CN102794169B - Attapulgite-perovskite composite material, preparation method and application thereof - Google Patents

Abstract

The invention discloses an attapulgite-perovskite composite material and its preparation method and application, wherein the attapulgite-perovskite composite material uses attapulgite clay as a carrier, and the attapulgite surface is loaded with perovskite In the composite material obtained after granulation, the loading of perovskite is 6-12% of the mass of attapulgite clay; the composition of the composite material of the present invention is expressed as: μ% La _1-x Sr _x MnO ₃ /PG; where μ =6-12, x=0, 0.1 or 0.3. The composite material of the invention has a nano structure, has low activation energy, high catalytic activity and strong deactivation resistance, and can be applied to the purification of volatile organic pollutants such as toluene and the catalytic oxidation of other various organic substances.

Description

A kind of attapulgite-perovskite composite material and its preparation method and application

1. Technical field

The invention belongs to the field of energy and chemical industry, and relates to a nano material with attapulgite clay as a carrier and perovskite compound nano particles as an active component, a preparation method and an application for removing volatile organic pollutants.

2. Background technology

Volatile organic compounds (VOCs) usually refer to organic compounds with a boiling point of 50-260°C under normal pressure, such as alkanes, alkenes, aromatic hydrocarbons, chlorinated aromatic hydrocarbons, saturated and unsaturated aldehydes, ketones, etc. VOCs mainly come from exhaust gases emitted by industries such as petroleum, chemical industry, papermaking, paint coatings, mining, metal electroplating, and textiles, as well as exhaust gases emitted by many vehicles.

According to statistics, from 2005 to 2010, the total emission of VOCs in my country was about 26.5-31 million tons. In 2010, only about 3.88 million tons of VOCs were released into the atmosphere during the coating application process in my country, accounting for a large proportion of the total emissions of volatile organic waste gases. . Five types of compounds, such as benzene series, alcohol, vinegar, ether, and ketone, are the main components of organic waste gas emitted by current coating applications, accounting for 29%, 19%, 13%, 10%, and 11% of the total, of which 31% It is a toxic and harmful substance, mainly toluene and xylene. With the development of society and the improvement of people's requirements for environmental quality, countries around the world have formulated strict environmental protection regulations on the discharge of organic waste gas, such as the United States, Japan, Germany, etc., have formulated strict organic waste gas emission standards, especially for benzene series , polycyclic aromatic hydrocarbons, polychlorinated biphenyls, dioxins and other common and highly toxic industrial organic waste gases have attracted the attention of people and environmental protection workers. Among the 189 priority toxic air pollutants that are required to be monitored by the United States Clean Air Amendment (1990), about 100 are volatile organic pollutants; the "Comprehensive Emission Standards for Atmospheric Pollutants" promulgated and implemented in my country in 1997 The emission limits of 33 kinds of pollutants are limited, including various VOCs such as benzene series (benzene, toluene and xylene). At present, the control and treatment of air pollution in my country are mostly focused on the technical research and industrial promotion of flue gas dust removal, desulfurization, and denitrification of large-scale fixed sources such as power plants and boilers. In contrast, volatile organic waste gases, such as benzene series organic waste gases emissions have not attracted enough attention. Therefore, the development of economical and efficient organic waste gas treatment technology will have important environmental, economic and social significance for improving my country's air quality and realizing the control and governance of air pollution.

3. Contents of the invention

The present invention aims to provide an attapulgite-perovskite composite material and its preparation method and application. The technical problem to be solved is to select suitable raw materials and proportions so that they can remove volatile organic waste gas through catalytic oxidation.

The present invention solves technical problem and adopts following technical scheme:

The attapulgite-perovskite composite material of the present invention is a composite material obtained by loading perovskite particles on the attapulgite surface with attapulgite clay as a carrier. 6-12%;

The general composition formula of the composite material of the present invention is expressed as: μ%La _1-x Sr _x MnO ₃ /PG;

Among them, La _1-x Sr _x MnO ₃ is perovskite, PG is attapulgite carrier, μ% indicates the loading amount of perovskite (accounting for the mass percentage of PG), μ=6-12;

The perovskite is lanthanum-manganese perovskite, ie x=0, the molar ratio of lanthanum to manganese is 1:1, or lanthanum-manganese perovskite doped with strontium, x=0.1 or 0.3.

The diameter of the attapulgite crystal in the attapulgite clay is 40-50nm;

The particle size of the perovskite is less than 10nm.

In the attapulgite clay, the mass percentage of attapulgite is ≥60%, and the mass percentage of dolomite is ≤10%.

The preparation method of attapulgite-perovskite composite material of the present invention, operates according to the following steps:

a. Pre-stock and homogenize the attapulgite clay;

b. Add water to the attapulgite clay after stockpiling and homogenization, so that the water content of the attapulgite clay is 30-50%, mix evenly, and then shear and extrude the attapulgite through a pair of rollers or a multi-roller extruder to obtain attapulgite Stone clay flakes, which depolymerize and disperse attapulgite crystal bundles;

c, drying the attapulgite clay flakes and pulverizing them through a 200-mesh sieve to obtain attapulgite powder;

d. Add 50 g of the attapulgite powder into 200-2000 mL of water, age for 10-48 hours and then stir for 0.5-1 hour to obtain a uniformly mixed slurry, and add a proportioned amount of easily soluble Lanthanum salt and soluble manganese salt or soluble lanthanum salt, soluble strontium salt and soluble manganese salt are added in a proportioning amount, stirred until no bubbles are generated, then ammonia water is added to adjust the pH value to 8-10 to obtain a suspension, and the added Complete hydrolysis of lanthanum ions and/or strontium ions and/or manganese ions;

The proportioning amount refers to the amount calculated according to the composition and proportioning of the general formula;

e. The suspension is washed and dehydrated to obtain a mud cake, and the mud cake is dried and sieved into 40-60 mesh pellets, or paste starch is added to the mud cake to dry and granulate to obtain a 40-60 mesh Granules; the addition of pasty starch is 1-5% of the mud cake quality;

f. Calcining the pellets at 600-900°C for 1.5-2.5 hours to convert the colloidal particles of lanthanum, strontium and manganese hydroxides loaded on the surface of attapulgite into nano-oxide particles to obtain attapulgite clay-calcium Titanium composite.

The soluble lanthanum salt is nitrate or sulfate of lanthanum; the soluble strontium salt is nitrate or sulfate of strontium; the soluble manganese salt is nitrate or sulfate of manganese.

The application of the attapulgite clay-perovskite composite material of the invention as a catalyst in the process of catalytic oxidation of volatile organic compounds.

The perovskite in the attapulgite-perovskite composite material referred to in the present invention refers to a perovskite compound.

The present invention takes toluene as an example to detect the catalytic oxidation performance of the attapulgite clay-perovskite composite material, and the process is as follows:

0.5g of the composite material prepared by the present invention is packed into the quartz tube of the gas-solid phase catalytic reactor, the reactor starts to heat up from room temperature, and the air generated by the air pump is divided into two paths, one path is passed into toluene, and the other path is used as a dilution gas, After being mixed through the gas mixing bottle, it enters the catalytic oxidation reaction system, and different concentrations of toluene gas can be obtained by adjusting the flow of the two-way gas. The gas concentration of toluene or other VOCs at the inlet and outlet of the catalytic oxidation reaction system is detected by gas chromatography equipped with an FID detector, and the activity of the catalyst is expressed by the conversion rate of toluene or other VOCs.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1, in the attapulgite clay, the attapulgite crystals often become bundle-like aggregates, and the shearing and extrusion of the attapulgite clay can promote the depolymerization of the bundle-like aggregates and impel the attapulgite nanocrystals to disperse. The method of the present invention adopts The extrusion shear pretreatment improves the specific surface area and catalytic performance of the composite.

2. Attapulgite clay generally contains a certain amount of dolomite, and the added lanthanum, strontium, and manganese salt solutions are acidic. The present invention utilizes the characteristic of attapulgite clay mineral composition, directly mixes attapulgite clay powder with lanthanum, strontium and manganese salt solution, which not only neutralizes the acidity of lanthanum, strontium and manganese salt solution, but also removes the unevenness The dolomite impurity of the rod stone clay improves the performance of the material, reduces the consumption of neutralizing and precipitating agent ammonia water, reduces the pollution discharge of acid waste water and high salinity waste liquid, and reduces the cost of catalyst material preparation.

3. The inventor found through research that there is an interaction between attapulgite and metal ions. The present invention utilizes this interaction to bring into play the hydrolysis and precipitation of metal ions induced by attapulgite crystals, and the attapulgite colloidal particles (negatively charged) and The interaction of metal ions to hydrolyze the hydroxide (positively charged) enables the metal hydroxide to be uniformly dispersed on the surface of the attapulgite crystal in the form of colloidal particles, and the pre-assembly of attapulgite and metal nanocomposite preparation is realized.

4. In the present invention, through calcination at an appropriate temperature, the lanthanum, strontium, and manganese hydroxides uniformly dispersed on the surface of the attapulgite crystal form perovskite compound nanoparticles to obtain attapulgite-perovskite composite materials, The catalytic activity of the composite material is improved.

5. The present invention simultaneously loads perovskite compound particles smaller than 10nm in diameter on the surface of attapulgite rod-shaped crystals. It is found that nano-scale perovskite compound particles can be uniformly dispersed on the surface of attapulgite carrier, which improves the catalytic performance. activity, reducing the loading of perovskite.

6. In the present invention, an organic binder is added to the mud cake produced after dehydration, stirred and mixed evenly, and granulated, which can improve the granulation effect and increase the porosity of the catalyst particles.

4. Description of drawings

Fig. 1 is the TEM image of the attapulgite-lanthanum manganese perovskite nanocomposite material prepared in the present invention.

Fig. 2 is a TEM image of the attapulgite clay-lanthanum strontium manganese perovskite nanocomposite material with a lanthanum strontium molar ratio of 9:1 prepared by the present invention.

Fig. 3 is a TEM image of the attapulgite clay-lanthanum strontium manganese perovskite nanocomposite material with a lanthanum strontium molar ratio of 7:3 prepared by the present invention.

5. Specific implementation

Example 1:

1. Pour the attapulgite clay ore mined from the mine on the ground of the ore stockyard, pave the thickness not to exceed 10cm, and transport it to the conical ore pile after drying for 3-5 days. The average ore stockpiling time is 1-6 During the storage process, the ore experienced natural weathering, natural crushing and mixing and homogenization to improve the uniformity of ore raw materials. Raw materials are taken from ore piles in a vertical way.

2. Add water to the attapulgite clay material taken out from the ore pile, so that the water content of the attapulgite clay is 30-50%. After mixing evenly, the attapulgite is obtained by shearing and extruding with a pair of rollers or a multi-roller extruder. Clay flakes promote the depolymerization and dispersion of attapulgite crystal bundles.

3. Attapulgite clay flakes were dried at 105° C., crushed and passed through a 200-mesh sieve to obtain attapulgite clay powder.

4. Add 50g of attapulgite powder into 1000ml of water, age for 24 hours, then use a high-speed mixer to stir at a high speed of 10000r/min for 0.5 hours to obtain a uniformly mixed slurry, and add 5.37g of lanthanum nitrate (La( NO ₃ ) ₃ 6H ₂ O analytically pure), stirred for 30 minutes, then added 4.44g manganese nitrate (50% analytically pure containing Mn(NO ₃ ) ₂ ), continued stirring until no bubbles were produced, then added dropwise ammonia solution , 10000r/min high-speed stirring for 10min, adjust the pH value to 8-10 to obtain a suspension, so that the added lanthanum ions and manganese ions are hydrolyzed completely.

5. Filter the suspension with a plate and frame filter press with washing function, wash and dehydrate to obtain a mud cake, and use an extrusion molding machine to shape the mud cake into 0.5-2mm pellets and dry.

6. Place the pellets in a muffle furnace for calcination at 700°C for 2 hours, so that the colloidal particles of lanthanum and manganese hydroxides loaded on the surface of the attapulgite interact and transform into nano-scale perovskite with high catalytic activity at high temperature. compound particles to obtain attapulgite-perovskite composite material, and the mass percentage of lanthanum manganese perovskite in the composite material is 6% (6%LaMnO ₃ /PG).

The transmission electron microscope image of the attapulgite-lanthanum manganese perovskite composite material prepared in this example is shown in FIG. 1 . It can be seen from Figure 1 that the lanthanum-manganese perovskite particles are loaded on the surface of the attapulgite rod-shaped crystals, the particle size of the nanoparticles is 5-10nm, and the lanthanum-manganese perovskite as a catalytic oxidation active component has a high dispersion Spend.

The composite material prepared in this example is loaded into a gas-solid phase catalytic reactor, and toluene is used as a model compound to evaluate the efficiency of catalytic oxidation of VOCs. The results show that for toluene gas with a concentration of 3790 mg/ ^m3 , the conversion of toluene at 339 ° C The rate is 99%, and the catalytic oxidation effect is higher than the performance of the currently reported catalysts.

Example 2:

The preparation method of step 1-3 is the same as embodiment 1.

4. Add 50g of attapulgite powder into 1000ml of water, age for 24 hours, and then use a high-speed mixer to stir at a high speed of 10000r/min for 0.5 hours to obtain a uniformly mixed slurry, and add 7.00g of lanthanum nitrate (La( NO ₃ ) ₃ 6H ₂ O analytically pure), stirred for 10 minutes, then added 0.38g strontium nitrate (Sr(NO ₃ ) ₂ analytically pure), continued stirring for 20 minutes, then added 6.43g manganese nitrate (containing Mn(NO ₃ ) ₂ is 50% analytically pure), continue to stir until no bubbles are produced, then add dropwise ammonia solution, stir at a high speed of 10000r/min for 10min, adjust the pH value to 8-10 to obtain a suspension, and make the added lanthanum ion, strontium ion and manganese Ionic hydrolysis is complete.

5. Filter the suspension with a plate and frame filter press with washing function, wash and dehydrate to obtain a mud cake, dry the mud cake, crush and sieve to obtain 0.5-2mm granules.

6. Place the pellets in a muffle furnace for calcination at 700°C for 2 hours, so that the colloidal particles of lanthanum, strontium, and manganese hydroxides loaded on the surface of attapulgite interact at high temperature and transform them into nano-scale perovskite with high catalytic activity ore-type compound particles to obtain attapulgite-perovskite composite materials, and the mass percentage of lanthanum strontium manganese perovskite in the composite material is 8.5% (8.5%La _0.9 Sr _0.1 MnO ₃ /PG).

The transmission electron microscope image of the attapulgite-lanthanum strontium manganese perovskite composite material prepared in this example is shown in Figure 2. The lanthanum strontium manganese perovskite particles are loaded on the surface of the attapulgite rod-shaped crystals, and the particle size of the nano-metal particles is 5-10nm, the lanthanum strontium manganese perovskite as the catalytic active component has a high degree of dispersion.

The composite material prepared in this example was loaded into a gas-solid phase catalytic reactor, and toluene was used as a simulated compound to evaluate the efficiency of catalytic oxidation of VOCs. The results showed that for toluene gas with a concentration of 3790 mg/ ^m3 , the conversion of toluene at 318 ° C The rate is 99%, and the catalytic oxidation effect is higher than the performance of the currently reported catalysts.

Example 3:

The preparation method of step 1-3 is the same as embodiment 1.

4. Add 50g of attapulgite powder into 1000ml of water, age for 24 hours, then use a high-speed mixer to stir at a high speed of 10000r/min for 0.5 hours to obtain a uniformly mixed slurry, and add 8.03g of lanthanum nitrate (La( NO ₃ ) ₃ 6H ₂ O analytically pure), stirred for 10 minutes, then added 1.68g strontium nitrate (Sr(NO ₃ ) ₂ analytically pure), continued stirring for 20 minutes, then added 9.48g manganese nitrate (containing Mn(NO ₃ ) ₂ is 50% analytically pure), continue to stir until no bubbles are produced, then add dropwise ammonia solution, stir at a high speed of 10000r/min for 10min, adjust the pH value to 8-10 to obtain a suspension, and make the added lanthanum ion, strontium ion and manganese Ionic hydrolysis is complete.

5. Filter the suspension with a plate and frame filter press with washing function, wash and dehydrate to obtain mud cake, dry the mud cake, crush and sieve to obtain different particles of 0.1-0.2mm, 0.2-0.5mm and 0.5-1.0mm The diameter of the pellets to meet the requirements of the catalytic reactor for fine particle catalysts.

6. Place the pellets in a muffle furnace for calcination at 800°C for 2 hours, so that the colloidal particles of lanthanum, strontium, and manganese hydroxides loaded on the surface of attapulgite interact and transform into nano-scale perovskite with high catalytic activity at high temperature ore-type compound particles to obtain attapulgite-perovskite composite material, the mass percentage of lanthanum strontium manganese perovskite in the composite material is 12% (12%La _0.7 Sr _0.3 MnO ₃ /PG).

The transmission electron microscope image of the attapulgite-lanthanum strontium manganese perovskite composite material prepared in this example is shown in Figure 3. The lanthanum strontium manganese perovskite particles are loaded on the surface of the attapulgite rod-shaped crystals, and the particle size of the nano-metal particles is 5 -10nm, the lanthanum strontium manganese perovskite as the catalytic active component has a high degree of dispersion.

The composite material prepared in this example is loaded into a gas-solid phase catalytic reactor, and toluene is used as a simulated compound to evaluate the efficiency of catalytic oxidation of VOCs. The results show that for a concentration of 3790 mg/m Toluene gas, the catalysts of ^three particle sizes are in The conversion rate of toluene at 300 °C is 99%, and the catalytic oxidation effect is higher than the catalyst performance reported so far.

Example 4:

The preparation method of step 1-3 is the same as embodiment 1.

4. Add 50g of attapulgite powder into 1000ml of water, age for 24 hours, then use a high-speed mixer to stir at a high speed of 10000r/min for 0.5 hours to obtain a uniformly mixed slurry, and add 8.03g of lanthanum nitrate (La( NO ₃ ) ₃ 6H ₂ O analytically pure), stirred for 10 minutes, then added 1.68g strontium nitrate (Sr(NO ₃ ) ₂ analytically pure), continued stirring for 20 minutes, then added 9.48g manganese nitrate (containing Mn(NO ₃ ) ₂ is 50% analytically pure), continue to stir until no bubbles are produced, then add dropwise ammonia solution, stir at a high speed of 10000r/min for 10min, adjust the pH value to 8-10 to obtain a suspension, and make the added lanthanum ion, strontium ion and manganese Ionic hydrolysis is complete.

5. Filter the suspension with a plate and frame filter press with washing function, wash and dehydrate to obtain a mud cake, add paste starch with a mass of 1-5% of the mud cake to the mud cake, and granulate to obtain a 0.5-1.0mm, Granules with different particle sizes of 1.0-2.0mm and 2-3mm meet the requirements of catalytic reactors for fine particle catalysts. Paste starch acts as a binder and porogen.

6. Place the pellets in a muffle furnace for calcination at 800°C for 2 hours, so that the colloidal particles of lanthanum, strontium, and manganese hydroxides loaded on the surface of attapulgite interact and transform into nano-scale perovskite with high catalytic activity at high temperature ore-type compound particles to obtain attapulgite-perovskite composite material, the mass percentage of lanthanum strontium manganese perovskite in the composite material is 12% (12%La _0.7 Sr _0.3 MnO ₃ /PG).

The composite material prepared in this example is loaded into a gas-solid phase catalytic reactor, and toluene is used as a simulated compound to evaluate the efficiency of catalytic oxidation of VOCs. The results show that for a concentration of 3790 mg/m Toluene gas, the catalysts of ^three particle sizes are in The conversion rate of toluene at 300 °C is 99%, and the catalytic oxidation effect is higher than the catalyst performance reported so far.

Claims (6)

1. attapulgite-perovskite composite, is characterized in that: take Concave-convex clay rod as carrier, and the composite obtaining after attapulgite area load perovskite particle, the load capacity of perovskite is the 6-12% of Concave-convex clay rod quality;

The composition of described composite is expressed as: μ%La _1-xsr _xmnO ₃/ PG;

In formula μ=6-12, x=0,0.1 or 0.3.

2. composite according to claim 1, is characterized in that:

In described Concave-convex clay rod, the diameter of attapulgite crystal is 40-50nm;

The particle diameter of described perovskite is less than 10nm.

3. composite according to claim 1 and 2, is characterized in that:

In described Concave-convex clay rod, quality percentage composition >=60% of attapulgite, quality percentage composition≤10% of dolomite.

4. a preparation method for attapulgite-perovskite composite claimed in claim 1, is characterized in that operating according to the following steps:

A, by Concave-convex clay rod store up in advance, homogenizing;

In b, the Concave-convex clay rod to storing up, after homogenizing, add water, making the water content of Concave-convex clay rod is 30-50%, after mixing, through pair roller or Multi-roller extruding machine shear extrusion, obtains Concave-convex clay rod tablet;

C, by described Concave-convex clay rod tablet crushed after being dried and cross 200 mesh sieves obtain attapulgite powder;

D, attapulgite powder described in 50g is added in 200-2000mL water, after ageing 10-48 hour, stir the slurry that obtains mixing for 0.5-1 hour, in described slurry, add easy to be molten lanthanum salt and the Yi Rong manganese salt of proportional quantity or add easy the to be molten lanthanum salt of proportional quantity, easy molten strontium salt and Yi Rong manganese salt, be stirred to without Bubble formation, then add ammoniacal liquor adjust pH 8-10 to obtain suspension;

E, described suspension obtain mud cake through washing, dehydration, described mud cake be dried and are sieved into 40-60 object pellet or pasty state starch is dry also obtains 40-60 object pellet after granulation to adding in described mud cake;

F, by described pellet in 600-900 ℃ calcining 1.5-2.5 hour, obtain Concave-convex clay rod-perovskite composite.

5. preparation method according to claim 4, is characterized in that: nitrate or sulfate that described easy molten lanthanum salt is lanthanum; Nitrate or sulfate that described easy molten strontium salt is strontium; Nitrate or sulfate that described easy molten manganese salt is manganese.

6. a purposes for Concave-convex clay rod-perovskite composite claimed in claim 1, is characterized in that: in the process of volatile organic matter catalytic oxidation as the application of catalyst.

Images