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Selecting an ozone removal catalyst in electronic manufacturing environments is not a matter of simply pursuing the “highest initial efficiency” or the “lowest unit price.” Rather, it is a systematic engineering trade‑off that must comprehensively weigh operating conditions (temperature, humidity, coexisting substances), intrinsic active‑phase performance, support engineering suitability, physical form and system integration, and full‑lifecycle economics. Based on tracking data from multiple industrial applications and the principles of catalytic science, the conclusion is clear: For the vast majority of electronic manufacturing ozone abatement scenarios, manganese‑based composite oxide catalysts (particularly the copper‑manganese composite system) supported on porous silica‑alumina, applied in honeycomb or granular form, achieve over 95% initial ozone decomposition efficiency at ambient temperature and maintain stable performance over a design life of 2–3 years. However, in specialized sub‑scenarios such as advanced semiconductor cleanrooms, high‑humidity factories (relative humidity >80%) in southern regions, and coating processes that emit siloxanes or halogenated compounds, the selector must make precise, differentiated choices across active phase type, support structure and purity, physical form, and poison‑ and moisture‑resistance design—a misstep in any single dimension can lead to rapid deactivation within months or introduce secondary contamination to the production environment.
The following sections systematically examine the scientific principles, quantitative metrics, and engineering trade‑offs of each selection factor, starting from the unique constraints of electronics manufacturing.
Ozone emissions in electronics manufacturing originate primarily from two core processes. The first is ozonated water cleaning: in semiconductor and photovoltaic wafer cleaning, high‑concentration ozone (up to 100 mg/L or more) is introduced into deionized water to form ozone‑ultrapure water for removing photoresist residues and organic contaminants. Dissolved ozone continuously escapes into the workshop air during circulation and drainage. The second is UV‑ozone cleaning (UV‑Ozone): 185 nm ultraviolet light photolyzes oxygen in air to generate ozone, while 254 nm UV further decomposes ozone into reactive oxygen atoms for oxidative removal of organic contaminants. Additionally, corona discharge equipment, plasma treatment tools, and the exhaust treatment units of ozone sterilization systems are also common sources of ozone emissions.
The electronics manufacturing environment imposes special constraints on catalyst selection that differ from those in chemical or municipal applications:
First, cleanliness requirements are extremely high. Semiconductor cleanrooms typically require compliance with ISO Class 3 or even tighter particle control standards. Dust release and ionic leaching from the catalyst and its support can cause irreversible contamination of precision electronic devices. High‑efficiency particulate air (HEPA) filters are usually installed downstream of the catalyst bed as a safety redundancy.
Second, temperature and humidity conditions are tightly controlled but subject to regional and seasonal variations. Cleanrooms are generally maintained at 22‑25°C and 40‑50% relative humidity, but during the rainy season in southern factories or in specific wet process sections, relative humidity may exceed 80%. Water vapor, as a competitive adsorbate for ozone decomposition, reversibly occupies active sites on the catalyst.
Third, the coexistence of multiple gas species is common. Volatile organic compounds (VOCs) such as isopropanol, acid gases (e.g., HF, HCl), or siloxanes (e.g., hexamethyldisiloxane, HMDSO) released during processing can cause irreversible deactivation through chemical poisoning.
The active phase is the “genetic code” of catalyst performance, dictating intrinsic activity and selectivity in the catalytic reaction. In the field of ozone decomposition, transition metal oxides occupy a central position due to the unique electronic structure of their d orbitals.
Core advantages of manganese oxides. Manganese oxides (MnOₓ) are recognized as one of the best active components for ozone decomposition. Their superiority stems from two inherent characteristics: the variable valence states of manganese (Mn²⁺↔Mn³⁺↔Mn⁴⁺), which provide the electron‑transfer basis for catalytic ozone conversion to oxygen, and abundant surface oxygen vacancies—these vacancies serve as preferential adsorption sites for ozone molecules, and their concentration is positively correlated with catalytic activity. Studies have identified three major limiting factors for ambient‑temperature catalytic ozone decomposition: insufficient active sites, competitive adsorption between water molecules and ozone, and difficult desorption of intermediate oxygen species.
Crystal phase engineering of manganese dioxide. Manganese dioxide exists in multiple crystal phases (α, β, γ, δ, ε, etc.), each with distinct tunnel structures. A study published in Environmental Science: Nano systematically compared the ozone decomposition activity of α‑, β‑, γ‑, δ‑, ε‑, and λ‑MnO₂ in dry air at 25°C, yielding the order: ε‑MnO₂ > α‑MnO₂ > γ‑MnO₂ > β‑MnO₂ ≈ δ‑MnO₂ > λ‑MnO₂. The study confirmed that the (102) facet of ε‑MnO₂ possesses the highest density of oxygen vacancies and the best oxygen mobility, with the lowest energy barrier (2.04 eV) for the rate‑determining O₂²⁻ desorption step. However, single MnO₂ readily deactivates under high‑humidity conditions due to competitive water adsorption, limiting its applicability in certain electronics manufacturing scenarios.
Composite approaches: breaking the performance ceiling of single materials. To overcome the shortcomings of single manganese‑based catalysts, copper‑manganese composite oxides have become the mainstream choice in industrial applications. Copper introduction generates a significant synergistic effect: the Cu⁺/Cu²⁺ redox pair and the Mn³⁺/Mn⁴⁺ pair together create a more efficient electron‑transfer channel, accelerating O‑O bond cleavage. In intermittent operation, the copper‑manganese composite is more resistant to thermal shock than single manganese‑based materials—comparative data from a chemical plant showed that the single‑manganese catalyst had to be replaced after each shutdown‑restart cycle, while the composite lasted over 3 years under the same conditions.
For complex exhaust streams containing chlorine or sulfur compounds, manganese‑iron or manganese‑cerium composite systems exhibit superior poison resistance. Cerium doping can modify the crystal structure of OMS‑2 type manganese oxide octahedral molecular sieves, increasing specific surface area and enhancing oxygen vacancy concentration.
If the active phase is the “heart” of the catalyst, the support is the “skeleton” that maintains its long‑term stable operation. Support selection directly affects active component dispersion, mechanical strength, mass‑transfer resistance, and poison tolerance.
Core functions of the support. A high‑specific‑surface‑area support prevents agglomeration of active nanoparticles, exposing more active sites; appropriate pore structure (mesopores of 2‑50 nm) facilitates rapid diffusion of ozone molecules and avoids internal diffusion limitations; sufficient mechanical strength ensures that the catalyst does not pulverize under gas flow impact.
Comparison of support materials. Conventional γ‑alumina is low‑cost and has a high specific surface area (150‑300 m²/g), but its hydrothermal aging resistance is mediocre—in humid environments, it readily undergoes hydration‑induced phase transformation (γ→α), leading to surface‑area collapse. Porous silica‑alumina supports incorporate SiO₂ to suppress rehydration of surface hydroxyl groups, significantly enhancing moisture resistance and poison tolerance. Measured data show that a catalyst on alumina support deactivated within 3 months in humid exhaust, while the silica‑alumina‑supported counterpart maintained activity for more than 2 years under identical conditions.
Engineering advantages of honeycomb structures. For high‑airflow electronics manufacturing exhaust systems, honeycomb ceramic supports (such as cordierite or silicon carbide) combined with washcoat catalysts are the preferred option. Their thin walls and high open frontal area (>70%) provide very low bed pressure drop (typically ≤800 Pa) while allowing high linear velocities. Honeycomb catalysts offer low pressure drop and energy savings; granular forms have slightly higher pressure drop but better resistance to fouling, making them suitable for dust‑ or oil‑mist‑containing exhaust streams.
The physical form of the catalyst determines its compatibility with the reactor configuration and is the most direct factor affecting engineering implementation.
Application boundaries of three main forms. Powder offers the highest specific surface area and intrinsic activity, suitable for laboratory evaluation or specific fluidized‑bed reactors, but its use is strictly limited in electronics cleanrooms due to dust risks. Granules (typically 3‑5 mm diameter) provide controllable pressure drop—measured values are usually below 500 Pa—and can balance efficiency by adjusting bed depth, making them suitable for low‑to‑medium airflow and intermittent operation. Honeycomb has the lowest pressure drop (≤800 Pa) and excellent thermal shock resistance, ideal for high‑airflow continuous operation, but the active component loading is limited and the coating process requires high precision.
Balancing bulk density and bed design. The bulk density of the catalyst must match the design space velocity. Too low a density can cause fluidization and attrition, generating fine dust; too high a density increases flow resistance and raises blower energy consumption. Space velocity (h⁻¹) represents the volume of gas processed per unit volume of catalyst per hour—higher space velocity means greater processing capacity, but excessively high velocity reduces contact time and lowers decomposition efficiency. For high‑flow scenarios (such as workshop exhaust), a high‑space‑velocity catalyst (≥15,000 h⁻¹) is recommended to minimize equipment footprint and reduce fan energy use.
Understanding how a catalyst loses activity is the prerequisite for extending its service life. In electronics manufacturing environments, the main causes of catalyst failure can be categorized into four types.
Moisture poisoning (reversible). Water molecules compete with ozone for adsorption on manganese active sites—this is one of the most challenging limiting factors for ambient‑temperature catalytic ozone decomposition. Above 60% relative humidity, the efficiency of ordinary catalysts drops rapidly. Countermeasures include: enhancing moisture resistance through hydrophobic modification or rare‑earth doping; constructing hydrophobic carbon coatings to inhibit water adsorption; or designing special catalyst structures (such as layered double hydroxides, LDHs) that allow water molecules to participate in ozone decomposition—for example, NiFe hydrotalcite maintained >95% ozone conversion for 22 consecutive days at 65% RH and a high space velocity of 600,000 h⁻¹.
Chemical poisoning (irreversible/hard‑to‑reverse). Organosilicon compounds, sulfides, phosphides, and similar substances in the exhaust react with active components to form stable compounds that block active sites. Siloxane‑containing exhaust (from coating, printing, or electronics processes) requires poison‑resistant formulations. Mitigation includes installing a chemical filtration stage upstream to selectively remove poisons, or choosing active‑phase systems such as manganese‑iron composites with superior poison tolerance.
Accumulation of surface oxygen species (reversible). Studies have shown that the accumulation of surface‑adsorbed oxygen species significantly reduces the catalytic activity of manganese‑based catalysts—this accumulation is closely related to the rate‑limiting step of the decomposition mechanism (i.e., oxygen‑species desorption). Countermeasures include optimizing crystal structure (such as the low‑energy‑barrier desorption characteristics of ε‑MnO₂) to accelerate desorption of intermediate oxygen species.
Carbon deposition and dust coverage (reversible). Polymeric carbonaceous deposits from VOCs and accumulated suspended particles from the atmosphere can block pore mouths and shield active centers. In adsorption‑catalysis coupled processes, catalyst service life typically reaches 2‑3 years.
Deactivation does not mean scrapping. Proper regeneration schemes can significantly prolong the effective service life of the catalyst and reduce total‑lifecycle costs.
Thermal regeneration. Heat treatment of deactivated manganese‑based catalysts at 100‑500°C can recover about 57.5% of activity at 300°C. However, excessively high temperatures may induce phase transformation of manganese oxides (e.g., MnO₂ to Mn₂O₃ above 530°C), causing irreversible structural damage.
Reductive regeneration. Hydrogen reduction at a mild 60°C can achieve about 55% activity recovery and selectively remove adsorbed oxygen species. Compared to thermal regeneration, hydrogen reduction consumes less energy and causes less damage to the catalyst structure.
Liquid‑phase regeneration. As an efficient regeneration method, liquid‑phase approaches have attracted widespread attention due to their operability and versatility. Water washing has been shown to fully restore the activity of poisoned catalysts in some cases.
In actual industrial practice, the appropriate regeneration scheme should be selected based on the deactivation cause. For scenarios where surface oxygen‑species accumulation or carbon deposition is the primary deactivation factor, periodic in‑situ thermal regeneration (dry hot air at 150°C for 1‑2 hours) is an effective maintenance measure.
The purchase price of a catalyst is merely the tip of the iceberg of its Total Cost of Ownership (TCO). Establishing a sound economic evaluation model is key to avoiding the trap of “cheap to buy, expensive to run.”
Four major components of TCO: Initial investment (catalyst material cost, reactor fabrication, installation and commissioning); operating energy (fan pressure‑drop‑related energy, heating energy if temperature elevation is required); replacement frequency (determined by the catalyst’s resistance to deactivation—high‑quality silica‑alumina‑supported composite catalysts typically have a design life of 2‑3 years, while low‑end products may fail within 6 months); and downtime losses (production stoppage costs in electronics manufacturing are extremely high—often far exceeding the catalyst price itself).
Quantitative comparison of annualized cost: Take two examples—Catalyst A costs 2000 RMB/L and lasts 2 years, giving an annualized cost of 1000 RMB/L·yr; Catalyst B costs 1000 RMB/L but lasts only 6 months, giving an annualized cost of 2000 RMB/L·yr. The lower‑priced catalyst has double the annualized cost of the higher‑priced one. Additionally, replacement labor, production loss, and potential compliance risks due to substandard efficiency must be factored in.
Decision recommendation: For critical applications such as cleanrooms, priority should be given to catalyst systems with strong moisture and poison resistance and high regeneration recovery, even if their unit price is higher—their TCO is often lower. Requiring suppliers to provide accelerated aging test data and peer‑industry case studies can validate lifetime expectations, shifting procurement decisions from “price‑driven” to “value‑driven.”
Integrating the analyses from all the above dimensions, the selection of ozone removal catalysts in electronics manufacturing can follow this systematic decision path:
Selecting an ozone removal catalyst for electronics manufacturing is never a simple “shelf comparison.” It is a multi‑dimensional decision that requires comprehensive consideration of reaction thermodynamics, materials science, reaction engineering, and engineering economics. Ultimately, the best catalyst is not the one with the highest laboratory‑measured activity, but the one that simultaneously meets the efficiency, durability, and economic requirements under your specific production‑line conditions. Only by deeply integrating technical feasibility with economic rationality can we achieve precise, long‑lasting, and safe ozone abatement in electronics manufacturing environments.
author: Gloria
date:2026/7/20
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