Separating Audio Channels Premiere Pro 22

Premiere is a little bit rigid in how it handles audio tracks and channels. There are two approaches you can go with (the second one is probably easier in this case, but if you needed more custom channel mapping you'd need to approach it the first way, so I'll say both in case it helps you in the future):
1. Create a new sequence with the audio channel mapping how you wish. So you'd basically make sure to map A1 to Left Pan, and all the other tracks to Right Pan. You should be able to copy and paste your current timeline into that new sequence.

2. Because it sounds like you are only concerned with panning then you can probably set this up for your Sequence in the Audio Track Mixer. Just Pan A1 all the way left, and Pan A2-9 all the way right. **EDIT: See Richard Knight's reply about the balance. It would probably be safest to use Option 3 rather than this one, using Mono Submixes.

Note that you could also just route A2 - A9 into a Submix/Bus and then you'd just Pan the bus instead of all the individual tracks:

Hope this helps.