Catalytic selective ethane dehydrogenation at low-temperature with low coke formation

Abstract

Catalytic ethane dehydrogenation (EDH) was investigated to improve the efficient production of ethylene, an extremely important chemical feedstock. The perovskite oxide YCrO₃ was found to be more suitable than earlier reported catalysts because it exhibits greater activity and C₂H₄ selectivity (94.3%) in the presence of steam at 973 K. This catalyst shows the highest activity than ever under kinetic conditions, and shows very high ethane conversion under integral reaction conditions. Comparison with EDH performance under conditions without steam revealed that steam plays an important role in stabilizing the high activity. Raman spectra of spent catalysts indicated that steam prevents coke formation, which is responsible for deactivating YCrO₃. Transmission IR and XPS measurements also revealed a mechanism by which H₂O forms surface oxygen species on YCrO₃, consequently removing C₂H₆-derived coke precursors rapidly and inhibiting coke accumulation.

Fig. 1. C₂H₄ formation rate and C₂H₄ selectivity at 973 K over Cr-based and Y-based perovskites, and La_0.7Ba_0.3MnO_3−δ (LBMO).

Fig. 2. Time course of H₂¹⁸O formation in SSITKA at 973 K over YCrO₃ and La_0.7Ba_0.3MnO_3−δ.

Fig. 3. Time course of the C₂H₄ formation rate at 973 K over YCrO₃ under wet and dry atmospheres.

Fig. 4. Raman spectra of fresh and spent YCrO₃ (a) and time course of C₂H₄ formation rate during activity tests with H₂O treatment (b).

Fig. 5. In situ IR spectra for YCrO₃ under dry atmosphere (a), wet atmosphere (b), and during removal of coke precursors by steam (c and d).

Fig. 6. Deconvoluted XP spectra of O 1s region for YCrO₃ after dry test, wet test, and H₂O treatment following the dry test.

Fig. 7. Schematic image showing the reaction mechanism.