If the most easily stolen part of a battery car is the battery, which part is more likely to be stolen for a car with more complex parts?
This article is reproduced from the public account "Global Science"
Written by Wang Yibo
Reviewer 27
On a dark and windy night in the month, cars that were "sleeping" were "woken up" by the sound of metal tools — someone "cutting" the parts of their chassis. However, the owner of the car is not aware of what is happening, and only after turning on the engine in the morning can he hear the exhaust sound of the car "wailing". And for the careless owner, the car also has to let its own ass emit black smoke to send a distress signal: "The three-way catalyst on my chassis has been stolen!" ”。
Image credit: pixabay
The three-way catalytic converter is the main part of the exhaust gas treatment system after the automobile machine. It is not only thieves who secretly manipulate these components, but also automakers that have been exposed as "emission gates" in recent years.
In September 2015, the U.S. Environmental Protection Agency accused Volkswagen of installing software specifically for exhaust emissions testing in some of its diesel vehicles, which can identify whether the car is in a state of detection and adjust the exhaust gas treatment device during the inspection to meet high environmental standards. Subsequently, large automobile manufacturers such as Mercedes-Benz and Ford were exposed to the problem of emissions fraud. In China, it is reported that some auto repair shops will help to install three-way catalytic converters on the time of car inspection, and then remove them after annual inspection.
But the question is, whether it is a thief or a car manufacturer, why should it go to such great pains to install, disassemble and control the ternary catalyst of the car? Before answering this question, we must go back to the 20th century, when catalytic converters were about to appear.
The birth of the catalyst
Since the early 20th century, Los Angeles has been known for its hazy weather. On days shrouded in smog, children are forced to stay at home and cannot leave the house, and the emergency rooms of hospitals are packed with patients with headaches and shortness of breath. The whole of Los Angeles is at a low ebb, forcing people to constantly look for solutions to the problem of air pollution.
Dr. Arie Haagen-Smit, a professor of chemistry at the California Institute of Technology, played a key role in the fight against smog. He began studying air pollution in 1948, not only discovering the chemical composition of smog, but also studying how smog is produced in real environments. He believes that the formation process of smog is complex, involving the role of nitrogen oxides, hydrocarbons and sunlight.
Los Angeles, USA, shrouded in smog in 1948. (Image source: UCLA Library Special Collections)
In 1968, he joined the California Air Resources Board and found that air pollution sources can be divided into 2 categories – stationary sources, including large factories and mainly cars. At the time, California decided to address the latter, the car's exhaust emissions, first.
What's more, in 1970, the U.S. Congress passed the Clean Air Act, and Richard Nixon, then president of the United States, created the U.S. Environmental Protection Agency under great pressure.
For car exhaust, different models, engines, fuels and other factors will make their composition different. However, in general, car exhaust mainly includes 3 pollutants: unburned or incompletely burned hydrocarbons (HCs), carbon monoxide (CO) and nitrogen oxides (NOx, mainly NO). The Clean Air Act requires vehicle emissions to be reduced to 10% of HC, CO and NOx emissions by 1976. With no other solution to meet such stringent legal requirements, catalysts in cars began to enter history. And under the impetus of many forces, a three-way catalytic converter was born in 1981 and became the core of the automotive exhaust gas treatment device that has been used today.
Three-way catalytic converter
When a catalytic converter can process three kinds of automotive exhaust gases at the same time, HC, CO and NOx, it is called a three-way catalytic converter.
The problem is that HC and CO are reducing substances, while NOx is oxidizing, so to convert toxic car exhaust into other non-toxic substances, oxidation and reduction reactions need to be carried out separately. Among them, HC is oxidized to carbon dioxide and water, CO is oxidized to carbon dioxide, and NOx is reduced to nitrogen.
There are many complex processes involved, so it is necessary to find a more efficient catalyst to convert more toxic exhaust gases into non-toxic products (i.e. catalytic selectivity). Moreover, a large number of hydrocarbons are generated during cold start of the car (the temperature is low when the engine is just started), and in order to avoid these substances being directly emitted into the air, the three-way catalyst also needs to work as soon as possible.
Scientists have found that in HC and CO oxidation reactions, platinum group metals (platinum, palladium, belonging to a class of precious metals) have higher intrinsic activity (the ability to catalyze HC and CO oxidation) than cheaper base metals (such as copper, iron, and chromium). However, before leaded fuels were discarded, because the precious metal palladium was more likely to react with lead in fuels, the active center of the early three-way catalyst was the precious metal platinum. It wasn't until several countries began to ban the sale of leaded fuel that palladium, which was cheaper than platinum, gradually began to "rise" in ternary catalysts.
In a three-way catalytic converter, oxidation and reduction occur at the same time. (Image source: Platinum Metals Rev., 1972, 16, 74486)
In contrast, scientists spent more time looking for catalysts to reduce NOx. At first, scientists pinned their hopes on the platinum group metal ruthenium, because they found that ruthenium is the best of the metals in catalyzing NOx to nitrogen, but the oxide of ruthenium is extremely volatile, so how to stabilize the ruthenium catalyst has become one of the biggest problems. In the end, however, they chose rhodium, a platinum group metal, because rhodium's oxides are relatively stable, less volatile, and rhodium catalytic NOx reduction performance is higher than platinum and palladium.
Now, in gasoline vehicles, the three-way catalyst is basically based on palladium as the main component, and a small amount of rhodium is used for the conversion of NOx. Due to the different exhaust gas compositions, the three-way catalyst of diesel vehicles is mainly platinum and a small amount of rhodium.
Sometimes the temperature of the car exhaust can be as high as 1100 ° C, and the body is often bumpy during driving, so scientists have also found a honeycomb-shaped porous ceramic as a catalyst carrier to improve the thermal stability and mechanical strength of the active components. In order to distribute the platinum group metals evenly on the carrier, scientists are also constantly updating the technology to obtain honeycomb-like ceramics with more "nest chambers" to increase the specific surface area of the carrier. However, the inner surface area of the ceramic is still too small, so it is also necessary to coat the nest chamber with a large surface area of materials, such as alumina coating.
Three-way catalytic converters mainly include catalysts, carriers and coatings. (Image source: DOI: 10.1016/S0920-5861(02)00384-X)
At this point, the three parts of the platinum group metal (active component), the carrier and the coating constitute the basic ternary catalyst. If the catalyst is protected with a metal shell, and then add some small parts such as padding and sandwiches, a three-way catalytic converter is obtained.
Stealing the catalyst = stealing precious metals
We can see that for ternary catalysts, the most important components are platinum group metals, but their content in the earth's crust is very low, so the yield is also very low. According to statistics, in 2019, the global production of rhodium was less than 24 tons, and for comparison, the global production of gold belonging to the same precious metal reached 3300 tons.
Low yields naturally lead to high prices, and on December 27, 2021, the price per gram of rhodium, palladium, platinum and gold is about 4150, 553, 175 and 364 yuan, respectively – 1 gram of rhodium is more expensive than 11 grams of gold. No wonder thieves come in the middle of the night to pry away the ternary catalyst of the car chassis, which contains substances more expensive than gold, and the value of different models of ternary catalysts varies from thousands of yuan, and some even cost tens of thousands of yuan.
In addition, since the implementation of the National VI Standard (National Phase VI Motor Vehicle Pollutant Emission Standard) in July 2020, gasoline vehicles and diesel vehicles must be added with catalysts, so more precious metal catalysts are needed. If not supplied in a timely manner, the price of palladium and rhodium may continue to increase.
In 2018, the price of palladium surpassed platinum for the second time (the first time in history was around 2000), and has since far exceeded the price of platinum. At present, whether to replace palladium in gasoline vehicles with platinum again is still controversial, and more catalyst manufacturers are still in the wait-and-see stage, because the palladium-based catalyst technology in gasoline vehicles is very mature, and the re-development of platinum-based catalysts requires more capital investment.
Internal combustion engine vs electric motor
Not only is the cost of catalysts plaguing catalytic converter manufacturers, but the resurgence of the electric vehicle industry has also made these "big factories" feel threatened, because electric vehicles will no longer need three-way catalysts.
Recently, BASF issued a statement saying that it wants to separate its business related to ternary catalysts and exist as separate entities. Some analysts believe that this step is ultimately to sell and transfer this affiliated entity, that is, to plan to cut off this piece of meat that is no longer "fat".
Faraday electrolysis experiment. (Image source: SHEILA TERRY / SCIENCE PHOTO LIBRARY)
Johnson Matthey, a British company with three-way catalysts as its main source of income, has taken a completely different approach. They said they would continue to manufacture ternary catalysts, but would also expand their business related to green hydrogen and proton exchange membrane fuel cells.
It is not an easy task to completely replace the internal combustion engine. Now, some scientists are working to improve various technologies to improve the ability of catalysts to process car exhaust, and some scientists are working on the development of lithium-ion battery-powered, or fuel-cell-powered electric vehicles. For these electric cars, at least they don't have to worry about the catalytic converter being stolen.
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