Carbon monoxide in automobile exhausts

Determination of Carbon Monoxide in Automobile Exhaust by FT-IR Spectroscopy, /. Chem. Educ. 1988, 65, 820-823. 

An enzyme is a protein that speeds up a biochemical reaction without itself experiencing any overall change. In chemical language, such a compound is called a catalyst and is said to catalyze a reaction. Chemists employ a variety of compounds as laboratory catalysts, and many industrial chemical processes would be impracticably slow without catalysis. An automobile s catalytic converter makes use of a metal catalyst to accelerate conversion of toxic carbon monoxide in the exhaust to carbon dioxide. Similarly, our bodies biochemical machinery effects thousands of different reactions that would not proceed without enzymatic catalysis. Some enzymes are exquisitely specific, catalyzing only one particular reaction of a single compound. Many others have much less exacting requirements and consequently exhibit broader effects. Specific or nonspecific, enzymes can make reactions go many millions of times faster than they would without catalysis. 

Carbon monoxide in auto exhaust is the result of incomplete combusting of gasoline in the engine. The removal of this major pollutant from auto emissions by conversion to CO2 via this reaction is one of the primary functions of catalytic converters in automobiles.)... 

Standing on a street comer in any major city exposes a person to above-normal concentrations of carbon monoxide from automobile exhaust. Carbon monoxide also reacts with hemoglobin. The following reaction takes place in the capillaries of the lung. 

For example, take six samples of carbon monoxide from the exhaust of an idling automobile and obtain the CO percentages as shown in Table 32-1. The sample mean is... 

Carbon monoxide is found in varying concentrations in unventilated and confined spaces resulting from partial oxidation of carbonaceous matter. Burning wood, paper, kerosene, or other organic materials in inadequate air can produce this gas. It also is found in automobile exhaust and tobacco smoke emissions. 

Concentrations of pollutants in ambient air are normally sufficiently small that ppm is the largest unit in use. However, pollutant concentrations in stacks or exhaust trains prior to mixing and dilution with air are much higher, and percent (i.e., parts per hundred) is sometimes used in this case. For example, carbon monoxide concentrations in automobile exhaust are measured in percentages, reflecting the numbers of CO molecules (or volumes) per 100 molecules (or volumes) of exhaust. 

Trace quantities of carbon monoxide in the environment are considered normal (WHO 1999). Plants can both metabolize and produce this gas. Carbon monoxide is also produced by incomplete combustion of carbon-containing materials (ACGIH 1996), and automobile exhaust is a major source of carbon... 

Another typical example of the use of the katherometer in the analysis of gas mixtures is afforded by the separation of the components of the Scott gas mixture 237. This is a standard mixture which consists of a mixture of oxygen, carbon monoxide, methane, and carbon dioxide in an excess of nitrogen. The sample is a typical mixture of gases that are liable to be found in automobile exhaust fumes and is used to test emission analyzing equipment and gas analyses apparatus. An example of such a separation carried out on a proprietary packing at 25°C is shown in figure 5. 

Catalysis is widely used in the chemical industry, particularly in the making of gasoline and other petrochemicals. Catalysts save enormous amounts of energy. As you probably know, carbon monoxide is a poisonous gas that is found in automobile exhaust. The following oxidation reaction could remove the health hazard, but this reaction is very slow. 

It is desirable to carry out these reactions in automobile exhaust systems. Carbon monoxide is very poisonous. The latter reaction is so slow that a mixture of CO and O2 gas at the exhaust temperature would remain unreacted for thousands of years in the absence of a catalyst Yet the addition of only a small amount of a solid, finely divided transition metal catalyst promotes the production of up to a mole of CO2 per minute. Because this reaction is a very simple but important one, it has been studied extensively by surface chemists. It is one of the best understood heterogeneously catalyzed reactions. The major features of the catalytic process are shown in Figure 16-18. 

Catalytic converters in automobile exhaust systems were developed to remove some of the carbon monoxide and unburned hydrocarbons from automobile exhaust. A catalyst is any substance that speeds a chemical reaction without being permanendy altered itself Some of the transition metals, such as platinum, palladium, iridium, and rhodium,... 

Transition metal carbides (mainly of W and Mo) have been shown to be effective catalysts in some chemical reactions that are usually catalyzed by noble metals such as Pt and Pd (ref.1). Their remarkable physical properties added to lower cost and better availability could make them good candidates for substitute materials to noble metals in automobile exhaust catalysis. Hence, for this purpose, we have prepared several catalysts of tungsten carbide and W,Mo mixed carbides supported on y alumina with different Mo/W atom ratios. The surface composition has been studied by XPS while the quantitative determination of catalytic sites has been obtained by selective chemisorption of hydrogen and of carbon monoxide. The catalytic performances of these catalysts have been evaluated in the simultaneous conversion of carbon monoxide, nitric oxide and propane from a synthetic exhaust gas. 

Heterogeneous catalysis is also utilized in the catalytic converters in automobile exhaust systems. The exhaust gases, containing compounds such as nitric oxide, carbon monoxide, and unburned hydrocarbons, are passed through a converter containing beads of solid catalyst (see Fig. 12.16). The catalyst promotes the conversion of carbon monoxide to carbon dioxide, hydrocarbons to carbon dioxide and water, and nitric oxide to nitrogen gas to lessen the environmental impact of the exhaust gases. However, this beneficial catalysis can, unfortunately, be accompanied by the unwanted catalysis of the oxidation of SO2 to SO3, which reacts with the moisture present to form sulfuric acid. 

Carbon Monoxide A colorless, tasteless gas, CO. Highly flammable (liquid autoignition point, 609°C) and toxic. Found in automobile exhaust gases and is a major air pollutant. Manufactured from coke by action of oxygen and carbon dioxide or steam. Used in organic S5mthesis, synthetic fuels, and metallurgy. 

Carbon monoxide (CO) and nitric oxide (NO) are t ARlS polluting gases contained in automobile exhaust. 

Toxic carbon monoxide in exhaust fumes (eq. 2.5), soot emitted copiously from trucks with diesel engines (eq. 2.6), smog resulting in part from aldehydes (eq. 2.7), and acid buildup in lubricating oils (eq. 2.8) are all prices we pay for being a motorized society However, incomplete hydrocarbon combustion is occasionally useful, as in the manufacture of carbon blacks (eq. 2.6) used for automobile tires, and lampblack, a pigment used in ink. 

Look closely at your symbols for aluminum and copper in Example 5.5. If you wrote AL or CU, the symbol is wrong. The letters are right, but the symbol is not. Whenever a chemical symbol has two letters, the first letter is always capitalized, but the second letter is always written in lowercase, or as a small letter. You can enjoy a long and happy life with a pile of Co in your house, but CO is a potentially serious problem in homes. Co is the metal cobalt, which is sometimes used in steel and pottery, among other things. CO is the deadly gas carbon monoxide, which is present in automobile exhaust and tobacco smoke. Carbon monoxide poisoning is the number one cause of accidental poisoning deaths in the world. 

Since the internal combustion engine is the primary source of localized pollutant carbon monoxide emissions, control measures have been concentrated on automobiles and have been very successful in reducing carbon monoxide emissions. Carbon monoxide emissions may be lowered by employing a leaner air-fuel mixture, that is, one in which the mass ratio of air to fuel is relatively high. At air-fuel (mass mass) ratios exceeding approximately 16 1, an internal combustion engine emits virtually no carbon monoxide. Modern automobiles use catalytic exhaust reactors and precise computerized control of engine operation to cut down on carbon monoxide emissions. 

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