Nickel aluminate (NiAl2O4) nano and microstructures were synthesized by both microwave combustion method (MCM) and conventional combustion method (CCM) using aloe vera as the plant extract. The synthesized NiAl2O4 nanoparticles were characterized by X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR) studies, high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) studies. The XRD results confirmed the formation of a cubic NiAl 2O4. The formation of NiAl2O4 nano and microstructures were confirmed by HR-SEM and HR-TEM. The optical absorption and photoluminescence emissions were determined by DRS and PL spectra, respectively. The effect of catalyst and solvent on the catalytic oxidation of benzyl alcohol using the NiAl2O4 catalyst prepared by both CCM and MCM was also investigated. © 2014 Elsevier B.V.