How about copying the catalog (using your OS e.g. Windows File Explorer), give the copied catalog a new name, and then delete the files from the new catalog. You can choose whether to delete the personal or business photos from the catalog and name the catalog accordingly.
Just a warning about deleting many files at the same time. It's one of the slowest commands in the organizer. In many cases, if you select many thousands of files, that will take hours and the process will probably abort for lack of memory/disk space. So, first test how many files you can delete in one batch and delete files progressively when you are not using the computer. If the process aborts, you'll have wasted some time, but you won't lose anything. In the meantime, you can 'hide' files instead of deleting them.
If one of the catalog parts you want to split is very big and you want simply to extract a smaller subcatalog, move the selected files to extract to a new location on the computer (master folder, drive, partition...) after writing metadata to files. Create a new catalog and import from that location. Delete or hide the extracted files from the bigger catalog. You can even recover the keywords structure by saving it in a text file and importing it in the new catalog prior to importing the media files.
I hadn't thought of copying the catalog in Windows and working from there. I'll give it a shot.
Even my Catalog file is nearly 10GB so I'm dealing with some large capacity content (I think; I'm really not sure what the typical capacity, or limit, for Elements....so I'm not certian if I'm pushing the envelope or if I'm in the comfort zone for catalog size.)
In your original post, you mentioned 103K items in your library. That's already a big catalog, but quite manageable. If you were to split it into two equal size separate ones, the catalog folder copy with the Explorer would probably require many deleting batches. With only a smaller batch to extract, that would seem feasible.
So, try to estimate the size of the smaller part of the catalog to extract and the size of the batch you can delete without the deletion aborting. That should give you an indication of the time required to achieve your goal.