Making instead of buying is a small hint that the amount is significant...
Can styrene (-30°C) be separated from benzene (+5°C) through the melting temperature? In a freezer. OK, I understand the polymerization of acetylene yields many more unwanted things, and that benzene must make eutectics with many aromatic compounds, but if some benzene too is recycled, it's nothing tragic.
One thing I like with just hydrocarbons, all fully deuterated, is that deuterium can be recovered from the unwanted compounds by pyrolysis. Or by full combustion, since the C2Ca route needs D2O.