CN112044448A - VOCs catalytic combustion monolithic metal foam catalyst and preparation and application thereof - Google Patents

VOCs catalytic combustion monolithic metal foam catalyst and preparation and application thereof Download PDF

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CN112044448A
CN112044448A CN202010856299.6A CN202010856299A CN112044448A CN 112044448 A CN112044448 A CN 112044448A CN 202010856299 A CN202010856299 A CN 202010856299A CN 112044448 A CN112044448 A CN 112044448A
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catalyst
toluene
temperature
nickel
foam
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卢晗锋
李剑宇
陈晓
周瑛
耿俊
胡中恒
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Zhejiang University of Technology ZJUT
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Zhejiang University of Technology ZJUT
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/892—Nickel and noble metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/30—Ion-exchange
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
    • F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
    • F23G7/07—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases in which combustion takes place in the presence of catalytic material

Abstract

The invention provides a noble metal monolithic catalyst, which takes foamed nickel as a carrier and Pt or Pd as an active component, wherein the mass loading of the active component is 0.1-1%; the catalyst is prepared by an ion exchange method, and the reaction temperature is 20-90 ℃; the preparation method of the noble metal monolithic foam nickel catalyst is simple and flexible, shows excellent activity in catalytic combustion of VOCs, and has excellent water resistance, thermal shock resistance and very high stability.

Description

VOCs catalytic combustion monolithic metal foam catalyst and preparation and application thereof
Technical Field
The invention relates to the technical field of catalytic combustion of organic waste gas, in particular to an integral metal catalyst prepared by directly replacing noble metal with ions.
Background
In recent years, with rapid urbanization and industrialization development, the environmental hazard caused by the emission of waste materials in production of various industries is increasingly serious, especially the emission of Volatile Organic Compounds (VOCs) in air pollution is gradually increased, and the exhaust becomes one of three main air pollutants in parallel with SOx and NOx, which mainly comes from petroleum refining, petrochemical processing, dye coating and various industries using organic solvents. Volatile Organic Compounds (VOCs) are a series of organic compounds having a saturated vapor pressure of greater than about 70Pa and a boiling point of 260 ℃ or less at normal temperature and pressure, such as toluene, ethyl acetate, acetaldehyde, and the like. The pollution hazard forms caused by the difference of the types and the properties of the organic matters are different, wherein most of discharged VOCs can cause the formation of secondary pollutants, such as tropospheric ozone, peroxyacetyl nitrate, secondary organic aerosol and the like, and the substances not only destroy the ecological balance, but also are toxic and carcinogenic, thereby causing great harm to the health and living environment of human beings. Therefore, when law and regulation policies such as energy conservation and emission reduction are implemented, research on efficient, economic, environment-friendly and practical VOCs treatment technology is very important in promoting harmonious development of economic and social environments.
With the severe environmental hazard and the improvement of environmental awareness, in recent years, countries release more and more strict industrial waste gas emission standards, wherein the ministry of environmental protection proposes that relevant pollution control strategies and methods should be adopted in the links of Volatile Organic Compounds (VOCs) production, transportation, sale and the like in the technical policy of pollution control of VOCs released in 2013. Currently, various technologies have been developed in the industry for the treatment of VOCs, which mainly include two main categories: one is a recovery method involving adsorption, absorption, membrane separation, condensation, and the like; another class is destruction methods involving catalytic combustion, thermodynamic incineration, biodegradation, photocatalytic decomposition, and plasma oxidation. However, due to the difference of the types of VOCs and the difference of environmental conditions of the exhaust emission sources, these technologies have limitations that only specific scenes can be processed in the using process. Such as condensation, membrane separation and adsorption, are commonly used in the chemical, pharmaceutical and synthetic material industries because of the inability to simultaneously process multiple VOCs gasesPurifying and recycling the discharged high-concentration VOCs; the biological treatment needs longer bed reaction time and is more suitable for deodorization in industries such as rubber, food and the like with lower VOCs content; the thermodynamic incineration technology is high in energy consumption requirement, large in equipment occupation volume and suitable for large-scale chemical enterprises such as petrochemical enterprises and the like; although the plasma and the photocatalysis technology do not need a large amount of energy consumption input and have mild reaction conditions, the purification efficiency is not high, and secondary pollution such as ozone is easy to generate. The catalytic combustion technology can enable VOCs to be deeply oxidized and completely degraded into harmless CO under mild conditions (generally 200-500 ℃) by applying the principle that the catalyst reduces the reaction activation energy2And H2O, not only energy-saving and environment-friendly, but also wide applicability, and is more and more favored and paid attention in recent years.
Obviously, the most critical part in the catalytic combustion technology is the catalyst, and the performance of the catalyst plays a decisive role in the removal effect of the VOCs and the energy consumption of the catalytic process. With the development of the theory in the field of catalysis and the progress of catalyst preparation technology, the structural form of the catalyst gradually develops from the traditional powder type to the particle type to the monolithic type widely used nowadays. Compared with the traditional powder type and particle type catalysts, the monolithic catalyst has the following advantages: (1) the heat transfer efficiency is high. The integral catalyst has thin wall and high aperture ratio, the direct pore channel greatly increases the contact area of the waste gas and the catalyst, the gas can quickly transfer heat to the surface, and the ignition time of the catalyst is reduced; (2) the mass transfer efficiency is high. The coating on the load type integral carrier has high specific surface area, the active components can be fully dispersed and distributed on the surface of the coating, the path of the reactant diffusing to the active center is shortened, and the influence of internal diffusion is reduced; (3) bed lamination is reduced. The geometrical configuration of the carrier reduces the resistance when the fluid passes through the catalyst bed layer, and the pressure of the gas flow is reduced; (4) the amplification effect is small. The difference between the laboratory and commercial catalysts is the number of channels. The catalytic combustion is mainly a gas-solid phase reaction, and the catalytic effect of the catalytic bed is obviously influenced by the properties of mass transfer, heat transfer and the like of the catalytic bed, so that the monolithic catalyst with the advantages is widely used as a catalytic combustion catalyst.
Of monolithic catalystsThe carrier is mainly divided into two categories of ceramic carrier and metal carrier according to different base materials, wherein the ceramic carrier mainly comprises cordierite, corundum, magnesium silicate and TiO2And SiC, etc., and the material generally used for the metal carrier is stainless steel or an alloy. The ceramic carrier is generally prepared into an integral body by mixing and doping different raw material powder and extrusion molding, and the appearance of the ceramic carrier is generally honeycomb-shaped, such as cordierite honeycomb ceramic, silicon carbide honeycomb ceramic and the like; the metal carrier can be prepared into various shapes such as metal wires, metal nets, metal foams and the like due to good ductility, tensile strength and compressive strength. Compared with the defects of slow heat transfer and temperature rise, poor mechanical property and the like of a ceramic carrier, the metal carrier has more excellent properties, mainly comprising the following components: (1) the metal support has a larger geometric surface area; (2) the metal carrier is not controlled by the shape of the metal carrier, and has adjustable structure; (3) the metal carrier has good conductivity and high mechanical strength; (4) the metal carrier has high heat conductivity, the catalytic combustion has high ignition speed, and the catalyst can play a role quickly. Therefore, monolithic catalysts prepared with metal supports are increasingly being studied and used in the field of catalytic combustion.
The monolithic catalyst generally comprises a carrier and an active component, wherein the carrier is a support place of the catalyst and provides a place for supporting the active component and reacting a circulating material; the active component is the main component of the catalyst to provide combined active sites for the reaction of materials. The noble metal catalyst is prepared by taking a metal salt precursor as a raw material, introducing the precursor onto a carrier by an impregnation or coating method, and reducing the precursor into a metal simple substance state, wherein Pt and Pd are the most widely studied elements in VOCs (volatile organic compounds) for noble metal catalytic combustion, and the research proves that C is the most widely studied element for C2-C8The organic matter has excellent catalytic degradation effect.
The metal carrier has the advantages of good plasticity, high mechanical strength, high heat transfer rate and the like, is widely applied to catalytic combustion catalysts, particularly foam metal has a unique three-dimensional network structure and rich specific surface area, and provides a good substrate for the preparation of the supported catalyst. However, the surface of the metal carrier is smooth, the thermal expansion rate is high, the traditional coating preparation method is complex, the coating is not firm, and the adhesion with the carrier is poor. In addition, the existing noble metal catalyst has complex loading mode of active components, high requirement on the types of carrier materials and difficult rapid and convenient industrial scale-up production.
Therefore, in order to solve the above problems, we research literature and summarize previous working experience, and select nickel foam as a carrier, and replace active components such as elemental metals Pt and Pd on the surface of the nickel foam metal carrier by a simple ion exchange method, and dry the active components to prepare the noble metal monolithic catalyst. On the basis, the performance difference of the foam metal prepared into the catalyst by the ion exchange method on the catalysis of VOCs is also researched. The results of these studies can provide reference for corresponding applications in industry.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a noble metal monolithic catalyst, a preparation method and an application thereof, wherein the active site of the catalyst is provided by noble metal, and the catalyst can efficiently and quickly degrade high-concentration VOCs into CO under the conditions of relatively low temperature and mild condition2And H2O，T90Can reach about 220 ℃, and the conversion rate can stably reach more than 99%.
The technical scheme of the invention is as follows:
a noble metal monolithic catalyst takes foam nickel as a carrier, Pt or Pd as an active component, and the mass loading capacity of the active component is 0.1-1%; the catalyst is prepared by an ion exchange method, and the reaction temperature is 20-90 ℃.
Specifically, the preparation method of the noble metal monolithic catalyst comprises the following steps:
adding the pretreated nickel foam into an active component precursor solution, carrying out immersion displacement at 20-90 ℃, measuring the absorbance of the solution by using an ultraviolet spectrophotometer to monitor the reaction process, finishing the reaction when the absorbance of the solution is not changed any more, filtering, and drying to obtain the noble metal monolithic catalyst;
the method for pretreating the foamed nickel comprises the following steps: firstly, placing foamed nickel in acetone for ultrasonic oscillation for 30min to remove surface oil stains, then taking out the foamed nickel and washing the foamed nickel by using deionized water, and then sequentially placing the foamed nickel in 10-30 wt% of NaOH aqueous solution and 10-30 wt% of HNO3Ultrasonic oscillation is carried out in the water solution for 30min to remove an oxide layer on the surface of the foamed nickel, then the foamed nickel is washed clean by deionized water and is dried in a drying oven for 2-24h at 110 ℃, and the pretreatment is finished;
the active component precursor solution is chloroplatinic acid aqueous solution or chloropalladite aqueous solution, and the mass of Pt or Pd in the active component precursor solution is 0.1-1% of that of the foamed nickel;
when the active component is Pt, monitoring the reaction process by measuring the absorbance of the solution at 263nm by an ultraviolet spectrophotometer;
when the active component was Pd, the progress of the reaction was monitored by measuring the absorbance of the solution at 310nm by an ultraviolet spectrophotometer.
The noble metal monolithic catalyst can be applied to degrading VOCs. Specifically, the application method comprises the following steps:
mixing toluene and air to serve as intake air, controlling the flow of the toluene to be 37-150mL/min through a flow meter by using a noble metal integral foam nickel combustion catalyst, adjusting the concentration of the toluene to be 2000ppm through air flow, controlling the total flow of the gas to be 166-666mL/min, controlling the reaction space velocity to be 5000-20000/h, raising the temperature to 160-300 ℃ at the speed of 5 ℃/min, stabilizing the temperature for 30min every 20 ℃, and then continuing to raise the temperature to degrade the toluene;
alternatively, the first and second electrodes may be,
mixing ethyl acetate and air to serve as intake air, controlling the flow rate of the ethyl acetate to be 9.98mL/min through a flow meter by using a noble metal integral foam nickel combustion catalyst, adjusting the air flow to enable the concentration of the ethyl acetate to be 2000ppm, controlling the total flow rate of the gas to be 166mL/min, controlling the reaction space velocity to be 5000/h, raising the temperature to 160-300 ℃ at the speed of 5 ℃/min, stabilizing the temperature for 30min at intervals of 20 ℃, and then continuing to raise the temperature to degrade the ethyl acetate.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention prepares the noble metal integral foam nickel catalyst by ion exchangeThe catalyst and the preparation method are simple and flexible, the catalyst has excellent activity in catalytic combustion of toluene and ethyl acetate, and 0.2 percent of Pt/Ni-foam catalyzes and combusts toluene T under the conditions of 5000/h and 2000ppm50＝200℃，T90Catalytic combustion of ethyl acetate at about 220 ℃ T50＝240℃，T90About 260 ℃, 0.2 percent Pd/Ni-foam catalyzes the combustion of toluene T under the conditions of 5000/h and 2000ppm50＝220℃，T90Catalytic combustion of ethyl acetate at about 240 ℃ of50＝260℃，T90About 300 ℃, and the conversion rate can stably reach more than 99%.
(2) The catalyst exhibits excellent water resistance and the catalytic activity remains substantially unchanged in the presence of moisture.
(3) The catalyst also has good thermal shock resistance, and after being roasted at 800 ℃ for 5 hours, the complete conversion temperature moves backwards to be about 40 ℃, and the catalytic effect can still be maintained by more than 80%.
(4) After 12h of cyclic experimental tests, the catalyst is found to have very high stability in the process of catalytically combusting toluene and ethyl acetate.
(5) The catalyst shows excellent catalytic combustion activity in the process of treating toluene and ethyl acetate at high space velocity of 5000-.
(6) The catalyst can treat VOCs in an actual factory under a high airspeed condition, the activity of the catalyst cannot be influenced even in an environment with a large amount of moisture, and the catalyst has extremely high thermal shock resistance and stability.
Drawings
FIG. 1a is a graph of catalytic combustion activity of 0.2% Pt/Ni-foam and 0.2% Pd/Ni-foam on toluene at GHSV of 5000h-1，C＝2000ppm。
FIG. 1b is a graph of the activity of 0.2% Pt/Ni-foam and 0.2% Pd/Ni-foam for catalytic combustion of ethyl acetate at GHSV of 5000h-1，C＝2000ppm。
FIG. 2a is a graph showing the activity of 0.2% Pt/Ni-foam after stabilization at 240 ℃ for 20min, with addition of water vapor at 80% humidity to catalyze toluene, and GHSV of 5000h-1，C＝2000ppm。
FIG. 2b is a graph showing the activity of 0.2% Pd/Ni-foam after stabilization at 240 ℃ for 20min, and water vapor with 80% humidity is added to catalyze toluene, and GHSV is 5000h-1，C＝2000ppm。
FIG. 3 is a graph of catalytic combustion toluene activity for aging test of 0.2% Pt/Ni-foam catalyst and 0.2% Pd/Ni-foam catalyst at GHSV of 5000h-1，C＝2000ppm。
FIG. 4a is a graph of the stability of 0.2% Pt/Ni-foam catalyst in catalyzing toluene at 240 ℃ under GHSV of 5000h-1，C＝2000ppm。
FIG. 4b is a graph of the stability of 0.2% Pd/Ni-foam catalyst in catalyzing toluene at 240 deg.C, GHSV 5000h-1，C＝2000ppm。
FIG. 5a is a graph of catalytic toluene activity of 0.2% Pt/Ni-foam catalyst at different space velocities with GHSV of 5000h-1，C＝2000ppm。
FIG. 5b is a graph of catalytic toluene activity of 0.2% Pd/Ni-foam catalyst at different space velocities, GHSV of 5000h-1，C＝2000ppm。
FIG. 6a is a graph of the catalytic activity of 0.2% Pt/Ni-foam catalyst at different reaction temperatures for toluene at GHSV of 5000h-1，C＝2000ppm。
FIG. 6b is the activity diagram of 0.2% Pd/Ni-foam catalyst in catalyzing toluene at different reaction temperatures, GHSV is 5000h-1，C＝2000ppm。
FIG. 7 is a schematic diagram of a VOCs catalytic combustion apparatus, 1 air cylinder, 2 flow meters, 3 toluene/ethyl acetate bubble bottles, 4U-shaped reaction tubes, 5 gas chromatography.
FIG. 8a is an EDS energy spectrum of a 0.2% Pt/Ni-foam catalyst.
FIG. 8b is the EDS energy spectrum of 0.2% Pd/Ni-foam catalyst.
Detailed Description
The invention will be further described in the following by means of specific embodiments with reference to the attached drawings, to which, however, the scope of protection of the invention is not limited.
The room temperature is 20-30 ℃.
The foam nickel used in the embodiment of the invention is a catalyst carrier, is integral foam nickel from Changshafei Limited, has the specification of a cuboid of 10 multiplied by 20mm, has a PPI of 50, has a density of 0.45g/mL, weighs 0.9g, and has a volume of 2 mL.
The preparation method of the noble metal monolithic catalyst comprises the following steps:
(1) preparation of chloroplatinic acid solution: weighing 1.66-8.3 g of H2PtCl6·6H2Dissolving O in 250ml of water to prepare a mother liquor of 2.5-12.5 g/L (based on the mass of platinum), and preparing chloroplatinic acid solutions of different concentrations from the mother liquor of 2.5-12.5 g/L to serve as immersion adsorption solutions.
(2) Preparation of chloropalladate solution: weighing 0.5-2.5 g of PdCl2Dissolving the raw materials in 100ml of water, adding 2.78-13.9 ml of 2.0mol/L HCl solution, heating the mixed solution until the raw materials are dissolved, finally, preparing 250ml of mother solution with the concentration of 1.2-6 g/L (based on the mass of palladium), and preparing chloropalladate solutions with different concentrations from 1.2-6 g/L of the mother solution to be used as impregnation adsorption solutions.
(3) Pretreatment of foamed nickel: firstly, placing foamed nickel in acetone, ultrasonically vibrating for 30min to remove surface oil stains, taking out the foamed nickel after the ultrasonic vibration is finished, washing the foamed nickel with deionized water for three times, and then sequentially placing the foamed nickel in prepared 10% -30% NaOH and 10% -30% HNO3And ultrasonically oscillating the solution for 30min to remove an oxide layer on the surface of the foamed nickel, taking out the foamed nickel after the operation is finished, washing the foamed nickel by using deionized water, and drying the foamed nickel in a drying oven at 110 ℃ for 2-24 h.
(4) Mixing 0.36-3.6 ml of the platinum mother liquor in the step (1) (calculating the amount of a Pt simple substance by using 0.1-1% of the mass fraction of 0.9g of foamed nickel) and 6.4-9.64 ml of water to prepare 10ml of solution in a centrifuge tube, putting the foamed nickel pretreated in the step (3) into the centrifuge tube, soaking and replacing in water bath at 20-90 ℃, measuring the absorbance of the solution at 263nm by using an ultraviolet spectrophotometer every 1h, reacting until the absorbance of the solution is not changed, filtering, and drying for 2h at 110 ℃ to obtain the catalyst with the load of 0.1-1% under the condition of 20-90 ℃ for reaction.
(5) Mixing 0.75-7.5 ml of palladium mother liquor (the mass fraction of 0.1-1% of 0.9g of foamed nickel is used for calculating the amount of a Pd simple substance) in the step (2) with 2.5-9.25 ml of water to prepare 10ml of solution in a centrifuge tube, putting the foamed nickel pretreated in the step (3) into the centrifuge tube, soaking and replacing in water bath at 20-90 ℃, measuring the absorbance of the solution at 310nm by using an ultraviolet spectrophotometer every 1h, reacting until the absorbance of the solution is not changed, filtering, and drying for 2h at 110 ℃ to obtain the catalyst with the loading amount of 0.1-1% under the condition of 20-90 ℃ for reacting.
The invention adopts a VOCs catalytic combustion device for testing the catalyst, and the device comprises an air steel bottle 1, a flowmeter 2, a toluene/ethyl acetate bubbling bottle 3, a U-shaped reaction tube 4 and a gas chromatograph 5;
the air steel cylinder 1 is communicated with an air inlet of the bubbling bottle 3 through a pipeline with a flow meter, and meanwhile, the air steel cylinder 1 is communicated with an air inlet of the U-shaped reaction tube 4 after being communicated with an air outlet pipeline of the bubbling bottle 3 through a pipeline with a flow meter, and an air outlet of the U-shaped reaction tube 4 is connected with the gas chromatograph 5;
the U-shaped reaction tube is arranged in a temperature programmed heating furnace; adding the noble metal monolithic foam nickel catalyst into a U-shaped reaction tube, introducing a mixed gas of air and toluene/ethyl acetate bubbling steam into an air inlet of the U-shaped reaction tube, introducing an air outlet of the U-shaped reaction tube into a gas chromatograph, and placing the U-shaped reaction tube in a heating furnace capable of programming temperature; the amount of the catalyst charged into the U-shaped reaction tube was 0.9 g.
Example 1
Taking 0.72ml of mother liquor of 2.5g/L (based on the mass of platinum) and 9.28ml of water to mix and prepare 10ml of solution in a centrifuge tube, putting 0.9g of pretreated foamed nickel into the centrifuge tube, immersing and replacing the foam in a water bath at 20 ℃, measuring the concentration change of the solution by an ultraviolet spectrophotometer every 10min until the concentration of Pt ions becomes 0, filtering and drying the solution, and recording the obtained product as 0.2% Pt/Ni-foam-20 ℃.
Example 2
The conditions were the same as in example 1, and the bath temperature was changed to 30 ℃ and was recorded as 0.2% Pt/Ni-foam-30 ℃.
Example 3
The conditions were the same as in example 1, the bath temperature was changed to 40 ℃ and was recorded as 0.2% Pt/Ni-foam-40 ℃.
Example 4
The conditions were the same as in example 1, and the bath temperature was changed to 50 ℃ and was recorded as 0.2% Pt/Ni-foam-50 ℃.
Example 5
The conditions were the same as in example 1, and the bath temperature was changed to 60 ℃ and was recorded as 0.2% Pt/Ni-foam-60 ℃.
Example 6
The conditions were the same as in example 1, and the bath temperature was changed to 70 ℃ and was recorded as 0.2% Pt/Ni-foam-70 ℃.
Example 7
The conditions were the same as in example 1, and the bath temperature was changed to 80 ℃ and was recorded as 0.2% Pt/Ni-foam-80 ℃.
Example 8
The conditions were as in example 1, with the bath temperature changed to 90 ℃ and was recorded as 0.2% Pt/Ni-foam-90 ℃.
Example 9
Mixing 1.5ml of mother liquor 1.2g/L (based on the mass of palladium) with 8.5ml of water to prepare 10ml of solution in a centrifuge tube, putting 0.9g of pretreated foamed nickel into the centrifuge tube, performing immersion displacement in a water bath at 20 ℃, measuring the concentration change of the solution by an ultraviolet spectrophotometer every 10min until the concentration of Pd ions becomes 0, filtering, drying, and recording the obtained product as 0.2% Pd/Ni-foam-20 DEG C
Example 10
The conditions were as in example 9, and the bath temperature was changed to 30 ℃ and was noted as 0.2% Pd/Ni-foam-30 ℃.
Example 11
The conditions were as in example 9, and the bath temperature was changed to 40 ℃ and was noted as 0.2% Pd/Ni-foam-40 ℃.
Example 12
The conditions were as in example 9, and the bath temperature was changed to 50 ℃ and was noted as 0.2% Pd/Ni-foam-50 ℃.
Example 13
The conditions were as in example 9, and the bath temperature was changed to 60 ℃ and was noted as 0.2% Pd/Ni-foam-60 ℃.
Example 14
The conditions were as in example 9, and the bath temperature was changed to 70 ℃ and was noted as 0.2% Pd/Ni-foam-70 ℃.
Example 15
The conditions were as in example 9, and the bath temperature was changed to 80 ℃ and was recorded as 0.2% Pd/Ni-foam-80 ℃.
Example 16
The conditions were as in example 9, and the bath temperature was changed to 90 ℃ and was recorded as 0.2% Pd/Ni-foam-90 ℃.
Example 17 Water resistance test
Referring to fig. 7, a VOCs catalytic combustion apparatus is adopted, and the apparatus comprises an air steel cylinder 1, a flowmeter 2, a toluene/ethyl acetate bubbling bottle 3, a U-shaped reaction tube 4 and a gas chromatograph 5; the air steel cylinder 1 is communicated with an air inlet of a toluene/ethyl acetate bubbling bottle 3 through a pipeline with a mass flow meter, meanwhile, the air steel cylinder 1 is communicated with an air inlet of a U-shaped reaction tube 4 after being communicated with an air outlet pipeline of the toluene/ethyl acetate bubbling bottle 3 through a pipeline with a mass flow meter, and an air outlet of the U-shaped reaction tube 4 is connected with a gas chromatograph 5; the U-shaped reaction tube is arranged in a temperature programmed heating furnace.
The monolithic catalysts prepared in example 2 and example 14 were added to a U-shaped reaction tube (the amount of catalyst added was 0.9g), and a steam generator was provided to mix steam with toluene steam at the outlet of the bubbler 3, i.e., a mixed gas of steam and toluene steam was introduced into one side of the U-shaped reaction tube, and the other side thereof was introduced into a gas chromatograph, and the U-shaped reaction tube was placed in a heating furnace capable of programmed temperature rise. Toluene catalytic combustion experimental conditions: the U-shaped reaction tube is heated from room temperature to 240 ℃ at the speed of 5 ℃/min, the flow rate of toluene is controlled to be 37ml/min through a flowmeter, the flow rate of water vapor is 129ml/min, the total flow rate of gas entering the U-shaped reaction tube is 166ml/min, the concentration of toluene is 2000ppm, and the reaction space velocity is 5000/h. Detecting the concentration of toluene in the tail gas at different time, and recording the toluene peak area value as C at room temperature0The peak area of toluene at each detection time was C1Percent conversion is 1- (C)1/C0) Percent, the gas chromatography detection conditions were: sample inlet temperature 250 ℃, detector temperature 300 ℃, column box temperature 200 ℃, capillary column model: agilent HP-INNOWAX, mobile phase: nitrogen gas.
As can be seen from fig. 2, the catalysts prepared by examples 2 and 14 have excellent water resistance.
Example 18 Activity assay
Example 2 and exampleThe monolithic catalyst prepared in example 14 was charged into a U-shaped reaction tube (catalyst charge of 0.9g), and the experimental conditions for catalytic combustion of toluene and ethyl acetate were as follows: the U-shaped reaction tube is heated from room temperature to 300 ℃ at the speed of 5 ℃/min, the temperature is raised by 20 ℃ for 30min, the flow rate of toluene is controlled to be 37ml/min through a flowmeter, the air flow is 129ml/min, the total flow rate of gas entering the U-shaped reaction tube is 166ml/min, the concentration of toluene is 2000ppm, and the reaction airspeed is 5000/h; the flow rate of ethyl acetate is 10ml/min, the air flow rate is 156ml/min, the total flow rate of gas entering the U-shaped reaction tube is 166ml/min, the concentration of ethyl acetate is 2000ppm, and the reaction space velocity is 5000/h. Detecting the concentration of toluene/ethyl acetate in the tail gas at different temperatures, and recording the peak area value of toluene/ethyl acetate as C at room temperature0And the peak area of toluene/ethyl acetate at each detection temperature is C1Percent conversion is 1- (C)1/C0)％。
As can be seen from FIG. 1, the catalysts prepared by example 2 and example 14 have good catalytic activities for toluene and ethyl acetate.
EXAMPLE 19 thermal shock resistance test
The catalysts prepared in the examples 2 and 14 are roasted in a muffle furnace at 800 ℃ for 5h, taken out and cooled, and then added into a U-shaped reaction tube, and the experimental conditions of the catalytic combustion of toluene are as follows: the U-shaped reaction tube is heated from room temperature to 300 ℃ at the speed of 5 ℃/min, the temperature is raised by 20 ℃ for 30min, the flow rate of toluene is controlled to be 37ml/min through a flowmeter, the air flow is 129ml/min, the total flow rate of gas entering the U-shaped reaction tube is 166ml/min, the concentration of toluene is 2000ppm, the reaction space velocity is 5000/h, the concentration of toluene in tail gas at different temperatures is detected, and the peak area value of toluene is recorded as C at room temperature0The peak area of toluene at each detection temperature was C1Percent conversion is 1- (C)1/C0)％。
As a result, as shown in FIG. 3, it can be seen that the activity of the catalyst after calcination at 800 ℃ was not decreased, demonstrating that the catalyst has good thermal shock resistance.
Example 20 stability testing
The catalysts prepared in example 2 and example 14 were added into a U-shaped reaction tube for testing the stability of degraded toluene, after the U-shaped reaction tube was heated from room temperature to 240 ℃ at a speed of 5 ℃/min, the flow rate of toluene was controlled by a flow meter to be 37ml/min and the flow rate of air to be 129ml/min, so that the total flow rate of gas entering the U-shaped reaction tube was 166ml/min, the concentration of toluene was 2000ppm, and the reaction space velocity was 5000/h. The reaction was continued for 12h and the toluene concentration was measured at different times.
The results are shown in fig. 4, and the catalysts prepared in example 2 and example 14 have good stability.
Example 21 Activity test at high airspeed
The monolithic catalysts prepared in example 2 and example 14 were charged into a U-shaped reaction tube (catalyst charge of 0.9g), and the toluene catalytic combustion test conditions: the U-shaped reaction tube is heated from room temperature to 300 ℃ at the speed of 5 ℃/min, the temperature per liter is raised by 20 ℃ for 30min, the flow rate of toluene is controlled to be 37-150ml/min through a flow meter, the concentration of toluene is 2000ppm through the adjustment of air flow, the total flow rate of gas is 666ml/min, the reaction space velocity is 5000-. Detecting the concentration of toluene in the tail gas at different temperatures, and recording the peak area value of toluene as C at room temperature0The peak area of toluene at each detection temperature was C1Percent conversion is 1- (C)1/C0)％。
The results are shown in fig. 5, and the catalysts prepared in example 2 and example 14 still have good catalytic activity at a large space velocity.
Example 21 Activity test at different reaction temperatures
The monolithic catalysts prepared in examples 1 to 8 and examples 9 to 16 were charged into a U-shaped reaction tube (catalyst charge of 0.9g), and the toluene catalytic combustion test conditions: the U-shaped reaction tube is heated from room temperature to 300 ℃ at the speed of 5 ℃/min, the temperature is raised by 20 ℃ for 30min, the flow rate of toluene is controlled to be 37ml/min through a flowmeter, the air flow is 129ml/min, the total flow rate of gas entering the U-shaped reaction tube is 166ml/min, the concentration of toluene is 2000ppm, and the reaction space velocity is 5000/h. Detecting the concentration of toluene in the tail gas at different temperatures, and recording the peak area value of toluene as C at room temperature0Each ofThe peak area of toluene at each detection temperature is C1Percent conversion is 1- (C)1/C0)％。
The results are shown in FIG. 6, the activity of the catalysts prepared in examples 1-8 and examples 9-16 at different reaction temperatures.
Comparative example 1
Putting pretreated foamed nickel (0.9g) into a VOCs catalytic combustion device for evaluating activity, raising the temperature to 300 ℃ at the speed of 5 ℃/min, raising the temperature by 20 ℃ per liter, stabilizing for half an hour, then continuing to raise the temperature, controlling the flow of toluene to be 37ml/min and the flow of air to be 129ml/min through a flowmeter, and enabling the total flow of gas entering a U-shaped reaction tube to be 166ml/min, the concentration of toluene to be 2000ppm and the reaction space velocity to be 5000/h; the flow rate of ethyl acetate is 10ml/min, the air flow rate is 156ml/min, the total flow rate of gas entering the U-shaped reaction tube is 166ml/min, the concentration of ethyl acetate is 2000ppm, and the reaction space velocity is 5000/h. Detecting the concentration of toluene/ethyl acetate at different temperatures, and recording the peak area value of toluene/ethyl acetate as C at room temperature0And the peak area of toluene/ethyl acetate at each detection temperature is C1Percent conversion is 1- (C)1/C0) % of the total weight of the composition. The results show that the conversion rate of the foamed nickel to toluene/ethyl acetate is zero in the range of 20-300 ℃.
Comparative example 2
Li et al (Hap Li, Yue Wang, Xiao Chen, et al, preparation of Metallic Monolithic Pt/FeCrAl Fiber Catalyst by catalysis Spraying for VOCs Combustion [ J ]. RSC Advances,2018,8(27):14806-14811.) have recently reported a novel method for preparing Monolithic metal catalysts by first preparing a noble metal Pt into a highly dispersed nanosol, and then uniformly spraying the nano sol liquid onto a metal carrier with a prepared coating in a spraying mode, researching the performance of the nano sol liquid in catalyzing and burning toluene, selecting iron, chromium and aluminum as the carrier, growing an alumina coating on the surface of the carrier by using a high-temperature oxidation method, preparing Pt nano particle sol dispersed in volatile solvent n-hexane by using a solvothermal method, finally spraying the nano sol onto the iron, chromium and aluminum carrier with the prepared coating, and drying and roasting to obtain the Pt-loaded integral metal catalyst. The monolithic catalyst 0.1Pt/FeCrAl has excellent catalytic activity on toluene, wherein the concentration of toluene in inlet gas is 2500ppm, and the complete conversion temperature can reach 280 ℃ under the condition that the space velocity is 10000 mL/g.h.
In conclusion, compared with the method of nano sol, the ion exchange method used in the invention has the advantages of simple preparation method, no need of high-temperature roasting in the process, better catalytic toluene activity effect, and T of the ion exchange method90220 ℃ C, T of nanosol method90＝280℃。

Claims (6)

1. The noble metal monolithic catalyst is characterized in that foam nickel is used as a carrier, Pt or Pd is used as an active component, and the mass loading amount of the active component is 0.1-1%; the catalyst is prepared by an ion exchange method, and the reaction temperature is 20-90 ℃.
2. The method of preparing a noble metal monolithic catalyst according to claim 1, wherein the method comprises:
adding the pretreated nickel foam into an active component precursor solution, carrying out immersion displacement at 20-90 ℃, measuring the absorbance of the solution by using an ultraviolet spectrophotometer to monitor the reaction process, finishing the reaction when the absorbance of the solution is not changed any more, filtering, and drying to obtain the noble metal monolithic catalyst;
the active component precursor solution is chloroplatinic acid aqueous solution or chloropalladite aqueous solution, and the mass of Pt or Pd in the active component precursor solution is 0.1-1% of the mass of the foamed nickel.
3. The method of claim 2, wherein the nickel foam is pretreated by: firstly, placing foamed nickel in acetone for ultrasonic oscillation for 30min to remove surface oil stains, then taking out the foamed nickel and washing the foamed nickel by using deionized water, and then sequentially placing the foamed nickel in 10-30 wt% of NaOH aqueous solution and 10-30 wt% of HNO3And ultrasonically oscillating the water solution for 30min to remove an oxide layer on the surface of the foamed nickel, then washing the foamed nickel clean with deionized water, and drying the foamed nickel for 2-24h at 110 ℃ in a drying oven to finish pretreatment.
4. The preparation method according to claim 2, wherein when the active component is Pt, the progress of the reaction is monitored by measuring absorbance of the solution at 263nm by an ultraviolet spectrophotometer; when the active component was Pd, the progress of the reaction was monitored by measuring the absorbance of the solution at 310nm by an ultraviolet spectrophotometer.
5. Use of the noble metal monolithic catalyst of claim 1 for the degradation of VOCs.
6. The application of claim 5, wherein the method of applying is:
mixing toluene and air to serve as intake air, controlling the flow of the toluene to be 37-150mL/min through a flow meter by using a noble metal integral foam nickel combustion catalyst, adjusting the concentration of the toluene to be 2000ppm through air flow, controlling the total flow of the gas to be 166-666mL/min, controlling the reaction space velocity to be 5000-20000/h, raising the temperature to 160-300 ℃ at the speed of 5 ℃/min, stabilizing the temperature for 30min every 20 ℃, and then continuing to raise the temperature to degrade the toluene;
alternatively, the first and second electrodes may be,
mixing ethyl acetate and air to serve as intake air, controlling the flow rate of the ethyl acetate to be 9.98mL/min through a flow meter by using a noble metal integral foam nickel combustion catalyst, adjusting the air flow to enable the concentration of the ethyl acetate to be 2000ppm, controlling the total flow rate of the gas to be 166mL/min, controlling the reaction space velocity to be 5000/h, raising the temperature to 160-300 ℃ at the speed of 5 ℃/min, stabilizing the temperature for 30min at intervals of 20 ℃, and then continuing to raise the temperature to degrade the ethyl acetate.
CN202010856299.6A 2020-08-24 2020-08-24 VOCs catalytic combustion monolithic metal foam catalyst and preparation and application thereof Pending CN112044448A (en)

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