What is crude oil?
Crude oil is a naturally-occurring substance found trapped in certain rocks below the earth's crust. It is a dark, sticky liquid which, scientifically speaking, is classed as a hydrocarbon. This means, it is a compound containing only hydrogen and carbon. Crude oil is highly flammable and can be burned to create energy. Along with its sister hydrocarbon, natural gas, crude oil makes an excellent fuel.
Hydrocarbons
Hydrocarbons are organic molecules that contain only carbon (C) and hydrogen (H).
Examples of hydrocarbons:
* Methane
* Propane
* Benzene
* Etc......
Unsaturated & Saturated Hydrocarbons
. Saturated Hydrocarbons
Saturated hydrocarbons contain only single carbon-carbon bonds, and therefore contain the greatest possible number of hydrogen atoms for their number of carbon atoms.
E.g.
* Alkanes
* Branched Alkanes
2. Unsaturated Hydrocarbons
Unsaturated hydrocarbons contain double and triple carbon-carbon bonds, and therefore do not contain the greatest possible number of hydrogen atoms for their number of carbon atoms.
E.g.
* Benzene
* Alkenes
* Alkynes
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If there is not enough oxygen present to completely burn the fuel to carbon dioxide and water other products may form. The most common partially burned products are likely to be carbon C (soot) and deadly carbon monoxide CO. It would appear that the hydrogen in the fuel molecules is more easily burned and usually forms water.
eg CH4(g) + O2(g) => C(s) + 2H2O(l) or 2CH4(g) + 3O2(g) => 2CO(g) + 4H2O(l)
Therefore it is extremely important that any combustion system is as efficient as possible eg gas heaters, furnaces etc must all have excellent ventilation for complete combustion to harmless water and carbon dioxide. Carbon monoxide is colourless and odourless and even low concentrations in the air can be fatal. Carbon monoxide is unfortunately emitted by all car exhausts, though catalytic converters help reduce this by converting nitrogen monoxide (another pollutant) and carbon monoxide into harmless nitrogen and carbon dioxide.
2NO(g) + 2CO(g) => N2(s) + 2CO2(l)
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The Problem of Incomplete Combustion
Fossil fuels are a complex mixture of carbon and hydrogen-containing molecules referred to as hydrocarbons (HC). In addition to the pure hydrocarbon molecules, fuels also have a small fraction of molecules containing nitrogen, sulphur and other elements including many metals such as vanadium. Poor quality fuels, such as coals, are comprised of very large, mostly carbon containing molecules. The amount of hydrogen in the fuel increases as the size of the molecules decrease and the quality of the fuel increases. Higher quality fuels which have more hydrogen and smaller molecules burn faster and more completely. When fossil fuels burn, oxygen is reacting with the hydrocarbon molecules to produce carbon dioxide (CO2), water (H2O), oxides of the trace elements (Nox, Sox, Vox, etc. where x is 0 or a small number) and heat. How completely the hydrocarbons burn depends upon three basic factors:
* The rate at which the molecules burn.
(This rate is a function of how large the molecules are.)
* How much oxygen is present around the fuel molecules
* The length of time that the fuel molecules spend in the fireball
Some of the harmful waste products and effects are:
* Black Smoke problems.
* Slagging, fouling, and corrosion of the car.
Carbon particles (soot), and condensed tar, result from the incomplete combustion of fuels. When present in sufficient particle size and quantity, soot in ...
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* The rate at which the molecules burn.
(This rate is a function of how large the molecules are.)
* How much oxygen is present around the fuel molecules
* The length of time that the fuel molecules spend in the fireball
Some of the harmful waste products and effects are:
* Black Smoke problems.
* Slagging, fouling, and corrosion of the car.
Carbon particles (soot), and condensed tar, result from the incomplete combustion of fuels. When present in sufficient particle size and quantity, soot in exhaust gases constitutes a black smoke. Although soot is not the most abundant pollutant, it may be one of the most hazardous since soot particles are the proper size to be ingested deep into the lungs.
In addition, the polycyclic aromatic hydrocarbons (PAH's) which are absorbed on soot can promote skin cancer in humans, as many PAH's are known to be carcinogenic. (A cancer-causing substance or agent.)
Research also indicates that soot adsorbs sulphuric acid formed during combustion and contributes to its formation via reactions on the carbon surface. The adsorbed H2SO4 can be as much as 20% by weight of the carbon retained in the boiler. If allowed to escape into the atmosphere, it can cause acid smut fallout and boiler cold-temperature corrosion.
What is a catalytic converter and how does it work?
A catalytic converter is a device that uses a catalyst to convert three harmful compounds in car exhaust into harmless compounds.
The three harmful compounds are:
* Hydrocarbons (in the form of unburned gasoline)
* Carbon monoxide (formed by the combustion of gasoline)
* Nitrogen oxides (created when the heat in the engine forces nitrogen in the air to combine with oxygen)
Carbon monoxide is a poison for any air-breathing animal. Nitrogen oxides lead to smog and acid rain, and hydrocarbons produce smog.
In a catalytic converter, the catalyst (in the form of platinum and palladium) is coated onto a ceramic honeycomb or ceramic beads that are housed in a muffler-like package attached to the exhaust pipe. The catalyst helps to convert carbon monoxide into carbon dioxide. It converts the hydrocarbons into carbon dioxide and water. It also converts the nitrogen oxides back into nitrogen and oxygen.
I have heard that carbon monoxide is extremely poisonous. Can you explain why?
Every poison has a particular trait that causes it to be poisonous. In the case of carbon monoxide, the trait has to do with haemoglobin in the blood.
Haemoglobin is made up of complex proteins that bind to iron atoms. The structure of the protein and its iron atom causes oxygen to bind to the iron atom very loosely. When blood passes through the lungs, the iron atoms in the haemoglobin bind to oxygen atoms. When the blood flows into areas of the body that are lacking in oxygen, the iron atoms release their oxygen. The difference in oxygen pressure in the lungs and in the parts of the body needing oxygen is very slight. The haemoglobin is very finely tuned to absorb and release oxygen at just the right times.
Carbon monoxide, on the other hand, binds very strongly to the iron in haemoglobin. Once carbon monoxide attaches, it is very difficult to release. So if you breathe in carbon monoxide, it sticks to your haemoglobin and takes up all of the oxygen binding sites. Eventually, your blood loses all of its ability to transport oxygen, and you suffocate.
Because carbon monoxide binds to haemoglobin so strongly, you can be poisoned by carbon monoxide even at very low concentrations if you are exposed for a long period of time. Concentrations as low as 20 or 30 parts per million (PPM) can be harmful if you are exposed for several hours. Exposure at 2,000 PPM for one hour will cause unconsciousness.
Many common devices produce carbon monoxide, including cars, gas appliances, wood stoves and cigarettes.
Solutions to Air Pollution
A catalytic converter is a pollution-control device placed in the exhaust system of an automobile. It was in the 1980's that the United States passed a federal law that required all new automobiles to have catalytic converters. A catalytic converter takes the carbon monoxide and hydrocarbons that are given off as waste from the combustion of gasoline in the car's engine and converts them into water and carbon dioxide gas. Since water and carbon dioxide cycle through the environment they are safer than carbon monoxide and hydrocarbons, the converters also convert nitrous oxides into nitrogen gas, which naturally makes up 78% of air.
A catalytic converter is coated with platinum and rhodium (both catalysts), all spread out over a honey comb structure for a greater surface area. The exhaust gases pass through the converter where the catalysts speed up the oxidation reactions to turn the harmful gases into less harmful substances.
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Although the catalytic converter may seem like a good idea and could stop most harmful pollutants, a study of the actual effects of the catalytic converter have been shown to be -ve as well +ve.
The study below shows a New York investigator's findings in the effect of a catalytic converter.
Against use of Catalytic converter
Study by Matthew L. Wald, The New York Times, May 29, 1998
The catalytic converter, an invention that has sharply reduced smog from cars, has now become a significant and growing cause of global warming, according to the Environmental Protection Agency (also known as EPA).
Hailed as a miracle by Detroit automakers even today, catalytic converters have been reducing smog for 20 years. The converters break down compounds of nitrogen and oxygen from car exhaust that can combine with hydrocarbons, also from cars, and are cooked by sunlight into smog.
But researchers have suspected for years that the converters sometimes rearrange the nitrogen-oxygen compounds to form nitrous oxide, known as laughing gas. And nitrous oxide is a potent greenhouse gas, more than 300 times more potent than carbon dioxide, the most common of the gases, that is warming the atmosphere, according to experts.
This spring, the EPA published a study estimating that nitrous oxide now comprises about 7.2 percent of the gases that cause global warming. Cars and trucks, most fitted with catalytic converters, produce nearly half of that nitrous oxide, the study said. (Other sources of nitrous oxide include everything from nitrogen-based fertiliser to manure from farm animals.)
The EPA study also showed that nitrous oxide is one of a few gases for which emissions are increasing rapidly. Collectively known as greenhouse gases, they trap heat in the earth's atmosphere.
The increase in nitrous oxide, the study notes stems from the growth in the number of miles travelled by cars that have catalytic converters. And the problem has worsened as improvements in catalytic converters, changes that have eliminated more of the nitrogen-oxygen compounds that cause smog, have conversely produced more nitrous oxide.
Wylie J. Barbour, an EPA official who worked on the recently published inventory, said that the problem created by the converter is classic. "You've got people trying to solve one problem, and as is not uncommon, they've created another."
Nitrous oxide, or N2O, is not regulated because the Clean Air Act was written in 1970 to control smog, not global warming. And no regulations exist to control gases that are believed to cause global warming.
The United States and the other industrialised nations agreed in Kyoto, Japan, last December to lower emissions of greenhouse gases to 5 percent below 1990 levels, over the next 10 to 15 years, but the agreement has not been approved by the Senate, and no implementing rules have been written.
"This hadn't really been on people's radar screen until climate change started becoming an issue," said one EPA official involved in reducing pollution from cars, which asked not to be identified by name.
The EPA has not proposed a solution at this point, and is seeking public comment on its study. Auto industry experts say they could solve the problem by tinkering with the catalytic converter, but some environmentalists suggest that the growing production of nitrous oxide is yet another reason to move away from gasoline-powered cars. The EPA's study estimated that nitrous oxide may represent about one-sixth of the global warming effect that results from gasoline use.
"It's like, clean is not green," said Sheila Lynch, executive director of the Northeast Alternative Vehicle Coalition, a public-private partnership that encourages non-traditional power sources.
Another expert, Christopher S. Weaver, an engineering consultant who wrote a study on the subject for the environmental agency, said, "We haven't cared enough to establish standards."
Precisely how much nitrous oxide the converters produce remains an issue. A report used by the EPA in preparing its greenhouse gas study, calculated that a car with a fuel economy of about 19 miles a gallon would produce .27 grams of nitrous oxide per mile. That represents an amount that is about one-third the limit of emissions for nitrogen oxide, the chemicals causing smog.
Steven H. Cadle, a research scientist at General Motors, said, "it's a huge number." In contrast, an older car without a catalytic converter produces much larger amounts of nitrogen oxides, but only about a tenth as much nitrous oxide, the greenhouse gas.
The EPA calculated that production of nitrous oxide from vehicles rose by nearly 50 percent between 1990 and 1996 as older cars without converters have neared extinction. Using a standard unit of measure for global warming gases, millions of metric tons of carbon equivalent, nitrous oxide emissions rose to 54.7 million tons from 36.7 million during those years, the study said.
The contradictory impact of the converter has not been lost on environmental officials or industry experts, who continue to debate not only the extent of the growing problem as well as how to reduce the emissions in future years.
Ned Sullivan, the head of the Maine Department of Environmental Protection, said the converter problem requires a "comprehensive" response. "This specific issue fits into a broader context that our regulatory system has tended to deal with pollutants on an individual, rather than a comprehensive, basis," he said.
He and others favour moving away from today's typical car design, a big gasoline engine driving the wheels, to electric cars. Maine would like electric cars. Another solution is hybrid cars, which use small, efficient engines running on gasoline to help turn the wheels and to charge batteries for electric motors that also run the wheels. Those have much higher fuel economy, and thus lower greenhouse gas emissions.
Car industry experts, however, favour less drastic changes. They propose cutting nitrous oxide production by adjusting catalytic converters in future models. They suspect that the gas is produced when the converter is warming up, and believe the converters could be redesigned to reach optimum temperature faster. That would also help them destroy other pollutants better.
Weaver said that measurements on more kinds of cars and light trucks would be needed to be certain about the size of the problem. But Weaver said, "It is quite clear that you produce nitrous oxide in a catalyst, in some circumstances."
At the Union of Concerned Scientists, an environmental group, an expert on transportation pollution, Roland Hwang, said, "We can't be pushing forward trying to reduce smog while making the global warming problem worse; we can't have programs that undercut each other." He said this was evidence that the transportation system would have to use something besides gasoline.
Cadle, of General Motors would not go that far. But, he said, "You have to be holistic and try and look at everything, which is obviously difficult."
CH4(g) + O2(g) => C(s) + 2H2O(l)
Or
2CH4(g) + 3O2(g) => 2CO(g) + 4H2O(l)