With all of the technological advances lately, couldn’t a catalytic converter be designed with cheaper materials that aren’t worth stealing?
In: 2057
I work closely in this area, so I’ll be able to explain this to different complexity extents.
The answer is YES, but there are some caveats.
First of all, we need to understand **why we need a catalytic converter.** When internal combustion engines burn fuel there are harmful and undesired gases that are produced and that we don’t want to emit. The most important ones are *nitrogen oxides*, *carbon monoxide* (not to confuse with carbon dioxide or CO2) and *unburned fuel.* **Therefore, the catalytic converter was designed with the objective of reducing the emission of these gases.**
Second of all, we need to understand **how a catalytic converter works.** When gases come out of the engine and start passing through the catalytic converter, each of the harmful gases mentioned above will be converted into harmless gases with the help of specific metals. Here it is important to clarify something. This might be out of ELI5, but it is still very important to mention it. Which metal helps convert which gas depends on the nature of the reaction. For example, carbon monoxide and unburned fuel will need to be oxidized and nitrogen oxides will need to be reduced. When oxidation occurs, the harmless gases coming out are carbon dioxide and water and when reduction occurs, the harmless gas will be nitrogen and water. **In summary, specific metals in the catalytic converter help convert the harmful gases into harmless ones.**
Now, if we limit this discussion to engines using gasoline and Diesel, the metals used in catalytic converters in gasoline cars use Rhodium and Palladium to help reduce nitrogen oxides and Platinum to help oxidize the carbon monoxide and unburned fuel (Palladium can also contribute). Similarly, in Diesel engines, Platinum and Palladium help oxidize carbon monoxide and unburned fuel but in the case of reducing nitrogen oxides we use Copper, which is very cheap!
Rhodium is currently the most expensive metal of the three, followed by Palladium and Platinum. If you wanted to replace those metals, you would need to find other cheaper metals that can interact similarly. These metals actually exist but there are more variables that prevent them from becoming a final product. A second clarification, these compounds that are used to help convert the harmful gases are called *Catalysts*.
To give you an example, currently there are catalysts that are based on Copper and Cerium Oxide which are excellent for oxidation reactions and which can actually be more efficient than Palladium and Platinum ones. These catalysts are first tested at laboratory scale under simpler conditions and if they show promising performance, then, they are tested under more realistic conditions. You might ask yourself, why don’t we use this catalyst in industry? As it turns out, there are other important aspects to take into account to commercialize them. One of them is resistance to poisoning from sulfur which is present in fuels and unfortunately reduces the performance of the catalyst over time.
So, to summarize, yes, currently there are replacements with cheaper metals which work very well under somewhat ideal conditions and current research work involves improving other aspects that hinder the commercialization of the catalysts.
If people want me to explain more aspects in more detail, I would be more than happy to do it 🙂
Source: I’m a PhD in Chemical Engineering focused in the area of catalysis with emphasis in vehicle emission control.
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