Pre-treatment of biomass and co-pyrolysis with polyurethane to produce nitrogen-containing chemicals and nitrogen-doped carbon materials

Abstract

The present application relates to the technical field of biomass utilization, and particularly relates to a method for preparing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane. The method comprises the following steps: crushing and drying biomass, and then sequentially performing hot spraying treatment, alkalization treatment, and fermentation treatment by mixing with urea to obtain pretreated biomass; mixing the pretreated biomass with polyurethane and a metal-supported catalyst, and performing co-pyrolysis treatment in an oxygen-deficient gas atmosphere to obtain volatile matter and co-pyrolysis residues, wherein the co-pyrolysis residues are nitrogen-doped carbon materials, and the condensate obtained after condensation of the volatile matter is nitrogen-containing chemicals. The present application solves the problems of high acidity, high oxygen content, low calorific value, high water content, and poor stability of biomass pyrolysis products, improves the content of nitrogen-containing compounds in biomass pyrolysis products, reduces the emission of pollutants such as NO x , SO x , and achieves the resource conversion and high-value utilization of biomass waste.

Description

Technical Field

[0001] This invention relates to the field of biomass utilization technology, specifically to the co-pyrolysis of pretreated biomass with polyurethane to produce nitrogen-containing chemicals and nitrogen-doped carbon materials. Background Technology

[0002] Biomass refers to various organic matter formed through photosynthesis, which can be converted into liquid, solid, and gaseous products through rapid pyrolysis technology. The liquid product is bio-oil, which can be used as fuel or to prepare high-value-added chemicals, such as nitrogen-containing heterocyclic compounds like pyridine, pyrrole, indole, aniline, and their derivatives. The solid product is biochar, a carbon-rich, nutrient-rich, porous adsorbent material that can be further used to prepare soil conditioners, low-cost adsorbents, and supercapacitors. The gaseous product is non-condensable biogas, composed of methane, hydrogen, carbon monoxide, etc., which can be used to prepare high-quality biomass synthetic natural gas to replace fossil fuels and provide fuel, heat, and electricity.

[0003] In biomass pyrolysis, the introduction of nitrogen-rich materials can promote the decomposition and transformation of organic matter in biomass, increasing the content of high-value-added chemicals such as olefins and nitrogen-containing compounds in the pyrolysis products. The introduction of hydrogen-rich materials can provide additional hydrogen, increasing the hydrocarbon content in the pyrolysis oil and allowing for more complete combustion of carbon in the bio-oil, thereby improving the quality of the pyrolysis oil and increasing energy efficiency. The addition of hydrogen-rich materials can also reduce the oxidation reactions of nitrogen and sulfur in biomass, thus reducing the emission of nitrogen oxides and sulfur oxides. Furthermore, the co-pyrolysis of biomass with nitrogen-rich materials introduces abundant nitrogen into biochar, resulting in nitrogen-doped carbon materials. Nitrogen-doped carbon materials exhibit excellent performance in adsorption and electrochemical properties, and have significant application value in environmental adsorption materials and supercapacitor electrode materials. Low energy density is one of the main problems restricting the rapid development of supercapacitors; nitrogen-doped carbon materials can effectively improve the pseudocapacitive properties of carbon materials, potentially solving the problem of low energy density. Therefore, the co-pyrolysis of biomass with other substances is currently a key research focus.

[0004] For example, patent CN105419848A describes the use of co-pyrolysis and catalytic hydrogenation of algae and waste rubber to produce bio-oil. By utilizing the high hydrogen content of waste rubber as a potential hydrogen source, co-pyrolysis with algal biomass can significantly reduce the oxygen content in bio-oil, indirectly reducing the amount of hydrogen used in the thermal high-resolution catalytic hydrogenation device and improving the quality of bio-oil.

[0005] Furthermore, polyurethane is a polymer material whose molecular structure contains multiple urethane bonds (NHCOO) and urea groups (H2N-CO-NH2), all of which contain nitrogen (N) and hydrogen (H) elements. Therefore, polyurethane has a relatively high N and H content, making it suitable as a nitrogen-rich or hydrogen-rich material for co-pyrolysis with biomass. Moreover, polyurethane materials are produced on a large scale, have a short service life, and a long environmental degradation time, resulting in a large amount of polyurethane solid waste and causing environmental pollution. Current methods for treating polyurethane waste mainly involve landfill and incineration, neither of which can effectively solve the environmental pollution problem. Co-pyrolysis of polyurethane with biomass to convert it into economically viable products is an effective treatment method.

[0006] For example, patent CN115780481A utilizes the co-pyrolysis of waste polyurethane materials and antibiotic bacterial residue to prepare nitrogen heterocyclic compounds, making full use of the synergistic effect between the physicochemical properties of the two to improve the selectivity and yield of nitrogen heterocyclic compounds; however, its reaction conditions are relatively complex, requiring strict control of parameters such as temperature and pressure during the pyrolysis process. Some harmful gases, such as ammonia and carbon dioxide, may be generated during the pyrolysis process, and corresponding measures need to be taken for gas treatment to avoid harm to the environment and human health.

[0007] Polyurethane contains a high nitrogen content of 10-20 wt.%, and co-pyrolysis of biomass with hydrogen- and nitrogen-rich raw materials such as polyurethane waste can effectively treat polyurethane waste and improve the yield and quality of biomass pyrolysis products. However, the diverse types and low selectivity of nitrogen-containing compounds in bio-oils still limit their further refining. To further increase the high-value application of biomass, research on pyrolysis pretreatment of biomass has been widely carried out.

[0008] For example, patent CN112646596A utilizes hypophosphoric acid or a mixture of hypophosphoric acid and organic-inorganic acids to pretreat biomass, obtaining a liquid product with L-glucan as the main product. Patent CN112876579A uses alkali-Fenton coupling pretreatment to modify the structure of biomass, significantly increasing the concentration of L-glucan and pyrolysis efficiency in bio-oil. While the pyrolysis effect of biomass after these pretreatments is improved, some problems remain. For instance, the product distribution of biomass pyrolysis technology is complex and difficult to control effectively, which may affect the quality and utilization of the final product. Furthermore, biomass pyrolysis technology requires a large amount of biomass material to generate sufficient energy and chemicals, potentially increasing production costs and resource consumption.

[0009] Therefore, researching an environmentally friendly and efficient co-pyrolysis material and pretreatment method to improve the quality of bio-oil and nitrogen-doped carbon materials is of great significance for realizing the high-value conversion of biomass. Summary of the Invention

[0010] To address the aforementioned problems in existing technologies, the purpose of this invention is to provide a method for producing nitrogen-containing chemicals and nitrogen-doped carbon materials through co-pyrolysis of pretreated biomass and polyurethane. This method solves the problems of high acidity, high oxygen content, low calorific value, high moisture content, and poor stability in biomass pyrolysis products, thereby increasing the content of nitrogen-containing compounds in biomass pyrolysis products and reducing NO content. x SO x The emission of pollutants has enabled the resource-based transformation and high-value utilization of biomass waste.

[0011] The present invention describes the process of co-pyrolyzing pretreated biomass with polyurethane to produce nitrogen-containing chemicals and nitrogen-doped carbon materials, comprising the following steps:

[0012] (1) Biomass pretreatment:

[0013] Biomass is crushed and dried to obtain biomass powder; the biomass powder is treated in saturated steam, and then the pressure is reduced to spray the biomass powder out to obtain thermally sprayed biomass raw material; the thermally sprayed biomass raw material is added to an alkaline solution for alkalization treatment, filtered, washed until neutral, and dried to obtain alkalized biomass raw material; the alkalized biomass raw material is mixed with urea for fermentation to obtain pretreated biomass;

[0014] (2) Co-pyrolysis treatment:

[0015] The pretreated biomass is mixed with polyurethane and a metal-supported catalyst and then subjected to co-pyrolysis in an oxygen-deficient gas atmosphere to obtain volatiles and co-pyrolysis residue. The co-pyrolysis residue is the nitrogen-doped carbon material, and the condensate obtained after condensation of the volatiles is the nitrogen-containing chemical.

[0016] In step (1), the biomass includes, but is not limited to, one or more of the following: wood, crop straw, fruit shells, leaves, bark, food processing residues, animal manure, aquatic plants, and algae. Wood can be birch, willow, beech, etc.; crop straw can be wheat straw, soybean straw, pea straw, etc.; fruit shells can be walnut shells, peanut shells, etc.

[0017] In step (1), after the biomass is crushed, 10-100 mesh biomass powder is sieved out and then dried at 80-200℃ for 8-48 hours.

[0018] In step (1), before the biomass powder is subjected to saturated steam treatment, it is preferable to knead and soften the biomass powder, that is, to knead the biomass powder by mechanical force, so as to change the internal fiber structure of the biomass, reduce its hardness, increase the surface area of ​​the biomass, increase its contact area with the external environment, which is conducive to the subsequent pyrolysis reaction and improves the energy conversion efficiency.

[0019] In step (1), the saturated steam treatment pressure is 0.2-15 MPa, the temperature is 100-200℃, and the time is 10-120 min. Saturated steam treatment is preferably carried out in a feed thermal sprayer. After saturated steam treatment, the pressure is rapidly reduced to allow the biomass powder to be sprayed out of the feed thermal sprayer, generally reducing the saturated steam pressure by about 50% within 5-60 seconds. Saturated steam treatment can promote the dissolution of lignin between biomass fiber cells, break hydrogen chains, and reduce fiber crystallinity. When the rapid pressure reduction causes the biomass powder to suddenly explode, stress is concentrated in the fragile structural areas of lignin, leading to loosening of the intercellular walls, cell detachment, and a sudden decrease in particle size, while the total surface area increases, which is beneficial for subsequent pyrolysis reactions, thereby further improving energy conversion efficiency.

[0020] In step (1), the alkaline solution is an aqueous solution of sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, ammonia, and sodium carbonate, preferably a calcium hydroxide solution.

[0021] The mass concentration of the alkaline solution is 3-30%, preferably 15%.

[0022] The mass-to-volume ratio of the biomass raw material after thermal spraying to the alkaline solution is 1g:(25-75)mL, preferably 1g:25mL.

[0023] During alkalization, the thermally sprayed biomass feedstock is added to an alkaline solution and stirred at 20-40°C for 1-5 hours. During alkalization, components such as cellulose, hemicellulose, and lignin in the biomass react with the alkali to generate soluble substances. These soluble substances are more easily vaporized during subsequent pyrolysis, thus increasing the yield of pyrolysis products. Furthermore, alkalization can remove some impurities and moisture from the biomass, improving its pyrolysis performance and enhancing the purity and quality of the pyrolysis products.

[0024] In step (1), after alkalization, the filter residue obtained by filtration is washed with water until the pH value is 7±0.5, and then the filter residue is dried at 80-200℃ for 8-48h to obtain alkalized biomass raw material.

[0025] In step (1), the mass ratio of the alkalized biomass raw material to urea is (0.5-2):1, preferably 1:1. Urea can improve the pyrolysis efficiency, control the migration and transformation of nitrogen elements, and act as a catalyst to convert biomass into high-value-added nitrogen-containing chemicals during biomass pyrolysis.

[0026] In step (1), fermentation is carried out in a sealed environment at room temperature for 20-60 days. During the fermentation process, components such as cellulose, hemicellulose, and lignin in the biomass will be degraded or transformed, making them easier to pyrolyze subsequently; it can also remove some impurities and moisture from the biomass, improving the quality and calorific value of the biomass, thereby improving the quality and yield of the pyrolysis products; it can also improve the physical properties of the biomass, such as increasing its porosity and specific surface area, improving its heat and mass transfer efficiency, thereby accelerating the pyrolysis process.

[0027] In step (2), the mass ratio of pretreated biomass to polyurethane is (1-4):1; the mass ratio of metal-supported catalyst to the total mass of pretreated biomass and polyurethane is 1:(1-4), preferably 1:1.

[0028] In step (2), polyurethane includes, but is not limited to, one or more of pure polyurethane, modified polyurethane, and waste polyurethane. Waste polyurethane can be waste polyurethane sponge, waste rigid polyurethane foam, waste polyurethane synthetic leather, waste polyurethane packaging materials, etc. Preferably, the polyurethane is pulverized before use and sieved to obtain polyurethane powder of 10-100 mesh. This invention uses a certain proportion of polyurethane to co-pyrolyze biomass, which can improve the bio-oil yield on the one hand, and remove most of the oxygen-containing compounds produced during biomass pyrolysis that would reduce the quality of bio-oil on the other hand. The amount of polyurethane added should be kept within a suitable range. Excessive addition will not only affect the bio-oil yield, but also may cause excessive polyurethane to accumulate on the surface of the biomass, hindering the escape of gas from inside the biomass particles, thus affecting the pyrolysis effect.

[0029] In step (2), the metal-supported catalyst is a supported catalyst of one or more metal elements selected from Fe, Mg, Pt, Zn, Na, Co, Ga, Ni, and Mo, preferably an Fe-based supported catalyst; the support for the metal-supported catalyst is one or more selected from ZSM-5 molecular sieve, HZSM-5 molecular sieve, H-BEA zeolite, HY molecular sieve, H-MOR molecular sieve, and natural zeolite, preferably HZSM-5 molecular sieve; the metal loading is 1-15 wt.%.

[0030] Preferably, one method for preparing the metal-supported catalyst is as follows:

[0031] The support is immersed in a precursor solution of loaded metal elements and stirred. After mixing, it is dried at 80-200℃ for 10-48h, and then treated in a reducing gas atmosphere at 400-800℃ for 1-10h. The catalyst is then pressed into tablets, crushed and ground to obtain a metal-supported catalyst with a metal loading of 1-15wt.%.

[0032] The mixing temperature is between 0-100℃, and the mixing time is 1-6h.

[0033] The reducing gas is one or more of H2, CO, H2S, CH4, and SO.

[0034] In step (2), during co-pyrolysis, the oxygen-deficient gas atmosphere is one or more of nitrogen, argon, helium, ammonia, CO2, and CO.

[0035] In step (2), the co-pyrolysis temperature is 400-800℃, preferably 500℃; the co-pyrolysis time is generally controlled between 5s and 60min, which is determined by the quality of the co-pyrolysis raw materials and the amount of volatiles generated during the co-pyrolysis process. When no volatiles are generated, the co-pyrolysis is completed.

[0036] In step (2), after co-pyrolysis, the condensation temperature of the volatiles is -30℃ to 30℃. After the volatiles are condensed, the resulting condensate is a nitrogen-containing chemical, and the non-condensable gas is a non-condensable biomass gas.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) The present invention utilizes alkaline substances to treat biomass, which can destroy the ester bonds between cellulose, hemicellulose and lignin, change the composition and structure of biomass, thereby improving its pyrolysis efficiency and reducing energy consumption in the biomass pyrolysis process.

[0039] (2) This invention introduces urea and biomass into a sealed fermentation process to increase the N content of biomass, effectively increasing the yield of nitrogen-containing compounds in the pyrolysis products. The sealed fermentation process can effectively decompose and transform components such as cellulose, hemicellulose and lignin in biomass raw materials, especially some recalcitrant organic substances, thereby improving the quality of biomass raw materials, increasing its pyrolysis efficiency and product quality. At the same time, some harmful substances in biomass raw materials, such as sulfides and nitrogen oxides, can be removed during the sealed fermentation process, thereby reducing the pollution generated by these substances during the pyrolysis process and making the biomass pyrolysis process more environmentally friendly.

[0040] (3) This invention uses polyurethane and biomass co-pyrolysis. Polyurethane contains a large amount of N and H elements. On the one hand, N and H elements can interact with a large amount of organic matter such as cellulose and hemicellulose contained in biomass to promote its decomposition and improve the utilization rate of biomass. On the other hand, N and H elements will combine with carbon atoms in other organic molecules during co-pyrolysis to form new chemical bonds. These chemical bonds have high energy, and the products formed also have high energy density, thereby realizing the high-value utilization of biomass.

[0041] (4) The present invention adds a metal-supported catalyst during the pyrolysis process, which can improve the yield of hydrocarbons and the selectivity of light aromatics such as benzene, toluene and xylene.

[0042] (5) This invention pre-treats biomass by hot spraying, alkalization, and urea mixed fermentation, and then mixes it with polyurethane for co-pyrolysis. This solves the problems of high acidity, high oxygen content, low calorific value, high water content and poor stability of nitrogen-containing chemicals in biomass pyrolysis products. It greatly improves the nitrogen content of nitrogen-containing chemicals. At the same time, the nitrogen-doped carbon material obtained by pyrolysis has rich microporous structure and high specific surface area, exhibiting excellent specific capacitance performance, and can be used to prepare supercapacitor electrode materials.

[0043] (6) The pyrolysis process of this invention reduces NO x SO x The emission of pollutants has enabled the resource-based transformation and high-value utilization of biomass and polyurethane waste. Detailed Implementation

[0044] The present invention will be further described below with reference to the embodiments. Unless otherwise specified, the raw materials used in the embodiments are all commercially available conventional raw materials; unless otherwise specified, the process methods used in the embodiments are all conventional methods in the art.

[0045] The metal-supported catalyst used in the examples mainly plays the role of promoting the co-pyrolysis reaction. The supported metal element is one or more of Fe, Mg, Pt, Zn, Na, Co, Ga, Ni, and Mo. The metal loading is controlled in the range of 1-15 wt.%, which can achieve good catalytic effect.

[0046] In Examples 1-3, 6 wt.% Fe-supported catalysts (6 wt.% Fe / HZSM-5), 1 wt.% Mg-supported catalysts (1 wt.% Mg / HZSM-5), and 15 wt.% Zn-supported catalysts (15 wt.% Zn / HZSM-5) were used, respectively, with ZSM-5 molecular sieve as the support. Taking the 6 wt.% Fe-supported catalyst as an example, its preparation method is as follows:

[0047] With an Fe loading of 6 wt.%, HZSM-5 molecular sieve was immersed in Fe(NO3)3·9H2O aqueous solution and stirred at 80℃ for 2 h. After being removed, it was dried at 105℃ for 12 h and then reduced at 600℃ in H2 atmosphere for 6 h. The sieve was then pressed into tablets, crushed and ground, and particles with a particle size between 100-1000 μm were screened to obtain the Fe-based supported catalyst (6 wt.% Fe / HZSM-5).

[0048] Example 1

[0049] The process of this invention involves co-pyrolysis of biomass and polyurethane, with the following steps:

[0050] (1) Biomass pretreatment:

[0051] Wheat straw was used as biomass. The wheat straw was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 105℃ for 36 hours to obtain wheat straw powder.

[0052] Wheat straw powder is placed in a rubbing and crushing machine, and softened by mechanical action. Then it is loaded into a feed thermal sprayer and kept under saturated steam at 1.2 MPa and 150°C for 2 hours. Then the saturated steam is reduced to 0.6 MPa within 15 seconds. The rapid pressure reduction causes the material to be sprayed out of the feed thermal sprayer, resulting in thermally sprayed biomass.

[0053] The biomass raw material after thermal spraying was mixed with a 15% ammonia solution at a ratio of 1g:35mL and stirred at 20℃ for 2h for alkalization treatment. Then it was filtered, and the filter residue was washed with water until the pH value was 7±0.5. Then it was placed in a drying oven at 102℃ for 25h to obtain alkalized biomass.

[0054] The alkalized biomass raw material was mixed with urea at a mass ratio of 1:1, placed in a sealed container, and fermented for 30 days to obtain pretreated biomass.

[0055] (2) Co-pyrolysis treatment:

[0056] Waste rigid polyurethane foam is crushed using a pulverizer and sieved to obtain 10-100 mesh waste rigid polyurethane foam powder. Pretreated biomass and waste rigid polyurethane foam powder are mixed at a mass ratio of 1:1. Then, 6wt.% Fe / HZSM-5 catalyst with a mass ratio of 1:2 to the total mass of pretreated biomass and waste rigid polyurethane foam powder is added. After mixing evenly, the mixture is added to a pyrolysis reactor, and nitrogen gas is introduced. When the temperature rises to 500℃, the material is pushed to the heating zone for co-pyrolysis. The volatiles are condensed in a cold trap at a temperature of -10℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0057] Example 2

[0058] The process of this invention involves co-pyrolysis of biomass and polyurethane, with the following steps:

[0059] (1) Biomass pretreatment:

[0060] Poplar wood was used as biomass. The poplar wood was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 80℃ for 48 hours to obtain poplar wood powder.

[0061] Poplar wood powder is placed in a kneading and pulverizing machine and softened by mechanical action. Then it is loaded into a feed thermal sprayer and kept under saturated steam at 0.2 MPa and 100°C for 10 minutes. Then the pressure is reduced to 0.1 MPa within 5 seconds. The rapid reduction of pressure causes the material to be sprayed out of the feed thermal sprayer, resulting in thermally sprayed biomass.

[0062] The biomass raw material after thermal spraying was mixed with a 3% sodium hydroxide solution at a ratio of 1g:25mL and stirred at 25℃ for 1h for alkalization treatment. Then it was filtered, and the filter residue was washed with water until the pH value was 7±0.5. Then it was placed in an 80℃ drying oven for 48h to obtain alkalized biomass.

[0063] The alkalized biomass raw material was mixed with urea at a mass ratio of 0.5:1, placed in a sealed container, and fermented for 20 days to obtain pretreated biomass.

[0064] (2) Co-pyrolysis treatment:

[0065] Waste polyurethane foam is crushed using a pulverizer and sieved to obtain 10-100 mesh waste polyurethane foam powder. Pretreated biomass and waste polyurethane foam powder are mixed at a mass ratio of 2:1. Then, 1wt.% Mg / HZSM-5 catalyst with a mass ratio of 1:1 to the total mass of pretreated biomass and waste polyurethane foam powder is added. After mixing evenly, the mixture is added to a pyrolysis reactor, and argon gas is introduced. When the temperature rises to 400℃, the material is pushed to the heating zone for co-pyrolysis. The volatiles are condensed in a cold trap at a temperature of -30℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0066] Example 3

[0067] The process of this invention involves co-pyrolysis of biomass and polyurethane, with the following steps:

[0068] (1) Biomass pretreatment:

[0069] Walnut shells were used as biomass. The walnut shells were dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, the powder was dried in an oven at 100℃ for 8 hours to obtain walnut shell powder.

[0070] Walnut shell powder is placed in a kneading and pulverizing machine and softened by mechanical action. Then it is loaded into a feed thermal sprayer and kept under saturated steam at 15 MPa and 200℃ for 150 minutes. Then the pressure is reduced by 2.5 MPa within 60 seconds. The rapid reduction of pressure causes the material to be sprayed out of the feed thermal sprayer, resulting in thermally sprayed biomass.

[0071] The thermally sprayed biomass raw material was mixed with a 30% sodium carbonate solution at a ratio of 1g:75mL and stirred at 35℃ for 5h for alkalization treatment. Then it was filtered, and the filter residue was washed with water until the pH value was 7±0.5. Then it was placed in a drying oven at 200℃ for 8h to obtain alkalized biomass.

[0072] The alkalized biomass raw material was mixed with urea at a mass ratio of 2:1, placed in a sealed container, and fermented for 60 days to obtain pretreated biomass.

[0073] (2) Co-pyrolysis treatment:

[0074] Waste polyurethane synthetic leather is crushed using a pulverizer and screened to obtain 10-100 mesh waste polyurethane synthetic leather powder. The pretreated biomass and waste polyurethane synthetic leather powder are mixed at a mass ratio of 4:1. Then, a 15wt.% Zn / HZSM-5 catalyst with a mass ratio of 1:4 to the total mass of the pretreated biomass and waste polyurethane synthetic leather powder is added. After mixing evenly, the mixture is added to a pyrolysis reactor, and CO2 is introduced. When the temperature rises to 800℃, the material is pushed to the heating zone for co-pyrolysis. The volatiles are condensed in a cold trap at a temperature of 30℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0075] Comparative Example 1

[0076] The only difference between this comparative example and Example 1 is that the wheat straw powder is not subjected to thermal spraying, alkalization, or fermentation treatment. The steps are as follows:

[0077] (1) Biomass pretreatment:

[0078] Wheat straw was used as biomass. The wheat straw was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 105℃ for 36 hours to obtain wheat straw powder.

[0079] (2) Co-pyrolysis treatment:

[0080] Waste rigid polyurethane foam is crushed using a pulverizer and sieved to obtain 10-100 mesh waste rigid polyurethane foam powder. Wheat straw powder and waste rigid polyurethane foam powder are mixed at a mass ratio of 1:1, and then 6wt.% Fe / HZSM-5 catalyst with a mass ratio of 1:2 to the total mass of wheat straw powder and waste rigid polyurethane foam powder is added. After mixing evenly, the mixture is added to a pyrolysis reactor, and nitrogen gas is introduced. When the temperature rises to 500℃, the material is pushed to the heating zone for co-pyrolysis. The volatiles are condensed in a cold trap at a temperature of -10℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0081] Comparative Example 2

[0082] The only difference between this comparative example and Example 1 is that the wheat straw powder is not subjected to thermal spraying, alkalization, or fermentation treatment, nor is it co-pyrolyzed with waste rigid polyurethane foam powder. The steps are as follows:

[0083] (1) Biomass pretreatment:

[0084] Wheat straw was used as biomass. The wheat straw was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 105℃ for 36 hours to obtain wheat straw powder.

[0085] (2) Pyrolysis treatment:

[0086] Add 6wt.% Fe / HZSM-5 catalyst at a mass ratio of 1:2 to wheat straw powder, mix well, and then add to a pyrolysis reactor. Introduce nitrogen gas, and when the temperature reaches 500℃, push the material to the heating zone for pyrolysis. The volatiles are condensed in a cold trap at a temperature of -10℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0087] Comparative Example 3

[0088] The only difference between this comparative example and Example 1 is that thermal spraying is not performed. The steps are as follows:

[0089] (1) Biomass pretreatment:

[0090] Wheat straw was used as biomass. The wheat straw was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 105℃ for 36 hours to obtain wheat straw powder.

[0091] Wheat straw powder was mixed with a 15% ammonia solution at a ratio of 1g:35mL and stirred at 20℃ for 2h for alkalization treatment. Then it was filtered, and the filter residue was washed with water until the pH value was 7±0.5. Then it was placed in a drying oven at 102℃ for 25h to obtain alkalized biomass.

[0092] The alkalized biomass raw material was mixed with urea at a mass ratio of 1:1, placed in a sealed container, and fermented for 30 days to obtain pretreated biomass.

[0093] (2) Co-pyrolysis treatment:

[0094] Waste rigid polyurethane foam is crushed using a pulverizer and sieved to obtain 10-100 mesh waste rigid polyurethane foam powder. The pretreated biomass and waste rigid polyurethane foam powder are mixed at a mass ratio of 1:1, and then 6wt.% Fe / HZSM-5 catalyst with a mass ratio of 1:2 to the total mass of biomass and waste rigid polyurethane foam is added. After mixing evenly, the mixture is added to a pyrolysis reactor, and nitrogen gas is introduced. When the temperature rises to 500℃, the material is pushed to the heating zone for co-pyrolysis. The volatiles are condensed in a cold trap at a temperature of -10℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0095] Comparative Example 4

[0096] The only difference between this comparative example and Example 1 is that no alkalization treatment is performed. The steps are as follows:

[0097] (1) Biomass pretreatment:

[0098] Wheat straw was used as biomass. The wheat straw was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 105℃ for 36 hours to obtain wheat straw powder.

[0099] Wheat straw powder is placed in a rubbing and crushing machine, and softened by mechanical action. Then it is loaded into a feed thermal sprayer and kept under saturated steam at 1.2 MPa and 150°C for 2 hours. Then the saturated steam is reduced to 0.6 MPa within 15 seconds. The rapid pressure reduction causes the material to be sprayed out of the feed thermal sprayer, resulting in thermally sprayed biomass.

[0100] The biomass raw material after thermal spraying was mixed with urea at a mass ratio of 1:1, and placed in a sealed container for fermentation for 30 days to obtain pretreated biomass.

[0101] (2) Co-pyrolysis treatment:

[0102] Waste rigid polyurethane foam is crushed using a pulverizer and sieved to obtain 10-100 mesh waste rigid polyurethane foam powder. The pretreated biomass and waste rigid polyurethane foam powder are mixed at a mass ratio of 1:1, and then 6wt.% Fe / HZSM-5 catalyst with a mass ratio of 1:2 to the total mass of biomass and waste rigid polyurethane foam is added. After mixing evenly, the mixture is added to a pyrolysis reactor, and nitrogen gas is introduced. When the temperature rises to 500℃, the material is pushed to the heating zone for co-pyrolysis. The volatiles are condensed in a cold trap at a temperature of -10℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0103] Comparative Example 5

[0104] The only difference between this comparative example and Example 1 is that no fermentation treatment is performed. The steps are as follows:

[0105] (1) Biomass pretreatment:

[0106] Wheat straw was used as biomass. The wheat straw was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 105℃ for 36 hours to obtain wheat straw powder.

[0107] Wheat straw powder is placed in a rubbing and crushing machine, and softened by mechanical action. Then it is loaded into a feed thermal sprayer and kept under saturated steam at 1.2 MPa and 150°C for 2 hours. Then the saturated steam is reduced to 0.6 MPa within 15 seconds. The rapid pressure reduction causes the material to be sprayed out of the feed thermal sprayer, resulting in thermally sprayed biomass.

[0108] The biomass raw material after thermal spraying was mixed with a 15% ammonia solution at a ratio of 1g:35mL and stirred at 20℃ for 2h for alkalization treatment. Then it was filtered, and the filter residue was washed with water until the pH value was 7±0.5. Then it was placed in a drying oven at 102℃ for 25h to obtain alkalized biomass.

[0109] (2) Co-pyrolysis treatment:

[0110] Waste rigid polyurethane foam is crushed using a pulverizer and sieved to obtain 10-100 mesh waste rigid polyurethane foam powder. The alkalized biomass is mixed with the waste rigid polyurethane foam powder at a mass ratio of 1:1. Then, a 6wt.% Fe / HZSM-5 catalyst with a mass ratio of 1:2 (total mass of alkalized biomass and waste rigid polyurethane foam powder) is added and mixed thoroughly. This mixture is then added to a pyrolysis reactor, and nitrogen gas is introduced. When the temperature reaches 500℃, the material is pushed to the heating zone for co-pyrolysis. The volatiles are condensed in a cold trap at -10℃. The resulting condensate is a nitrogen-containing chemical, the non-condensable gas is non-condensable biomass gas, and the co-pyrolysis residue is a nitrogen-doped carbon material.

[0111] Comparative Example 6

[0112] The only difference between this comparative example and Example 1 is that it is not mixed with polyurethane for co-pyrolysis. The steps are as follows:

[0113] (1) Biomass pretreatment:

[0114] Wheat straw was used as biomass. The wheat straw was dried indoors in a ventilated environment, crushed with a pulverizer, and sieved to obtain 10-100 mesh powder. Then, it was dried in an oven at 105℃ for 36 hours to obtain wheat straw powder.

[0115] Wheat straw powder is placed in a rubbing and crushing machine, and softened by mechanical action. Then it is loaded into a feed thermal sprayer and kept under saturated steam at 1.2 MPa and 150°C for 2 hours. Then the saturated steam is reduced to 0.6 MPa within 15 seconds. The rapid pressure reduction causes the material to be sprayed out of the feed thermal sprayer, resulting in thermally sprayed biomass.

[0116] The biomass raw material after thermal spraying was mixed with a 15% ammonia solution at a ratio of 1g:35mL and stirred at 20℃ for 2h for alkalization treatment. Then it was filtered, and the filter residue was washed with water until the pH value was 7±0.5. Then it was placed in a drying oven at 102℃ for 25h to obtain alkalized biomass.

[0117] The alkalized biomass raw material was mixed with urea at a mass ratio of 1:1, placed in a sealed container, and fermented for 30 days to obtain pretreated biomass.

[0118] (2) Pyrolysis treatment:

[0119] 6wt.% Fe / HZSM-5 catalyst at a mass ratio of 1:2 was added to the pretreated biomass feedstock. After mixing evenly, the mixture was added to the pyrolysis reactor, and nitrogen gas was introduced. When the temperature reached 500℃, the material was pushed to the heating zone for pyrolysis. The volatiles were condensed in a cold trap at a temperature of -10℃. The resulting condensate is the nitrogen-containing chemical, the non-condensable gas is the non-condensable biomass gas, and the co-pyrolysis residue is the nitrogen-doped carbon material.

[0120] The component content and calorific value of the nitrogen-containing chemicals obtained in each example and comparative example were detected using gas chromatography-mass spectrometry and a calorific value analyzer, respectively. The results are shown in Table 1, where NHCs represent nitrogen-containing heterocyclic substances. The specific surface area, maximum nitrogen doping amount, and specific capacitance of the nitrogen-doped carbon materials obtained in each example and comparative example were detected using a specific surface area and micropore analyzer, an elemental analyzer, and an electrochemical workstation, respectively.

[0121] Table 1 Nitrogen-containing chemical indicators

[0122]

[0123] Table 2 Indicators of Nitrogen-Doped Carbon Materials

[0124]

[0125] As can be seen from Tables 1-2, the nitrogen-containing heterocyclic substances in the nitrogen-containing chemicals produced by co-pyrolysis of biomass with polyurethane after thermal spraying, alkalization, and fermentation are significantly increased. The main reasons are as follows: fermentation pretreatment degrades or transforms components such as cellulose, hemicellulose, and lignin in the biomass; thermal spraying pretreatment dissolves lignin between biomass fiber cells, breaks hydrogen chains, reduces fiber crystallinity, increases the specific surface area of ​​biomass, and facilitates the Maillard reaction; alkalization treatment increases the relative content of cellulose in the raw material, and furan and other small molecule oxygen-containing compounds (ethanol aldehyde, hydroxyacetone, aldehyde, etc.) produced by cellulose pyrolysis are intermediates for the formation of nitrogen-containing compounds, thereby promoting the generation of nitrogen-containing chemicals. Alkaliization treatment also helps to increase carbonyl groups, and the introduction of a large number of carbonyl groups is conducive to capturing nitrogen-containing free radicals to form nitrogen-containing compounds; adding polyurethane as a hydrogen-rich and nitrogen-rich raw material for co-pyrolysis, the large amount of N and H elements contained in polyurethane can promote the decomposition of cellulose and hemicellulose, and at the same time combine with carbon atoms in other organic molecules to form high-energy chemical bonds, thereby increasing the calorific value of nitrogen-containing chemicals.

[0126] The nitrogen-doped carbon material obtained by co-pyrolysis in this invention has a rich microporous structure and a high specific surface area, exhibiting excellent specific capacitance performance. The main reasons are as follows: First, after the biomass undergoes pretreatment such as thermal spraying, alkalization, and fermentation, the sample surface is corroded and damaged, which facilitates the full pyrolysis of the raw materials and increases the specific surface area and microporous structure of the raw materials. Second, after co-pyrolysis with polyurethane, the nitrogen content in the nitrogen-doped carbon material is significantly increased. In addition, nitrogen-containing groups (pyridine-N, pyrrole-N, etc.) react with the original oxygen-containing groups and embed into the carbon skeleton, thereby improving the specific capacitance performance of the carbon material through synergistic effect.

[0127] In contrast, in Comparative Examples 1-6, the reduction of one or more pretreatment steps or the omission of co-pyrolysis with polyurethane resulted in varying degrees of reduction in the content of nitrogen-containing heterocyclic substances in the obtained nitrogen-containing chemicals, and the calorific value of the nitrogen-containing chemicals also decreased relatively. At the same time, the specific surface area, maximum nitrogen doping amount, and specific capacitance of the nitrogen-doped carbon materials also decreased to varying degrees.

Claims

1. A method for preparing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane, characterized in that: Includes the following steps: (1) Biomass pretreatment: Biomass is crushed and dried to obtain biomass powder; After treating the biomass powder in saturated steam, the pressure is reduced to spray the biomass powder out, resulting in thermally sprayed biomass raw material. The thermally sprayed biomass raw material is then added to an alkaline solution for alkalization treatment, filtered, washed until neutral, and dried to obtain alkalized biomass raw material. The alkalized biomass raw material is mixed with urea and fermented to obtain pretreated biomass. The mass ratio of alkalized biomass raw material to urea is (0.5-2):1; (2) Co-pyrolysis treatment: The pretreated biomass is mixed with polyurethane and metal-supported catalyst and subjected to co-pyrolysis in an oxygen-deficient gas atmosphere to obtain volatiles and co-pyrolysis residue. The co-pyrolysis residue is nitrogen-doped carbon material, and the condensate obtained after condensation of the volatiles is nitrogen-containing chemical. Among them, the metal supported catalyst is a supported catalyst of one or more metal elements selected from Fe, Mg, Pt, Zn, Na, Co, Ga, Ni, and Mo, with a metal loading of 1-15 wt.%.

2. The method for preparing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane according to claim 1, characterized in that: In step (1), the saturated steam treatment pressure is 0.2-15 MPa, the temperature is 100-200℃, and the time is 10-120 min.

3. The method for producing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane according to claim 1, characterized in that: In step (1), the alkaline solution is an aqueous solution of sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia, and sodium carbonate; the mass concentration of the alkaline solution is 3-30%.

4. The method for producing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane according to claim 1, characterized in that: In step (1), the mass-to-volume ratio of the biomass raw material after thermal spraying to the alkaline solution is 1g:(25-75)mL.

5. The method for producing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane according to claim 1, characterized in that: In step (2), the mass ratio of pretreated biomass to polyurethane is (1-4):

1.

6. The method for producing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane according to claim 1, characterized in that: In step (2), the mass ratio of the metal-supported catalyst to the total mass of the pretreated biomass and polyurethane is 1:(1-4).

7. The method for producing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane according to claim 1, characterized in that: In step (2), the co-pyrolysis temperature is 400-800℃.

8. The method for preparing nitrogen-containing chemicals and nitrogen-doped carbon materials by co-pyrolysis of pretreated biomass and polyurethane according to claim 1, characterized in that: In step (2), after co-pyrolysis treatment, the condensation temperature of the volatiles is -30℃ to 30℃. After the volatiles are condensed, the resulting condensate is a nitrogen-containing chemical, and the non-condensable gas is a non-condensable biomass gas.

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