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Partially or fully regenerated catalytic cracking catalysts were prepared by gasifying the coke deposited on coked catalysts with a gaseous mixture of oxygen and steam in a fixed fluidized bed(FFB).The resultant samples were characterized by different methods such as the nitrogen adsorption-desorption analysis,the X-ray diffractometry,the infrared spectroscopy,the ammonia temperature-programmed desorption(NH_3-TPD) method, the X-ray fluorescence(XRF) analysis,the transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM-EDX),the thermal-gravimetric analysis(TGA) and the differential thermal analysis(DTA).The results showed that exposure of catalyst to steam for about 10 minutes at temperature≥800℃could not cause too much destruction of the catalysts,and an amount of coke equating to about 0.27 m%was enough to block approximately all acid sites in micro-pores of the zeolite catalyst.Coke didn’t show equal reactivity during coke burning-off that could be accelerated by the catalytic action of nearby metal atoms.However,when the carbon content on the catalyst reached about 2.44 m%,the catalytic action of metals on the catalyst was not evident.The severe thermal and hydrothermal environment during exposure of the catalyst to steam at a temperature in the range of about 860-880℃for 30 minutes could lead to collapse of pore structure and transformation of crystal phase and consequently decrease of the surface area and acid amount on the catalyst.
Partially or fully regenerated catalytic cracking catalysts were prepared by gasifying the coke deposited on coked catalysts with a gaseous mixture of oxygen and steam in a fixed fluidized bed (FFB). The resultant samples were characterized by different methods such as the nitrogen adsorption-desorption analysis , the X-ray diffractometry, the infrared spectroscopy, the ammonia temperature-programmed desorption (NH_3-TPD) method, the X-ray fluorescence (XRF) analysis, the transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM- EDX) , the thermal-gravimetric analysis (TGA) and the differential thermal analysis (DTA). The results showed that exposure of catalyst to steam for about 10 minutes at temperature ≧ 800 ° C could not cause too much destruction of the catalysts, and an amount of coke equating to about 0.27 m% was enough to block approximately all acid sites in micro-pores of the zeolite catalyst. Coke did not show equal reactivity during coke burning-off that could be be accelera ted by the catalytic action of nearby metal atoms. When, when the carbon content on the catalyst reaches about 2.44 m%, the catalytic action of metals on the catalyst was not evident. severe heat and hydrothermal environment during exposure of the catalyst to steam at a temperature in the range of about 860-880 ° C for 30 minutes could lead to collapse of pore structure and transformation of crystal phase and decreased decrease of the surface area and acid amount on the catalyst.