Oxidative Dehydrogenation of Ethane to Ethylene over V2O5/Al2O3 Catalysts: Effect of Source of Alumina on the Catalytic Performance

A series of V 2 O 5 /Al 2 O 3 catalysts with fixed V 2 O 5 content (10 wt %) but varying Al 2 O 3 supports were prepared by impregnation technique and tested for the oxidative dehydrogenation of ethane (ODHE) to ethylene in a fixed bed quartz reactor in the temperature range from 500 to 600 °C. The nature of alumina support applied had a significant influence on the catalytic performance. Among all alumina supports investigated, the high surface area γ-Al 2 O 3 (200–300 m 2 /g) supported V 2 O 5 catalyst showed the best performance in ODHE with selectivity to ethylene of ca. 45–50%. This result is mainly due to the high dispersion of vanadia species on the support surface. On the other hand, low surface area α-Al 2 O 3 (5 m 2 /g) and γ-Al 2 O 3 (<100 m 2 /g) supported catalysts exhibited much higher ethane conversion under the same reaction conditions, but they also exhibited low selectivity to ethylene because of the existence of larger V 2 O 5 crystallites. In addition, a structurally disordered γ-Al 2 O 3 (ca. 6 m 2 /g) containing a high proportion of penta-coordinated Al-sites was also included in the present study. Amazingly, this low surface area alumina supported V 2 O 5 catalyst displayed a good performance in ODHE. Such behavior can be ascribed mainly to the presence of the penta-coordinated Al surface sites acting as anchors for preferentially monomeric and oligomeric VO x species leading to a prime dispersion. Therefore, performance similar to that of the high surface area aluminas was reached.