Fuel fractionation using membrane distillation

A method for reducing emissions from an engine, the method comprising:

• generating a light hydrocarbon fuel fraction by:
• heating a fuel;
• flowing the fuel through a plurality of hollow superhydrophobic membranes in a membrane module, wherein each hollow superhydrophobic membrane comprises a porous support and a superhydrophobic layer free of pores that extend from one side of the superhydrophobic layer to the other, and wherein vapor from the fuel permeates the hydrophobic membranes and enters a distillate collection chamber, producing a distilled fuel in the distillate collection chamber and a residual fuel within the hollow superhydrophobic membranes;
• removing the residual fuel from the membrane module;
• cooling the residual fuel to produce a cooled residual fuel;
• flowing the cooled residual fuel through a plurality of hollow tubes in the membrane module;
• and
• removing the distilled fuel from the distillate collection chamber to produce the light hydrocarbon fuel fraction;
• and
• combusting the light hydrocarbon fuel fraction in the engine in place of the fuel, wherein combusting the light hydrocarbon fuel fraction generates fewer particulate emissions than combusting the fuel.