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Catalysts of general formula, MoVAlO x were prepared with the initial elemental composition of 1:0.34:0.167 (Mo:V:Al) at a pH value in the range of 1-4. The elemental analysis showed that the final composition of the catalysts is pH dependant. The performance of the catalysts was tested for selective oxidation of ethane to give ethylene and acetic acid. While all of them were active for ethane oxidation with a moderate conversion, the catalyst prepared at pH 2 showed a highest activity with 23% ethane conversion and a combined selectivity of 80.6% to ethylene and acetic acid. The catalyst prepared at pH 4 was least selective to ethylene and acetic acid. Various techniques like powder XRD, SEM, Raman, UV-Vis and EPR were used to characterize the catalysts and to identify the active phases responsible for the selective oxidation of ethane. The powder XRD data showed that the catalysts prepared at pH 1 and 2 contain mainly of MoO 3 and MoV 2 O 8 along with traces of Mo 4 O 11 . The amount of MoO 3 was slightly higher in the catalyst prepared at pH 1. However, the catalyst prepared at pH 3 contains mainly of MoV 2 O 8 with no trace of MoO 3 . The catalyst prepared at pH 4 showed V 2 O 5 as the major phase along with MoVAlO 4 phase. The Raman data corroborated the XRD results. EPR and UV-Vis studies indicated the presence of traces of V 4+ in pH 1 and 2 catalysts and significant amount of Mo 5+ in all the catalysts. Thus, the high activity and selectivity to ethylene and acetic acid are attributed to the presence of MoV 2 O 8 phase and other reduced species like Mo 4 O 11 phase supported on MoO 3 . The presence of V and Mo ions in a partially reduced form seems to play a crucial role in the selective oxidation of ethane.

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