(647d) V2O5-Nb/La-Al2O3 Catalysts for Oxidative Dehydrogenation of Ethane to Ethylene

The aim of this study is to investigate oxidative dehydrogenation (ODH) of ethane to ethylene in absence of gas phase oxygen using multimetallic V₂O₅-Nb/La-Al₂O₃ catalysts. In the catalyst formulation, La is used to modify γ-Al₂O₃, stabilizing bulk phase transformation of γ-Al₂O₃. A small amount of Nb is used as a promoter of the main active V₂O₅ species.

Catalysts were prepared by using an incipient wetness technique. V₂O₅ was loaded on La modfied γ-Al₂O₃ (260 m²/g).  Before V₂O₅ loading the support γ-Al₂O₃ was modified with La. The prepared catalysts were characterized using various physicochemical techniques in order to understand the different aspects of their performances including the reducibility, oxygen carrying capacity, stability and phase transformation under repeated redox cycles.

Temperature programmed reduction (TPR) evaluation shows that Nb-V₂O₅/La-Al₂O₃ catalyst is very stable over repeated reduction and oxidation cycles. In each cycle the amount of hydrogen consumption remains stable approximately at 80 cc/g catalyst. XRD analysis indicates that V₂O₅ on catalysts is an amorphous phase up to 10 % V loading. The pulse chemisorption show a good metal dispersion on the La modified support.  SEM and EDX results reveal that La, Nb and V₂O₅ are present on the support surface as mono-vanadate and poly-vanadate in amorphous phase which further confirmed by XRD peak analysis.

The gas phase oxygen free ODH of ethane in the fluidized CREC Riser Simulator displays that approximately 30 % ethane conversion can be achieved in very short contact time reactions. The oxygen free (gas phase) ODH also found favorable to obtain high ethylene selectivity (upto 85 %). The Nb-V₂O₅/La-Al₂O₃ catalyst also shows stable performance in the repeated ODH-regeneration cycles which is consistent to cyclic TPR/TPO results.

Acknowledgement: We acknowledge the financial support by KACST research grant number ARP-30-252