Chemical and Physical Processes of Hydrocarbon Combustion: Chemical Processes

Abstract

An initial attempt at firmly establishing the interrelationship of vapor-phase partial oxidation processes to the associated process parameters has been undertaken. This has been specifically done for the oxidation of ethane in the presence or absence of a countercurrent rain of particulate solids which enable uniform and stable control of the extreme reaction heat. It has been shown that these systems are comprised of a coupled chemical and physical transport process. Part I of this two-part series deals with the chemical processes of ethane partial oxidation. A mechanism is developed on the bases of experimental data illustrating the effects of temperature, pressure, composition, and contact time in conjunction with estimated rate parameters. The mechanism has been found very effective in quantitatively correlating and predicting experimental behavior over substantial ranges of conditions using derived Arrhenius parameters which are consistent when compared with theoretical estimates.

Comparison of the surface and catalytic properties of rare earth‐promoted CaO catalysts in the oxidative coupling of methane

“…The observations are consistent with those reported in the literature over different catalyst systems 1, 13–20. The increase in the C 2 H 4 /C 2 H 6 product ratio with temperature suggests that the conversion of ethane (which is formed by coupling of methyl radicals21) to ethylene is favoured at higher temperatures. The increase in C 2 H 4 /C 2 H 6 ratio is expected, due to the decomposition of more ethyl radicals and/or thermal cracking of more ethane molecules at higher temperature, as follows: It may also be due to an increase in the rate of the following reaction: and due to the oxidative dehydrogenation of ethane on the catalyst's surface.…”

“…The increase in the C 2 H 4 /C 2 H 6 ratio as the CH 4 /O 2 ratio decreases is most probably because of the availability of oxygen at higher concentration for the following gas‐phase reactions involved in the formation of ethyl radicals and ethylene from ethane 21, 25 It may also be due to the increase in the rate of the gas‐phase reactions of ethyl radicals to ethylene [reaction (3)].…”

Chemical and Physical Processes of Hydrocarbon Combustion: Physical Processes

“…At this point, the effective bulk temperature reaches a minimum beyond which the effective bulk temperature will increase as particulate solids are further introduced into the reaction system. Based upon the experimentally observed temperature effects on ethane partial oxidation (Figures 1 and 2 of Geisbrecht and Daubert, 1975), the relations depicted in Figure 8 can be deduced. Since it is known that the effective bulk temperature is lower for any given average axial temperature in the controlled reaction system cross-plots may be made as in Figure 9.…”

“…A characteristic effect of particulate solids upon the conversion processes of paraffinic hydrocarbon partial oxidations consists of only a slight inhibiting effect at initial solids loading beyond which the conversion processes are strongly inhibited (Geisbrecht and Daubert, 1975).…”

Influence of precursors of Li2O and MgO on surface and catalytic properties of Li-promoted MgO in oxidative coupling of methane

“…The increase in the ethene/ethane product ratio with decreasing the CH 4 /O 2 feed ratio (or increasing the O 2 concentration in feed) is probably because of the availability of O 2 at higher concentration for the following gas phase reactions involved in the formation of ethyl radicals and ethylene from ethane 28. 29 …”