I know there are 1000's of threads about this but all I could find was steel and aluminum and carbon and aluminum. My friend brought over an old aluminum trek and while we were servicing it we realized the seatpost was stuck. The main issue is the fact that it is an aluminum seatpost and an aluminum frame. Does anyone have any experience with this? I can't use ammonia because I would damage the frame and liquid wrench is not really doing much. Thanks in advance.

Liquid Wrench is the least effective of the popular shelf-bought parts freeing sprays.
PB Blaster is better, Kroil even better.
You can try to mix your own...50/50 mixture of acetone and ATF. Claimed to be most effective on a machinists site.

Being aluminum, try heat. The rapid expansion rate may be beneficial here. Heat the seat tube, post will get hot. Rapid cool the post while the seat tube stays hot. The contracting post might break the bond.

A neat trick for rapid cooling of something is to buy a small can of compressed air (for blowing dust off of keyboards and other computer parts), turn it upside down, and spray that onto something. The gas inside comes out in liquid form and it is awfully cold. It'll give you frostbite quick, and it's flammable, so wear gloves and make sure your torch is turned off before you do this.