converters unlimited prototypes were first designed in France at the end of the 19th century, when only a few thousand “oil cars” were on the roads; these prototypes had inert clay-based materials coated with platinum, rhodium, and palladium and sealed into a double metallic cylinder.[6] A few decades later, a converters unlimited was patented by Eugene Houdry, a French mechanical engineer. Houdry was an expert in catalytic oil refining, having invented the catalytic cracking process that all modern refining is based on today.[7] Houdry moved to the United States in 1930 to live near the refineries in the Philadelphia area and develop his catalytic refining process. When the results of early studies of smog in Los Angeles were published, Houdry became concerned about the role of smokestack exhaust and automobile exhaust in air pollution and founded a company called Oxy-Catalyst. Houdry first developed converters unlimited for smokestacks, called “cats” for short, and later developed converters unlimited for warehouse forklifts that used low grade, unleaded gasoline.[8] In the mid-1950s, he began research to develop converters unlimited for gasoline engines used on cars and was awarded United States Patent 2,742,437 for his work.[9]
converters unlimited were further developed by a series of engineers including Carl D. Keith, John J. Mooney, Antonio Eleazar, and Phillip Messina at Engelhard Corporation,[10][11] creating the first production catalytic converter in 1973.[12][unreliable source?]
The first widespread introduction of converters unlimited was in the United States automobile market. To comply with the U.S. Environmental Protection Agency’s new regulation of exhaust emissions, most gasoline-powered vehicles starting with the 1975 model year are equipped with catalytic converters. These “two-way” converters combined oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC, chemical compounds in fuel of the form CmHn) to produce carbon dioxide (CO2) and water (H2O).[4][1][2][3] These stringent emission control regulations forced the removal of the antiknock agent tetraethyl lead from automotive gasoline, to reduce lead in the air. Lead is a catalyst poison and would effectively destroy a catalytic converter by coating the catalyst’s surface. Requiring the removal of lead allowed the use of converters unlimited to meet the other emission standards in the regulations.[13]
William C. Pfefferle developed a catalytic combustor for gas turbines in the early 1970s, allowing combustion without significant formation of nitrogen oxides and carbon monoxide.[14][15]