It is not so much the chemical/s themselves as the dispersion and trigger/detonation mechanisms.
The US used Fuel air munitions in Veit Nam.
U.S. Naval Museum of Armament Technology
Three sub muntions that had to "burst" and disperse the "agent" before detonation and it has to be the right height above ground level to get desired effect.
Also see:
Fuel/Air Explosive (FAE)
Thermobaric weapons add high temperature to the blast wave/effect and this is done using things like Magnesium and Aluminium. Aluminiumized explosives were used in WWII but getting powdered or granulated metal powders to disperse an ignite properly in your "normal" fuel cloud may take a bit of doing.
There may have been nothing to "prevent" it except
lots of testing and time.