Synthesis and characterization of mesoporous aluminas with different pore sizes: Application in NiMo supported catalyst for hydrotreating of heavy gas oil

The mesoporous alumina materials having different textural properties were synthesized by modifying the procedures mentioned in literature. Pluronic P-123 was used as structure directing agent (SDA) and aluminum isopropoxide was used as precursor for aluminum. The materials were characterized using N-2 adsorption-desorption isotherms (BET), X-ray diffraction, FTIR and high resolution-TEM (HRTEM). BET, XRD and HRTEM analyses had confirmed the synthesis of mesoporous aluminas with different textural characteristics. The synthesized mesoporous aluminas were utilized as a support material for NiMo catalyst for hydrotreating of oil sands bitumen derived heavy gas oil, in a fixed bed reactor at industrial conditions. The catalytic activity was measured in terms of hydrodesulfurization (HDS) and hydrodenitrogenation (HDN). The catalysts were characterized by BET, XRD, FUR, Raman, CO-chemisorption, HRTEM, TPD and TPR. The activity study for conventional NiMo/gamma-Al2O3 was also performed for comparison. Six types of mesoporous aluminas and corresponding catalysts were synthesized based on HNO3/H2O ratio varying from 0 to 2. It was observed that with increase in water content the surface area, pore volume and pore diameter of mesoporous aluminas increase. Moreover, the structure changes form ordered hexagonal to wormlike/sponge-like and fibular and then to corrugated platelets/rod like structures with increase in water content. However, the morphology of structure was changed after loading of active metals and the catalytic active follows the order NiMo/Meso-Al-0.6>NiMo/Meso-Al-0.4>NiMo/Meso-Al-2 approximate to NiMo/Meso-Al-0.2 > NiMo/Meso-Al-0> NiMo/gamma-Al2O3 > NiMo/Meso-Al-1.25. The highest activity shown by catalyst NiMo/Meso-Al-0.6 could be assigned to (i) its higher pore volume and surface area, (ii) highest metal dispersion, (iii) more number of weak acidic sites and (iv) lower Mo reduction temperatures. (C) 2014 Elsevier B.V. All rights reserved.