Process for high-valued aqueous phase synthesis of renewable biomass-based epoxy resin based on industrial pulping black liquor

Abstract

The invention relates to the technical field of efficient utilization of biomass, in particular to a process for high-valued aqueous phase synthesis of renewable biomass-based epoxy resin based on industrial pulping black liquor, which comprises the following steps: adjusting the pH value of the pulping black liquor with acid or alkali, adding epichlorohydrin, and heating to a certain temperature. And then adding an alkali solution to adjust the pH value, reacting for a certain time, cooling, centrifuging, taking a dark solution on the upper layer, adjusting the pH value to be neutral, and drying to obtain the biomass-based epoxy resin. The biomass-based epoxy resin is simple in synthesis process and low in energy consumption, industrial production is easy to realize, and the biomass-based epoxy resin has a wide market prospect.

Description

Technical Field

[0001] The invention relates to the technical field of efficient utilization of biomass, and more particularly to a process for synthesizing renewable biomass-based epoxy resin in an aqueous phase by high-value industrial pulping black liquor. Background Art

[0002] With the continuous increase in fossil energy consumption and people's growing concern about political and environmental pressures, people are increasingly seeking to use renewable resources and relatively clean energy to replace fossil energy. Pulping black liquor is a by-product of alkaline pulping in the pulp production process. The rich lignin in it is the only renewable aromatic compound in nature. Although the composition of pulping black liquor in factories varies greatly due to the cooking process and the wood used, the pollution caused is similar. The high alkalinity and high COD content of pulping black liquor cause serious harm to the environment and human health. The pollutants contained in black liquor account for more than 90% of the total pollution emissions of the papermaking industry, and have the characteristics of high concentration and difficulty in degradation. Its treatment has always been a major problem.

[0003] At present, domestic paper manufacturers basically use alkali recovery process to treat black liquor. Alkali recovery of pulping black liquor needs to go through three stages of evaporation, combustion and causticization to realize the resource utilization of black liquor. The evaporation section concentrates the dilute black liquor produced in the pulping process, and the concentrated black liquor is sent to the alkali furnace in the combustion section for combustion. The alkali furnace produces steam and green liquor by incinerating the black liquor from pulping to treat the black liquor that pollutes the environment. The steam can be used for cogeneration, and the green liquor enters the causticization section to recover alkali. However, the alkali recovery process does not effectively utilize the abundant lignin, and the processing energy consumption is high. The harmless treatment of pulping black liquor and its high-value utilization can not only effectively solve the bottleneck problem of overloaded alkali recovery furnace in pulping plants, but also provide a sustainable low-carbon solution for the energy conservation, emission reduction and consumption reduction goals of pulping enterprises; it is also the only way for the pulp and paper industry to achieve the "dual carbon" goal.

[0004] Epoxy resin is a polymer material that combines electrical insulation, chemical resistance, high temperature resistance, wear resistance and low shrinkage. It can be widely used in aerospace, integrated circuit boards, structural carbon fiber glue, electronic sealants, adhesives and other fields. Currently, more than 90% of epoxy resins are bisphenol A epoxy resins. Bisphenol A is a chemical extracted from fossil energy and is not renewable. Its large-scale use will aggravate the shortage of fossil energy and greenhouse gas emissions. Lignin has a similar structure to bisphenol A and has more phenolic hydroxyl groups. It is a promising green product to replace bisphenol A in synthesizing epoxy resins.

[0005] In recent years, researchers have conducted a lot of attempts and studies on the synthesis of epoxy resins from lignin with different separation methods and different biomass sources. Patent (CN116535672A) discloses a method for preparing a hyperbranched modified enzymatic lignin epoxy resin and its application. Patent (CN202210818308.1) discloses a lignin-based epoxy resin coating based on pulping black liquor and its preparation method. Patent (CN202011027011.0) discloses a waterproof lignin-based epoxy resin adhesive, especially a method for preparing an oleyl lignin-based epoxy resin. Patent (CN202211696384.6) discloses a black liquor lignin-based epoxy resin film composite material and its preparation method. Most of the above inventions use refined extracted lignin or partially replace bisphenol A with lignin to synthesize epoxy resins, rather than directly using undried pulping black liquor; and the environment for synthesizing epoxy resins is an organic phase, making it difficult to separate and recover the subsequent organic solvent. Summary of the invention

[0006] To solve the above problems, the present invention provides a process for synthesizing renewable biomass-based epoxy resin in aqueous phase based on the high-value industrial pulping black liquor. The high-pH and highly polluted pulping black liquor discharged in the papermaking industry can be directly synthesized into bio-based epoxy resin in high-value manner. There is no need to purify the black liquor, let alone alkali recovery. The whole process is green and environmentally friendly, with no wastewater discharge.

[0007] The present invention specifically adopts the following technical solutions:

[0008] A process for synthesizing renewable biomass-based epoxy resin based on high-value aqueous phase of industrial pulping black liquor comprises the following steps:

[0009] Take an appropriate amount of pulping black liquor, adjust the pH of the pulping black liquor to a certain range with acid or alkali, add an appropriate amount of epichlorohydrin, and heat to a certain temperature. Then, add an appropriate amount of alkaline solution to adjust the pH, react for a certain time, cool, centrifuge, take the upper dark solution, adjust the pH to neutral, and dry to obtain biomass-based epoxy resin.

[0010] Furthermore, the pH of the pulping black liquor is adjusted to 8-13 with acid or alkali.

[0011] Furthermore, the amount of epichlorohydrin added is 1.0-3.0 times the hydroxyl group contained in the lignin in the pulping black liquor, based on the molar ratio.

[0012] Furthermore, the reaction temperature is 50-100°C.

[0013] Furthermore, an alkaline solution is added to adjust the pH of the solution to 9-13.

[0014] Furthermore, the reaction time is 10-300 min.

[0015] Furthermore, after centrifugation, the pH of the obtained upper dark solution is adjusted to neutral, and dried to obtain the biomass-based epoxy resin.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention can directly convert the high-pH, highly polluting pulping black liquor discharged from the papermaking industry into a high-value bio-based epoxy resin without the need to purify the black liquor or recover alkali. The entire process is green and environmentally friendly with no wastewater discharge.

[0018] (2) The present invention uses renewable biomass to replace the toxic and non-renewable petroleum product bisphenol A, effectively reducing the consumption of fossil energy and contributing to the realization of the carbon neutrality goal.

[0019] (3) The present invention transforms highly polluting pulping black liquor into valuable materials to produce high-value bio-based epoxy resin. The process is simple, the energy consumption is low, and the production cycle is short, thus providing technical support for the large-scale production of bio-based epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The invention is a process for synthesizing renewable biomass-based epoxy resin from industrial pulping black liquor in aqueous phase with high value DETAILED DESCRIPTION

[0021] The present invention is described in detail below in conjunction with the accompanying drawings and specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0022] Example 1

[0023] Take 50mL of pulping black liquor and adjust the pH to 11, add 0.3mL of epichlorohydrin, and heat to 70℃ for 30min. Then, add 5mL of 4M sodium hydroxide solution to adjust the pH and react for 2h. Then cool and centrifuge to take the upper dark solution, adjust the pH to neutral, and dry at 60℃ to obtain biomass-based epoxy resin. The epoxy equivalent of the biomass-based epoxy resin measured by the hydrochloric acid-acetone method is 178g / mol, and the epoxy value is 0.5618mol / g.

[0024] Example 2

[0025] Take 50mL of pulping black liquor and adjust the pH to 12, add 0.5mL of epichlorohydrin, and heat to 60℃ for 30min. Then, add 5mL of 4M sodium hydroxide solution to adjust the pH and react for 2h. Then cool and centrifuge to take the upper dark solution, adjust the pH to neutral, and dry at 60℃ to obtain biomass-based epoxy resin. The epoxy equivalent of the biomass-based epoxy resin measured by the hydrochloric acid-acetone method is 292g / mol, and the epoxy value is 0.3425mol / g.

[0026] Example 3

[0027] Take 50mL of pulping black liquor and adjust the pH to 12, add 0.15mL of epichlorohydrin, and heat to 60℃ for 30min. Then, add 3mL of 4M sodium hydroxide solution to adjust the pH and react for 30min. Then cool and centrifuge to take the upper dark solution, adjust the pH to neutral, and dry at 60℃ to obtain biomass-based epoxy resin. The epoxy equivalent of the biomass-based epoxy resin measured by the hydrochloric acid-acetone method is 448g / mol, and the epoxy value is 0.2232mol / g.

[0028] Example 4

[0029] Take 50mL of pulping black liquor and adjust the pH to 12, add 0.2mL of epichlorohydrin, and heat to 70℃ for 30min. Then, add 3mL of 4M sodium hydroxide solution to adjust the pH and react for 3h. Then cool and centrifuge to take the upper dark solution, adjust the pH to neutral, and dry at 60℃ to obtain biomass-based epoxy resin. The epoxy equivalent of the biomass-based epoxy resin measured by the hydrochloric acid-acetone method is 258g / mol, and the epoxy value is 0.3876mol / g.

[0030] It can be seen from Table 1 that the epoxy equivalents of the biomass-based epoxy resins prepared in Examples 1-4 are all smaller than the solids after de-alkali drying of the pulping black liquor, and the epoxy values ​​are all greater than the solids after de-alkali drying of the pulping black liquor. This indicates that the content of epoxy groups in the molecule can be significantly increased after epoxidation of the pulping black liquor in the aqueous phase, thereby obtaining a bio-based epoxy resin.

[0031] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0032] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0033] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0034] Table 1. Epoxy equivalent and epoxy value of samples

[0035] sample Epoxide equivalent (g / mol) Epoxy value (mol / g) Example 1 178 0.5618 Example 2 292 0.3425 Example 3 448 0.2232 Example 4 258 0.3876 Solids after de-alkali drying of pulping black liquor 557 0.1795

[0036] *Epoxy equivalent refers to the mass (g) of biomass-based epoxy resin containing 1 mol equivalent of epoxy groups.

[0037] *Epoxy value refers to the equivalent number (mol) of epoxy groups in 100g of biomass-based epoxy resin.

Claims

1. A process for synthesizing renewable biomass-based epoxy resin based on high-value aqueous phase of industrial pulping black liquor, characterized in that: The following steps are involved: Take an appropriate amount of pulping black liquor, adjust the pH of the pulping black liquor to a certain range with acid or alkali, add an appropriate amount of epichlorohydrin, and heat to a certain temperature. Then, add an appropriate amount of alkaline solution to adjust the pH, react for a certain time, cool, centrifuge, take the upper dark solution, adjust the pH to neutral, and dry to obtain biomass-based epoxy resin.

2. The process for synthesizing renewable biomass-based epoxy resin from industrial pulping black liquor in aqueous phase according to claim 1, characterized in that: The pH of the pulping black liquor is adjusted to 8-13 with acid or alkali. The acid can be an inorganic acid such as hydrochloric acid, phosphoric acid, sulfuric acid, or an organic acid such as formic acid, acetic acid, or a combination of several of them.

3. The process for synthesizing renewable biomass-based epoxy resin from industrial pulping black liquor in aqueous phase according to claim 1, characterized in that: The amount of epichlorohydrin added is 1.0-3.0 times the hydroxyl group contained in the lignin in the pulping black liquor, based on the molar ratio.

4. The process for synthesizing renewable biomass-based epoxy resin from industrial pulping black liquor in aqueous phase according to claim 1, characterized in that: The reaction temperature is 50-100°C.

5. The process for synthesizing biomass-based epoxy resin from industrial pulping black liquor in aqueous phase according to claim 1, characterized in that: After reaching the desired temperature, an alkali solution is added to adjust the solution pH to 9-13.

6. The process for synthesizing renewable biomass-based epoxy resin from industrial pulping black liquor in aqueous phase according to claim 1, characterized in that: The reaction time is 10-300min.

7. The process for synthesizing renewable biomass-based epoxy resin from industrial pulping black liquor in aqueous phase according to claim 1, characterized in that: After centrifugation, the pH of the obtained upper dark solution is adjusted to neutral, and then dried to obtain the biomass-based epoxy resin.

8. The use of the biomass-based epoxy resin according to claims 1-7, characterized in that: The biomass-based epoxy resin can replace bisphenol A epoxy resin and be applied in the fields of aerospace, integrated circuit boards, structural carbon fiber glue, electronic sealants, adhesives, etc.

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