Due to the combustion of fossil fuels that has put the atmosphere in a lamentable state, finding an alternative fuel source has become increasingly prioritized. Biofuels have gained significant attention as a potential alternative energy source as the depletion of traditional fossil fuels has become more apparent. Like petroleum based fuels, biofuels consist of combustible molecules that emit carbon dioxide.
Biofuels-unlike petroleum products- are derived from renewable sources. Also, in burning biomass, the amount of CO2 being released by combustion exceeds no more than than what is produced in natural processes. Currently, the absence of technology that would allow released CO2 to be turned back into usable fuel means that petroleum based fuel is a finite commodity. Because of the difference in chemical composition of petroleum and biofuels, chemical properties are different, including, the energy content of the fuel. In this experiment, I will be determining the effect of oxygen content of different fuels on combustion efficiency and energy content.
As airlines account for two percent of the world’s greenhouse gas emissions, industries have been working to find an economically and environmentally sustainable alternative to jet fuels. In a 2017 article published by Scientific American, John Fialka, an editor of ClimateWire, reported the advancements made by aerospace industries on creating feasible aircraft fuels that reduce these greenhouse gas emissions. Neste Corp, an oil refining and marketing company based in Finland, showed some of the most promising results during test flights. The company had originally used palm oil to create biofuel.
However, after being attacked by environmental groups due to the many known detrimental effects of creating palm oil plantations can have on the environment, Neste had agreed to phase out the use of palm oil in the manufacturing of clean oil. Instead, they have created a new renewable fuel from waste oil that they call “hydrotreated vegetable oil”, which closely resembles kerosene. Rather than the process of transesterification to create traditional biodiesel, Neste renewable fuel requires a process called hydrodeoxygenation to remove oxygenated compounds which makes the chemical structure to be more similar to petroleum derived fuels.
“It is definitely fair to say that Neste is a pioneer,” says Darrin Morgan, Boeing’s chief strategist for creating new aviation fuels “They took a big risk and deserve a lot of credit. They bet a large percentage of their company on the future of renewable fuels at a time when a lot of people were not making that bet.”Alkanes, such as paraffin, are hydrocarbons as they consist of carbon and hydrogen atoms and lack any other functional groups. Because of this, alkanes are considered the simplest and least reactive type of hydrocarbon. As the chemical structure of alkanes only consists of single bonds, alkanes are referred to as saturated hydrocarbons since each carbon atom is saturated with hydrogen atoms. Its lack of double and triple bonds, resulting in its lack of unsaturation, distinguish alkanes from other compounds that also exclusively contain carbon and hydrogen atom. Commercially, alkanes are very important due to their role as the principal constituent of gasoline and lubricating oils.
Pure alkanes, such as hexanes, are usually used at solvents.Within the carbon-carbon bond and the carbon-hydrogen bond, the energy that is confined is relatively high and rapid oxidation produces a large amount of heat that manifests in the form of fire. The general formula of a alkane, or a saturated hydrocarbon, is C n H 2 n+2.Vegetables are known as triglycerides which are esters of glycerol and fatty acids. Glycerol is a colorless, odorless, hygroscopic (having a tendency to absorb moisture from the air), viscous liquid.
During the process of transesterification to produce biodiesel from triglycerides, glycerols are removed as they are too viscous to perform properly in a diesel engine over a long period of time. Fatty acids are long chain hydrocarbons with a carboxylic acid. Carboxylic acids are compounds which contain a -COOH group, in which a carbon atom is bonded to an oxygen atom by a double bond and to a hydroxyl group by a single bond.The chemical compounds consisting in biofuels drastically differ from those found in petroleum fuels.
Petroleum contains alkanes of long hydrocarbon chains whereas most biofuels contain long chain esters. The differing chemical composition in these molecules result in a dramatic change in chemical properties. For example, biofuels tend to be more corrosive than unreactive alkenes. The fatty acid methyl esters found in biodiesel can be biodegraded by anaerobic bacteria, producing hydrogen sulfide and other acids. Compared to petroleum, biofuels have a higher viscosity and a higher freezing point which can cause engines to clog at low temperatures. Arguably, one of the most significant effects of the presence of oxygen molecules in fuel molecules is the lower energy content. Molecular oxygen is necessary for the combustion of fuels for energy as oxygen must react with the fuel compound to produce energy (oxides).
If an oxygen molecule is present in the combusting material, it will react with the fuel first. In many cases of biofuel, a C-H bond has replaced with a C=O bond and a hydroxyl bond. The oxygen present has insignificant contribution to the combustion energy of the molecule. Also, due to its relatively high weight, oxygen molecules occupy much of the weight of the fuel therefore resulting in a fuel with less energy per weight. As the depletion of petroleum products become increasingly apparent, the importance of alternatives derived from biorenewable sources increase. In finding how the presence of oxygen in fuel molecules affect the energy content of fuels and to what extent, changes can be driven towards how to make biodiesel more feasible in relation to oxygen content. As of now, Neste Corporation of oil refining and marketing have pioneered in new techniques to create higher energy contented biofuel.
Using a process called hydrodeoxygenation where oxygen molecules are removed from the fuel molecules, Neste corp produces biofuels with energy content similar to those derived of petroleum products, therefore higher than biodiesels produced using the traditional transesterification process. However, because of the large amounts of hydrogen used during the hydrodeoxygenation process, chemical engineering students at Chonnam National University, researched an alternative to hydrodeoxygenation using only a minimal amount of hydrogen using a process called catalytic deoxygenation where precious metal-based catalysts are used for the catalytic cracking of biofuels.