Abstract:

A study was conducted on the modification of alumina oxide to meet the requirements of catalytic cracking heavy oil conversion and reducing coke yield.Al₂O₃-B and Al₂O₃-P were obtained by impregnation modification of pseudo boehmite with boric acid and diammonium hydrogen phosphate.The crystal structure，pore structure，acid amount，and acid strength of the samples were characterized using techniques such as X-ray diffraction（XRD），N₂ adsorption-desorption，NH₃-temperature-programmed desorption（NH₃-TPD），and pyridine-infrared spectroscopy（Py-IR）.The results showed that compared with unmodified Al₂O₃-0，although Al₂O₃-B and Al₂O₃-P exhibited reduced pore volume，specific surface area，and smaller most probable pore size，their thermal stability was improved.After calcination at 950 ℃，the specific surface area retention rate was increased by more than 15%.The acid amount was increased for Al₂O₃-B but decreased for Al₂O₃-P，while the acid strength of both Al₂O₃-B andAl₂O₃-P were decreased.The catalytic performance of fluid catalytic cracking（FCC） catalysts prepared using Al₂O₃-0，Al₂O₃-B，and Al₂O₃-P was evaluated.Compared with CAT-1，CAT-2 showed a 0.92% decrease in heavy oil yield，a 0.55% reduction in coke yield，and a 1.46% increase in total liquid yield.In contrast，CAT-3 exhibited a 0.32% increase in heavy oil yield，a 0.78% decrease in coke yield，and a 0.48% rise in total liquid yield compared to CAT-1.Compared with CAT-1，CAT-2 and CAT-3 demonstrated stronger heavy oil conversion ability and lower coke yield.Furthermore，the Al₂O₃-B-based catalyst provided a higher total liquid yield than the Al₂O₃-P.

Key words: aluminum oxide, boron modification, phosphorus modification, catalytic cracking, coke