Yes, TRIPOLIS is a Scrabble word!

Letter values in Scrabble US: T 1, R 1, I 1, P 3, O 1, L 1, I 1, S 1.

Is it a valid word?

TRIPOLIS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a weathered and decomposed siliceous limestone; in powdered form it is used in polishing
the capital and chief port and largest city of Libya; in northwestern Libya on the Mediterranean Sea; founded by the Phoenicians in the 7th century BC
a port city and commercial center in northwestern Lebanon on the Mediterranean Sea

Also: tarabulus al-gharb, capital of libya, tarabulus ash-sham.

Not playable in Scrabble US: TARABULUS, TRABLOUS.