Catalytic evaluation of metal azolate framework-6 in pristine and metal doped modes in upgrading heavy residual fuel oil

Abstract

Despite the attracted widespread attention to the metal organic frameworks (MOFs) as advanced materials, they have not been inspected as catalytic additive in upgrading heavy oil. Herein, MAF-6, a nominated member of MOF vast family with high hydrophobicity and large structural cavities of 18.4A° was examined in catalytic upgrading of heavy residual fuel oil in pristine and molybdenum-doped modes. Integration of the MOF matrice with molybdenum was implemented to impart additional catalytic properties leading to the further improvement in catalytic upgrading performance. Both synthesized pristine and in-situ Mo-doped MAF-6s were characterized by XRD, FESEM, N2 adsorption-desorption, elemental mapping, ICP, and Raman analyses. The outcomes confirmed the high purity, crystallinity and porosity of both catalysts and the successful positioning of phosphomolybdic acid entities throughout the Mo-doped MAF-6 skeleton. Introduction of a small dosage (0.7 wt %) of either catalyst to the heavy oil was able to reduce the gas evolution and coke formation albeit with similar product distribution in comparison with thermal upgrading. However, conducting the viscosity and asphaltene content measurements, CHNS, TGA and 1HNMR analyses on catalytically upgraded oils emerged qualitative differences. TGA results revealed that pristine and Mo-doped MAF-6s were able to produce 62 and 58.3 wt % light and middle distillates, respectively, compared to the thermal upgrading with 54.8 wt % yield. However, Mo-doped-MAF-6 acted more efficiently achieving deeper asphaltene conversion up to 54.6 % and more intense viscosity drop to 98 cSt versus thermal upgrading with 49 % asphaltene conversion and viscosity reduction to 157 cSt. Catalytic upgrading with MAF-6 also yielded a liquid with 128 cSt viscosity without any further asphalten reduction.