For the record, so you can learn, alpha catalysts are a blue color, and will be reflected by the name. Basic catalysts are grey, and class catalysts are the respective class colors. You can see the difference in the screen where you try to rank up Annihilus. As you level up, your inventory will increase. You inventory shows how many items of each kind that you can permanently hold, while the overflow holds anything else (these will eventually expire). Yes, you have 7 but your inventory limit is the maximum number that you can use at any one time.It might be a bummer, but it should indicate that with the campions you have, you actually can clear more content (and thus get more XP). The inventory limits are typically designed in a way that they should match your natural progression through the game. Story content (like Act 4 with XP boosts) is probably the best way to get more XP faster. Good luck.