Johnson Matthey Advances Emission Control with Catalytic Converter Tech

In modern society, automobiles have become an indispensable mode of transportation. However, while providing convenience, vehicles also emit substantial exhaust gases that pose serious threats to both the environment and human health. Automotive exhaust contains multiple harmful substances, including carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), which not only pollute the air but can also trigger respiratory diseases, cardiovascular conditions, and other health issues. To mitigate these hazards, catalytic converters have emerged as critical components in vehicle exhaust purification systems.

Catalytic converters, also known as catalytic converters, are devices installed in vehicle exhaust systems to transform harmful gases into relatively harmless substances such as carbon dioxide (CO₂), nitrogen (N₂), and water vapor (H₂O). These devices serve as robust barriers, effectively reducing the environmental and health impacts of vehicle emissions while creating cleaner breathing environments.

Johnson Matthey stands as a global leader in catalytic converter technology with a rich history of innovation. As a specialty chemicals company, it develops, manufactures, and distributes high-performance catalysts and other specialty chemical products, providing cutting-edge solutions across multiple industries. In vehicle emissions control, Johnson Matthey delivers premium catalytic converter products and systems to automakers worldwide, contributing to improved air quality.

The efficiency of catalytic converters stems from their internal metal catalysts—substances that accelerate chemical reactions without being consumed. Common catalysts include platinum (Pt), palladium (Pd), and rhodium (Rh), which exhibit exceptional catalytic activity, stability, and durability in converting harmful exhaust components.

The catalytic process involves four key steps:

• Adsorption: Harmful gas molecules attach to the catalyst surface.
• Activation: Adsorbed molecules become chemically reactive.
• Reaction: Activated molecules transform into harmless compounds.
• Desorption: Resulting compounds detach, freeing the catalyst for new reactions.

Different catalyst systems are employed based on vehicle types and exhaust compositions:

• Platinum (Pt): Excels in oxidizing CO and HC.
• Palladium (Pd): Primarily oxidizes HC.
• Rhodium (Rh): Specializes in reducing NOx.

To maximize efficiency, precious metals are dispersed as nanoparticles on ceramic or metallic honeycomb substrates. These structures provide extensive surface areas for catalytic activity.

Modern gasoline vehicles predominantly use three-way catalysts (TWC) that simultaneously address three pollutants:

• Oxidation of CO to CO₂
• Oxidation of HC to CO₂ and H₂O
• Reduction of NOx to N₂

TWCs utilize platinum, palladium, and rhodium to facilitate these reactions under optimal air-fuel ratios (λ=1). Their honeycomb structure maximizes catalytic surface area.

Gasoline particulate filters (GPF) coated with TWC catalysts form TWFs, which control both gaseous pollutants and particulate matter.

Diesel engines employ multiple specialized catalysts:

Oxidizes CO and HC while converting NO to NO₂, achieving over 90% reduction.

Uses ammonia (NH₃) to reduce NOx to N₂ and H₂O, typically employing copper/iron zeolites or vanadium-titanium materials.

Captures NOx during cold starts before SCR systems activate, later releasing it for reduction during rich-burn cycles.

Eliminates excess NH₃ from SCR systems to prevent secondary emissions.

CSF combines DPF with DOC coatings, while SCRF integrates SCR functionality with particulate filtration, eliminating standalone DPFs in some configurations.

Global catalytic converter production consumes approximately 90 tons of platinum, 300 tons of palladium, and 30 tons of rhodium annually, with 30-50% sourced from recycling. Johnson Matthey plays a dual role in both manufacturing catalysts and recovering precious metals from spent converters, refining enough material annually to produce millions of new units.

The recovery involves:

1. Preprocessing (crushing/grinding)
2. Leaching (metal dissolution)
3. Extraction (solution transfer)
4. Precipitation (solid metal recovery)
5. Refining (purification)

These catalysts achieve over 90% conversion efficiency due to:

• High Activity: Accelerate reactions through unique electronic structures.
• Thermal Stability: Maintain performance under extreme temperatures.
• Durability: Resist mechanical wear and chemical corrosion.

The company drives innovation through:

• Advanced catalyst formulations
• Substrate material improvements
• Converter structural optimizations
• Emission control system enhancements

Johnson Matthey's sustainability initiatives focus on developing cleaner technologies, maximizing metal recycling, reducing production emissions, and promoting eco-friendly transportation alternatives.