CN108837823B - Perovskite type catalyst and integral forming method and application thereof - Google Patents

Perovskite type catalyst and integral forming method and application thereof Download PDF

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CN108837823B
CN108837823B CN201810618379.0A CN201810618379A CN108837823B CN 108837823 B CN108837823 B CN 108837823B CN 201810618379 A CN201810618379 A CN 201810618379A CN 108837823 B CN108837823 B CN 108837823B
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mixing
drying
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powder
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CN108837823A (en
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沙宇
李作金
詹吉山
于海波
陈潇
周英浩
胡进
孙康
初乃波
黎源
华卫琦
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Wanhua Chemical Group Co Ltd
Wanhua Chemical Ningbo Co Ltd
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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
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/32—Manganese, technetium or rhenium
    • B01J23/34—Manganese
    • 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
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • 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
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
    • 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
    • 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
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2209/00—Specific waste
    • F23G2209/14—Gaseous waste or fumes

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Abstract

The invention provides a perovskite catalyst and an integral forming method and application thereof, wherein the perovskite catalyst comprises 30-65 wt% of active components and 35-70 wt% of carrier alumina; the general formula of the active component is AXB1‑XCO3The integral forming method comprises the steps of 1) mixing metal salt, an alkaline precipitator, an organic pore-forming agent and water, reacting to obtain a precipitate, and filtering, washing, drying and roasting the precipitate to obtain active component powder; 2) grinding and sieving the active component powder obtained in the step 1) to obtain active component powder, and mixing the active component powder with an acid solution, alumina, sesbania powder and water to obtain a wet mass; 3) carrying out vacuum mixing and extrusion molding on the wet material mass obtained in the step 2) to obtain a honeycomb-shaped wet base blank; 4) drying and calcining the honeycomb-shaped wet base blank body obtained in the step 3) to obtain the perovskite type catalyst. The perovskite catalyst prepared by the invention can be applied to removal of industrial volatile organic compounds.

Description

Perovskite type catalyst and integral forming method and application thereof
Technical Field
The invention belongs to the technical field of catalysis, and particularly relates to a perovskite type catalyst, and an integral forming method and application thereof.
Background
With the rapid development of economy in China, particularly the development of chemical industry and manufacturing industry, the emission amount of volatile organic compounds is continuously increased, most of harmful gases are flammable and explosive, the emission amount of the harmful gases has serious influence on local ecological environment and global environment, the harmful gases are the reasons for causing atmospheric photochemical smog, greenhouse effect and ozone layer destruction, and the direct emission inevitably causes serious environmental pollution. At present, tail gas in the chemical industry is treated by adopting a direct emission method or a direct combustion method in China, the requirement of sustainable development of enterprises cannot be met, and the catalytic combustion technology has the advantages of low ignition temperature, recoverable waste heat, low energy consumption, good selectivity and the like, and is inevitably the mainstream of the waste gas purification technology in the petrochemical industry in future.
The principle of treating waste gas by catalytic combustion method is that the active components of catalyst are used to make oxygen molecules in air adsorb and activate, and the adsorbed active center reacts with reactant, so that it can form intermediate transition state, and after the reaction path is changed, the activation energy can be reduced, so that a combustion decomposition condition can be formed at a lower temperature, and the pollutant can be finally produced into harmless substance.
At present, the catalysts used for catalytic purification of VOCs at home and abroad are mainly concentrated on noble metals and supported catalysts thereof in the early stage, and although the materials have excellent catalytic effect, the resources are rare and the price is high, so that the large-scale application of the materials in the field of waste gas treatment is limited. Research focuses on transition metal and non-noble metal catalysts, and researches show that the perovskite type composite oxide with low cost has the advantages of high activity, toxicity resistance and heat resistance, is suitable for catalyzing and burning complex and high-concentration VOCs waste gas, and is expected to become one of substitutes of noble metal catalysts.
At present, the research in laboratories mostly focuses on the activity evaluation of the powder catalyst, but the synthesized catalyst powder is difficult to be directly applied, and the final solid catalyst needs to be molded to have certain shape, size and industrial strength. The honeycomb monolithic catalyst is more and more favored by people due to the advantages of low pressure drop, large surface area per unit reactor volume, high catalyst efficiency, remarkably improved reaction selectivity, small amplification effect and the like.
The preparation of the honeycomb monolithic catalyst has two modes of immobilization and self-molding: immobilization is to fix a catalyst powder on the surface of a honeycomb carrier (ceramic, metal, etc.) having a certain structure and mechanical strength by coating, hydrothermal growth, or the like. For example, patent CN1058357 describes a solution impregnation method, which comprises impregnating a cordierite carrier in a solution containing a metal salt at a certain concentration, and then drying and calcining the carrier to obtain a monolithic catalyst with a certain loading amount, wherein the catalyst is uniformly loaded and is simple to operate, but the active component of the catalyst interacts with the cordierite carrier during the preparation process, so that the formed perovskite structure is not complete enough, resulting in low catalyst activity. Patent 200810163774.0 discloses a method for forming a perovskite catalyst, which comprises the main steps of coating preparation, coprecipitation, impregnation, calcination, etc., and has the greatest disadvantage of complicated preparation process and difficulty in industrial production. Patent 201410064103.4 discloses dissolving metal salts in an aluminum sol, then immersing a shaped carrier in the aluminum sol solution for multiple soakings and calcinations to obtain a supported catalyst, wherein the monolithic catalyst has a high catalytic activity for catalytic combustion reaction of methane, but the supported amount of the catalyst is small, and the activity is decreased due to easy loss of active components. CN101905145 introduces a self-forming method of a molecular sieve honeycomb material, which is formed by mixing and bonding a molecular sieve, an adhesive and dilute acid.
In a word, the monolithic molecular sieve catalyst prepared by the immobilization method has uniform distribution of active components, but cannot overcome the defect that the active components fall off due to less active components and different thermal expansion coefficients of a carrier and catalyst raw powder.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a perovskite catalyst and an integral forming method thereof, wherein a self-forming method, namely a direct forming method is adopted to uniformly mix a powdery active component with raw materials such as a binder, a peptizing agent, water and the like to prepare a mud-shaped blank with certain viscosity and fluidity, and then the honeycomb perovskite catalyst is prepared through processes such as extrusion, drying, calcination and the like. The perovskite catalyst prepared by the invention can be applied to removal of industrial volatile organic compounds.
The technical scheme of the invention is as follows:
the perovskite catalyst comprises 30-65 wt% of active component and 35-70 wt% of carrier alumina;
the active component has a perovskite crystalline structure and a general formula of the active component is AXB1-XCO3In the formula 0<X<1, A and B are two different rare earth elements, and C is a transition metal element.
Preferably, the active component has a general formula of LaXCe1-XCO3In the formula 0<X<0.6, C is Mn, Co or Cu, preferably Mn.
Further, the perovskite-type catalyst is a honeycomb-shaped catalyst prepared by a monolith molding method.
A monolithic molding method of a perovskite type catalyst comprises the following steps:
1) mixing metal salt, an alkaline precipitator, an organic pore-forming agent and water, reacting to obtain a precipitate, and filtering, washing, drying and roasting the precipitate to obtain active component powder;
2) grinding and sieving the active component powder obtained in the step 1) to obtain active component powder, and mixing the active component powder with an acid solution, alumina, sesbania powder and water to obtain a wet mass;
3) carrying out vacuum mixing and extrusion molding on the wet material mass obtained in the step 2) to obtain a honeycomb-shaped wet base blank;
4) drying and calcining the honeycomb-shaped wet base blank body obtained in the step 3) to obtain the perovskite type catalyst.
Further, in the step 1), the mass ratio of the metal salt, the alkaline precipitator, the organic pore-forming agent and the water is 1: 0.2-0.9: 0.01-0.05: 2-8.
Further, in step 1), the metal salt is a soluble salt (preferably nitrate) mixture of the metal A, B and C, and preferably, the metal salt and the organic pore-forming agent are prepared into an aqueous solution with the metal salt concentration of 0.5-2mol/L before reaction.
Further, in the step 1), the alkaline precipitator is a mixture of sodium hydroxide and sodium carbonate, and the mixing molar ratio is 1:5-5:1, preferably 2: 1; preferably, the aqueous solution of the alkaline precipitator is prepared before reaction, and the concentration is 10 to 20 weight percent; the addition mode of the alkaline precipitant is preferably dropwise, and comprises forward dropwise addition, reverse dropwise addition or cocurrent dropwise addition, and the forward dropwise addition is most preferable. The forward dropping is that the alkaline precipitant is dropped into the metal salt, the reverse dropping is that the metal salt is dropped into the alkaline precipitant, and the parallel dropping is that the alkaline precipitant and the metal salt are simultaneously dropped into the reaction system.
Further, in the step 1), the reaction is carried out at the temperature of 50-80 ℃ for 0.5-2 h.
Further, in the step 1), the organic pore-forming agent is alpha cellulose; the particle size of the organic pore-forming agent is 20-100um, preferably 30 um. The organic pore-forming agent is added in the preparation process, so that the internal diffusion resistance of the raw materials and the products can be reduced, the mass transfer effect can be improved, the dispersion degree of the active components can be improved, and the activity of the catalyst can be effectively improved.
Further, in the step 1), all the raw materials are mixed under the condition of high-speed stirring, and the stirring speed is 300-; the precipitate is filtered and washed by adopting a method commonly used in the field, and the washing is washed by deionized water, which are catalyst treatment processes commonly used in the field.
Further, in the step 1), the drying is carried out at the temperature of 90-120 ℃ for 4-8 h; the roasting is carried out at the temperature of 400 ℃ and 600 ℃ for 4-8 h.
Further, in the step 2), the solid raw material comprises active component powder, alumina and sesbania powder, and the components of the solid raw material comprise 30-55 wt% of the active component powder, 35-70 wt% of the alumina and 2-10wt% of the sesbania powder, and the total amount is 100%.
Further, in the step 2), the acid solution is an aqueous nitric acid solution, and the concentration of the aqueous nitric acid solution is preferably 20-40 wt%; the dosage of the acid solution is 40-80wt% of the total mass of the solid raw materials.
Further, in the step 2), the particle size of the active component powder is less than or equal to 100 meshes; the alumina is alpha-alumina trihydrate.
Further, in the step 2), the active component powder, sesbania powder and alumina are preferably dry-mixed, and then an acid solution is added for kneading; the dry mixing is carried out, the rotating speed of a motor is 10-80r/min, and the time is 30-50 min; the kneading is carried out, the rotating speed of a motor is 10-80r/min, and the time is 40-80 min.
Further, in the step 3), the vacuum mixing is carried out in a pug mill, and the vacuum mixing comprises two steps of rough mixing and vacuumizing refining; the rough smelting conditions are as follows: normal pressure, 1-2h time and 10-50mm/s extrusion rate; the vacuumizing refining conditions are as follows: the vacuum degree is 10-25Mpa, the time is 1-3h, and the extrusion speed is 10-50 mm/s. The vacuum mixing can eliminate bubbles in the blank body, so that the catalyst is more compact, and the method is of great importance in the integral forming method, and has important functions of preventing the catalyst from cracking in the drying and roasting processes, enhancing the strength of the catalyst and the like.
Further, in the step 3), the extrusion molding adopts a high-pressure vacuum extrusion mode, and the extrusion conditions are as follows: room temperature, vacuum degree of 10-15KPa, extrusion pressure of 10-30MPa, extrusion rate of 10-50 mm/s; the catalyst can be cylindrical, cuboid or rhombic, the honeycomb pore structure can be round, square or hexagonal, and the shape of the extruded green body can be molded into catalysts with different shapes and pore structures by using different molds according to requirements.
Further, in step 4), the drying is performed by: firstly, drying under constant temperature and humidity in a dark condition, controlling the temperature to be 25-35 ℃, preferably 30 ℃ and keeping the humidity to be 65-85% in the drying process, and quickly drying for 6-12h at 60-80 ℃ when the water content of the honeycomb-shaped wet base blank is reduced to be below 25 wt%. The control of the temperature, the humidity and the drying rate which are suitable in the drying process plays an important role, for example, in the constant-temperature and constant-humidity drying process, the phenomena that the embryo body loses water too fast and the surface and the inside of the embryo body are cracked due to overhigh temperature, overlow humidity or direct strong light.
Further, in the step 4), the calcination is carried out at the temperature of 450-650 ℃ for 4-8 h.
The integrally formed perovskite catalyst can be applied to removal of industrial volatile organic compounds (such as benzene series, alkane, ethyl acetate and the like).
The invention has the beneficial effects that:
the honeycomb perovskite catalyst is prepared by an integral forming method, the defect that an active component is easy to fall off in the industrial application process is overcome, meanwhile, the inactivation caused by the interaction of a carrier and the active component is avoided, and the anti-poisoning performance of the catalyst is obviously improved due to the high content of the active component. The catalyst prepared by the invention has very high activity and stability when being used for removing VOCs pollutants in catalytic combustion, and has high strength and low cost.
Detailed Description
The advantageous effects of the present invention will be described below by way of specific examples. It will be appreciated by those skilled in the art that the examples are only intended to illustrate the invention and are not intended to limit the scope of the invention. In the examples, the means used are conventional in the art unless otherwise specified.
Example 1:
an integral molding method of a perovskite type catalyst comprises the following steps:
1) adding 4.0kg of sodium hydroxide, 2.7kg of sodium carbonate and 40kg of deionized water into a reaction kettle to prepare an aqueous solution of an alkaline precipitator, and dissolving 2.5kg of lanthanum nitrate, 6.0kg of cerium nitrate, 0.2kg of alpha cellulose (with the particle size of 30 mu m) and 7.1kg of a 50 wt% aqueous solution of manganese nitrate into 39.7kg of deionized water to prepare an aqueous solution of metal salts; and (2) dropping the aqueous solution of the alkaline precipitator into the aqueous solution of the metal salts in a forward direction, controlling the temperature in the kettle to be 70 ℃ and the reaction time to be 1.0h in the precipitation process, adjusting the pH of the system to be 10.0 by adopting a mixed aqueous solution of sodium carbonate and sodium hydroxide, continuously aging for 3h at 70 ℃, filtering, washing with water, drying the filter cake at 100 ℃ for 6h, and roasting at 500 ℃ for 6h to obtain the active component powder.
2) Grinding the active component powder obtained in the step 1) and sieving the active component powder with a 100-mesh sieve to obtain active component powder, taking 5kg of the active component powder, 0.5kg of sesbania powder and 5kg of a-type alumina trihydrate, carrying out dry mixing in a mixer, wherein the rotating speed of a motor is 15r/min, the dry mixing time is 30min, then adding a mixed solution of 5kg of deionized water and 2.5kg of nitric acid, and kneading for 1h at the rotating speed of the motor of 30r/min to obtain wet material lumps;
3) putting the wet material mass obtained in the step 2) into a vacuum pug mill for high-pressure mixing at room temperature, firstly carrying out 7.5Mpa and rough mixing for 3h, then carrying out vacuum refining for mixing for 3h under the vacuum degree of 10Mpa, and carrying out extrusion molding on the mixed pug at the extrusion speed of 50mm/s in the mixing process, wherein the mixed pug is put into a high-pressure vacuum extruder for extrusion molding, and the conditions of the high-pressure vacuum extrusion are as follows: room temperature, vacuum degree of 12KPa, extrusion pressure of 20MPa, extrusion speed of 20mm/s, obtaining a honeycomb-shaped wet-based blank body with wall thickness of 1mm, square pore channel and side length of 100mm multiplied by 100 mm;
4) and 3) drying the honeycomb wet-based blank body obtained in the step 3) in a constant temperature and humidity room, controlling the temperature to be 30 +/-5 ℃, keeping the humidity to be 65-75%, keeping out of the sun, quickly drying the wet blank body for 8 hours in a drying furnace at 80 ℃ when the water content of the wet blank body is reduced to 25wt%, and finally roasting the wet blank body for 4 hours in a muffle furnace at 500 ℃ to obtain the perovskite type catalyst.
The perovskite catalyst prepared in example 1 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3。
Example 2
The integral forming process of perovskite catalyst includes the same steps as that in example 1, and the basic technological process is the same with the difference in that the forming mold is square 100mm × 100mm, hexagonal channel structure and 1mm wall thickness.
Example 3:
a process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 1): the prepared aqueous solution of the alkaline precipitant and the aqueous solution of the metal salt are subjected to precipitation reaction in a parallel-flow dropwise manner.
The perovskite catalyst prepared in example 3 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3。
Example 4
An integral forming method of a perovskite catalyst comprises the steps as described in example 1, except that in step 1), 2.7kg of lanthanum nitrate, 6.3kg of cerium nitrate, 0.2kg of alpha cellulose (with the particle size of 30um) and 6.0kg of cobalt nitrate are dissolved in 39.1kg of deionized water to prepare an aqueous solution of metal salts;
the perovskite catalyst prepared in example 4 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7CoO3。
Example 5
A process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 1): raw material ratio was changed by dissolving 1.7kg of lanthanum nitrate, 6.8kg of cerium nitrate, 0.2kg of alpha cellulose (particle size 30um), and 7.0kg of a 50 wt% aqueous solution of manganese nitrate in 39.4kg of deionized water to prepare an aqueous solution of metal salts.
The perovskite catalyst prepared in example 5 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.2Ce0.8MnO3。
Example 6
A process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 1): adding 4.0kg of sodium hydroxide and 2.7kg of sodium carbonate into a reaction kettle, dissolving the sodium hydroxide and the sodium carbonate in 40kg of deionized water to prepare an alkali solution, and dissolving 7.2kg of lanthanum nitrate, 1.8kg of cerium nitrate, 0.2kg of alpha cellulose and 7.4kg of 50 wt% manganese nitrate solution in 39.3kg of deionized water to prepare a metal salt aqueous solution; composition of the catalyst prepared in example 6: 58% of active component and 42% of carrier alumina; wherein the active component is La0.8Ce0.2MnO3。
Comparative example 1
A process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 1): 6.7kg of sodium hydroxide was used as the alkaline precipitant.
The catalyst prepared in the comparative example 1 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3。
Comparative example 2
A process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 2): taking 1kg of catalyst powder, 0.5kg of sesbania powder and 10kg of a-type alumina trihydrate, carrying out dry mixing in a mixer at the motor rotating speed of 6r/min for 30min, adding a mixed solution of 5kg of deionized water and 2.5kg of nitric acid, and kneading for 1 h. The remaining steps are as described in example 1.
The catalyst prepared in the comparative example 2 comprises the following components in percentage by mass: 13% of active component and 87% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3。
Comparative example 3
A process for the monolithic formation of a perovskite catalyst, the steps of which are as described in example 1, except that the calcination in step 1 and the calcination in step 4) are both carried out at a temperature of 300 ℃.
The catalyst prepared in the comparative example 3 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3。
Comparative example 4
A process for the monolithic formation of a perovskite catalyst, the steps of which are as described in example 1, except that the calcination in step 1 and the calcination in step 4) are both carried out at a temperature of 700 ℃.
The catalyst prepared in the comparative example 4 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.0.7MnO3。
Comparative example 5
A process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 4): the precipitation reaction temperature was 25 ℃ and the other steps were the same as in example 1.
The catalyst prepared in the comparative example 5 comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3。
Comparative example 6
A process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 4): the constant temperature and humidity drying is replaced by rapid drying at 120 ℃ for 6h, and the catalyst is cracked after roasting, and the catalyst comprises the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3。
Comparative example 7
A process for the monolithic formation of a perovskite catalyst, the process being as described in example 1, except that in step 3): the prepared wet blank is not mixed and directly extruded and molded, and the prepared catalyst blank contains bubbles which comprise the following components in percentage by mass: 58% of active component and 42% of carrier alumina; wherein the active component is La0.3Ce0.7MnO3. The compressive strength of the catalyst is 1.0MPa in the axial direction and 0.3MPa in the radial direction, and the catalyst is easy to break in the using process; the active component shedding rate test (oscillation power of 200w for 60min) is 0.9%, and the wear rate of the catalyst after 1000h is 2.8%/kg.
Under the same conditions, the catalyst of the embodiment 1 of the invention is tested to have the compressive strength of 2.3MPa in the axial direction and 0.9MPa in the radial direction; the active component falling rate is lower than 0.1%/kg, and the wear rate of the catalyst is lower than 0.1%/kg after the catalyst is used for 1000 hours. The performance of the catalyst of the invention in example 1 is significantly better than that of the comparative example.
The catalysts prepared in the above examples 1-6 and comparative examples 1-7 of the present invention were subjected to catalytic combustion reaction using xylene as a model pollutant to examine the performance of the catalysts, IIThe toluene concentration was 2000mg/m3The space velocity is 20000h-1The results are shown in Table 1.
The activity test method of the catalyst comprises the following steps: the method is carried out on a fixed bed, the catalyst is cut into a cylindrical shape, the catalyst is placed in a constant-temperature area of a reaction tube, an air source is divided into two paths, organic saturated steam is prepared by a bubbling method in one path, the steam quantity of the organic is controlled by flow, then the organic saturated steam is mixed with air in the other path to prepare mixed gas with a certain concentration, then the mixed gas enters the fixed bed reactor to carry out catalytic combustion reaction, the evaluation is carried out by adopting a temperature programming mode, the reaction tail gas is analyzed on line by adopting Agilent 6890N chromatography, and the airspeed of the reaction gas is 20000h-1The reaction temperature is 200-400 ℃.
TABLE 1 evaluation table of xylene catalytic combustion reaction activity
Figure BDA0001697464940000111
As can be seen from Table 1, the molded catalyst has high catalytic activity, the invention adopts the prior equipment technology and reasonable preparation process, can prepare monolithic catalysts with different structures according to requirements, and the catalyst prepared by the invention has high activity, good stability and long service life, can still realize 100 percent complete conversion of dimethylbenzene after continuously running for 1000 hours at 280 ℃, has low price and can be used for replacing noble metal catalysts.
The above examples are only for describing the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and various modifications and improvements made to the technical solution of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims (9)

1. A perovskite catalyst characterized by: the percentage composition is 30-65 wt% of active component and 35-70 wt% of carrier alumina; the active component has a perovskite crystalline structure and a general formula of the active component is AXB1-XCO3In the formula 0<X<0.6, A and B are two different rare earth elements, and C is Mn, Co or Cu;
the catalyst is used for removing benzene series, alkane and ethyl acetate;
the preparation method of the perovskite type catalyst comprises the following steps:
1) mixing metal salt, an alkaline precipitator, an organic pore-forming agent and water, reacting to obtain a precipitate, filtering, washing and drying the precipitate, and roasting at the temperature of 400-;
2) grinding and sieving the active component powder obtained in the step 1) to obtain active component powder, and mixing the active component powder with an acid solution, alumina, sesbania powder and water to obtain a wet mass;
3) carrying out vacuum mixing and extrusion molding on the wet material mass obtained in the step 2) to obtain a honeycomb-shaped wet base blank; the vacuum mixing is carried out in a pug mill, and comprises two steps of rough mixing and vacuumizing refining; the rough smelting conditions are as follows: normal pressure, 1-2h time and 10-50mm/s extrusion rate; the vacuumizing refining conditions are as follows: the vacuum degree is 10-25MPa, the time is 1-3h, and the extrusion rate is 10-50 mm/s;
4) drying and calcining the honeycomb-shaped wet base blank body obtained in the step 3), wherein the drying method comprises the following steps: firstly, drying at constant temperature and humidity under the condition of keeping out of the sun, wherein the temperature is 25-35 ℃, the humidity is 65-85%, and when the water content of the honeycomb-shaped wet base blank body is reduced to 25wt%, quickly drying for 6-12h at 60-80 ℃ to obtain the perovskite catalyst.
2. A method of forming a monolith of the perovskite catalyst of claim 1, comprising the steps of:
1) mixing metal salt, an alkaline precipitator, an organic pore-forming agent and water, reacting to obtain a precipitate, filtering, washing and drying the precipitate, and roasting at the temperature of 400-;
2) grinding and sieving the active component powder obtained in the step 1) to obtain active component powder, and mixing the active component powder with an acid solution, alumina, sesbania powder and water to obtain a wet mass;
3) carrying out vacuum mixing and extrusion molding on the wet material mass obtained in the step 2) to obtain a honeycomb-shaped wet base blank; the vacuum mixing is carried out in a pug mill, and comprises two steps of rough mixing and vacuumizing refining; the rough smelting conditions are as follows: normal pressure, 1-2h time and 10-50mm/s extrusion rate; the vacuumizing refining conditions are as follows: the vacuum degree is 10-25MPa, the time is 1-3h, and the extrusion rate is 10-50 mm/s;
4) drying and calcining the honeycomb-shaped wet base blank body obtained in the step 3), wherein the drying method comprises the following steps: firstly, drying at constant temperature and humidity under the condition of keeping out of the sun, wherein the temperature is 25-35 ℃, the humidity is 65-85%, and when the water content of the honeycomb-shaped wet base blank body is reduced to 25wt%, quickly drying for 6-12h at 60-80 ℃ to obtain the perovskite catalyst.
3. The integrated molding method according to claim 2, wherein: in the step 1), the mass ratio of metal salt, alkaline precipitant, organic pore-forming agent and water is 1: 0.2-0.9: 0.01-0.05: 2-8; the metal salt is a soluble salt mixture of metal A, B and C; the alkaline precipitator is a mixture of sodium hydroxide and sodium carbonate, and the molar ratio is 1:5-5: 1; the particle size of the organic pore-forming agent is 20-100 mu m.
4. The integrated molding method according to claim 3, wherein: the molar ratio of the mixture of sodium hydroxide and sodium carbonate is 2: 1.
5. The integrated molding method according to claim 3, wherein: the organic pore-forming agent is alpha cellulose.
6. The integrated molding method according to claim 2, wherein: in the step 1), the reaction is carried out at the temperature of 50-80 ℃ for 0.5-2 h; drying at 90-120 deg.C for 4-8 hr; and roasting for 4-8 h.
7. The integrated molding method according to claim 2, wherein: in the step 2), the solid raw materials comprise active component powder, alumina and sesbania powder, and the components comprise 30-55 wt% of the active component powder, 35-70 wt% of the alumina and 2-10wt% of the sesbania powder, and the total amount is 100%; the dosage of the acid solution is 40-80wt% of the total mass of the solid raw materials.
8. The integrated molding method according to claim 2, wherein: in the step 2), mixing, dry mixing of active component powder, sesbania powder and alumina is carried out, and then acid solution is added for kneading; the dry mixing is carried out, the rotating speed of a motor is 10-80r/min, and the time is 30-50 min; the kneading is carried out, the rotating speed of a motor is 10-80r/min, and the time is 40-80 min.
9. The integrated molding method according to claim 2, wherein: in the step 4), the calcination is carried out at the temperature of 450-650 ℃ for 4-8 h.
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