Biomass-based catalyst prepared by taking lignin as raw material and research on catalysis of conversion of CO2 by biomass-based catalyst

Abstract

The invention relates to a synthesis process of a biomass-based catalyst, and belongs to the technical field of chemical engineering. The specific preparation process comprises the following steps: dissolving 99% of acrylamide (AM), 75% of methacryloyloxyethyl trimethyl ammonium chloride (DMC) and 90% of 4-chloromethyl styrene (CS) in a certain proportion in deionized water, then adding ammonium persulfate (APS) as an initiator to synthesize CPA, and then mixing sodium lignin sulfonate (KL) and CPA according to a certain proportion to synthesize KL-CPA. The KL-CPA catalyst synthesized by KL and CPA with different contents is used for the cycloaddition reaction of CO2 and epoxide, and the catalyst is low in cost and environmentally friendly, has thermal stability, chemical stability and mechanical stability, and shows excellent conversion rate, selectivity and universality at normal temperature and pressure.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical industry, and relates to preparation of a biomass-based catalyst with lignin as a raw material and application of the catalyst to a CO2 cycloaddition reaction. TECHNICAL BACKGROUND

[0002] Lignin is the third largest component of lignocellulose. Due to its high calorific value, lignin is traditionally combusted for energy supply in paper pulp and black liquor. According to incomplete statistics, the annual lignin production capacity is as high as 6.2 billion tons, but the effective utilization rate is less than 1%, and more than 95% of the lignin is directly discharged into rivers or burned as papermaking waste liquid. Since lignin is a kind of non-fossil resource containing aromatic groups and is widely available, mainly produced through plant photosynthesis, it has great development potential. However, due to its complex structure, it is more difficult to study.

[0003] In the twenty-first century with highly developed economy, the main energy applied to life and industry is still traditional fossil fuels such as coal, oil and natural gas. The excessive combustion of fossil fuels is the main reason for global climate change so far, accounting for more than 75% of global greenhouse gas emissions and nearly 90% of all CO2 emissions. Therefore, reducing CO2 in the environment is an urgent matter. In principle, there are three ways to reduce CO2 in the environment, mainly reducing CO2 emissions, CO2 capture and storage (CCS) and CO2 capture and utilization (CCU). At present, the CCS technology is faced with the core problems of high cost and high energy consumption; secondly, there is an environmental risk, if CO2 leaks during transportation, its concentration will increase in the local environment, which may cause damage to the soil environment in the region, ocean acidification, and even CO2 poisoning of the human body. In contrast, the CCU technology is more attractive, the captured CO2 can not only be effectively converted into various valuable products, but also has the advantages of broad economic prospects and low risk. The addition reaction of CO2 and epoxide to form cyclic carbonate is one of the most promising and few industrialized ways to utilize CO2 due to its 100% atom utilization, green and economic method.

[0004] Due to the inherent high thermodynamic stability and kinetic inertness of CO2, catalysts are important factors for its conversion. Lignin is the second largest biomass resource in plants after cellulose, and is a natural renewable aromatic biopolymer with a three-dimensional hyperbranched structure and many active functional groups. In recent years, lignin has been found to have great application potential in functional materials, as it is natural, renewable, and low-cost, and has wide research significance in the field of green catalysts. A variety of lignin cross-linked polymers are designed and synthesized from sodium lignosulfonate for adsorbing heavy metal ions and other pollutants in wastewater. For the first time, the polymer is linked to the cycloaddition reaction of CO2, seeking new ideas for the capture and utilization of CO2. A linear cationic polyacrylamide (CPA) prepolymer with chlorine as the end group is prepared, which is then grafted onto KL to form KL-CPA. KL contains abundant phenolic and alcoholic hydroxyl groups, which can act as natural hydrogen bond donors to activate epoxides for the cycloaddition reaction of CO2 and epoxides. The presence of nucleophile X - (halide) on DMC and a co-catalyst can open the ring of epoxide, and the presence of Lewis base (amino or nitrogen-containing substance) in AM and DMC can further activate CO2 to accelerate the cycloaddition reaction of CO2 and epoxide. Therefore, we choose to synthesize KL-CPA to explore the effect of the synthesis method of the catalyst on the cycloaddition reaction. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a biomass-based catalyst, which has the advantages of simple preparation process, low cost, green environmental protection, mild reaction conditions, high thermal stability of the catalyst, recyclability, universality, and recyclability, and good catalytic ability for the cycloaddition reaction of CO2 and epoxide at normal temperature and pressure.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is:

[0007] A biomass-based catalyst KL-CPA prepared from lignin, comprising the following steps:

[0008] (1) AM (7.1 g), DMC (6.9 g) and CS (0.074 g) are added to a three-necked flask and dissolved in 40 mL of deionized water, and the reaction solution is continuously purged with nitrogen for 30 min;

[0009] (2) APS (0.28 g) is added to the three-necked flask, and the reaction solution is purged with nitrogen for 5 min, and the three-necked flask is placed in an oil bath at 80℃ for 10 h;

[0010] (3) After the reaction is completed, the flask is soaked in cold water for 20 min, the solution is poured into a beaker containing three times the volume of anhydrous ethanol to extract the product, and the white material obtained is freeze-dried for 24 h to obtain purified CPA;

[0011] (4) Different proportions of KL and CPA (3 g) are added to a round-bottom flask and dissolved in 40 mL of deionized water, and placed in an oil bath at 80 DEG C for 4 h;

[0012] (5) After the reaction is completed, it is soaked in cold water for 20 min, and the product is extracted with three times the volume of anhydrous ethanol;

[0013] (6) The product is placed in a dialysis bag with a molecular weight of 14,000 and dialyzed for 72 h, and the gray material obtained is freeze-dried for 24 h to obtain purified KL-CPA.

[0014] The application of a biomass-based catalyst KL-CPA prepared from lignin as a raw material, the obtained catalyst is subjected to a CO2 and epoxide ring addition reaction to prepare a cyclic carbonate, and the specific operation process is as follows:

[0015] As a preferred technical solution, the catalyst needs to be activated in a vacuum drying box at 80 DEG C for 12 h before the ring addition reaction test.

[0016] As a preferred technical solution, tetrabutylammonium bromide (TBAB) is used as a cocatalyst to catalyze the ring addition reaction with propylene oxide (PO) as a substrate.

[0017] As a preferred technical solution, the amount of tetrabutylammonium bromide as a cocatalyst is 0.0162 g.

[0018] As a preferred technical solution, the KL-CPA catalyst is 0.02 g as described above.

[0019] As a preferred technical solution, in the reaction of CO2 and epoxide ring addition to prepare a cyclic carbonate, the reaction temperature is 25-80 DEG C, the CO2 pressure is 0.1 MPa, and the reaction time is 12 h.

[0020] As a preferred technical solution, after the reaction is completed and cooled to room temperature, 4 mL of ethyl acetate is used as a solvent to move the reaction to a 10 mL centrifuge tube, and gas chromatography is used for qualitative and quantitative detection. Compared with the prior art, the technical solution of the present application has the following beneficial effects:

[0021] (1) The KL-CPA is successfully prepared by the step-by-step method, and compared with the one-pot synthesis, the product obtained by the method has higher purity and stronger stability.

[0022] (2) The present application uses sodium lignosulfonate as raw material, and since it is easily soluble in water, the reaction does not need to be alkalized by sodium hydroxide, the method is simple in operation process and shortens the production time.

[0023] (3) The present application uses inexpensive lignin as raw material, realizes waste recycling, and saves the cost of synthetic catalyst.

[0024] (4) The catalyst provided by the present application has been widely used as a flocculating agent in the field of wastewater treatment, and the flocculating agent is first applied to the catalyst of the cycloaddition reaction.

[0025] (5) The catalyst provided by the present application can achieve very high conversion rate and selectivity at normal temperature and pressure in the cycloaddition reaction of CO2 and epoxide, can be used repeatedly, and has universality and can be applied to different epoxides as the substrate of the cycloaddition reaction, greatly reduces industrial energy consumption, and implements the concept of green chemistry. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the infrared spectrum of KL, CPA, KL-CPA catalyst.

[0027] Figure 2 is the infrared spectrum of KL-CPA, KL-CPA-1, KL-CPA-2.

[0028] Figure 3 is the SEM spectrum of CPA, KL-CPA, KL-CPA-1, KL-CPA-2.

[0029] Figure 4 is the thermogravimetric spectrum of KL, CPA, KL-CPA catalyst.

[0030] Figure 5 is the thermogravimetric spectrum of KL-CPA, KL-CPA-1, KL-CPA-2 catalyst.

[0031] Figure 6 is the synthesis path of KL-CPA.

[0032] Figure 7 Table 6 is the elemental analysis of KL, CPA, KL-CPA, KL-CPA-1, KL-CPA-2. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application are further described below in combination with the drawings and technical solutions.

[0034] The specific preparation method of the KL-CPA material synthesized with different content of KL is as follows:

[0035] Example 1:

[0036] Method of preparation of KL-CPA:

[0037] (1) AM (7.1 g), DMC (6.9 g) and CS (0.074 g) were taken in a three neck flask and dissolved in 40 mL of deionized water, the reaction solution was purged with nitrogen gas continuously for 30 min;

[0038] (2) APS (0.28 g) was added to the three neck flask and the reaction solution was purged with nitrogen gas for 5 min, the three neck flask was kept in an oil bath at 80 °C for 10 h;

[0039] (3) After completion of the reaction the flask was soaked in cold water for 20 min, the solution was poured into a beaker containing three times the volume of absolute ethanol to extract the product, the white material obtained was freeze dried for 24 h to get the purified CPA;

[0040] (4) KL (1 g) and CPA (3 g) were taken in a round bottom flask and dissolved in 40 mL of deionized water, kept in an oil bath at 80 °C for 4 h;

[0041] (5) After completion of the reaction it was soaked in cold water for 20 min, the product was extracted with three times the volume of absolute ethanol;

[0042] (6) The product was dialyzed in a dialysis bag of molecular weight fourteen thousand for 72 h, the grey material obtained was freeze dried for 24 h to get the purified KL-CPA.

[0043] Example 2:

[0044] Method of preparation of KL-CPA-1:

[0045] (1) AM (7.1 g), DMC (6.9 g) and CS (0.074 g) were taken in a three neck flask and dissolved in 40 mL of deionized water, the reaction solution was purged with nitrogen gas continuously for 30 min;

[0046] (2) APS (0.28 g) was added to the three neck flask and the reaction solution was purged with nitrogen gas for 5 min, the three neck flask was kept in an oil bath at 80 °C for 10 h;

[0047] (3) After completion of the reaction the flask was soaked in cold water for 20 min, the solution was poured into a beaker containing three times the volume of absolute ethanol to extract the product, the white material obtained was freeze dried for 24 h to get the purified CPA;

[0048] (4) KL (0.5 g) and CPA (3 g) were taken in a round bottom flask and dissolved in 40 mL of deionized water, kept in an oil bath at 80 °C for 4 h;

[0049] (5) After the reaction, immerse in cold water for 20 min, and extract the product with three volumes of anhydrous ethanol;

[0050] (6) Put the product in a dialysis bag with a molecular weight of 14000 for dialysis for 72 h, freeze-dry the obtained gray substance for 24 h to obtain purified KL-CPA.

[0051] Example 3:

[0052] Preparation method of KL-CPA-2:

[0053] (1) Add AM (7.1 g), DMC (6.9 g) and CS (0.074 g) into a three-necked flask and dissolve in 40 mL of deionized water, continuously blow the reaction solution with nitrogen for 30 min;

[0054] (2) Add APS (0.28 g) into the three-necked flask, and blow the reaction solution with nitrogen for 5 min, and place the three-necked flask in an oil bath at 80°C for 10 min;

[0055] (3) After the reaction, immerse in cold water for 20 min, and extract the product with three volumes of anhydrous ethanol, and freeze-dry the obtained white substance for 24 h to obtain purified CPA;

[0056] (4) Add KL (0.5 g) and CPA (3 g) into a round-bottom flask and dissolve in 40 mL of deionized water, and place in an oil bath at 80°C for 4 h;

[0057] (5) After the reaction, immerse in cold water for 20 min, and extract the product with three volumes of anhydrous ethanol;

[0058] (6) Put the product in a dialysis bag with a molecular weight of 14000 for dialysis for 72 h, freeze-dry the obtained gray substance for 24 h to obtain purified KL-CPA.

[0059] Specific operation method of the KL-CPA material for the CO2 and epoxide cycloaddition reaction:

[0060] Weigh 0.02 g of catalyst KL-CPA and 0.0162 g of TBAB in a polytetrafluoroethylene liner on a balance. Add 2 mmol (0.14 mL) of epoxide into the polytetrafluoroethylene liner with a pipette, and fill the reaction kettle with 0.1 MPa of CO2 gas. Place the liner described above in the reaction kettle, heat to 25-80°C, and react for 12 h at a rotation speed of 720 rpm. After cooling to room temperature, move the reaction to a 10 mL centrifuge tube with 4 mL of ethyl acetate as the solvent, and detect and quantify with a gas chromatograph (GC) and detect qualitatively with a gas chromatograph-mass spectrometer (GC-MS).

[0061] Example 4:

[0062] The co-catalyst TBAB (0.0162 g) and the catalyst KL-CPA (0.02 g) were added to a high-pressure reaction kettle, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 80 °C and 0.1 MPa for 12 h to obtain a mixture containing the propylene carbonate product. According to gas chromatography analysis, the conversion rate of propylene oxide was 98%, and the product selectivity was 99%.

[0063] Example 5:

[0064] The co-catalyst TBAB (0.0162 g) and the catalyst KL-CPA (0.02 g) were added to a high-pressure reaction kettle, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 40 °C and 0.1 MPa for 12 h to obtain a mixture containing the propylene carbonate product. According to gas chromatography analysis, the conversion rate of propylene oxide was 92%, and the product selectivity was 99%.

[0065] Example 6:

[0066] The co-catalyst TBAB (0.0162 g) and the catalyst KL-CPA (0.02 g) were added to a high-pressure reaction kettle, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 25 °C and 0.1 MPa for 12 h to obtain a mixture containing the propylene carbonate product. According to gas chromatography analysis, the conversion rate of propylene oxide was 87%, and the product selectivity was 97%.

[0067] Example 7:

[0068] The co-catalyst TBAB (0.0162 g) and the catalyst KL (0.02 g) were added to a high-pressure reaction kettle, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 25 °C and 0.1 MPa for 12 h to obtain a mixture containing the propylene carbonate product. According to gas chromatography analysis, the conversion rate of propylene oxide was 40%, and the product selectivity was 95%.

[0069] Example 8:

[0070] The co-catalyst TBAB (0.0162 g) and the catalyst CPA (0.02 g) were added to a high-pressure reaction kettle, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 25 °C and 0.1 MPa for 12 h to obtain a mixture containing the propylene carbonate product. According to gas chromatography analysis, the conversion rate of propylene oxide was 63%, and the product selectivity was 97%.

[0071] Example 9:

[0072] Catalyst KL-CPA-1 (0.02 g) was added to a high-pressure reaction kettle, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 25 °C and 0.1 MPa for 12 h to obtain a mixture containing propylene carbonate product. Gas chromatographic analysis showed that the conversion of propylene oxide was 45%, and the product selectivity was 95%.

[0073] Example 10:

[0074] Catalyst KL-CPA-2 (0.02 g) was added to a high-pressure reaction kettle, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 25 °C and 0.1 MPa for 12 h to obtain a mixture containing propylene carbonate product. Gas chromatographic analysis showed that the conversion of propylene oxide was 42%, and the product selectivity was 94%.

[0075] Example 11:

[0076] Catalyst KL-CPA (0.02 g) was added to a high-pressure reaction kettle, and then 0.14 mL of epichlorohydrin was added. The reaction was stirred at 50 °C and 0.1 MPa for 12 h to obtain a mixture containing cyclic carbonate product. Gas chromatographic analysis showed that the conversion of epichlorohydrin was 91%, and the product selectivity was 99%.

[0077] Example 12:

[0078] Catalyst KL-CPA (0.02 g) was added to a high-pressure reaction kettle, and then 0.14 mL of 1,2-epoxyhexane was added. The reaction was stirred at 50 °C and 0.1 MPa for 12 h to obtain a mixture containing cyclic carbonate product. Gas chromatographic analysis showed that the conversion of epichlorohydrin was 85%, and the product selectivity was 98%.

[0079] Example 13:

[0080] Catalyst KL-CPA (0.02 g) was added to a high-pressure reaction kettle, and then 0.14 mL of epoxystyrene was added. The reaction was stirred at 60 °C and 0.1 MPa for 12 h to obtain a mixture containing cyclic carbonate product. Gas chromatographic analysis showed that the conversion of epichlorohydrin was 89%, and the product selectivity was 99%.

[0081] Example 14:

[0082] The co-catalyst TBAB (0.0162 g) and the catalyst KL-CPA (0.02 g) were added to the autoclave, and then 0.14 mL of epoxycyclohexane was added. The reaction was stirred at 70 °C and 0.1 MPa for 12 h to obtain a mixture containing the cyclic carbonate product. The conversion of epoxycyclohexane was 97% and the product selectivity was 99% by gas chromatography analysis.

[0083] Example 15:

[0084] After the reaction in Example 6 was completed, the catalyst in the autoclave was removed, washed with ethyl acetate, and centrifuged three times. The co-catalyst TBAB (0.0162 g) and the recovered catalyst KL-CPA (0.02 g) were added to the autoclave, and then 0.14 mL of propylene oxide was added. The reaction was stirred at 25 °C and 0.1 MPa for 12 h to obtain a mixture containing the propylene carbonate product. The conversion of propylene oxide was 88% and the product selectivity was 97% by gas chromatography analysis. This cycle was repeated five times.

[0085] The conversion, selectivity, and yield of the cycloaddition reaction were calculated, and the results of the reaction are shown in the following table:

[0086] Table 1. Cycloaddition reaction of CO2 with propylene oxide at different temperatures

[0087] Catalyst Temperature / °C Time / h Conversion Selectivity KL-CPA 80 12 98 99 KL-CPA 40 12 92 99 KL-CPA 25 12 87 97

[0088] Table 2. Cycloaddition reaction of CO2 with propylene oxide using different catalysts

[0089] Catalyst Temperature / °C Time / h Conversion Selectivity KL 25 12 40 95 CPA 25 12 63 97 KL-CPA 25 12 87 97

[0090] Table 3. Cycloaddition reaction of CO2 with propylene oxide using different catalysts

[0091] Catalyst Temperature / °C Time / h Conversion Selectivity KL-CPA 25 12 87 97 KL-CPA-1 25 12 45 95 KL-CPA-2 25 12 42 94

[0092] Table 4. Cycloaddition reaction of CO2 with different epoxides using the catalyst KL-CPA

[0093] Epoxide Temperature / °C Time / h Conversion Selectivity Propylene oxide 25 12 87 97 Epichlorohydrin 50 12 91 99 1,2-Epoxyhexane 50 12 85 98 Epoxystyrene 60 12 89 99 Epoxycyclohexane 70 12 97 99

[0094] Table 5. Cycloaddition reaction of CO2 with epoxides using the catalyst KL-CPA

[0095] Cycle number Temperature / °C Time / h Conversion Selectivity 1 25 12 87 97 2 25 12 88 97 3 25 12 87 97 4 25 12 86 97 5 25 12 88 97

[0096] The above merely describes preferred embodiments of the present application, but is not intended to limit the present application to other forms, and any person skilled in the art can make changes or modifications to the above disclosed technical contents into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and improvement made to the above embodiments without departing from the technical solution of the present application and according to the technical essence of the present application still falls within the protection scope of the present application.

Claims

1. A method for preparing a biomass-based catalyst KL-CPA from lignin as a raw material, characterized by, The preparation method comprises the following steps: (1) dissolving free radical monomers and chain transfer agent in deionized water, adding initiator and synthesizing under high temperature in nitrogen atmosphere; (2) extracting the product with anhydrous ethanol after cooling the mixed solution of step (1), and freeze-drying to obtain CPA; (3) dissolving the CPA obtained in step (2) and lignin in deionized water and reacting under high temperature, extracting the product with anhydrous ethanol after cooling, and then purifying by dialysis, and freeze-drying to obtain the biomass-based catalyst KL-CPA.

2. The process for the preparation of biomass-based catalyst KL-CPA as claimed in claim 1, wherein, The free radical monomers are acrylamide and methacryloyloxyethyl trimethyl ammonium chloride, and the molar ratio is 3:

1.

3. The process for the preparation of biomass based catalyst KL-CPA as claimed in claim 1, wherein, The chain transfer agent is 4-chloromethyl styrene, and the initiator is ammonium persulfate.

4. The process for the preparation of biomass based catalyst KL-CPA as claimed in claim 1, wherein, The lignin is sodium lignosulfonate, and the mass ratio of sodium lignosulfonate to CPA is 1:1, 1:2 and 2:1 respectively, and the catalysts are named as KL-CPA, KL-CPA-1 and KL-CPA-2 respectively.

5. The process for the preparation of biomass based catalyst KL-CPA as claimed in claim 1, wherein, In step (1), AM, DMC and CS are dissolved in deionized water, nitrogen is continuously blown into the reaction solution, then APS is added, and the reaction solution is continuously blown with nitrogen, and the reaction is carried out in an oil bath.

6. The process for the preparation of biomass based catalyst KL-CPA as claimed in claim 1, wherein, In step (2), the product is extracted with anhydrous ethanol and then freeze-dried.

7. The process for the preparation of biomass based catalyst KL-CPA as claimed in claim 1, wherein, In step (3), KL and CPA in different proportions are dissolved in deionized water and reacted in an oil bath, the product is extracted with anhydrous ethanol, dialyzed with a dialysis bag, and then freeze-dried.

8. A biomass-based catalyst KL-CPA prepared from lignin, characterized in that, The biomass-based catalyst KL-CPA prepared by the preparation method of any one of claims 1-7 is obtained.

9. Use of a biomass-based catalyst KL-CPA according to claim 8, characterized in that, The biomass-based catalyst KL-CPA prepared by using lignin as raw material is used for CO2 cycloaddition reaction with different epoxides as substrates.

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