Method for preparing lignin-based quinoxaline through one-pot two-step catalysis of acidic HZSM-5-triethylamine
Through a one-pot two-step process of acidic HZSM-5 and triethylamine catalyst, the reaction of lignin and molded substances with orthophenyldiamine was solved by solving the problem of quinoxaline synthesis on fossil resource dependence and strong alkali use, and achieving a green and economical preparation of quinoxaline.
Patent Information
- Application Number
- CN202510442057.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-09
- Publication Date
- 2025-08-08
AI Technical Summary
The existing quinoxaline synthesis method relies on fossil resource-based chemicals, and the use of strong alkaline systems is prone to environmental pollution and is difficult to achieve sustainable development.
Acid HZSM-5 and triethylamine were used as catalysts, and lignin and lignin β-O-4 molded substances were used to react with orthophenyldiamine through a one-pot two-step process to avoid external hydrogenation and oxygen sources, forming quinoxaline.
It has achieved the preparation of lignin-based quinoxaline at lower temperatures with cheap and easy-to-access catalysts, which reduces energy consumption and environmental impacts and has a good economic competitive advantage.
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Figure CN120441494A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of biomass resources, and in particular to a method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine. Background Art
[0002] Quinoxaline is an important class of nitrogen-containing heterocyclic compounds with extensive applications and markets in drug synthesis, dye and pigment preparation, material preparation, fine synthetic chemistry, and natural products. Currently, commercial quinoxaline synthesis methods primarily utilize fossil resource-based chemicals, such as aromatic monomers such as 1,2-diketones, 1,2-diols, α-hydroxyketones, and epoxides, resulting in a high reliance on fossil resources. Patents filed and research literature published in recent years also mostly utilize aromatic monomers, such as aromatic glyoxals and α-carbonyl esters, to react with o-phenylenediamine to prepare quinoxaline or quinoxalinone, yet remain reliant on fossil resource-based raw materials.
[0003] Lignin contains a large number of aromatic structures and β-O-4 bonds. In recent years, lignin and β-O-4 moieties have been studied for the synthesis of nitrogen-containing heterocyclic compounds, including quinoxaline. The route for synthesizing quinoxaline using lignin and β-O-4 moieties is as follows:
[0004]
[0005] However, most reported routes for synthesizing quinoxaline from lignin and its moieties utilize strongly alkaline systems such as NaOH and KOH. The use of large amounts of base can easily lead to environmental pollution and reuse issues. Therefore, developing new pathways for preparing quinoxaline from lignin and β-O-4 moieties is an important approach to the sustainable development of lignin as a renewable resource and a key task in developing green synthetic routes for quinoxaline. Summary of the Invention
[0006] In view of the deficiencies in the above-mentioned prior art, the object of the present invention is to provide a method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine. The present invention adopts a one-pot two-step method using lignin and lignin β-O-4 model and o-phenylenediamine as raw materials. First, without the need for an external hydrogen source or oxygen source, HZSM-5 is used as a catalyst to catalyze the carbon-oxygen bond cleavage and oxygen transfer of lignin and the model to obtain intermediate monomer phenol and phenylacetaldehyde compounds. The obtained phenylacetaldehyde structure continues to react with o-phenylenediamine under the catalytic action of triethylamine. The aldehyde carbon and benzyl carbon respectively form a C-N bond with the two nitrogen atoms of o-phenylenediamine, and then undergo dehydrogenation to form 2-phenylquinoxaline. The present invention uses HZSM-5 and triethylamine as catalysts, and uses lignin and its model as raw materials to prepare 2-phenylquinoxaline in one-pot two-step. The catalyst is cheap and easy to obtain, the acid position is easy to control, and the use of a strong base system is effectively avoided. It meets the requirements of sustainable development and green economy and has excellent promotion and application prospects.
[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:
[0008] A method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine comprises the following steps:
[0009] (1) placing lignin or lignin β-O-4 model and HZSM-5 catalyst in a reaction vessel, adding a solvent to the reaction vessel and stirring and mixing;
[0010] (2) replacing the air in the reaction vessel with nitrogen, then filling it with nitrogen and sealing the reaction vessel;
[0011] (3) Place the sealed reaction vessel in an electric furnace, heat to 100°C to 260°C with stirring, and keep warm for 0.5h to 12h, then cool to room temperature;
[0012] (4) triethylamine and o-phenylenediamine are added to the reaction system of step (3), and then placed in an electric heating furnace again to carry out nitrogen-containing heterocyclic ring formation reaction. Under stirring conditions, the reaction system is heated to 35° C. to 100° C. and kept warm for 0.5 h to 8 h, and then cooled to room temperature to obtain lignin-based quinoxaline.
[0013] Optionally, in step (1), the ratio of the lignin β-O-4 model to HZSM-5 is (0.4-5):40 mmol / mg, and the ratio of the lignin sample to HZSM-5 is 0.1 g:40 mg.
[0014] Optionally, the silicon-aluminum molar ratio of the HZSM-5 catalyst is SiO2 / Al2O3=(5-200):1.
[0015] Optionally, the HZSM-5 catalyst is an untreated HZSM-5 catalyst or a HZSM-5 catalyst loaded with metal ions; the metal ions include at least one of iron, cobalt, copper, and palladium.
[0016] Optionally, the reaction vessel is a reactor, a pressure-resistant tube or other sealed and stirred reaction container.
[0017] Optionally, in step (1), the solvent includes one or more organic solvents such as toluene, cyclohexane, n-hexane, methanol, ethanol, isopropanol, acetone, ethyl acetate, tetrahydrofuran, dichloroethane, 1,4-dioxane, and hexafluoroisopropanol.
[0018] Optionally, in step (1), the ratio of the lignin or the lignin β-O-4 model to the solvent is (0.4-50):(5-20) mmol / ml.
[0019] Optionally, in step (2), the pressure of the nitrogen gas charged is 0 MPa to 1 MPa.
[0020] Optionally, in step (3), the stirring speed is 400 r / min; in step (4), the stirring speed is 600 r / min.
[0021] Optionally, in step (4), the amount of triethylamine used is 0.6 to 4 μl / ml solvent; o-phenylenediamine includes unsubstituted o-phenylenediamine or o-phenylenediamine monosubstituted at the 4-position or disubstituted at the 4-position and 5-position by one or more of alkyl, alkoxy, hydroxyl, and halogen; and the molar ratio of the o-phenylenediamine to lignin or lignin β-O-4 model is >1.1:1.
[0022] Optionally, in step (1), the stirring and mixing method can be magnetic stirring, mechanical physical stirring, ultrasonic vibration, etc.
[0023] Optionally, after the reaction is completed, the reactor is cooled to room temperature, the liquid in the reactor is taken out, 0.02 g of biphenyl is added as an internal standard, and quinoxaline is quantified by gas chromatography.
[0024] Optionally, the gas chromatography detection conditions are: C18 capillary column, starting temperature 45°C, hold for 2 min; heating to 280°C at 15°C / min, hold for 5 min; FID detector temperature set to 300°C, carrier gas flow rate 1.6 ml / min.
[0025] Compared with the prior art, the present invention has the following beneficial effects:
[0026] The present invention utilizes renewable resources lignin and lignin β-O-4 modules as raw materials, and prepares lignin-based quinoxaline through a one-pot two-step method with o-phenylenediamine. First, the present invention uses HZSM-5 and triethylamine as catalysts, effectively avoiding the use of a strong base system, which meets the requirements of sustainable development and green economy. Secondly, the present invention uses commercial molecular sieve HZSM-5 as a catalyst, which has low production cost and is cheap and easy to obtain, which is conducive to the promotion and application of the invention technology and effectively improves the economic cost advantage of lignin-based quinoxaline in market competition; thirdly, the change of HZSM-5 silicon-aluminum ratio can effectively adjust the acidic position of the catalyst, thereby regulating the reaction rate and reaction temperature. In addition, the present invention can achieve the depolymerization of lignin β-O-4 modules at a lower temperature without the need for external hydrogen and oxygen sources, and then react with o-phenylenediamine to form quinoxaline, effectively reducing the energy consumption cost of the technology. In summary, the present invention adopts a one-pot two-step method, using inexpensive HZSM-5 and triethylamine as catalysts to convert lignin and lignin β-O-4 model raw materials into lignin-based quinoxaline, which has a large economic cost competitive advantage and has excellent application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 The present invention shows a reaction pathway diagram of the method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine.
[0028] Figure 2 This is a reaction pathway diagram of Example 1 of the present invention.
[0029] Figure 3 This is the gas chromatogram of the product of Example 1 of the present invention.
[0030] Figure 4 The mass spectrum of the quinoxaline product in Example 1 of the present invention is compared with the standard spectrum. DETAILED DESCRIPTION
[0031] The following is a detailed description of the technical solutions in the embodiments of the present invention, using preferred embodiments and accompanying drawings in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0032] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.
[0033] Example 1
[0034] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0035] (2) Measure 15 ml of toluene, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0036] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0037] (4) Place the sealed reaction vessel in an electric furnace, heat to 180°C at 400 r / min with continuous stirring, and maintain at the set temperature for 30 minutes.
[0038] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0039] (6) 45 μl of triethylamine and 0.52 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0040] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0041] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 100%, and the structure of quinoxaline was:
[0042]
[0043] The yield was 0.0819 g.
[0044] Comparative Example 1
[0045] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of p-toluenesulfonic acid and place them in a reaction kettle.
[0046] (2) Measure 15 ml of toluene, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0047] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0048] (4) Place the sealed reaction vessel in an electric furnace, heat to 180°C at 400 r / min with continuous stirring, and maintain at the set temperature for 30 minutes.
[0049] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0050] (6) 45 μl of triethylamine and 0.52 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0051] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0052] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 54% and the quinoxaline yield was 0 g.
[0053] Comparative Example 2
[0054] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of all-silicon HZSM-5 catalyst and place them in a reactor.
[0055] (2) Measure 15 ml of toluene, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0056] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0057] (4) Place the sealed reaction vessel in an electric furnace, heat to 180°C at 400 r / min with continuous stirring, and maintain at the set temperature for 30 minutes.
[0058] (5) After the reaction is completed, the reaction vessel is cooled to room temperature;
[0059] (6) 45 μl of triethylamine and 0.52 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0060] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0061] (8) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. After gas chromatography analysis, the substrate conversion rate was 0%.
[0062] Comparative Example 3
[0063] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0064] (2) Measure 15 ml of toluene, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0065] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0066] (4) Place the sealed reaction vessel in an electric furnace, heat to 180°C at 400 r / min with continuous stirring, and maintain at the set temperature for 30 minutes.
[0067] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0068] (6) 0.52 mmol of o-phenylenediamine was weighed and added to the above reaction solution.
[0069] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0070] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 100% and the quinoxaline yield was 0 g.
[0071] Example 2
[0072] (1) Weigh 0.51 mmol of 1-hydroxy-2-phenoxy-(4'-methoxy)-ethylbenzene and 40 mg of copper-supported HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 5:1 and place them in a reactor.
[0073] (2) Measure 15 ml of cyclohexane, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0074] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0075] (4) Place the sealed reaction vessel in an electric furnace, heat to 180°C at 400 r / min with continuous stirring, and maintain at the set temperature for 30 minutes.
[0076] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0077] (6) 25 μl of triethylamine and 0.66 mmol of 4-methyl-o-phenylenediamine were weighed and added to the above reaction solution.
[0078] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0079] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 100%, and the structure of quinoxaline was:
[0080]
[0081] The yield was 0.1013 g.
[0082] Example 3
[0083] (1) Weigh 0.50 mmol of 1-hydroxy-2-(2'-methoxy)phenoxy-ethylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 200:1 and place them in a reactor.
[0084] (2) Measure 10 ml of methanol, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0085] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0086] (4) Place the sealed reaction vessel in an electric furnace, heat to 260°C at 400 r / min with continuous stirring, and maintain at the set temperature for 6 h.
[0087] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0088] (6) 9 μl of triethylamine and 0.67 mmol of 4-hydroxy-o-phenylenediamine were weighed and added to the above reaction solution.
[0089] (7) The reaction vessel was placed in the electric furnace again, heated to 35°C at 600 r / min with continuous stirring, and maintained at the set temperature for 8 h.
[0090] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 100%, and the structure of quinoxaline was:
[0091]
[0092] The yield was 0.0924 g.
[0093] Example 4
[0094] (1) Weigh 0.52 mmol of 1,3-dihydroxy-2-(2'-methoxy)phenoxy-(3',4'-dimethoxy)propylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0095] (2) Measure 15 ml of n-hexane, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0096] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, nitrogen at 0 MPa was filled in and the reaction vessel was sealed.
[0097] (4) Place the sealed reaction vessel in an electric furnace, heat to 100°C at 400 r / min with continuous stirring, and maintain at the set temperature for 12 h.
[0098] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0099] (6) 45 μl of triethylamine and 0.63 mmol of 4-fluoro-o-phenylenediamine were weighed and added to the above reaction solution.
[0100] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 4 h.
[0101] (8) After the reaction was completed, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. After gas chromatography analysis, the substrate conversion rate was 84%, and the structure of quinoxaline was:
[0102]
[0103] The yield was 0.0329 g.
[0104] Example 5
[0105] (1) Weigh 5.00 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0106] (2) Measure 15 ml of ethanol, pour it into the reactor, stir and mix at 400 r / min for 2 minutes, and assemble the reaction vessel.
[0107] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0108] (4) Place the sealed reaction vessel in an electric furnace, heat to 240°C at 400 r / min with continuous stirring, and maintain at the set temperature for 4 h.
[0109] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0110] (6) 45 μl of triethylamine and 6.72 mmol of 4-methoxy-o-phenylenediamine were weighed and added to the above reaction solution.
[0111] (7) The reaction vessel was placed in the electric furnace again, heated to 60°C at 600 r / min with continuous stirring, and maintained at the set temperature for 6 h.
[0112] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 95%, and the structure of quinoxaline was:
[0113]
[0114] The yield was 0.9230 g.
[0115] Example 6
[0116] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a pressure-resistant reaction tube.
[0117] (2) Measure 10 ml of hexafluoroisopropanol, pour it into the pressure-resistant reaction tube, stir and mix at 400 r / min for 2 minutes, and assemble the reaction vessel.
[0118] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0119] (4) Place the sealed reaction vessel in an electric furnace, heat to 120°C at 400 r / min with continuous stirring, and maintain at the set temperature for 8 h.
[0120] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0121] (6) Measure 6 μl of triethylamine and 0.53 mmol of 4,5-dibromo-o-phenylenediamine and add them to the above reaction solution.
[0122] (7) The reaction vessel was placed in the electric furnace again, heated to 60°C at 600 r / min with continuous stirring, and maintained at the set temperature for 6 h.
[0123] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the pressure-resistant reaction tube was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 89%, and the structure of quinoxaline was:
[0124]
[0125] The yield was 0.1463 g.
[0126] Example 7
[0127] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of iron-supported HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0128] (2) Measure 15 ml of acetone, pour it into the reactor, stir and mix at 400 r / min for 2 minutes, and assemble the reaction vessel.
[0129] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0130] (4) Place the sealed reaction vessel in an electric furnace, heat to 250°C at 400 r / min with continuous stirring, and maintain at the set temperature for 4 h.
[0131] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0132] (6) 45 μl of triethylamine and 0.54 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0133] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0134] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 100%, and the structure of quinoxaline was:
[0135]
[0136] The yield was 0.0317 g.
[0137] Example 8
[0138] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of cobalt-supported HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0139] (2) Measure 5 ml of ethyl acetate, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0140] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0141] (4) Place the sealed reaction vessel in an electric furnace, heat to 230°C at 400 r / min with continuous stirring, and maintain at the set temperature for 2 h.
[0142] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0143] (6) 45 μl of triethylamine and 0.62 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0144] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0145] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 72%, and the structure of quinoxaline was:
[0146]
[0147] The yield was 0.0446 g.
[0148] Example 9
[0149] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of palladium-supported HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0150] (2) Measure 15 ml of tetrahydrofuran, pour it into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0151] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0152] (4) Place the sealed reaction vessel in an electric furnace, heat to 230°C at 400 r / min with continuous stirring, and maintain at the set temperature for 2 h.
[0153] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0154] (6) 45 μl of triethylamine and 0.53 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0155] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0156] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 58%, and the structure of quinoxaline was:
[0157]
[0158] The yield was 0.0116 g.
[0159] Example 10
[0160] (1) Weigh 0.47 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0161] (2) Measure 15 ml of 1,4-dioxane, pour it into the reactor, stir and mix at 400 r / min for 2 minutes, and assemble the reaction vessel.
[0162] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0163] (4) Place the sealed reaction vessel in an electric furnace, heat to 250°C at 400 r / min with continuous stirring, and maintain at the set temperature for 6 h.
[0164] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0165] (6) 45 μl of triethylamine and 0.60 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0166] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0167] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 83%, and the structure of quinoxaline was:
[0168]
[0169] The yield was 0.0622 g.
[0170] Example 11
[0171] (1) Weigh 0.46 mmol of 1-hydroxy-2-phenoxyethylbenzene and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0172] (2) Measure 15 ml of dichloroethane, pour it into the reactor, stir and mix at 400 r / min for 2 minutes, and assemble the reaction vessel.
[0173] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0174] (4) Place the sealed reaction vessel in an electric furnace, heat to 140°C at 400 r / min with continuous stirring, and maintain at the set temperature for 2 h.
[0175] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0176] (6) 45 μl of triethylamine and 0.56 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0177] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0178] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 100%, and the structure of quinoxaline was:
[0179]
[0180] The yield was 0.0854 g.
[0181] Example 12
[0182] (1) Weigh 0.1 g of lignin and 40 mg of HZSM-5 catalyst with a SiO2 / Al2O3 molar ratio of 25:1 and place them in a reactor.
[0183] (2) Measure 5 ml of 1,4-dioxane and 10 ml of toluene, pour them into the reactor, stir and mix at 400 r / min for 2 min, and assemble the reaction vessel.
[0184] (3) The air in the reaction vessel was replaced with nitrogen three times. After the air replacement was completed, 1 MPa of nitrogen was filled in and the reaction vessel was sealed.
[0185] (4) Place the sealed reaction vessel in an electric furnace, heat to 140°C at 400 r / min with continuous stirring, and maintain at the set temperature for 2 h.
[0186] (5) After the reaction is completed, the reaction vessel is cooled to room temperature.
[0187] (6) 45 μl of triethylamine and 0.53 mmol of o-phenylenediamine were weighed and added to the above reaction solution.
[0188] (7) The reaction vessel was placed in the electric furnace again, heated to 80°C at 600 r / min with continuous stirring, and maintained at the set temperature for 2 h.
[0189] (8) After the reaction, the reactor was cooled to room temperature, the liquid in the reactor was taken out, and 0.02 g of biphenyl was added as an internal standard. Gas chromatography analysis showed that the substrate conversion rate was 100%, and the structure of quinoxaline was:
[0190]
[0191] The total yield was 0.0084 g.
[0192] Results and technical analysis:
[0193] The results of Examples 1 to 12 show that lignin-based quinoxaline can be successfully obtained by a one-pot two-step method using lignin and lignin β-O-4 modules as raw materials, HZSM-5 with a SiO2 / Al2O3 molar ratio of 5 to 200, and triethylamine as catalysts. The invention has good universal performance for different substituted lignin β-O-4 modules and o-phenylenediamine substituted products, and can be applied to the conversion of real lignin to obtain lignin-based quinoxaline. Different solvents are used in the reaction process. Due to differences in solvent solubility and polarity, as well as adsorption capacity with the catalyst, the corresponding optimal reaction conditions and reaction efficiency will be different, but the effect on the reaction route is not obvious. That is, all of them are generated by β-O-4 bond cleavage and oxygen transfer to form a phenylacetaldehyde structure intermediate, which then reacts with o-phenylenediamine to form a quinoxaline nitrogen-containing heterocycle. The results of Example 1 and Comparative Examples 1-2 show that the acid sites in HZSM-5 catalyze the cleavage of β-O-4 bonds and the transfer of oxygen to form phenylacetaldehyde structures, and that proton acid has a certain effect on the depolymerization of lignin and the model, but cannot effectively obtain a quinoxaline structure. This indicates that the catalytic function of the acid sites in HZSM-5 does not affect the catalytic effect of triethylamine or has a synergistic effect with triethylamine, otherwise the quinoxaline structure cannot be obtained. In Comparative Example 3, there is no catalytic effect of triethylamine, and no quinoxaline structure is obtained. In summary, a method for preparing lignin-based quinoxaline in a one-pot, two-step catalysis using acidic HZSM-5 and triethylamine is feasible and has good universality. It is friendly to the requirements of solvent system, reaction temperature, and reaction atmosphere, the catalyst is inexpensive and readily available, and the reproducibility is good. It meets the requirements of green economic development and has broad potential for promotion and application.
[0194] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.
Claims
1. A method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine, characterized in that: The following steps are involved: (1) placing lignin or lignin β-O-4 model and HZSM-5 catalyst in a reaction vessel, adding a solvent to the reaction vessel and stirring and mixing; (2) replacing the air in the reaction container with nitrogen, then filling it with nitrogen and sealing the reaction container; (3) Place the sealed reaction vessel in an electric furnace, heat to 100°C to 260°C with stirring, and keep warm for 0.5h to 12h, then cool to room temperature; (4) triethylamine and o-phenylenediamine are added to the reaction system of step (3), and then placed in an electric heating furnace again to carry out nitrogen-containing heterocyclic ring formation reaction. Under stirring conditions, the reaction system is heated to 35° C. to 100° C. and kept warm for 0.5 h to 8 h, and then cooled to room temperature to obtain lignin-based quinoxaline.
2. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: In step (1), the ratio of the lignin β-O-4 model to HZSM-5 is (0.4-5):40 mmol / mg, and the ratio of the lignin sample to HZSM-5 is 0.1 g:40 mg.
3. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: The silicon-aluminum molar ratio of the HZSM-5 catalyst is SiO2 / Al2O3=(5-200):
1.
4. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: The HZSM-5 catalyst is an untreated HZSM-5 catalyst or a HZSM-5 catalyst loaded with metal ions; the metal ions include at least one of iron, cobalt, copper and palladium.
5. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: The reaction container is a reactor, a pressure-resistant tube or other sealed and stirred reaction container.
6. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: In step (1), the solvent includes one or more organic solvents such as toluene, cyclohexane, n-hexane, methanol, ethanol, isopropanol, acetone, ethyl acetate, tetrahydrofuran, dichloroethane, 1,4-dioxane, hexafluoroisopropanol, etc.
7. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: In step (1), the ratio of the lignin or the lignin β-O-4 model to the solvent is (0.4-50):(5-20) mmol / ml.
8. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: In step (2), the pressure of the nitrogen gas charged is 0 MPa to 1 MPa.
9. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: In step (3), the stirring speed is 400 r / min; in step (4), the stirring speed is 600 r / min.
10. The method for preparing lignin-based quinoxaline by one-pot two-step catalysis using acidic HZSM-5-triethylamine according to claim 1, characterized in that: In step (4), the amount of triethylamine used is 0.6-4 μl / ml solvent; O-phenylenediamine includes unsubstituted o-phenylenediamine or o-phenylenediamine monosubstituted at the 4-position or disubstituted at the 4-position and 5-position by one or more of alkyl, alkoxy, hydroxyl, and halogen; The molar ratio of the o-phenylenediamine to the lignin or the lignin β-O-4 module is greater than 1.1:1.