Chemical Composition And Properties: Gasoline Vs Diesel Fuels

Best idea to pick on a number of deposits such as Natural gas, Gasoline, Kerosine Heavy gas oil, Diesel (2) and discuss how the nature of the petroleum chemistry will influence the type of deposit and its properties and uses.

Take the deposits you looked at in the first part and discuss what they are used for: How does the chemistry affect the refining process? What are the physical (Distillation, absorption etc.) and chemical (Hydro-treating, hydrocracking etc.) processes used?

Chemistry of Gasoline Fuel

Gasoline and diesel are the major key fuels which are used in driving automobiles. The uses of these fuels are led to two major engines namely: diesel engines and gasoline engines. Diesel and gasoline fuels are product of the same crude oil (McNally 2017). The main different come in the stage and which the two fuels are extracted from the crude oil. The crude oil is refined to give out fuels with different consistencies and some of them are the gasoline and diesel fuel. Therefore one of the major differences between gasoline and diesel is the level of consistency. Diesel fuel is thicker and more oil in consistency. This is unlike gasoline fuel which is lighter in consistency. In addition, due to the different stages of extraction, gasoline due to the lightness is more flammable than diesel (Shukla 2017). Therefore gasoline fuel will require less amount of heat to combust than diesel fuel. Most important, since these two fuels are extracted from the same crude oil, they are made of carbon atoms. The major difference is the amount of carbons which are composed in each of the fuel. Generally, the level of extraction of the fuel determines the amount of hydrocarbons composed. This is able to make the difference in the chemical composition of the different fuels. The fuel chemistries are affected as well by the stage in the extraction process when the fuels are extracted (Kanopy (Firm) 2016). In addition, it has to be noted that there are only few differences between gasoline and diesel fuels in their composition and properties. The same process, which is fractional distillation is used to separate different components of crude oil and therefore used to extract both fuels.

Gasoline and diesel are defined by their chemistry level. Their chemical composition is able to define their reaction at different situations. Hydrocarbons are the major components which are part of the fuel chemistries. The fuels are made of chains of both carbon and hydrogen (Agarwal 2016). The different number of the carbon composed on the fuel determines the nature of the fuel. These numbers are able to define the chemical and physical chemistry of the specific fuel. Under this section, this paper will analyze the different chemistries of gasoline and diesel fuels. This will involve their structure and type of isomers which are composed on each fuel.

As noted early, gasoline is composed of carbon and hydrogen atoms. These chemical elements are able to define the chemical reaction activity which this fuel is involved in. Moreover, gasoline is a mixture of large number of hydrocarbons. Gasoline has between 5 and 12 carbon atoms. In addition, gasoline is a natural by-product of the petroleum industry (Speight 2014). Therefore gasoline is made from a non renewable source. Fractional distillation is the major process which is used to extract gasoline from crude oil. Gasoline is also known as petrol in some countries and it is mainly used to power automobiles. In definition, gasoline is a mixture of over 500 hydrocarbons. In addition, in their chemical composition, gasoline has small amount of alkane cyclic and aromatic compounds. In addition it has to be noted that gasoline lacks alkenes and alkynes in their composition. The boiling points of hydrocarbons vary when the fractional distillation is used for separating crude oil (Kent, Bommaraju & Barnicki 2017). The boiling point varies with the length of hydrocarbons in the specific fuel. This means that the hydrocarbon in gasoline is able to define its boiling point.

Isomers of Gasoline Fuel

In order to enhance its usage, different components are added to gasoline. This is able to alter the chemical composition and properties of gasoline. In the end, the combustion rate of gasoline is altered to the required specification. The few carbon chain in the gasoline means that the fuel is lighter. In turn, this means that the fuel require less energy to burn. Moreover, due to the fewer hydrocarbons, the density of gasoline is low and this means it is highly inflammable (Owen 2010). Generally, it can be concluded that the chemical composition of gasoline is able to determine the chemical characteristics and behaviour of the fuel. In addition, the chemical composition of the fuel is able to determine the energy stored. The energy density of the fuel is able to dictate the amount of energy stored and can be transported in the same volume.

In addition, gasoline has different isomers. Isomers are defined as molecules which have same chemical composition but do show difference in molecular structure. This means that the isomers do have same number and type atoms and the only difference is on the arrangement. In addition, it has to be noted that the different arrangement of the atoms is able to result to difference in physical and chemical properties. In gasoline, the isomers are able to exhibit different characteristics of boiling point and melting points (Maurya 2018). These key factors affect the combustion rates of the specific isomers. Due to this factor, the selection of gasoline isomers for fuel is very important. Additionally, the different isomers are able to produce different energy when combusted. Different isomers of gasoline are able to burn different. For instance, octane, which is a gasoline fuel, has 18 known isomers. The different octane gasoline isomers are “n-octane, 2-methylheptane, 3-methylheptane, 4-methylheptane, 2.2-dimethylhexane, 2.3-dimethylhexane, 2.4-dimethylhexane, 2.5-dimethylexane, 3.3-dimethylhexane, 3.4-dimethylhexane, 3-ethylhexane, 2.2.3-trimethylpentane, 2.2.4-trimethylpentane, 2.3.3-trimethylpentane, 2.3.4-trimethylpentane, 2-methyl-3-ethylpentane, 3-methyl-3-ethylpentane and tetramethylbutane.”  The 2.2.4-trimethylpentane which is also known isooctane is used for the reference of octane rating scale. In addition, the 2.2.4-trimethylpentane is part of gasoline and helps to reduce the engine knocking noise which vehicles do exhibit sometimes (Maurya 2018). These octane isomers are derived from octane formula of C₈H₁₈. The choice of the octane isomers is important to achieve the specific goals of fuel such as stable burning. Some of octane isomers are able to achieve this combustion factor better than others. To produce energy, gasoline is burned with oxygen to produce energy and other products according to equation below.

Chemistry of Diesel Fuel

2C₈H₁₈   + 25O₂ = 16CO₂ + 18H₂O

As for the above figure, the first is an n-octane isomer, which is more linear. The second one is an iso-octane, which is more branched more. This isomer is most used in many fuels and help to give the octane rating for the fuel. In analysis, the first octane isomer will be able to burn more quickly than the iso-octane, which is more branched (Oak Ridge National Laboratory et al., 2007). Moreover, when the choices of fuel are being made, the branched ones are more preferred since they burn slowly and more evenly than the first isomer. The octane rating is a key factor which is considered when it comes to gasoline choice. Octane rating is defined as the number which is visible on gas pumps and a measure of how much iso-octane is available in the fuel. High iso-octane presence in the fuel mixture is usually preferred for even burning of the fuel.

In addition, the isomers have different melting points and boiling points. For instance, n-octane has a melting point of -57⁰C and boiling point of 126⁰C. On the other hand, 2.3-dimethylhexane has a melting point of -110 ⁰C and a boiling point of 116 ⁰C while 4-methylheptane has a mp of -121 ⁰C and a bp of 118 ⁰C (Gesser 2012). These factors as seen are able to affect the combustion rate of the different octane isomers.

In addition, diesel as well is used as an automobile fuel, which is a by-product of petroleum. Moreover, it is achieved through fractional distillation. Compared to gasoline is denser and has a higher boiling point than water. In terms of the chemical composition, is composed of hydrocarbons which have long chain of carbon where they have carbon atoms of between 8 and 21 (Roussak & Gesser 2013). Therefore compared to gasoline, diesel has more carbon atoms which make is heavier than gasoline. The major compounds of diesel include paraffins, isoparafins, napthenes, olefins aromatic hydrocarbons. Moreover, diesel is categorized according to different grades which are based on different uses which have to be taken. In addition due to its chemical status, diesel burn without sparks due to the compression at the air inlet when burning it.

In addition, in terms of its chemical composition, diesel is composed of about 75 percent saturated hydrocarbons and 25 aromatic hydrocarbons. The chemical formula of diesel range from C₁₀H20 to C₁₅H₂₈ (Roussak & Gesser 2013)_. The average type of diesel fuel by the use of chemical formula is C₁₂H₂₄. The temperature of diesel is able to vary according to the available environment. In addition, the range of boiling point between 150 and 380^oC.

Grades of Diesel Fuel

In addition, the chemical formation of diesel is composed of many components which are not individually made. Although diesel can be viewed as natural product the end product diesel fuel is man-made product (Dane, Voorhees & National Renewable Energy Laboratory (U.S.) 2010). During fractional distillation, diesel fuel is created at the end of the tower. Due to the higher density, diesel fuel is oily and sometimes is referred to as diesel oil. Due to the high number of hydrocarbons, diesel evaporates much slower compared to gasoline fuel (Speight 2014). The higher melting point is as well as a result of the high number o hydrocarbons, which ranges between 200 and 300 ^oC. In its combustion, diesel is able to burn in presence of air to produce energy, carbon dioxide and water. The following equation shows the chemical reaction of dodecane which is type of diesel in presence of air

C₁₂H₂₆  + 18.5O₂ = 12CO2 ₊ 13H₂O + energy

Diesel has different types of grades and which have different chemical composition. The typical molecule of biodiesel, which is one of the grades of diesel, has long chain of carbon atom, which has hydrogen atoms attached to the carbon atoms. The following figure shows the typical representation of a biodiesel. This type of diesel has an end which is known as an ester functional group. This is the part which is on the far end of the following figure. In addition, due to its density, diesel is able to yield more energy per gallon. According to research, a gallon of diesel is able to produce 10% more energy than gasoline (Armitage 2009). The different ranges of diesel are able to meet different fuel requirements. The ranges have different chemical and physical characteristics which ensure that different uses are met.

Moreover, like other fuels and elements, diesel has its own isomers. As noted, the different isomers have different arrangement of atoms which lead to them having different chemical and physical characteristics. One of the diesel isomer is dodecane. This is a alkane hydrocarbon which is represented by a chemical forma of CH₃(CH₂)₁₀CH₃, or simply C₁₂H₂₆, which is a oily liquid and part of paraffin series. This isomer has a record of 255 isomers (Owen 2010). The different isomers have different characteristics. Additionally, the different isomers have different uses according to their characteristics (Armitage 2009). This helps to meet the different need and provide key merits which are required in the diesel use. The development of these isomers is able to provide different fuels with different characteristics. This ensures that the different needs of the fuels are met depending on the need of use and combustion required. Generally, the different isomers ensure that the different fuel characteristics provide wide range of use of the diesel fuel.

Petroleum processes are used in refining crude oil and able to produce gasoline, diesel among other fuels and products. Fractional distillation has been used for long for refining crude oil in order to produce gasoline, diesel and other products. Under the fractional distillation, the crude oil is heated up and then the favour vaporizes (Holt 2008). After that the vapour is condensed to achieve the different fuels. The chemistry of gasoline and diesel are able to affect their operations. Both physical and chemical characteristics define the different uses of the fuels (Meyers 2009). These play a key role when refining the fuels and determine at which level the fuel will be extracted. Physical and chemical transformation of the crude oil is able to take place during the refining process. Distinct processes are able to happen at different specific facilities or process units.

First, distillation process is utilized before the chemical refining of the crude oil is carried out. The distillation is able to separate the liquid crude of the solid particles. In the distillation process, the crude is divided into different sections (Meyers 2009). This helps to easily enable the separation of the crude according to their density. The fuels with high number of carbon are widely used in this step of processing. Crude distillation is able to separate the crude oil into different ranges of the fuels boiling points so that they can be further processed. During refining process, the level of carbon and density is able to affect the level at which each of the fuel will be collected. When using the fractional distillation, the chemical composition is key at the level when the fuel will be collected. First, gasoline will evaporate first before diesel (Keyworth & National Petroleum Refiners Association 2010). This is because gasoline is lighter and has low boiling point than diesel. Fractional distillation is used for the refining of crude oil since it components have different boiling points. Some of the important processes used for the distillation include the atmospheric distillation and vacuum distillation. The distillation process is able to separate the fuels according to different ranges of their hydrocarbons.  Therefore under this process, the chemical hydrocarbon structure of the fuel is important. Generally, it can be noted that the chemical structure of the fuels influence the physical process of distillation. After distillation, the fuels are composed at different ranges of their boiling points due to the differences in carbon atoms at each fuel.

Additionally, chemical composition of the fuels plays an important role in refining of the fuels. Chemical processes are able to enhance the refining process by further refining the fuels to their different specific fuels. One of the major chemical processes used for refining crude oil and especially gasoline and diesel is the conversion or cracking process (Demirbas 2008). Tin this process, the heavy crude oil and fuel specific parts are broken down into lighter refineries. These finer fractions are then further processed or blended to produce the required chemical composition of fuels. The major processes which are included in this stage include the hydrocracking and fluid catalytic cracking (FCC). Next in the chemical processes, the upgrading process takes place. Under this stage, the molecular structure of the fuels is rearranged to improve the properties of the fuels. This process helps to enhance the value of the gasoline and diesel components (Argonne National Lab et al., 2011). Isomerisation and catalytic reforming are major processes which are included in this stage.

In addition, another key process which is included in the chemical process is the treatment of the fuels. This process is used to remove hetero-atoms impurities. This is seen as a purification process of the fuel and it is used to remove aromatics compounds from the refining streams. Examples of processes which may be applied at this stage include FCC feeding hydroheating, reformer feed hydroheating, Gasoline and distillate hydroheating and benzene saturation. Additionally other processes which are included in refining of gasoline and diesel include the separation and blending processes (Ramirez-Corredores & Borole 2011). The separation process is able to use both physical and chemical separation. The different parts of the fuels are further refined for quality controls. Fractionation and aromatic extraction are some of the key processes used in this process. Blending process helps to combine blendstocks and produce finished products of the fuels. This stage ensures that the fuels are able to meet the different specific requirements and meet required environmental standards. 

Conclusion

In conclusion, both gasoline and crude oil have most of the characteristics similar since they are all produced from same crude oil. The numbers of carbons are usually the major differences in the two fuels. Moreover, another difference can be traced on the refining stage when the fuels are extracted. Moreover, the chemical and physical characteristics are able to differ in the two fuels. As seen the two have different ranges of number of carbons. This makes their physical characteristics and chemical characteristics different. In addition, the different types of fuels have their own isomers. The isomers bear different characteristics due to difference in the arrangement of their atoms. While purchasing the fuels, it is important to consider the type of isomer which is preferred.  The isomers of these fuels are able to differ in term of their purpose and use. Physical and chemical characteristics are able to influence the refining processes which are involved. Distillation is one of the major physical processes used in refining of the fuels. This process helps to separate the fuels according to their boiling point ranges. In chemical refining, different processes are involves. Some of them include hydrocraking, cracking, isomerisation, hydroheating among other processes.

References

Agarwal, S. (2016). Engineering Chemistry. Cambridge: Cambridge University Press.

Armitage, P. (2009). Crude oil tanker basics: The theory and practice of crude oil cargo operations. Edinburgh: Witherby Seamanship International.

Dane, J., Voorhees, K. J., & National Renewable Energy Laboratory (U.S.). (2010). Investigation of nitro-organic compounds in diesel engine exhaust: Final report February 2007 - April 2008. Golden, CO: National Renewable Energy Laboratory.

Demirbas, A. (2008). Biodiesel: A realistic fuel alternative for diesel engines. London: Springer.

Environment Protection Agency (EPA) (2008).Direct final rule update: Regulation of fuel and fuel additives : gasoline and diesel fuel test methods. Washington, D.C: U.S. Environmental Protection Agency, Office of Transportation and Air Quality.

Gesser, H. D. (2012). Applied chemistry: A textbook for engineers and technologists. New York : Kluwer Academic/Plenum Publishers.

Griffin, P., Laurszen, T., & Robertson, J. (2016). Egypt: Guiding Reform of Energy Subsidies Long-Term. Washington, D.C: The World Bank.

Holt, D. (2008). Crude oil. Market Rasen: Total-E-Bound.

Kanopy (Firm). (2016). Crude Impact. [San Francisco, California, USA]: Kanopy Streaming.

Kent, J. A., Bommaraju, T. V., & Barnicki, S. D. (2017). Handbook of industrial chemistry and biotechnology. Cham: Springer.

Li, J., Xiao, X., & Floudas, C. A. (June 01, 2016). Integrated gasoline blending and order delivery operations: Part I. short-term scheduling and global optimization for single and multi-period operations. Aiche Journal, 62, 6, 2043-2070.

Maurya, R. K. (2018). Characteristics and control of low temperature combustion engines: Employing gasoline, ethanol and methanol. Cham: Springer.

McNally, R. (2017). Crude volatility: The history and the future of boom-bust oil prices. Place of publication not identified: COLUMBIA University Press.

McRae, S. D., & National Bureau of Economic Research,. (2017). Crude oil price differentials and pipeline infrastructure. Cambridge, Mass. : National Bureau of Economic Research.

Meyers, R. A. (2009). Handbook of petroleum refining processes. New York: McGraw-Hill.

Oak Ridge National Laboratory., Bunting, B. G., Szybist, J. P., Fuels, Engines and Emissions Research Center, National Transportation Research Center, & EE USDOE - Office of Energy Efficiency and Renewable Energy (EE). (August 2007). Chemistry Impacts in Gasoline HCCI. Oak Ridge, Tenn: Oak Ridge National Laboratory.

Owen, K. (2010). Gasoline and diesel fuel additives. Chichester: Published on behalf of the Society of Chemical Industry by Wiley.

Ramirez-Corredores, M. M., & Borole, A. P. (2011). Biocatalysis in Oil Refining. Burlington: Elsevier Science.

Roussak, O. V., & Gesser, H. D. (2013). Applied chemistry: A textbook for engineers and technologists. New York: Springer.

Schobert, H. H. (2013). Chemistry of fossil fuels and biofuels. Cambridge: Cambridge University Press.

Shukla, A. K. (2017). Analytical Characterization Methods for Crude Oil and Related Products. Newwark John Wiley & Sons, Incorporated.

Speight, J. G. (2014). The chemistry and technology of petroleum. Boca Raton: CRC Press, Taylor & Francis Group