阅读说明：本技术 一种提高生物质热解油中酚类化合物含量的方法 (Method for increasing content of phenolic compounds in biomass pyrolysis oil ) 是由 赵一博 何文静 张兰君 黄婷婷 许抒悦 常露 刘子恒 孙正军 于 2021-08-31 设计创作，主要内容包括：本发明是一种提高生物质热解油中酚类化合物含量的方法,该方法采用四氢萘THN预处理生物质快速热解的方法来制取酚类化合物,先向核桃壳WS内加入THN进行预混合；再进行热解反应,反应以氮气或惰性气体为载气,预热到400℃～600℃,然后将装有热解料的反应器推入反应炉中,于恒温区内反应5-8min,所得热解液体产物为热解油。本发明采用的THN预处理生物质,能实现共热解产生一定的协同效应,THN的加入可以提高热解液体产物产率,减少热解气体产物的生成。经THN预处理得到的热解油中酚类化合物的含量有明显提高,同时,THN的加入还抑制了酸类化合物及其他含氧化合物的生成,提高了焦油的品质。(The invention relates to a method for improving the content of phenolic compounds in biomass pyrolysis oil, which adopts a method of biomass fast pyrolysis pretreated by Tetrahydronaphthalene (THN) to prepare the phenolic compounds, and firstly, THN is added into walnut shells WS for premixing; then carrying out pyrolysis reaction, preheating to 400-600 ℃ by taking nitrogen or inert gas as carrier gas, then pushing the reactor filled with the pyrolysis material into a reaction furnace, and reacting for 5-8min in a constant temperature area, wherein the obtained pyrolysis liquid product is pyrolysis oil. According to the invention, the THN is adopted to pretreat the biomass, so that a certain synergistic effect can be generated by co-pyrolysis, the yield of the pyrolysis liquid product can be improved by adding the THN, and the generation of the pyrolysis gas product can be reduced. The content of phenolic compounds in the pyrolysis oil obtained by THN pretreatment is obviously improved, and meanwhile, the generation of acid compounds and other oxygen-containing compounds is inhibited by the addition of the THN, so that the quality of tar is improved.)

1. A method for improving the content of phenolic compounds in biomass pyrolysis oil is characterized in that the phenolic compounds are prepared by adopting a method of biomass fast pyrolysis through Tetrahydronaphthalene (THN) pretreatment, and the method comprises the following steps:

s1, pyrolysis material treatment: placing walnut shells WS in a mixing container with a stirring device, and mixing according to the weight ratio of WS: adding THN into the mixture according to the mass ratio of 1: 0.1-1: 1 for premixing, fully stirring and uniformly mixing, sealing, and standing at room temperature-120 ℃ for 1-36 hours to obtain a pyrolysis material;

s2, pyrolysis: carrying out pyrolysis on a tube furnace, taking a quartz tube as a reactor, taking 2U-shaped tubes under ice water bath as a secondary cooling device, adopting a thermocouple to test the temperature of the furnace, adjusting the temperature by using a temperature control device, loading pyrolysis materials on a quartz boat, placing the quartz boat in a quartz tube reactor, taking nitrogen or inert gas as carrier gas, wherein the flow range is 180-220 mL/min, adjusting the temperature control device to preheat the furnace to 400-600 ℃, then quickly pushing the quartz tube reactor with the pyrolysis materials into the reaction furnace, placing the pyrolysis materials in a constant temperature area, pushing the quartz tube reactor out of the reaction furnace after carrying out constant temperature reaction for 5-8min at the preheating temperature, closing a gas carrying valve after cooling to room temperature, closing the temperature control device, and obtaining pyrolysis liquid as pyrolysis oil.

2. The method for increasing the content of phenolic compounds in biomass pyrolysis oil according to claim 1, wherein the method comprises the following steps: in S1, the mass ratio of WS to THN is 1: 0.5.

3. The method for increasing the content of phenolic compounds in biomass pyrolysis oil according to claim 1, wherein the method comprises the following steps: in S1, the pyrolized material is left at room temperature for 24 hours before pyrolysis.

4. The method for increasing the content of phenolic compounds in biomass pyrolysis oil as claimed in claim 1, wherein: in S2, the preheating temperature is 500 ℃; the constant temperature reaction temperature was 500 ℃.

5. The method for increasing the content of phenolic compounds in biomass pyrolysis oil as claimed in claim 1, wherein: in S2, the temperature rising rate of the tube furnace is 1-20 ℃/min.

Technical Field

The invention relates to the technical field of chemical engineering and energy, in particular to a method for improving the content of phenolic compounds in biomass pyrolysis oil.

Background

China is a big country rich in coal, poor in oil and less in gas, and development of renewable energy sources is beneficial to getting rid of external dependence of energy sources early and achieving the strategic target of 2060-year carbon neutralization early. Biomass is considered the fourth most widely used energy source, accounting for approximately 10% of the global energy load, and biomass feedstocks contain approximately 1.08 × 10 energy per year¹¹Ton oil equivalent. Due to the advantages of renewability, abundant and easily available raw materials, zero emission of carbon dioxide, replacement of fossil energy and the like, biomass is widely utilized and developed by countries in the world. However, the energy utilization rate of the existing biomass is not high, and most of the biomass is discarded or incinerated, so that serious resource waste and environmental pollution are caused. Therefore, energy conversion of biomass has become a research hotspot of researchers.

In the research progress of energy conversion, a thermochemical method of fast pyrolysis is considered to be an effective method for utilizing biomass on a large scale, and a method for preparing bio-oil by using a fast pyrolysis technology can effectively utilize biomass energy, but the obtained bio-oil has the defects of high oxygen content, low calorific value, instability, high acidity, strong corrosivity and the like, which are caused by the high oxygen content (up to 40%) of biomass, so that a large amount of oxygen-containing compounds exist in pyrolysis products.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art and provides a method for improving the content of phenolic compounds in biomass pyrolysis oil so as to realize effective transfer of each element in biomass and improve the quality of the biomass oil.

The technical problem to be solved by the present invention is achieved by the following technical means. The invention relates to a method for improving the content of phenolic compounds in biomass pyrolysis oil, which is characterized in that the phenolic compounds are prepared by adopting a method for quickly pyrolyzing biomass pretreated by Tetrahydronaphthalene (THN), and the method comprises the following steps:

s1, pyrolysis material treatment: placing walnut shells WS in a mixing container with a stirring device, and mixing according to the weight ratio of WS: adding THN into the mixture according to the mass ratio of 1: 0.1-1: 1 for premixing, fully stirring and uniformly mixing, sealing, and standing at room temperature-120 ℃ for 1-36 hours to obtain a pyrolysis material;

s2, pyrolysis: carrying out pyrolysis on a tube furnace, taking a quartz tube as a reactor, taking 2U-shaped tubes under ice water bath as a secondary cooling device, adopting a thermocouple to test the temperature of the furnace, adjusting the temperature by using a temperature control device, taking nitrogen or inert gas as carrier gas, adjusting the flow range of the nitrogen or inert gas to be 180-220 mL/min, adjusting the temperature control device to preheat the furnace to 400-600 ℃, then quickly pushing a quartz tube reactor filled with pyrolysis materials (placed on a quartz boat) into the reaction furnace, placing the pyrolysis materials in a constant temperature area, carrying out constant temperature reaction at the preheating temperature for 5-8min, then pushing the quartz tube reactor out of the reaction furnace, closing a gas carrying valve after cooling to room temperature, and closing the temperature control device to obtain a pyrolysis liquid product which is pyrolysis oil.

The invention relates to a method for improving the content of phenolic compounds in biomass pyrolysis oil, which further adopts the preferable technical scheme that: in S1, the mass ratio of WS to THN is 1: 0.5.

The invention relates to a method for improving the content of phenolic compounds in biomass pyrolysis oil, which further adopts the preferable technical scheme that: in S1, the pyrolized material is left at room temperature for 24 hours before pyrolysis.

The invention relates to a method for improving the content of phenolic compounds in biomass pyrolysis oil, which further adopts the preferable technical scheme that: in S2, the preheating temperature is 500 ℃; the constant temperature reaction temperature was 500 ℃.

The invention relates to a method for improving the content of phenolic compounds in biomass pyrolysis oil, which further adopts the preferable technical scheme that: in S2, the temperature rise rate of the tube furnace is 10 ℃/min.

The inventor of the present invention found that if hydroxyl (oxygen) in biomass can be effectively transferred to benzene ring in the pyrolysis process, the content of phenolic compounds can be increased, and the content of acid compounds and other oxygen-containing compounds can be effectively reduced, so as to improve the quality of bio-oil. Meanwhile, the THN is a hydrogen supply solvent commonly used for coal and biomass liquefaction, contains a benzene ring structure, has certain hydrogen supply capacity, and can be used for co-pyrolysis with biomass to improve the content of phenols in pyrolysis products.

The method aims to improve the content of phenolic compounds in the biomass pyrolysis oil, and effectively transfers hydroxyl (oxygen) in the biomass to a benzene ring by adopting a thermochemical conversion technology of THN pretreatment biomass fast pyrolysis, so that the content of phenols in products is improved, the contents of acid compounds and other oxygen-containing compounds are effectively reduced, and the quality of the bio-oil is improved.

Compared with the prior art, the invention has the following beneficial effects or advantages:

1. the method for pretreating biomass by THN can realize a certain synergistic effect in the co-pyrolysis process, and the addition of THN can improve the yield of pyrolysis liquid products and reduce the generation of pyrolysis gas products.

2. Compared with the traditional method for directly pyrolyzing biomass, the method provided by the invention has the advantages that the content of phenolic compounds in the pyrolysis oil obtained by THN pretreatment is obviously increased, meanwhile, the generation of acid compounds and other oxygen-containing compounds is inhibited by the addition of THN, and the quality of tar is improved.

3. The method of the invention increases the content of phenolic compounds in the biomass pyrolysis oil, and has the advantages of low requirement on equipment, low price of reaction raw materials, controllable reaction temperature and various conditions, simple pyrolysis process flow and convenient repeated engraving.

Drawings

FIG. 1 is a graph comparing an experimental value (A) and a theoretical value (T) of yields of pyrolysis products in experimental examples;

FIG. 2 is a graph comparing the experimental value (A) and the theoretical value (T) of the composition of the pyrolysis liquid product of the experimental example.

Detailed Description

In order to better understand the technical scheme, the technical scheme is explained in detail in the following with the accompanying drawings of the specification and a specific method.

Example 1, a method for increasing the phenolic compound content of biomass pyrolysis oil, comprising the steps of:

s1, pyrolysis material treatment: placing WS in a mixing container with a stirring device, and mixing according to the weight ratio of WS: adding THN into the mixture according to the mass ratio of 1:0.5 for premixing, fully stirring and uniformly mixing, sealing, and standing at room temperature for 24 hours to obtain a pyrolysis material;

s2, pyrolysis: the pyrolysis is carried out on a tube furnace, a quartz tube is taken as a reactor, 2U-shaped tubes under ice water bath are taken as a secondary cooling device, the temperature of the furnace is tested by adopting a thermocouple, the temperature is adjusted by adopting a temperature control device, argon is taken as carrier gas, the flow range is 200mL/min, the temperature control device is adjusted to preheat the furnace to 500 ℃, and the temperature rise rate of the tube furnace is 10 ℃/min. And then quickly pushing the quartz tube reactor filled with the pyrolysis material (on the quartz boat) into the reaction furnace, placing the pyrolysis material in a constant temperature area, carrying out constant temperature reaction at the preheating temperature for 6min, then pushing the quartz tube reactor out of the reaction furnace, cooling to room temperature, then closing the argon valve, and closing the temperature control device, wherein the obtained pyrolysis liquid product is pyrolysis oil.

Example 2 WS fast pyrolysis comparative experiment after THN pretreatment:

experimental example: the pyrolysis is carried out using the method described in example 1 (all differences in parameters, the differences being explained below), in which: the tube furnace is a common tube heating furnace which can be controlled by a program, the diameter of the tube furnace is 34mm, and the length of the tube furnace is 200 mm.

The tube inner diameter of the reaction tube body is 28mm, the wall thickness is 2mm, the length is 600mm, the outer diameter of the quartz boat is 26mm, the wall thickness is 1mm, and the length is 100 mm.

The condensing unit is composed of 2U-shaped tubes connected in series, the U-shaped tubes are placed in an ice-water bath, and tar in the pyrolysis gas is fully condensed by using the purpose of multi-stage condensation so as to ensure the calculation of yield.

The pyrolysis experimental procedure was as follows: introducing argon as carrier gas, wherein the flow rate is 200mL/min, putting WS (the mass ratio of WS to THN is 1:0.125, 1:0.25 and 1:0.5 respectively) subjected to THN pretreatment into a quartz boat as a sample, wherein the chemical composition and the element analysis of the WS sample are shown in Table 1, the heating rate is set to be 10 ℃/min, the final temperature is set to be 500 ℃, and heating is started. When the furnace temperature reaches 500 ℃, the quartz tube reactor is quickly pushed into the tube furnace, so that the THN and WS fast pyrolysis is realized.

The following table 1 is a table of chemical compositions and elemental analyses of walnut shell samples used in the experiments:

TABLE 1 chemical composition and elemental analysis Table of walnut Shell samples

Differential subtraction method

Determination of the semicoke yield: the yield of the semicoke can be determined by weighing the mass of the remaining semicoke in the quartz boat after pyrolysis.

Determination of the amount of tar: pyrolysis tar is collected by using a U-shaped pipe, wherein the amount of tar in the U-shaped pipe can be determined by measuring the mass of the U-shaped pipe before and after pyrolysis. Weighing the empty U-shaped pipe before the experiment, weighing the U-shaped pipe containing the sample again after the experiment, and obtaining the quality of tar in the U-shaped pipe through subtraction.

Gas yield: a subtraction method is used.

Comparative example 1: the procedure was the same as in the experimental example except that WS was pyrolyzed alone without the addition of THN pretreatment.

Comparative example 2: the procedure was the same as in the experimental example, except that THN was pyrolyzed alone.

The experimental results are shown in table 2 and fig. 1; table 2 is a graph showing the yields of the experimental examples and the comparative examples; FIG. 1 is a comparison of experimental and theoretical values for yield of pyrolysis products.

TABLE 2 pyrolysis product yield Table

From the above experiments, it can be seen that the yield of tar in the examples is higher than that in comparative example 1, as shown by comparative analysis of the yields of fast pyrolysis products in the examples and comparative examples. When the mass ratios of WS and THN were 1:0.125, 1:0.25 and 1:0.5, the liquid yields were 55.91%, 60.67%, 60.91%, respectively, which are higher than the liquid yield (48.5%) of pyrolysis of WS alone, and the gas yields were 17.82%, 14.51%, 18.67%, respectively, which are lower than the gas yield (21.12%) of pyrolysis of WS alone, so that the tar yield was improved in example over that in comparative example 1.

The theoretical value (T) of the experimental example can be calculated from comparative example 1 and comparative example 2 as follows: the pyrolysis product yields or compositions of comparative examples 1 and 2 are noted as Yws and Y_THNThen, theoretical values of yield and composition of pyrolysis products of different mass ratios of WS and THN (1: a) were calculated from the formula (1).

Taking the liquid product yield as an example: the WS pyrolysis liquid yield was 48.5%, the THN pyrolysis liquid yield was 68.5%, and the theoretical value of the liquid yield was 52.5% when the mass ratio of WS to THN was 1: 0.25.

FIG. 1 is a comparison between the experimental value (A) and the theoretical value in the experimental example, and it can be seen that the yields of pyrolysis liquid products are 55.91%, 60.67% and 60.91% respectively at the mass ratios of WS and THN of 1:0.125, 1:0.25 and 1:0.5, respectively, which are increased by 5.19%, 8.17% and 5.75% respectively compared with the theoretical value, and the yields of gases are 17.82%, 14.51% and 18.67% respectively, and are decreased by 4.45%, 8.68% and 5.91% respectively compared with the theoretical value, which indicates that the synergistic effect is generated during the fast pyrolysis of the THN pretreated WS, and the synergistic effect is most obvious at the mass ratio of WS and THN of 1: 0.25.

The reasons for the above phenomena are: THN is a common hydrogen supply solvent, can generate a large amount of H & lt- & gt in the thermal cracking process, can stabilize free radical fragments generated by WS pyrolysis, and improves the yield of pyrolysis tar; WS is also a hydrogen-rich material in itself, and a large number of small-molecule radical fragments, such as H, HO and CH, are also produced during pyrolysis₃Etc., which can be combined with radical fragments produced by the pyrolysis of THN, thereby increasing tar yield; the combination of small molecule free radical and other free radical makes small moleculeThe binding between molecular radicals is reduced and the reaction history during pyrolysis is changed due to the reaction between radicals, resulting in a reduction in the yield of gaseous products.

Table 3 shows the compositions of the pyrolysis liquid products of the experimental examples and comparative examples, and it can be seen from the table that the content of phenols in the WS pyrolysis liquid product after THN pretreatment is significantly increased and the content of acids is significantly decreased compared to the WS pyrolysis alone. When the mass ratio of WS to THN is 1:0.125, 1:0.25 and 1:0.5, the phenolic content in the pyrolysis liquid product is respectively 53.27%, 53.62% and 59.6%, which are higher than the phenolic content (49.66%) in the pyrolysis liquid product alone WS, and the acid content is respectively 0.29%, 0.09% and 0%, which is lower than the acid content (1.77%) in the pyrolysis liquid product alone WS. Therefore, compared with the comparative example 1, the content of the phenolic substances in the tar is increased, and the content of the acid substances is reduced.

Meanwhile, theoretical values of the liquid compositions of the experimental examples are calculated according to the formula (1) and compared with the experimental values, and the results are shown in FIG. 2. As can be seen from FIG. 2, compared with the theoretical value, (1) the content of phenols is obviously increased, when the mass ratio of WS to THN is 1:0.125, 1:0.25 and 1:0.5, the content of phenols in the pyrolysis liquid product is respectively improved by 9.13%, 13.89% and 26.93% compared with the theoretical value, and the higher the addition amount of THN is, the more obvious the content of phenols in the liquid product is improved; (2) the contents of oxygen-containing compounds such as acids, alcohols, esters and the like are reduced to a certain extent, for the acids, the contents of the acids in the pyrolysis liquid product are respectively reduced by 1.28%, 1.33% and 1.18% compared with the theoretical value when the mass ratio of WS to THN is 1:0.125, 1:0.25 and 1:0.5, the content of the acids in the liquid product is lower when the addition amount of the THN is larger, and almost no acid substances are generated in the liquid product when the mass ratio of WS to THN is 1: 0.5.

The above phenomena again show that THN and WS pyrolysis in the THN pretreatment WS fast pyrolysis process produces a synergistic effect, and that THN produces a large amount of free radicals of benzene derivatives in addition to H, which are generated with the free radicals produced by WS pyrolysis, such as OH, OCH₃And the like, and the content of phenolic substances in the pyrolysis product is increased; simultaneously changes the migration path of O element in the pyrolysis process, more oxygen-containing groups are combined with benzene derivative free radicals to generate phenolThe content of alcohols, aldehydes, acids and esters in the aliphatic hydrocarbon is reduced; this tendency becomes more pronounced the higher the THN content. The phenols in the pyrolysis oil are increased, and the acid content is reduced, so that the quality of the bio-oil is improved.

TABLE 3 table of contents of pyrolysis liquid products

In conclusion, the rapid pyrolysis method for WS by THN pretreatment can improve the synergistic effect of the co-pyrolysis process, improve the yield of pyrolysis tar and the content of phenolic compounds, and reduce the content of acids and oxygen-containing compounds.