Ethane calculated rates

For a fresh ethane feed rate of 100,000 kg/h, evaluate the impact of one-pass ethane conversion efficiency on the plant recycle rate and hydraulic loading by carrying out a material balance on the process and tabulating recycle flows for 40, 50, 60, and 70% conversion efficiency. For each calculation assume that no ethane leaves the product recovery unit, i.e., 3 = 0. 

Calculations with a = 0.8 A-1 (curve 1) were performed, in addition to a = 1 A 1, because the choice for the potential energy surface interpolation parameter although reasonable is somewhat arbitrary. Hase27 used a = 0.82 A 1, based on a fit of ethane decomposition rates to the experimental data. 

Both the C-C and C-H bond activation branches of the potential energy surface for the reaction between Fe and ethane (calculations by B3LYP method) are characterized by a low barrier for the first step (the insertion of the Fc into a C-C or C-H bond) [55]. The second step is the rate determining one. In the C-C bond activation this is a [1,3]-H shift leading to a complex between Fe=CH2 and methane. Calculations using high-accuracy quantum chemical methods (B3LYP and PCI-80) for the endothermic reaction... 

The Half-Life for Homolysis of Ethane at Room Temperature The —90 kcal / mol C-C BDE of ethane sets a lower limit to the activation energy for the thermally induced homolysis of the molecule. In Chapter 7 we will introduce the Arrhenius equation, which can be used to calculate rate constants from activation energies If we assume an Arrhenius pre-exponential factor (A) of 10 (a common value for a unimolecular process), the half-life for homolysis of ethane at 25 °C would be approximately 10 years. Our universe is postulated to have been around for at most only 10 ° years. Thus, hydrocarbons are thermally very stable ... 

An example of the application of molecular mechanics in the investigation of chemical reactions is a study of the correlation between steric strain in a molecule and the ease of rupture of carbon-carbon bonds. For a series of hexasubstituted ethanes, it was found that there is a good correlation between the strain calculated by the molecular mechanics method and the rate of thermolysis. Some of the data are shown in Table 3.3. 

Transient computations of methane, ethane, and propane gas-jet diffusion flames in Ig and Oy have been performed using the numerical code developed by Katta [30,46], with a detailed reaction mechanism [47,48] (33 species and 112 elementary steps) for these fuels and a simple radiation heat-loss model [49], for the high fuel-flow condition. The results for methane and ethane can be obtained from earlier studies [44,45]. For propane. Figure 8.1.5 shows the calculated flame structure in Ig and Og. The variables on the right half include, velocity vectors (v), isotherms (T), total heat-release rate ( j), and the local equivalence ratio (( locai) while on the left half the total molar flux vectors of atomic hydrogen (M ), oxygen mole fraction oxygen consumption rate... 

Since work with the radical clock substrate probes indicated important differences in the hydroxylation mechanisms for M. capsulatus (Bath) and M. trickosporium OB3b, work with (R) and (S)-[1-2H,1-3H]ethane with both enzymes was carried out (93, 94). With M. tri-chosporium OB3b, approximately 65% of the product displays retention of stereochemistry (93). A rebound rate constant of 2 - 6 x 1012 s-1 was calculated, assuming a free energy change of 0.5 kcal mole-1 for rotation about the C-C bond (94). This estimate approaches the value obtained from the radical clock substrate probe analysis (59). 

The equilibrium constant of hexaphenylethane dissociation, in striking contrast to the rate constant for dissociation, varies considerably with solvent. The radical with its unpaired electron and nearly planar structure probably complexes with solvents to a considerable extent while the ethane does not. Since the transition state is like the ethane and its solvation is hindered, the dissociation rate constants change very little with solvent.12 13 From an empirical relationship that happens to exist in this case between the rate and equilibrium constants in a series of solvents, it has been calculated that the transition state resembles the ethane at least four times as much as it resembles the radical. These are the proportions that must be used if the free energy of the transition state in a given solvent is to be expressed as a linear combination of the free energies of the ethane and radical states.14... 

At 252 °C based on kg/ks = 0.15 reaction (9) accounts for only 34 % of the ethane and 11 % of the ethylene. Reactions (6) and (7) are required to explain the concordance of results based on gas analysis and with those based on tetramethyl lead analysis. All observed orders and activation energies are consistent with this mechanism. If reaction (1) is the rate-controlling step in the initiation, the rate of this reaction can be calculated from... 

The first thing that stands out in Table 6.2 is that the OH-CH4 rate constant, 6.2 X 10 15 cm3 molecule 1 s-1, is much smaller than those for the higher alkanes, a factor of 40 below that for ethane. This relatively slow reaction between OH and CH4 is the reason that the focus is on non-methane hydrocarbons (NMHC) in terms of ozone control in urban areas. Thus, even at a typical peak OH concentration of 5 X 106 molecules cm 3, the calculated lifetime of CH4 at 298 K is 373 days, far too long to play a significant role on urban and even regional scales. Clearly, however, this reaction is important in the global troposphere (see Chapter 14.B.2b). 

Use the structure-reactivity relationship approach to calculate the rate constants for the reactions of OH with the following compounds and calculate the percentage difference from the recommended values in Table 6.2 (a) ethane, (b) n-butane, (c) 2-methylpen-tane, (d) 2,2-dimethylpentane, (e) 2,2,3-trimethyl-butane, (f) n-nonane, (g) n-decane. 

From the activation energies and the preexponential factors, the rate constants at 873 K can be calculated. They are listed in Table II. They show that for the gas-phase homogeneous reactions, the reactions of O atoms and OH radicals with ethene are very rapid and somewhat faster than their reactions with ethane. This fact would limit the maximum yield of ethene. It is well known that if the reactions of an alkane and an alkene are both first order in the hydrocarbon, then the maximum yield for the alkene of about 35% would be obtained when the rate constants, kA and kn, for the two reactions have equal values ... 

Exercise 18-9 Use bond energies and the stabilization energy of ethanoic acid (18 kcal mole-1, Section 18-2A) to calculate AH° for the addition of water to ethanoic acid to give 1,1,1-trihydroxyethane. Compare the value you obtain with a calculated AH° for the hydration of ethanal in the vapor phase. Would you expect the rate, the equilibrium constant, or both, for hydration of ethanoic acid in water solution to be increased in the presence of a strong acid such as sulfuric acid Explain. 

There are only few data sets of aqueous solubility for systems with hydrates (1) methane and ethane solubility in water as a function of temperature ramping rate (Song et al. 1997), (2) carbon dioxide solubility in water by Yamane and Aya (1995), (3) methane in water and in seawater (Besnard et al., 1997), (4) methane in water in Lw-H region [see Servio and Englezos (2002) and Chou and Burruss, Personal Communication, December 18,2006, Chapter 6], As a standard for comparison, Handa s (1990) calculations for aqueous methane solubility are reported in Table 4.3. 

Corma and co-workers152 have performed a detailed theoretical study (B3PW91/6-31G level) of the mechanism of the reactions between carbenium ions and alkanes (ethyl cation with ethane and propane and isopropyl cation with ethane, propane, and isopentane) including complete geometry optimization and characterization of the reactants, products, reaction intermediates, and transition states involved. Reaction enthalpies and activation energies for the various elemental steps and the equilibrium constants and reaction rate constants were also calculated. It was concluded that the interaction of a carbenium ion and an alkane always results in the formation of a carbonium cation, which is the intermediate not only in alkylation but also in other hydrocarbon transformations (hydride transfer, disproportionation, dehydrogenation). 

---