That's up to you and your employer.

Edit: Worth pointing out that it's not really a Facebook account in the typical sense. You can have an FB@Work account without having an FB account, though it seems you can also use your FB account for both.

> Employers can create separate log-ins for employees to use with their Work accounts, or users can link these up with their other profiles to access everything in one place.

Doesn't look like you have to have personal account or link it.