NOVELTY - Fractionating complex mixture of vaporized compounds comprises: (a) injecting cooling fluid into vaporized compounds at first predetermined temperature to form first aerosol fraction and first remaining vaporized compound stream, where first predetermined temperature is less than vaporization temperature of first fraction but greater than vaporization temperature of first remaining vaporized compound stream; (b) separating first aerosol fraction from remaining vaporized compound stream by electrostatic precipitation at about predetermined temperature; and (c) collecting first aerosol fraction.    USE - The method is useful for fractionating the complex mixture of vaporized compounds (hot pyrolysis vapor or oil) from biomass pyrolysis (claimed).    ADVANTAGE - The method utilizing cooling fluid: affords low cost and low reactivity, and reduces oxidation and danger of explosions; minimizes or eliminates reactions between and/or among the various pyrolysis product components, particularly acid-catalyzed reactions; eliminates the use of indirect contact heat exchangers; and provides: sufficient separation of pyrolysis product components by class making further purification feasible; narrow bio-oil fractions; and selective and rapid collection and quenching for multiple times.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for fractionating hot pyrolysis vapor or oil from biomass pyrolysis, comprising: (a) injecting a coolant into hot pyrolysis vapor from biomass pyrolysis to selectively condense a first fraction from the hot pyrolysis vapor at a first predetermined temperature that will condense the first fraction, where the coolant is nitrogen, hydrogen, carbon monoxide, carbon dioxide,, methane, water, argon, helium and/or an inert gas; (b) collecting the first fraction by electrostatic precipitation at about the first predetermined temperature; (c) injecting additional coolant into the hot pyrolysis vapor to selectively condense a second fraction from the hot pyrolysis vapor at a second predetermined temperature that will condense the second fraction; (d) collecting the second fraction by electrostatic precipitation at about the second predetermined temperature; and (e) optionally repeating steps (c) and (d) at progressively cooler temperatures.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic illustration of equipment for fractionating the complex mixture of vaporized compounds.    Collection system (110)    Chiller (120)    Mixing zone (140)    Electrostatic precipitator (160)    Cooler (180)