Catalytic converters prevent knocking in engines without leaded fuel.
Houdry was a Frenchman working on high-octane fuels. His initial focus were race cars. Sun Oil sponsored the early work, in the 1930’s, moving Houdry to the US. The fuel work was a success but could not be use in mass production because the catalysts that allow the use of high-octane fuel would be destroyed by lead, which was then used in gasoline to increase compression to prevent knocking.
Time went by (during WWII, Houdry was a vehement anti-Nazi). Eventually, it became clear to Houdry and others that lead fuels caused serious environmental problems.
Houdry developed “catalytic cracking” to create high octane fuels via the use of a catalyst. Initially, fighter airplanes relied on high high-octane fuels. Correspondingly, this gave a substantial edge to Allied forces during WWII.
After the war, Houdry created and patented the catalytic converter allowing engines to run on lead-free gasoline. He patented the innovation in 1956 with a 1952 innovation date, assigning the rights to his company, Oxy-Catalyst Company.
His patent expired Apr. 16, 1970, less than a year before the newly created US Environmental Protection Agency (EPA), established Dec. 1970, labeled leaded gasoline as a threat.
Subsequently, the United States and most European government banned cars that required leaded gasoline in the 1970s.