SURFACE EFFECTS IN THE UNINHIBITED AND THE INHIBITED PYROLYSES OF ISOMERIC HEXANES: PARTS I-III.n-HEXANE, 2-METHYL PENTANE, 3-METHYL PENTANE

Abstract

The rates of pyrolysis of n-hexane, 2-methyl pentane, and 3-methyl pentane decrease with increasi~lg S / V ratio in the pressure range of 15 to 90 mm a t temperatures around 520 "C. The partial pressure of nitric oxide required for maximum inhibition which appears to be independent of the hydrocarbon pressure and is approximately constant for all isomers, namely 12-14 mm, for hydrocarbon ranging from 50 to 100 111111, iricreases slightly with increasing S / V ratio. Nitric oxide affects the product distribution rnarl~edly. The simultaneous increase in the yield of C2H.i and decrease in the yield of C~H G with increasing S O pressure can be attributed to the set of competitive reactions CzI-1, + NO 4 C2H.I + HNO C?H; + RE1 + C?I-IG + R.Similarly, the slight decrease in the yield of C3Ms with increasing NO pressure can be accounted for by the competitionIncreased S / V ratios favor the formation of C~H G in both the ~~ninhibited and the inhibited pyrolyses, but has no effect on the yields of such products as CaHG, l-c.~Hs, and i-C.,I-Is. T h e analytical balance beco~lles less co~llplete a t higher NO pressures for the inhibited decomposition, which can be attributed to the formation of some nitrogen-containing compounds undetectable by the analytical nlethods used. bIechanisms are proposed accou~iti~ig clualitatively for the products of the uninhibited and the inhibited pyrolyses.

Surface Effects in the Uninhibited and the Inhibited Pyrolyses of Isomeric Hexanes: Part V. 2,2-Dimethyl Butane (Neohexane)

“…2) Nitric oxide reduces the rate of decomposition by about 55%. The reduction in rate is more gradual in comparison to the less branched isomeric hexanes (10). The NO pressure required for maximum inhibition is the same, namely 12-14 mm, for hydrocarbon pressures ranging from 50 to 120 mm (Fig.…”

“…I). However, the reduction in rate due to the packing is less marked than that of the less branched isomeric hexanes (10).…”

“…T h e net reduction in rate due to packing is less marked than that for the less branched isomeric hexanes (10). From the relative adsorption of NO and the isomeric hexanes on quartz wool i t appears that neohexane is adsorbed more than the less branched isomers.…”

“…T h e initiation processes can take place in both phases (10). T h e net reduction in rate due to packing is less marked than that for the less branched isomeric hexanes (10).…”

“…However, this reduction is more gradual than it was in the less isomeric hexanes (10). Nitric oxide cannot expel1 neohexane molecules from the active sites of the wall efficiently and therefore it is expected that NO will suppress the heterogeneous initiation slightly.…”