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Thursday, March 10, 2005

chem: ethanol assignment

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Ethanol Assignment

1. At present ethanol is produced commercially from ethene which is derived from petroleum.
i) Describe how ethanol is produced commercially from ethene.
Ethanol is commercially prepared by the sulfuric-acid-catalysed vapour phase addition of water to ethene at 280°C and 30Mpa. The reaction occurs in two steps. First the sulfuric acid adds onto the ethene to produce ethyl hydrogen sulfate. Then the ethyl hydrogen sulfate reacts with water, generating ethanol, and sulfuric acid is reformed.
Step 1: C2H4(g) + H2SO4(g) C2H5HSO4(g)
Step 2: C2H5HSO4(g) + H2O(g) C2H5OH(g) + H2SO4(g)
Overall addition: C2H4(g) + H2O(g) CH3CH2OH(g) DH = -45kJ molL-1
ethene water ethanol

ii) Write a structural equation for the production of ethanol including the catalyst

2. Ethanol can be readily converted to ethene.
i) Write an equation for this reaction.
CH3CH2OH(l) C2H4(g) + H2O(l)

3. Ethanol can also be produced without using petroleum products.
i) Describe how ethanol can be produced from sugars.
Yeast is used to convert the sugar into ethanol. The yeast derives energy from the respiration of glucose and ethanol and carbon dioxide are released as wastes. Pure ethanol is then distilled.

ii) Write an equation for the reaction.
C6H12O6(aq) 2C2H6O(l) + 2CO2(g)
sugar ethanol carbon dioxide gas

iii) Name the process in (i)
This process is called fermentation.

4. i) Describe how ethanol can be produced from sugar waste and corn.
This can be done through two processes:
- dry milling. The corn feedstock is ground and cooked in water to produce corn mash. Enzymes such as amyloglucosidase are added and the starch is hydrolysed to form glucose. Yeast fermentation for up to 72 hours produces ethanol. It is then distilled.
- wet milling. The corn is soaked in a mixture of water and sulfur dioxide for 2 days to loosen the fibrous hull. Corn oil is extracted from the kernel, then the starch from the endosperm is extracted and fermented as in the dry milling process.

ii) When and why can ethanol be considered to be a renewable energy resource?
When the process of fermentation is used to produce ethanol, renewable resources are being used in the form of plants that can regrow. As opposed to making ethanol from petrochemicals, a non-renewable resource, using plants is renewable, in that all their energy comes from the sun and photosynthesis.

iii) Where in Australia is ethanol produced from sugar cane or other crops?
All plant material contains glucose and other simple sugars, but they may be locked away in long chains as cellulose and other material. They have to first be released (which can be inefficient), and the cheapest source of plant material depends on the region. In some places roots such as cassava, tubers such as potato and grains such as corn are used. Manildra at Nowra, New South Wales has been producing 90 million litres pa. since the 1990s, using wheat flour from its plant at Gunnedah to produce a range of wheat by-products with the balance of starch production fermented into ethanol. A CSR factory at Sarina in northern Queensland uses molasses and other wastes from sugar cane with the advantage that most of the carbohydrate is already sugar. It produces about 8 million litres pa.

5. Ethanol is currently used as a fuel in Brazil, USA and Canada.
i) Research the ethanol blends in these countries
Brazil: The current Brazilian legislation mandates blending of ethanol in gasoline in the range of 24 to 26 per cent. 40% of automobiles in Brazil operate on 100% ethanol, while the balance use a 22% ethanol blend.
USA: Blending of ethanol in gasoline is done on environmental considerations. Ethanol blending is 10 per cent in gasoline for cities requiring control on carbon monoxide emissions during winter months. Approximately 12% of all US gasoline contains ethanol at a blending percentage of 10%.
Canada: Blends containing 5-10% ethanol in gasoline are being marketed by several companies (throughout Ontario, Quebec, the western provinces and the Yukon), and are available at 1,000 retail outlets across the country. Approximately 5-10% of Canadian gasoline contains ethanol.

ii) Evaluate the success of current usage in those countries.
Brazil: In Brazil, the government has introduced a national, large-scale ethanol fuel program, which uses a 20% blend of ethanol with regular fuels. The use in these blends consumes 2/3 of the country’s sugar cane production and is essentially a farm support program for otherwise unemployed rural workers. Since its launch in 1975, the Brazilian Ethanol Program remains to date the largest commercial application of biomass for energy production and use in the world. It succeeded in demonstrating the technical feasibility of large-scale ethanol production from sugarcane and its use to fuel car engines. Forty percent of automobiles in Brazil already operate on 100% ethanol, while the balance use a 22% ethanol blend.
Fuel ethanol development in Brazil was fostered by concerns about expanding imports of foreign crude oil, and their effects on foreign exchange. Over the last 22 years, hard currency savings amounted to 1.8 billion US dollar/year. However, the 1999 production cost of ethanol was still higher than price of gasoline manufactured from imported oil which was the main reason for the financial difficulties faced by the program. Impressive technological progress has been continuously reducing ethanol production costs, but oil prices still need to be quite high for ethanol to be cost-effective. Socially, the program has been responsible for the creation of 720,000 direct jobs and 200,000 indirect jobs in rural areas
Local air pollution during harvesting season (burning required for manual harvest, use of sugar cane bagasse in the boilers) has been an environmental problem, but the replacement of gasoline by ethanol reduced atmospheric pollution in large Brazilian cities. So far, the Brazilian program has been successful, socially, environmentally and in terms of cost. It has produced a whole other industry for the country to export.

USA: Fuel-grade ethanol represents about 85% of the U.S. ethanol market. It is a clean-burning automotive fuel, and, as a fuel additive, it is also used as an oxygenate. “Oxygenates” are products blended into fuel to improve combustion and thus to reduce harmful air emissions. U.S. development was triggered by concerns about environmental quality, and recognition of the merits of using grains, produced in excess supply in the U.S., to reduce imports of mid- eastern oil. Ethanol is one of the few commercially available oxygenates that can be used to meet the requirement of the Clean Air Act Amendments of 1990 that gasoline be oxygenated in “non-attainment” areas (areas where certain Federal clean air standards are not being met). Most purchasers of fuel-grade ethanol are thus oil companies and fuel marketers that use it to meet this federal mandate. The Clean Air Act Amendments of 1990 mandated the use of oxygenated gasoline in areas with unhealthy levels of carbon monoxide. At the time, the primary oxygenates were ethanol and MTBE. Subsequently, MTBE has been shown to contaminate ground water supplies, and the demand for ethanol has increased significantly.
There are several benefits to using ethanol. It emits less carbon monoxide than gasoline, and adding oxygenates like ethanol to gasoline reduces carbon monoxide emissions. Last year ethanol use reduced US greenhouse gas emissions by 5.7 million tonnes, equivalent to removing more than 853,000 cars from the road. Ethanol is domestically produced and allows us to reduce the use of imported petroleum, supporting U.S. farmers and creating jobs.
All auto manufacturers approve the use of low-level ethanol blends, and although ethanol is more expensive to produce than gasoline, federal tax incentives reduce the price to a competitive level. It is therefore a cleaner and still cost-effective fuel. 85% blends of ethanol are also popular with the 3 million US owners of flexible-fuel cars, an expanding new market.

Canada: At the federal level, the ethanol portion of blended gasoline receives an exemption from the federal excise tax of 10 cents per litre on gasoline. At the provincial level, governments exempt the ethanol portion of blended gasoline from their road taxes, without restriction on the ethanol source or the content in ethanol. The Government of Canada and some provincial governments have also supported the development and use of ethanol fuel through research and development programs.
The energy efficiency of ethanol production from grain (corn, wheat, barley) is higher in Canada than the U.S. because of a much lower dependence on irrigation for grain production in Canada. Analysis in 1992 showed that ethanol made from Ontario-grown corn had over twice the combustible energy content as was used in its production. This analysis involved all aspects of corn production, including input and machinery manufacture and transport. The cost of ethanol-production from grain, at about 35-45¢/litre, currently exceeds the refinery-gate price of gasoline. Although the cost of production of ethanol has declined substantially over time as technology has improved, present price relationships mean that ethanol provides the highest economic value when it is used as an octane enhancer to replace other octane additives - especially additives containing heavy metals, and “aromatic” compounds such as benzene. Ethanol blended fuel is only a voluntary option in Canada at present, but it is a centre for research into new ways of processing biomass for ethanol production. Canadian ethanol blends are currently at 5-10% for regular automobiles.

iii) In USA it is mandated by the government to use ethanol blended fuel.
What is the situation in Australia? Does car fuel in Australia contain ethanol?
Currently there is no government mandate in Australia to use ethanol blended fuel. Federal legislation regulated a 10% limit of ethanol blends as of July 2003 and requiring that petrol stations adequately inform consumers if they are using petrol that includes ethanol. While 10% ethanol blends are available at a few outlets across the country, it is not a popular alternative.

iv) Evaluate the success of current usage of ethanol as fuel in Australia.
Ethanol fuels are not being used in Australia anywhere near as much as they are overseas and so can be seen as unsuccessful. The government's indecisiveness to mandate ethanol blends has impaired consumer confidence of ethanol-blended fuel, while public concern has caused much resistance. In addition, given that ethanol costs almost twice as much to produce than petrol, consumers would be unwilling to purchase ethanol fuel if it is more expensive and is less energy efficient than petrol. Thus, Australia is spending money on using up quickly expiring supplies of petrochemicals, and on foreign imports that are gradually rising in price. Ethanol is being produced, and with the large tracts of land, more cane and wheat feedstocks could easily be produced, but consumer confidence is extremely low and the government has made no move to implement any strategies to incorporate ethanol as fuels

6. Assess the potential of ethanol as an alternative fuel and discuss the advantages and disadvantages of its use.
Ethanol as an alternative fuel has its advantages. It is renewable and can replace the fast-dwindling supply of international petrochemicals. It usually burns cleanly, with minimal formation of particulates, so reduces some pollution, such as hydrocarbons and carbon monoxide. It may also reduce greenhouse gas emissions, but there is still debate on how much. However it also has its drawbacks. Its combustion as a fuel has increased emissions of oxides of nitrogen and acetaldehyde. Its use in over 10% ethanol-unleaded petrol blends has been proven to cause damage in cars not specifically manufactured for the ethanol component. It contains less energy than petrol, so even if the price is lower, more ethanol is still required to move a vehicle from one point to another. And even though it reduces greenhouse gas emissions, fossil fuels are still used as a fuel during the manufacturing of ethanol as well as in the planting, harvesting and transportation of feedstock crops.
Its use in the US is as an additive in the oxygenation of fuels to reduce the pollution emitted in motor vehicle combustion engines. In Canada one of the reasons for its use is because of its ability to restrict the freezing of fuel lines in engines. Brazil uses the production of ethanol to stimulate its economy and to provide jobs for the social benefit of its people. All of these are added incentives to use ethanol as an alternative fuel, but it has only one real outstanding benefit, and that is its status as a renewable resource. Studies are pointing at a very short lifespan for the remaining world petrochemical supply, and so the focus must turn to alternative, renewable fuels that can be adapted to with as little disruption as possible. 10% blends require no change at all in the mechanics of motor vehicles, but as in Brazil, it may be necessary to recalibrate the car fleet to suit any higher blends, eg. the E85 blend of 85% ethanol and 15% petrol, which has also been proven to reduce greenhouse gas emissions by up to 75%.
In a full cycle, using ethanol as a fuel in motor vehicles as well as in its own production, the use of ethanol as a fuel has many advantages over the current use of fossil fuels. And although its benefits do not seem to overly outweigh the benefits of using petrol as a fuel, the fact remains that it is a renewable resource that has the potential to stimulate the agricultural industry and lessen the globe’s reliance on disappearing non-renewable petrochemicals. As an alternative fuel, with more research into efficient ways to its production, ethanol could possibly be a very successful option in the future fuelling of motor vehicles.

7. Pathways 2 pg 39. Data Processing – Exercise on Heat of Combustion.

Resources: Presentation4-SessionIVB(11-12.30h)-LaRovere.ppt


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