Sustainable biofuel separation and purification method based on CO2 capture and salt cyclic regeneration

Abstract

The invention discloses a sustainable biofuel separation and purification method based on CO2 capture and salt cyclic regeneration, which comprises the following steps: 1) treating a fermentation broth, placing the fermentation broth in a headspace bottle, adding salt, sealing, fully shaking, and standing until a salting-out phase is balanced; 2) collecting the water phase in the headspace bottle in the step 1), placing the water phase in a double-port reaction bottle, introducing the fermentation waste gas into the water phase solution in the double-port reaction bottle for reaction until a reaction endpoint is reached, recovering the reacted salt, and reusing the salt after post-treatment; according to the technical scheme provided by the invention, potassium carbonate (K2CO3) is used as a bifunctional agent, and efficient separation and resource circulation of the biological butanol fermentation liquor are realized through a salt precipitation separation-carbon capture-salt regeneration closed-loop method; the method comprises the following steps: reacting CO2 generated by fermentation of biological butanol with a K2CO3 enriched water phase after salting-out separation to generate potassium bicarbonate (KHCO3), and recovering K2CO3 through simple thermal decomposition to form a closed-loop salt cycle; according to the method, the n-butyl alcohol recovery rate gt can be realized under optimized conditions; the method has the advantages that the reaction efficiency and the CO2 absorption and utilization rate are balanced, the CO2 utilization rate can be up to 88%, the salt recovery rate is 84%, and the consumption of chemicals is reduced by more than or equal to 80%; according to the method, salt recovery and carbon emission reduction are integrated, and an economical, efficient and environment-friendly circular economy model is provided for separation and purification of biofuel.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical separation, and relates to a method for separating and purifying biofuels, specifically to a method for separating and purifying biofuels based on CO2 capture and salt cycle regeneration. Background Art

[0002] Biofuels are often regarded as ideal substitutes for fossil fuels. n-butanol, acetone, and ethanol are good organic solvents and important chemical raw materials. Due to the properties of bio-n-butanol such as high energy density, low vapor pressure, and good combustion stability, fermented n-butanol is more meaningful. Bio-n-butanol can be obtained by the acetone / n-butanol / ethanol (referred to as ABE) fermentation of biomass. The generation of fermented exhaust gas CO2 in the production process of biofuels will restrict its sustainable development. Therefore, we can use K2CO3 as a bifunctional agent, which can not only separate and purify the acetone-butanol-ethanol (ABE) solution but also capture CO2 from biofuel fermentation.

[0003] The industrial production of butanol can adopt the microbial fermentation method or the chemical synthesis method. The chemical synthesis method usually uses petrochemical products as raw materials, which will produce a large amount of waste gas, waste water, and waste residue, causing environmental pollution (Biotechnol. J. 2011, 6, 1348–1357). Therefore, people's attention is still focused on the more environmentally friendly fermentation process (Fermentation 2023, 9, 847.). Corn fermentation can produce acetone, n-butanol, and ethanol, which is called ABE fermentation. The target product is usually mixed with other components in the fermentation broth, and separation operations are required to extract and purify the required target product. The traditional distillation method is the main method for recovering butanol from the fermentation broth. However, due to the low butanol concentration and the high latent heat of vaporization of water, the energy consumption is very high. The energy required to remove butanol in the classical distillation process is 220% of the energy content of butanol itself (FEMS Microbiol. Lett. 2016, 363, 1–5). The recovery rate of the adsorption method is low (less than 85%) and the enrichment ability is weak (Biotechnol. Prog. 2012, 28, 962–972), because the application of commercial adsorbents in the integrated acetone-butanol-ethanol (ABE) fermentation process is limited. Therefore, although distillation and adsorption are traditional ABE separation technologies, they each have obvious disadvantages. Salting-out, as an economic, simple, and effective separation technology, is widely used in the purification of bioalcohols. K2CO3 is a non-toxic, recyclable high ionic strength salt with a strong ability to promote phase separation. Therefore, K2CO3 is selected as the salting-out agent.

[0004] ABE fermentation is a biochemical process that generates a large amount of carbon dioxide. For carbon dioxide, common carbon capture methods include chemical absorption, membrane separation, and physical adsorption. Chemical absorption using alkaline solutions such as carbonates as absorbents has attracted increasing attention from researchers due to its low cost, easy regeneration, low toxicity, and good stability. Summary of the Invention

[0005] In view of the problems of large consumption of salting-out agent, CO2 emissions, and subsequent treatment of salts in the processes of bio-butanol fermentation and salting-out extraction, the present invention proposes a recycling method to achieve sustainable separation and purification of biofuels by combining CO2 capture and salt regeneration cycle.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, comprising the following steps:

[0008] 1) Treat the fermentation broth and place it in a headspace bottle, then add salt, seal and shake well, and let it stand until the salting-out phase equilibrium is reached;

[0009] 2) Collect the aqueous phase in the headspace bottle of step 1) and place it in a two-neck reaction flask. Pass the fermentation waste gas into the aqueous phase of the two-neck reaction flask for reaction until the reaction end point is reached. Recover the salt in the aqueous phase after the reaction, and reuse it after post-treatment.

[0010] Further, in the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, the salt is one or any combination of K2CO3 or Na2CO3.

[0011] Further, in the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, the fermentation broth comprises ethanol, acetone, and n-butanol with a mass ratio of 1:3:6.

[0012] Further, in the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, the treatment of the fermentation broth is to concentrate the ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol.

[0013] Further, in the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, using the water described in claim 4 as the solvent, the salt concentration is 50 - 550 g·kg -1 .

[0014] Further, for the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, the reaction end-point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%.

[0015] Further, for the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, the flow rate of the fermented exhaust gas when introduced is 20 - 60 mL / min.

[0016] Further, for the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, filter out the salt precipitated in the aqueous solution after the reaction, and vacuum dry it until the white solid KHCO3 is completely precipitated; then heat to fully decompose KHCO3, take out the product after cooling, and cool it to room temperature to obtain white powdery K2CO3 for recycling.

[0017] Further, for the above-mentioned sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, it successively includes the following steps:

[0018] Step 1: Compress the fermented gas into a steel cylinder;

[0019] Step 2: After degassing the fermentation broth, dilute it and place it in a headspace bottle and mix evenly.

[0020] Step 3: Add salt to the headspace bottle in Step 2 so that the salt concentration is 50 - 550 g·kg -1 , seal the headspace bottle and shake it well, then let it stand to reach salting-out phase equilibrium;

[0021] Step 4: After reaching salting-out phase equilibrium, take out the organic phase in the headspace bottle and perform gas chromatography analysis;

[0022] Step 5: Collect the aqueous phase in the headspace bottle in Step 3, place it in a two-neck reaction flask and stir. After adjusting the fermented exhaust gas in Step 1 through a pressure reducing valve, control the gas flow rate to be 20 - 60 mL / min with a glass rotameter and introduce the fermented gas into the aqueous solution in the two-neck reaction flask for reaction. Pause the gas introduction every 5 minutes, weigh the total mass of the reaction system, record the data until the reaction end-point is reached, and record the total time to reach the reaction end-point;

[0023] Step 6: Filter out the salt precipitated in the aqueous solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature to 60 °C, the vacuum degree to -0.08 MPa, and dry for 6 - 8 hours until the white solid is completely precipitated.

[0024] Step 7: Transfer the dried white solid obtained in Step 6 to a ceramic crucible, spread it evenly, place it in a muffle furnace, and program the temperature to rise to 250 °C at a rate of 5 °C / min, and keep it at a constant temperature for 2 hours to fully decompose KHCO3; turn off the muffle furnace, take out the product after the temperature drops below 50 °C, cool it to room temperature to obtain powdery white K2CO3, and add it to Step 3 to replace fresh K2CO3 for reuse.

[0025] Due to the adoption of the above technical solutions, the present invention has the following advantages:

[0026] (1) Compared with the high energy consumption of traditional distillation, salting-out separation is an economical, simple and effective separation technology. In the present invention, the separation and purification of organic components (acetone, n-butanol, ethanol) in the bio-butanol fermentation broth are realized through salting-out extraction. The salting-out effect is based on the increase in ionic strength (high-concentration K2CO3 solution) to reduce the solubility of organic solvents and promote the rapid stratification of the organic phase and the aqueous phase. Moreover, the selected salt is non-toxic, has excellent water solubility, and does not react with the target products (acetone, n-butanol, ethanol), ensuring the stability of the separation system.

[0027] (2) The present invention reduces the net CO2 emissions and the consumption of the salting-out extractant. The salting-out extractant also acts as a chemical absorbent to capture the CO2 generated by fermentation, and itself precipitates in the form of KHCO3 for reuse. This not only reduces the carbon capture cost (compared with the traditional amine method for CO2 capture technology), realizes the carbon closed-loop, but also avoids the discharge of a large amount of saline wastewater, which has important economic and environmental significance.

[0028] (3) The precipitated KHCO3 in the present invention can be simply thermally decomposed into K2CO3 subsequently and can be reused in the salting-out extraction process to realize the closed-loop use of salt and reduce the chemical consumption by ≥80%.

[0029] (4) By regulating the concentration of the salting-out agent (10 - 600 g·kg -1 ), the stirring rate (50 - 1500 r / min) and the CO2 flow rate (10 - 80 mL / min), the present invention can adapt to fermentation broths with different mass concentrations (30% - 80%), and has high process compatibility.

[0030] (5) The CO2 absorption reaction in the present invention is carried out at room temperature without complex temperature control equipment. This sustainable separation and purification method can also be applied to other various biofuel systems such as lignocellulose hydrolysate and algal fermentation broth, promoting large-scale application. Description of the Drawings

[0031] Figure 1 is the gas chromatogram of the organic phase in the headspace bottle of Example 1;

[0032] Figure 2It is the gas chromatogram of the organic phase in the headspace bottle of Example 2;

[0033] Figure 3 It is the gas chromatogram of the organic phase in the headspace bottle of Example 3;

[0034] Figure 4 It is the gas chromatogram of the organic phase in the headspace bottle of Example 4;

[0035] Figure 5 It is the gas chromatogram of the organic phase in the headspace bottle of Example 5;

[0036] Figure 6 It is the gas chromatogram of the organic phase in the headspace bottle of Example 6;

[0037] Figure 7 It is the gas chromatogram of the organic phase in the headspace bottle of Example 7;

[0038] Figure 8 It is the gas chromatogram of the organic phase in the headspace bottle of Example 8;

[0039] Figure 9 It is the gas chromatogram of the organic phase in the headspace bottle of Example 9;

[0040] Figure 10 It is the gas chromatogram of the organic phase in the headspace bottles of Examples 10 - 12;

[0041] Figure 11 It is the gas chromatogram of the organic phase in the headspace bottle of Example 13;

[0042] Figure 12 They are the recovery rates of acetone, n - butanol, and ethanol at different initial salt concentrations.

[0043] Figure 13 They are the recovery rate of the salt reaching complete reaction, the time deviation rate, and the CO₂ absorption utilization rate at different gas flow rates. Detailed implementation manners

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0045] It should be noted that during the experimental stage of this application, the simulated industrial fermentation waste gas used is prepared according to the components of industrial fermentation waste gas in "Fermentation Method for Acetone and Butanol Production Technology". The specific components are: 62% (V%) carbon dioxide and 38% hydrogen (V%);

[0046] Example 1

[0047] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h for 1 h, and then compress them into an 8 L steel cylinder to obtain the simulated industrial fermentation waste gas.

[0048] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0049] Step 3: Add 0.2632 g of K2CO3 to the 20 mL headspace vial in Step 2 to make the salt concentration 50 g·kg -1 , seal the headspace vial and shake it well for 30 min, then let it stand at 20 °C for 24 h.

[0050] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis. Refer to Figure 1 .

[0051] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 77.86% water, 3.01% ethanol, 7.63% acetone, 4.62% n-butanol, and 6.88% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase solution in the two-neck reaction flask for reaction. Pause the gas injection every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (the determination standard for the reaction end point: the change rate of the three consecutive measurement values of Δm CO2 <1%), and record the total time to reach the reaction end point.

[0052] Step 6: Let the solution that reaches the reaction end point in Step 5 stand for 6 h, then take 5 mL of the upper clear liquid into a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt (specifically referring to the amount of substance of K + ) in the reaction solution by using the external standard method with a conductivity meter.

[0053] Step 7: Filter out the salt precipitated in the aqueous solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0054] Step 8: Transfer the dried white solid in Step 7 to a ceramic crucible, evenly spread it out, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min, and keep it at a constant temperature for 2 hours to fully decompose KHCO₃.

[0055] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K₂CO₃.

[0056] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K₂CO₃ to verify the purity. Grind the K₂CO₃ with qualified purity through a 100-mesh sieve, and directly replace the fresh K₂CO₃ according to the salt content required in the salting-out extraction process in Step 3.

[0057] Example 2

[0058] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h. After mixing for 1 h, compress it into an 8 L steel cylinder.

[0059] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with each component content of: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0060] Step 3: Add 0.5556 g of K₂CO₃ to the 20 mL headspace vial in Step 2 to make the salt concentration 100 g·kg -1 , seal the headspace vial and shake it well for 30 min, and let it stand at 20 °C for 24 h.

[0061] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 2 .

[0062] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 77.05% water, 2.51% ethanol, 4.98% acetone, 2.27% n-butanol, and 13.18% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas introduction every 5 minutes, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0063] Step 6: After allowing the solution that has reached the reaction end point in Step 5 to stand for 6 h, take 5 mL of the supernatant and transfer it to a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the reacted solution (specifically referring to the amount of substance of K + ) by an external standard method using a conductivity meter.

[0064] Step 7: Filter out the precipitated salt from the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0065] Step 8: Transfer the dried white solid in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0066] Step 9: Turn off the muffle furnace. After the temperature drops below 50 °C, take out the product and cool it to room temperature to obtain white powdery K2CO3.

[0067] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0068] Example 3

[0069] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h for 1 h, and then compress it into an 8 L steel cylinder.

[0070] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with each component content of: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0071] Step 3: Add 0.8824 g of K2CO3 to the 20 mL headspace vial in Step 2 to make the salt concentration 150 g·kg -1 , seal the headspace vial and shake it well for 30 min, then let it stand at 20 °C for 24 h.

[0072] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 3 .

[0073] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 76.63% water, 1.22% ethanol, 2.28% acetone, 0.66% n-butanol, and 19.22% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate controlled at 60 mL / min by a glass rotor flowmeter into the aqueous phase of the two-neck reaction flask. Pause the gas introduction every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0074] Step 6: Let the solution that reaches the reaction end point in Step 5 stand for 6 h, then take 5 mL of the upper clear liquid into a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the solution after the reaction (specifically referring to the amount of substance of K + ) by an external standard method using a conductivity meter.

[0075] Step 7: Filter out the salt precipitated in the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until white solid is completely precipitated.

[0076] Step 8: Transfer the dried white solid in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0077] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K2CO3.

[0078] Step ten, take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in step three.

[0079] Example 4

[0080] Step one, mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h. After mixing for 1 h, compress it into an 8-L steel cylinder.

[0081] Step two, concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20-mL headspace bottle.

[0082] Step three, add 1.25 g of K2CO3 to the 20-mL headspace bottle in step two to make the salt concentration 200 g·kg -1 , seal the headspace bottle and shake it well for 30 min, then let it stand at 20 °C for 24 h.

[0083] Step four, after reaching the salting-out phase equilibrium, use a 1-μL microsyringe to take out the organic phase in the headspace bottle, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 4 .

[0084] Step five, collect the aqueous phase in the headspace bottle in step three. The composition of the aqueous phase is 73.50% water, 0.73% ethanol, 1.08% acetone, 0.24% n-butanol, and 24.45% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the prepared simulated fermentation waste gas in step one through a pressure reducing valve, pass the fermentation gas with a gas flow rate controlled at 60 mL / min by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas injection every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (the reaction end point determination criterion: the change rate of the Δm CO2 of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0085] Step six, after letting the solution that reaches the reaction end point in step five stand for 6 h, take 5 mL of the upper clear liquid into a 50-mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the reaction solution (specifically referring to the amount of substance of K + ) in the solution by using an external standard method with a conductivity meter.

[0086] Step 7: Filter out the salt precipitated in the aqueous solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0087] Step 8: Transfer the white solid dried in Step 7 to a ceramic crucible, spread it evenly, place it in a muffle furnace, and program the temperature to rise to 250 °C at a rate of 5 °C / min, and keep it at a constant temperature for 2 hours to fully decompose KHCO₃.

[0088] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K₂CO₃.

[0089] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K₂CO₃ to verify the purity. Grind the K₂CO₃ with qualified purity through a 100-mesh sieve and directly replace the fresh K₂CO₃ according to the salt content required in the salting-out extraction process in Step 3.

[0090] Example 5

[0091] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h. After mixing for 1 h, compress it into an 8-L steel cylinder.

[0092] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20-mL headspace vial.

[0093] Step 3: Add 1.667 g of K₂CO₃ to the 20-mL headspace vial in Step 2 to make the salt concentration 250 g·kg -1 , seal the headspace vial and shake it well for 30 min, and let it stand at 20 °C for 24 h.

[0094] Step 4: After reaching the salting-out phase equilibrium, use a 1-μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 5 .

[0095] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 69.68% water, 0.45% ethanol, 0.60% acetone, 0.12% n-butanol, and 29.16% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas introduction every 5 minutes, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0096] Step 6: After standing the solution that reaches the reaction end point in Step 5 for 6 h, take 5 mL of the supernatant and transfer it to a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the solution after the reaction (specifically referring to the amount of substance of K + ) by an external standard method using a conductivity meter.

[0097] Step 7: Filter out the salt precipitated in the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0098] Step 8: Transfer the white solid dried in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it constant for 2 hours to fully decompose KHCO3.

[0099] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdered K2CO3.

[0100] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0101] Example 6

[0102] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h for 1 h, and then compress them into an 8 L steel cylinder.

[0103] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0104] Step 3: Add 2.1429 g of K2CO3 to the 20 mL headspace vial in Step 2 to make the salt concentration 300 g·kg -1 , seal the headspace vial and shake it well for 30 min, then let it stand at 20 °C for 24 h.

[0105] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, referring to Figure 6 .

[0106] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 65.70% water, 0.25% ethanol, 0.30% acetone, 0.04% n-butanol, and 33.71% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas introduction every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (the reaction end point determination criterion: the change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point. CO2

[0107] Step 6: Let the solution that reaches the reaction end point in Step 5 stand for 6 h, then take 5 mL of the upper clear liquid into a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the post-reaction solution (specifically referring to the amount of substance of K + ) by using an external standard method with a conductivity meter.

[0108] Step 7: Filter out the salt precipitated in the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C and the vacuum degree at -0.08 MPa, and dry it for 6 - 8 hours until white solid is completely precipitated.

[0109] Step 8: Transfer the dried white solid in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0110] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K2CO3.

[0111] Step ten: Take a small amount of the product and dissolve it in deionized water. Measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in step three.

[0112] Example 7

[0113] Step one: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h. After mixing for 1 h, compress them into an 8-L steel cylinder.

[0114] Step two: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20-mL headspace vial.

[0115] Step three: Add 2.6923 g of K2CO3 to the 20-mL headspace vial in step two to make the salt concentration 350 g·kg -1 , seal the headspace vial and shake it well for 30 min, then let it stand at 20 °C for 24 h.

[0116] Step four: After reaching the salting-out phase equilibrium, use a 1-μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 7 .

[0117] Step five: Collect the aqueous phase in the headspace vial in step three. The composition of the aqueous phase is 61.67% water, 0.15% ethanol, 0.14% acetone, 0.01% n-butanol, and 38.03% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in step one through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas injection every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (the reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0118] Step six: After letting the solution reach the reaction end point in step five stand for 6 h, take 5 mL of the upper clear liquid into a 50-mL volumetric flask, add deionized water to make up the volume, and use an external standard method with a conductivity meter to quantitatively analyze the remaining salt (specifically referring to the amount of substance of K + ) in the solution after the reaction.

[0119] Step 7: Filter out the salt precipitated in the aqueous solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0120] Step 8: Transfer the dried white solid in Step 7 to a ceramic crucible, spread it evenly, place it in a muffle furnace, and program the temperature to rise to 250 °C at a rate of 5 °C / min, and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0121] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K2CO3.

[0122] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0123] Example 8

[0124] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h. After mixing for 1 h, compress them into an 8 L steel cylinder.

[0125] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0126] Step 3: Add 3.3333 g of K2CO3 to the 20 mL headspace vial in Step 2 to make the salt concentration 400 g·kg -1 , seal the headspace vial and shake it well for 30 min, and let it stand at 20 °C for 24 h.

[0127] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 8 .

[0128] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 57.35% water, 0.08% ethanol, 0.07% acetone, and 42.50% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas introduction every 5 minutes, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0129] Step 6: After allowing the solution that reached the reaction end point in Step 5 to stand for 6 h, take 5 mL of the supernatant and transfer it to a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the solution after the reaction (specifically referring to the amount of substance of K + by using an external standard method with a conductivity meter).

[0130] Step 7: Filter out the salt precipitated in the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0131] Step 8: Transfer the dried white solid in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0132] Step 9: Turn off the muffle furnace. After the temperature drops below 50 °C, take out the product and cool it to room temperature to obtain white powdery K2CO3.

[0133] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0134] Example 9

[0135] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h for 1 h, and then compress it into an 8 L steel cylinder.

[0136] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0137] Step 3: Add 4.0909 g of K2CO3 to the 20 mL headspace vial in Step 2 to make the salt concentration 450 g·kg -1 , seal the headspace vial and shake it well for 30 min, then let it stand at 20 °C for 24 h.

[0138] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 9 .

[0139] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 52.90% water, 0.05% ethanol, 0.04% acetone, and 47.01% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min into the aqueous phase of the two-neck reaction flask through a glass rotor flowmeter. Pause the gas injection every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0140] Step 6: After allowing the solution that reached the reaction end point in Step 5 to stand for 6 h, take 5 mL of the upper clear liquid and transfer it to a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the post-reaction solution (specifically referring to the amount of substance of K + ) by an external standard method using a conductivity meter.

[0141] Step 7: Filter out the salt precipitated in the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature to 60 °C, the vacuum degree to -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0142] Step 8: Transfer the white solid dried in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0143] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K2CO3.

[0144] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0145] Example 10

[0146] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h. After mixing for 1 h, compress them into an 8-L steel cylinder.

[0147] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the following component contents: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20-mL headspace vial.

[0148] Step 3: Add 5 g of K2CO3 to the 20-mL headspace vial in Step 2 to make the salt concentration 500 g·kg -1 , seal the headspace vial and shake it well for 30 min, then let it stand at 20 °C for 24 h.

[0149] Step 4: After reaching the salting-out phase equilibrium, use a 1-μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis. Refer to Figure 10 .

[0150] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 48.45% water, 0.04% ethanol, 0.02% acetone, and 51.49% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the pressure-reducing valve for the simulated fermentation waste gas prepared in Step 1, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas passing every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (the reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0151] Step 6: Let the solution that reaches the reaction end point in Step 5 stand for 6 h, then take 5 mL of the supernatant to a 50-mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt (specifically referring to the amount of substance of K + ) in the post-reaction solution by using an external standard method with a conductivity meter.

[0152] Step 7: Filter out the salt precipitated in the aqueous solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0153] Step 8: Transfer the dried white solid in Step 7 to a ceramic crucible, spread it evenly, place it in a muffle furnace, and program the temperature to rise to 250 °C at a rate of 5 °C / min, and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0154] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K2CO3.

[0155] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0156] Example 11

[0157] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h. After mixing for 1 h, compress it into an 8 L steel cylinder.

[0158] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0159] Step 3: Add 5 g of K2CO3 to the 20 mL headspace vial in Step 2 to make the salt concentration 500 g·kg -1 , seal the headspace vial and shake it well for 30 min, and let it stand at 20 °C for 24 h.

[0160] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis, refer to Figure 10 .

[0161] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 48.45% water, 0.04% ethanol, 0.02% acetone, and 51.49% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 40 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas introduction every 5 minutes, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0162] Step 6: After allowing the solution that reaches the reaction end point in Step 5 to stand for 6 h, take 5 mL of the upper clear liquid and transfer it to a 50 mL volumetric flask. Add deionized water to make up the volume, and quantitatively analyze the remaining salt in the solution after the reaction (specifically referring to the amount of substance of K + ) by an external standard method using a conductivity meter.

[0163] Step 7: Filter out the salt precipitated in the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry for 6 - 8 hours until a white solid is completely precipitated.

[0164] Step 8: Transfer the white solid dried in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0165] Step 9: Turn off the muffle furnace. After the temperature drops below 50 °C, take out the product and cool it to room temperature to obtain white powdery K2CO3.

[0166] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0167] Example 12

[0168] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a gas flow rate of 38 L / h for 1 h and then compress it into an 8 L steel cylinder.

[0169] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0170] Step 3: Add 5 g of K2CO3 to the 20 mL headspace vial in Step 2 to make 500 g·kg -1 , seal the headspace vial, shake it well for 30 min, and let it stand at 20 °C for 24 h.

[0171] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis. Refer to Figure 10 .

[0172] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 48.45% water, 0.04% ethanol, 0.02% acetone, and 51.49% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer at 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 20 mL / min into the aqueous phase of the two-neck reaction flask through a glass rotameter. Pause the gas flow every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (reaction end point determination criterion: Δm CO2 The change rate of three consecutive measurement values < 1%), and record the total time to reach the reaction end point.

[0173] Step 6: After allowing the solution that reached the reaction end point in Step 5 to stand for 6 h, take 5 mL of the upper clear liquid and transfer it to a 50 mL volumetric flask, add deionized water to make up the volume, and use an external standard method with a conductivity meter to quantify the remaining salt in the solution after the reaction (specifically referring to the amount of substance of K + ).

[0174] Step 7: Filter out the salt precipitated from the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry it for 6 - 8 hours until a white solid is completely precipitated.

[0175] Step 8: Transfer the white solid dried in Step 7 to a ceramic crucible, spread it evenly, and place it in a muffle furnace. Program the temperature to rise to 250 °C at a rate of 5 °C / min and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0176] Step 9: Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K2CO3.

[0177] Step 10: Take a small amount of the product and dissolve it in deionized water, measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0178] Example 13

[0179] Step 1: Mix carbon dioxide with a flow rate of 62 L / h and hydrogen with a flow rate of 38 L / h for 1 h, and then compress the mixture into an 8 L steel cylinder.

[0180] Step 2: Concentrate the industrial ABE fermentation broth to an ABE fermentation broth concentrate with the following component contents: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol. Take 10 g of the concentrated ABE fermentation broth and place it in a 20 mL headspace vial.

[0181] Step 3: Add K2CO3 with a salt concentration of 550 g·kg -1 to the 20 mL headspace vial in Step 2. Seal the headspace vial and shake it well for �0 min, then let it stand at 20 °C for 24 h.

[0182] Step 4: After reaching the salting-out phase equilibrium, use a 1 μL microsyringe to take out the organic phase in the headspace vial, inject it into the injector, and then perform gas chromatography analysis. Refer to Figure 11 .

[0183] Step 5: Collect the aqueous phase in the headspace vial in Step 3. The composition of the aqueous phase is 43.75% water, 0.02% ethanol, 0.01% acetone, and 56.22% K2CO3. Each time, take 41.23 g of the aqueous phase and place it in a two-neck reaction flask. Control the stirring rate of the magnetic stirrer to be 1100 r / min. After adjusting the simulated fermentation waste gas prepared in Step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate of 60 mL / min controlled by a glass rotameter into the aqueous phase of the two-neck reaction flask. Pause the gas injection every 5 min, weigh the total mass of the reaction system, and record the data until the reaction end point is reached (the reaction end point determination criterion: the change rate of the three consecutive measurement values of Δm CO2 <1%). Record the total time to reach the reaction end point.

[0184] Step 6: Let the solution that reaches the reaction end point in Step 5 stand for 6 h, then take 5 mL of the upper clear liquid into a 50 mL volumetric flask, add deionized water to make up the volume, and quantitatively analyze the remaining salt in the reaction solution (specifically referring to the amount of substance of K + ) in the reaction solution by an external standard method using a conductivity meter.

[0185] Step 7: Filter out the salt precipitated in the aqueous phase solution after the reaction in Step 5, transfer it to a vacuum drying oven, set the temperature to 60 °C, the vacuum degree to -0.08 MPa, and dry it for 6 - 8 hours until a white solid is completely precipitated.

[0186] Step 8: Transfer the dried white solid from Step 7 to a ceramic crucible. After spreading it evenly, place it in a muffle furnace and program the temperature to rise at a rate of 5 °C / min to 250 °C, and keep it at a constant temperature for 2 hours to fully decompose KHCO3.

[0187] Step 9: Turn off the muffle furnace. After the temperature drops below 50 °C, take out the product and cool it to room temperature to obtain white powdery K2CO3.

[0188] Step 10: Take a small amount of the product and dissolve it in deionized water. Measure the conductivity and compare it with the standard curve of pure K2CO3 to verify the purity. Grind the K2CO3 with qualified purity through a 100-mesh sieve and directly replace the fresh K2CO3 according to the salt content required in the salting-out extraction process in Step 3.

[0189] The concentration of the industrial ABE fermentation broth in the above-mentioned examples is concentrated by conventional technical means in the art, such as rectification.

[0190] The contents of water, ethanol, acetone, and n-butanol in each of the above examples were all obtained by testing with a gas chromatograph, and the quantitative method was the corrected normalization method. The water content in the organic phase after salting-out extraction of the crude alcohol was measured in each example, and the results showed that the water content in the total solvent was greatly reduced, proving the effective salting-out ability of K2CO3.

[0191] By recording the total time required to reach the reaction end point in each example, the deviation rate between the actual reaction time and the theoretical reaction time and the CO2 absorption utilization rate can be calculated. The calculation methods are as follows:

[0192]

[0193] The salt recovery rates (the salt recovery rates throughout the text all refer to the recovery rate of K + ) in each of the above examples were all calculated by using an external standard method with a conductivity meter to quantify the remaining salt in the solution (specifically referring to the amount of substance of K + ). According to the law of conservation of mass, the salt recovery rate can be calculated. The calculation method is as follows:

[0194]

[0195] The results of the time deviation rate %, CO2 absorption utilization rate %, and recovery rate % in Examples 10 - 12 are shown in Table 1:

[0196] Table 1

[0197] Time deviation rate % <![CDATA[Absorption and utilization rate of CO2 %]]> Recovery rate % Example 10 1.1 99 84.18 Example 11 13.8 87 84.62 Example 12 41.9 71 84.64

[0198] The initial salt concentrations obtained in Examples 10 - 12 and the corresponding recovery rates of ethanol, acetone, and n-butanol are as Figure 12shown. The obtained gas flow rate, the corresponding salt recovery rate, the deviation rate of the actual reaction time from the theoretical reaction time, and the CO2 absorption utilization rate are as Figure 13 shown.

[0199] Since the solubility of KHCO3 is not zero, the salt recovery rate cannot reach 100% even if the reaction proceeds completely. The recovered KHCO3 in the present invention can be obtained by simple thermal decomposition to get K2CO3, which can be reused in the salting-out extraction process for reuse, realizing the regeneration cycle of the salt. The sustainable biofuel separation and purification method of the present invention can greatly reduce the resource consumption for the separation and recovery of ethanol, acetone and n-butanol.

Claims

1. A sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration, characterized in that, It includes the following steps: 1) After treating the fermentation broth, place it in a headspace vial, then add salt, seal it, shake well, and let it stand until the salting-out phase equilibrium is reached; 2) Collect the aqueous phase in the headspace vial of step 1), place it in a two-neck reaction flask, and pass the fermentation waste gas into the aqueous phase in the two-neck reaction flask for reaction until the reaction end point is reached. Recover the salt in the aqueous phase after the reaction, and reuse it after post-treatment.

2. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claim 1, wherein The salt is one of K2CO3 or Na2CO3 or any combination thereof.

3. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claim 1, wherein The fermentation broth is a mixed solution of ethanol, acetone, and n-butanol with a mass ratio of 1:3:

6.

4. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claim 1, wherein The treatment of the fermentation broth is to concentrate the ABE fermentation broth to an ABE fermentation broth concentrate with the content of each component being: 50 wt% water, 15 wt% acetone, 30 wt% n-butanol, and 5 wt% ethanol.

5. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claim 4, wherein Using water as the solvent as claimed in claim 4, the salt concentration is 50 - 550 g·kg -1 .

6. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claim 1, wherein The determination criterion for the reaction end point: Δm CO2 The change rate of the measured values for three consecutive times < 1%.

7. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claim 1, wherein The flow rate of the fermentation waste gas when passing through is 20 - 60 mL / min.

8. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claim 1, characterized in that, The post-treatment method of the salt after the reaction is: Filter out the salt precipitated in the aqueous phase solution after the reaction, and vacuum dry it until the white solid KHCO3 is completely precipitated; then heat it to fully decompose KHCO3, cool it down, take out the product, and cool it to room temperature to obtain white powdery K2CO3 for recycling.

9. The sustainable biofuel separation and purification method based on CO2 capture and salt cycle regeneration according to claims 1-8, characterized in that, It sequentially includes the following steps: Step 1, Compress the fermentation gas into a steel cylinder; Step 2, After degassing the fermentation broth, dilute it and then place it in a headspace vial and mix evenly. Step 3: Add salt to the headspace vial in Step 2 so that the salt concentration is 50 - 550 g·kg -1 , seal the headspace vial, shake it well, and then let it stand until the salting-out phase equilibrium is reached; Step 4, After reaching the salting-out phase equilibrium, take out the organic phase in the headspace vial for gas chromatography analysis; Step 5, Collect the aqueous phase in the headspace vial in step 3, place it in a two-neck reaction flask and stir. After adjusting the fermentation waste gas in step 1 through a pressure reducing valve, pass the fermentation gas with a gas flow rate controlled at 20 - 60 mL / min by a glass rotameter into the aqueous phase solution in the two-neck reaction flask for reaction. Pause the gas passing every 5 minutes, weigh the total mass of the reaction system, record the data until the reaction end point is reached, and record the total time to reach the reaction end point; Step 6: Filter out the salt precipitated in the aqueous phase solution after the reaction in step 5, transfer it to a vacuum drying oven, set the temperature at 60 °C, the vacuum degree at -0.08 MPa, and dry it for 6 - 8 hours until the white solid is completely precipitated; Step 7, Transfer the white solid dried in step 6 to a ceramic crucible, spread it evenly, place it in a muffle furnace, and program the temperature to rise to 250 °C at a rate of 5 °C / min, and keep it at a constant temperature for 2 hours to fully decompose KHCO3; Turn off the muffle furnace, take out the product after the temperature drops below 50 °C, and cool it to room temperature to obtain white powdery K2CO3, which is added to step 3 to replace fresh K2CO3 for recycling.

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