Porteous was dismissed on the half-hour mark for a challenge on Joe Aribo in our 2-1 defeat at Ibrox.
Chief Executive Ben Kensell said: “After reviewing footage of the incident, we have decided to appeal the decision.
“We believe we have enough evidence to show his challenge was not worthy of a sending off.
“We will await an answer from the SFA and stand united with Ryan, who has our absolute support.”
If the red card is upheld, it means that our centre-half will miss our first two games after the international break when we face Dundee United at home (Saturday 16 October) and Aberdeen away (Saturday 23 October).
