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Fuels
Published in Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong, Combustion Engineering, 2022
Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong
One important alkane for characterizing ignition property is octane, C8H18, which can have different molecular structures, leading to drastically different autoignition characteristics (i.e., octane number). n-Octane (n-C8H18) has a straight chain of eight carbon atoms; isooctane (i-C8H18) has three methyl radicals bonded to specific carbons on a C5 chain, hence is called 2,2,4-tri-methyl-pentane. iso-Octane has a compact molecular structure that is more difficult to break and hence is more resistant to autoignition, i.e., and is of higher octane number. In contrast, long-chain alkanes are easy to break and are prone to autoignition, i.e., and are of low octane number. Furthermore, the longer the chain, the easier to break and autoignite. Isomers of hexadecane (n-cetane and isocetane) are two reference fuels used for determining the cetane number for diesel fuel. The effects of molecular structure on autoignition will be discussed in later sections.
Atomic-Scale Simulation of Tribological and Related Phenomena
Published in Bharat Bhushan, Handbook of Micro/Nano Tribology, 2020
Judith A. Harrison, Steven J. Stuart, Donald W. Brenner
Molecular dynamics has also been used to simulate indentation of an n-hexadecane-covered Au(001) substrate with an Ni tip (Landman et al., 1992). The forces governing the metal–metal interactions were derived from EAM potentials. A so-called united-atom model (Ryckaert and Bellmans, 1978) was used to model the n-hexadecane film. In this model, the hydrogen and carbon atoms were treated as one united atom and the bonds between united atoms were held rigid. The interchain forces and the interaction of the chain molecules with the metallic tip and substrate were both modeled using an LJ potential energy function. The size of the metallic tip and substrate were the same as in a previous study (Landman et al., 1990). The hexadecane film consisted of 73 alkane molecules. The film was equilibrated on a 300 K Au surface and indentation was performed as described earlier (Landman et al., 1990).
The First Law of Thermodynamics
Published in Kathleen E. Murphy, Thermodynamics Problem Solving in Physical Chemistry, 2020
The hydrocarbon liquid, hexadecane, C16H34, has a heat of combustion equal to –10,700 kJ per mole at 298.15 K and 1.0 bar. Given the products of the combustion reaction are H2O(l) and CO2(g), what would be the: Standard enthalpy of formation for hexadecane, C16H34, in kJ per mole?The ∆Ucomb for hexadecane, C16H34, at 298.15 K and 1.0 bar?As an alkane, hexadecane would be close in structure to the lipids or fat biomolecules. Compare the caloric content of hexadecane, C16H34, to that of an average fat, which is 9.0 kcal/g.
Effect of amphoteric surfactant on phase behavior of hydrocarbon-electrolyte-water system-an application in enhanced oil recovery
Published in Journal of Dispersion Science and Technology, 2018
Hamidreza Yarveicy, Ali Haghtalab
Using IKA-CMAG HS Egmont Steer model, the stock solutions of the aqueous electrolyte–surfactant are prepared at 0.05 to 0.5% wt % of surfactant and salinity of 0–20% wt % in the separate graduated glass tubes. Following preparation of the aqueous solutions, the hydrocarbon samples with the same volume of the aqueous surfactant solution are prepared and kept in closed graduated tubes which are completely sealed shed.[68] The n-heptane and n-hexadecane are used because these alkanes are a fluid series through hexadecane which has oil-like physical and chemical properties. By rotation of the tubes through end over end for 12 h at the speed of 10 rpm and 30 ± 0.5 C, the aqueous solution of hydrocarbon sample is mixed until microemulsions are formed as shown in Figure 2. The rotation speed is chosen low enough that simulates the fluid speed in a porous medium reservoir. Following 12 h, the tubes containing hydrocarbon phase, surfactant, and saline solution are placed at a thermostatic bath at a constant temperature to reach an equilibrium state so that the equilibrium phases don’t change. By observation of these equilibrium tubes, the different Winsor type and the water solubilization parameters are obtained. Prior and after each experiment, the weight and the volume of the samples are measured in each test tube to monitor the changes in weight and volume of the samples to keep the overall mass and volume balances.