臺灣博碩士論文加值系統

摘 要在都會地區，主要的空氣污染源來自汽、機車排放出來的廢氣
，而碳氫化合物燃燒不完全是主要的原因。醛類即是廢氣中主要成分之一
它們是一種無色、透明的化合物，在常溫狀態下具有揮發性，主要直接對
眼睛、皮膚及鼻腔黏膜的刺激與上呼吸系統之危害，並有致癌的可能。觸
媒轉換器是車輛常用的廢氣處理裝置，藉由觸媒的催化作用可降低工作溫
度，並且增加去除效率。溫度是觸媒轉換器產生轉換作用的主要因素，隨
著溫度升高，轉換效率亦提昇。但是溫度過高時會使觸媒轉換器產生塗膜
現象，使表面積減少，而降低轉換效率。鉛、硫等元素亦會使觸媒轉換器
產生毒害作用，失去轉換的能力。本實驗使用1500cc的馬自達引擎及鉑觸
媒轉換器，分別加入九五及九二無鉛汽油，以不同的轉速、節氣門開啟率
，待其運轉穩定後在有無觸媒轉換器的情況下個別採其尾氣進行分析。其
醛類化合物的組成以甲醛、乙醛、反丁烯醛及苯甲醛為主。在無觸媒轉換
器時排出之廢氣以九五無鉛汽油的總濃度稍高於九二無鉛汽油的總濃度在
裝上觸媒轉換器後排出之廢氣亦以九五無鉛汽油的總濃度稍高於九二無鉛
汽油，但二者總濃度均非常低裝上觸媒轉換器前後的醛類排放濃度有非常
明顯的差異，由研究結果顯示不論是九五無鉛汽油或是九二無鉛汽油的轉
換效率均高達80%以上，表示觸媒轉換器對醛類化合物有很好的去除能力
在冷啟動方面二種油品所得到的結果發現觸媒轉換器的效率極低且廢氣濃
度更高於穩態運轉時的濃度。以排放濃度的觀點而言九二無鉛汽油產生的
排放量排放濃度等各項結果均較九五無鉛汽油，表示本引擎使用九二無鉛
汽油的燃燒效果較佳

Effects of Engine Speed and the Catalytic Converter on
Aldehydes Emission in Automobile ExhaustAbstractAldehydes are
among many known toxic compounds found in the exhaust emission
from vehicles due to imcomplete combustion of fuels. They often
cause uncomfortable irritation to the skin, eyes and mucous
membranes. Some aldehydes are even known to be potential
carcinogens. This study was conducted to understand the
composition and distribution of aldehydes in the exhaust, and
the conversion efficiency of the catalytic converter on
aldehydes. A 1500 c.c. Mazda engine with a dynamometer was used
with and without a honey comb-type platinum-coated catalytic
converter. Two fuels, the 95 lead-free gasoline and 92 lead-
free gasoline, were used. The tests were done on four pre-
selected engine speeds. The exhaust gas samples were collected
at the tail pipe into separate Tedlar bags, pumped though a
2,4-dinitrophenyl-hydrazine coated cartridge to convert into
stable hydrazine derivatives. The cartridges were then eluted
with acetonitrile and the eluanThe results show that the
conversion efficiency increased with increased temperature in
the catalytic converter, which was caused by the increase in
engine speed. In all 92 lead-free gasolin runs the total
conversion efficiency were all beyond 90%, while in other runs
total conversion efficiency were all also beyond 80%. Overall
speaking, a catalytic converter is of great help in cutting down
aldehydes emission in the vehicular exhaust. In the cold start
runs, concentration of some aldehydes, especially the toxic
aldehydes such as acetaldehyde, crotonaldehyde, and acrolin,
were all found to be higher than the corresponding steady-state
runs when either 95 lead-free gasoline or 92 lead-free gasoline
was used, Also, during cold start, due to the still low
temperature, the catalytic converter performed very pooly,
causing emission of much higher level of aldehydes into the
atmosphere.In terms of emission concentrations of aldehydes
alone, the studied engine running at 2200 rpm emits the least
aldehydes and thus is the most environmentally friendly speed.