Common carrier types and characteristics of honeycomb ozone removal catalysts
The carriers for honeycomb ozone removal catalysts need to meet requirements such as high specific surface area, good air permeability, high mechanical strength, and strong chemical stability, in order to support the active components (such as MnO₂, TiO₂, precious metals, etc.) and ensure efficient ozone decomposition. The following are the common carrier types and their core characteristics:
I. Cordierite (Cordierite) Carrier
Chemical composition: 2MgO·2Al₂O₃·5SiO₂, belonging to hexagonal crystal system silicate minerals.
Structural characteristics:
Porous honeycomb structure, typical pore density of 200-600 cpsi (cpsi = cubic centimeters per square inch), open porosity > 70%, low gas resistance;
Low thermal expansion coefficient (α = 1-3×10⁻⁶/℃), high temperature resistance (long-term use temperature ≤ 800℃), excellent thermal shock resistance.
Performance advantages:
High mechanical strength (compressive strength > 15MPa), wear-resistant, suitable for high gas flow impact scenarios (such as industrial waste gas treatment);
Surface is weakly acidic, can be modified by acid washing or coating (such as loading Al₂O₃) to improve the dispersion of active components.
Application scenarios: Tail gas treatment of large industrial ozone generators, ozone tail gas decomposition in municipal wastewater treatment.
II. Alumina (Alumina, Al₂O₃) Carrier
Chemical composition: γ-Al₂O₃ (commonly used), α-Al₂O₃ (high-temperature stable type).
Structural characteristics:
High specific surface area (γ-Al₂O₃ can reach 150-300 m²/g), rich micropores (pore diameter 2-10nm), high active component loading capacity;
Can be extruded to form honeycomb structure, flexible pore density (100-400 cpsi), surface can be modified with hydroxyl groups (-OH) to enhance catalyst anchoring effect.
Performance advantages:
Good chemical stability, resistant to acid and alkali corrosion (pH 3-11), suitable for complex exhaust gas environments;
Moderate thermal stability (γ-Al₂O₃ usage temperature ≤ 500℃, α-Al₂O₃ can reach above 1000℃).
Application scenarios: Household ozone purifiers, ozone removal modules for automotive air conditioning (small-sized equipment).
III. Titanium Dioxide (Titania, TiO₂) Carrier
Chemical composition: Anatase or Rutile phase of TiO₂.
Structural characteristics:
Higher specific surface area of anatase (50-100 m²/g), rich Lewis acid sites on the surface, can generate synergistic catalysis with ozone (photo catalysis + chemical catalysis);
Resistant to light corrosion, suitable for scenarios of ultraviolet light-assisted ozone decomposition (such as photocatalytic reactors).
Performance advantages:
It has certain ozone decomposition activity by itself (especially under ultraviolet light excitation), can reduce the amount of active components;
Will transform to rutile phase at high temperatures (>600℃), decreased specific surface area, need to control the usage temperature.
Application scenarios: Photocatalytic ozone purification equipment, hospital operating room air disinfection system (requires coordination with ultraviolet lamps).
IV. Activated Carbon (Activated Carbon, AC) Carrier
Chemical composition: Mainly carbon, containing a small amount of oxygen and hydrogen functional groups (such as -COOH, -OH).
Structural characteristics:
High specific surface area (500-1500 m²/g), multi-level pore structure of micro, meso, and macropores, large adsorption capacity;
Activated carbon is formed by binder molding, mechanical strength is low (needs to add resin to enhance), prone to adsorb moisture and organic impurities causing blockage.
Performance advantages:
Has both physical adsorption and chemical catalysis functions, can adsorb ozone first and then decompose through loaded metal oxides (such as MnO₂);
Low cost, suitable for low-concentration ozone (<100 ppm) treatment scenarios.
Application scenarios: Filter net for household air purifiers, ozone residue removal in food packaging workshops. The regular microporous structure (pore size 0.3 - 1.5 nm) has strong selectivity and can inhibit side reactions (such as excessive decomposition of ozone generating ·OH free radicals);
The surface can undergo ion exchange (such as introducing Cu²⁺ and Ag⁺), enhancing the adsorption and activation ability of ozone.
Performance advantages:
Excellent hydrothermal stability (use temperature ≤ 600℃), suitable for high humidity environments (such as ozone-bleaching tail gas from paper mills);
Strong resistance to poisoning, higher tolerance to impurities such as SO₂ and NOx than activated carbon.
Application scenarios: Industrial high-humidity waste gas ozone treatment, ozone odor removal in cigarette factories (requires resistance to water vapor).
Six. Composite Carriers
Common combinations: Al₂O₃-TiO₂ composite carrier, spinel-Al₂O₃ coated carrier.
Performance advantages:
Collaborate the advantages of a single carrier, such as "spinel + Al₂O₃ coating": Spinel ensures mechanical strength and permeability, Al₂O₃ coating enhances specific surface area and dispersion of active components;
The performance can be optimized by adjusting the composite ratio (for example, when the TiO₂ proportion in the Al₂O₃-TiO₂ composite carrier is 20%-30%, the ozone decomposition efficiency increases by 15%-20%).
Application scenarios: High-end ozone catalytic equipment (such as ultra-clean workshops in semiconductor factories).
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