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

Abstract

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 N2 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, FTIR, Raman, CO-chemisorption, HRTEM, TPD and TPR. The activity study for conventional NiMo/γ-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≈NiMo/Meso-Al-0.2>NiMo/Meso-Al-0>NiMo/γ-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.