Ignition Catalyzed by Unsupported Metal Nanoparticles

Abstract

The short residence times available in supersonic combustion require some pre-reaction under mixing-controlledrich conditions and/or methods to lower the reaction temperature for auto-ignition. Adding catalysts could be such an option to achieve this objective. Catalytic ignition of toluene over the surfaces of in situ-generated free metal (Fe and Ni) nanoparticles was investigated experimentally in an aerosol reactor. The metal nanoparticles (Fe and Ni) were generated by decomposition of the corresponding metal carbonyls. Gas-phase (aerosol) size distributions along with transmission electron microscopy used to characterize the morphology of catalyst particles at different temperatures are presented. The effluent gas product and the fuel ignition temperature were determined by mass spectrometry. In comparison to non-catalytic homogeneous ignition, the addition of metal nanoparticles can lower the ignition temperature by as much as 150 °C under rich conditions but had little effect under lean conditions. Iron was found to be a more active catalyst than nickel. Inspection of the catalyst product indicated that sintering was occurring at relatively low temperatures presumably as a result of the exothermic reaction on the particle surface. Turnover frequency as high as 80 s À1 was achieved, implying a greater catalyst efficiency than commonly found for substrate-stabilized catalysts.

Dust Explosion of Carbon Nanofibers Promoted by Iron Nanoparticles

“…In addition, several studies discussed the special effect of iron nanoparticles (Fe-NPs): the phenomena of camera flash light igniting SWCNTs was attributed to the pyrophoric nature of fine Fe particles within the nanotube bundles; 8 iron (on the surface) helps catalyze the boron (core) oxidation at room temperature; 26 the addition of metal nanoparticles (either Ni or Fe) can lower the ignition temperature of aerosols by as much as 150°C. 27 One possible explanation is illustrated in Figure 7 regarding the Fe-NPs effect on triggering the ignition of CNFs. Figure 7 shows the radiation energy path for both conventional bulky particles and nanofiber agglomerates.…”

“…This assumption is of very likely since previous experience showed that CNTs with iron can be ignited around 300 °C in air while pure CNTs cannot. In addition, several studies discussed the special effect of iron nanoparticles (Fe-NPs): the phenomena of camera flash light igniting SWCNTs was attributed to the pyrophoric nature of fine Fe particles within the nanotube bundles; iron (on the surface) helps catalyze the boron (core) oxidation at room temperature; the addition of metal nanoparticles (either Ni or Fe) can lower the ignition temperature of aerosols by as much as 150 °C …”

Experimental Investigation of the Settling Characteristics of Carbon and Metal Oxide Nanofuels

“…Metal, metal oxide and carbon-based nanoparticles have been tested with an everincreasing number of hydrocarbon-based base fuels. Researchers have investigated the effect of metal nanomaterials such as iron [11][12], boron [13], nickel [14] on liquid fuel combustion properties. The effect of metal oxides such magnesium oxide [15], alumina [16], zinc oxide [17], and cerium oxide [18] has also been examined.…”

Catalytic combustion of methane, methanol, and ethanol in microscale combustors with Pt/ZSM-5 packed beds

“…It was demonstrated that methanol-air could self-ignite at room temperature with catalyst of platinum nanoparticles [13]. The high surface energy of nanometer-sized catalysts contributed to their high catalyst activity [14][15][16]. Most reports on micro combustion of methanol and ethanol were focused on the integrated reforming process including a catalytic combustor [17][18][19][20].…”