X rays do not pass through a black hole. In fact when a black hole exists and when matter is accelerated towards the black hole (that is being sucked into the black hole) the material (mainly H and He heats up to very, very high temperatures; so high that this accelerating matter emits X rays. So the X rays are generated OUTSIDE the black hole and that is what we see.

X-rays have been seen from black holes, but these x-rays are not coming from inside the black hole. They are coming from the accretion disk - matter that is falling into the black hole, heating up, but has yet to pass through the event horizon. Being as hot as it is, the accretion disk emits x-rays. Nothing is emitted from matter once it has fallen through the event horizon.