三元催化器的作用：凈化尾氣
The function of a three-way catalyst: purifying exhaust gas
三元催化器，是安裝在汽車排氣系統(tǒng)中最重要的機外凈化裝置，它可將汽車尾氣排出的CO、HC和NOx等有害氣體通過氧化和還原作用轉變?yōu)闊o害的二氧化碳、水和氮氣。由于這種催化器可同時將廢氣中的三種主要有害物質轉化為無害物質。隨著環(huán)境保護要求的日益苛刻，越來越多的汽車安裝了廢氣催化轉化器以及氧傳感器裝置。它安裝在發(fā)動機排氣管中，通過氧化還原反應，二氧化碳和氮氣，故又稱之為三元(效)催化轉化器。
The three-way catalyst is the most important external purification device installed in the automobile exhaust system. It can convert harmful gases such as CO, HC, and NOx emitted from automobile exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction. Due to its ability to simultaneously convert three major harmful substances in exhaust gas into harmless substances. With increasingly stringent environmental protection requirements, more and more cars are equipped with exhaust catalytic converters and oxygen sensor devices. It is installed in the engine exhaust pipe and undergoes oxidation-reduction reactions to produce carbon dioxide and nitrogen, hence it is also known as a three-way catalytic converter.
三元催化器的工作原理：當高溫的汽車尾氣通過凈化裝置時，三元催化器中的凈化劑將增強CO、HC和NOx三種氣體的活性，促使其進行一定的氧化-還原化學反應，其中CO在高溫下氧化成為無色、無毒的二氧化碳氣體；HC化合物在高溫下氧化成水(H20)和二氧化碳；NOx還原成氮氣和氧氣。所以，其作用就是讓三種有害氣體變成無害氣體，使汽車尾氣得以凈化。
The working principle of a three-way catalyst: When high-temperature automobile exhaust passes through the purification device, the purifying agent in the three-way catalyst will enhance the activity of CO, HC, and NOx gases, promoting them to undergo certain oxidation-reduction chemical reactions. Among them, CO is oxidized to colorless and non-toxic carbon dioxide gas at high temperature; HC compounds oxidize into water (H2O) and carbon dioxide at high temperatures; NOx is reduced to nitrogen and oxygen. So, its function is to turn three harmful gases into harmless gases, purifying car exhaust.
三元催化器失效的原因
Reasons for the failure of three-way catalytic converters
1、高溫失活：三元催化器長期在高溫條件下，會造成高溫失活，三元催化器產生高溫的原因是：
1. High temperature deactivation: Long term exposure to high temperature conditions can cause high temperature deactivation of the three-way catalyst. The reason for the high temperature of the three-way catalyst is:
（A）發(fā)動機失火過使未燃混合氣在催化器中燃燒發(fā)生劇烈氧化放熱反應。
(A) The engine misfires, causing the unburned mixture to undergo intense oxidation and heat release reactions during combustion in the catalyst.
（B）汽車連續(xù)高速大負荷運行。
(B) The car runs continuously at high speed and high load.
（C）汽車突然制動、減速。
(C) The car suddenly brakes or decelerates.
發(fā)動機排氣溫度的變化范圍很大，怠速時一般為300~400℃，低速、中速常用工況行駛為400~600℃，高速全負荷行駛時為900℃。如果三元催化劑長期暴露在800℃以上的高溫環(huán)境下，催化劑的活性組分鉑、鈀和銠貴金屬等組分易揮發(fā)，其涂層易剝落，其晶粒及助催化劑氧化鈰的晶粒會明顯增大，而且載體氧化鋁也會發(fā)生相變，會從比表面較大的γ型轉變比表面較小的∂型，從而加劇了貴金屬活性組分和助劑氧化鈰晶粒的長大燒結和聚集，使該催化劑的比表面急劇下降，而使催化劑失活。高溫還會引起氧化鈰助劑等儲氧能力降低，在800℃時催化劑吸氧能力迅速降低，從而使催化劑的活性大大下降。
The range of engine exhaust temperature variation is large, generally ranging from 300~400 ℃ at idle, 400~600 ℃ at low and medium speeds, and 900 ℃ at full load at high speeds. If the ternary catalyst is exposed to a high temperature environment above 800 ℃ for a long time, the active components of the catalyst, such as platinum, palladium, and rhodium precious metals, are prone to volatilization, and their coatings are prone to peeling off. The grain size of the catalyst and the grain size of the co catalyst cerium oxide will significantly increase, and the carrier aluminum oxide will also undergo phase change, transforming from the larger surface area of the gamma type to the smaller surface area of the ∂ type, thereby exacerbating the growth, sintering, and aggregation of precious metal active components and co catalyst cerium oxide grains, causing a sharp decrease in the specific surface area of the catalyst and catalyst deactivation. High temperature can also cause a decrease in the oxygen storage capacity of cerium oxide additives, and the oxygen absorption capacity of the catalyst rapidly decreases at 800 ℃, resulting in a significant decrease in the activity of the catalyst.
2、化學中毒：燃油和潤滑油中的硫、磷、抗爆劑中的錳、鉛、燃油不完全燃燒產生的一氧化碳都會造成三元催化劑中毒失效，毒物主要是吸附在催化劑活性表面上，并形成一種化學吸附絡合物，其中鉛中毒往往是不可逆的，催化劑在含鉛氣氛中工作幾十小時就會完全喪失活性，而對硫、磷、一氧化碳中毒，催化劑的活性則在一定條件下可以得到恢復。
2. Chemical poisoning: Sulfur and phosphorus in fuel and lubricants, manganese and lead in anti knock agents, and carbon monoxide produced by incomplete combustion of fuel can all cause poisoning and failure of three-way catalysts. Toxic substances mainly adsorb on the active surface of the catalyst and form a chemical adsorption complex. Lead poisoning is often irreversible, and the catalyst will completely lose its activity after working in a lead containing atmosphere for tens of hours. However, for sulfur, phosphorus, and carbon monoxide poisoning, the activity of the catalyst can be restored under certain conditions.
3、積碳失活：因積炭覆蓋在三元催化劑和涂層表面而造成三元催化器失效為積炭失活，覆蓋在涂層表面的積碳往往是一種含有碳、氫、硫、氮、氧、重金屬等多種元素的混合物，積炭失活是目前導致三元催化器失效的主要原因之一。
3. Carbon deposition deactivation: The failure of a three-way catalyst caused by carbon deposition covering the surface of the catalyst and coating is known as carbon deposition deactivation. The carbon deposition covering the surface of the coating is often a mixture containing various elements such as carbon, hydrogen, sulfur, nitrogen, oxygen, heavy metals, etc. Carbon deposition deactivation is currently one of the main reasons for the failure of three-way catalysts.
4、堵塞失效：三元催化器因堵塞失效造成發(fā)動機工作不正常是目前環(huán)保發(fā)動機很普遍的問題，三元催化器堵塞常見形式有：
4. Blockage failure: The abnormal operation of the engine caused by blockage failure of the three-way catalyst is a common problem in environmentally friendly engines. Common forms of blockage of the three-way catalyst include:
（A）使用乙醇汽油膠質積碳燒結堵塞。
(A) Use ethanol gasoline gum to deposit carbon and sinter for blockage.
（B）硫磷化學絡合物燒結堵塞。
(B) Sulfur phosphorus chemical complex sintering blockage.
（C）鉛錳金屬沉積物燒結堵塞。
(C) Lead manganese metal deposits are sintered and blocked.
（D）發(fā)動機失火造成陶瓷載體燒溶堵塞。
(D) Engine misfire causes ceramic carrier melting and blockage．
（E）發(fā)動機失火造成三元催化器陶瓷載體和金屬外殼之間的密封層部分高溫老化，成為粉末堵塞后半部陶瓷載體。
(E) The engine misfire caused high temperature aging of the sealing layer between the ceramic carrier and the metal shell of the three-way catalyst, resulting in powder blockage of the rear half of the ceramic carrier.