A rare earth metal modified nickel-based catalyst, a preparation method and application thereof

Abstract

The application discloses a rare earth metal modified nickel-based catalyst and a preparation method and application thereof. The dolomite is modified by sodium silicate and calcium citrate, so that the catalyst is loose and porous, and the specific surface area is increased. The larger the specific surface area is, the more active sites are, and the faster the reaction rate is. In addition, the large specific surface area can increase the contact area between the catalyst and the reactants, so that the reaction efficiency is improved. The addition of the rare earth metal lanthanum can change the structure of the nickel-based catalyst, including the particle size and the morphology, which helps to provide more active sites and higher surface area, so that the hydrogen production reaction rate is improved. In addition, the rare earth element generally has good thermal stability, and the introduction of lanthanum can enhance the thermal stability of the catalyst, which is particularly important for the hydrogen production reaction at high temperature. In addition, the accumulation of carbon deposition can be inhibited, and the catalyst poisoning can be reduced to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a rare earth metal modified nickel-based catalyst, its preparation method, and its application. Background Technology

[0002] Gasification is a technological method for the resource utilization of organic solid waste. It achieves clean and efficient utilization of solid waste while offering advantages such as high efficiency, low secondary pollution emissions, complete degradation of harmful substances, and high value-added products. However, gasification also faces the following problems: high tar production, high coke residue, and low calorific value of syngas. These problems seriously hinder the improvement of biomass gasification efficiency and reduce the safety of gasification equipment.

[0003] The main method to solve the above problems is to use catalysts. Nickel-based catalysts have excellent catalytic activity and relatively low cost. They mainly use Ni as the active reaction site and are the most widely studied and applied catalysts in the catalytic cracking of biomass tar. However, these catalysts still have problems such as poor stability, easy sintering, and low gas production. For example, the paper "Research on the Production of Hydrogen-Rich Gas by Catalytic Gasification of Wood Chips with Steam" added a Ni-CaO composite catalyst during the gasification process and found that the nickel-based catalyst effectively increased the H2 content in the gas while reducing the CO2 content. However, a drawback is that the nickel-based catalyst is very prone to carbon deposition, leading to a decrease in activity. The paper "Research on In-situ Catalytic Gasification of Municipal Solid Waste for Hydrogen Production Based on NiO / MD Catalyst" studied the effect of a nickel-based catalyst on the in-situ catalytic gasification of municipal solid waste for hydrogen production. The results showed that the nickel-based catalyst had a high tar removal rate, but the hydrogen concentration was only 52.79 vol.%. Furthermore, existing technologies have also found that nickel-based catalysts can promote the conversion of tar into unsaturated hydrocarbons and oxygen-containing organic matter, and promote the generation of H2 and CO. However, the catalysts have poor stability and are not regenerable. Based on the shortcomings exhibited by nickel-based catalysts, improvements to existing nickel-based catalysts are needed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a rare earth metal modified nickel-based catalyst, its preparation method, and its application. The prepared catalyst is not easily deactivated by sintering, has excellent mechanical strength and stability, and exhibits highly efficient catalytic hydrogen production performance for sludge / straw.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a rare earth metal-modified nickel-based catalyst includes the following steps:

[0007] S1. Preparation of modified dolomite carrier: Pretreated dolomite, sodium silicate and calcium citrate are mixed, water is added and mixed evenly, and then dried and calcined to obtain modified dolomite.

[0008] S2. Preparation of rare earth metal modified nickel-based catalyst: Soluble nickel salt and soluble lanthanum salt are added to deionized water and stirred to dissolve. Then, the modified dolomite prepared in step S1 is added, stirred evenly, and heated in an oil bath for reaction. After the reaction is completed, the catalyst is dried, calcined, ground and sieved to obtain rare earth metal modified nickel-based catalyst.

[0009] Preferably, in step S1, the pretreatment of dolomite is as follows: the dolomite powder is calcined in a muffle furnace to obtain pretreated dolomite.

[0010] Preferably, in step S1, the mass ratio of pretreated dolomite, sodium silicate, calcium citrate and water is 5-10:1-3:1-2:30-50.

[0011] Preferably, in step S1, the drying temperature is 100-120℃ and the drying time is 5-8h; the calcination temperature is 400-500℃ and the calcination time is 2-3h.

[0012] Preferably, in step S2, the soluble nickel salt is selected from at least one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate; and the soluble lanthanum salt is selected from at least one of lanthanum chloride, lanthanum nitrate, and lanthanum sulfate.

[0013] Preferably, in step S2, the mass ratio of soluble nickel salt, soluble lanthanum salt, deionized water and modified dolomite is 4-8:1-4:100:20-40.

[0014] Preferably, in step S2, the oil bath heating reaction temperature is 80-100℃, and the oil bath heating reaction time is 3-4h.

[0015] Preferably, in step S2, the calcination temperature is 1000-1100℃ and the calcination time is 3-5h.

[0016] This invention provides a rare earth metal modified nickel-based catalyst prepared by the above preparation method.

[0017] This invention also provides the application of the above-mentioned rare earth metal modified nickel-based catalyst in catalytic gasification of sludge / straw to produce hydrogen.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) By modifying dolomite with sodium silicate and calcium citrate, the catalyst can be made loose and porous, thereby increasing the specific surface area. The larger the specific surface area, the more active sites there are, and the faster the reaction rate. In addition, a large specific surface area can also increase the contact area between the catalyst and the reactants, thereby improving the reaction efficiency.

[0020] (2) The addition of rare earth metal lanthanum can change the structure of nickel-based catalysts, including particle size and morphology, which helps to provide more active sites and higher surface area, thereby increasing the rate of hydrogen production reaction. At the same time, rare earth elements generally have good thermal stability, and the introduction of lanthanum can enhance the thermal stability of the catalyst, which is particularly important for hydrogen production reaction at high temperature. It can also inhibit the accumulation of carbon deposits and alleviate catalyst poisoning to a certain extent. In addition, under high temperature reaction conditions, one of the reasons for catalyst deactivation is catalyst sintering, which reduces the specific surface area and pore size, leading to a decrease in activity. The introduction of rare earth metal lanthanum can effectively inhibit this sintering phenomenon and improve the stability of the catalyst during temperature cycling, thereby maintaining the activity and stability of the catalyst. Detailed Implementation

[0021] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0022] It should be noted that, unless otherwise specified, all chemical reagents involved in this invention were purchased through commercial channels.

[0023] A method for preparing a rare earth metal-modified nickel-based catalyst includes the following steps:

[0024] S1. Preparation of modified dolomite carrier

[0025] Pretreated dolomite, sodium silicate, and calcium citrate were mixed, water was added to make a uniform solution, and then the mixture was dried and calcined to obtain modified dolomite.

[0026] In this step, the pretreatment of dolomite is as follows: Dolomite powder is calcined in a muffle furnace at 800-900℃ for 2-3 hours to obtain pretreated dolomite.

[0027] In this step, the mass ratio of pretreated dolomite, sodium silicate, calcium citrate and water is 5-10:1-3:1-2:30-50, and more preferably 6-8:1-2:1-2:35-40.

[0028] In this step, the drying temperature is 100-120℃, for example, 100℃, 105℃, 110℃, 115℃, or 120℃ can be selected; the drying time is 5-8h, for example, 5h, 6h, 7h, or 8h can be selected.

[0029] In this step, the calcination temperature is 400-500℃, for example, 400℃, 420℃, 440℃, 450℃, 460℃, 480℃, or 500℃ can be selected; the calcination time is 2-3 hours, for example, 2 hours, 2.5 hours, or 3 hours can be selected.

[0030] S2, Preparation of rare earth metal modified nickel-based catalysts

[0031] Soluble nickel salt and soluble lanthanum salt were added to deionized water and stirred to dissolve. Then, the modified dolomite prepared in step S1 was added, stirred evenly, and heated in an oil bath to react. After the reaction was completed, the catalyst was dried, calcined, ground, and sieved to obtain rare earth metal modified nickel-based catalyst.

[0032] In this step, the soluble nickel salt is selected from at least one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate; the soluble lanthanum salt is selected from at least one of lanthanum chloride, lanthanum nitrate, and lanthanum sulfate.

[0033] In this step, the mass ratio of soluble nickel salt, soluble lanthanum salt, deionized water and modified dolomite is 4-8:1-4:100:20-40, and more preferably 5-6:2-3:100:25-30.

[0034] In this step, the oil bath heating reaction temperature is 80-100℃, for example, 80℃, 85℃, 90℃, 95℃, or 100℃ can be selected; the oil bath heating reaction time is 3-4 hours, for example, 3 hours, 3.5 hours, or 4 hours can be selected.

[0035] In this step, the calcination temperature is 1000-1100℃, for example, 1000℃, 1020℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, or 1100℃; the calcination time is 3-5h, for example, 3h, 4h, or 5h.

[0036] The present invention will be further described below through specific embodiments.

[0037] Example 1

[0038] A method for preparing a rare earth metal-modified nickel-based catalyst includes the following steps:

[0039] S1. Preparation of modified dolomite carrier: Dolomite powder was placed in a crucible and heated to 900℃ in a muffle furnace at a heating rate of 10℃ / min, and calcined for 2 hours to obtain pretreated dolomite. 70g of pretreated dolomite, 20g of sodium silicate and 10g of calcium citrate were mixed together and 400g of water was added for adjustment. Then, the mixture was placed in an oven and dried at 105℃ for 7 hours to form a shape. Then, it was placed in a muffle furnace and heated to 400℃ at a rate of 10℃ / min, and calcined for 2 hours to obtain modified dolomite.

[0040] S2. Preparation of rare earth metal modified nickel-based catalyst: Weigh 5.829g of nickel nitrate hexahydrate and 1.834g of lanthanum nitrate hexahydrate into a beaker, add 100ml of deionized water, stir to dissolve, and then slowly add 25g of the modified dolomite obtained in step (1) to the above mixed solution, stir evenly, and then place it in an oil bath, heat and stir at 85℃ for 3h. After stirring, place it in an oven at 105℃ to dry for 12h, and then place it in a muffle furnace, heat to 1000℃ at a heating rate of 10℃ / min, calcine for 4h, grind through a 200-mesh sieve to obtain the rare earth metal modified nickel-based catalyst.

[0041] Example 2

[0042] A method for preparing a rare earth metal-modified nickel-based catalyst includes the following steps:

[0043] S1. Preparation of modified dolomite carrier: Dolomite powder was placed in a crucible and heated to 900℃ in a muffle furnace at a heating rate of 10℃ / min, and calcined for 2 hours to obtain pretreated dolomite. 60g of pretreated dolomite, 10g of sodium silicate and 10g of calcium citrate were mixed together and 400g of water was added for adjustment. Then, the mixture was placed in an oven and dried at 105℃ for 7 hours to form a shape. Then, it was placed in a muffle furnace and heated to 500℃ at a rate of 10℃ / min, and calcined for 2 hours to obtain modified dolomite.

[0044] S2. Preparation of rare earth metal modified nickel-based catalyst: Weigh 5.829g of nickel nitrate hexahydrate and 1.834g of lanthanum nitrate hexahydrate into a beaker, add 100ml of deionized water, stir to dissolve, and then slowly add 30g of the modified dolomite obtained in step (1) to the above mixed solution, stir evenly, and then place it in an oil bath, heat and stir at 100℃ for 3h. After stirring, place it in an oven at 105℃ to dry for 12h, and then place it in a muffle furnace, heat to 1000℃ at a heating rate of 10℃ / min, calcine for 4h, grind through a 200-mesh sieve to obtain the rare earth metal modified nickel-based catalyst.

[0045] Example 3

[0046] A method for preparing a rare earth metal-modified nickel-based catalyst includes the following steps:

[0047] S1. Preparation of modified dolomite carrier: Dolomite powder was placed in a crucible and heated to 900℃ in a muffle furnace at a heating rate of 10℃ / min. It was calcined for 2 hours to obtain pretreated dolomite. 80g of pretreated dolomite, 20g of sodium silicate and 15g of calcium citrate were mixed together and 400g of water was added for adjustment. The mixture was then placed in an oven and dried at 105℃ for 7 hours to form a shape. Then it was placed in a muffle furnace and heated to 500℃ at a rate of 10℃ / min. It was calcined for 3 hours to obtain modified dolomite.

[0048] S2. Preparation of rare earth metal modified nickel-based catalyst: Weigh 5.829g of nickel nitrate hexahydrate and 1.834g of lanthanum nitrate hexahydrate into a beaker, add 100ml of deionized water, stir to dissolve, and then slowly add 35g of the modified dolomite obtained in step (1) to the above mixed solution, stir evenly, and then place it in an oil bath, heat and stir at 100℃ for 3h. After stirring, place it in an oven at 105℃ to dry for 12h, and then place it in a muffle furnace, heat to 1000℃ at a heating rate of 10℃ / min, calcine for 4h, grind through a 200-mesh sieve to obtain the rare earth metal modified nickel-based catalyst.

[0049] Example 4

[0050] A method for preparing a rare earth metal-modified nickel-based catalyst includes the following steps:

[0051] S1. Preparation of modified dolomite carrier: Dolomite powder was placed in a crucible and heated to 900℃ in a muffle furnace at a heating rate of 10℃ / min, and calcined for 2 hours to obtain pretreated dolomite. 100g of pretreated dolomite, 30g of sodium silicate and 20g of calcium citrate were mixed together and 500g of water was added for adjustment. Then, the mixture was placed in an oven and dried at 105℃ for 7 hours to form a shape. Then, it was placed in a muffle furnace and heated to 500℃ at a rate of 10℃ / min, and calcined for 3 hours to obtain modified dolomite.

[0052] S2. Preparation of rare earth metal modified nickel-based catalyst: Weigh 5.829g of nickel nitrate hexahydrate and 1.834g of lanthanum nitrate hexahydrate into a beaker, add 100ml of deionized water, stir to dissolve, and then slowly add 40g of the modified dolomite obtained in step (1) to the above mixed solution, stir evenly, and then place it in an oil bath, heat and stir at 100℃ for 3h. After stirring, place it in an oven at 105℃ to dry for 12h, and then place it in a muffle furnace, heat to 1000℃ at a heating rate of 10℃ / min, calcine for 4h, grind through a 200-mesh sieve to obtain the rare earth metal modified nickel-based catalyst.

[0053] Comparative Example 1

[0054] A method for preparing a nickel-based catalyst includes the following steps:

[0055] S1. Preparation of modified dolomite carrier: Dolomite powder was placed in a crucible and heated to 900℃ in a muffle furnace at a heating rate of 10℃ / min, and calcined for 2 hours to obtain pretreated dolomite. 70g of pretreated dolomite, 20g of sodium silicate and 10g of calcium citrate were mixed together and 400g of water was added for adjustment. Then, the mixture was placed in an oven and dried at 105℃ for 7 hours to form a shape. Then, it was placed in a muffle furnace and heated to 400℃ at a rate of 10℃ / min, and calcined for 2 hours to obtain modified dolomite.

[0056] S2. Preparation of nickel-based catalyst: Weigh 5.829g of nickel nitrate hexahydrate into a beaker, add 100ml of deionized water, stir to dissolve, then slowly add 25g of the modified dolomite obtained in step (1) to the above mixed solution, stir evenly, then place it in an oil bath, heat and stir at 85℃ for 3h, after stirring is completed, put it in an oven at 105℃ to dry for 12h, then place it in a muffle furnace, heat to 1000℃ at a heating rate of 10℃ / min, calcine for 4h, grind through a 200-mesh sieve to obtain the nickel-based catalyst.

[0057] Comparative Example 2

[0058] A method for preparing a rare earth metal-modified nickel-based catalyst includes the following steps:

[0059] Weigh 5.829g of nickel nitrate hexahydrate and 1.834g of lanthanum nitrate hexahydrate into a beaker, add 100ml of deionized water, stir to dissolve, then slowly add 25g of unmodified dolomite to the above mixed solution, stir evenly, then place in an oil bath, heat and stir at 85℃ for 3h, after stirring is complete, place in an oven at 105℃ to dry for 12h, then place in a muffle furnace, heat to 1000℃ at a heating rate of 10℃ / min, calcine for 4h, grind through a 200-mesh sieve to obtain rare earth metal modified nickel-based catalyst.

[0060] The catalysts prepared in Examples 1-4 and Comparative Examples 1-2 were used in the catalytic gasification of sludge / straw steam to produce hydrogen. The specific experimental steps are as follows:

[0061] (1) Accurately weigh 0.4g of sludge and 0.6g of corn stalks into a beaker, stir evenly, put the mixture into a small quartz basket, weigh 2g of catalyst and place it on the sand core of the quartz tube, spread it evenly on the surface, and place the quartz tube vertically in a vertical tube furnace.

[0062] (2) Set up the experimental setup and check the airtightness of the setup. Set the N2 flow rate to 500 ml / min and observe whether the bubbles in the gas washing bottle are uniform. At the same time, observe whether the glass rotor flowmeter of the gas analyzer is at "0.5 L / min". If both are in normal condition, it means that the airtightness is good and the experiment can begin.

[0063] (3) After confirming the airtightness, the furnace body is programmed to heat up. The N2 flow rate is reduced to 180 ml / min to ensure that the reaction is fully carried out. The starting temperature of the electric furnace is set to 25℃, the heating rate is 25℃ / min, the sludge / straw water vaporization reaction temperature is 900℃, the reaction time is 40 min, and the water vapor flow rate is 0.5 ml / min. Two minutes before the temperature reaches the specified temperature, the injection pump is turned on to ensure that the reaction device is filled with water vapor atmosphere. After the reaction is completed, the N2 flow rate is adjusted to 50 ml / min as a protective gas and continued until the cooling is completed.

[0064] (4) Finally, gas collection is performed. The percentage of gas generated per second can be obtained by the flue gas online analyzer.

[0065] The experimental results are shown in Table 1:

[0066] Table 1

[0067] Hydrogen concentration (%) Hydrogen production (mol / kg) Total gas production (g / L) Example 1 61.3 24.7 0.903 Example 2 65.1 27.5 0.947 Example 3 60.4 23.3 0.866 Example 4 55.9 20.4 0.813 Comparative Example 1 50.2 18.6 0.830 Comparative Example 2 52.6 19.7 0.839

[0068] The catalysts prepared in Example 1 and Comparative Examples 1-2 were used in a sludge / straw steam catalytic gasification hydrogen production cycle experiment. The specific experimental steps were the same as above. After the reaction was completed, the sludge and corn straw were replaced, and the mixture was placed in a tubular furnace for another gasification experiment. This cycle was repeated 20 times. The experimental results are shown in Table 2.

[0069] Table 2

[0070]

[0071]

[0072] As can be seen from Table 2, after 20 cycles, the hydrogen concentration of the catalyst prepared in Example 1 of the present invention decreased by only 7%, the hydrogen production decreased by 15%, and the total gas production decreased by 8.88% compared with the first gasification experiment. This indicates that the rare earth metal modified nickel-based catalyst prepared in the present invention has good stability, maintains a balanced catalytic hydrogen production performance, and can be reused.

[0073] Finally, it should be noted that the above embodiments do not limit the present invention in any way. Those skilled in the art can make modifications and improvements based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a rare earth metal-modified nickel-based catalyst, characterized in that, Includes the following steps: S1. Preparation of modified dolomite carrier: Pretreated dolomite, sodium silicate and calcium citrate are mixed, water is added to make uniform, and then dried and calcined to obtain modified dolomite. S2. Preparation of rare earth metal modified nickel-based catalyst: Soluble nickel salt and soluble lanthanum salt are added to deionized water and stirred to dissolve. Then, the modified dolomite prepared in step S1 is added, stirred evenly, and heated in an oil bath to react. After the reaction is completed, the catalyst is dried, calcined, ground and sieved to obtain rare earth metal modified nickel-based catalyst. In step S1, the pretreatment of dolomite is as follows: Dolomite powder is calcined in a muffle furnace to obtain pretreated dolomite. In step S2, the mass ratio of soluble nickel salt, soluble lanthanum salt, deionized water and modified dolomite is 4-8:1-4:100:20-40.

2. The method for preparing the rare earth metal modified nickel-based catalyst according to claim 1, characterized in that, In step S1, the mass ratio of pretreated dolomite, sodium silicate, calcium citrate and water is 5-10:1-3:1-2:30-50.

3. The preparation method of the rare earth metal modified nickel-based catalyst according to claim 1, characterized in that, In step S1, the drying temperature is 100-120℃, the drying time is 5-8h, the calcination temperature is 400-500℃, and the calcination time is 2-3h, thus obtaining modified dolomite.

4. The method for preparing the rare earth metal modified nickel-based catalyst according to claim 1, characterized in that, In step S2, the soluble nickel salt is selected from at least one of nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate; the soluble lanthanum salt is selected from at least one of lanthanum chloride, lanthanum nitrate, and lanthanum sulfate.

5. The method for preparing the rare earth metal modified nickel-based catalyst according to claim 1, characterized in that, In step S2, the oil bath heating reaction temperature is 80-100℃, and the oil bath heating reaction time is 3-4h.

6. The method for preparing the rare earth metal modified nickel-based catalyst according to claim 1, characterized in that, In step S2, the calcination temperature is 1000-1100℃ and the calcination time is 3-5h.

7. The rare earth metal modified nickel-based catalyst prepared by the preparation method according to any one of claims 1-6.

8. The application of the rare earth metal modified nickel-based catalyst as described in claim 7 in the catalytic gasification of sludge / straw to produce hydrogen.

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