Why are the heavier fractions from crude oil unsuitable for use as fuels?

Answer 1

The first answer is off-base, There is actually more heat capacity per unit weight for higher molecular hydrocarbons.

I agree with the second answer, typically there is more branching and more functional groups (like acids, thionyl group & amines) and even elemental contamination as you go up in molecular weight. So you get incomplete combustion and acid gases and metallic pollution. The low molecular weight alkanes “unzip” (cleaving off the terminal carbon) quite cleanly.

Also think about handling, as you get to higher molecular weights viscosity goes up and percent solids goes up. Even though you might be able to pump a liquid fraction, there would be a build up of high molecular weight gunk in distribution tanks and lines and your vehicle’s fuel system. Smaller molecules are always cleaner.

Of course the engines would have to be redesigned to work with specific molecular weights and fuel types, much like methane, propane, gasoline and diesel engines are today.

As a fuel high molecular weight materials work fine, heck look at space Ship One. They use a solid hydrocarbon fuel that has the consistency of rubber.

Answer 2

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Answer 3

They are unsuitable because upon ignition, there isnt enough viable energy released to be used as a efficient fuel. I mean, would you want to pump 25 gallons of tar to get the equivalent energy of about 1 liter of gasoline (octanes, heptanes, and a few other components).

Answer 4

'Bunker C' is a heavy fraction of crude oil consisting of 'Topped Crude' which is crude oil having had much of the lighter fractions removed.

Bunker 'C' is a heavy fuel oil used in furnaces in refineries and boilers in steam raising equipment in ships .. etc.

Answer 5

for many reasons, but mainly because they cause more pollution