Does the waste gas generated by corona ozonation contain oil mist or VOCs, and do these substances have a toxic effect on the catalyst?

In workshops dedicated to the surface treatment of plastic films, metal cables, or packaging materials, one can often detect a distinctive, "grassy" odor. This scent originates from the high concentrations of ozone generated by corona treatment equipment. To eliminate this harmful gas, ozone decomposition catalysts serve as the "gatekeepers" of environmental protection.

However, this line of defense faces a formidable challenge: corona exhaust gases contain not only ozone but are also frequently laden with oil mist and volatile organic compounds (VOCs). What impact do these substances have on the catalyst? Do they—in effect—"poison" it?

This article will provide a clear and accessible analysis of this critical technical pain point within the field of industrial environmental protection.

1. Corona Discharge: Both "Producer" and "Cleaner"

To understand this issue, we must first understand the dual role of corona discharge.

Corona discharge is the process of ionizing air using a high-voltage electrode. This process generates a large number of high-energy electrons and reactive species (such as ozone, hydroxyl radicals, etc.).

On one hand, industry uses this principle to treat VOCs: high-energy electrons directly break the molecular chains of VOCs, oxidizing and decomposing them into carbon dioxide and water.
On the other hand, in the surface treatment industry, corona discharge becomes a producer of ozone. When air is ionized at high voltage, oxygen molecules are split into oxygen atoms, which then combine to form ozone (O₃).

This raises a core question: When corona equipment is processing materials containing organic solvents (such as coating or printing), the exhaust gas is actually a mixture of "ozone" and "incompletely decomposed VOCs."

2. The "Invisible Killers" in Exhaust Gas: Oil Mist and VOCs

Corona exhaust is not a pure "ozone-air mixture." In most industrial scenarios, it also carries the following two types of harmful substances:

1. Oil Mist and Dust: Many materials being treated contain lubricating oils, plasticizers, or mold release agents on their surfaces. Under the high temperature and ionization effects of corona treatment, these substances volatilize or vaporize, forming micron-sized oil mist particles.
2. Residual VOCs: Although corona discharge itself can degrade VOCs, its removal efficiency is limited by energy density and typically struggles to reach 100%. Especially for high-concentration mixed VOCs, if the input energy is insufficient, some organic compounds (such as toluene, styrene, etc.) can "escape" or decompose into intermediate byproducts.

3. The Truth About Catalyst "Poisoning": Physical Coverage and Chemical Toxicity

Addressing the question posed at the beginning of the article: Are these substances toxic to catalysts?

The answer is yes, and they typically manifest in two forms: physical poisoning and chemical poisoning.

3.1 Physical Poisoning – "Coking" and Coverage

The microstructure of an ozone catalyst resembles a sponge, filled with nanoscale pores. This greatly increases the reactive surface area, enabling efficient ozone decomposition at room temperature.

When oil mist or high-boiling-point VOCs in the exhaust gas pass over the catalyst surface, they adhere to the pore walls like "glue." This phenomenon is technically referred to as electrode coking or catalyst carbon deposition.

• Consequence: Physical blockage prevents ozone molecules from reaching the internal active sites of the catalyst. This "outer layer" directly shields the contact between the catalyst and ozone, causing a sharp drop in ozone removal efficiency. This type of poisoning is typically reversible but extremely difficult to regenerate.

3.2 Chemical Poisoning – Active Site Deactivation

This is a more lethal form of poisoning. Certain specific VOCs or their decomposition byproducts can chemically react with the active components on the catalyst surface.

• Phenomenon: For example, silicon-containing organic compounds (common components in defoamers and mold release agents) can generate silicon dioxide (SiO₂) deposits on the surface under high temperature or ionization conditions, permanently sealing the active sites.
• Case Study: Research has shown that in DC corona discharge, although the presence of catalysts helps decompose byproducts, the complex chemical composition of the exhaust gas (such as nitrogen oxides and certain aromatic hydrocarbon derivatives) can alter the chemical state of the catalyst, leading to discharge "poisoning," i.e., a collapse in ozone generation or decomposition efficiency. Although this study focused on the discharge process, it also revealed the strong inhibitory effects of specific chemical substances on catalyst activity.

4. The Practical Dilemma: Why "Synergy" Becomes "Interference"

You may have heard that "non-thermal plasma + catalysis" is the golden combination for treating VOCs. Indeed, under ideal conditions, catalysts can synergize with the plasma, decomposing the ozone generated as a byproduct and further improving the mineralization rate of VOCs.

However, the situation is different in corona workshops:
In synergistic mode, the catalyst is positioned downstream. If the upstream corona discharge energy is insufficient (which is typical for corona treaters, as their primary purpose is surface treatment of films, not burning off VOCs), a large quantity of VOCs can "break through" the defense line and directly impact the catalyst.
These high-concentration VOCs can generate intense heat upon oxidation on the catalyst surface, or form polymers, leading to catalyst overheating or agglomeration. This is why the service life of catalysts in many corona exhaust treatment systems falls far below their design values.

5. Solutions and Protective Recommendations

To protect expensive catalysts, engineers typically implement the following "three lines of defense":

1. Pre-filtration (Oil Mist Protection): Install high-efficiency filtration sections or electrostatic oil removal devices before the exhaust gas enters the catalytic reactor. Removing liquid oil mist and dust is the first step in protecting catalyst lifespan.
2. High-Concentration Surge Protection: Control the process source to avoid large amounts of liquid solvents entering the corona unit directly. During system design, ensure the catalyst bed is located in an airflow that is "oil-free" and contains "low concentrations of organic compounds."
3. Select Poison-Resistant Catalysts: Targeted ozone decomposition catalysts have been developed. For example, using transition metal oxides (such as manganese-based) to replace some precious metals, and doping with special additives that resist water and oil, can significantly improve catalyst tolerance under harsh operating conditions.

Conclusion

Oil mist and VOCs in corona ozone exhaust are not just pollutants; they are "chronic poisons" for catalysts. They either suffocate catalyst activity through physical coverage or completely destroy their structure through chemical reactions.

A professional ozone treatment solution should not simply involve purchasing a catalyst; it requires designing a complete engineering system that includes pretreatment (oil and dust removal) + catalytic reaction. Only by stopping these "invisible killers" can the catalyst efficiently and durably safeguard the air quality in the workshop.

Appendix: Comparison of Catalyst Poisoning Types

Poisoning Type	Mechanism	Reversibility	Typical Pollutants
Physical Poisoning (Coking/Coverage)	Pollutants adhere to catalyst surface pores, physically shielding active sites	Extremely difficult to reverse	Oil mist, high-boiling-point VOCs
Chemical Poisoning (Deactivation)	Pollutants chemically react with active components, permanently destroying the structure	Irreversible	Silicon-containing organics, aromatic hydrocarbon derivatives

author：Gloria
date:2026-05-27