To link your WordPress.com blog to your Facebook Page (business account) instead of your personal account, here’s what you need to do:
1) In your WordPress.com Dashboard, go to Settings > Sharing.
2) Next to Facebook, click the Connect button.
3) Enter your Facebook login details.
4) You should see a message that says, “You have successfully connected your blog with your Facebook account.”
It will then give you to options, one is to Publicize to my Facebook Timeline (which is your personal account) and the other is to Publicize to my Facebook Page (which is your business account).
5) Choose the radio button next to your Facebook Page (business account), then press OK.
6) It should now connect to the business account (Facebook page), instead of your personal account.
7) Don’t forget to press the “Save Changes” button at the very bottom of the page.
Here are the instructions to connect or reconnect Facebook from the WordPress.com’s support documentation: