A method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieve combined with seaweed charcoal for graded catalytic pyrolysis of biomass

Abstract

The present invention belongs to the field of biomass utilization, and specifically relates to a method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieves and seaweed charcoal for graded catalytic pyrolysis of biomass. The catalytic pyrolysis method of the present invention is to first use a zeolite molecular sieve catalyst to convert the volatile matter of biomass pyrolysis in a low temperature range into light aromatic hydrocarbons to a large extent, and then use a modified seaweed charcoal catalyst to convert the volatile matter of the pyrolysis residue in a medium temperature range into monophenol chemicals. The seaweed charcoal catalyst used in the present invention has high catalytic activity after activation treatment, and can realize the efficient conversion of lignocellulosic biomass into monophenol chemicals. Based on the idea of ​​graded catalytic pyrolysis, the present invention first uses zeolite molecular sieves to catalytically pyrolyze cellulose and hemicellulose in biomass, which solves the problem of poor pyrolysis effect of cellulose and hemicellulose in the process of catalytic pyrolysis of biomass, and then uses seaweed charcoal to catalytically pyrolyze lignin, thereby improving the utilization rate of bio-oil and realizing high-value conversion and utilization of all components of biomass.

Description

Technical Field

[0001] The present invention belongs to the field of biomass utilization, and specifically relates to a method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieves combined with seaweed charcoal for graded catalytic pyrolysis of biomass. Background Art

[0002] Biomass pyrolysis technology enables the sustainable resource utilization of biomass waste. As a large-scale resource with broad prospects, it plays a crucial role in supplementing the massive consumption of fossil fuels. Current biomass pyrolysis technologies have evolved from direct pyrolysis to catalytic pyrolysis, with biochar catalysts playing a significant role in enhancing resource utilization. The three major components of biomass sawdust are cellulose, hemicellulose, and lignin. However, biochar catalysts have been found to be ineffective in regulating the pyrolysis products of cellulose and hemicellulose, while exhibiting high selectivity for the pyrolysis of lignin to produce monophenols. Furthermore, thermal stability analysis of cellulose, hemicellulose, and lignin revealed significant differences in their pyrolysis temperature ranges. Therefore, using biochar catalysts alone in biomass pyrolysis cannot maximize pyrolysis efficiency, and methods for regulating the pyrolysis products of cellulose and hemicellulose are lacking. Clearly, direct catalytic pyrolysis using biochar catalysts is not the optimal choice for biomass pyrolysis. There is an urgent need to address the poor pyrolysis of cellulose and hemicellulose in biomass and achieve high-value conversion and utilization of all biomass components. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieves combined with seaweed charcoal for graded catalytic pyrolysis of biomass. The method is based on the idea of ​​graded catalytic pyrolysis. The cellulose and hemicellulose in the biomass are first catalytically pyrolyzed using zeolite molecular sieves, which solves the problem of poor pyrolysis effect of cellulose and hemicellulose during the catalytic pyrolysis of biomass. Seaweed charcoal is then used to catalytically pyrolyze lignin, thereby improving the utilization rate of bio-oil and realizing high-value conversion and utilization of all components of biomass.

[0004] To achieve the above object, the present invention is implemented through the following technical solutions:

[0005] The present invention provides a method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieves combined with seaweed charcoal for graded catalytic pyrolysis of biomass, comprising the following steps:

[0006] S1. Preparation of modified seaweed charcoal: first, the seaweed raw material is crushed and carbonized to obtain seaweed charcoal, the seaweed charcoal is mixed and ground evenly with an alkaline activator, and then activated at high temperature, and then washed and dried to obtain the modified seaweed charcoal;

[0007] S2. Zeolite molecular sieve catalytic pyrolysis: The biomass feedstock and the zeolite molecular sieve are placed in separate reactors for ex situ catalytic pyrolysis, and the gases, bio-oil rich in light aromatics and monophenol products, and biomass residue produced during the pyrolysis process are collected;

[0008] S3. Catalytic pyrolysis of modified seaweed charcoal: The biomass residue of S2 and the modified seaweed charcoal of S1 were placed in reactors for heterogeneous catalytic pyrolysis, and the gas, bio-oil rich in light aromatics and monophenol products, and coke produced during the pyrolysis process were collected.

[0009] Preferably, in step S1, the carbonization conditions are: a heating rate of 5 to 10°C / min, a carbonization temperature of 450 to 550°C, and a carbonization time of 60 to 120 min.

[0010] Preferably, in step S1, the alkaline activator is a mixture of one or more of NaOH, KOH, NaHCO3, Na2CO3, KHCO3, and K2CO3, and the mass ratio of the seaweed charcoal to the alkaline activator is (1-2):1.

[0011] Preferably, in step S1, the high-temperature activation conditions are: a heating rate of 5 to 10°C / min, a target temperature of 700 to 900°C, and a high-temperature activation time of 60 minutes.

[0012] Preferably, in step S2, the biomass raw material is sawdust.

[0013] Preferably, in step S2, the zeolite molecular sieve catalytic pyrolysis conditions are: the mass ratio of biomass raw material to zeolite molecular sieve is 2:1, the pyrolysis temperature is 300-400°C, and the pyrolysis atmosphere is nitrogen or carbon dioxide.

[0014] Preferably, in step S3, the catalytic pyrolysis conditions of the modified seaweed charcoal are: the pyrolysis temperature is 600-800° C., and the pyrolysis atmosphere is nitrogen or carbon dioxide.

[0015] Preferably, in steps S2 and S3, the zeolite molecular sieve or modified seaweed charcoal is fixedly placed below the raw material to be pyrolyzed, and the raw material is evenly fed into the fixed bed tubular reactor pipe through a feeder and stays above the zeolite molecular sieve; this method is non-in situ catalytic pyrolysis, the catalyst does not contact the biomass raw material, and the catalyst can be recovered and reused.

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

[0017] The catalytic pyrolysis method of the present invention first uses a zeolite molecular sieve catalyst to convert the volatile matter of biomass pyrolysis in a low temperature range to a large extent into light aromatic hydrocarbons, and then uses a modified seaweed charcoal catalyst to convert the pyrolysis residue into monophenolic chemicals in a medium temperature range. The present invention is based on the idea of ​​hierarchical catalytic pyrolysis. The cellulose and hemicellulose in the biomass are first catalytically pyrolyzed using a zeolite molecular sieve. The zeolite molecular sieve has well-developed micropores, high thermal stability and strong acid resistance. It can highly selectively crack the cellulose and hemicellulose in the biomass to produce furans, furfural and other substances, and then convert them into aromatic hydrocarbon products through the excellent aromatization effect of the zeolite molecular sieve, solving the problem of poor pyrolysis effect of cellulose and hemicellulose in the biomass catalytic pyrolysis process. Then, a modified seaweed charcoal catalyst with high catalytic activity is used to achieve rapid and efficient conversion of lignin into monophenolic chemicals. The present invention improves the utilization rate of bio-oil and realizes high-value conversion and utilization of all components of biomass. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a step diagram of a method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieves combined with seaweed charcoal for graded catalytic pyrolysis of biomass. DETAILED DESCRIPTION

[0019] The following is a further description of specific embodiments of the present invention. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0020] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0021] Example 1 Molecular sieve combined with seaweed charcoal to graded catalytic pyrolysis of biomass to produce light aromatics and monophenol products

[0022] The zeolite molecular screening used in this embodiment is ZSM-5, with an average particle size of 50 nm, Si / Al=36, and a specific surface area of ​​311.69 m 2 / g, pore volume is 0.070m 3 / g, pore size is 1.418 nm; the raw material of the seaweed charcoal catalyst of this embodiment is Enteromorpha; the biomass raw material of this embodiment is 60 mesh poplar sawdust; this embodiment is according to Figure 1 The specific steps are as follows:

[0023] 1. Preparation of modified activated carbon: First, crush the Enteromorpha striata into 60 mesh powder, slowly pyrolyze and carbonize the Enteromorpha striata powder in a reactor, set the carbonization target temperature to 500℃, the heating rate to 5℃ / min, and the carbonization time to 60min. After the carbonization, collect the seaweed charcoal, wash it with deionized water until it is neutral, and then dry it in a 105℃ oven for 12h; 4g of the dried seaweed charcoal was mixed with 2g of potassium hydroxide and ground evenly, and the mixture was slowly pyrolyzed and activated in a reactor. The target temperature was 800°C, the heating rate was 5°C / min, and after reaching 800°C, it was maintained for 60 minutes. After cooling, the modified seaweed carbon was collected; the collected modified seaweed carbon was ground into powder, added into 600mL deionized water to dissolve, magnetically stirred for 30 minutes, and then added into 30mL of 1mol / L hydrochloric acid. Ultrasonic vibration was performed for 2 hours, and the solid was collected and washed with deionized water until the pH was neutral, and then filtered with filter paper. It was dried in an oven at 105°C for 24 hours to obtain the modified seaweed carbon;

[0024] 2. Catalytic pyrolysis of zeolite molecular sieve: first stabilize the temperature of the tubular reactor at 300°C, and feed 1g of poplar sawdust from the upper port at a rate of 2g / h; use N2 as an inert protective atmosphere, and control the flow rate to 100mL / min; set up two layers of upper and lower quartz wool in the middle reaction zone of the tubular reactor, take 0.5g of ZSM-5 and fix it with quartz wool below the biomass raw material, and the poplar sawdust is evenly fed into the tubular reactor through a feeder, and stays on the quartz wool fixed above the ZSM-5 for catalytic pyrolysis; two low-temperature cooling circulation pumps at -12°C are used to condense the volatiles produced by the reaction, and the gaseous products are stored in a gas collection bag. The bio-oil is collected by extraction and dissolution. After extraction, a product obtained by mixing bio-oil and anhydrous methanol in a ratio of 1g:10mL is obtained, and the biomass residue in the tubular reactor is collected, weighed, and the yield is calculated as the raw material for the next stage of catalytic pyrolysis process, and the ZSM-5 in the tubular reactor is collected;

[0025] 3. Catalytic pyrolysis of modified seaweed charcoal: first stabilize the temperature of the tubular reactor at 600°C, and feed all the biomass residues collected after the pyrolysis in step 2 from the upper port at a rate of 1g / h; use N2 as an inert protective atmosphere, and control the flow rate to 100mL / min; set up two layers of upper and lower quartz wool in the middle reaction zone of the tubular reactor, take 0.5g of modified seaweed charcoal and fix it with quartz wool below the biomass raw material, and the biomass residue is evenly fed into the tubular reactor through the feeder, and stays on the quartz wool fixed above the modified seaweed charcoal for catalytic pyrolysis; use two -12°C low-temperature cooling circulation pumps to condense the volatiles produced by the reaction, and the gaseous products are stored in a gas collection bag. The bio-oil is collected by extraction and dissolution. After extraction, a product obtained by mixing bio-oil and anhydrous methanol in a ratio of 1g:10mL is obtained, and the modified seaweed charcoal and coke after the reaction are collected.

[0026] The obtained products were characterized. During the first-stage ZSM-5 catalytic pyrolysis process, the liquid phase product yield was 34.1wt.%, the gas phase product yield was 31.8wt.%, and the solid phase product was 33.5wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 8.2%, and the aromatic hydrocarbon content was 31.6%. During the second-stage modified seaweed charcoal catalytic pyrolysis process, the liquid phase product yield was 12.1wt.%, the non-condensable gas yield was 19.2wt.%, and the solid phase yield was 68.7wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 76.2%, and the aromatic hydrocarbon content was 12.3%.

[0027] Example 2: Molecular sieve combined with seaweed charcoal for graded catalytic pyrolysis of biomass to produce light aromatic hydrocarbons and monophenol products

[0028] The preparation method is the same as that of Example 1, except that in the catalytic pyrolysis of the zeolite molecular sieve, the temperature of the tubular reactor is changed to 325° C., and the other steps and parameters remain unchanged.

[0029] The obtained products were characterized. During the first-stage ZSM-5 catalytic pyrolysis process, the liquid phase product yield was 35.2wt.%, the gas phase product yield was 31.5wt.%, and the solid phase product was 32.1wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 16.6%, and the aromatic hydrocarbon content was 34.7%. During the second-stage modified seaweed charcoal catalytic pyrolysis process, the liquid phase product yield was 10.1wt.%, the non-condensable gas yield was 16.9wt.%, and the solid phase yield was 69wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 63.7%, and the aromatic hydrocarbon content was 31.2%.

[0030] Example 3: Molecular sieve combined with seaweed charcoal for graded catalytic pyrolysis of biomass to produce light aromatics and monophenol products

[0031] The preparation method is the same as that of Example 1, except that in the catalytic pyrolysis of the zeolite molecular sieve, the temperature of the tubular reactor is changed to 350° C., and the other steps and parameters remain unchanged.

[0032] The obtained products were characterized. During the first-stage ZSM-5 catalytic pyrolysis process, the liquid phase product yield was 36.8wt.%, the gas phase product yield was 29.2wt.%, and the solid phase product was 29.8wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 22.2%, and the aromatic hydrocarbon content was 39.7%. During the second-stage modified seaweed charcoal catalytic pyrolysis process, the liquid phase product yield was 7.8wt.%, the non-condensable gas yield was 15.6wt.%, and the solid phase yield was 75.6wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 35.1%, and the aromatic hydrocarbon content was 53.6%.

[0033] Example 4: Molecular sieve combined with seaweed charcoal for graded catalytic pyrolysis of biomass to produce light aromatics and monophenols

[0034] The preparation method is the same as that of Example 1, except that in the catalytic pyrolysis of the zeolite molecular sieve, the temperature of the tubular reactor is changed to 375° C., and the other steps and parameters remain unchanged.

[0035] The obtained products were characterized. During the first-stage ZSM-5 catalytic pyrolysis process, the liquid phase product yield was 42.1wt.%, the gas phase product yield was 27.3wt.%, and the solid phase product was 24.3wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 26.6%, and the aromatic hydrocarbon content was 42.5%. During the second-stage modified seaweed charcoal catalytic pyrolysis process, the liquid phase product yield was 7.1wt.%, the non-condensable gas yield was 14.9wt.%, and the solid phase yield was 76.3wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 12.5%, and the aromatic hydrocarbon content was 77.1%.

[0036] Example 5: Molecular sieve combined with seaweed charcoal for graded catalytic pyrolysis of biomass to produce light aromatics and monophenol products

[0037] The preparation method is the same as that of Example 1, except that in the catalytic pyrolysis of the zeolite molecular sieve, the temperature of the tubular reactor is changed to 400° C., and the other steps and parameters remain unchanged.

[0038] The obtained products were characterized. During the first-stage ZSM-5 catalytic pyrolysis process, the liquid phase product yield was 44.2wt.%, the gas phase product yield was 27.1wt.%, and the solid phase product was 24.0wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 29.3%, and the aromatic hydrocarbon content was 43.3%. During the second-stage modified seaweed charcoal catalytic pyrolysis process, the liquid phase product yield was 6.3wt.%, the non-condensable gas yield was 13.3wt.%, and the solid phase yield was 80.0wt.%. GC-MS was then used to analyze the components of the liquid product, and the monophenol content in the bio-oil was 6.6%, and the aromatic hydrocarbon content was 89.7%.

[0039] In summary, the catalytic pyrolysis method of the present invention first uses a zeolite molecular sieve catalyst to convert the biomass pyrolysis volatiles in the low temperature range into light aromatic hydrocarbons to a large extent, and then uses a modified seaweed charcoal catalyst to convert the pyrolysis residue into monophenol chemicals in the medium temperature range. In Examples 1 to 5, different monophenol and aromatic hydrocarbon yields were obtained by changing the temperature of the tubular reactor in the zeolite molecular sieve catalytic pyrolysis. As the temperature rises, the yield of liquid products in the first-stage ZSM-5 catalytic pyrolysis process increases, and the yield of monophenols and aromatic hydrocarbons therein increases, the solid phase product raw materials used for subsequent biochar are reduced, and the monophenol yield of biochar catalytic pyrolysis is greatly reduced; therefore, the temperature of the tubular reactor in the zeolite molecular sieve catalytic pyrolysis can be adjusted according to the actual industrial production of monophenols or aromatic hydrocarbons.

[0040] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

Claims

1. A method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieves combined with seaweed charcoal for graded catalytic pyrolysis of biomass, characterized in that: The following steps are involved: S1. Preparation of modified seaweed charcoal: first, the seaweed raw material is crushed and carbonized to obtain seaweed charcoal, the seaweed charcoal is mixed and ground evenly with an alkaline activator, and then activated at high temperature, and then washed and dried to obtain the modified seaweed charcoal; S2. Zeolite molecular sieve catalytic pyrolysis: The biomass feedstock and the zeolite molecular sieve are placed in separate reactors for ex situ catalytic pyrolysis, and the gases, bio-oil rich in light aromatics and monophenol products, and biomass residue produced during the pyrolysis process are collected; S3, catalytic pyrolysis of modified seaweed charcoal: The biomass residue of S2 and the modified seaweed charcoal of S1 are placed in reactors for heterogeneous catalytic pyrolysis, and the gas, bio-oil rich in light aromatics and monophenol products, and coke produced during the pyrolysis process are collected; In step S2, the biomass raw material is poplar sawdust; In step S2, the zeolite molecular sieve catalytic pyrolysis conditions are: the mass ratio of biomass raw material to zeolite molecular sieve is 2:1, the pyrolysis temperature is 300-400° C., and the pyrolysis atmosphere is nitrogen or carbon dioxide; In step S3, the catalytic pyrolysis conditions of the modified seaweed charcoal are: the pyrolysis temperature is 600-800° C., and the pyrolysis atmosphere is nitrogen or carbon dioxide.

2. The method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieve combined with seaweed charcoal for graded catalytic pyrolysis of biomass according to claim 1, characterized in that: In step S1, the carbonization conditions are: a heating rate of 5 to 10°C / min, a carbonization temperature of 450 to 550°C, and a carbonization time of 60 to 120 min.

3. The method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieve combined with seaweed charcoal for graded catalytic pyrolysis of biomass according to claim 1, characterized in that: In step S1, the alkaline activator is a mixture of one or more of NaOH, KOH, NaHCO3, Na2CO3, KHCO3, and K2CO3, and the mass ratio of the seaweed charcoal to the alkaline activator is (1-2):

1.

4. The method for preparing light aromatic hydrocarbons and monophenol products by using molecular sieves combined with seaweed charcoal for graded catalytic pyrolysis of biomass according to claim 1, characterized in that: In step S1, the high-temperature activation conditions are: a heating rate of 5 to 10°C / min, a target temperature of 700 to 900°C, and a high-temperature activation time of 60 minutes.

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