Reduction of nitrogen oxides by carbon monoxide over an iron oxide catalyst under dynamic conditions

Abstract

The reduction of NO and N 2 O by CO over a silica-supported iron oxide catalyst was investigated by the transient response method, with different initial oxidation states of the catalyst, i.e. completely reduced (Fe 3 O 4 ), or oxidised (Fe 2 O 3 ). The in¯uence of CO pre-adsorption was also studied. From the material balance on the gas phase species, it was shown that the composition of the catalyst changes during relaxation to steady-state. The degree of reduction of the catalyst at steady-state could thus be estimated. During the transient period, CO was shown to inhibit N 2 O as well as NO reductions by adsorption on reduced sites. The activity of the reduced catalyst was found to be substantially higher as compared to the oxidised catalyst for both reactions. On this basis, it was attempted to keep the catalyst in a reduced state by periodically reducing it with CO. As a result, a signi®cant increase in the performance of the reactor with respect to steady-state operation could be achieved for N 2 O reduction by CO. Finally, the dynamic behaviour of the N 2 O±CO and NO±CO reactions made it possible to evidence reaction steps, the occurrence of which could not be shown during our previous investigations on the separate interactions of the reactants with the catalyst. #

Mathematical modelling of the unsteady-state oxidation of nickel gauze catalysts

“…The activation energy of di usion (E di = 54 kJ=mol) is relatively close to values reported by Randall et al (1998) (60 kJ=mol) and Castel and Surman (1969) for activated di usion in Fe 2 O 3 . Furthermore, Al'kaeva, Andrushkevich, Ovsitser, and Sokolovskii (1995) reports a value of 68 kJ=mol for the activation energy for di usion in a alumina supported catalyst loaded with di erent metals (Mo, Bi, Fe, Co, Ni, K and Si).…”

“…The step-response method, which consists of the measurement of the response of a catalytic system on a step-wise change in the concentration of reactants, was chosen for the substantial amount of information that it provides (Kobayashi, 1982;Tamaru, 1983;Renken, 1993;Randall, Doepper, & Renken, 1998).…”

Investigations of the reduction of NO to N2 by reaction with Fe under fuel-rich and oxidative atmosphere

“…Notably, iron or its compounds (alloys, oxides) can be used for the de-NO x process in two types of methods: primary and secondary methods. The application of iron (or/and its alloys/oxides) as a catalyst (secondary measures) in a separate reactor (similar to the concept of selective catalytic reduction, SCR) has been previously proposed [40][41][42][43][44]. For example, Randall et al investigated the reduction of NO and N 2 O by CO over silica-supported iron oxide (Fe 2 O 3 or Fe 3 O 4 ) catalysts.…”

Application of Nanoparticle Iron Oxide in Cigarette for Simultaneous CO and NO Removal in the Mainstream Smoke

“…b) The reduced form of NANOCT® Fe 2 O 3 as a catalyst of 2CO + 2NO = 2CO 2 + N 2 reaction: As mentioned in the previous section, Fe 3 O 4 is known to be the active catalytic component for the CO + NO reaction (13). In Figure 9, the inlet gas consists of CO, NO but not O 2 .…”

“…Fe 3 O 4 , FeO, and Fe) could also be used to reduce NO in the mainstream smoke to N 2 . Fe 3 O 4 is known as the active component in iron oxide based catalyst for CO + NO reaction under oxygen deficient conditions (13). The reaction produces N 2 and CO 2 .…”