Efficient catalyst for catalytic cracking of biomass gasification tar as well as preparation method and application of efficient catalyst

Abstract

The invention provides a high-efficiency catalyst for catalytic cracking of biomass gasification tar as well as a preparation method and application of the high-efficiency catalyst. The high-efficiency catalyst for catalytic cracking of biomass gasification tar comprises a carrier, an active component and an auxiliary agent, wherein the carrier is a hierarchical porous molecular sieve; the active component is a transition metal oxide, and the loading capacity of the active component is 5-20wt%; the additive is a rare earth element, and the addition amount of the additive is 1-5wt%. The efficient catalyst disclosed by the invention can be used for catalytic cracking of tar at a relatively low temperature, has the advantages of high activity, good stability, long service life, strong adaptability and the like, has high tar conversion rate and H2 selectivity when being used for catalytic cracking of biomass gasification tar, not only remarkably reduces the tar content in gasified gas, but also greatly improves the quality of produced gas.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass energy, and in particular to a high-efficiency catalyst for catalytic cracking of biomass gasification tar, and a preparation method and application thereof. Background Art

[0002] Biomass gasification technology is an effective way to convert biomass into clean combustible gas. However, the tar produced during the gasification process can clog pipelines, corrode equipment, and reduce gas quality, seriously restricting the promotion and application of biomass gasification technology.

[0003] Catalytic cracking technology is an effective method for removing tar from biomass gasification. Its key lies in the development of efficient and stable catalysts. Currently, commonly used catalysts for the catalytic cracking of biomass gasification tar include natural mineral catalysts, alkali metal catalysts, and nickel-based catalysts. However, these catalysts generally suffer from issues such as high cracking temperatures, low catalytic activity, susceptibility to carbon deposition and deactivation, short service life, poor adaptability, and difficulty cracking tar with high moisture content.

[0004] In addition, existing biomass gasification technology has defects such as low carbon conversion rate and gasification efficiency, and low concentrations of carbon monoxide and hydrogen in the synthesis gas.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-efficiency catalyst for catalytic cracking of biomass gasification tar, as well as its preparation method and application. The high-efficiency catalyst has the advantages of low catalytic cracking temperature, high reaction activity, good stability, long service life, good adaptability, and the ability to efficiently process high-water content tar.

[0007] The present invention provides a high-efficiency catalyst for catalytic cracking of biomass gasification tar, comprising a carrier, an active component and an auxiliary agent; wherein the carrier is a multi-stage pore molecular sieve; the active component is a transition metal oxide, and the loading amount of the active component is 5-20wt%; the auxiliary agent is a rare earth element, and the addition amount of the auxiliary agent is 1-5wt%.

[0008] The multi-level pore molecular sieve is at least one selected from the group consisting of multi-level pore ZSM-5 molecular sieve, multi-level pore MCM-41 molecular sieve and multi-level pore SBA-15 molecular sieve.

[0009] Furthermore, the specific surface area of ​​the multi-stage pore molecular sieve is 500-1500m 2 / g, pore volume of 0.4-1.5cm 3 / g, with an external surface area of ​​100-800m 2 / g, and the total acid content is 5.0-7.0mmol / g. The multi-level pore molecular sieve contains micropores with a pore size of <2nm and mesopores with a pore size of 2-50nm, with the mesopores accounting for 40-60%.

[0010] The above-mentioned multi-level pore molecular sieve has the following advantages: 1) High specific surface area + large pore volume: improves the adsorption and mass transfer efficiency of reactants; 2) Bimodal pore size distribution: takes into account both shape-selective catalysis and diffusion performance; 3) Strong acid sites + high thermal stability: enhances reaction activity and life; 4) Hierarchical connectivity: solves the diffusion bottleneck of macromolecular reactions; 5) Adjustable loading capacity: adapts to different reaction requirements (such as biomass conversion, heavy oil cracking, etc.).

[0011] The transition metal oxide is at least one selected from nickel oxide, cobalt oxide and iron oxide.

[0012] The rare earth element is selected from one of cerium, lanthanum and neodymium.

[0013] The present invention also provides a method for preparing the above-mentioned high-efficiency catalyst for catalytic cracking of biomass gasification tar, comprising the following steps:

[0014] S1: Immersing the support in a mixed solution containing a transition metal salt and a rare earth metal salt, stirring uniformly, to prepare a precursor solution;

[0015] S2: Drying and calcining the precursor solution to obtain a high-efficiency catalyst for catalytic cracking of biomass gasification tar.

[0016] In step S1, the transition metal salt is selected from at least one of nickel nitrate, cobalt nitrate, and iron nitrate, and the rare earth metal salt is selected from at least one of cerium nitrate, lanthanum nitrate, and neodymium nitrate. The mass content of the transition metal salt in the mixed solution is 0.1-0.15 g / mL, and the mass content of the rare earth metal salt is 0.02-0.03 g / mL. More specifically, the mass ratio of the carrier, transition metal salt, and rare earth metal salt is 10:(1.5-3):(0.3-0.7).

[0017] In step S2, the drying temperature is 80-120°C, and the drying time is 2-6 hours; the roasting temperature is 400-600°C, for example, 450-550°C, and the roasting time is 2-4 hours.

[0018] The present invention also provides the use of the high-efficiency catalyst for catalytic cracking of biomass gasification tar in the catalytic cracking of biomass gasification tar.

[0019] Furthermore, the catalytic cracking temperature is 450-600°C and the hourly space velocity (GHSV) is 1000-3000h -1 .

[0020] Furthermore, the preparation method of biomass gasification tar includes:

[0021] A) feeding biomass raw materials and gasifying agent into a gasifier for gasification;

[0022] B) Separate the synthesis gas produced by gasification.

[0023] Specifically, the gasifier is equipped with a quartz sand fluidized bed. The quartz sand used in this fluidized bed has the following particle size distribution: 8-12% of the sand has a particle size of 0.3 mm or less and less than 0.5 mm; 45-55% of the sand has a particle size of 0.5 mm or less and less than 0.6 mm; and 35-45% of the sand has a particle size of 0.6 mm or less and less than 0.8 mm. This particle size distribution in the fluidized bed ensures uniform heating within the gasifier, improving gasification efficiency and syngas quality.

[0024] The gasifying agent can be air; specifically, it includes pure oxygen and water vapor, with a pure oxygen equivalence ratio (the ratio of the amount of oxygen provided during the gasification process to the theoretical amount of oxygen required for complete combustion of the biomass feedstock) of 0.2-0.3, and a water vapor ratio (the mass ratio of the water vapor provided during the gasification process to the biomass feedstock) of 0.3-0.5. Using pure oxygen and water vapor as gasifying agents can significantly increase the concentrations of carbon monoxide and hydrogen in the syngas. The gasification temperature can be 700-800°C, and the gasification time can be 6-20 seconds.

[0025] Compared with the prior art, the present invention has at least the following advantages:

[0026] 1. The high-efficiency catalyst provided by the present invention uses a multi-level pore molecular sieve as a carrier, has a large specific surface area and a rich pore structure, which is conducive to the diffusion of reactants and products, improves the activity of the catalyst, and the hierarchical pore design solves the bottleneck of macromolecular diffusion and is suitable for the cracking needs of heavy tar.

[0027] 2. The high-efficiency catalyst provided by the present invention uses transition metal oxides as active components and adds rare earth elements as additives. It can catalytically crack tar at a lower temperature and effectively improve the activity, stability and service life of the catalyst. It has high adaptability when used for catalytic cracking of biomass gasification tar, and can solve problems such as the difficulty of cracking tar with high water content. It has high conversion rate and H2 selectivity, significantly reduces the tar content in the gasification gas, and improves the gas production quality.

[0028] 3. The preparation method of the high-efficiency catalyst provided by the present invention is simple, easy, low-cost, and easy to industrialize. It has the advantages of high conversion rate (>93%) and low carbon deposition rate (reduced by 64-75%) in biomass tar cracking, significantly improving gas production quality and service life (>2000h), and reducing operating costs.

[0029] 4. The present invention also provides a biomass gasification method, which uses pure oxygen and water vapor as gasifying agents, can effectively improve the carbon conversion rate and gasification efficiency. The total concentration of carbon monoxide and hydrogen in the synthesis gas can be increased to more than 65%, greatly improving the quality of the biomass gasification synthesis gas. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0031] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0032] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] Example 1

[0034] The steps for preparing the high-efficiency catalyst for catalytic cracking of biomass gasification tar in this embodiment are as follows:

[0035] 1) Immerse 10 g of hierarchical ZSM-5 molecular sieve in 25 mL of a mixed solution containing 2.5 g of nickel nitrate and 0.5 g of cerium nitrate, and stir evenly to prepare a precursor solution;

[0036] 2) drying the precursor solution at 100° C. for 4 h;

[0037] 3) The dried product was calcined at 500° C. for 3 h under a nitrogen atmosphere to obtain a high-efficiency catalyst for catalytic cracking of biomass gasification tar.

[0038] The multi-level pore ZSM-5 molecular sieve used in this example was purchased from Luoyang Jianlong Micro-Nano New Materials Co., Ltd., and its quality parameters are shown in Table 1.

[0039] Table 1 Quality parameters of multi-level pore ZSM-5 molecular sieve

[0040] Example 2

[0041] The steps for preparing the high-efficiency catalyst for catalytic cracking of biomass gasification tar in this embodiment are as follows:

[0042] 1) Immerse 10 g of multi-level pore MCM-41 molecular sieve in 25 mL of a mixed solution containing 1.5 g of cobalt nitrate and 0.3 g of lanthanum nitrate, and stir evenly to prepare a precursor solution;

[0043] 2) drying the precursor solution at 80° C. for 6 h;

[0044] 3) The dried product was calcined at 450° C. for 4 h under a nitrogen atmosphere to obtain a high-efficiency catalyst for catalytic cracking of biomass gasification tar.

[0045] The multi-level pore MCM-41 molecular sieve used in this example was purchased from Xi'an Qiyue Biotechnology Co., Ltd., and its quality parameters are shown in Table 2.

[0046] Table 2 Quality parameters of multi-stage pore MCM-41 molecular sieve

[0047] parameter Multi-level pore MCM-41 molecular sieve Specific surface area (BET) <![CDATA[500-1500m 2 / g(micropore + mesopore synergistic contribution)]]> Kong Rong (BJH) <![CDATA[0.5-1.5cm 3 / g (mesopores account for 40-60%) Pore ​​size distribution Bimodal distribution: micropores (0.5-1nm) + mesopores (2-10nm) External surface (SBET) <![CDATA[600-800m 2 / g(Mesopores contribute significantly)]]> Acid strength (Hammett) <![CDATA[H0 = -8 to -10.0 (increase in the proportion of strong acid sites)]]>

[0048] Example 3

[0049] The steps for preparing the high-efficiency catalyst for catalytic cracking of biomass gasification tar in this embodiment are as follows:

[0050] 1) Immerse 10 g of hierarchical SBA-15 molecular sieve in 25 mL of a mixed solution containing 3 g of ferric nitrate and 0.7 g of neodymium nitrate, and stir evenly to prepare a precursor solution;

[0051] 2) drying the precursor solution at 120°C for 2 hours;

[0052] 3) The dried product was calcined at 550° C. for 2 h under a nitrogen atmosphere to obtain a high-efficiency catalyst for catalytic cracking of biomass gasification tar.

[0053] The multi-stage pore SBA-15 molecular sieve used in this example was purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., and its quality parameters are shown in Table 3.

[0054] Table 3 Quality parameters of multi-stage pore SBA-15 molecular sieve

[0055] parameter Multi-stage pore SBA-15 molecular sieve Specific surface area (BET) <![CDATA[600-1200m 2 / g(micropore + mesopore synergistic contribution)]]> Kong Rong (BJH) <![CDATA[0.4-0.45cm 3 / g (mesopores account for 40-60%) Pore ​​size distribution Bimodal distribution: micropores (0.5-1nm) + mesopores (5-30nm) External surface (SBET) <![CDATA[100-400m 2 / g(mesopores contribute significantly)]]> Acid strength (Hammett) <![CDATA[Weak B acid (H0≈ -8)]]>

[0056] Comparative Example 1

[0057] Except that cerium nitrate was not added, the rest was the same as in Example 1.

[0058] Comparative Example 2

[0059] The process is the same as that of Example 1 except that ordinary ZSM-5 molecular sieve (single-peak distribution, containing only 0.5-1 nm micropores and no mesopores) is used instead of the multi-level pore ZSM-5 molecular sieve.

[0060] Test Example 1

[0061] The catalysts of the embodiments and comparative examples were used to carry out catalytic cracking of biomass gasification tar, as follows:

[0062] The straw was crushed to a particle size of ≤100 mm and then fed into a gasifier. Air was introduced into the gasifier as a gasifying agent for gasification. The air equivalence ratio was 0.2, the gasification temperature was 750°C, and the gasification time was 10 s.

[0063] The gasified syngas is subjected to two-stage cyclone separation. The moisture content of the separated syngas is 8% and the tar content is 1200 mg / Nm 3 .

[0064] The catalysts of the embodiments and the control examples were used to carry out tar cracking on the separated synthesis gas. The tar cracking temperature was 600°C and the hourly space velocity (GHSV) was 1000h -1 .

[0065] The results of the catalytic cracking reaction of biomass gasification tar are shown in Table 4, and the main reaction products and their contents are shown in Table 5.

[0066] Table 4 Biomass gasification tar catalytic cracking reaction results

[0067] catalyst Tar conversion rate (%) Carbon deposit amount (g / (g·h)) Example 1 93.54 0.051 Example 2 95.87 0.035 Example 3 94.29 0.042 Comparative Example 1 91.33 0.138 Comparative Example 2 85.47 0.080

[0068] Table 5 Main products and contents of biomass gasification tar catalytic cracking reaction

[0069] catalyst hydrogen carbon monoxide methane carbon dioxide Example 1 12.46％ 16.17％ 5.98％ 13.65％ Example 2 12.90％ 16.78％ 5.67％ 14.04％ Example 3 13.43％ 17.56％ 6.05％ 13.75％ Comparative Example 1 9.41％ 13.16％ 3.14％ 16.14％ Comparative Example 2 8.56％ 12.65％ 2.03％ 17.54％

[0070] Test Example 2

[0071] The catalytic cracking reaction of biomass gasification tar using the catalysts of Example 1 and Comparative Example 2 is as follows:

[0072] Quartz sand is fed into the gasifier to form a fluidized bed. The particle size distribution of the quartz sand is as follows: the component with a particle size of 0.3 mm ≤ < 0.5 mm accounts for 10%, the component with a particle size of 0.5 mm ≤ < 0.6 mm accounts for 50%, and the component with a particle size of 0.6 mm ≤ ≤ 0.8 mm accounts for 40%. The volume of the quartz sand is 3% of the volume of the gasifier.

[0073] The straw is crushed into a particle size of ≤100 mm and then fed into a gasifier. Pure oxygen and water vapor are introduced into the gasifier as gasifying agents for gasification. The pure oxygen equivalent ratio is 0.2, the water vapor ratio is 0.3, the gasification temperature is 750°C, and the gasification time is 10 s.

[0074] The gasified synthesis gas was subjected to two-stage cyclone separation. The hydrogen content of the separated synthesis gas was 30.54%, the carbon monoxide content was 36.12%, the water content was 20%, and the tar content was 1000 mg / Nm 3 .

[0075] The catalysts of Example 1 and Comparative Example 2 were used to perform tar cracking on the separated synthesis gas. The tar cracking temperature was 600°C and the hourly space velocity (GHSV) was 1000h -1 .

[0076] The catalytic cracking effect is shown in Table 6.

[0077] Table 6 Main composition of synthesis gas and catalytic cracking effect

[0078] hydrogen carbon monoxide Hydrogen selectivity Example 1 31.86％ 37.58％ 78.8％ Comparative Example 2 - - 64.9％

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-efficiency catalyst for catalytic cracking of biomass gasification tar, characterized in that: It includes a carrier, an active component and an auxiliary agent; wherein the carrier is a multi-level pore molecular sieve; the active component is a transition metal oxide, and the loading amount of the active component is 5-20wt%; the auxiliary agent is a rare earth element, and the addition amount of the auxiliary agent is 1-5wt%.

2. The high efficiency catalyst according to claim 1, characterized in that The multi-level pore molecular sieve is at least one selected from the group consisting of multi-level pore ZSM-5 molecular sieve, multi-level pore MCM-41 molecular sieve and multi-level pore SBA-15 molecular sieve.

3. The high efficiency catalyst according to claim 1, characterized in that The transition metal oxide is at least one selected from nickel oxide, cobalt oxide and iron oxide.

4. The high efficiency catalyst according to claim 1, characterized in that The rare earth element is selected from one of cerium, lanthanum and neodymium.

5. The high efficiency catalyst according to claim 2, characterized in that The multi-level pore molecular sieve contains micropores with a pore size of <2nm and mesopores with a pore size of 2-50nm, with the mesopores accounting for 40-60%.

6. The method for preparing a high-efficiency catalyst for catalytic cracking of biomass gasification tar according to any one of claims 1 to 5, characterized in that: The steps include: S1: Immersing the support in a mixed solution containing a transition metal salt and a rare earth metal salt, stirring uniformly, to prepare a precursor solution; S2: Drying and calcining the precursor solution to obtain a high-efficiency catalyst for catalytic cracking of biomass gasification tar.

7. The preparation method according to claim 6, characterized in that In step S1, the transition metal salt is selected from at least one of nickel nitrate, cobalt nitrate and iron nitrate, and the rare earth metal salt is selected from at least one of cerium nitrate, lanthanum nitrate and neodymium nitrate.

8. The preparation method according to claim 6, characterized in that In step S2, the drying temperature is 80-120° C., and the drying time is 2-6 hours; the roasting temperature is 400-600° C., and the roasting time is 2-4 hours.

9. Use of the high-efficiency catalyst for catalytic cracking of biomass gasification tar according to any one of claims 1 to 5 in catalytic cracking of biomass gasification tar.

10. The use according to claim 9, characterized in that The catalytic cracking temperature is 450-600℃.

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