So I was messing around, trying to find out if anyone ever got POPSLoader to work with Adrenaline ePSP. I searched and couldn't find anything, so I decided to try myself but with no luck, the only thing that would happen was a black screen. I did some more digging, a little trial and error, and finally got POPSLoader to work with Adrenaline.
Okay, so first what you want to do if you already have Adrenaline installed is get the latest version of POPSLoader
Using VitaShell, connect your PS Vita to your PC. Go to appPSPEMUCFWlash0 and find these files:
common_util.prx
impose_01g.prx
proheaparea.prx
pafmini.prx
libpspvmc.prx
Copy these files to sepluginspopsloadermodules.
Next, you will need to dump PSP Firmware 4.01 so download PSARDumper and PSP Firmware 4.01. Rename the firmware to EBOOT.PBP and place it into the root of pspemu directory, where you have your ISO GAME and seplugins folders. Open Adrenaline, go to game, start PSARDumper and press square. Wait for it to finish, then exit Adrenaline and connect your PS Vita back to your pc.
Go back to your pspemu folder, there should be a new folder called F0. Open F0/kd/ and copy impose.prx into sepluginspopsloadermodules folder. In your seplugins folder, open POPS.txt and add this line to the main top: ms0:/seplugins/popsloader/popsloader.prx . Save and exit. Open Adrenaline, select your PS1 while holding down R and you'll be greeted with the POPS select screen.
Hopefully this helps someone else, because I was having trouble with Silent Hill and now it's running perfectly.