These large components are also the ones that don't vaporize easily, instead boiling off after the initial combustion has taken place. If the fuel could be produced comprising small molecules only, then our engines would run cleaner and more efficiently. This is exactly what LPG does. Thermal catalytic cracking refers to the process of cracking large molecule hydrocarbons into smaller molecules using heat and some sort of catalyst. It is how the oil refineries process crude oil into gasoline and other products.
Catalysts are typically metals such as nickel or copper.
Silica type desiccant is also a catalyst. The process involves heating the hydrocarbon and adding steam in the presence of a catalytic substance. Hydrogen from the water chemically combines with the hydrocarbon molecules which are broken into smaller more volatile components. The process is endothermic, meaning energy must be added to make it happen. The early high mileage carburetors often provided all the necessary conditions to enable this cracking process to proceed.