D8 focus advance diffractometer

Powder X-ray diffraction (XRD) patterns of the catalysts were recorded using a Bruker D8 Focus Advance diffractometer equipped with Lynx Eye detector with a Ni-filtered Cu Kα radiation source (λ = 1.5406 Å) in 2θ range of 0.6 to 2 with a step size of 0.01 and step time of 2 s. Fourier transformed infrared spectra (FT-IR) were recorded using a Bruker TENSOR 27 FT-IR spectrometer with 4 cm⁻¹ resolution and 100 scans in mid IR region (4000–600 cm⁻¹) employing KBr pellet technique. Nitrogen adsorption–desorption isotherms were measured at 77 K using Micromeritics 3Flex surface area analyzer, in which catalysts were outgassed at 300 °C for 6 h prior to the sample measurements. Helium was used as the carrier gas. Specific surface area was calculated using BET (Brunauer–Emmett–Teller) equation and pore-size distribution was obtained from desorption branch of the isotherm using BJH (Barrett–Joyner–Halenda) method. Total number of acids sites and acid strengths of the samples were determined by temperature programmed desorption of ammonia (NH₃-TPD) using an Altamira AMI-300 equipment. Samples were activated at 300 °C for 1 hour in helium flow. Later, they were cooled and maintained at 100 °C prior to their exposure to ammonia vapour followed by purging with helium for 30 min. The desorption of ammonia was carried out by heating the reactor up to 350 °C at a steady rate of 10 °C min⁻¹.