No mention of an ex-date in the merger annoucement.
Technically speaking the .74 @ share offer isnt a "dividend"...it's a one time "cash payment" and therefore wouldn't come under rules / proceedures that govern dividend(s).
Try calling or emailing the IR Dept at Fairmount Santrol. Below is a link to their site. Let the board know what you find out. Your question is a good one!