Catalytic converters are emission control devices that reduce toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Inside a catalytic converter, there are several precious metals that act as catalysts, like platinum, palladium, and rhodium. These metals play a vital role in catalyzing the chemical reactions that convert harmful compounds into less harmful ones.
What is a catalytic converter?
A catalytic converter is a device that uses a catalyst to convert three harmful compounds in car exhaust into harmless compounds. The three harmful compounds that a catalytic converter converts are:
- Carbon monoxide into carbon dioxide
- Hydrocarbons into carbon dioxide and water
- Nitrogen oxides back into nitrogen and oxygen
The catalyst in a catalytic converter is usually a combination of several precious metals including platinum, palladium, and rhodium. These metals act as catalysts, meaning they facilitate chemical reactions in the converter without undergoing any permanent chemical change themselves. The precious metals provide active sites where exhaust molecules can interact with the catalyst surface and undergo chemical reactions.
How does a catalytic converter work?
The basic working principle of a catalytic converter is to convert harmful exhaust gases into harmless gases through redox reactions. Here are the steps:
- Exhaust gas from the engine enters the catalytic converter.
- The exhaust gases come into contact with the catalyst (platinum, palladium, rhodium).
- The catalyst facilitates chemical reactions that convert the harmful gases into harmless ones. For example:
- CO + O2 -> CO2
- 2CxHy + 2O2 -> 2CO2 + 2H2O
- 2NOx -> N2 + xO2
- The less harmful gases exit the catalytic converter and get emitted into the air.
So in summary, the converter uses a redox reaction catalyzed by the precious metals to convert toxic exhaust gases into more benign ones.
How much platinum is typically in a catalytic converter?
The amount of platinum in a catalytic converter can vary depending on:
- Type of vehicle
- Engine size
- Emissions standards in the country
- Whether it’s a diesel or gasoline engine
However, according to experts, here are some general estimates for the platinum content of catalytic converters by vehicle type:
| Vehicle Type | Platinum Content |
|---|---|
| Gasoline car | 2-7 grams |
| Diesel car | 3-10 grams |
| Hybrid car | 2-15 grams |
| Gasoline truck | 5-15 grams |
| Diesel truck | 8-25 grams |
So for a typical passenger gasoline car, the platinum content is estimated to be between 2-7 grams. Diesel vehicles tend to have higher platinum content compared to gasoline, and trucks tend to have higher loads than passenger cars. Hybrid vehicles can have widely varying amounts depending on the engine size and type.
Factors that determine platinum content
The key factors that determine the platinum content in catalytic converters include:
- Vehicle type – Trucks tend to have higher platinum loads than passenger cars.
- Engine size – Vehicles with larger engine sizes require more platinum to treat the higher exhaust gas volumes.
- Fuel type – Diesel vehicles typically need more platinum compared to gasoline.
- Emissions standards – Stringent emissions standards in some countries require higher platinum loading.
- Catalyst efficiency – Less efficient catalyst formulations require more platinum.
Newer vehicle models meeting tighter emissions standards tend to have greater platinum, palladium and rhodium loads compared to older models.
Platinum’s role and function
Platinum plays a crucial role in the functioning of catalytic converters. Here are some key functions of platinum in catalytic converters:
- Oxidation of carbon monoxide (CO) and hydrocarbons (HC)
- Reduction of nitrogen oxides (NOx)
- Stabilizing the surface area and dispersion of particles on the catalyst support material
- Increasing catalyst efficiency and conversion rates of toxic gases into benign gases
- Withstanding high temperatures and providing oxidation and reduction reaction sites
- Providing oxygen storage capacity to manage oxygen levels during combustion
Platinum is exceptionally well-suited for use in catalytic converters because of its:
- Excellent catalytic activity
- High resistance to chemical degradation
- Stability at high temperatures
- Outstanding durability
- Ability to catalyze both oxidation and reduction reactions
These properties make platinum highly effective for catalyzing the converter’s chemical reactions and providing a long service life.
Importance of platinum in catalytic converters
Platinum plays an irreplaceable role in catalytic converters. Here are some reasons why platinum is so important:
- Exceptional efficiency – Platinum provides the highest conversion efficiency for reducing toxic emissions compared to other metals.
- Temperature resistance – The high melting point of platinum allows catalytic converters to operate at very high temperatures of 900°C and beyond.
- Stability – Platinum maintains its chemical properties under prolonged exposure to high heat and vibration.
- Longevity – Platinum provides exceptional longevity and can remain effective for over 10 years and 120,000 miles of driving.
- Dual catalytic abilities – Platinum facilitates both oxidation and reduction reactions, enabling the converter to handle multiple pollutants.
- Cost effectiveness – Only a small amount of platinum is needed to achieve high performance catalytic conversion in converters.
In short, platinum enables catalytic converters to meet stringent emissions standards for reducing toxic gases over hundreds of thousands of miles of use. It plays an irreplaceable role that no other material can feasibly mimic or replace in modern catalytic converter designs.
Global platinum demand from catalytic converters
Catalytic converters are the single greatest source of global demand for platinum. According to Johnson Matthey, around 40% of total platinum demand worldwide comes from catalytic converters used in vehicle emissions control systems.
Some key facts about platinum demand for catalytic converters:
- In 2018, over 7.2 million ounces of platinum were used in catalytic converters globally. This accounted for around 40% of total platinum demand that year.
- Diesel vehicles use approximately 5 to 10 grams of platinum per converter which is greater than the 2 to 5 grams used by gasoline engines.
- Stricter emissions standards have increased platinum loadings in catalytic converters for both diesel and gasoline vehicles.
- Expansion of catalytic converter use in light-duty and heavy-duty vehicle segments is increasing global platinum demand.
- China has become the top consumer of platinum for auto catalysts as vehicle production and higher emissions standards ramp up in the country.
Due to their essential role in emissions control systems, catalytic converters are expected to remain the dominant source of global platinum demand for the foreseeable future.
Platinum price trends
Platinum prices have shown significant volatility over the past decade owing to fluctuating supply and demand dynamics. Here are some key trends in platinum pricing:
- Platinum prices peaked at over $2,200 per ounce in 2008 before declining to less than $1,000 per ounce in the aftermath of the global recession.
- Prices recovered back above $1,700 per ounce in 2011-2012 before dropping to around $1,000 in 2013-2015 during a period of weak economic growth.
- In 2016, platinum fell below gold prices for the first time since 2001 and traded under $1,000 due to oversupply conditions.
- From 2018 to late 2021, platinum prices saw a recovery back to the $1,000 to $1,300 range driven by resurgent demand and some supply reductions.
- More recently in 2022, platinum has traded around $900 to $1,000 per ounce due to economic uncertainty and fears of a global recession.
Platinum prices remain volatile and are likely to see ongoing fluctuations based on broader economic conditions as well as supply/demand dynamics in the automotive and industrial sectors. Constraints on Russian palladium supply in 2022-2023 may also drive some substitution demand towards platinum.
Recycling platinum from catalytic converters
The platinum present in spent catalytic converters can be recovered through recycling. Here are some key facts about recycling platinum from old catalytic converters:
- Around 15-20% of the world’s platinum supply comes from recycled catalytic converters.
- Processing companies crush and grind the ceramic honeycomb of old converters to powder before treating it with acids, high temperatures, and chemicals to dissolve out the platinum.
- Extracted platinum is refined to high purity levels exceeding 99.95% before being sold back to manufacturers.
- Automotive companies recycle converters from old vehicles, while third-party companies specialize in recovering platinum from scrap converters.
- Recycling platinum is an environmentally beneficial activity since it reduces the need for fresh mining of platinum ore.
However, recycling rates for platinum remain relatively low compared to metals like aluminum or gold. Logistical challenges in collecting and transporting scrap catalytic converters often hinders the economics of recycling. There is potential to increase global platinum recycling rates through greater coordination in the supply chain and more scrap collection infrastructure.
Conclusion
Platinum is an essential and irreplaceable component in catalytic converters used for emissions control in both diesel and gasoline vehicles. The typical platinum content for gasoline car converters ranges from 2-7 grams, while diesel vehicles often use 3-10 grams. Trucks and other larger vehicles may contain higher platinum loads ranging from 5-25 grams per converter.
Stringent emissions regulations continue to drive demand for platinum in autocatalyst applications, making this the single greatest source of global platinum demand. While platinum prices have seen volatility over the past decade, the ongoing need for platinum’s exceptional catalytic properties for pollution abatement ensures it will remain a critical material for modern and future vehicles. Improving recycling rates for reclaiming platinum from spent converters also offers environmental benefits.
