Ethane kinetics

Magomedov RN, Proshina AYu, Peshnev BV, Arutyunov VS. Effects of the Gas Medium and Heterogeneous Factors on the Gas-Phase Oxidative Cracking of Ethane. Kinet Catal 2013 54(4) 394—9. 

Burcat A, Skinner G B, Crossley R W and Scheller K 1973 High temperature decomposition of ethane Int. J. Chem. Kinetics 5 345-52... 

Waage E V and Rabinovitch B S 1971 Some aspects of theory and experiment in the ethane-methyl radical system int. J. Chem. Kinetics 3 105-25... 

Only 20—40% of the HNO is converted ia the reactor to nitroparaffins. The remaining HNO produces mainly nitrogen oxides (and mainly NO) and acts primarily as an oxidising agent. Conversions of HNO to nitroparaffins are up to about 20% when methane is nitrated. Conversions are, however, often ia the 36—40% range for nitrations of propane and / -butane. These differences ia HNO conversions are explained by the types of C—H bonds ia the paraffins. Only primary C—H bonds exist ia methane and ethane. In propane and / -butane, both primary and secondary C—H bonds exist. Secondary C—H bonds are considerably weaker than primary C—H bonds. The kinetics of reaction 6 (a desired reaction for production of nitroparaffins) are hence considerably higher for both propane and / -butane as compared to methane and ethane. Experimental results also iadicate for propane nitration that more 2-nitropropane [79-46-9] is produced than 1-nitropropane [108-03-2]. Obviously the hydroxyl radical attacks the secondary bonds preferentially even though there are more primary bonds than secondary bonds. 

An appreciation of statistical results can be gained from a study conducted to support the first application of computer control for an ethylene oxide production unit at Union Carbide Corporation in 1958. For the above purpose, twenty years of production experience with many units was correlated by excellent statisticians who had no regard for kinetics or chemistry. In spite of this, they did excellent, although entirely empirical work. One statement they made was ... [ethane has a significant effect on ethylene oxide production.] This was rejected by most technical people because it did not appear to make any sense ethane did not react, did not chemisorb, and went through the reactor unchanged. 

Englezos, P., Kalogerakis, N., Dholababhai, P.D. and Bishnoi, P.R., 1987a. Kinetics of fonuation of methane and ethane gas hydrates. Chemical Engineering Science, 42(11), 2647-2658. 

Bowden has studied the application of the Hammett equation to the kinetics of the reaction of c/s-3-substituted acrylic acids with diphenyldiazom ethane (59) and with methanol (69) and the rates of alkaline hydrolysis of c -3-substituted methyl acrylates (69). The sets studied are reported in Table XII. Results of the... 

The stoichiometry of the reduction by Fe(ll) of cumene hydroperoxide is 1 1 (in contrast to reduction of H2O2) but the ratio A[Fe(II)]/A[ROOH] increases greatly in the presence of oxygen. The Arrhenius parameters for reduction of this and related hydroperoxides are quite similar to those of the Fenton reaction (Table 21). The production of acetophenone and ethane in high yield and the simple, second-order kinetics are consistent with the scheme... 

The above described experiments over atomically clean single crystal catalysts have been extended to studies of the kinetics of various catalytic reactions over chemically modified catalysts. Examples are recent studies Into the nature of poisoning by sulfur of the catalytic activity of nickel, ruthenium, and rhodium toward methana-tlon of CO (11,12) and CO2 (15). ethane (12) and cyclopropane (20) hydrogenolysls, and ethylene hydrogenation (21). 

Song H, ER Carraway (2005) Reduction of chlorinated ethanes by nanosized zero-valent iron kinetics, pathways, and effect of reaction conditions. Environ Sci Technol 39 6237-6245. 

Figure 4. Effect of methane conversion for 1=5 mA on ethylene, ethane and total Cg hydrocarbon selectivity and yield. Lines from kinetic model discussed below. Solid lines CgH j and C2Hg Dashed lines C2...

While alkane metathesis is noteworthy, it affords lower homologues and especially methane, which cannot be used easily as a building block for basic chemicals. The reverse reaction, however, which would incorporate methane, would be much more valuable. Nonetheless, the free energy of this reaction is positive, and it is 8.2 kj/mol at 150 °C, which corresponds to an equihbrium conversion of 13%. On the other hand, thermodynamic calculation predicts that the conversion can be increased to 98% for a methane/propane ratio of 1250. The temperature and the contact time are also important parameters (kinetic), and optimal experimental conditions for a reaction carried in a continuous flow tubiflar reactor are as follows 300 mg of [(= SiO)2Ta - H], 1250/1 methane/propane mixture. Flow =1.5 mL/min, P = 50 bars and T = 250 °C [105]. After 1000 min, the steady state is reached, and 1.88 moles of ethane are produced per mole of propane consmned, which corresponds to a selectivity of 96% selectivity in the cross-metathesis reaction (Fig. 4). The overall reaction provides a route to the direct transformation of methane into more valuable hydrocarbon materials. 

Table 5. Ethane hydrogenolysis reaction rates and kinetic parameters for both series of Pt/SBA-15 catalysts [13,16].

A mechanistic model for the kinetics of gas hydrate formation was proposed by Englezos et al. (1987). The model contains one adjustable parameter for each gas hydrate forming substance. The parameters for methane and ethane were determined from experimental data in a semi-batch agitated gas-liquid vessel. During a typical experiment in such a vessel one monitors the rate of methane or ethane gas consumption, the temperature and the pressure. Gas hydrate formation is a crystallization process but the fact that it occurs from a gas-liquid system under pressure makes it difficult to measure and monitor in situ the particle size and particle size distribution as well as the concentration of the methane or ethane in the water phase. 

The experiments were conducted at four different temperatures for each gas. At each temperature experiments were performed at different pressures. A total of 14 and 11 experiments were performed for methane and ethane respectively. Based on crystallization theory, and the two film theory for gas-liquid mass transfer Englezos et al. (1987) formulated five differential equations to describe the kinetics of hydrate formation in the vessel and the associate mass transfer rates. The governing ODEs are given next. 

The first reported work on the kinetics of hydrogenolysis reactions of simple hydrocarbons appears to be that of Taylor and associates at Princeton (2-4, 14, 15), primarily on the hydrogenolysis of ethane to methane. The studies were conducted on nickel, cobalt, and iron catalysts. More recently, extensive studies on ethane hydrogenolysis kinetics have been conducted on all the group VIII metals and on certain other metals as well (16,28-83). 

Kinetic Parameters for Ethane Hydrogenolysis on Silica-Supported Metals (16)... 

Here Pe and pH are the partial pressures of ethane and hydrogen, respectively, and the parameter a is equal to (6 — x)/2. This analysis was subsequently generalized to include cases in which equilibrium is not established between adsorbed C2H and gas phase ethane (16). Provided that surface coverage by adsorbed species is low, and that equilibrium is maintained between the surface species C2H5 and C2Hx, and H2 in the gas phase, a kinetic analysis leads to the rate expression... 

In applying the foregoing kinetic analysis to data on ethane hydro-genolysis on the group VIII metals, one finds for most of the metals that the value of x in C2Hz is equal to zero, i.e., the surface intermediate is a C2 species which is totally devoid of hydrogen (16). This conclusion does not conflict with known facts. However, a value of zero for x for most of the... 

Wallington, T.J., Neuman, D.M., Kurylo, M.J. (1987) Kinetics of the gas phase reaction of hydroxyl radicals with ethane, benzene, and a series of halogenated benzenes over the temperature range 234 -38 K. Int. J. Chem. Kinet. 19, 725-739. 

The rate of dissociation has been measured by oxygen uptake in the presence of an inhibitor of chain reactions as in the case of hexaaryl-ethanes. Since the uptake of oxygen obeys the same kinetic law, it is a reasonable extrapolation to suppose that here too the rate-determining step is a dissociation into radicals. When one of the phenyl groups in triphenylmethyl is replaced by a cyclohexyl group, the rate of dissociation of the ethane is reduced by a factor of 170.38 Some dissociation rate parameters are given in Tables III A and B. 

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