Brönsted (B) and Lewis (L) acid sites were differentiated using pyridine as a probe by FT-IR spectrophotometer (Perkin Elmer, GX, USA) equipped with Diffuse Reflectance FT-IR (DRIFT) accessory (Graseby Specac, P/N 19900) and an automatic temperature controller (Graseby Specac, P/N 20130) as described earlier [32]. The quantification of B and L acid sites ratio (B/L) was done from the characteristic peak area of 1544 cm1 for B and 1443 cm1 for L at 150 C as well as by molar extinction coefficient method (using eB = 1.67 cm/lmol and eL = 2.22 cm/lmol) [33,34].