Why Catalysts Are Essential for VOCs Abatement in the Petrochemical Industry

Petrochemical VOCs treatment is inherently difficult due to the extreme complexity of waste gas components, severe fluctuations in operating conditions, and continuously tightening emission standards. Against the backdrop where adsorption, biofiltration, and direct combustion each have their own limitations, catalytic oxidation has become the mainstream choice for petrochemical VOCs treatment because of its low light‑off temperature, wide applicability, and absence of secondary pollution. The heart of catalytic oxidation technology is the catalyst – it not only solves the technical problem of "whether VOCs can be degraded," but also determines the economic equation of "how well and how cost‑effectively" the treatment is performed. By lowering the reaction activation energy, the catalyst enables complete oxidative decomposition of VOCs under mild conditions. Without a catalyst, the oxidation reaction requires a high temperature of 800 to 1200°C; with a catalyst, the reaction temperature drops to 250 to 500°C, dramatically reducing energy consumption. Every breakthrough in catalyst technology – from low‑temperature activity to sulfur/chlorine resistance, and from precious metals to non‑precious metal alternatives – expands the boundaries of petrochemical VOCs treatment. The catalyst is the indispensable technical core of petrochemical VOCs treatment, and also the critical enabler for enterprises to meet stricter standards while cutting costs and improving efficiency.

1. Stricter Standards Push Petrochemical VOCs Treatment into an Era of "Hard Constraints"

In 2025, the Ministry of Ecology and Environment officially implemented the revised Emission Standard for Air Pollutants in the Chemical Industry, tightening the VOCs emission limit from 120 mg/m³ down to 80 mg/m³. In general areas, the limit is 80 mg/m³, while in key regions (e.g., Beijing‑Tianjin‑Hebei and the Yangtze River Delta) it is further reduced to 50 mg/m³. The new standard also adds single‑factor concentration control indicators for characteristic pollutants such as benzene series and halogenated organics. For fugitive emissions, the fence‑line VOCs concentration must not exceed 2.0 mg/m³, and online monitoring equipment is required. Regarding treatment efficiency, the collection efficiency must be no less than 95%, and the removal efficiency of the end‑of‑pipe treatment facility must not be below 90%.

This round of standard adjustments has directly changed the design logic and operation rhythm of waste gas treatment systems in petrochemical plants. The old combination of "activated carbon adsorption + simple spray" can no longer achieve stable compliance. At the same time, the Emission Standard for Pollutants in the Petrochemical Industry (GB 31571‑2015) sets the non‑methane hydrocarbon (NMHC) emission limit for petrochemical units at 60 mg/m³, and some local standards further tighten it to 50 mg/m³ or even lower. Hebei Province issued its local standard Emission Control Standard for Volatile Organic Compounds from Industrial Enterprises (DB13/ 2322‑2025), which took effect on January 1, 2026. The continuous tightening of standards has become the primary driver pushing petrochemical enterprises to upgrade their VOCs treatment facilities.

2. Complex Composition + Variable Operating Conditions – The "Inherent Difficulties" of Petrochemical VOCs Treatment

The difficulty of petrochemical VOCs treatment arises first from the extreme complexity of the waste gas composition. Petrochemical waste gases contain a wide variety of VOCs, including alkanes, alkenes, aromatic hydrocarbons, halogenated hydrocarbons, and more. Studies show that alkanes account for the highest proportion among VOCs in petrochemical parks, reaching 42.3%, followed by aromatics (28.1%) and oxygenated organics (18.6%). Other research indicates that alkanes (70.4%) are a major component of VOCs. Among them, light alkanes (such as ethane and propane) have stable molecular structures with high C—H bond dissociation energies, making them among the most difficult VOCs components to degrade. The physical and chemical properties of different components vary greatly, so no single technology can handle all of them effectively.

Second, concentration fluctuates sharply. The VOCs concentration in petrochemical point sources can range from 0.2 mg/m³ to 46.3 mg/m³. Under conditions such as truck loading and tank breathing, the concentration can change by orders of magnitude within a short time. Such wide concentration swings demand that the treatment process have strong adaptability.

Third, fugitive emissions are widespread. Petrochemical plants have numerous fugitive sources – tank farms, process units, and wastewater treatment areas all have continuous emissions, and the total VOC concentration in refining and chemical units typically shows a diurnal pattern of higher levels in the morning and evening and lower levels at noon. Alkanes account for the highest proportion in all types of fugitive emissions. These low‑concentration, high‑volume gas streams impose very high economic requirements on the treatment technology – the cost must be manageable, otherwise it becomes unaffordable for the enterprise.

Faced with such complex emission characteristics, traditional treatment methods each have limitations:

• Adsorption only transfers pollutants rather than destroying them, and spent activated carbon is classified as hazardous waste;
• Biofiltration has low efficiency and requires a large footprint;
• Direct combustion can treat the gas but consumes extremely high energy.

The necessity of catalysts becomes evident precisely in addressing these challenges.

3. Catalytic Oxidation – A Technological Leap from "Can We" to "How Well"

Catalytic oxidation technology stands out among various VOCs treatment methods because it simultaneously solves two problems: "can it be degraded" and "can we afford it."

From a technical principle perspective, catalytic combustion is a typical gas‑solid catalytic reaction. The catalyst lowers the activation energy of the reaction between VOCs molecules and oxygen, altering the reaction pathway. On the catalyst surface, VOCs molecules are adsorbed, activated, and oxidized, ultimately converting into harmless CO₂ and H₂O. Compared with direct combustion, catalytic combustion reduces the reaction temperature from 800 to 1200°C down to 250 to 500°C, drastically cutting energy consumption. Because the oxidation temperature is lower, the formation of thermal NOx from N₂ in the air is greatly suppressed, avoiding secondary pollution.

In terms of removal efficiency, catalytic combustion achieves impressive VOCs destruction. Studies show that precious‑metal catalysts can achieve removal efficiencies of 95% to 98%, while metal‑oxide catalysts reach 90% to 95%. Under optimized conditions, catalytic combustion can attain VOCs removal rates of over 98%. Catalytic combustion technology offers high removal efficiency, a wide concentration operating window, and no secondary pollution.

From an economic standpoint, catalytic combustion strikes the best balance between "complete destruction" and "cost‑effectiveness." Catalytic combustion saves 25% to 40% in operating costs compared with regenerative thermal oxidation (RTO), and its heat recovery efficiency can exceed 90%. With proper maintenance, catalysts have a service life of 24 to 36 months. For petrochemical enterprises, this means meeting emission standards while keeping treatment costs under control.

Comparing the various technology routes: adsorption only transfers pollutants and creates hazardous waste; direct combustion is energy‑intensive; biofiltration is inefficient and land‑consuming. Only catalytic oxidation satisfies both the "complete destruction" and "cost‑effective" requirements simultaneously. Catalytic oxidation is one of the most effective methods for the harmless treatment of VOCs.

4. The Core Battlefield of Catalysts – Triple Breakthroughs in Low Temperature, Efficiency, and Economy

The essential role of catalysts in VOCs treatment can be understood from three dimensions: low temperature, efficiency, and economy.

Low‑Temperature Breakthrough

The most fundamental value of a catalyst is that it lowers the temperature threshold for the oxidation reaction. Without a catalyst, complete oxidation of VOCs requires 800 to 1200°C; with a catalyst, the temperature drops to 250 to 500°C. This substantial temperature reduction directly brings about significant energy savings and improved safety. Catalytic combustion is flameless, making it inherently safer than direct combustion. Low‑temperature catalysis remains a continuous R&D focus. Manganese‑based catalysts, known for their excellent redox activity, abundant oxygen vacancies, good thermal stability, and low cost, are regarded as highly promising materials for VOCs degradation.

Efficiency Breakthrough

Catalysts greatly increase the oxidation reaction rate by lowering activation energy and concentrating reactant molecules on the surface. Studies show that under conditions of organic waste gas concentration 300 to 9000 mg/m³, space velocity 10,000 to 20,000 h⁻¹, and inlet temperature 200 to 300°C, the purification efficiency can exceed 98%. Regenerative catalytic oxidation (RCO) generally achieves purification efficiencies of over 99%. After catalytic oxidation treatment, the NMHC concentration in the purified gas can be as low as below 10 mg/m³, and characteristic pollutants such as benzene, toluene, and xylene can be reduced below detection limits.

Economic Breakthrough

Catalysts not only determine treatment effectiveness but also directly affect operating costs. With proper maintenance, catalyst service life is 24 to 36 months. By substituting non‑precious metals, catalyst costs can be further reduced. With appropriate catalyst selection and maintenance, the operating expenses of catalytic combustion are far lower than those of direct combustion. For petrochemical enterprises, the choice of catalyst directly determines the long‑term economic viability and competitiveness of their treatment system.

5. From Laboratory to Production Line – Industrial Validation of Catalytic Oxidation Technology

The value of catalytic oxidation technology in petrochemical VOCs treatment has been fully demonstrated through numerous industrial applications. Below are several representative examples.

VOCs Treatment in a Methanol‑to‑Olefins (MTO) Catalyst Production Facility

During the production of MTO catalysts, organic templating agents inevitably generate high‑concentration VOCs process gases containing hydrocarbons, amines, aldehydes, alcohols, etc. After adopting catalytic oxidation, the industrial unit operated stably for over 4,000 hours, reducing the VOCs concentration in the tail gas from 300 to 3000 mg/m³ down to below 20 mg/m³. The purified NMHC concentration consistently met standards, and benzene, toluene, xylene, and other characteristic pollutants were all below detection limits.

Catalytic Oxidation Application in an S‑MTO Catalyst Production Unit

Catalytic oxidation achieved a VOCs removal efficiency of over 98.5%, with the tail gas NMHC concentration stably below 10 mg/m³, reducing high‑concentration VOCs emissions by approximately 15,000 tons per year.

Catalytic Oxidation of Waste Gases from Petrochemical Wastewater Treatment Plants

For the high‑concentration waste gases from oil separators and flotation units in refinery wastewater treatment, and for the low‑concentration gases from aeration tanks, treatment trains of "desulfurization + total hydrocarbon concentration equalization – catalytic oxidation" and "scrubbing – adsorption – regeneration gas catalytic oxidation" were respectively applied. After treatment, the purified NMHC concentration was below 60 mg/m³, hydrogen sulfide below 0.2 mg/m³, and benzene, toluene, and xylene were below detection limits.

Integrated Treatment of Refinery VOCs

In actual engineering practice, gasoline loading vapors can be treated by "low‑temperature diesel absorption"; for VOCs from chlorobenzene and nitrochlorobenzene units and tank storage, a combined "regenerative thermal oxidation – caustic scrubbing – activated carbon adsorption" system can be used, achieving purified NMHC levels below 10 mg/m³.

These industrial practices fully prove that catalytic oxidation technology not only meets increasingly stringent emission standards but also provides long‑term operational stability and reliability. Catalytic oxidation‑based combination processes have become a mature technical route for VOCs treatment in the petrochemical industry.

6. Going Deeper – Three Frontier Directions: Sulfur Resistance, Low Temperature, and Non‑Precious Metals

Although catalytic oxidation technology has achieved remarkable results in petrochemical VOCs treatment, industry demands on catalyst technology continue to rise. Currently, the following three directions are at the forefront of catalyst R&D.

Sulfur‑Resistant Catalysts

Petrochemical waste gases often contain sulfur compounds, and catalyst sulfur poisoning has long been a pain point. In actual industrial service, sulfur‑containing species typically compete with VOCs molecules for adsorption on active sites, causing deactivation. Under certain conditions, sulfur species may even react with the active phase or support to form sulfates, resulting in irreversible poisoning. Current major anti‑sulfur strategies include constructing bimetallic precious‑metal systems, elemental doping, acid treatment, and building core‑shell structures. A recent review article from the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, systematically summarizes the fundamental differences in sulfur resistance and deactivation behavior between precious‑metal catalysts and transition‑metal oxide catalysts in sulfur‑containing environments. Advanced anti‑sulfur approaches include electronic structure modulation, interface engineering optimization, and dynamic response design – by tuning the electron cloud distribution and band structure of the catalyst, one can simultaneously enhance the adsorption and activation of VOCs while promoting desorption of sulfur species; constructing core‑shell structures, heterojunctions, and other interface engineering can effectively block sulfate formation pathways.

Low‑Temperature High‑Performance Catalysts

Lowering the catalytic reaction temperature is the core direction for reducing energy consumption. Low‑temperature catalytic oxidation, with its high potential and good economics, has become a highly promising approach. Oxygen vacancy (Ov) engineering has been proven to enhance the intrinsic catalytic activity of metal‑oxide‑based catalysts and is recognized as a transformative strategy for non‑precious‑metal oxide catalysts to break through the activity‑stability‑cost trade‑off. Through oxygen vacancy regulation, the catalytic activity of transition metal oxides such as Co₃O₄, MnO₂, and CeO₂ can be significantly improved.

Non‑Precious Metal Substitution

Precious‑metal catalysts are costly and dependent on scarce resources. Non‑precious‑metal catalysts based on doped transition‑metal oxide materials offer the advantages of low cost, high activity, and good stability in VOCs catalytic combustion. Technical innovations include: enhancing the redox capacity of transition‑metal oxide materials through doping modification; developing hydrophobic and sulfur‑resistant modification technologies to improve water and sulfur tolerance; and inventing new slurry formulations to reduce shedding rates and enhance the structural stability of monolithic catalysts. Such catalysts can achieve conversion rates of over 98%. Non‑precious‑metal catalysts have become a major R&D focus in the field of VOCs catalytic oxidation.

7. Conclusion

The reason why petrochemical VOCs treatment cannot do without catalysts is that catalysts address three levels of issues simultaneously:

1. Technical level: Catalysts enable complete oxidative decomposition of VOCs under mild conditions, lowering the reaction temperature from 800 to 1200°C to 250 to 500°C, thus solving the "can it be treated" problem.
2. Efficiency level: Catalytic combustion achieves VOCs removal efficiencies of 95% to 98% (precious‑metal catalysts) or 90% to 95% (metal‑oxide catalysts), with NMHC concentrations stably below 10 mg/m³, answering the "how well" question.
3. Economic level: Catalytic combustion saves 25% to 40% in operating costs compared with RTO, and with proper maintenance, catalyst service life can reach 24 to 36 months, addressing the "can we afford it" concern.

Catalysts are not only the technical core of VOCs treatment, but also the key technological support for the petrochemical industry to cope with continuously tightening standards and achieve green transformation. As breakthroughs continue in sulfur resistance, low‑temperature operation, and non‑precious metal substitution, the central role of catalysts in petrochemical VOCs treatment will only be further consolidated. For petrochemical enterprises, a deep understanding of catalyst mechanisms, proper selection, and rational maintenance are critical – not only for compliance but also for long‑term economic performance and competitiveness. The catalyst – this seemingly small material – carries the major mission of the industry's sustainable development.

author: Gloria
date:2026/8/11