Can you put loose cellulose insulation over knob and tube wiring in attic ?

NO. See prior post reply.

K&T. Uses Not Permitted NEC 394.12 2012 edition
(5) Hollow spaces of walls, ceilings, and attics where such spaces are insulated by loose, rolled, or foamed-inplace insulating material that envelops the conductors.

The reason is that knob and tube wiring was designed to operate in open air. Any insulation covering K&T wiring will cause the wiring to overheat.

If the attic is easily accessible, why not be safe and convert to NM-B(Romex)