How Is CO Removed from Industrial Gases?

 Carbon monoxide (CO) is often present as a low-concentration impurity in industrial gases, but even trace levels can affect downstream processes and gas purity in air separation, compressed air, and high-purity gas systems. Effective CO removal requires more than evaluating catalyst activity alone. Oxygen concentration, inlet CO concentration, operating temperature, space velocity, moisture, and other impurities can all affect catalytic performance. Hopcalite catalysts typically promote the oxidation of CO with oxygen, converting CO into CO₂. Therefore, industrial CO purification systems should evaluate catalyst performance together with reaction conditions, mass transfer, moisture resistance, poisoning resistance, and long-term stability.

Why Does CO Need to Be Removed from Industrial Gases?

Carbon monoxide is a colorless and odorless gas that can enter industrial gas systems from raw air, compression equipment, combustion processes, or other upstream operations. Although CO is often present at relatively low concentrations, even trace impurities may need to be controlled when high-purity gases or precision industrial processes are involved.

For example, in air separation, high-purity gas production, and compressed air purification, CO may enter downstream processes as a trace contaminant. When strict gas purity requirements apply, the objective is not simply to reduce CO to a low concentration once, but to maintain stable and continuous purification performance throughout system operation.

Therefore, the key to industrial CO removal is not simply achieving a high initial removal efficiency. The purification process should be designed around the actual gas composition and operating conditions to provide consistent long-term performance.

What Is the Basic Principle of CO Catalytic Oxidation?

Several technologies can be used to remove CO from industrial gases, including adsorption, separation, and catalytic oxidation. For gas streams containing sufficient oxygen, catalytic oxidation is an important approach for CO purification.

The overall reaction can be represented as:

2CO + O₂ → 2CO₂

Hopcalite catalysts generally contain copper oxides and manganese oxides as active components. Through surface oxidation-reduction processes, these active components promote the reaction between CO and oxygen. Under suitable temperature and gas composition conditions, CO can be oxidized to CO₂, thereby reducing the CO concentration in the gas stream.

However, oxygen is required for catalytic CO oxidation. Therefore, conventional CO catalytic oxidation cannot simply be applied to high-purity gas streams containing little or no oxygen. The gas composition should first be evaluated to determine whether sufficient oxygen is available for the reaction. If oxygen addition is technically feasible, its impact on final gas purity and downstream processes must also be considered.

Why Is Catalyst Activity Alone Not Enough to Evaluate CO Removal?

Laboratory catalyst activity is an important performance indicator, but it does not necessarily represent the actual performance of a catalyst in an industrial purification system.

The first factor is inlet CO concentration. Different CO concentrations can affect catalyst loading and reaction rates. The second factor is operating temperature. Catalytic oxidation generally requires an appropriate temperature to achieve a sufficient reaction rate, while industrial systems must also consider energy consumption and equipment limitations.

Gas space velocity is another critical factor. Increasing space velocity means that a larger volume of gas passes through the catalyst bed within a given period, reducing the effective contact time between the gas and catalyst. If catalyst activity and reactor design are insufficient for the required gas flow, CO conversion may decrease.

For this reason, CO catalyst evaluation should consider inlet concentration, operating temperature, space velocity, and outlet concentration together rather than relying on the conversion rate obtained under a single laboratory test condition.

How Do Moisture and Other Impurities Affect CO Catalytic Oxidation?

Industrial gas streams can differ significantly from laboratory test gases. Among the various factors that influence oxide-based catalysts, water vapor is particularly important.

When the gas contains elevated moisture, water molecules may adsorb onto the catalyst surface and occupy active sites, potentially affecting the interaction between CO, oxygen, and the catalyst surface. Under certain operating conditions, increased humidity may therefore reduce the reaction rate.

Other contaminants, such as sulfur-containing compounds, halogen-containing compounds, and substances that strongly interact with catalyst active components, may also cause catalyst deactivation or reduce long-term catalytic performance.

Consequently, industrial projects should evaluate not only CO concentration but also moisture content, impurity composition, and the operating temperature range. For continuous industrial operation, moisture resistance, poisoning resistance, and long-term stability can be just as important as initial catalyst activity.

How Should a Catalyst Be Selected for Industrial CO Removal?

Catalyst selection for industrial CO purification should be based on several operating parameters rather than a single performance value.

1. Determine the Gas Composition

The first step is to identify the CO concentration, oxygen concentration, moisture content, and other potential impurities in the gas stream. Reliable gas composition data provide the foundation for determining whether catalytic oxidation is suitable and which catalyst characteristics are required.

2. Determine the Actual Operating Temperature

The catalyst should provide stable CO oxidation performance within the temperature range that the equipment can maintain over long-term operation. Catalyst data obtained only at elevated temperatures may not accurately represent performance under actual plant conditions.

Operating temperature should also be evaluated together with energy consumption, equipment limitations, and process requirements.

3. Calculate Space Velocity and Contact Time

For the same catalyst, gas flow rate, catalyst loading, and reactor bed configuration can all influence the actual purification performance. Catalyst loading and reactor dimensions should therefore be designed according to the required gas flow and target outlet CO concentration.

4. Evaluate Long-Term Stability

Industrial gas purification systems often operate continuously for extended periods. Catalyst mechanical strength, moisture resistance, poisoning resistance, and long-term activity retention should therefore be included in the evaluation.

A catalyst with high initial activity does not necessarily provide the best long-term performance if its activity decreases significantly under actual operating conditions.

5. Focus on the Required Outlet CO Concentration

Final catalyst selection should not be based solely on catalyst activity data. The required outlet CO concentration should first be defined according to the downstream process. Catalyst performance should then be validated under conditions that closely represent the actual application.

What Else Should Be Considered in a CO Removal System?

It is important to understand that catalytic CO oxidation does not simply make CO disappear. The reaction converts CO into CO₂. Therefore, if the downstream process also has strict requirements for CO₂ concentration, an additional CO₂ removal or purification step may be necessary after catalytic oxidation.

A complete industrial gas purification process should therefore be evaluated as an integrated system covering inlet CO concentration → catalytic oxidation → CO₂ control → final gas purity.

For air separation, compressed air, and high-purity gas systems, a suitable CO removal solution should be based on actual operating conditions. Catalyst activity is only one part of the evaluation. Oxygen availability, temperature, space velocity, moisture, contaminants, and long-term stability can all determine the final purification performance.

Therefore, the selection principle for industrial CO catalysts should shift from asking “Which catalyst has the highest activity?” to asking “Which catalyst is best matched to the actual operating conditions?”. By evaluating catalyst performance together with gas composition, equipment conditions, and the required outlet CO concentration, industrial systems can achieve more stable and sustainable CO purification.

author:kaka

date:2026/8/18