Self-sustained catalytic combustion of carbon monoxide ignited by dielectric barrier discharge

Abstract

This paper presents the results of a study of self-sustained catalytic combustion of CO ignited by dielectric barrier discharge (DBD) using Ce 0.5 Zr 0.5 O y /TiO 2 (CeZr/Ti), CuZr 0.25 O y /TiO 2 (CuZr/Ti), and CuCe 0.75 Zr 0.25 O y /TiO 2 (CuCeZr/Ti) catalysts. DBD excites and dissociates some of the reactant molecules in the gas phase. These are more easily adsorbed on the catalyst surface than are ground-state species, therefore induction begins at a lower background temperature than in thermal catalysis. CO is adsorbed on copper sites, therefore CeZr/Ti is inactive in CO ignition, but CuZr/Ti and CuCeZr/Ti achieve DBD ignition at 34 and 44 s, respectively, at a specific energy density (SED) of 1500 J/L. CO catalytic ignition by DBD involves two steps. The induction process is dominated by plasma catalysis. At the same SEDs, induction with CuCeZr/Ti begins earlier than those with CuZr/Ti, in good agreement with the reducibilities and oxygen-transfer properties of these catalysts. The ignition process is governed by thermal catalysis because the enhancement of external diffusion induced by increasing the temperature improves the reaction rate. CuZr/Ti provided more CO adsorption sites than did CuCeZr/Ti, contributing to shortening of the ignition delay.

Reaction mechanism and kinetics of CO oxidation over a CuO/Ce0.75Zr0.25O2-δ catalyst

“…Cu(NO 3 ) 2 ·3H 2 O, Ce(NO 3 ) 3 ·6H 2 O and Zr(NO 3 ) 4 ·5H 2 O were combined in a 4:3:1 M ratio and dissolved fully in 70 mL of ethanol at 80°C. This Cu:Ce:Zr ratio was selected on the basis of our previous study according to its good redox capability and oxygen storage capacity for CO oxidation [22,23]. Then, 0.24 mol/L of an oxalic acid solution was used as a pore former and was added quickly to the aforementioned nitrate solution with stirring to evaporate ethanol and to fully dissolve until a gel was formed at 80°C over nearly 6 h. After aging at room temperature for approximately 48 h, the gel was dried at 105°C for 12 h and then calcined in air at 550°C for 2 h.…”

Catalytic self-sustained combustion of toluene and reaction pathway over CuxMn1-xCe0.75Zr0.25/TiO2 catalysts

“…Yang [2] and Scarpa [4] found that alkanes including methane, propane and n-octane could achieve self-sustained combustion successively over Pt-based catalyst supported ZSM-5 or γ-Al 2 O 3 with relatively lower concentration. In addition, the self-sustained combustion can be obtained by CO → CO 2 exothermic reaction over the CuCe/ZSM-5 and CuCe 0.75 Zr 0.25 /TiO 2 catalysts in our previous studies [5,6].…”

Enhanced removal of toluene by dielectric barrier discharge coupling with Cu-Ce-Zr supported ZSM-5/TiO2/Al2O3

“…For instance, with discharge power increases from 25 to 42 W, toluene removal for CuCeZr/T increases from 98.2% to 100%, while the corresponding CO 2 selectivity increases from 64.8% to 94.2%. On the one hand, the background temperature further increases in the reactor through joule heating, dielectric loss, and gas heating in the plasma channel with the migration of electrons and ions [20], and it can activate the catalyst owing to the thermal chemistry. On the other hand, with the increase of input discharge power, plasma can activate catalyst gradually by changing the physicochemical properties of the catalyst, formation of hot spots, lowering the activation barrier and changing the reaction pathways, hence the catalyst's role becomes much more important or dominant.…”