can a bad cataylitic convertyer make your car rough idle?

What is your question?

I hear knocking noises from the catalytic conver and the car rough idles at a stop and in all gears including nutraul but idles fairly ok in park

What makes this problem better or worse?

running in gear makes the shake and noise lessen

How long has your 1998 Jeep Grand Cherokee had this problem?

just started but was most likely there before but not obvious