Production process of pyridine-rich bio-oil from pretreated biomass fractionation and nitrogen-enriched pyrolysis

Abstract

This invention belongs to the field of biomass high-value utilization technology, specifically relating to a production process for preparing pyridine-rich bio-oil from pretreated biomass through graded nitrogen-enriched pyrolysis. The graded nitrogen-enriched pyrolysis process of this invention involves setting different pyrolysis reaction temperature ranges based on the pyrolysis characteristics of the three major components of biomass, and collecting pyrolysis steam with relatively high concentrations of different components at each stage. Under nitrogen-enriched pyrolysis conditions, aldehyde- and ketone-rich pyrolysis steam is converted into pyridine-rich bio-oil. For pyrolysis steam with low aldehyde and ketone content, further online catalytic control is used to convert easily aldehyde- and ketone-converted components into aldehydes and ketones, which are then subjected to nitrogen-enriched pyrolysis. Pyrolysis steam with higher content of less easily aldehyde- and ketone-converted components is used to prepare liquid fuels or other chemicals, achieving graded and high-value utilization of all biomass components.

Description

Technical Field

[0001] This invention belongs to the field of biomass high-value utilization technology, specifically involving a production process for preparing pyridine-rich bio-oil by pre-treatment biomass grading-nitrogen-enriched pyrolysis. Background Technology

[0002] Nitrogen-containing compounds play a vital role in fine chemicals, with pyridine and its derivatives being among the most common skeletons in pharmaceutical molecules and agrochemicals, resulting in a huge annual demand. For example, pyridine pesticides are considered fourth-generation pesticides, possessing advantages such as high efficiency, low toxicity, and good environmental compatibility. Furthermore, some pyridine derivatives exhibit good fluorescence properties, making them important for applications in energy fields such as electroluminescent materials. However, currently, industrial synthesis of pyridine compounds primarily involves multi-step reactions from fossil fuels, resulting in complex processes and significant pollutant emissions. Research indicates that compared to petroleum-based hydrocarbons, biomass-based materials are more readily ammonified to form nitrogen-containing chemicals. Therefore, utilizing the pyrolysis of biomass to prepare high-value-added nitrogen-containing compounds such as pyridines is of great significance.

[0003] There are many synthetic routes for pyridine compounds. For example, the main chemical synthesis methods for pyridine bases (pyridine and its methyl-substituted derivatives) in industry include the aldehyde (ketone)-ammonia method, the acetylene-acetonitrile method, and the side-chain alkylation method, with the aldehyde (ketone)-ammonia method currently being the dominant one. Most biomass in nature has a low nitrogen content, which cannot meet the conditions for the large-scale formation of nitrogen-containing chemicals. Therefore, there are two main routes for the rapid pyrolysis of nitrogen-containing compounds such as pyridine: (1) A single intermediate oxygen-containing substance, such as aldehyde, ketone, acetic acid, ethanol, etc., is obtained in a directional manner and then catalyzed in an ammonia atmosphere.

[0004] (2) The pyrolysis process directly introduces exogenous nitrogen (such as NH3, urea, etc., which is called "nitrogen-rich pyrolysis") to catalyze the production of pyridine compounds.

[0005] Compared with route (1), route (2) does not require the separation of intermediate products, reducing the energy-intensive steps of bio-oil condensation-component purification-re-evaporation reactions, transforming a multi-step reaction into a single step, shortening the process route, and offering advantages such as high atom utilization. Studies have shown that small molecule aldehydes and ketones are important intermediates for the formation of pyridine compounds (CN202210149448.4); under high-temperature conditions, weakly acidic catalysts and short residence times readily form pyridine compounds; nitrogen-containing compounds such as indole can also be converted into pyridine compounds under certain conditions. However, due to the reactivity of aldehydes and ketones, condensation transformation easily occurs during the purification process. Therefore, by controlling the biomass pyrolysis reaction process, pyrolysis product components mainly composed of aldehydes and ketones can be directionally generated, significantly improving the yield of pyridine compounds and their enrichment in bio-oil under nitrogen-rich pyrolysis conditions.

[0006] Agricultural and forestry biomass has the characteristics of being rich in oxygen and poor in nitrogen (oxygen content 30-50%, nitrogen content <0.5%). Although the introduction of exogenous nitrogen during pyrolysis can significantly increase the yield of nitrogen-containing compounds in bio-oil, the selectivity of pyridine compounds is still low (generally <10%). The main reasons are: (1) Traditional biomass pyrolysis is a single-stage pyrolysis, that is, the raw material is only pyrolyzed at a specific temperature. The product precipitation temperature ranges of cellulose, hemicellulose and lignin in biomass overlap, and there are certain differences in the composition of the products. Bio-oil obtained by nitrogen-rich pyrolysis contains a variety of nitrogen-containing compounds and low content of pyridine products. The pyrolysis temperature ranges of the three components of biomass overlap, and there are complex interactive reactions between the pyrolysis products. For example, the main pyrolysis range of cellulose is 300-400℃, and the products are sugars and aldehydes and ketones, etc.; the main pyrolysis range of hemicellulose is 200-300℃, and the products are acids, cyclopentanones and furans, etc. Cellulose and hemicellulose are mainly converted into pyrrole, pyridine and indole during nitrogen-rich pyrolysis. The main pyrolysis range of lignin is 250-500℃, and the products are phenols, aromatic hydrocarbons, etc. During nitrogen-rich pyrolysis, it is mainly converted into aromatic amines (CN202410176052.8). (2) The various inorganic mineral elements (including K, Ca, Na, Mg, Fe, etc.) contained in biomass itself exacerbate the complexity of pyrolysis reaction and bio-oil components (CN202010712825.1).

[0007] In single-stage pyrolysis, higher pyrolysis temperatures are beneficial for increasing bio-oil yield. However, at this temperature, multiple pyrolysis products are released almost simultaneously, making it difficult to effectively control the products under fixed catalytic conditions, resulting in complex bio-oil composition. At lower pyrolysis temperatures, although some target products show high selectivity in bio-oil, incomplete pyrolysis leads to low yields. Furthermore, acids, alcohols, esters, and sugars produced by biomass pyrolysis are not easily converted into nitrogen-containing compounds such as pyridines under non-catalytic ammonia conditions, while these substances can be converted into aldehydes and ketones via deoxygenation reactions (CN201410213889.1). Considering the complexity of single-stage pyrolysis products and the difficulty in achieving coordinated transformation of multiple components under fixed catalytic conditions, the relative enrichment advantage of components in staged pyrolysis can be utilized to control aldehyde-ketalization reactions by preparing pyrolysis vapors rich in readily aldehyde-ketalized substances.

[0008] Furthermore, the composition of aldehydes and ketones obtained under different pyrolysis atmospheres and with different types of catalysts varies greatly. For example, in a CO2 atmosphere, CO2 provides oxygen for the carbonylation reaction, increasing the yield of ketones; simultaneously, CO2 adsorbs on the catalyst surface, blocking surface active sites and inhibiting the carbonylation reaction. Metal-organic frameworks (MOFs), due to their highly ordered structure, high specific surface area, and precisely customizable composition, exhibit significant advantages in chemical tunability, insolubility, and recyclability, and have been widely used in recent years as heterogeneous porous catalysts for photocatalysis and CO2 reduction. Therefore, it is necessary to directionally control the preparation of pyridine compounds through methods such as raw material pretreatment, high-efficiency catalysts, and pyrolysis conditions. Summary of the Invention

[0009] The purpose of this invention is to provide a production process for preparing pyridine-rich bio-oil from pretreated biomass through graded nitrogen-enriched pyrolysis. This process sets different pyrolysis reaction temperature ranges based on the pyrolysis characteristics of the three main components of biomass, and collects pyrolysis steam with relatively high concentrations of different components stepwise. Because the pyrolysis products are released in stages during graded nitrogen-enriched pyrolysis, the complexity of the bio-oil components can be reduced. Furthermore, by selectively preparing aldehyde- and ketone-rich pyrolysis steam and readily aldehyde- and ketone-forming pyrolysis steam through process control, components that are not easily aldehyde- and ketone-forming can be effectively separated, significantly improving the yield and selectivity of pyridine compounds in the graded pyrolysis bio-oil, which is beneficial for subsequent product separation and processing.

[0010] The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to the present invention consists of the following steps: (1) First, the biomass is crushed and screened to obtain biomass powder. Then, the biomass powder is added to a washing solution for pretreatment. After filtration, washing and drying, pretreated biomass is obtained. (2) The mesoporous molecular sieve was dispersed in deionized water, and then a first metal salt solution was added. After stirring, drying and calcining, a metal oxide modified mesoporous molecular sieve catalyst was prepared. (3) Disperse MOF in deionized water, then add a second metal salt solution, stir, dry and calcine to prepare a bimetallic supported MOF-based catalyst; (4) After the pretreated biomass prepared in step (1) is mixed evenly with the metal oxide modified mesoporous molecular sieve catalyst prepared in step (2), it is added to the first pyrolysis reactor and subjected to staged pyrolysis under an oxygen-free atmosphere to obtain the first aldehyde- and ketone-rich pyrolysis steam, the aldehyde- and ketone-easily pyrolysis steam and the aldehyde- and ketone-easily pyrolysis steam in different temperature ranges. (5) The first aldehyde- and ketone-rich pyrolysis vapor from step (4) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under ammonia conditions. The volatiles are introduced into the No. 1 condenser and condensed to obtain the first pyridine-rich bio-oil. (6) The pyrolysis steam that is easily aldehyde-ketone converted in step (4) is passed into a catalytic reactor carrying the bimetallic supported MOF-based catalyst prepared in step (3) to carry out an ex-situ catalytic online aldehyde-ketone conversion reaction of the pyrolysis steam to obtain a second aldehyde-ketone rich pyrolysis steam. (7) The second aldehyde- and ketone-rich pyrolysis vapor from step (6) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under ammonia conditions. The volatiles are introduced into the No. 2 condenser and condensed to obtain the second pyridine-rich bio-oil. (8) Pass the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) into condenser tube No. 3 and condense to obtain bio-oil.

[0011] in: The biomass mentioned in step (1) refers to one or more of the following: wood, crop straw, fruit shells, leaves, bark, food processing residues (residual substances or waste generated during food processing, such as the leaves, stems, and roots of vegetables, as well as the remaining parts after processing meat and seafood), or model compounds. Specifically, the wood is one or more of pine, poplar, or camphor wood; the crop straw is one or more of corn straw, cotton straw, or wheat straw, preferably wheat straw; the fruit shell is one or more of coconut shell, grapefruit peel, or walnut shell; and the model compound is one or more of cellulose, glucose, xylose, xylan, alkali lignin, aldehyde, or ketone.

[0012] In step (1), the particle size of the biomass powder is 40-100 mesh.

[0013] When the biomass in step (1) is a model compound, there is no need to add the model compound to the washing solution for pretreatment. The model compound is directly washed and dried to obtain pretreated biomass.

[0014] The washing solution mentioned in step (1) is one of an acidic solution, an alkaline solution, or an oxidizing solution. The acidic solution is a mixture of one of acetic acid, formic acid, oxalic acid, or propionic acid with deionized water, and the concentration of the acidic solution is 1-10 mol / L. The alkaline solution is a sodium hydroxide solution with a concentration of 1-10 mol / L. The oxidizing solution is a hydrogen peroxide solution with a concentration of 1-10 mol / L.

[0015] In step (1), the mass-to-volume ratio of biomass powder to washing solution is 1:25-75, in g / mL; preferably, the mass-to-volume ratio of biomass powder to washing solution is 1:25, in g / mL.

[0016] In step (1), the biomass powder is immersed in the prepared washing solution and pretreated by stirring at 20-40℃ for 1-5 hours using a constant temperature magnetic rotor stirrer. The pretreated raw material is repeatedly washed with deionized water until the pH value of the last filtered water is 7±0.03. Then the filter residue is dried at 80-200℃ for 8-48 hours to obtain pretreated biomass.

[0017] The mesoporous molecular sieve mentioned in step (2) refers to one or more of the M41S series, MSU series, or SBA series. The M41S series is one of the MCM-41 mesoporous molecular sieve, MCM-22 mesoporous molecular sieve, MCM-48 mesoporous molecular sieve, or MCM-50 mesoporous molecular sieve. The MSU series is the MSU-1 mesoporous molecular sieve. The SBA series is one of the SBA-15 mesoporous molecular sieve or SBA-16 mesoporous molecular sieve. The preferred mesoporous molecular sieve is MCM-41.

[0018] In step (2), the mass ratio of mesoporous molecular sieve to deionized water is 1:1-3, preferably 1:2.

[0019] In step (2), the first metal salt solution is a solution obtained by mixing one or more of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, Zr(NO3)4·10H2O, Ce(NO3)3·6H2O, Mn(NO3)2·4H2O or Mg(NO3)2·6H2O with deionized water, and the concentration of the first metal salt solution is 0.1-5 mol / L.

[0020] Step (2) The first metal salt solution is added to the mixed solution of mesoporous molecular sieve and deionized water and stirred.

[0021] The metal loading in the metal oxide modified mesoporous molecular sieve catalyst in step (2) is 5-30 wt%, preferably 10 wt%.

[0022] In step (2), a constant temperature magnetic rotor stirrer is used to stir the mixture of mesoporous molecular sieve and deionized water with the first metal salt solution at 20-60℃ for 1-12h, then dry at 80-200℃ for 8-24h, and finally calcine at 500-800℃ for 4-12h to prepare a metal oxide modified mesoporous molecular sieve catalyst.

[0023] In step (2), the metal oxide modified mesoporous molecular sieve catalyst is prepared by the equal volume impregnation method.

[0024] The MOF mentioned in step (3) refers to one or more of the following: metal-organic mesh frameworks (IRMOFs), zeolite-like imidazolium ester frameworks (ZIFs), pore-channel frameworks (PCNs), or Lavasil frameworks (MILs).

[0025] Among them, the network metal-organic framework series materials (IRMOFs) are one of IRMOFs-1, IRMOFs-3, IRMOFs-6 or IRMOFs-8; the zeolite-like imidazole ester framework series materials (ZIFs) are one of ZIF-8, ZIF-11 or ZIF-67; the pore-channel framework series materials (PCNs) are one of PCN-9, PCN-14 or PCN-53; and the Lavasil framework series materials (MIL) are one of MIL-53, MIL-100 or MIL-101.

[0026] Preferably, the MOF mentioned in step (3) is ZIF-8.

[0027] In step (3), MOF is dispersed in deionized water, and the mass ratio of MOF to deionized water is 1:1-3, preferably 1:2.

[0028] In step (3), the second metal salt solution is a solution obtained by mixing any two of Ce(NO3)3, RuCl3, Co(NO3)2, Ni(NO3)2, Zr(NO3)4, Mn(NO3)2 or Mg(NO3)2 with deionized water, and the concentration of the second metal salt solution is 0.1-2 mol / L, preferably 0.5 mol / L.

[0029] In step (3), the two metal salt solutions in the second metal salt solution are added sequentially to the mixed solution of MOF and deionized water.

[0030] The metal loading in the bimetallic supported MOF-based catalyst described in step (3) is 5-30 wt%, with the loading of the two metals being the same, preferably 10 wt%.

[0031] In step (3), a constant temperature magnetic rotor stirrer is used to stir the mixture of MOF and deionized water with the second metal salt solution at 20-60℃ for 1-12h, then dry at 80-200℃ for 8-24h, and finally calcine at 500-800℃ for 4-12h to prepare a bimetallic supported MOF-based catalyst.

[0032] In step (4), the mass ratio of pretreated biomass to metal oxide modified mesoporous molecular sieve catalyst is 1:1-5, preferably 1:1.

[0033] The oxygen-free atmosphere mentioned in step (4) refers to one or more of nitrogen, argon, helium, CO2 or CO, with a gas flow rate of 100-200 mL / min, preferably 200 mL / min.

[0034] The staged pyrolysis described in step (4) involves setting multiple temperature ranges within the range of 20-800℃, preferably 20-250℃, 250-300℃, 300-400℃, and 400-600℃; the holding time for each temperature range is 3s-30min, preferably 15min; and the pyrolysis heating rate is 2-15℃ / min, preferably 10℃ / min.

[0035] In step (5), the second pyrolysis reactor is heated and kept at the same temperature as the first pyrolysis reactor in step (4). The pyrolysis temperature range, pyrolysis heating rate, holding time and gas flow rate of nitrogen-rich pyrolysis under ammonia conditions are consistent with the reaction conditions when the first aldehyde-ketone pyrolysis vapor is obtained in the first pyrolysis reactor in step (4).

[0036] The ammonia-containing condition mentioned in step (5) refers to a carrier gas of pure NH3 or a mixture of NH3 and other inert gases, wherein the other inert gas is either argon or nitrogen, preferably pure NH3.

[0037] In step (6), the mass of the bimetallic supported MOF-based catalyst is 1-5 times the mass of the pretreated biomass.

[0038] The catalytic reactor in step (6) is heated and kept at the same temperature as the first pyrolysis reactor in step (4). The temperature range, heating rate, holding time and gas flow rate of the ex-situ catalytic online aldehyde-ketone reaction are consistent with the reaction conditions when easily aldehyde-ketone pyrolysis steam is obtained in the first pyrolysis reactor in step (4).

[0039] The catalytic reactor described in step (6) is in an oxygen-free atmosphere, and the gas type is consistent with that in step (4).

[0040] The ammonia-containing condition mentioned in step (7) refers to a carrier gas of pure NH3 or a mixture of NH3 and other inert gases, wherein the other inert gas is either argon or nitrogen, preferably pure NH3.

[0041] In step (7), the third pyrolysis reactor is heated and kept at the same temperature as the first pyrolysis reactor in step (4). The pyrolysis temperature range, pyrolysis heating rate, holding time and gas flow rate of nitrogen-rich pyrolysis under ammonia conditions are consistent with the reaction conditions when easily aldehyde-ketalized pyrolysis vapor is obtained in the first pyrolysis reactor in step (4).

[0042] The condensing temperature of condenser tube 1 in step (5), condenser tube 2 in step (7), and condenser tube 3 in step (8) is -30 to -30 ℃.

[0043] Compared with the prior art, the present invention has the following advantages: (1) The production process for preparing pyridine-rich bio-oil from pretreated biomass via graded nitrogen-enriched pyrolysis as described in this invention involves graded nitrogen-enriched pyrolysis, which sets different pyrolysis reaction temperature ranges based on the pyrolysis characteristics of the three major components of biomass, and collecting different pyrolysis steams with relatively high component content step by step. Under nitrogen-enriched pyrolysis conditions, aldehyde- and ketone-rich pyrolysis steams are converted into pyridine-rich bio-oil. For pyrolysis steams with low aldehyde- and ketone content, online catalytic control is further used to convert easily aldehyde- and ketone-converted components into aldehydes and ketones, which are then subjected to nitrogen-enriched pyrolysis. Pyrolysis steams with higher content of components that are not easily aldehyde- and ketone-converted are used to prepare liquid fuels or other chemicals, realizing the graded and high-value utilization of all biomass components. Since pyrolysis products are released stepwise during graded nitrogen-enriched pyrolysis, the complexity of bio-oil components can be reduced. Furthermore, by selectively preparing aldehyde- and ketone-rich and easily aldehyde- and ketone-converted pyrolysis steams through process control, the pyrolysis components that are not easily aldehyde- and ketone-converted can be effectively separated, significantly improving the yield of pyridine compounds and their selectivity in graded pyrolysis bio-oil, which is beneficial for subsequent product separation and processing.

[0044] (2) The pre-treated biomass staged-nitrogen-enriched pyrolysis process for preparing pyridine-rich bio-oil described in this invention effectively removes impurities and inorganic salts from the biomass raw materials through acid washing, alkali washing, or oxidative pretreatment, thereby improving pyrolysis efficiency and product quality. Staged pyrolysis technology is employed, setting different temperature ranges based on the pyrolysis characteristics of the three major biomass components (cellulose, hemicellulose, and lignin), and collecting pyrolysis vapors with relatively high component content stage by stage. This method effectively reduces the complexity of bio-oil components, laying the foundation for subsequent targeted conversion and product separation.

[0045] (3) The production process for preparing pyridine-rich bio-oil by pre-treatment biomass grading-nitrogen-rich pyrolysis described in this invention, in the grading pyrolysis process, pyrolysis vapor rich in aldehydes and ketones is prepared by in-situ / ex-situ catalytic directional control. This graded and quality-separated treatment method not only significantly improves the yield and selectivity of pyridine compounds in bio-oil under nitrogen-rich pyrolysis conditions, but also realizes the high-value utilization of all components of biomass, avoiding the complex component separation steps in traditional processes.

[0046] (4) The pre-treated biomass fractionation-nitrogen-enriched pyrolysis process for preparing pyridine-rich bio-oil described in this invention uses a metal oxide-modified mesoporous molecular sieve catalyst for in-situ catalysis, which can effectively control the composition of the pyrolysis products. The introduction of metal oxides enhances the acidity and redox performance of the mesoporous molecular catalyst, which is beneficial to the efficient conversion of biomass. At the same time, this invention uses a bimetallic supported MOF-based catalyst for online catalytic control of easily aldehyde-ketone pyrolysis steam. MOF materials have a highly ordered structure, high specific surface area, and precisely customizable composition, showing great advantages in terms of chemical tunability, insolubility, and recyclability. The bimetallic support further improves the performance of the catalyst, which is beneficial to the efficient generation of aldehydes and ketones, and has strong stability, meeting the characteristics of high efficiency, low cost, and environmental protection, and has strong practicality. Detailed Implementation

[0047] The present invention will be further described below with reference to embodiments.

[0048] Example 1 The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis as described in Example 1 consists of the following steps: (1) Coconut shells were selected as raw materials. The coconut shells were crushed and screened to obtain coconut shell powder with a particle size of 40 mesh. Then, 10 g of coconut shell powder was added to a beaker containing 250 mL of acetic acid solution (concentration of 1 mol / L). The mixture was stirred at 20°C for 2 h using a constant temperature magnetic rotor stirrer. The pretreated raw material was repeatedly washed with deionized water until the pH value of the last filtered water was 7±0.03. The filter residue was then dried at 105°C for 24 h to obtain the pretreated coconut shell powder.

[0049] (2) Using the impregnation method, 20 g of MCM-41 mesoporous molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 40 g of deionized water, and Zr(NO3)4 solution with a concentration of 0.5 mol / L was added to make the metal loading 10 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of MCM-41 deionized water solution and Zr(NO3)4 solution was stirred at 40℃ for 6 h, then dried at 105℃ for 12 h, and finally calcined at 600℃ for 4 h to prepare ZrO2-MCM-41.

[0050] (3) Using the impregnation method, 20 g of ZIF-8 (purchased from Shanghai Kaishu Chemical Technology Co., Ltd.) was dispersed in 40 g of deionized water. Ce(NO3)3 solution with a concentration of 0.5 mol / L and RuCl3 solution with a concentration of 0.5 mol / L were added to 100 mL of deionized water. The Ce loading was 5 wt% and the Ru loading was 5 wt%. Using a constant temperature magnetic rotor stirrer, the deionized aqueous solution of ZIF-8 and the second metal salt solution were stirred at 40 °C for 6 h. Then, it was dried at 105 °C for 12 h and finally calcined at 600 °C for 4 h to obtain RuCe-ZIF-8.

[0051] (4) Mix 10 g of the pre-treated coconut shell powder prepared in step (1) with 10 g of ZrO2-MCM-41 prepared in step (2) and add it into the first pyrolysis reactor. Perform staged pyrolysis under Ar atmosphere. The gas flow rate is 100 mL / min. The staged pyrolysis temperatures are 300℃, 400℃ and 600℃ respectively. The heating rate is 10℃ / min. Each stage is held for 15 min. The first aldehyde- and ketone-rich pyrolysis steam is obtained in the 20-300℃ range. The easily aldehyde- and ketone-forming pyrolysis steam is obtained in the 300-400℃ range. The difficult aldehyde- and ketone-forming pyrolysis steam is obtained in the 400-600℃ range.

[0052] (5) The second pyrolysis reactor, the third pyrolysis reactor, and the catalytic reactor are heated and kept at the same temperature as the first pyrolysis reactor. Within the temperature range of 20-300℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (4) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a pure NH3 atmosphere. The gas flow rate is 100 mL / min, and the volatiles are introduced into the No. 1 condenser and condensed at -10℃ to obtain the first pyridine-rich bio-oil.

[0053] (6) In the temperature range of 300-400 ℃, the pyrolysis vapor generated in step (4) is first introduced into a catalytic reactor carrying 10 g RuCe-ZIF-8 catalyst, and the extrinsic catalytic online aldehyde-ketone reaction is carried out under Ar atmosphere. The gas flow rate is 100 mL / min, and the second aldehyde-ketone rich pyrolysis vapor is obtained.

[0054] (7) In the temperature range of 300-400 ℃, the second aldehyde-ketone pyrolysis vapor obtained in step (6) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under pure NH3 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -10 ℃ to obtain the second pyridine-rich bio-oil.

[0055] (8) In the temperature range of 400-600 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) is passed into condenser tube No. 3 and condensed at -10 ℃ to obtain bio-oil.

[0056] Example 2 The production process for preparing pyridine-rich bio-oil from pretreated biomass grading-nitrogen-enriched pyrolysis as described in Example 2 consists of the following steps: (1) Cotton stalks were selected as raw materials. The cotton stalks were crushed and screened to obtain cotton stalk powder with a particle size of 60 mesh. Then, 10 g of cotton stalk powder was added to a beaker containing 300 mL of formic acid solution (concentration of 1 mol / L). The mixture was stirred at 30 °C for 4 h using a constant temperature magnetic rotor stirrer. The pretreated raw material was repeatedly washed with deionized water until the pH value of the last filtered water was 7 ± 0.03. The filter residue was then dried at 105 °C for 12 h to obtain the acid-washed pretreated cotton stalks.

[0057] (2) Using the impregnation method, 15 g of SBA-15 mesoporous molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 45 g of deionized water, and a Co (NO3)2 solution with a concentration of 0.3 mol / L was added to make the metal loading 10 wt%. Using a constant temperature magnetic rotor stirrer, the deionized water solution of SBA-15 mesoporous molecular sieve and the Co (NO3)2 solution were stirred at 40 °C for 6 h, then dried at 105 °C for 12 h, and finally calcined at 600 °C for 4 h to prepare Co3O4-SBA-15.

[0058] (3) Using the impregnation method, 15 g of ZIF-11 (purchased from Shanghai Kaishu Chemical Technology Co., Ltd.) was dispersed in 45 g of deionized water. Ni (NO3)2 solution with a concentration of 0.5 mol / L and Mg (NO3)2 solution with a concentration of 0.5 mol / L were added to 100 mL of deionized water. The Ni loading was 8 wt% and the Mg loading was 8 wt%. The mixture of ZIF-8 solution and second metal salt solution was stirred at 40 °C for 6 h using a constant temperature magnetic rotor stirrer. Then it was dried at 105 °C for 12 h and finally calcined at 550 °C for 6 h to obtain NiMg-ZIF-11.

[0059] (4) Mix 5 g of the pre-treated cotton stalks prepared in step (1) with 10 g of the Co3O4-SBA-15 prepared in step (2) and add it into the first pyrolysis reactor. Perform staged pyrolysis under CO2 atmosphere. The gas flow rate is 100 mL / min. The staged pyrolysis temperatures are 300 ℃, 400 ℃ and 600 ℃, respectively. The heating rate is 12 ℃ / min. Each stage is held for 20 min. Pyrolysis steam that is not easily aldehyde-ketone pyrolysis is obtained in the temperature range of 20-300℃. First aldehyde-ketone rich pyrolysis steam is obtained in the temperature range of 300-400℃. Pyrolysis steam that is easily aldehyde-ketone pyrolysis is obtained in the temperature range of 400-600℃.

[0060] (5) In the temperature range of 20-300℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) is passed into condenser tube No. 3 and condensed at -10℃ to obtain bio-oil.

[0061] (6) The second pyrolysis reactor, the third pyrolysis reactor, and the catalytic reactor are heated and kept at the same temperature as the first pyrolysis reactor. Within the temperature range of 300-400℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (4) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a pure NH3 atmosphere. The gas flow rate is 100 mL / min, and the volatiles are introduced into the No. 1 condenser and condensed at -10℃ to obtain the first pyridine-rich bio-oil.

[0062] (7) In the temperature range of 400-600 ℃, the pyrolysis steam generated in step (4) is first introduced into a catalytic reactor carrying 10 g NiMg-ZIF-11 catalyst, and the extrinsic catalytic online aldehyde-ketone reaction is carried out under CO2 atmosphere with a gas flow rate of 100 mL / min to obtain the second aldehyde-ketone rich pyrolysis steam.

[0063] (8) In the temperature range of 400-600℃, the second aldehyde-ketone pyrolysis vapor obtained in step (7) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under pure NH3 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -10℃ to obtain the second pyridine-rich bio-oil.

[0064] Example 3 The process for preparing pyridine compounds by pretreatment biomass fractionation-nitrogen-enriched pyrolysis as described in Example 3 consists of the following steps: (1) Pine wood was selected as raw material. The pine wood was crushed and screened to obtain pine wood powder with a particle size of 100 mesh. Then, 10 g of pine wood powder was added to a beaker containing 400 mL of H2O2 solution (concentration of 3 mol / L). The mixture was stirred at 25°C for 2 h using a constant temperature magnetic rotor stirrer. The pretreated raw material was repeatedly washed with deionized water until the pH value of the last filtered water was 7±0.03. The filter residue was then dried at 120°C for 24 h to obtain oxidized pretreated pine wood powder.

[0065] (2) Using the impregnation method, 30 g of MCM-22 mesoporous molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 80 g of deionized water, and Mg(NO3)2 solution with a concentration of 0.5 mol / L was added to make the metal loading 5 wt%. Using a constant temperature magnetic rotor stirrer, the mixed solution of MCM-22 mesoporous molecular sieve deionized water and Mg(NO3)2 was stirred at 40℃ for 6 h, then dried at 105℃ for 12 h, and finally calcined at 600℃ for 4 h to prepare MgO-MCM-22.

[0066] (3) Using the impregnation method, 30 g of MIL-101 (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 60 g of deionized water. Ni (NO3)2 solution with a concentration of 1.5 mol / L and Co (NO3)2 solution with a concentration of 1.5 mol / L were added to 100 mL of deionized water. The Ni loading was 10 wt% and the Co loading was 10 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of MIL-101 deionized water solution and metal salt solution was stirred at 30 °C for 8 h. Then it was dried at 105 °C for 24 h and calcined at 650 °C for 4 h to obtain CoNi-MIL-101.

[0067] (4) Mix 15 g of the oxidized pretreated pine powder prepared in step (1) with 15 g of MgO-MCM-22 prepared in step (2) and add it into the first pyrolysis reactor. Perform staged pyrolysis under N2 atmosphere. The gas flow rate is 100 mL / min. The staged pyrolysis temperatures are 250℃, 400℃ and 600℃, respectively. The heating rate is 5℃ / min. Each stage is held for 25 min. The first aldehyde- and ketone-rich pyrolysis steam is obtained in the temperature range of 20-250℃. The easily aldehyde- and ketone-forming pyrolysis steam is obtained in the temperature range of 250-400℃. The difficult aldehyde- and ketone-forming pyrolysis steam is obtained in the temperature range of 400-600℃.

[0068] (5) The second pyrolysis reactor, the third pyrolysis reactor, and the catalytic reactor are heated and kept at the same temperature as the first pyrolysis reactor. Within the temperature range of 20-250℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (4) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a 5 voL% NH3 / 95 voL% N2 atmosphere. The gas flow rate is 100 mL / min, and the volatiles are introduced into the No. 1 condenser and condensed at -20℃ to obtain the first pyridine-rich bio-oil.

[0069] (6) In the temperature range of 250-400 ℃, the pyrolysis steam generated in step (4) is first introduced into a catalytic reactor carrying 15 g CoNi-MIL-101 catalyst, and the extrinsic catalytic online aldehyde-ketone reaction is carried out under CO2 atmosphere with a gas flow rate of 100 mL / min to obtain the second aldehyde-ketone rich pyrolysis steam.

[0070] (7) In the temperature range of 250-400℃, the second aldehyde-ketone pyrolysis vapor obtained in step (6) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a 5 voL% NH3 / 95 voL% N2 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -20℃ to obtain the second pyridine-rich bio-oil.

[0071] (8) In the temperature range of 400-600 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) is passed into condenser tube No. 3 and condensed at -20 ℃ to obtain bio-oil.

[0072] Example 4 The production process for preparing pyridine-rich bio-oil from pretreated biomass grading-nitrogen-enriched pyrolysis as described in Example 4 consists of the following steps: (1) Grapefruit peel was selected as raw material. The grapefruit peel was crushed and screened to obtain grapefruit peel powder with a particle size of 40 mesh. Then, 20 g of grapefruit peel powder was added to a beaker containing 500 mL of NaOH solution (concentration of 2.5 mol / L). The mixture was stirred at 20℃ for 4 h using a constant temperature magnetic rotor stirrer. The pretreated raw material was repeatedly washed with deionized water until the pH value of the last filtered water was 7±0.03. The filter residue was then dried at 105℃ for 24 h to obtain the alkali-washed pretreated grapefruit peel powder.

[0073] (2) Using the impregnation method, 15 g of MSU-1 mesoporous molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 30 g of deionized water, and Ni (NO3)2 solution with a concentration of 1.5 mol / L was added to make the metal loading 20 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of MSU-1 deionized water solution and Ni (NO3)2 solution was stirred at 40℃ for 6 h, then dried at 105 ℃ for 12 h, and finally calcined at 600 ℃ for 4 h to prepare NiO-MSU-1.

[0074] (3) Using the impregnation method, 15g of ZIF-8 (purchased from Shanghai Kaishu Chemical Technology Co., Ltd.) was dispersed in 45g of deionized water. A Zr(NO3)4 solution with a concentration of 0.5 mol / L and a Mg(NO3)2 solution with a concentration of 0.5 mol / L were added to 100 mL of deionized water. The Zr loading was 6wt% and the Mg loading was 6wt%. Using a constant temperature magnetic rotor stirrer, the mixture of the deionized water solution of ZIF-8 and the metal salt solution was stirred at 40℃ for 6 h. Then it was dried at 105℃ for 12 h and calcined at 500℃ for 4 h to obtain ZrMg-ZIF-8.

[0075] (4) Mix 8 g of the alkali-washed pretreated grapefruit peel powder prepared in step (1) with 16 g of NiO-MSU-1 prepared in step (2) and add it into the first pyrolysis reactor. Perform staged pyrolysis under Ar atmosphere. The gas flow rate is 120 mL / min. The staged pyrolysis temperatures are 250 ℃, 350 ℃ and 550 ℃, respectively. The heating rate is 7.5 ℃ / min. Each stage is held for 30 min. The first aldehyde- and ketone-rich pyrolysis steam is obtained in the temperature range of 20-250℃. The easily aldehyde- and ketone-forming pyrolysis steam is obtained in the temperature range of 250-350℃. The difficult aldehyde- and ketone-forming pyrolysis steam is obtained in the temperature range of 350-550℃.

[0076] (5) The second pyrolysis reactor, the third pyrolysis reactor, and the catalytic reactor are heated and kept at the same temperature as the first pyrolysis reactor. Within the temperature range of 20-250℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (4) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a 10 voL% NH3 / 90 voL% N2 atmosphere. The gas flow rate is 120 mL / min, and the volatiles are introduced into the No. 1 condenser and condensed at -15℃ to obtain the first pyridine-rich bio-oil.

[0077] (6) In the temperature range of 250-350 ℃, the pyrolysis vapor of easy aldehyde-ketone conversion generated in step (4) is first introduced into a catalytic reactor carrying 16 g ZrMg-ZIF-8 catalyst, and the extrinsic catalytic online aldehyde-ketone conversion reaction is carried out under Ar atmosphere. The gas flow rate is 100 mL / min, and the second aldehyde-ketone rich pyrolysis vapor is obtained.

[0078] (7) In the temperature range of 250-350℃, the second aldehyde-ketone pyrolysis vapor obtained in step (6) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a 10 voL% NH3 / 90 voL% N2 atmosphere. The gas flow rate is 120 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -15℃ to obtain the second pyridine-rich bio-oil.

[0079] (8) In the temperature range of 350-550 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) is passed into condenser tube No. 3 and condensed at -15 ℃ to obtain bio-oil.

[0080] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the coconut shell powder is not pretreated with acid washing. The steps are as follows: (1) Coconut shells are selected as raw materials, and the coconut shells are crushed and screened to obtain coconut shell powder with a particle size of 40 mesh.

[0081] (2) Using the impregnation method, 20 g of MCM-41 mesoporous molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 40 g of deionized water, and a Zr(NO3)4 solution with a concentration of 0.5 mol / L was added to make the metal loading 10 wt%. The mixed solution of MCM-41 and Zr(NO3)4 was stirred at 40 ℃ for 6 h using a constant temperature magnetic rotor stirrer, then dried at 105 ℃ for 12 h, and calcined at 600 ℃ for 4 h to prepare ZrO2-MCM-41.

[0082] (3) Using the impregnation method, 20 g of ZIF-8 (purchased from Shanghai Kaishu Chemical Technology Co., Ltd.) was dispersed in 40 g of deionized water. Ce(NO3)3 solution with a concentration of 0.5 mol / L and RuCl3 solution with a concentration of 0.5 mol / L were added to 100 mL of deionized water. The Ce loading was 5 wt% and the Ru loading was 5 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of ZIF-8 and deionized water and the second metal salt solution were stirred at 40 °C for 6 h. Then, it was dried at 105 °C for 12 h and calcined at 600 °C for 4 h to obtain RuCe-ZIF-8.

[0083] (4) Mix 10 g of the pre-treated coconut shell powder prepared in step (1) with 10 g of ZrO2-MCM-41 prepared in step (2) and add it into the first pyrolysis reactor. Perform staged pyrolysis under Ar atmosphere. The gas flow rate is 100 mL / min. The staged pyrolysis temperatures are 300℃, 400℃ and 600℃ respectively. The heating rate is 10℃ / min. Each stage is held for 15 min. The first aldehyde- and ketone-rich pyrolysis steam is obtained in the 20-300℃ range. The easily aldehyde- and ketone-forming pyrolysis steam is obtained in the 300-400℃ range. The difficult aldehyde- and ketone-forming pyrolysis steam is obtained in the 400-600℃ range.

[0084] (5) The second pyrolysis reactor, the third pyrolysis reactor, and the catalytic reactor are heated and kept at the same temperature as the first pyrolysis reactor. Within the temperature range of 20-300℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (4) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a pure NH3 atmosphere. The gas flow rate is 100 mL / min, and the volatiles are introduced into the No. 1 condenser and condensed at -10℃ to obtain the first pyridine-rich bio-oil.

[0085] (6) In the temperature range of 300-400 ℃, the pyrolysis vapor generated in step (4) is first introduced into a catalytic reactor carrying 10 g RuCe-ZIF-8 catalyst, and the extrinsic catalytic online aldehyde-ketone reaction is carried out under Ar atmosphere. The gas flow rate is 100 mL / min, and the second aldehyde-ketone rich pyrolysis vapor is obtained.

[0086] (7) In the temperature range of 300-400 ℃, the second aldehyde-ketone pyrolysis vapor obtained in step (6) is introduced into the second-stage pyrolysis reactor and nitrogen-rich pyrolysis is carried out under pure NH3 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -10 ℃ to obtain the second pyridine-rich bio-oil.

[0087] (8) In the temperature range of 400-600 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) is passed into condenser tube No. 3 and condensed at -10 ℃ to obtain bio-oil.

[0088] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that in-situ catalysis is not performed in the staged pyrolysis. The steps are as follows: (1) Coconut shells were selected as raw materials. The coconut shells were crushed and screened to obtain coconut shell powder with a particle size of 40 mesh. Then, 10 g of coconut shell powder was added to a beaker containing 250 mL of acetic acid solution (concentration of 1 mol / L). The mixture was stirred at 20°C for 2 h using a constant temperature magnetic rotor stirrer. The pretreated raw material was repeatedly washed with deionized water until the pH value of the last filtered water was 7±0.03. The filter residue was then dried at 105°C for 24 h to obtain the pretreated coconut shell powder.

[0089] (2) Using the impregnation method, 20 g of ZIF-8 (purchased from Shanghai Kaishu Chemical Technology Co., Ltd.) was dispersed in 40 g of deionized water. Ce(NO3)3 solution with a concentration of 0.5 mol / L and RuCl3 solution with a concentration of 0.5 mol / L were added to 100 mL of deionized water. The Ce loading was 5 wt% and the Ru loading was 5 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of ZIF-8 and deionized water and the second metal salt solution were stirred at 40 °C for 6 h. Then, it was dried at 105 °C for 12 h and calcined at 600 °C for 4 h to obtain RuCe-ZIF-8.

[0090] (3) Weigh 10 g of the pre-treated coconut shell powder prepared in step (1) and add it to the first pyrolysis reactor. The pyrolysis is carried out in stages under Ar atmosphere. The gas flow rate is 100 mL / min. The stages of pyrolysis are 300 ℃, 400 ℃ and 600 ℃ respectively. The heating rate is 10 ℃ / min. Each stage is kept at the temperature for 15 min. The first aldehyde-ketone rich pyrolysis steam is obtained in the 20-300℃ range, the easily aldehyde-ketone pyrolysis steam is obtained in the 300-400℃ range, and the difficult aldehyde-ketone pyrolysis steam is obtained in the 400-600℃ range.

[0091] (4) The second pyrolysis reactor, the third pyrolysis reactor, and the catalytic reactor are heated and kept at the same temperature as the first pyrolysis reactor. Within the temperature range of 20-300℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (3) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a pure NH3 atmosphere. The gas flow rate is 100 mL / min, and the volatiles are introduced into the No. 1 condenser and condensed at -10℃ to obtain the first pyridine-rich bio-oil.

[0092] (5) In the temperature range of 300-400 ℃, the pyrolysis vapor generated in step (3) is first introduced into a catalytic reactor carrying 10 g RuCe-ZIF-8 catalyst, and the extrinsic catalytic online aldehyde-ketone reaction is carried out under Ar atmosphere. The gas flow rate is 100 mL / min, and the second aldehyde-ketone rich pyrolysis vapor is obtained.

[0093] (6) In the temperature range of 300-400 ℃, the second aldehyde-ketone pyrolysis vapor obtained in step (5) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under pure NH3 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -10 ℃ to obtain the second pyridine-rich bio-oil.

[0094] (7) In the temperature range of 400-600 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (3) is passed into condenser tube No. 3 and condensed at -10 ℃ to obtain bio-oil.

[0095] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the easily aldehyde-ketalized pyrolysis vapors are not subjected to ex-situ catalysis. The steps are as follows: (1) Coconut shells were selected as raw materials. The coconut shells were crushed and screened to obtain coconut shell powder with a particle size of 40 mesh. Then, 10 g of coconut shell powder was added to a beaker containing 250 mL of acetic acid solution (concentration of 1 mol / L). The mixture was stirred at 20°C for 2 h using a constant temperature magnetic rotor stirrer. The pretreated raw material was repeatedly washed with deionized water until the pH value of the last filtered water was 7±0.03. The filter residue was then dried at 105°C for 24 h to obtain the pretreated coconut shell powder.

[0096] (2) Using the impregnation method, 20 g of MCM-41 mesoporous molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 40 g of deionized water, and Zr(NO3)4 solution with a concentration of 0.5 mol / L was added to make the metal loading 10 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of MCM-41 deionized water solution and Zr(NO3)4 solution was stirred at 40℃ for 6 h, then dried at 105℃ for 12 h, and calcined at 600℃ for 4 h to prepare ZrO2-MCM-41.

[0097] (3) Mix 10 g of the pre-treated coconut shell powder prepared in step (1) with 10 g of ZrO2-MCM-41 prepared in step (2) and add it into the first pyrolysis reactor. Perform staged pyrolysis under Ar atmosphere. The gas flow rate is 100 mL / min. The staged pyrolysis temperatures are 300 ℃, 400 ℃ and 600 ℃, respectively. The heating rate is 10 ℃ / min. Each stage is held for 15 min. The first aldehyde- and ketone-rich pyrolysis steam is obtained in the 20-300℃ range. The easily aldehyde- and ketone-forming pyrolysis steam is obtained in the 300-400℃ range. The difficult aldehyde- and ketone-forming pyrolysis steam is obtained in the 400-600℃ range.

[0098] (4) The second pyrolysis reactor, the third pyrolysis reactor and the first pyrolysis reactor are heated and kept at the same temperature. In the temperature range of 20-300 ℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (3) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out in a pure NH3 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 1 condenser and condensed at -10 ℃ to obtain pyridine-rich bio-oil.

[0099] (5) In the temperature range of 300-400 ℃, the pyrolysis vapor generated in step (3) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under pure NH3 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -10 ℃ to obtain the first bio-oil (this bio-oil is a nitrogen-rich bio-oil).

[0100] (6) In the temperature range of 400-600 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (3) is passed into condenser tube No. 3 and condensed at -10 ℃ to obtain the second bio-oil.

[0101] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that nitrogen-rich pyrolysis is not performed. The steps are as follows: (1) Coconut shells were selected as raw materials. The coconut shells were crushed and screened to obtain coconut shell powder with a particle size of 40 mesh. Then, 10 g of coconut shell powder was added to a beaker containing 250 mL of acetic acid solution (concentration of 1 mol / L). The mixture was stirred at 20°C for 2 h using a constant temperature magnetic rotor stirrer. The pretreated raw material was repeatedly washed with deionized water until the pH value of the last filtered water was 7±0.03. The filter residue was then dried at 105°C for 24 h to obtain the pretreated coconut shell powder.

[0102] (2) Using the impregnation method, 20 g of MCM-41 mesoporous molecular sieve (purchased from Tianjin Nanhua Catalyst Co., Ltd.) was dispersed in 40 g of deionized water, and Zr(NO3)4 solution with a concentration of 0.5 mol / L was added to make the metal loading 10 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of MCM-41 deionized water solution and Zr(NO3)4 solution was stirred at 40℃ for 6 h, then dried at 105℃ for 12 h, and finally calcined at 600℃ for 4 h to prepare ZrO2-MCM-41.

[0103] (3) Using the impregnation method, 20 g of ZIF-8 (purchased from Shanghai Kaishu Chemical Technology Co., Ltd.) was dispersed in 40 g of deionized water. Ce(NO3)3 solution with a concentration of 0.5 mol / L and RuCl3 solution with a concentration of 0.5 mol / L were added to 100 mL of deionized water. The Ce loading was 5 wt% and the Ru loading was 5 wt%. Using a constant temperature magnetic rotor stirrer, the mixture of ZIF-8 and deionized water and the second metal salt solution were stirred at 40 °C for 6 h. Then, it was dried at 105 °C for 12 h and calcined at 600 °C for 4 h to obtain RuCe-ZIF-8.

[0104] (4) Mix 10 g of the pre-treated coconut shell powder prepared in step (1) with 10 g of ZrO2-MCM-41 prepared in step (2) and add it into the first pyrolysis reactor. Perform staged pyrolysis under Ar atmosphere. The gas flow rate is 100 mL / min. The staged pyrolysis temperatures are 300 ℃, 400 ℃ and 600 ℃, respectively. The heating rate is 10 ℃ / min. Each stage is held for 15 min. The first aldehyde-ketone rich pyrolysis steam is obtained in the temperature range of 20-300℃. The easily aldehyde-ketone pyrolysis steam is obtained in the temperature range of 300-400℃. The difficult aldehyde-ketone pyrolysis steam is obtained in the temperature range of 400-600℃.

[0105] (5) In the temperature range of 20-300 ℃, the first aldehyde-rich ketone pyrolysis vapor obtained in step (4) is passed into condenser tube No. 1 and condensed at -10 ℃ to obtain the first bio-oil.

[0106] (6) The catalytic reactor and the first pyrolysis reactor are heated and kept at the same temperature. Within the temperature range of 300-400 ℃, the pyrolysis vapor generated in step (4) is introduced into the catalytic reactor carrying 10 g RuCe-ZIF-8 catalyst, and the extrinsic catalytic online aldehyde-ketone reaction is carried out under Ar atmosphere. The gas flow rate is 100 mL / min, and the second aldehyde-ketone rich pyrolysis vapor is obtained.

[0107] (7) In the temperature range of 300-400℃, the second aldehyde-rich ketone pyrolysis vapor obtained in step (6) is passed into condenser tube No. 2 and condensed at -10℃ to obtain the second bio-oil.

[0108] (8) In the temperature range of 400-600 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) is passed into condenser tube No. 3 and condensed at -10 ℃ to obtain the third bio-oil.

[0109] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the coconut shell powder is not pretreated with acid washing, and no catalyst is added. The steps are as follows: (1) Coconut shells are selected as raw materials, and the coconut shells are crushed and screened to obtain coconut shell powder with a particle size of 40 mesh.

[0110] (2) Weigh 10g of the coconut shell powder prepared in step (1) and add it to the first pyrolysis reactor. Under Ar atmosphere, the pyrolysis is carried out in stages with a gas flow rate of 100 mL / min. The stage pyrolysis temperatures are 300 ℃, 400 ℃ and 600 ℃, respectively. The heating rate is 10 ℃ / min. Each stage is held for 15 min. The first aldehyde-ketone rich pyrolysis steam is obtained in the temperature range of 20-300℃, the easily aldehyde-ketone pyrolysis steam is obtained in the temperature range of 300-400℃, and the difficult aldehyde-ketone pyrolysis steam is obtained in the temperature range of 400-600℃.

[0111] (3) The second and third pyrolysis reactors are heated and kept at the same temperature as the first pyrolysis reactor. Within the temperature range of 20-300 ℃, the first aldehyde- and ketone-rich pyrolysis vapor obtained in step (2) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under a pure NH3 atmosphere. The gas flow rate is 100 mL / min, and the volatiles are introduced into the No. 1 condenser tube and condensed at -10 ℃ to obtain the first pyridine-rich bio-oil.

[0112] (4) In the temperature range of 300-400℃, the pyrolysis vapor generated in step (2) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under pure NH3 atmosphere. The gas flow rate is 100 mL / min. The volatiles are introduced into the No. 2 condenser and condensed at -10℃ to obtain the first bio-oil.

[0113] (5) In the temperature range of 400-600 ℃, the pyrolysis vapor that is not easily aldehyde-ketalized in step (2) is passed into condenser tube No. 3 and condensed at -10 ℃ to obtain the second bio-oil.

[0114] The component content of the bio-oils obtained in Examples 1-4 and Comparative Examples 1-5 was detected using gas chromatography-mass spectrometry, and the results are shown in Table 1.

[0115] Table 1 Distribution of bio-oil components

[0116] Examples 1-4 and Comparative Examples 1-5 show that the pretreated biomass fractionation-nitrogen-enriched pyrolysis process significantly improves the distribution of pyridine compounds in bio-oil. The specific reasons are as follows: (1) Acid washing / alkali washing / oxidation pretreatment significantly reduced the content of alkali metals and alkaline earth metals, and promoted the generation of ketones and dehydrated sugars by destroying the chemical cross-linking of cellulose and lignin. Under nitrogen-rich conditions, it promoted the generation of pyridines, amines and imidazoles, and reduced the complexity of bio-oils.

[0117] (2) In the process of staged pyrolysis, a mesoporous molecular sieve catalyst modified with metal oxide is added for in-situ catalysis. The direct contact between the catalyst and biomass enhances heat transfer and promotes the thermal decomposition of biomass. The metal oxide significantly promotes the conversion of biomass (especially cellulose and hemicellulose components) into small molecule carbonyl compounds.

[0118] (3) Adding a bimetallic supported MOF-based catalyst to the directional aldehyde-ketal conversion process allows for more precise control of the conversion of easily aldehyde-ketalized components such as dehydrated sugars, acids, and alcohols into aldehyde-ketal components, thereby improving the selectivity of the target product and reducing the impact of raw materials on catalyst carbon deposition and deactivation.

[0119] (4) An anaerobic atmosphere can alter the decomposition pathways of certain oxygen-containing compounds in bio-oils, promoting the formation of ketones, esters, and sugars, thus providing sufficient intermediates for pyridine compounds. Under nitrogen-rich conditions, aldehyde- and ketone-rich components react with NH3 to form pyridine compounds via the Maillard reaction; the higher the NH3 concentration, the higher the selectivity of pyridine compounds. Changing the pyrolysis atmosphere can also improve the distribution of aldehyde- and ketone components and pyridines.

Claims

1. A production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis, characterized in that: It consists of the following steps: (1) First, the biomass is crushed and screened to obtain biomass powder. Then, the biomass powder is added to a washing solution for pretreatment. After filtration, washing and drying, pretreated biomass is obtained. (2) Disperse the mesoporous molecular sieve in deionized water, then add the first metal salt solution, and after stirring, drying and calcining, prepare the metal oxide modified mesoporous molecular sieve catalyst. The first metal salt solution is a solution obtained by mixing one or more of Co (NO3)2, Ni (NO3)2, Zr (NO3)4, Ce (NO3)3, Mn (NO3)2 or Mg (NO3)2 with deionized water. (3) Disperse MOF in deionized water, then add a second metal salt solution, stir, dry and calcine to prepare a bimetallic supported MOF-based catalyst. The second metal salt solution is any two of Ce(NO3)3, RuCl3, Co(NO3)2, Ni(NO3)2, Zr(NO3)4, Mn(NO3)2 or Mg(NO3)2 mixed with deionized water. (4) After the pretreated biomass prepared in step (1) is mixed evenly with the metal oxide modified mesoporous molecular sieve catalyst prepared in step (2), it is added to the first pyrolysis reactor and subjected to staged pyrolysis under an oxygen-free atmosphere to obtain the first aldehyde- and ketone-rich pyrolysis steam, the aldehyde- and ketone-easily pyrolysis steam and the aldehyde- and ketone-easily pyrolysis steam in different temperature ranges. (5) The first aldehyde- and ketone-rich pyrolysis vapor from step (4) is introduced into the second pyrolysis reactor and nitrogen-rich pyrolysis is carried out under ammonia conditions. The volatiles are introduced into the No. 1 condenser and condensed to obtain the first pyridine-rich bio-oil. (6) The pyrolysis steam that is easily aldehyde-ketone converted in step (4) is passed into a catalytic reactor carrying the bimetallic supported MOF-based catalyst prepared in step (3) to carry out an ex-situ catalytic online aldehyde-ketone conversion reaction of the pyrolysis steam to obtain a second aldehyde-ketone rich pyrolysis steam. (7) The second aldehyde- and ketone-rich pyrolysis vapor from step (6) is introduced into the third pyrolysis reactor and nitrogen-rich pyrolysis is carried out under ammonia conditions. The volatiles are introduced into the No. 2 condenser and condensed to obtain the second pyridine-rich bio-oil. (8) Pass the pyrolysis vapor that is not easily aldehyde-ketalized in step (4) into condenser tube No. 3 and condense to obtain bio-oil.

2. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: The biomass mentioned in step (1) refers to one or a mixture of several of the following: wood, crop straw, fruit shells, leaves, bark, or food processing residues; The wood is one or more of pine, poplar, or camphor; the crop straw is one or more of corn stalks, cotton stalks, or wheat stalks; and the fruit shell is one or more of coconut shells, grapefruit peel, or walnut shells. In step (1), the particle size of the biomass powder is 40-100 mesh.

3. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: The washing solution mentioned in step (1) is one of an acidic solution, an alkaline solution, or an oxidizing solution. The acidic solution is a mixture of acetic acid, formic acid, oxalic acid, or propionic acid with deionized water, and the concentration of the acidic solution is 1-10 mol / L. The alkaline solution is a sodium hydroxide solution with a concentration of 1-10 mol / L. The oxidizing solution is a hydrogen peroxide solution with a concentration of 1-10 mol / L. In step (1), the mass-to-volume ratio of biomass powder to washing solution is 1:25-75, with units of g / mL; In step (1), the biomass powder is immersed in the prepared washing solution and pretreated by stirring at 20-40℃ for 1-5 hours using a constant temperature magnetic rotor stirrer. The pretreated raw material is repeatedly washed with deionized water until the pH value of the last filtered water is 7±0.

03. Then the filter residue is dried at 80-200℃ for 8-48 hours to obtain pretreated biomass.

4. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: The mesoporous molecular sieve mentioned in step (2) refers to one or more of the M41S series, MSU series or SBA series. The M41S series is one of MCM-41 mesoporous molecular sieve, MCM-48 mesoporous molecular sieve or MCM-50 mesoporous molecular sieve. The MSU series is MSU-1 mesoporous molecular sieve. The SBA series is one of SBA-15 mesoporous molecular sieve or SBA-16 mesoporous molecular sieve. Step (2) The mass ratio of mesoporous molecular sieve to deionized water is 1:1-3; In step (2), the concentration of the first metal salt solution is 0.1-5 mol / L; The metal loading in the metal oxide-modified mesoporous molecular sieve catalyst described in step (2) is 5-30 wt%. In step (2), a constant temperature magnetic rotor stirrer is used to stir the mixture of mesoporous molecular sieve and deionized water with the first metal salt solution at 20-60℃ for 1-12h, then dry at 80-200℃ for 8-24h, and finally calcine at 500-800℃ for 4-12h to prepare a metal oxide modified mesoporous molecular sieve catalyst.

5. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: The MOF mentioned in step (3) refers to one or more of the following: network metal-organic framework materials, zeolite-like imidazolium ester framework materials, pore-channel framework materials, or Lavasil framework materials; Among them, the network metal-organic framework series materials are one of IRMOFs-1, IRMOFs-3, IRMOFs-6 or IRMOFs-8; the zeolite-like imidazolium ester framework series materials are one of ZIF-8, ZIF-11 or ZIF-67; the pore-channel framework series materials are one of PCN-9, PCN-14 or PCN-53; and the Lavasil framework series materials are one of MIL-53, MIL-100 or MIL-101. In step (3), MOF is dispersed in deionized water, and the mass ratio of MOF to deionized water is 1:1-3.

6. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: In step (3), the concentration of the second metal salt solution is 0.1-2 mol / L; The metal loading in the bimetallic supported MOF-based catalyst described in step (3) is 5-30 wt%, and the loading of the two metals is the same; In step (3), a constant temperature magnetic rotor stirrer is used to stir the mixture of MOF and deionized water with the second metal salt solution at 20-60℃ for 1-12h, then dry at 80-200℃ for 8-24h, and finally calcine at 500-800℃ for 4-12h to prepare a bimetallic supported MOF-based catalyst.

7. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: In step (4), the mass ratio of pretreated biomass to metal oxide modified mesoporous molecular sieve catalyst is 1:1-5; The oxygen-free atmosphere mentioned in step (4) refers to one or more of nitrogen, argon, helium, CO2 or CO, with a gas flow rate of 100-200 mL / min; The staged pyrolysis described in step (4) involves setting multiple temperature ranges within the range of 20-800℃, with each temperature range having a holding time of 3s-30min and a pyrolysis heating rate of 2-15℃ / min.

8. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: In step (5), the second pyrolysis reactor is heated and kept at the same temperature as the first pyrolysis reactor in step (4). The pyrolysis temperature range, pyrolysis heating rate, holding time and gas flow rate of nitrogen-rich pyrolysis under ammonia conditions are consistent with the reaction conditions when the first aldehyde-ketone pyrolysis vapor is obtained in the first pyrolysis reactor in step (4). The ammonia-containing condition mentioned in step (5) refers to the carrier gas being pure NH3 or a mixture of NH3 and other inert gases, where the other inert gas is either argon or nitrogen. In step (6), the mass of the bimetallic supported MOF-based catalyst is 1-5 times the mass of the pretreated biomass; The catalytic reactor in step (6) is heated and kept at the same temperature as the first pyrolysis reactor in step (4). The temperature range, heating rate, holding time and gas flow rate of the ex-situ catalytic online aldehyde-ketone reaction are consistent with the reaction conditions when easily aldehyde-ketone pyrolysis steam is obtained in the first pyrolysis reactor in step (4). The catalytic reactor described in step (6) is in an oxygen-free atmosphere, and the gas type is consistent with that in step (4).

9. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: The ammonia-containing condition mentioned in step (7) refers to a carrier gas consisting of pure NH3 or a mixture of NH3 and other inert gases, wherein the other inert gas is either argon or nitrogen. In step (7), the third pyrolysis reactor is heated and kept at the same temperature as the first pyrolysis reactor in step (4). The pyrolysis temperature range, pyrolysis heating rate, holding time and gas flow rate of nitrogen-rich pyrolysis under ammonia conditions are consistent with the reaction conditions when easily aldehyde-ketalized pyrolysis vapor is obtained in the first pyrolysis reactor in step (4).

10. The production process for preparing pyridine-rich bio-oil from pretreated biomass fractionation-nitrogen-enriched pyrolysis according to claim 1, characterized in that: The condensing temperature of condenser tube 1 in step (5), condenser tube 2 in step (7), and condenser tube 3 in step (8) is -30 to -30 ℃.

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