Any type of construction adhesive that lists PVC will work well for attaching corner guards to the wall. Two great options are:
How Much Adhesive Do I Need?
How much adhesive you need will depend on how much you use on each corner guard. In a normal application one 10.5 oz tube of adhesive will cover two 8' corner guards.
Keep in mind that construction adhesive is permanent so if you need to remove the corner guard after the adhesive has cured you will damage the wall.