A Kinetic Study of Methane Partial Oxidation over Fe‐ZSM‐5 Using N₂O as an Oxidant

Abstract

Catalytic methane oxidation using N O was investigated at 300 °C over Fe-ZSM-5. This reaction rapidly produces coke (retained organic species), and causes catalyst fouling. The introduction of water into the feed-stream resulted in a significant decrease in the coke selectivity and an increase in the selectivity to the desired product, methanol, from ca. 1 % up to 16 %. A detailed investigation was carried out to determine the fundamental effect of water on the reaction pathway and catalyst stability. The delplot technique was utilised to identify primary and secondary reaction products. This kinetic study suggests that observed gas phase products (CO, CO , CH OH, C H and C H ) form as primary products whilst coke is a secondary product. Dimethyl ether was not detected, however we consider that the formation of C products are likely to be due to an initial condensation of methanol within the pores of the zeolite and hence considered pseudo-primary products. According to a second order delplot analysis, coke is considered a secondary product and its formation correlates with CH OH formation. Control experiments in the absence of methane revealed that the rate of N O decomposition is similar to that of the full reaction mixture, indicating that the loss of active alpha-oxygen sites is the likely cause of the decrease in activity observed and water does not inhibit this process.

Photocatalytic Oxidation of Small Molecular Hydrocarbons over ZnO Nanostructures: The Difference between Methane and Ethylene and the Impact of Polar and Nonpolar Facets

“…Comparatively, ZnO nanorods under the same conditions show poor rate in the photocatalytic oxidation of methane. The difference in their photocatalytic activities may arise from the difference in the number of active sites in light of having comparable surface areas. − Thermodynamically, polar facets on account of high energy are much reactive than nonpolar facets and as such may induce polarity in a stable and highly symmetrical molecule like methane. ,− …”

Direct Methane Conversion under Mild Condition by Thermo-, Electro-, or Photocatalysis

“…73 For the first time, Narsimhan et al 72 reported the direct catalytic methane oxidation with oxygen or water at a reaction temperature of 210 C. The effect of water stream on the direct methane oxidation over Fe-ZSM-5 was investigated using N 2 O as oxidant. 74 Interestingly, the introduction of stream enhanced the desired product selectivity of methanol from 1% to 16% and inhibited coke formation. The presence of water in the reaction environment favors methanol desorption and inhibits coke formation via the competitive adsorption of water.…”

Investigating the Influence of Fe Speciation on N2O Decomposition Over Fe–ZSM-5 Catalysts

“…Here, 0.4 wt% Fe–ZSM-5 (23) was identified as a suitable catalyst formulation for acid washing, due to the presence of extra-framework ɑ-Fe species and minor levels of spectator Fe x O y nano-particulates and clusters. Previous work within the group has shown that it is difficult to distinguish between the Fe species present at higher weight loadings, therefore lower weight loadings were selected for acid washing to enable changes to be noted [82, 83]. After acid washing the calcined catalyst, ICP-OES analysis of the digested samples revealed that the weight loading had reduced to 0.16%.…”