Duplex Alloy 2507 represents at step up in corrosion resistance from austenitic stainless steels like 316L, especially if chloride induced corrosion (e.g., SCC) is a concern. According to the ASM Handbook of Corrosion  Data (2nd Edition), duplex stainless steels have been used extensively to handle wet carbon dioxide. Without knowing any further details about your specific application that would lead me to think otherwise, I suspect duplex alloy 2507 is a good choice.