Ethane dehydrogenation over Cr/ZSM-5: characterization of active sites through probe molecule adsorption FTIR

Abstract

<p>Dispersed Cr species supported on zeolite ZSM-5 were investigated in the context of catalytic ethane dehydrogenation. Probe molecule FTIR and XANES were used to characterize the nature of Cr sites...</p>

Stable Cr-MFI Catalysts for the Nonoxidative Dehydrogenation of Ethane: Catalytic Performance and Nature of the Active Sites

“…The nonreduced sample shows a wide variety of peaks that can be attributed to multiple Cr-nitrosyl complexes at different oxidation states (Figure S19a). The results are in line with the XAS data where Cr­(VI), Cr­(III), and Cr­(II) were identified in the early stages of the thermal treatment (Figure a). After the introduction of H 2 at 575 °C, most of these bands disappear, and only the ones at 1613 and 1814 cm –1 remain (Figure S19b).…”

“…BET analysis of the 0.8Cr/MFI catalyst after second catalytic runs (without calcination) shows a slight decrease in micropore area and volume (Table S1), suggesting that the pore structure is preserved very well, which is one of the main reasons for its excellent regeneration ability. A recently reported similar catalytic system based on Cr/ZSM-5 claimed that the framework Al sites are necessary to stabilize the active Cr sites against sintering . Mimura et al reported a similar system under nonoxidative conditions but the C 2 H 6 conversion level dropped after only a few hours because of coke formation .…”

“…The associated disadvantage is the decrease in activity due to the poison effect of these base promoters that sometimes decrease the reducibility of Cr. A very recent study on Cr/ZSM-5 catalysts showed that the zeolite framework Al sites are crucial for the stabilization of active Cr sites during EDH . However, the catalyst was observed to deactivate very fast with time even after neutralizing the acidity by Ca-doping.…”

“…A very recent study on Cr/ZSM-5 catalysts showed that the zeolite framework Al sites are crucial for the stabilization of active Cr sites during EDH. 10 However, the catalyst was observed to deactivate very fast with time even after neutralizing the acidity by Ca-doping. Therefore, the earlier reported works clearly indicate that an ideal dehydrogenation catalyst should avoid the use of acidic supports.…”

Enhanced Catalytic Performance of Fe‐containing HZSM‐5 for Ethane Non‐Oxidative Dehydrogenation via Hydrothermal Post‐Treatment

“…Currently, non‐oxidative dehydrogenation catalyst of light alkanes, such as ethane and propane, mainly contains Pt−M (M=Sn, Zn, Ga, In) [6d,l,7] and CrO x [6a–c,g–j,m] supported catalyst, as the most extensively studied systems owing to its high activity. Nevertheless, owing to environmentally unfriendly CrO x ‐based catalyst, and high‐cost as well as easily agglomeration of Pt−M catalyst, it is urgent to develop highly active, selective as well as coke‐resistant catalysts.…”