Properly operating fuel-burning engines produce exhaust gases containing only nitrogen, carbon dioxide and water as emissions; however, incomplete combustion may produce harmful pollutants such as carbon monoxide, unburned hydrocarbons or nitric oxide emissions.
A catalytic converter is an exhaust emission control device that utilizes redox reactions to remove harmful contaminants from an exhaust stream. As catalyst material, precious metals like platinum, palladium and rhodium are utilized.
The most sophisticated kind of catalytic converters are three-way converters, and they may significantly improve the quality of the air we breathe. Three-way catalytic converters assist in lowering levels of dangerous pollutants, which helps to lessen smog, acid rain, and other environmental issues. Discover the difference a three-way catalytic converter can make for your vehicle and the environment.
Converts Carbon Monoxide to Carbon Dioxide
Three-way catalytic converters perform two key tasks, converting carbon monoxide to carbon dioxide through chemical reactions involving platinum and palladium; secondly they reduce Nitrogen Oxides back down to nitrogen and oxygen by using chemical reactions between nickel and rhodium as catalysts.
Three-way catalysts work best when engine operations occur within a narrow band of air/fuel ratios close to stoichiometry. If not used within this range, exhaust gasses would become rich with excess fuel and lack oxygen, rendering this catalyst ineffective in reducing NOx.
To ensure proper operation of a three-way catalyst, an O2 sensor coupled with a closed-loop feedback fuel injection system are required for proper functioning. This combination allows the sensor to regulate engine lean/rich conditions, keeping three-way catalyst operating at its highest effectiveness state.
Converts Hydrocarbons to Water
Three Way Catalytic Converters (TWCs) are essential components for vehicles meeting modern emission standards, converting harmful gasses such as hydrocarbons and nitrogen oxides into less harmful ones like carbon dioxide and water vapor while simultaneously decreasing concentrations of hydrocarbons and nitrogen oxides in exhaust.
TWC utilizes an oxidation catalyst that converts carbon monoxide and unburnt fuel to carbon dioxide and water for safe disposal, while its reduction catalyst transforms nitric oxide into oxygen and nitrogen gases for further use in its products.
Reducing catalysts require higher working temperatures than their oxidation counterparts, leading to their placement closer to engines in early automobiles. Nowadays, TWCs are typically located under vehicles near their exhaust outlets in order to achieve optimal working temperatures and maximize productivity.
Due to being covered in precious metals, TWCs are vulnerable to certain chemicals and substances that interfere with conversion processes; such as hydrogen sulfide gas forming in them which produces an unpleasant odor while decreasing efficiency.
Converts Nitrogen Oxides to Nitrogen
Three-way catalytic converters improve upon the two-way oxidation catalyst found on vehicles before 1981 by adding an anti-reduction element, helping reduce emission of nitrogen oxides that contribute to acid rain and global climate change.
Three-way catalytic converters feature reduction reactions that allow them to complete a process that two way catalytic converters cannot, including turning hazardous gases such as nitric oxide and nitrogen dioxide into non-hazardous materials such as carbon monoxide and water.
Though a three-way catalytic converter can efficiently carry out these redox reactions, it may still be susceptible to interference from chemicals and substances which impede its effective operation. For instance, oxides of sulfur and nitrogen produced during diesel engine combustion may poison its catalyst and prevent desired reactions from taking place. Furthermore, certain maneuvers can enrich exhaust mixture beyond what a three-way catalytic converter can supply with oxygen; leading to unwanted reactions occurring due to excess of air entering through exhaust pipework.
Converts Particulate Matter to Particulate Matter
Automobiles contribute significantly to air pollution through toxic gases and particulate matter (PM10, PM2.5 and PM0.1). Cars are one of the primary sources of these emissions in urban environments. A catalytic converter helps lower emissions by catalyzing chemical reactions.
A catalyst consists of a honeycomb structure lined with small tubes coated in precious metal (Gold, Platinum or Rhodium). As exhaust gas passes through these channels, this metal encourages chemical processes that help convert harmful gases into less-harmful ones.
The three-way catalytic converter effectively reduces carbon monoxide, hydrocarbons, and nitrogen oxide emissions that contribute to air pollution caused by cars. Auto experts also utilize urea injection – using liquid ammonium forms of ammonium – as another means to decrease NOx production from engines – predominantly those powered by diesel as their stoichiometric points tend to be much leaner than gasoline engines.
