So, the answer is: fractionator; With the decrease of pressure, the boiling point of hydrocarbon 8 decreases with the decrease of pressure, so that heavy oil can be fractionated at a lower temperature;
(2) vinyl chloride plastics can be produced by addition polymerization of vinyl chloride: nnH2=nHnl? Catalyst, so the answer is: nnH2=nHnl? Catalyst;
(2) Vinyl chloride plastic is flame retardant, corrosion resistant and warm, so the answer is: flame retardant and corrosion resistant;
(2)A, gases with pungent smell when PVC burns; And polyethylene flammable, when burning, has no smell, so A is wrong;
B, polyethylene can't degrade itself and needs to be recycled, so B is wrong;
N, polyethylene plastic is non-toxic and PVC plastic is toxic, so n is wrong;
1, the density of polyethylene 8 is less than that of water, and the density of polyvinyl chloride 8 is less than that of water, so 8 floating on the water is polyethylene and 8 submerged in water is polyvinyl chloride, so 1 is correct;
So choose: 1.