A method for directional control of biomass microwave-assisted pyrolysis product distribution using bio-coke-based catalyst

Abstract

The present invention discloses a method for directionally controlling the distribution of biomass microwave-assisted pyrolysis products using a bio-coke-based catalyst, comprising the following steps: subjecting biomass to microwave-assisted pyrolysis to obtain bio-coke; acid-washing the bio-coke with an acid solution, and optionally loading the bio-coke with an active metal to obtain a bio-coke-based catalyst; subjecting the bio-coke-based catalyst and the biomass feedstock to microwave-assisted pyrolysis to obtain bio-oil, syngas, and biochar; and adjusting the type of acid solution and / or active metal to obtain bio-oil, syngas, and biochar in different distribution ratios; the active metal is derived from the positive electrode of a waste lithium-ion battery. The method of the present invention utilizes microwave pyrolysis, acid washing, and optional loading of an active metal to synergistically improve the efficiency of biomass pyrolysis, control the distribution of biomass pyrolysis products, and improve the selectivity of high-value-added chemicals in the pyrolysis products, thus having important practical significance for the biochemical industry and the efficient utilization of national energy.

Description

Technical Field

[0001] The present invention relates to the field of biomass energy conversion, and more specifically, to a method for directionally controlling the distribution of biomass microwave-assisted pyrolysis products using a bio-coke-based catalyst. Background Art

[0002] Thermochemical conversion processes (such as hydrothermal treatment, pyrolysis, gasification, and combustion) have been widely used to efficiently convert various biomass resources into renewable energy sources within a short period of time (seconds to minutes). Pyrolysis, due to its multiple product effects and high conversion efficiency, has become one of the most popular processes for bioenergy production. Furthermore, pyrolysis polygeneration technology can co-produce syngas, bio-oil, and biochar from biomass, thereby improving reaction conversion efficiency and economic benefits.

[0003] Biomass pyrolysis is typically performed using traditional electric heating or microwave heating (microwave-assisted pyrolysis). In traditional electric heating, a heat transfer medium transfers heat to the material, which then conducts the heat from the surface to the interior. Furthermore, at high heating rates, the material's inherent conductivity from the outside in can easily lead to overheating and compromise the pyrolysis effect. However, in microwave heating, polar molecules within the material rub against each other, generating internal energy and creating a temperature gradient from the inside out. Compared to traditional heating, microwave heating offers advantages such as high heating rates, high energy efficiency, and fast start-up and shutdown responses. Microwave heating overcomes the heat and mass transfer challenges inherent in traditional heating, and therefore holds great promise for its application. However, due to the selective heating characteristics of microwaves, a crucial prerequisite for their application in biomass pyrolysis is the identification of a suitable medium with excellent microwave absorption properties, namely, a microwave absorber. Biochar (biochar) materials are good microwave absorbers. Due to their acidic properties, oxygen-containing functional groups, and good pore structure, they are often used as in-situ catalysts for the cracking conversion of pyrolytic bio-oil and the improvement of bio-oil quality. However, the syngas, bio-oil, and biochar produced by the pyrolysis of biomass using current biochar materials as microwave absorbers are of poor quality, with low selectivity for high-value-added products. In response to different market demands, it is necessary to change the type of microwave absorber to achieve the regulation of the distribution of biomass pyrolysis products. Therefore, providing a simple, low-cost process to achieve the targeted regulation of the distribution of biomass pyrolysis products, thereby upgrading the quality of the target products and generating high-value-added products, is of great and far-reaching significance to the biochemical industry and the efficient utilization of national energy.

[0004] Lithium-ion batteries (LIBs) are widely used in various electronic products. To avoid environmental pollution and resource waste, the proper recycling of large quantities of discarded LIBs has attracted widespread attention. Generally speaking, the cathode materials of spent LIBs contain a variety of valuable metals (such as nickel, cobalt, manganese, lithium, and aluminum), which have high recycling value. Therefore, research on the recycling and reuse of spent LIBs is of great significance. Summary of the Invention

[0005] Based on the above background, the object of the present invention is to provide a method for directionally regulating the distribution of biomass microwave-assisted pyrolysis products.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for directionally controlling the distribution of biomass microwave-assisted pyrolysis products using a bio-coke-based catalyst comprises the following steps:

[0008] 1) Microwave-assisted pyrolysis of biomass to obtain biochar;

[0009] 2) After the bio-semi-coke is acid-washed, optionally, active metals are loaded on the bio-semi-coke to obtain a bio-semi-coke-based catalyst;

[0010] 3) The bio-coke-based catalyst and biomass raw materials are subjected to microwave-assisted pyrolysis to obtain bio-oil, synthesis gas and biochar;

[0011] 4) adjusting the type of the acid solution and / or active metal to obtain bio-oil, syngas, and biochar with different compositions and distribution ratios;

[0012] Wherein, in step 2), the active metal is derived from the acid leaching solution of the positive electrode of the waste lithium-ion battery.

[0013] Bio-semi-coke can provide an active surface for hydrocarbon cracking and is rich in alkali metal and alkaline earth metal elements. These two types of metal elements have very good catalytic effects on the cracking of bio-tar. In addition, bio-semi-coke has the advantages of excellent electromagnetic wave absorption performance, good catalytic performance and high economy, which can significantly improve the selectivity of high value-added products in microwave-assisted pyrolysis products. Generally, bio-semi-coke is produced by conventional electric heating or microwave-assisted pyrolysis of biomass. Compared with conventional electric heating, the semi-coke produced by microwave pyrolysis has a larger specific surface area and porosity, and is a better carrier for microwave absorption catalysts. Bio-semi-coke-based catalysts exhibit a strong synergistic effect when coupled with the microwave effect and applied to biomass pyrolysis. In addition, acid washing of bio-semi-coke can remove inorganic ash, increase the porosity and specific surface area of ​​the semi-coke, and increase the surface functional groups, thereby improving the catalytic activity. The present invention has found that the distribution of pyrolysis products can be regulated by acid washing with different acid solutions. In addition to acid washing, the transition metal elements of the positive electrode of the waste lithium-ion battery can be selectively loaded onto the semi-coke carrier to improve the catalytic activity of the catalyst and further regulate the distribution of biomass pyrolysis products.

[0014] Furthermore, in the above method, the acid solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, oxalic acid and citric acid.

[0015] The concentration of the acid solution is in the range of 0.5 mol / L to 5 mol / L.

[0016] The pickling is carried out under stirring for 5-10 hours.

[0017] The active metal includes at least one of iron, nickel, cobalt, manganese and the like.

[0018] Preferably, the active metal further includes aluminum and / or copper.

[0019] Preferably, the waste lithium-ion battery positive electrode is one or more of waste lithium iron phosphate, waste lithium nickel cobalt manganese oxide and waste lithium cobalt oxide.

[0020] In step 2), loading the active metal specifically includes the following steps: obtaining acid leaching solution of the positive electrode of the waste lithium-ion battery, using the acid leaching solution to impregnate the acid-washed bio-semi-coke, drying, and microwave calcining.

[0021] The microwave calcination conditions are as follows: microwave power of 360-600 W, and microwave calcination time of 5-20 min. It is understood that the microwave calcination is carried out under the protection of inert gas.

[0022] The solid-liquid ratio of the bio-semi-coke and the acid leaching solution is 1g:10-30mL.

[0023] Illustratively, the waste lithium-ion battery positive electrode and acid are mixed in a mass ratio of 1-3:50, and the acid leaching solution is obtained after sufficient stirring; wherein the acid used here can be the same as the acid solution for pickling.

[0024] It is understood that the bio-semicoke-based catalyst obtained in step 2) is also within the scope of protection of the present invention.

[0025] In step 1), the microwave-assisted pyrolysis is carried out in a fixed bed of an inert microwave absorbent.

[0026] Preferably, the inert microwave absorber is silicon carbide; more preferably, in the fixed bed of silicon carbide, the laying thickness of silicon carbide is 2-8 cm; and the particle size of the silicon carbide is 10-20 mesh.

[0027] Preferably, the mass ratio of the biomass to the inert microwave absorber is 1:5-20.

[0028] In step 1) or step 3), the conditions for the microwave-assisted pyrolysis are: the microwave power is 240-800 W, and the pyrolysis time is 10-30 minutes.

[0029] The mass ratio of the bio-semi-coke based catalyst to the biomass raw material is 1:5-10.

[0030] In step 1) or step 3), the microwave-assisted pyrolysis is carried out in an inert atmosphere.

[0031] Preferably, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0032] In addition, unless otherwise specified, any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0033] The beneficial effects of the present invention are as follows:

[0034] (1) The present invention can improve the shortcomings of traditional electric heating hydrogen production, such as slow heating rate and high energy dissipation, through the microwave effect. By coupling with bio-semi-coke-based catalysts, it can achieve the dual effects of microwave absorption and rapid catalysis.

[0035] (2) The present invention utilizes acid-washed bio-semi-coke to reduce bio-oil yield and increase gas yield. For example, the content of high-value-added components (hydrogen and carbon monoxide) in the syngas is increased, while the content of greenhouse gases (carbon dioxide and methane) is significantly reduced. Different acids used in the acid-washing process can further regulate the distribution of oil and gas products, the selectivity of gas products, and the selectivity of high-value-added products (furans, phenols, ketones, aromatics, etc.) in the bio-oil.

[0036] (3) The cathode materials of waste lithium-ion batteries are rich in metal elements with extremely high catalytic activity, such as iron, nickel, cobalt, and manganese. Loading them on bio-coke through acid leaching can improve the absorption and catalytic capabilities of the coke, while further changing the distribution of oil and gas products and the selectivity of high value-added products. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] Figure 1 Shown is a structural diagram of the microwave reaction device used in the present invention;

[0039] In the figure, 1-microwave reaction chamber, 2-control panel, 3-quartz reactor, 5-gas carrier device, 6-pyrolysis gas collection device.

[0040] Figure 2 The solid-liquid-gas product distribution histograms of Test Examples 1-2 and Examples 1-5 are shown.

[0041] Figure 3 The liquid product distribution histograms of Test Examples 1-2 and Examples 1-5 are shown.

[0042] Figure 4 The gas distribution histograms of Test Examples 1-2 and Examples 1-5 are shown. DETAILED DESCRIPTION

[0043] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the following detailed description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0044] The microwave reaction devices used in the following test examples or embodiments are Figure 1 The device shown comprises a microwave reaction chamber 1, a control panel 2, a quartz reactor 3, a gas carrier device 5, and a pyrolysis gas collecting device 6, wherein the quartz reactor 3 is used to place biomass raw materials and a bio-coke-based catalyst 4.

[0045] Test Example 1

[0046] The rice straw powder was mixed with 12 mesh granular silicon carbide at a mass ratio of 1:10 and then loaded into the Figure 1 In a quartz reactor, argon was introduced for 10 minutes to exhaust the air, and then pyrolysis was carried out under 600W microwave irradiation for 15 minutes to obtain bio-oil, synthesis gas and straw semi-coke in the proportions of 30%, 30% and 40% respectively (e.g. Figure 2 GC / MS peak area showed that the furans in the bio-oil were 24.74%, phenols were 48.04%, and ketones were 13.68% (e.g. Figure 3 ); 24.32% hydrogen, 37.59% carbon dioxide, 22.12% carbon monoxide, 8.62% methane and the remainder C2 to C6 gaseous organic matter (such as Figure 4 ).

[0047] Test Example 2

[0048] The rice straw powder was mixed with the rice straw semi-coke obtained directly in Experimental Example 1 (without any modification) at a mass ratio of 5:2 and then loaded into the Figure 1 In a quartz reactor, nitrogen was introduced for 10 minutes to exhaust the air, and then pyrolysis was carried out under 400W microwave irradiation for 15 minutes to obtain bio-oil, synthesis gas and biochar in the proportions of 19.7%, 41.7% and 38.6%, respectively (e.g. Figure 2 GC / MS peak area analysis revealed that the bio-oil contained 19.5% furans, 60.64% phenols, and 16.39% ketones (e.g. Figure 3 ), the synthesis gas contains 41.33% hydrogen, 23.54% carbon dioxide, 29.29% carbon monoxide, 4.67% methane and the remainder C2 to C6 gaseous organic matter (such as Figure 4 ).

[0049] Example 1

[0050] The straw semi-coke directly obtained in Experimental Example 1 was acid-washed with 1 mol / L dilute hydrochloric acid at 400 rpm for 6 hours, filtered, and then directly microwave calcined (power 400 W, 10 minutes, argon atmosphere) to obtain a hydrochloric acid-modified bio-semi-coke-based catalyst.

[0051] The rice straw powder and the bio-semi-coke-based catalyst were mixed at a mass ratio of 2:1 and loaded into the Figure 1 In a quartz reactor, argon was introduced for 10 minutes to expel air, and then pyrolysis was carried out under 480W microwave irradiation for 20 minutes to obtain bio-oil, synthesis gas and biochar in the proportions of 21%, 39.9% and 39.1%, respectively (e.g. Figure 2 The bio-oil contains 55.57% furans (of which 45.98% furfural), 23.18% phenols, 6.16% ketones (such as Figure 3 , GC / MS peak area), syngas contains 41.50% hydrogen, 11.43% carbon dioxide, 42.72% carbon monoxide, 3.31% methane and the remainder C2 to C6 gaseous organic matter (such as Figure 4 ).

[0052] Example 2

[0053] The straw semi-coke directly obtained in Experimental Example 1 was acid-washed with 2 mol / L oxalic acid at 400 rpm for 6 hours (solid-liquid ratio 2:25), filtered and then directly microwave calcined (power 500 W, 10 minutes, argon atmosphere) to obtain an oxalic acid-modified bio-semi-coke-based catalyst.

[0054] The rice straw powder and the bio-semi-coke-based catalyst were mixed at a mass ratio of 4:3 and loaded into the Figure 1 In a quartz reactor, nitrogen was introduced for 10 minutes to exhaust the air, and then pyrolysis was carried out under 280W microwave irradiation for 15 minutes to obtain bio-oil, synthesis gas and biochar in the proportions of 15.1%, 50.7% and 34.2%, respectively (e.g. Figure 2 The bio-oil contains 26.29% furans, 59.59% phenols, and 8.16% ketones (e.g. Figure 3 , GC / MS peak area), syngas contains 48.10% hydrogen, 7.63% carbon dioxide, 39.85% carbon monoxide, 4.35% methane and the remainder C2 to C6 gaseous organic matter (such as Figure 4 ).

[0055] Example 3

[0056] The straw semi-coke directly obtained in Experimental Example 1 was acid-washed with 1 mol / L phosphoric acid at 400 rpm for 6 hours (solid-liquid ratio 2:25), filtered and then directly microwave calcined (power 400 W, 10 minutes, argon atmosphere) to obtain an oxalic acid-modified bio-semi-coke-based catalyst.

[0057] The rice straw powder and the bio-semi-coke-based catalyst were mixed at a mass ratio of 3:2 and loaded into the Figure 1 In a quartz reactor, argon was introduced for 10 minutes to expel air, and then pyrolysis was carried out under 400W microwave irradiation for 20 minutes to obtain bio-oil, synthesis gas and biochar in the proportions of 16.7%, 49.6% and 33.7%, respectively (e.g. Figure 2 The bio-oil contains 57.72% furans (of which 46.06% furfural), 24.1% phenols, 5.61% ketones (such as Figure 3 , GC / MS peak area), the synthesis gas contains 41.87% hydrogen, 13.13% carbon dioxide, 38.15% carbon monoxide, 8.75% methane and the remainder C2 to C6 gaseous organic matter (such as Figure 4 ).

[0058] Example 4

[0059] The straw semi-coke obtained directly from Experimental Example 1 was acid-washed with 2 mol / L oxalic acid at 400 rpm for 6 hours (solid-to-liquid ratio 2:25). After filtration, it was directly microwave-calcined (power 400 W, 10 minutes, argon atmosphere) to obtain a semi-coke-based catalyst support. Waste lithium iron phosphate was leached with oxalic acid (solid-to-liquid ratio 1:50, stirring speed 400 rpm, 1 hour) to obtain an acid leachate.

[0060] The acid leaching liquid was mixed with the semi-coke-based catalyst carrier, dried, and then microwave calcined (power 400W, 10 minutes, argon atmosphere) to obtain a waste lithium iron phosphate-modified bio-semi-coke-based catalyst.

[0061] The rice straw powder and the semi-coke-based catalyst were mixed at a mass ratio of 2:1 and loaded into the Figure 1 In a quartz reactor, argon was introduced for 10 minutes to expel air, and then pyrolysis was carried out under 480W microwave irradiation for 20 minutes to obtain bio-oil, synthesis gas and biochar in the proportions of 11.6%, 50.2% and 38.2%, respectively (e.g. Figure 2 The bio-oil contains 29.39% furans, 50.54% phenols, and 10.44% ketones (e.g. Figure 3 , GC / MS peak area), syngas contains 42.30% hydrogen, 10.61% carbon dioxide, 41.77% carbon monoxide, 4.12% methane and the remainder C2 to C6 gaseous organic matter (such as Figure 4 ).

[0062] Example 5

[0063] The straw semi-coke obtained directly from Experimental Example 1 was acid-washed with 2 mol / L oxalic acid at 400 rpm for 6 hours (solid-to-liquid ratio 2:25), filtered, and then microwave-calcined (400 W power, 10 minutes, argon atmosphere) to obtain a semi-coke-based catalyst support. Waste lithium cobalt oxide was leached with oxalic acid (solid-to-liquid ratio 3:50, 400 rpm, 1 hour) to obtain an acid leachate.

[0064] The acid leaching liquid was mixed with the carrier, dried, and then microwave calcined (power 400 W, 10 minutes, argon atmosphere) to obtain a waste lithium cobalt oxide modified bio-semi-coke-based catalyst.

[0065] The rice straw powder and the bio-semi-coke-based catalyst were mixed at a mass ratio of 3:2 and loaded into the Figure 1 In a quartz reactor, argon was introduced for 10 minutes to expel air, and then pyrolysis was carried out under 600W microwave irradiation for 25 minutes to obtain bio-oil, synthesis gas and biochar in the proportions of 13.8%, 50% and 36.2%, respectively (e.g. Figure 2 The bio-oil contains 18.79% furans, 62.07% phenols, and 10.68% ketones (e.g. Figure 3, GC / MS peak area), syngas contains 46.71% hydrogen, 10.61% carbon dioxide, 37.32% carbon monoxide, 4.06% methane and the remainder C2 to C6 gaseous organic matter (such as Figure 4 ).

[0066] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for directional control of biomass microwave-assisted pyrolysis product distribution using a bio-coke-based catalyst, characterized in that: The following steps are involved: 1) Microwave-assisted pyrolysis of biomass to obtain biochar; 2) The bio-semi-coke is acid-washed and loaded with active metals to obtain a bio-semi-coke-based catalyst; 3) The bio-coke-based catalyst and biomass raw materials are subjected to microwave-assisted pyrolysis to obtain bio-oil, synthesis gas and biochar; 4) adjusting the type of the acid and / or active metal to obtain bio-oil, syngas, and biochar with different compositions and distribution ratios; Wherein, in step 2), the active metal is derived from the positive electrode of a waste lithium-ion battery; The acid solution is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, oxalic acid and citric acid; the concentration of the acid solution is in the range of 0.5 mol / L to 5 mol / L; the pickling is carried out under stirring for 5 to 10 hours; The waste lithium-ion battery positive electrode is one or more of waste lithium iron phosphate, waste lithium nickel cobalt manganese oxide and waste lithium cobalt oxide; In step 2), loading the active metal specifically comprises the following steps: obtaining an acid leaching solution of the positive electrode of the waste lithium-ion battery, impregnating the acid-washed bio-semi-coke with the acid leaching solution, drying, and microwave calcining; The microwave calcination conditions are as follows: the microwave power is 360-600W, and the microwave calcination time is 5-20min; The solid-liquid ratio of the bio-semi-coke and the acid leaching solution is 1g:10-30mL.

2. The method according to claim 1, characterized in that In step 1), the microwave-assisted pyrolysis is carried out in a fixed bed of an inert microwave absorbent.

3. The method according to claim 2, characterized in that The inert microwave absorber is silicon carbide.

4. The method according to claim 3, characterized in that In the fixed bed of silicon carbide, the laying thickness of silicon carbide is 2-8 cm; and the particle size of the silicon carbide is 10-20 mesh.

5. The method according to claim 2, characterized in that The mass ratio of the biomass to the inert microwave absorber is 1:5-20.

6. The method according to claim 1, characterized in that In step 1) or step 3), the microwave-assisted pyrolysis conditions are: microwave power is 240-800 W, and the pyrolysis time is 10-30 minutes.

7. The method according to claim 1, characterized in that The mass ratio of the bio-semi-coke based catalyst to the biomass raw material is 1:5-10.

8. The method according to claim 1, characterized in that In step 1) or step 3), the microwave-assisted pyrolysis is carried out in an inert atmosphere.

9. The method according to claim 8, characterized in that The inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

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