Propylene epoxidation in the gas-phase oxidation of propane-propylene mixtures

Oxidation of propene in the gas phase

“…The reaction of allyl with oxygen will always be much faster than with propene. However, as pointed out by Grigoryan et al, [7], the allylperoxy radical will tend to decompose back to allyl and oxygen without further reaction, above its ceiling temperature (301, allowing allyl addition to propene to become significant. Indeed any radical that adds to propene in preference to reaction with oxygen or abstraction from the alkene (or other product) can undergo a series of reactions similar to those described for OH addition, giving propene oxide, acetaldehyde, and formaldehyde as molecular products, e.g.…”

“…Grigoryan et al [7] discussed the case of X = H , for which this radical addition mechanism is plausible, in that hydrogen will add to propene faster than to oxygen in fuel-rich experiments. However for the scheme in the Appendix, there is no significant source of hydrogen atoms, so hydrogen atom addition to propene is not considered to be significant for the experiments reported here.…”

“…The smaller hydrocarbons (for example, methane, ethane, ethene, and ethyne) as well as larger homologues, have been reported as products above ca. 630 K [7,121 and in significant amounts above 900 K [9, Surprisingly, in several studies, the presence or absence of propene oxide has not been the center of attention and it was not observed at all in some of the most detailed experiments (for example 4,6), although it was detected in an early analytical study [14]. Nevertheless it has more recently been found that, under pressure, large concentrations of the epoxide are formed below 670 K [XI. For this work, a series of low temperature experiments (505-549 K), with fuel-rich mixtures were conducted to gain an understanding of the chemistry involved in the formation of propene oxide during propene oxidation, and to examine the variation in epoxide yield with experimental parameters (eg., temperature, pressure etc.…”

“…550 K) and higher (ca. 750 K) temperatures (for example, , a negative temperature coefficient [3,6,8,10,111, and the characteristic autocatalytic behavior of hydrocarbon oxidation [2,7,9,111.…”

Epoxidation of Alkenes by Peroxyl Radicals in the Gas Phase: Structure−Activity Relationships

“…Arsentiev et al , monitored the total peroxyl radical concentration in the gas phase by ESR during the autoxidation of ethene and propene. The rates of production of the epoxides (determined by GC analysis) were found to correlate well with the product of the peroxyl radical and alkene concentrations and were used to derive (effectively, species averaged) rate constants for the epoxidation of the alkene by the peroxyl radicals present.…”