Removing brackets and not breaking them

Thank you for reaching out to us. Most of the shelf brackets we sell plug into a hole and are then kept in place with the pressure of the shelf itself. However, yours may be glued in which would be an issue. If that's the case, you could use a commercial glue remover, soak a cloth with it, and then it should loosen after a time. I recommend going to a local hardware store to see what brand they specifically recommend. 

Another idea would be to try using a hair dryer to weaken the adhesive, then use a putty knife to pry it loose. Personally speaking, I try to shy away from hair dryers or heat guns for this kind of thing. They definitely work well, but if you aren't careful then you risk damaging the actual shelf itself. Heat's no joke and the risk of warping is real. Just something to consider. If you want to go that path, then I advise using a light touch. Don't go too hard, only just use enough.