Anionic effect in hot surface combustions

The initial phase of hot surface catalyzed hydrocarbon oxidation is anionic and not free radical in character. In the initial phase, anionic oxygen species such as the free radical anion abstract a proton to form a caged carbanion and an hydroxyl free radical. Hydrocarbon free radical character in the oxidation sequence then occurs by electron transfer from the hydrocarbon carbanion to the caged hydroxyl radical. The formation of the carbanion determines the ultimate course of the overall oxidation reaction.;There are many factors contributing to concerns about these anomalies: (1) An inverse relationship in the correlations between ignition temperatures of and the identities of the hydrocarbon oxidation products. These correlations are entirely consistent with carbanion, but not free radical (or cationic, either) effects. (2) Surface effects are very important, with more anionic surfaces providing greater combustibility. (3) Isotope effects, previously described as being supportive of free radical pathways, are compatible also for anionic mechanisms, if it is assumed that carbanions form initially in a fast step and that these then convert to free radical intermediates in slower, rate determining steps. (4) a Combustion trends are consistent with the Seebeck effect (ease of electron migration in an unevenly heated area). The Seebeck effect governs the adsorption and availability of oxygen radical anions at the hot surfaces. Surfaces with negative Seebeck effects more easily inspire selective oxidations, by draining electron density from developing hot spots and thus requiring a higher temperature to effect ignition of impinged hydrocarbon fuels than is the case for positive Seebeck effect surfaces. Conclusively, Seebeck effects are the most important in initiation and control of combustion and fire. (5) EFM confirms increased electrostatic intensities at microscopic surface defects. (6) Previously unexplainable rapid moving incandescent transient "red spots" often appear to presage imminent outbreak of ignition across the surface fuel impinging on a hot surface. (7) Addition of polar compounds to fuel/air mixtures facilitate ignition. (8) We have found that negative electrostatic potential facilitates hot surface catalyzed oxidations.;These factors have a very significant impact on plastics engineering potentials and the petrochemical industry in general.