Every MTBE unit was built based on a licencing document that has all the information you need: design data and an operation manual. Your refinery should have this documentation wherever thay keep the design documents. Otherwise, you need to know whose licenced process is in use in that refinery...
An internet search on Google for "tank bladder" would give you about 50 supply sources. You can select the one that best suits your application and location. Here is just one of them: www.perma-type.com.
I hope this helps.
1. Assuming that the fluid is lighter than water and that the tank bottom is clean enough to avoid piercing a hole in it, consider buying a large bladder made of non-contaminating plastic or rubber. Ensure it has a long fill-up connection of the same material so it can be tied at the entry...