Process and apparatus for producing lower carbon olefins and BTX by catalytic pyrolysis of hydrocarbon-containing feedstock oil

A process includes: cutting a hydrocarbon-containing feedstock oil into a light distillate oil and a heavy distillate oil; introducing the light distillate oil and a first catalyst into a down-flow reactor to produce a stream; subjecting the stream to a gas-solid separation to produce a first reaction hydrocarbon product and a first spent catalyst; or, introducing the stream into a fluidized bed reactor, and then subjecting to a gas-solid separation to produce a second reaction hydrocarbon product and a second spent catalyst; introducing a continuous catalyst, the heavy distillate oil and a second catalyst into an up-flow reactor, and then subjecting to a gas-solid separation to produce a third reaction hydrocarbon product and a third spent catalyst; separating out lower carbon olefins and light aromatics from reaction hydrocarbon products, separating out a light olefin fraction, and returning the light olefin fraction to the fluidized bed reactor or the up-flow reactor.