Steel slag-based catalyst as well as preparation method and application thereof

Abstract

The invention provides a steel slag-based catalyst as well as a preparation method and application thereof, and belongs to the technical field of solid waste treatment. The method comprises the following steps: activating steel slag to prepare activated steel slag; the activated steel slag and nickel nitrate hexahydrate are placed in water for dipping treatment, then calcination treatment is conducted, and the steel slag-based catalyst is prepared. The steel slag-based catalyst prepared by the preparation method disclosed by the invention is large in specific surface area, has excellent anti-sintering performance, has advantages in the aspects of tar cracking and reforming hydrogen production, and can remarkably reduce the yield of a by-product tar in the biomass gasification and pyrolysis processes.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste treatment, and in particular to a steel slag-based catalyst and a preparation method and application thereof. Background Art

[0002] With the rapid economic development and the promotion of the concept of sustainable development, the efficient and safe use of biomass energy has become the only way to deal with energy problems. At present, biomass gasification and pyrolysis are the most abundant, low-cost and CO 2 Neutral biomass resources are an increasingly attractive method for producing fuel gas. However, tar is a byproduct produced during biomass gasification and pyrolysis. During the gasification process, tar not only reduces the yield and efficiency of gasification, but also blocks pipes and filters and causes corrosion of downstream equipment. In contrast, catalytic reforming of tar is considered to be the most promising biomass energy utilization technology that chemically converts tar into gas at relatively low temperatures.

[0003] Catalysts are key to the catalytic reforming process, which not only affects tar decomposition but also the overall economic feasibility of the process. Therefore, the development of effective and low-cost catalysts has become increasingly attractive. Metal-based catalysts, such as Ni-based catalysts, Fe-based catalysts, and alkali metal catalysts, have been widely studied due to their high catalytic activity and operational availability. Therefore, natural minerals and industrial wastes, which are usually rich in metal oxides, have also been studied as effective and low-cost catalysts. For example, Ashok et al. used municipal solid waste incineration bottom ash as a catalyst support material and achieved high catalytic activity for steam reforming of biomass tar at 700-800 °C. Zou et al. selected natural limonite as a catalyst to catalytically crack toluene, a typical model compound of tar, and found that toluene can be decomposed into H 2 , CO, CH 4 and CO, loading nickel can further improve the catalytic performance.

[0004] Steel slag is a byproduct of the steelmaking process and a cheap industrial waste. The main utilization of steel slag is the preparation of sintering solvents, roadbed materials in road construction, and the preparation of cement and concrete. However, a large part of steel slag is still stored in the open air, and the dust and heavy metal pollution caused by it are harmful to the human body and the ecological environment, and its high-value utilization is still in its early stages. Steel slag contains a large amount of metal compounds such as iron, magnesium, aluminum, and calcium, and has the potential to be used as a catalyst for biomass tar reforming. Therefore, it is of great significance to study a steel slag-based catalyst and its preparation method, and use it in tar cracking and reforming to produce hydrogen. Summary of the invention

[0005] The object of the present invention is to provide a steel slag-based catalyst and a preparation method and application thereof, so as to solve the problem in the prior art that steel slag cannot be processed and the high yield of byproduct - tar in the process of biomass gasification and pyrolysis.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a steel slag-based catalyst, comprising the following steps:

[0008] S1: activating the steel slag to obtain activated steel slag;

[0009] S2: The activated steel slag and nickel nitrate hexahydrate are placed in water for impregnation treatment, and then calcined to obtain a steel slag-based catalyst.

[0010] Preferably, in step S1, the steel slag is converter steel slag; and the steel slag is firstly washed and dried before the activation treatment.

[0011] Preferably, the washing is performed with water; the drying temperature is 100-120° C., and the drying time is 10-14 hours.

[0012] Preferably, in step S1, the heating rate during the activation treatment is 8-12°C / min, the temperature of the activation treatment is 800-1000°C, and the time of the activation treatment is 2-4h.

[0013] Preferably, in step S2, the mass ratio of activated steel slag to nickel nitrate hexahydrate is 80-90:15-80.

[0014] Preferably, in step S2, the immersion treatment time is 4 to 6 hours.

[0015] Preferably, in step S2, the heating rate during calcination is 8-12°C / min, the calcination temperature is 500-700°C, and the calcination time is 2-4h.

[0016] The present invention also provides a steel slag-based catalyst prepared by the preparation method of the steel slag-based catalyst described above, wherein the steel slag-based catalyst is mainly composed of calcium oxide, nickel oxide, ferric oxide, magnesium oxide and aluminum oxide; the mass of the nickel oxide accounts for 5 to 20% of the mass of the steel slag-based catalyst.

[0017] The present invention also provides an application of the steel slag-based catalyst described above in tar cracking and reforming to produce hydrogen.

[0018] Beneficial effects of the present invention:

[0019] (1) The steel slag-based catalyst prepared by the preparation method of the present invention has a large specific surface area, has advantages in tar cracking and reforming hydrogen production, and can significantly reduce the yield of tar, a by-product in the process of biomass gasification and pyrolysis.

[0020] (2) The steel slag-based catalyst of the present invention is prepared by activating steel slag and then loading nickel oxide for modification. The calcium oxide in the steel slag-based catalyst serves as an adsorption component, ferric oxide and nickel oxide serve as active components, magnesium oxide serves as an auxiliary agent, and aluminum oxide serves as an inert component. The inert component aluminum oxide hinders the active components NiO and Fe in the high-temperature catalytic process. 2 O 3 , and the sintering and agglomeration of the adsorbed component CaO, so the steel slag-based catalyst has excellent anti-sintering performance.

[0021] (3) The present invention selects steel slag to prepare a catalyst for catalytic reforming of tar to produce hydrogen. On the one hand, it can significantly enhance the cracking of tar to produce more synthesis gas, and on the other hand, it is conducive to the high-value utilization of industrial solid waste. Using steel slag as a catalyst for the development of biomass energy is of great significance to promoting the green transformation of the waste-producing industry and promoting the comprehensive utilization of industrial solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a comparison chart of tar, biochar and gas content after performance verification of the steel slag-based catalysts of Example 1, Comparative Examples 3 and 4, the activated alumina of Comparative Example 1 and the activated steel slag of Comparative Example 2;

[0023] Figure 2 It is a comparison chart of the contents of various gases after the performance verification of the steel slag-based catalysts of Example 1, Comparative Examples 3 and 4, the activated alumina of Comparative Example 1 and the activated steel slag of Comparative Example 2;

[0024] Figure 3 It is a comparison chart of the yields of various gases after performance verification of the steel slag-based catalysts of Example 1, Comparative Examples 3 and 4, the activated alumina of Comparative Example 1, and the activated steel slag of Comparative Example 2;

[0025] Figure 4 This is a comparison chart of tar, biochar and gas products when different contents of nickel oxide are loaded;

[0026] Figure 5 This is a comparison chart of the contents of various gases when different contents of nickel oxide are loaded;

[0027] Figure 6 This is a comparison chart of the yields of various gases when loaded with different contents of nickel oxide. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a steel slag-based catalyst, comprising the following steps:

[0029] S1: activating the steel slag to obtain activated steel slag;

[0030] S2: The activated steel slag and nickel nitrate hexahydrate are placed in water for impregnation treatment, and then calcined to obtain a steel slag-based catalyst.

[0031] In the present invention, in step S1, the steel slag is converter steel slag; and the steel slag is firstly washed and dried before the activation treatment.

[0032] The main components and contents of the converter slag used in the present invention are: CaO 40-45%, Fe 2 O 3 25~30%、SiO 2 15~20%, MgO 5~10%, Al 2 O 3 1-8%, trace oxides, the trace oxides include P 2 O 5 , K 2 O, ZnO, MnO, TiO 2 、V 2 O 5 The total content of trace oxides is 5-10%.

[0033] In the present invention, the washing is performed with water; the drying temperature is 100-120° C., preferably 105-115° C.; the drying time is 10-14 hours, preferably 11-13 hours, and more preferably 12 hours.

[0034] In the present invention, in step S1, the heating rate during the activation treatment is 8-12°C / min, preferably 9-11°C / min, and more preferably 10°C / min; the temperature of the activation treatment is 800-1000°C, preferably 800°C, 900°C, and 1000°C; the time of the activation treatment is 2-4h, preferably 3h.

[0035] In the present invention, in step S2, the mass ratio of activated steel slag to nickel nitrate hexahydrate is 80-90:15-80, preferably, more preferably.

[0036] In the present invention, the volume ratio of the activated slag to water is 80-90 g:30-50 mL, preferably 80-90 g:40 mL.

[0037] In the present invention, in step S2, the immersion treatment time is 4 to 6 hours, preferably 5 hours.

[0038] In the present invention, in step S2, the heating rate during calcination is 8-12°C / min, preferably 9-11°C / min, and more preferably 10°C / min. The calcination temperature is 500-700°C, preferably 600°C, and the calcination time is 2-4h, preferably 3h.

[0039] The present invention also provides a steel slag-based catalyst prepared by the preparation method of the steel slag-based catalyst described above, wherein the steel slag-based catalyst is mainly composed of calcium oxide, nickel oxide, ferric oxide, magnesium oxide and aluminum oxide; the mass of the nickel oxide accounts for 5 to 20% of the mass of the steel slag-based catalyst, preferably 10 to 20%, and more preferably 10 to 15%.

[0040] In the present invention, calcium oxide in the steel slag-based catalyst is used as an adsorption component, ferric oxide and nickel oxide are used as active components, magnesium oxide is used as an auxiliary agent, and aluminum oxide is used as an inert component. The inert component hinders the active components NiO and Fe in the high-temperature catalytic process. 2 O 3 , and the sintering and agglomeration of the adsorbed component CaO, so the steel slag-based catalyst has excellent anti-sintering performance.

[0041] The present invention also provides an application of the steel slag-based catalyst described above in tar cracking and reforming to produce hydrogen.

[0042] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0043] The converter slag used in the present invention and comparative examples 2 to 4 comes from Aosen Steel Co., Ltd., Xinji City, Hebei Province, and its composition is as follows: CaO content is 36.7%, Fe 2 O 3 The content is 26.3%, SiO 2 The content is 18.2%, MgO content is 5.0%, Al 2 O 3 The content is 4.3%, other trace metal oxides P 2 O 5 , K 2 O, ZnO, MnO, TiO 2 、V 2 O 5 The total content is 9.5%.

[0044] Example 1

[0045] The steel slag was washed several times with deionized water, and after washing, placed in a constant temperature drying oven and dried at 105°C for 12 hours; the dried steel slag was loaded into a quartz boat, placed in a muffle furnace, and the temperature was increased to 800°C at a heating rate of 10°C / min, and kept warm for 3 hours for activation treatment to obtain activated steel slag.

[0046] 90 g of activated steel slag and 38.8 g of nickel nitrate hexahydrate were placed in 40 mL of deionized water and immersed under ultrasonic conditions for 5 h until the water was evaporated, then placed in a constant temperature drying oven and dried at 105°C for 12 h. After drying, they were loaded into a quartz boat and transferred to a muffle furnace. The temperature was increased to 600°C at a heating rate of 10°C / min and the mixture was kept warm for 3 h for calcination. The calcined product was ground and passed through an 80-mesh sieve to obtain a steel slag-based catalyst, recorded as AS-Ni, with a nickel oxide content of 10%.

[0047] Example 2

[0048] The difference from Example 1 is that the mass of activated steel slag is 95 g, the mass of nickel nitrate hexahydrate is 19.4 g, the content of nickel oxide in the prepared steel slag-based catalyst is 5%, and other conditions are the same.

[0049] Example 3

[0050] The difference from Example 1 is that the mass of activated steel slag is 85 g, the mass of nickel nitrate hexahydrate is 58.2 g, the content of nickel oxide in the prepared steel slag-based catalyst is 15%, and other conditions are the same.

[0051] Example 4

[0052] The difference from Example 1 is that the mass of activated steel slag is 80 g, the mass of nickel nitrate hexahydrate is 77.6 g, the content of nickel oxide in the prepared steel slag-based catalyst is 20%, and other conditions are the same.

[0053] Comparative Example 1

[0054] The alumina was washed several times with deionized water and placed in a constant temperature drying oven after washing, and dried at 105°C for 12 hours. The dried alumina was loaded into a quartz boat, placed in a muffle furnace, and the temperature was increased to 800°C at a heating rate of 10°C / min. The alumina was kept at this temperature for 3 hours for activation treatment to obtain activated alumina, which was recorded as Alumina.

[0055] Comparative Example 2

[0056] The steel slag was washed several times with deionized water, and after washing, it was placed in a constant temperature drying oven and dried at 105°C for 12 hours. The dried steel slag was loaded into a quartz boat, placed in a muffle furnace, and the temperature was increased to 800°C at a heating rate of 10°C / min. The slag was kept warm for 3 hours for activation treatment to obtain activated steel slag, which was recorded as AS.

[0057] Comparative Example 3

[0058] The difference from Example 1 is that 38.8 g of cobalt nitrate hexahydrate is used to replace nickel nitrate hexahydrate to prepare a steel slag-based catalyst, which is denoted as AS-Co, and other conditions are the same.

[0059] Comparative Example 4

[0060] The difference from Example 1 is that 30.3 g of copper nitrate hexahydrate is used to replace nickel nitrate hexahydrate to prepare a steel slag-based catalyst, which is denoted as AS-Cu, and other conditions are the same.

[0061] The steel slag-based catalysts of Examples 1 to 4, Comparative Examples 3 and 4, the activated alumina of Comparative Example 1, and the activated steel slag of Comparative Example 2 were respectively subjected to performance verification, and the specific process is as follows:

[0062] (1) A gasification experiment was carried out in a two-stage fixed bed reactor. 5 g of the prepared sample was evenly dispersed in the second stage fixed bed reactor and purged with 100 mL / min of high-purity nitrogen (99.999%) to exhaust the impurity gases in the reaction system.

[0063] (2) The first stage gasification temperature is 800°C, the catalytic reforming reaction temperature is 600°C, and the heating rate is 10°C / min. After reaching the preset temperature and maintaining it stably for 30 minutes, the water vapor flow rate is adjusted to 0.4 mL / min, and after ER=2, 5 g of biomass is quickly placed in the central heating area of ​​the first stage quartz reaction tube.

[0064] (3) The generated gas was washed with acetone to effectively condense the tar components in the gas, and then further dried to ensure that the gas did not contain moisture. The experimental reaction time lasted for 40 minutes.

[0065] (4) The pyrolysis products such as gas, tar and semi-coke after the reaction are collected in a gas bag, a condenser bottle and a fixed bed reactor respectively. The gas components of the collected gas are analyzed by gas chromatography (GC), and the yield of each component gas is calculated based on the nitrogen flow rate. The acetone in the gas washing bottle is evaporated by a rotary evaporator to obtain tar, which is then weighed.

[0066] from Figure 1It can be seen that the steel slag-based catalysts of Example 1 and Comparative Examples 3 and 4 make the tar in the three-phase products after gasification change particularly obvious. When the activated alumina in Comparative Example 1 is used as a catalyst, the proportion of tar is 1.8wt%, which can be reduced to 0.8wt% after loading nickel oxide, and the corresponding gas product is increased from 87.8wt% to 88.9wt%.

[0067] from Figure 2 It can be seen that compared with the activated alumina in Comparative Example 1 and the activated steel slag in Comparative Example 2, as well as the steel slag-based catalyst loaded with copper oxide or cobalt oxide, the steel slag-based catalyst loaded with nickel oxide (AS-Ni in Example 1) makes the proportion of hydrogen in the total gas components increase particularly significantly. When the activated alumina in Comparative Example 1 is used as a catalyst, the proportion of hydrogen is 33.2 vol%, and when the steel slag-based catalyst loaded with nickel oxide is used, it increases to 60.8 vol%, CO and CO 2 The proportion of gas components showed a clear downward trend, CO 2 The proportion of CO in the total gas components decreased significantly. When the activated alumina in Example 1 was used as the catalyst, 2 The proportion of nickel oxide in the steel slag-based catalyst was 29.8 vol%. 2 The proportion dropped to 12.5 vol%.

[0068] from Figure 3 It can be seen that compared with Comparative Examples 1 and 2, the steel slag-based catalyst loaded with transition metals can increase the production of hydrogen. The activated alumina in Comparative Example 1 as a catalyst accounts for 240.2 mL / g of hydrogen, and the steel slag-based catalyst loaded with nickel oxide in Example 1 increases the production of hydrogen to 476.3 mL / g. CO and CO 2 The gas production showed a clear downward trend, CO 2 The gas production decreased significantly. The activated alumina in Comparative Example 1 was used as the catalyst CO 2 The proportion is 220.1 mL / g, but the steel slag-based catalyst loaded with nickel oxide in Example 1 can be reduced to 98.2 mL / g, which shows that the steel slag-based catalyst loaded with nickel oxide of the present invention has good effects on catalytic cracking and reforming of tar to produce hydrogen.

[0069] from Figure 4 It can be seen that when the nickel oxide loading is 0 (Comparative Example 2), the tar content is 1.18%, and the tar content decreases as the nickel oxide loading increases. When the nickel oxide loading is 10% (Example 1), the tar content decreases to 0.78%, and then the tar content increases as the nickel oxide amount increases.

[0070] from Figure 5It can be seen that compared with the unloaded nickel oxide (Comparative Example 2), the proportion of hydrogen in the gas product increased significantly after the nickel oxide was loaded. When it was not loaded (Comparative Example 2), the proportion of hydrogen was 53.2 vol%, and when 10% nickel oxide was loaded (Example 1), it increased to a maximum of 60.88 vol%. At the same time, CO and CO 2 The proportion of hydrogen also decreases accordingly, indicating that loading nickel oxide in activated steel slag can significantly increase the proportion of hydrogen in the gas product. Properly increasing the loading amount of nickel oxide can increase the proportion of hydrogen, but when there is too much nickel oxide, it will block the pores and active sites of the material, resulting in a decrease in the catalytic effect.

[0071] from Figure 6 It can be seen that, compared with the case where nickel oxide is not loaded (Comparative Example 2), the hydrogen production in the gas product increases significantly after nickel oxide is loaded. When the product is not loaded (Comparative Example 2), the hydrogen production is 381.9 mL / g. When 10% nickel oxide is loaded (Example 1), the hydrogen production increases to a maximum of 476.3 mL / g. At the same time, CO and CO 2 The yield of is also reduced accordingly, indicating that loading nickel oxide in activated steel slag can significantly increase the yield of hydrogen. This shows that the steel slag-based catalyst loaded with nickel oxide of the present invention has a good effect on catalytic cracking and reforming of tar to produce hydrogen.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a steel slag-based catalyst, characterized in that: The steps include: S1: activating the steel slag to obtain activated steel slag; S2: The activated steel slag and nickel nitrate hexahydrate are placed in water for impregnation treatment, and then calcined to obtain a steel slag-based catalyst.

2. The method for preparing a steel slag-based catalyst according to claim 1, characterized in that: In the step S1, the steel slag is converter steel slag; the steel slag is firstly washed and dried before the activation treatment.

3. The method for preparing a steel slag-based catalyst according to claim 2, characterized in that: The washing is performed with water; the drying temperature is 100-120° C., and the drying time is 10-14 hours.

4. The method for preparing a steel slag-based catalyst according to any one of claims 1 to 3, characterized in that: In the step S1, the heating rate during the activation treatment is 8-12°C / min, the temperature of the activation treatment is 800-1000°C, and the time of the activation treatment is 2-4h.

5. The method for preparing a steel slag-based catalyst according to claim 4, characterized in that: In the step S2, the mass ratio of activated steel slag to nickel nitrate hexahydrate is 80-90:15-80.

6. The method for preparing a steel slag-based catalyst according to claim 2, 3 or 5, characterized in that: In step S2, the immersion treatment time is 4 to 6 hours.

7. The method for preparing a steel slag-based catalyst according to claim 6, characterized in that: In the step S2, the heating rate during the calcination treatment is 8-12°C / min, the calcination treatment temperature is 500-700°C, and the calcination treatment time is 2-4h.

8. The steel slag-based catalyst prepared by the method for preparing a steel slag-based catalyst according to any one of claims 1 to 7, characterized in that: The steel slag-based catalyst is mainly composed of calcium oxide, nickel oxide, ferric oxide, magnesium oxide and aluminum oxide; the mass of the nickel oxide accounts for 5-20% of the mass of the steel slag-based catalyst.

9. Use of the steel slag-based catalyst according to claim 8 in tar cracking and reforming to produce hydrogen.

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