Preparation method and application of transition metal loaded modified active coke bifunctional catalyst

Abstract

The invention discloses a preparation method and application of a transition metal loaded modified active coke bifunctional catalyst, the catalyst comprises a first component Ni and a second component Ce, and the first component and the second component are loaded on the surface of a modified active coke carrier. The transition metal loaded modified active coke bifunctional catalyst can simultaneously catalyze ammonia selective reduction of nitrogen oxide reaction and carbon monoxide oxidation reaction, simultaneous catalytic elimination of NO and CO on the same catalytic bed layer is realized, and the removal efficiency at the temperature interval of 180-250 DEG C can simultaneously reach 90% or above.

Description

Technical Field

[0001] The present application relates to a metal-supported modified activated coke catalyst, belonging to the field of catalysts. Background Art

[0002] In the steel industry, sintering and coking processes produce a large amount of toxic and harmful waste gas, which urgently needs to be deeply purified. Nitrogen oxides and carbon monoxide are two of the most harmful air pollutants in sintering machine exhaust and coke oven flue gas. The exhaust gas from the sintering machine in the steel plant has a large air volume, and the average nitrogen oxide content is 250-400 mg / m 3 , up to 700mg / m 3 The CO content is high, with a volume concentration of 0.6-1.2% and a mass concentration of 10000 mg / m 3 The average nitrogen oxide content in coke oven flue gas is 1000-1500 mg / m 3 , CO content is usually between 2000 and 4000 mg / m 3 About. Nitrogen oxides can cause atmospheric hazards such as photochemical smog, acid rain, and ozone hole, and can also have adverse effects on human health. CO is a toxic gas to humans and animals. It is very easy to combine with hemoglobin in the blood to weaken the oxygen transport capacity of hemoglobin. CO has an important impact on the atmospheric environment: CO will react photochemically with VOCs and NOx, causing an increase in ozone concentration; CO is the control gas of OH free radicals, the most important active substance in the stratosphere, and can control OH to react with almost all trace gases in the atmosphere, thereby further affecting the atmospheric environment. At present, most sintering machines and coke ovens have installed SCR denitrification facilities, and the excessive emission of NOx has been effectively controlled, but CO has not been effectively controlled. The control of CO is receiving increasing attention, and it is necessary to develop an efficient catalytic system that can synergistically remove CO and NO in the flue gas exhaust temperature range.

[0003] Activated coke is a porous carbonaceous material made from coal. It has the characteristics of high strength and unique pore structure. Most of them are 8-9mm cylindrical. It has been widely used in flue gas dry desulfurization and has the advantages of high desulfurization efficiency and high sulfur capacity. In addition, metal-modified activated coke also has low-temperature denitrification performance.

[0004] Chinese patent CN103406122 B reports a catalyst for removing nitrogen oxides and carbon monoxide and a preparation method thereof. The catalyst is copper oxide or cuprous oxide supported by activated carbon, and shows the removal effect of simultaneously removing nitrogen monoxide and carbon monoxide in a simulated flue gas atmosphere containing NO and CO. However, the low-temperature conversion rate of the catalyst is low, such as the CO conversion rate is only 27% at 200°C, and the removal rate of NO and CO can reach more than 90% when the temperature rises to above 250°C. However, when the catalyst is prepared, the carrier is coconut shell activated carbon, and the risk of catalyst spontaneous combustion will increase when operating at such a high temperature of 250°C in an oxygen-rich atmosphere. Summary of the invention

[0005] The present invention aims at solving the above technical defects and prepares a transition metal-loaded modified activated coke catalyst. The catalyst has low cost and has two catalytic functions, and can effectively catalyze NO-NH3-SCR reaction and CO oxidation reaction in the low temperature range.

[0006] The present application provides a modified activated coke-supported transition metal catalyst, which can simultaneously catalyze the selective reduction of nitrogen oxides by ammonia and the oxidation of carbon monoxide, thereby achieving the simultaneous catalytic elimination of NO and CO on the same catalytic bed.

[0007] According to one aspect of the present application, a bimetallic modified activated coke catalyst is provided. The catalyst loads bimetallic on the surface of activated coke to construct different reactive active sites, thereby achieving one-step simultaneous removal of NO and CO in complex flue gas.

[0008] According to one aspect of the present application, a Ni—Ce / modified activated coke catalyst is provided that can simultaneously catalyze the selective reduction of nitrogen oxides by ammonia and the oxidation of carbon monoxide.

[0009] The catalyst comprises a first component, a second component and modified active coke which provides a physical carrier and a synergistic or auxiliary catalytic effect to the first component and the second component, wherein: the first component is NiO; the second component is CeO2.

[0010] Optionally, the content of the first component metal oxide in the catalyst is 3 to 30 wt %; preferably 5 to 15 wt %;

[0011] Optionally, the content of the second component metal oxide in the catalyst is 3% to 20wt%, preferably 5-15wt%;

[0012] The modified activated coke is the first component, and the second component provides a physical carrier and plays a synergistic or auxiliary catalytic role. Based on the total weight of the catalyst, its content is optionally 50wt%-96wt%, preferably 70wt%-90wt%.

[0013] The atomic ratio of nickel to cerium in the first component and the second component may be 1:10 to 10:1, preferably 1:1 to 4:1.

[0014] The present application also provides a method for preparing the above catalyst, which uses acid-modified activated coke as a carrier, and immerses the carrier in a mixed aqueous solution of inorganic salts of Ni and Ce, dries it, and calcines it.

[0015] Furthermore, in the above technical solution, the method specifically comprises at least the following steps:

[0016] ①Activated coke modification:

[0017] A certain amount of activated coke particles (30 g) were weighed and placed in a dry beaker, and a nitric acid solution with a concentration of 63 wt% was added, and the sample was over-impregnated for 6 h at room temperature. The treated sample was rinsed with deionized water until neutral, and dried in an oven at 105°C for 12 h to obtain a modified activated coke sample.

[0018] ②Metal load:

[0019] The metal-supported catalyst was prepared by the equal volume impregnation method. An appropriate amount of modified activated coke particles was placed in a beaker. The saturated water absorption of activated coke was calculated based on the measured water absorption rate of activated coke. An appropriate amount of Ni(NO3)2·6H2O and Ce(NO3)3·6H2O were dissolved in deionized water to obtain a mixed solution. The modified activated coke particles were placed in the mixed solution and impregnated at room temperature for 2 hours.

[0020] Bimetallic catalysts with different ratios and loadings were prepared by adjusting the molar amounts of Ni(NO3)2·6H2O and Ce(NO3)3·6H2O in the impregnation solution.

[0021] ③ Drying and roasting:

[0022] The impregnated activated coke sample was placed in an oven, dried at 105°C for 12 hours, and then placed in a quartz tube and calcined at 400°C for 2 hours under a nitrogen atmosphere to obtain a modified activated coke loaded with Ni and Ce bimetallic catalyst, which is recorded as m-xNi-yCe / AC-N. (Where m is the metal loading, and x and y are the ratios of Ni and Ce)

[0023] According to another aspect of the present application, there is provided a use of a Ni—Ce / modified activated coke catalyst in simultaneously catalyzing ammonia selective reduction of nitrogen oxides and carbon monoxide oxidation.

[0024] Optionally, the application is application in eliminating nitrogen oxides and carbon monoxide from flue gas emissions.

[0025] Optionally, the flue gas source is a fixed source.

[0026] Optionally, a mixed gas containing nitrogen oxides, carbon monoxide, oxygen and ammonia is introduced into a reactor containing the non-precious metal composite oxide catalyst of the present application, and the reaction conditions are: a volume space velocity of 1000 to 5000 h -1 , the temperature is 100 ~ 250 ℃.

[0027] Preferably, the volume space velocity is 2000-3000h -1 , the temperature is 150 ~ 200 ℃.

[0028] As a specific implementation, a method for purifying fixed source flue gas is provided, the method at least comprising: purifying a mixed gas containing nitrogen oxides, carbon monoxide and ammonia in the presence of the Ni-Ce / modified activated coke catalyst.

[0029] The Ni-Ce / modified activated coke catalyst provided in the present application is used for the selective catalytic reduction NH3-SCR process of nitrogen oxides and the catalytic oxidation process of carbon monoxide in the fixed source flue gas purification system. After ammonia is added to the flue gas, NO and CO can be eliminated at the same time within a certain temperature range, and the removal efficiency can reach more than 90% at the same time.

[0030] The beneficial effects of this application include:

[0031] 1) The transition metal-loaded modified activated coke bifunctional catalyst provided in the present application enriches the catalytic active sites, constructs multiple redox cycles on the catalyst surface, and exhibits a synergistic effect, thereby achieving the simultaneous catalytic elimination of NO and CO on the same catalyst under low temperature conditions.

[0032] 2) The transition metal-loaded modified activated coke bifunctional catalyst provided in this application is used for flue gas treatment, which can greatly simplify the treatment process and reduce the cost of pollutant treatment. The conventional step-by-step method of removing NO and CO requires the setting of different reaction units and the installation of different catalysts, which is bound to increase the site area, equipment investment and operating costs. The transition metal-loaded modified activated coke bifunctional catalyst for integrated elimination of NO and CO provided in this application can effectively circumvent the above problems. The catalyst can efficiently catalyze the SCR reaction of NO and NH3, and can also efficiently catalyze the oxidation reaction of CO, completing the efficient removal of NO and CO in one step in one reactor, making the treatment process more compact and efficient.

[0033] 3) The transition metal-loaded modified activated coke bifunctional catalyst provided in the present application does not contain precious metals, has low cost, and can be applied to the treatment of fixed source flue gas pollutants with huge flue gas volumes. DETAILED DESCRIPTION

[0034] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0035] Unless otherwise specified, the raw materials in the examples of this application were purchased from commercial sources. Unless otherwise specified, the test methods all adopted conventional methods, and the instrument settings all adopted the settings recommended by the manufacturer.

[0036] In the examples of this application, the denitrification efficiency and the CO removal efficiency are calculated as follows:

[0037] Among them, NOx out is the outlet concentration of nitrogen oxides, NOx in is the inlet concentration of nitrogen oxides.

[0038] Among them, CO out is the outlet concentration of carbon monoxide, CO in is the inlet concentration of nitrogen oxides.

[0039] Figure 1 NO on the catalyst prepared in Example 1 x Conversion rate and CO conversion rate change curves with inlet gas temperature.

[0040] Figure 2 NO on the catalyst prepared in Example 2 x Conversion rate and CO conversion rate change curves with inlet gas temperature.

[0041] Figure 3 NO on the catalyst prepared in Example 3 x Conversion rate and CO conversion rate change curves with inlet gas temperature.

[0042] Figure 4 NO on the catalyst prepared in Example 4 x Conversion rate and CO conversion rate change curves with inlet gas temperature.

[0043] Figure 5 Preparation and activity evaluation of the catalyst prepared in Example 5 x Conversion rate and CO conversion rate change curves with inlet gas temperature.

[0044] Example 1: Preparation of 30-2Ni-4Ce / AC-N catalyst (metal loading 25wt%, Ni:Ce atomic ratio = 2:4)

[0045] Take 30g of activated coke particles (20-40 mesh) and place them in a 63wt% nitric acid solution. After immersion for 6h, rinse with deionized water until neutral and place in a 105℃ oven to dry for 12h. Mix 8.72gNi(NO3)2·6H2O and (0.03mol) with 26.04g Ce(NO3)3·6H2O (0.06mol) and dissolve them in deionized water. The volume of the mixed solution is approximately equal to 24ml. The modified activated coke is immersed in the mixed solution for 2h, then placed in a 105℃ oven to dry, and calcined in a tubular quartz furnace with nitrogen as protective gas, calcination temperature of 400℃, and calcination time of 2h. A bifunctional catalyst with a metal loading of 30% and a molar ratio of Ni to Ce of 2:4 is obtained, which is recorded as 30-2Ni-4Ce / AC-N.

[0046] 10 ml of the prepared catalyst was placed in a fixed bed reactor for activity evaluation. A mixed gas containing nitrogen oxides, carbon monoxide, oxygen and ammonia was introduced into the reactor. The reaction conditions were: a volume space velocity of 3000 h -1 , the temperature is 100~250℃. Figure 1 As shown, within the temperature range of 100-250°C, the NO conversion rate is 94%-100%, and above 180°C, the CO conversion rate is greater than 90%.

[0047] Example 2: Preparation of 30-3Ni-4Ce / AC-N catalyst (metal loading 30wt%, Ni:Ce atomic ratio = 3:4)

[0048] Take 30g of activated coke particles (20-40 mesh) and place them in a 63% nitric acid solution. After immersion for 6 hours, rinse with deionized water until neutral and place in a 105℃ oven to dry for 12 hours to obtain nitric acid-modified activated coke particles, recorded as AC-N. Mix 12.22g Ni(NO3)2.6H2O (0.042mol) and 20.30g Ce(NO3)3.6H2O (0.056mol) and dissolve them in deionized water. The volume of the mixed solution is approximately equal to 24ml. The modified activated coke is immersed in the mixed solution for 2 hours, then placed in a 105℃ oven to dry, and calcined in a tubular quartz furnace with nitrogen as the protective gas, calcination temperature of 400℃, calcination time of 2h, and 30-3Ni-4Ce / AC-N catalyst is obtained.

[0049] 10 ml of the prepared catalyst was placed in a fixed bed reactor for activity evaluation. A mixed gas containing nitrogen oxides, carbon monoxide, oxygen and ammonia was introduced into the reactor. The reaction conditions were: a volume space velocity of 30,000 h -1 , the temperature is 100~250℃. Figure 2As shown, at 175°C, the NO and CO conversion rates are 96.2% and 94.9%, respectively. Above 200°C, the NO and CO conversion rates are both 100%.

[0050] Example 3: Preparation of 25-2Ni-4Ce / AC-N catalyst (metal loading 25wt%, Ni:Ce atomic ratio = 2:4)

[0051] Take 30g of activated coke particles (20-40 mesh) and place them in a 63wt% nitric acid solution. After immersion for 6h, rinse with deionized water until neutral and place in a 105℃ oven to dry for 12h to obtain nitric acid-modified activated coke particles, recorded as AC-N. Mix 6.95gNi(NO3)2.6H2O (0.024mol) and 20.75gCe(NO3)3.6H2O (0.048mol) and dissolve them in deionized water. The volume of the mixed solution is approximately equal to 24ml. The modified activated coke is immersed in the mixed solution for 2h, then placed in a 105℃ oven to dry, and calcined in a tubular quartz furnace with nitrogen as the protective gas, calcination temperature of 400℃, calcination time of 2h, and obtain 25-2Ni-4Ce / AC-N catalyst.

[0052] 10 ml of the prepared catalyst was placed in a fixed bed reactor for activity evaluation. A mixed gas containing nitrogen oxides, carbon monoxide, oxygen and ammonia was introduced into the reactor. The reaction conditions were: a volume space velocity of 30,000 h -1 , the temperature is 100~250℃. Figure 3 As shown, at 175°C, the NO and CO conversion rates are 99.2% and 99%, respectively. Above 200°C, the NO and CO conversion rates are both 100%.

[0053] Example 4: Preparation of 20-2Ni-4Ce / AC-N catalyst (metal loading 20wt%, Ni:Ce atomic ratio = 2:4)

[0054] Take 30g of activated coke particles (20-40 mesh) and place them in a 63wt% nitric acid solution. After immersion for 6h, rinse with deionized water until neutral and place in a 105℃ oven to dry for 12h. Mix 5.23gNi(NO3)2.6H2O (0.018mol) and 15.58gCe(NO3)3.6H2O (0.036mol) and dissolve them in deionized water. The volume of the mixed solution is approximately equal to 24ml. The modified activated coke is immersed in the mixed solution for 2h, then placed in a 105℃ oven to dry, and calcined in a tubular quartz furnace with nitrogen as the protective gas, the calcination temperature is 400℃, and the calcination time is 2h.

[0055] 10 ml of the prepared catalyst was placed in a fixed bed reactor for activity evaluation. A mixed gas containing nitrogen oxides, carbon monoxide, oxygen and ammonia was introduced into the reactor. The reaction conditions were: a volume space velocity of 30,000 h-1 and a temperature of 100-250°C. Figure 4 As shown, when the temperature is higher than 175°C, the NO and CO conversion rates are both higher than 90%.

[0056] Figure 4 :20-2Ni-4Ce / AC-N catalyst NOx conversion rate and CO conversion rate change curve with inlet gas temperature

[0057] Example 5: Preparation of 30-1Ni-4Ce / AC-N catalyst (metal loading 20wt%, Ni:Ce atomic ratio = 1:4)

[0058] Take 30g of activated coke particles (20-40 mesh) and place them in a 63wt% nitric acid solution. After immersion for 6h, rinse with deionized water until neutral and place in a 105℃ oven to dry for 12h. Mix 4.95gNi(NO3)2.6H2O (0.017mol) and 29.51gCe(NO3)3.6H2O (0.068mol) and dissolve them in deionized water. The volume of the mixed solution is approximately equal to 24ml. The modified activated coke is immersed in the mixed solution for 2h, then placed in a 105℃ oven to dry, and calcined in a tubular quartz furnace with nitrogen as the protective gas, calcination temperature of 400℃, and calcination time of 2h.

[0059] 10 ml of the prepared catalyst was placed in a fixed bed reactor for activity evaluation. A mixed gas containing nitrogen oxides, carbon monoxide, oxygen and ammonia was introduced into the reactor. The reaction conditions were: a volume space velocity of 3000 h -1 , the temperature is 100~250℃. Figure 5 As shown, at 200°C, the conversion rate of NO is 94% and CO can reach 84%.

[0060] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A transition metal-supported modified activated coke bifunctional catalyst: The catalyst comprises a first component, a second component and modified activated coke that provides a physical carrier and synergistic or auxiliary catalytic effect to the first component and the second component, wherein: The first component is NiO; the second component is CeO2. The content of the first component in the catalyst is 3 to 30 wt%; The content of the second component in the catalyst is 3-20 wt%.

2. The catalyst according to claim 1, characterized in that: The modified active coke is the first component, and the second component provides a physical carrier and plays a synergistic or auxiliary catalytic role. Based on the total weight of the catalyst, the content of the modified active coke is 50-96wt%.

3. The catalyst according to claim 1, characterized in that: The atomic ratio of nickel to cerium in the first component and the second component is 1:10 to 10:

1.

4. The catalyst according to claim 1, characterized in that: The content of the first component in the catalyst is 5 to 15 wt %; The content of the second component in the catalyst is 5-15wt%; The modified activated coke is the first component, and the second component provides a physical carrier and plays a synergistic or auxiliary catalytic role. Based on the total weight of the catalyst, the content of the modified activated coke is 70-90wt%; The atomic ratio of nickel to cerium in the first component and the second component is 1:1 to 4:

1.

5. A method for preparing a catalyst as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: The acid-modified activated coke is used as a carrier, and the carrier is placed in a mixed aqueous solution of Ni and Ce inorganic salts, impregnated, dried, and calcined to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that: The acid-modified activated coke was prepared by excessively impregnating the sample with a nitric acid solution having a concentration of 63% at room temperature for 6 hours; the treated sample was rinsed to neutrality, placed in an oven at 105° C. and dried for 12 hours to obtain a modified activated coke sample.

7. The preparation method according to claim 5, characterized in that: The metal-supported catalysts were prepared by the isovolumetric impregnation method.

8. The preparation method according to claim 5, characterized in that: The impregnated activated coke sample was placed in an oven, dried at 105°C for 12 hours, and then placed in a quartz tube and calcined at 400°C for 2 hours in a nitrogen atmosphere to obtain a modified activated coke loaded with Ni and Ce bimetallic catalyst.

9. Use of the catalyst according to any one of claims 1 to 4 in simultaneously catalyzing the selective reduction of nitrogen oxides by ammonia and the oxidation of carbon monoxide.

10. The use according to claim 9, characterized in that: The application is application in eliminating nitrogen oxides and carbon monoxide emitted from flue gas.

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