With pure alprazolam base bulk powder, you wouldn't necessarily need to dissolve it in PG/PEG to vaporize the alprazolam in an appropriate methamphetamine-style pipe, althought it may make it somewhat easier to handle depending on your method of vaporization.
But that aside, it's an insanely needless risk so far outweighing any benefits vs the oral or sublingual ROA, and imprecise vaporization could generate potentially toxic or carcinogenic by-products which would not be good to be inhaling.
TL;DR, don't vaporize alprazolam.