Application of VOx/Al2O3 and Fe2(MoO4)3–MoO3 catalysts for the selective reaction and detection of ethanol in multi-component hydrocarbon fuel mixtures

This work presents for the first time the development of a selective catalyst to enable selective hydrocarbon detection when coupled with a microcalorimetric sensor. Specifically, the application of VOx/Al2O3 and Fe2(MoO4)3–MoO3 catalysts as selective sensor substrates for thermal microsensor detection of ethanol in automotive fuel is described. At 453 K, 8VOx/Al2O3 (monolayer surface density of ∼8 V/nm2) and Fe2(MoO4)3–MoO3 (Mo:Fe = 1.9) catalysts convert ethanol towards one highly exothermic oxidative dehydrogenation product, acetaldehyde, with selectivities of 95% and 98%, respectively. For 8VOx/Al2O3 and Fe2(MoO4)3–MoO3, rates at 453 K are 1.3 × 10−6 and 3.4 × 10−6 mol ethanol converted/g s, respectively, and they are independent of ethanol concentration from 0.2 to 2.0 kPa ethanol. At 453 K, these catalysts provide excellent reaction selectivity towards all classes of hydrocarbons present in automotive fuels. No reaction is observed for common constituents of gasoline such as benzene, toluene, 1-pentene, 1-hexene, 2-methyl butane, butyraldehyde, and 2-methyl pentane at 453 K in binary or ternary mixtures with ethanol. All of these non-target hydrocarbons except butyraldehyde also have no impact on the ethanol partial oxidation rate or selectivity. MTBE proves to be active at 453 K over both 8VOx/Al2O3 and Fe2(MoO4)3–MoO3. Both MTBE and butyraldehyde decrease the ethanol reaction rate due to competitive surface adsorption on active sites but have no impact on the selectivity of the ethanol partial oxidation reaction.

Figure optionsDownload as PowerPoint slideResearch highlights▶ Selective reaction of ethanol in typical gasoline constituents is possible. ▶ Metal oxides provide chemical specificity for electrothermal ethanol detection. ▶ Catalyst and operating temperature selection are vital for catalytic sensor design.