How many Empire Cards can I play on my turn?
According to the rules, you get two empire cards at the start. You can get additional empire cards if you land on a empire square, but these must be played immediately:


  Take the top Empire card and do what it says. Once you’ve played it,
  return the card to the bottom of the pile.


There is no mention on when to use them. But on the wikihow page, there is a more expanded section on empire cards:


  8 Give everyone two empire cards and one tower. Everyone starts the
  game with two Empire cards. Look at them, but don’t share them you’re
  your fellow players. Wait until your turn to use them.


This implies you can use them both onto your turn, not specifying when, so yes, you can play them right after you played the one you got from the empire square.