36 for gas solid separation the separated flue gas departs from the regenerator via pipe line 15 and then is divided into two streams wherein one stream enters the turbine via pipe line 38 and the other stream is mixed with steam from pipe line 31 via pipe line 39 according to the requirements on the commercial catalytic cracking unit the aged catalyst is added into the regenerator 13 of the commercial catalytic cracking unit via pipeline 37 and the prevailing wind is fed into the regenerator 13 via pipe line 14 for regeneration of the catalyst fig4 is another schematic representation of the processing method for improving the selectivity of the catalytic cracking catalyst according to the present invention however the fresh catalyst ager is not restricted to being placed adjacent to the regenerator and the aged catalyst is not restricted to being recycled to the regenerator moreover the model and manner of the heat exchanger are not restricted to those as shown in the drawings a fresh catalyst ager i e a dense phase fluidized bed 32 u2033 may be placed adjacent to the regenerator 13 u2033 so as to introduce the hot catalyst in the regenerator 13 u2033 into the heat exchanger 40 u2033 of the dense phase fluidized bed 32 u2033 via pipe line 42 u2033 a fresh catalytic cracking catalyst is fed into the dense phase fluidized bed 32 u2033 to heat exchange with the hot catalyst in the heat exchanger 40 u2033 the heat exchanged hot catalyst in the heat exchanger 40 u2033 is recycled back to the regenerator 13 u2033 via pipe line 41 u2033 steam is fed into the bottom of the dense phase fluidized bed 32 u2033 via pipe.