Ethanol

Table of Contents Introduction 3 Properties 4 Physical Properties of Ethanol 4 Chemical Properties of Ethanol 5 Sources of Ethanol 5 Production of Ethanol 5 Conventional Batch Fermentation Technology 6 Sulfuric Acid Technology 6 Gasification or Bioconversion 6 Catalytic hydration 7 Uses of Ethanol as a Fuel 7 Advantages and Disadvantages of Ethanol 8 Advantages of Ethanol Compared to Coal 8 Disadvantages of Ethanol Compared to Coal 9 Conclusion 9 List of References 10 List of Tables Table 1: Physical Properties of Ethanol 4 Table 2: Comparison of the Advantages between Ethanol and Coal 8 Introduction This century, the energy and chemical industries are challenged by the increasing scarcity of oil (Howell, 1981). Several alternative fuels have been introduced to overcome this problem. Ethanol, as a renewable fuel, is one of the alternative fuels that appears to have the potential to substitute the demand for petrol. Several countries have been using ethanol, either in its own right or mixed with petrol, as liquid transport fuel (Enecon, 2002). Blends that contain petrol and ethanol are presently used by about 80 million vehicles throughout the world (Schell and Hogan, 2003). In fact, using ethanol as transport fuel is not a new idea as ethanol had been used to run the Model T Ford, which were first produced in 1908 (New Scientist, 2006). Ethanol, with a chemical formula of C2H5OH, is an organic compound and has been classified as alkanol (Schell and Hogan, 2003). Ethanol can be produced through the fermentation of sugars and starch as well as the hydration of petroleum fractions (Eng, Lim and Lim, 2007). Ethanol produces 70% of the heat that is produced by petrol. However, carbon dioxide and water are the only products of ethanol combustion, and hence it is known as a clean fuel (ibid.). This report will emphasize both the physical and chemical properties of ethanol, the sources and the production of ethanol as well as the usage of ethanol as a fuel. The comparison of the advantages and disadvantages between coal and ethanol will also be discussed in this report. Properties Physical Properties of Ethanol Properties that do not take part in a chemical reaction are known as physical properties (Lewis and Evans, 2006). Ethanol, like any other substance, has its own unique physical properties. Table 1 shows some of the physical properties of this fuel. Table 1: Physical Properties of Ethanol |Structural formula |C2H5OH | |Colour |Colourless | |Odour |Sharp smell | |Melting point ( oC) |−117 | |Boiling point (oC) |78 | |Solubility (g per 100 cm3 water) |Miscible in all proportions | (Eng et al., 2007) One of the unique physical properties shown in the table above is the solubility of ethanol. Ethanol has a high solubility in water. It can dissolve in water in all proportions, in other words, it is completely miscible with water (Stewart, 1985). The high solubility of ethanol is due to its ability to form hydrogen bonds with water (Lewis and Evans, 2006). Moreover, ethanol, which consists of an –OH group, appears to be an excellent solvent, as it has similar solvent properties as water (ibid.). The polar nature and hydrogen bonding of ethanol enables it to act as a solvent to both organic and covalent substances (Schell and Hogan, 2003). Ethanol has a low melting and boiling point (Eng et al., 2007). However, the presence of hydrogen bonds triggers it to have a higher melting and boiling point than other alkanes of the same molecular mass (Schell and Hogan, 2003). Chemical Properties of Ethanol Ethanol has several properties that involved in chemical reactions and determined by its functional group. These properties are known as chemical properties (Eng et al., 2007). Ethanol is very flammable, which means that it can easily burn with excess oxygen (Stewart, 1985). Ethanol has a combustion heat of 1560 kJ mol-1 and therefore it is very suitable to be used as a fuel (Schell and Hogan, 2003). Furthermore, ethanol can be oxidised to form ethanoic acid by potassium dichromate (VI) and potassium manganate (VII) (Eng et al., 2007). When potassium dichromate (VI) is added to ethanol, the solution changes its colour from orange to green (ibid.). The changing of colour indicates that a chemical reaction has occurred and ethanol has been oxidised. Moreover, ethanol is able to undergo dehydration to form ethene, C2H4 (Stewart, 1985). In the formation of ethene, a water molecule is eliminated from each ethanol molecule (Eng et al., 2007). Sources of Ethanol Since ethanol is mainly produced from the fermentation of yeasts, the main raw material used in its production is crops (Enecon, 2002). Crops that are commercially used in ethanol production can be classified into cellulose-based crops and starch or sugar crops (Wells, 1980). Cellulose-based crops, for examples, wood, wheat straw, and other agricultural residues, offer a low raw material cost. However, the conversion of the cellulose-based crops into ethanol is costly (ibid.). On the other hand, the starch or sugar crops are relatively cheap to convert to ethanol, but, they require a higher cost in raw materials. Sugar cane, sweet sorghum, sugar beet, wheat, fodder bet and cassava are some of the examples of these crops (ibid.). Production of Ethanol For thousands of years, ethanol has been produced through the fermentation of yeasts from sugars and starches (Eng et al., 2007). Due to the development of modern technologies, new methods of producing industrial ethanol have been discovered to increase the productivity of ethanol production. Conventional Batch Fermentation Technology In the fermentation process, actively growing yeast is added to the sugar or starch in an enclosed fermenter (Wells, 1980). Biological enzymes are released by yeast to break down the sugar and starch into glucose. The glucose is then decomposed into ethanol and carbon dioxide by an enzyme call zymase (Eng et al., 2007). The fermentation requires approximately thirty hours to obtain the maximum yield of ethanol (Wells, 1980). Then, the mixture is removed from the fermenter and the ethanol is purified by fractional distillation (ibid.). Sulfuric Acid Technology Concentrated sulfuric acid is used in two stages to hydrolyze the feed of ethanol. After the hydrolysis, the solution is filtered to eliminate lignin and other insoluble compounds (Enecon, 2002). The sugars are then separated from the acid by industrial scale’s chromatography, however, not all acid is removed from the sugars (ibid.). Thus, lime is used to neutralize the remaining acid in the sugar solution (ibid.). The sugar solution then undergoes the fermentation process to produce ethanol. Gasification or Bioconversion Gasification is a process to hydrolyze biomass in order to produce feed for ethanol. Biomass is gasified to produce syngas, which consists of CO, CO2 and H2 (Enecon, 2002). The syngas is then used as feed to produce ethanol from the fermentation of special microorganisms (ibid.). Catalytic hydration Catalytic hydration is the direct hydration of ethene, which is obtained from the petroleum fractions. Ethanol is produced by the combination of ethene with steam (Eng, et al., 2007). In the hydration of ethene, phosphoric acid is used as catalyst while the temperature and the pressure of the reaction are set at 300oC and 60 atm. The ethanol produced is in the form of gas and is then condensed into liquid (ibid.). Uses of Ethanol as a Fuel The highly flammable characteristic of ethanol makes it an excellent fuel for vehicles as well as engines. Ethanol is used in varieties of ways as transport fuel. Ethanol can be blended with petrol in several proportions and is used as transport fuel. Blend that contains 10% of ethanol and 90% of petrol, which is also known as gasohol, can be used in most modern cars without any further modifications (Enecon, 2002). In addition, blends of up to approximately 20% ethanol are used in many petrol engines with only minor modification to the carburetor (Wells, 1980). For example, in the United States, the blends are widely used in the vehicles that consist of engines and fuel systems that are able to utilize ethanol of this level efficiently (Enecon, 2002). Pure, hydrous ethanol, which consists of 96% of ethanol and 4% of water, can also be used in vehicles that have engines and carburetors that are specially designed for high levels of ethanol (ibid.). Moreover, ethanol can also blend with diesel at low level and is used as fuel in diesel engines (Wells, 1980). However, more extensive modifications to the existing engines are required (ibid.). Dual fuel system or specialised emulsifiers are used to facilitate blending and to avoid phase separation between ethanol and diesel (Enecon, 2002). Advantages and Disadvantages of Ethanol Advantages of Ethanol Compared to Coal Several advantages can be determined when ethanol is compared with coal. Table 2 shows some of the advantages of ethanol compared to coal. Table 2: Comparison of the Advantages between Ethanol and Coal |Ethanol |Coal | |Renewable fuel |Non-renewable fuel | |Environmental friendly |Not environmental friendly | |Only produces carbon dioxide and water |Produces pollutants that caused air pollution | |Spills are biodegradable |Ash particles produced are not biodegradable | (Enecon, 2002) One of the advantages shown in Table 2 is the benefit of ethanol as a renewable fuel compared to coal which is non-renewable. As ethanol is produced from the fermentation of yeasts by using crops as its major feed, the energy produced from ethanol combustion is known as renewable. The renewability of coal is, however, a timely process which requires millions of years for the decomposition of vegetation (Schell and Molyneux, 2004). Hence, it is quite impossible to recreate coal in a short period of time, whereas, for ethanol, it can always be restored by growing new crops. Although the combustion of ethanol produces carbon dioxide, but it has zero net carbon dioxide emissions as it is balanced by the growing of crops that are used to produce ethanol (Enecon, 2002). On the other hand, coal has net carbon dioxide emissions of 1.7 tonnes per MWh (ibid.) and it also produces carbon monoxide and sulfur dioxide which contribute to air pollution (Schell a Molyneux, 2004). Moreover, the spills of ethanol are biodegradable whereas the ash particles produced in the combustion of coal are not biodegradable (Schell and Hogan, 2003). Disadvantages of Ethanol Compared to Coal Ethanol, however, has some disadvantages when compared to coil. The most obvious disadvantage when comparing ethanol to coal is that it requires vast agricultural land that supposed to supply food to the world (New Scientist, 2006). Unlike ethanol production that causes a sharp decline in world grain stocks (ibid.), the production and the extraction of coal do not have any negative impact to the agriculture industry. Apart from the agricultural effects, ethanol does not produce as much energy as coal. Therefore, it is expected that the fuel consumption for ethanol is higher than that of coal (Wells, 1980). Conclusion Ethanol, as a renewable fuel, has the potential to be the most common alternative fuel used in industries and vehicles in the future. It is also one of the biofuels that is able to help countries throughout the world to reduce their dependency on fossil fuels and combat the sharp increasing prices of fossil fuels (New Scientist, 2006). However, research has been carried out to increase the usage of ethanol as a fuel. Furthermore, some scientists have been working on a perfect way to produce ethanol from non-food crops and biomass (ibid.). Hence, ethanol is estimated to be widely used for coming centuries. List of References Enecon, S.S.&A. (2002). Wood for Alcohol Fuels. Kingston Act: RIRDC. Eng, N.H., Lim, E.W. and Lim, Y.C. (2007). Focus Super SPM Chemistry. Malaysia: Pelangi. Fuels Gold. (2006, September 23). New Scientist, pp. 36-41. Howell, D.A.R. (1981) Energy and Chemistry. In Thompson, R. (Ed.). (1981). Energy and Chemistry (pp. 1-10). Great Britain: Whitstable Litho Ltd. Lewis, R. and Evans, W. (2006). Chemistry. (3rd ed.). New York: Palgrave Macmillan. Schell, M. and Hogan, M. (2003). Chemistry Identification and Production of Materials. Australia: Science Press. Schell, M. and Molyneux, K. (2004). Chemistry Energy. Australia: Science Press. Stewart, B. (1985). Progress with Chemistry 2. East Sussex: Cassell Ltd. Wells, S. (1980). Fuel Ethanol Production. Australia. ----------------------- USFP English for Science Fuel Report ETHANOL Name Tang Huey Ming Fiona Student ID 346993 E-mail 346993@studygroup.edu.au Class SJESA2/7 Subject English for Science Teacher Shannon Assignment Fuel Report Date Due 11th April 2008 (Friday)