VOCs waste gas treatment in painting workshops: How to correctly select VOC catalysts?

In the coating industry, the treatment of volatile organic compounds (VOCs) waste gas generated in spray booths and spray painting workshops is a core aspect of environmental compliance for enterprises. Catalytic combustion technology, due to its advantages such as high purification efficiency, low energy consumption, and no secondary pollution, has become the mainstream process for VOCs treatment in spray painting workshops. As the "heart" of the catalytic combustion system, the selection of the catalyst directly determines the treatment effect, operating cost, and system stability. Faced with various types of VOC catalysts on the market, how should spray painting workshops choose? This article will provide you with a complete selection guide.

I. Typical Characteristics of VOCs Waste Gas in Spray Painting Workshops

The waste gas from spray painting workshops has distinct industry characteristics, mainly reflected in the following three aspects:

1. Complex composition, high proportion of benzene compounds: The waste gas contains aromatic hydrocarbons such as benzene, toluene, and xylene, as well as organic compounds such as alcohols, esters, and ketones. Studies show that toluene, xylene, and ethylbenzene account for 79% to 99% of the total VOCs emitted by the spray painting industry in the Yangtze River Delta region.

2. Large fluctuations in concentration and air volume: Affected by spray painting intensity, paint type, and drying temperature, VOC concentrations in spray painting workshops typically fluctuate between 20 and 200 mg/m³.

3. Containing paint mist particles: Exhaust gas often carries a large amount of paint mist, which must undergo efficient pretreatment (such as filtration and water washing) before entering the catalytic combustion system; otherwise, it will lead to catalyst pore blockage and a rapid decline in activity.

II. Comparison of Mainstream VOC Catalyst Types

Currently, there are three main types of VOC catalysts suitable for spray painting workshops:

Noble metal catalysts (platinum, palladium): High activity at low temperatures, achieving 95% to 99% VOCs decomposition efficiency at 200–350℃, especially effective for removing benzene compounds. Disadvantages include higher cost and sensitivity to impurities such as sulfur and chlorine.

Non-precious metal catalysts (oxides of manganese, copper, cobalt, etc.): Cost is only 1/10 to 1/50 that of precious metals, with good high-temperature resistance, suitable for treating oxygen-containing VOCs (such as acetone and ethyl acetate). However, their ignition temperature is relatively high (300-500℃), and their degradation efficiency for benzene compounds is slightly lower than that of precious metals.

Composite catalysts (such as platinum-palladium bimetallic catalysts, rare earth modified catalysts): Balance activity and cost, efficiently converting VOCs at 200-300℃, widely used in low-temperature, low-sulfur conditions such as automotive painting and furniture spraying.

III. Four Core Dimensions for Catalyst Selection in Spray Painting Workshops

1. Selecting the Active Component Based on Waste Gas Characteristics

The waste gas from spray painting workshops has a high content and strong stability of benzene compounds. It is recommended to prioritize platinum/palladium-based precious metal catalysts, whose activity temperature window is 250-350℃, ensuring efficient degradation of aromatic hydrocarbon VOCs. If the company has a limited budget and the proportion of oxygen-containing VOCs in the waste gas is high, manganese-cobalt composite oxide non-precious metal catalysts can be considered.

2. Focus on Core Performance Parameters

When selecting a catalyst, the following indicators should be carefully checked:

- Ignition temperature: Should be below 250℃ to ensure rapid low-temperature start-up;

- Purification efficiency: Should consistently reach above 95%;

- Space velocity range: 10000~20000 h⁻¹, reflecting the catalyst's processing capacity.

3. Emphasize Anti-poisoning Capability

Impurities such as sulfur and chlorine in spray painting exhaust gas can cause catalyst poisoning and deactivation. For sulfur-containing exhaust gas, sulfur-resistant catalysts (such as platinum-palladium catalysts containing composite rare earth oxide additives) can be selected; for chlorine-containing exhaust gas, chlorine-resistant modified catalysts containing cerium dioxide can be selected, utilizing cerium dioxide to adsorb chloride ions and protect active sites.

4. Match Process Conditions

If the workshop has a large air volume and low concentration, a combined process of "adsorption concentration + catalytic combustion" (zeolite rotor + catalytic combustion) can be used to concentrate the exhaust gas before treatment, ensuring purification efficiency while reducing operating energy consumption. The inlet temperature of catalytic combustion is typically controlled between 200 and 350℃; therefore, the catalyst's activation temperature should start below 250℃.

IV. Carrier Selection: An Essential Foundation

The most commonly used carrier for VOCs treatment in spray painting workshops is cordierite honeycomb ceramic, which has a moderate specific surface area (50-200 m²/g), low airflow resistance, high mechanical strength, and regular pores that do not easily accumulate dust. High-quality catalysts can have a coating specific surface area exceeding 130 m²/g, ensuring high dispersion of active components and improving purification efficiency.

To ensure long-term stable operation of the catalyst, it is recommended to: perform thorough exhaust gas pretreatment to remove paint mist particles and impurities; regularly monitor system pressure differential and outlet concentration to promptly assess catalyst activity; restore activity through thermal regeneration when it decreases by less than 20%; and perform chemical cleaning when activity decreases by 20% to 50%. During shutdown, use inert gas purging to prevent residual organic matter from polymerizing at high temperatures and clogging the pores.

Selecting a VOCs catalyst for a spray painting workshop is a complex undertaking, requiring comprehensive consideration of exhaust gas composition, concentration, airflow, temperature, and emission standards. Generally, for most spray painting workshop conditions, platinum-palladium based precious metal catalysts paired with cordierite honeycomb ceramic supports are the most reliable choice, achieving purification efficiencies of over 95% at 200-350℃, effectively addressing recalcitrant VOCs such as benzene compounds. If the exhaust gas contains sulfur or chlorine, catalysts modified to resist poisoning should be prioritized. Scientific selection not only ensures compliance with emission standards but also achieves multiple benefits, including energy saving, reduced consumption, and optimized operation and maintenance costs.

Contact our technical team for a customized catalyst selection solution tailored to your workshop's specific conditions!

author：Gloria
date:2026-04-23