The Sterling Chemical plant where this took place also produces styrene, acrylonitrile, acetic acid, plasticizers, sodium cyanide and disodium iminodiacetic acid (DSIDA). If this was their only loading facility, I suppose those tanks might contain just about anything.
And don't ask me what disodium iminodiacetic acid is. I haven't a clue.
I think Sterling chem is just a sales company. They buy refinery output and sell that to folks that either repackage and resell it again, or are end users that are under the refinery/manufacturers minimum.