bottle to 0 ℃ by using an ice water bath, slowly adding 2-chloro-N, N-bis (trimethylsilyl) ethylamine (2.45g,11mmol), and carrying out reflux reaction for 12h at 80 ℃; after the reaction is finished, cooling the obtained system to room temperature, adding 5mL of water and 6mL of 2.0mmol/mL sulfuric acid, stirring for 1h, then adding 7mL of 4.0mmol/mL sodium hydroxide solution, and stirring for 0.5 h; the organic phase was separated, the aqueous phase was extracted with ether (3 × 20mL), the organic phases were combined, dried over anhydrous sodium sulfate and dried to give the crude product (crude yield 2.06g, crude yield 95%) which was used directly in the next step without further column chromatography.
3. Synthesis of imidazole NNP ligands
Under the protection of argon and at room temperature, adding a tetrahydrofuran solution (6mL) of imidazole formaldehyde (110mg,1.0mmol) into a Schlenk bottle, then dropwise adding a tetrahydrofuran solution (6mL) of diphenylphosphine ethylamine (290mg,1.0mmol), and reacting at room temperature for 1 h; then, tetrahydrofuran is pumped out by an oil pump through a Schlenk pipeline connected with a cold trap, 6mL of toluene is added, a toluene solution of diisobutylaluminum hydride (DIBAL) (1.5mol/L,1.2mL, 1.8mmol) is added under the condition of ice-water bath, the mixture reacts for 2h under the condition of room temperature, 10mL of water is added for quenching reaction, an organic phase is separated, an aqueous phase is extracted by diethyl ether (3X 20mL), the obtained organic phases are combined, dried by anhydrous sodium sulfate and dried by spinning, and column chromatography separation (the adopted eluent is a mixture of dichloromethane and methanol, the volume ratio of the dichloromethane to the methanol is 20: 1) is carried out to obtain a light yellow oily liquid which is the target product (the yield is 210mg, and the yield is 65%).
1 H NMR(400MHz,CDCl 3 )δ7.41(ddt,J＝7.4,5.4,2.7Hz,4H),7.35–7.29(m,6H),6.91(d,J＝1.3Hz,1H),6.80(d,J＝1.3Hz,1H),3.82(s,2H),3.64(s,3H),2.86–2.74(m,2H),2.31–2.23(m,2H),1.77(b,1H)。
13 C NMR(101MHz,CDCl 3 )δ146.3,138.3(d,J＝12.4Hz),132.7(d,J＝18.7Hz),128.6,128.4(d,J＝6.7Hz),127.1,121.2,46.2(d,J＝20.3Hz),45.6,32.7,28.9(d,J＝12.4Hz)。
31 P NMR(162MHz,CDCl 3 )δ-20.76(s)。
HRMS(ESI)calcd.for C19H22N3P[M+H] + :324.1624；found:324.1610。
Preparation of di, N-Me-PNP (Ph) ligand
To a 50mL Schlenk flask, diphenylphosphine (1.50g,8mmol) and degassed THF (10mL) were added under argon, the solution was cooled to-20 deg.C, nBuLi (4mL,2.5M in hexanes,10mmol) was added slowly to the solution, and after the addition was complete, the solution was slowly warmed to room temperature and refluxed for 1 hour. To another 50mL Schlenk flask, MeN (CH) was added under argon 2 CH 2 Cl) 2 HCl (0.62g,3.2mmol) and THF (10mL), the solution was cooled to-20 deg.C, to which nBuLi (1.5mL,2.5M in hexanes,3.75mmol) was slowly added, after which time it was allowed to warm to room temperature and stirring continued for 2 h. Then, a THF solution of lithium diphenylphosphine was slowly added to the above solution at-78 deg.C, and then the reaction was slowly warmed to room temperature and heated under reflux overnight. After the reaction was complete, THF was pumped off, 5mL of degassed water was added to the residue, the solution was extracted three times with degassed ether (3 × 10mL), the organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the organic phase was concentrated and separated on a column (CH2Cl2/MeOH 100/1to 50/1) to give a pale yellow liquid (0.71g, 49%).
1 H NMR(400MHz,CDCl 3 )δ7.39(td,J＝7.2,3.1Hz,8H),7.33–7.29(m,12H),2.48(m,4H),2.24(s,3H),2.36–2.12(m,4H). 13 C NMR(101MHz,CDCl 3 )δ138.44(d,J＝12.2Hz),132.70(d,J＝19.1Hz),128.58(s),128.45(s),128.38(s),53.38(d,J＝27.3Hz),41.75(s),25.75(d,J＝12.1Hz).
31 P NMR(162MHz,CDCl 3 )δ-19.79(s).
HRMS(ESI)calcd.for C 29 H 31 NP 2 [M+H] + :456.2004；found:456.1988.
Example 1 Synthesis of imidazole NNP-Mn (CO) 2 Br Complex (formula IV)
The reaction equation is as follows:
in a glove box filled with argon, imidazole NNP ligand (210mg,0.65mmol) and manganese pentacarbonyl bromide (165mg,0.60mmol) were added to a schleck bottle and reacted at reflux at 110 ℃ for 12 h; after the reaction was completed, the obtained system was cooled to room temperature, a yellow precipitate was precipitated, and after filtration, the yellow filter cake (2X 1mL) was washed with toluene, and the filter cake (3X 5mL) was washed with ether, followed by vacuum drying to obtain the objective catalyst (yield 260mg, yield 80%).
1 H NMR(400MHz,DMSO-d 6 )δ7.76(t,J＝7.6Hz,2H),7.55(m,3H),7.45–7.34(m,5H),7.07(s,1H),6.42(s,1H),4.32(d,J＝16.8Hz,1H),4.08(d,J＝16.8Hz,1H),3.56(s,3H),3.14(m,1H),2.87–2.69(m,1H),2.27(m,2H)。
13 C NMR(101MHz,DMSO-d 6 )δ149.8,132.7,132.3,132.0,131.9,131.7,131.4,131.0,130.9,129.7(d,J＝9.5Hz),129.4(d,J＝9.3Hz),128.1,125.2,54.9(d,J＝11.4Hz),49.7,34.7,22.5(d,J＝22.6Hz)。
31 P NMR(162MHz,DMSO-d 6 )δ63.97(s)。
HRMS(ESI)calcd.for C 22 H 22 BrMnN 3 O 3 P[M-Br] + :462.0774；found:462.0775。
From the above analysis results, it was found that the prepared target manganese complex had a correct structure.
Example 2 Synthesis of N-Me-PNP (Ph) -Mn (CO) 2 Br Complex (formula VII)
To a 25mL Schlenk flask, under argon atmosphere, was added [ Mn (CO) 5 Br](92mg,0.33mmol)，[N-Me-PNP-iPr](160mg,0.35mmol) and degassed toluene (10mL), the reaction was heated to 100 ℃ and stirred overnight. After the reaction was complete, the toluene was drained, 10mL of degassed n-hexane was added, the mixture was filtered under argon, and the filter cake was dried under vacuum to give a pale yellow solid (175mg, 82%).
1 H NMR(400MHz,DCM-d 2 )δ7.89–7.76(m,8H),7.49–7.35(m,12H),3.79–3.72(m,2H),3.24–3.14(m,2H),3.01–2.93(m,2H),2.81–2.71(m,2H),2.67(s,3H). 13 C NMR(101MHz,DCM-d 2 )δ132.34(t,J＝5.0Hz),131.50(t,J＝5.1Hz),129.50(s),129.03(s),128.53(t,J＝4.4Hz),127.78(t,J＝3.9Hz),59.08(t,J＝4.4Hz),49.94(s),27.77(t,J＝8.8Hz).
31 P NMR(162MHz,DCM-d 6 )δ69.06(s).
HRMS(ESI)calcd.for C 31 H 31 BrMnNO 2 P 2 [M-Br] + :566.1205；found:566.1205.
The X-ray single crystal structure is shown in fig. 1.
From the above analysis results, it was found that the prepared target manganese complex had a correct structure.
The preparation of the complexes of formula I, formula II, formula III, formula V, formula VI is described in the literature (J.Am.chem.Soc.2017,139, 11941-11948; Angew.chem.int.Ed.2018,57, 13439-13443).
Example 3 investigation of the results of dehydrogenation reactions with different manganese catalysts [a]
TABLE 1 comparison of the effectiveness of different manganese catalysts for dehydrogenation reactions
[a] The reaction conditions (0.25mmol) of N, N' -dimethylethylenediamine, (6eq,1.5mmol) of methanol, (4 mol%) of potassium tert-butoxide, (2 mol%) of the catalyst, (0.4mL) of dioxane were reacted in a 25mL pressure-tight tube for 16h at 165 ℃ with conversion and yield determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard. [b] The hydrogen yield was calculated based on the hydrogen liberated when all 1 was converted to 2a, and the hydrogen purity was checked by gas phase GC and shown in parentheses.
Under the protection of argon, a manganese catalyst (0.005mmol,2 mol%), potassium tert-butoxide (0.01mmol,4 mol%), N, N' -dimethylethylenediamine (0.25mmol), methanol (1.5mmol,6equiv.) and dioxane (0.4mL) were added successively to a 25mL sealed tube containing a magnetic stirrer and reacted at 165 ℃ for 16 h. After the reaction is finished, the reaction product is cooled by ice water, gas generated inside the sealed tube is slowly released, the total volume of the generated gas is measured, and the purity of the gas is obtained through gas phase GC detection. Adding 1,1,2, 2-tetrachloroethane as internal standard into liquid phase system, and performing GC reaction 1 H NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 1.
It was found by screening the catalyst that no conversion of the feedstock could be detected with a catalyst of the NNP type Pincer [ Mn ] (+1) (entry 1-4); in contrast, the conversion of the starting material and the formation of the desired product can be detected using a PNP type of catalyst, Pincer [ Mn ] (+1) (entry5-6), and better yields and selectivities than isopropyl can be obtained when the substituent is phenyl.
Example 4 investigation of the results of dehydrogenation reactions with different bases and solvents [a]
TABLE 2 optimization of dehydrogenation reaction conditions with different bases and solvents
[a] Reaction conditions (0.25mmol) N, N' -dimethylethylenediamine, (6eq,1.5mmol) methanol, (4 mol%) base, (2 mol%) and formula VI were reacted in a 25ml pressure-tight tube for 16h at 165 ℃ with conversion and yield determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard. [b] The hydrogen yield was calculated based on the hydrogen liberated when all 1 was converted to 2a, and the hydrogen purity was checked by gas phase GC and shown in parentheses.
The catalyst of formula VI (0.005mmol,2 mol%), base (0.01mmol,4 mol%), N, N' -dimethylethylenediamine (0.25mmol), methanol (1.5mmol,6equiv.) and solvent (0.4mL) were added successively to a 25mL lock containing a magnetic stirrer under argon and reacted at 165 ℃ for 16 h. After the reaction is finished, the reaction product is cooled by ice water, gas generated inside the sealed tube is slowly released, the total volume of the generated gas is measured, and the purity of the gas is obtained through gas phase GC detection. Adding 1,1,2, 2-tetrachloroethane as internal standard into liquid phase system, and performing GC reaction 1 H NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 2.
Through the optimization of the conditions of the base and the solvent, the optimal yield and selectivity (entry 1and 3) can be obtained when potassium tert-butoxide and potassium methoxide are used as the bases, and the yield of the target product is reduced by other bases (sodium tert-butoxide, potassium hydroxide and sodium ethoxide) (entry 2, 4 and 5); simple screening of the solvent shows that the solvent can obtain better selectivity and yield for aromatic solvents with high boiling points (toluene, xylene and mesitylene) (entry 6-8).
Example 5 investigation of the enlargement of the amount of substrate [a]
[a] Reaction conditions (1.5mmol) of N, N' -dimethylethylenediamine, (2eq,3.0mmol) of methanol, (1.33 mol%) of potassium tert-butoxide, (0.67 mol%) of formula VI were reacted in a 25ml pressure-tight tube for 6 hours and then cooled to room temperature to release the gases produced in the reaction system, and then (1eq,1.5mmol) of methanol, (1.33 mol%) of potassium tert-butoxide, (0.67 mol%) of formula VI were added again to the reaction system and the reaction was continued at 165 ℃ for 10 hours, the conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard.
Under the protection of argon, adding the catalyst (0.01mmol,0.67 mol%) of the formula VI, potassium tert-butoxide (0.02mmol,1.33 mol%), N, N' -dimethylethylenediamine (1.5mmol) and methanol (3mmol,2equiv.) in sequence into a 25mL sealed tube containing a magnetic stirrer, reacting at 165 ℃ for 6h, and releasing the generated gas of the reaction system; then VI catalyst (0.01mmol,0.67 mol%), potassium tert-butoxide (0.02mmol,1.33 mol%) and methanol (1.5mmol,1equiv.) were added again to the reaction and the reaction was continued at 165 ℃ for 10h. After the reaction is finished, 1,2, 2-tetrachloroethane is added into a liquid phase system as an internal standard, and GC and 1 h NMR (in CDCl) 3 Deuterated reagent) to quantitatively obtain the conversion rate of the raw material and the yield of the product, the target product N, N '-diformyl-N, N' -dimethylethylenediamine can be obtained in a yield of 52% in the case of the reaction equation.
This example shows that the amount of substrate is increased, and that the dehydrogenation reaction can achieve an intermediate yield and selectivity even when no solvent is added.
Example 6 study of the results of dehydrogenation reaction with other parameters [a]
TABLE 3 optimization of other parameters for dehydrogenation reaction conditions
[a] Reaction conditions (0.25mmol) N, N' -dimethylethylenediamine, (6eq,1.5mmol) methanol, (4 mol%) potassium tert-butoxide, (2 mol%) formula VI were reacted in a 25ml pressure-tight tube for 16h at 165 ℃ conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as internal standard. [b] The reaction temperature was 150 ℃. [C] After reacting for 2 hours, cooling to room temperature, releasing gas generated in the reaction system, and then continuing the reaction at 165 ℃ for 6 hours. [d] (1 mol%) of formula VI, (4 mol%) of potassium tert-butoxide, cooling to room temperature after 2 hours of reaction to release the gases generated in the reaction system, adding (1 mol%) of formula VI again, and continuing the reaction at 165 ℃ for 6 hours.
Under the protection of argon, the catalyst of formula VI (0.005mmol,2 mol%), potassium tert-butoxide, N, N' -dimethylethylenediamine, methanol and dioxane were added one after the other to a 25mL sealed tube containing a magnetic stirrer and reacted at the given temperature. After the reaction is finished, the reaction product is cooled by ice water, gas generated inside the sealed tube is slowly released, the total volume of the generated gas is measured, and the purity of the gas is obtained through gas phase GC detection. Adding 1,1,2, 2-tetrachloroethane as internal standard into liquid phase system, and performing GC reaction 1 H NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 3.
Systematically screening methanol equivalent (entry 1-3), alkali amount (entry1, 4-6) and solvent amount (entry1, 7-9) required by the reaction to obtain the optimal equivalent of 6eq of methanol, the optimal amount of 4 mol% of alkali and 0.6mL of solvent; when the temperature is continuously reduced to 150 ℃, the yield and the selectivity of the product are reduced; in order to obtain higher product selectivity and hydrogen purity, the reaction is tried to be continued for 6 hours after the gas generated by the relief system is released after the reaction is carried out for two hours, at the moment, the selectivity for the diamide product can reach 97 percent, and the hydrogen yield and the hydrogen purity are respectively 98 percent and 98.7 percent; when the catalyst required for the reaction is added to the system in two portions, the hydrogen purity obtained can then be > 99.9%.
Example 7 investigation of solvent amount on dehydrogenation reaction results [a]
TABLE 4 optimization of solvent amounts to dehydrogenation reaction conditions
[a] The reaction conditions were (0.25mmol) of N, N' -dimethylethylenediamine, (6eq,1.5mmol) of methanol, (4 mol%) of potassium tert-butoxide, (2 mol%) of formula VI were reacted in a 25ml pressure-tight tube for 2 hours, then cooled to room temperature to release the gases generated in the reaction system, and then the reaction was continued at 165 ℃ for 6 hours. the conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard.
Under the protection of argon, the catalyst of formula VI (0.005mmol,2 mol%), potassium tert-butoxide (0.01mmol,4 mol%), N, N' -dimethylethylenediamine (0.25mmol), methanol (1.5mmol,6equiv.) and dioxane were added successively to a 25mL sealed tube containing a magnetic stirrer, and the produced gas of the reaction system was released after reaction for 2h at 165 ℃. The total volume of gas produced was determined and its purity of the gas was determined by gas GC. Adding 1,1,2, 2-tetrachloroethane as internal standard into liquid phase system, and performing GC reaction 1 H NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 4.
The solvent optimization described above revealed that the dehydrogenation reaction solvent can be reduced to 0.2mL to obtain a good selectivity.
Example 8 investigation of the results of hydrogenation with different manganese catalysts [a]
TABLE 5 comparison of hydrogenation effects of different manganese catalysts
[a] Reaction conditions (0.25mmol) N, N '-diformyl-N, N' -dimethylethylenediamine, (20 mol%) potassium tert-butoxide, (2 mol%) of formula IV, (1mL) dioxane were reacted under 60bar hydrogen pressure for 16h at 150 ℃ conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as internal standard.
Under the protection of argon, a manganese catalyst (0.005mmol,2 mol%), potassium tert-butoxide (0.05mmol,20 mol%), N, N '-diformyl-N, N' -dimethylethylenediamine (0.25mmol) and dioxane (1mL) were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted at 150 ℃ under 60bar hydrogen pressure for 16 h. After the reaction is finished, cooling the mixture by ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and carrying out GC and GC 1 H NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 5.
From the results of the screening of the catalysts, it was found that the conversion of the starting material could be detected with the NNP type of catalyst, Pincer [ Mn ] (+1) (entry1-4), and the target product could be obtained in close equivalents when formula IV was used as the catalyst; the conversion of the starting material and the formation of the target product can also be detected with the PNP type of catalyst Pincer [ Mn ] (+1) (entry5-6), but the target product can only be obtained in moderate yields.
Example 9 investigation of the results of hydrogenation reactions with different bases and solvents [a]
TABLE 6 optimization of hydrogenation conditions for different bases and solvents
[a] Reaction conditions (0.25mmol) N, N '-diformyl-N, N' -dimethylethylenediamine, (20 mol%) base, (2 mol%) formula IV were reacted under 60bar hydrogen pressure for 16h at a reaction temperature of 150 ℃ and conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard.
Under the protection of argon, the catalyst of formula IV (0.005mmol,2 mol%), alkali (0.05mmol,20 mol%), N, N '-diformyl-N, N' -dimethylethylenediamine (0.25mmol) and dioxane (1mL) were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted at 150 ℃ under 60bar hydrogen pressure for 16 h. After the reaction is finished, cooling with ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and performing GC reaction and 1 h NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 6.
Through the optimization of the conditions of the base and the solvent, the best yield and selectivity (entry 1) can be obtained when the potassium tert-butoxide is used and the base is used, and the yield of the target product of other bases (potassium methoxide, sodium tert-butoxide, potassium hydroxide and sodium ethoxide) is reduced (entry 2-5); simple screening of the solvent revealed that the desired product was also obtained in the case of aromatic high-boiling solvents (toluene, xylene and mesitylene), but the product selectivity was slightly reduced (entry 6-8).
Example 10 study of the results of hydrogenation reaction with other parameters [a]
TABLE 7 optimization of other parameters for hydrogenation reaction conditions
[a] Reaction conditions N, N '-diformyl-N, N' -dimethylethylenediamine, potassium tert-butoxide, (2 mol%) of formula IV were reacted under 60bar hydrogen pressure for 16h, the conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard. [b] 40bar hydrogen pressure.
Under the protection of argon, the catalyst of the formula IV (2 mol%), potassium tert-butoxide, N, N '-diformyl-N, N' -dimethylethylenediamine and dioxane were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted for 16 hours at the given temperature and hydrogen pressure. After the reaction is finished, cooling with ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and performing GC reaction and 1 h NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 7.
Systematically screening the pressure (entry 1-2), temperature (entry1, 3-5) and alkali amount (entry1, 6) required by the reaction, and obtaining that the alkali amount is required at 60bar, 110 ℃ and 20 mol% when the reaction substrate amount is 0.25 mmol; when the amount of the substrate is increased to 0.5mmol, the amount of the base can be reduced to 2.5%, and when the amount of the solvent is continuously reduced to 0.4mL, the target product (entry 7-10) can be obtained with high yield.
Example 11 investigation of the catalytic hydrogenation reaction conditions of formula VI [a]
TABLE 8 optimization of catalytic hydrogenation reaction conditions for formula VI
[a] The reaction conditions are (0.5mmol) N, N '-diformyl-N, N' -dimethylethylenediamine, potassium tert-butoxide, the formula VII is reacted for 16h under the hydrogen condition, the conversion rate and the yield areIt was determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard. [b] Dioxane (0.5mL). [c] Dioxane (2mL).
Under the protection of argon, the catalyst of the formula VI, potassium tert-butoxide, N, N '-diformyl-N, N' -dimethylethylenediamine (0.5mmol) and dioxane were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted for 16h at the given temperature and hydrogen pressure. After the reaction is finished, cooling with ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and performing GC reaction and 1 h NMR (in CDCl) 3 Deuterated reagent) to quantitatively determine the conversion of starting material and the yield of product.
Systematic screening of the amount of catalyst, the amount of base, the reaction temperature and hydrogen required for the reaction was performed, and the results are shown in table 8, and finally the optimal reaction conditions were obtained, i.e., the target product 1(entry 8) was obtained at a yield of 94% when the amount of catalyst VI was 3 mol%, the amount of base was 5 mol%, the reaction temperature was 180 ℃, and the reaction pressure was 80 bar.
EXAMPLE 12 investigation of solvent dosage on the results of the catalytic hydrogenation of formula IV [a]
TABLE 9 optimization of solvent amounts for the catalytic hydrogenation reaction conditions of formula IV
[a] Reaction conditions (0.5mmol) N, N '-diformyl-N, N' -dimethylethylenediamine, (2.5 mol%) potassium tert-butoxide, (2 mol%) formula IV were reacted under 60bar hydrogen pressure for 16h at a reaction temperature of 110 ℃ and conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard.
Under the protection of argon, the catalyst of formula IV (0.01mmol,2 mol%), potassium tert-butoxide (0.0125 mm)ol,2.5 mol%), N, N '-diformyl-N, N' -dimethylethylenediamine (0.5mmol) and dioxane were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted at 110 ℃ under 60bar hydrogen pressure for 16 hours. After the reaction is finished, cooling with ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and performing GC reaction and 1 h NMR (in CDCl) 3 As deuterated reagent) quantitatively gave the conversion of starting material and the yield of product, as shown in table 9.
The solvent optimization shows that the catalytic hydrogenation reaction solvent of the formula IV can obtain better selectivity even if the solvent is reduced to 0.2 mL.
Example 13 investigation of solvent dosage on the results of the catalytic hydrogenation reaction of formula VI [a]
TABLE 10 optimization of solvent amounts for catalytic hydrogenation reaction conditions of formula VI
[a] The reaction conditions (0.5mmol) N, N '-diformyl-N, N' -dimethylethylenediamine, (5 mol%) potassium tert-butoxide, (3 mol%) formula VI were reacted under 80bar hydrogen pressure for 16h at 180 ℃ with conversion and yield determined by NMR and GC using 1,1,2, 2-tetrachloroethane as internal standard.
Under the protection of argon, the catalyst of the formula VI (0.015mmol,3 mol%), potassium tert-butoxide (0.025mmol,5 mol%), N, N '-diformyl-N, N' -dimethylethylenediamine (0.5mmol) and dioxane were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted at 180 ℃ under a hydrogen pressure of 80bar for 16 hours. After the reaction is finished, cooling the reaction product by ice water, slowly releasing the hydrogen in the autoclave, and adding 1,1,2, 2-tetrachloroethane into a liquid phase systemAlkane as internal standard by GC and 1 h NMR (in CDCl) 3 Deuterated reagent) quantitatively yields the conversion of starting material and the yield of product.
The solvent optimization shows that the catalytic hydrogenation reaction solvent of the formula VI can obtain better selectivity even if the solvent is reduced to 0.3 mL.
Example 14, Experimental study of the poisoning reaction of dehydrogenation reaction of catalyst of formula VI [a]
TABLE 11 comparison of dehydrogenation ligand poisoning results
[a] The reaction conditions (0.25mmol) of N, N' -dimethylethylenediamine, (6eq,1.5mmol) of methanol, (4 mol%) of potassium tert-butoxide, (2 mol%) of catalyst, (0.4mL) of dioxane and additives were reacted in a 25mL pressure-tight tube for 16h at 165 ℃ with conversion and yield determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard.
Under the protection of argon, the catalyst of formula VI (0.005mmol,2 mol%), potassium tert-butoxide (0.01mmol,4 mol%), N, N' -dimethylethylenediamine (0.25mmol), methanol (1.5mmol,6equiv.), dioxane (0.4mL) and additives (equivalent to the catalyst) were added successively to a 25mL tube block containing a magnetic stirrer and reacted at 165 ℃ for 16 h. After the reaction, the reaction mixture was cooled with ice water, and 1,1,2, 2-tetrachloroethane was added to the liquid phase system as an internal standard, followed by GC and 1 h NMR (in CDCl) 3 Deuterated reagent) to quantitatively determine the conversion of starting material and the yield of product.
The above results show that the addition of Hg or PMe, the poisoning agents 3 The conversion and yield of the whole catalytic reaction are not affected at all, which indicates that the catalytic dehydrogenation reaction is a homogeneous reaction process.
Example 15 catalyst hydrogen of formula IVChemical poisoning experiment reaction study [a]
TABLE 12 comparison of poisoning results for formula IV catalytically hydrogenated ligands
[a] Reaction conditions (0.5mmol) N, N '-diformyl-N, N' -dimethylethylenediamine, (2.5 mol%) potassium tert-butoxide, (2 mol%) formula IV, (2mL) dioxane and additives were reacted under 60bar hydrogen pressure for 16h at a reaction temperature of 150 ℃ and conversion and yield were determined by NMR and GC using 1,1,2, 2-tetrachloroethane as an internal standard.
Under the protection of argon, the catalyst of formula IV (0.005mmol,2 mol%), base (0.0125mmol,2.5 mol%), N, N '-diformyl-N, N' -dimethylethylenediamine (0.5mmol), dioxane (2mL) and additives (equivalent to the catalyst) were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted at 110 ℃ under a hydrogen pressure of 60bar for 16 h. After the reaction is finished, cooling the mixture by ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and carrying out GC and GC 1 H NMR (in CDCl) 3 Deuterated reagent) quantitatively yields the conversion of starting material and the yield of product.
The above results show that the addition of Hg or PMe, the poisoning agent 3 The conversion and yield of the whole catalytic reaction are not affected at all, which shows that the catalytic hydrogenation reaction of the formula IV is a homogeneous reaction process.
EXAMPLE 16 toxicity test reaction study of hydrogenation of catalyst of formula VI [a]
TABLE 13 comparison of poisoning results for catalytic hydrogenation ligands of formula VI
[a] The reaction conditions (0.5mmol) N, N '-diformyl-N, N' -dimethylethylenediamine, (5 mol%) potassium tert-butoxide, (3 mol%) formula VI and the additive were reacted under 80bar hydrogen pressure for 16h at 180 ℃ with conversion and yield determined by NMR and GC using 1,1,2, 2-tetrachloroethane as internal standard.
Under the protection of argon, the catalyst of formula VI (0.015mmol,3 mol%), base (0.025mmol,5 mol%), N, N '-diformyl-N, N' -dimethylethylenediamine (0.5mmol), dioxane (1mL) and additives (equivalent to the catalyst) were added successively to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reaction vessel and reacted at 180 ℃ under a hydrogen pressure of 80bar for 16 h. After the reaction is finished, cooling the mixture by ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and carrying out GC and GC 1 H NMR (in CDCl) 3 Deuterated reagent) quantitatively yields the conversion of starting material and the yield of product.
The above results show that the addition of Hg or PMe, the poisoning agent 3 The conversion and yield of the entire catalytic reaction were not adversely affected, indicating that the catalytic hydrogenation of formula VI is a homogeneous reaction.
Example 17 manganese catalyzed reversible conversion study between diamine-methanol and diamide
The reaction equation for manganese catalyzed reversible conversion between diamine-methanol and diamide is shown below:
the first condition is as follows: under the protection of argon, the catalyst of formula VI (0.01mmol,2 mol%), potassium tert-butoxide (0.02mmol,4 mol%), N, N' -dimethylethylDiamine (0.5mmol), methanol (3mmol,6equiv.) and dioxane (0.4mL) are added into a 25mL sealed tube containing a magnetic stirrer in sequence, the reaction is carried out at 165 ℃ for 4 hours, the generated gas of the reaction system is released for further reaction for 6 hours, after the reaction is finished, the reaction is cooled to room temperature, the dehydrogenation reaction system is transferred into a 10mL reaction bottle added with a catalyst (0.01mmol,2 mol%) of the formula IV and potassium tert-butoxide (0.0125mmol,2.5 mol%) in a glove box, and the reaction bottle is transferred into a reaction kettle to react for 16 hours at 110 ℃ under 60bar hydrogen pressure. After the reaction is finished, 1,2, 2-tetrachloroethane is added into a liquid phase system as an internal standard, and GC and 1 HNMR (in CDCl) 3 Deuterated reagent) to quantitatively determine the conversion of starting material and the yield of product.
And a second condition: under the protection of argon, the catalyst of the formula VI (0.01mmol,2 mol%), potassium tert-butoxide (0.02mmol,4 mol%), N, N' -dimethylethylenediamine (0.5mmol), methanol (3mmol,6equiv.) and dioxane (0.4mL) were added successively to a 25mL sealed tube containing a magnetic stirrer, the reaction was carried out at 165 ℃ for 4 hours, the generated gas in the reaction system was released and continued to react for 6 hours, after the reaction was completed, the reaction was cooled to room temperature and the dehydrogenation reaction system was transferred to a 10mL reaction flask into which the catalyst of the formula VI (0.015mmol,3 mol%), potassium tert-butoxide (0.025mmol,5 mol%) and dioxane (0.6mL) had been added, the reaction flask was transferred to a reaction vessel and reacted for 16 hours at 180 ℃ under a hydrogen pressure of 80 bar. After the reaction is finished, 1,2, 2-tetrachloroethane is added into a liquid phase system as an internal standard, and GC and 1 h NMR (in CDCl) 3 Deuterated reagent) quantitatively yields the conversion of starting material and the yield of product.
As can be seen from the above reaction equation, reversible conversion can be realized between diamine-methanol and diamide through dehydrogenation and hydrogenation, and interconversion can be realized under mild conditions by using formula IV for hydrogenation after dehydrogenation; in contrast, hydrogenation using formula VI after dehydrogenation requires more severe conditions (higher pressure, higher temperature) to achieve interconversion.
EXAMPLE 18N-Me protected manganese catalyst Studies during hydrogenation and dehydrogenation conversions
Formula VII (0.005mmol,2 mol%), potassium tert-butoxide (0.01mmol,4 mol%), N' -dimethylethylenediamine (0.25mmol), methanol (1.5mmol,6equiv.) and dioxane (0.4mL) were added one after the other to a 25mL tube seal containing a magnetic stirrer under argon and reacted at 165 ℃ for 16 h. After the reaction is finished, cooling with ice water, slowly releasing gas generated in the sealed tube, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and performing GC and 1 h NMR (in CDCl) 3 Deuterated reagent) quantitatively yields the conversion of starting material and the yield of product.
Formula VII (0.015mmol,3 mol%), potassium tert-butoxide (0.025mmol,5 mol%), N '-diformyl-N, N' -dimethylethylenediamine (0.5mmol) and dioxane (1mL) were added one after the other under a blanket of argon to a 10mL vial containing a magnetic stirrer, and an aluminum alloy tray containing seven vials was placed in a 300mL reactor and reacted at 180 ℃ under 80bar hydrogen pressure for 16 h. After the reaction is finished, cooling with ice water, slowly releasing hydrogen in the autoclave, adding 1,1,2, 2-tetrachloroethane as an internal standard into a liquid phase system, and performing GC reaction and 1 h NMR (in CDCl) 3 Deuterated reagent) quantitatively yields the conversion of starting material and the yield of product.
From the above results, it is considered that the change of the N-H structure to N-Me has a great influence on the occurrence of both the dehydrogenation reaction and the hydrogenation reaction. The conversion rate, the yield and the selectivity are all reduced obviously, so that the existence of the N-H structure in the ligand plays an important role in the occurrence of dehydrogenation and hydrogenation reactions.
Example 19 study of the mechanism of catalytic dehydrogenation reaction of manganese
To further study the reaction mechanism of the dehydrogenation reaction, a series of control experiments were performed.
First, the reaction was run using methanol under standard conditions and the formation of only a small amount of methyl formate was monitored, indicating that methyl formate may not be a reaction intermediate for the reaction (18 a); the reaction was carried out under standard conditions using paraformaldehyde instead of methanol, and the formation of the monoamide and diamide products could be detected, indicating that formaldehyde is likely to be an intermediate in the dehydrogenation reaction (18 b); synthesis of monoamide dehydrogenation reaction under standard conditions, can get the diamide product with 92% high yield, which indicates that monoamide may be the intermediate (18c) of dehydrogenation reaction to generate diamide product; also, a control experiment without adding a catalyst was attempted, and the formation of the objective product could not be detected with diamine and paraformaldehyde under the catalyst-free condition but the formation of the cyclized product 3 could be obtained in a yield of 25% (18d), but the formation of the cyclized product 3 could not be detected when the catalyst-free experiment was performed with the monoamide (18e), indicating that the cyclized product 3 was formed in situ from diamine and formaldehyde under the catalyst-free condition. The above control experiment can be advantageously carried out to further presume the mechanism of the dehydrogenation reaction.
It can be seen from the above examples that the present invention provides a novel manganese catalytic hydrogenation and dehydrogenation system for realizing reversible conversion of N, N ' -dimethylethylenediamine-methanol and N, N ' -diformyl-N, N ' -dimethylethylenediamine as liquid organic hydrogen storage materials. The hydrogen storage system has a hydrogen storage density of 5.3 percent and can realize a reversible dehydrogenation adding process under the catalysis of manganese; the selectivity of the dehydrogenation system can be up to 97% to obtain the diamide product, and the purity of the generated hydrogen can reach 99.9%. The method has good research value and application prospect.
In this specification, the invention has been described with reference to specific embodiments. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
Claims (7)
1. A method of storing and releasing hydrogen gas comprising the steps of:
1) under the catalysis of a manganese complex, carrying out dehydrogenation reaction on N, N ' -dimethyl ethylenediamine and methanol to obtain N, N ' -diformyl-N, N ' -dimethyl ethylenediamine and hydrogen, and realizing the release of the hydrogen;
2) under the catalysis of the manganese complex, carrying out hydrogenation reaction on N, N ' -diformyl-N, N ' -dimethylethylenediamine and hydrogen to obtain N, N ' -dimethylethylenediamine, and realizing the storage of the hydrogen;
the structure of the manganese complex is shown as formula I-formula VII:
wherein iPr represents an isopropyl group, and Ph represents a phenyl group.
2. The method of claim 1, wherein: in the step 1), the dehydrogenation reaction is carried out in the presence of a strong base;
the using amount of the strong base is 2.7-8% of the molar amount of the N, N' -dimethylethylenediamine;
the solvent of the dehydrogenation reaction is dioxane, toluene, xylene or mesitylene;
the dosage of the solvent is as follows: 0.25 to 1.5mmol of N, N' -dimethylethylenediamine: 0 to 1mL of a solvent.
3. The method according to claim 1 or 2, characterized in that: in the step 1), the use amount of the manganese complex is 1-2% of the molar amount of the N, N' -dimethylethylenediamine;
the dehydrogenation reaction is carried out at the temperature of 150-165 ℃ for 8-16 hours.
4. The method of claim 3, wherein: in the step 2), the hydrogenation reaction is carried out in the presence of a strong base;
the using amount of the strong base is 2.5-20% of the molar amount of the N, N '-diformyl-N, N' -dimethylethylenediamine;
the solvent of the hydrogenation reaction is dioxane, toluene, xylene or mesitylene;
the dosage of the solvent is as follows: 0.25 to 0.5mmol of N, N '-diformyl-N, N' -dimethylethylenediamine: 0.2-2 mL of a solvent.
5. The method of claim 4, wherein: in the step 2), the using amount of the manganese complex is 2-3% of the molar amount of the N, N '-diformyl-N, N' -dimethylethylenediamine;
the temperature of the hydrogenation reaction is 90-180 ℃, and the time is 6-16 hours.
6. An organic liquid hydrogen storage system for storing and releasing hydrogen gas comprising:
1) n, N' -dimethylethylenediamine and methanol;
2) n, N '-diformyl-N, N' -dimethylethylenediamine;
3) a manganese complex;
under the catalysis of the manganese complex, the N, N' -dimethylethylenediamine and the methanol are subjected to a dehydrogenation reaction to release hydrogen; the N, N '-diformyl-N, N' -dimethylethylenediamine is subjected to a hydrogenation reaction to store hydrogen under the catalysis of the manganese complex;
the structure of the manganese complex is shown as formula I-formula VII:
wherein iPr represents an isopropyl group, and Ph represents a phenyl group.
7. Use of a manganese complex to catalyze the dehydrogenation and hydrogenation reactions of a liquid organic hydrogen storage material to produce and store hydrogen gas;
the liquid organic hydrogen storage material comprises the following components:
1) a mixture of N, N' -dimethylethylenediamine and methanol;
2) n, N '-diformyl-N, N' -dimethylethylenediamine;
the structure of the manganese complex is shown as formula I-formula VII:
wherein iPr represents an isopropyl group, and Ph represents a phenyl group.
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