when changing the catalytic convertor on the awd do you need to disconnect the rear drive shaft

It all depends on how you are going to remove it. The best way that might get you out of moving the exhaust is to get a chain whip cutter. Any Advanac e Auto or Auto Zone has them on a loaner basis and they cut through ehhast like hot butter. If you are unbolting it, get some PB Blaster which is better than WD40 and let is saok for as long as possible and spray it on and wipe it off as much as possible. It will make all the difference in the world to get the hardware off.

got bolts lose cant get around drive shaft to get off.

that would work to get old one out but need to put new one back in

Well, then you must remove the driveshaft. It is not hard. Remove the rear u-joint and then slide the driveshaft back towards rear of van. Put a rag under the tail of the tranmission if it is propped up and you may want to get some transmission fluid to top it off. you can always slip the yoke back in the tranny once it is out of your way.