Houdry joined his father's business, but left for military training right before the outbreak of World War I. He served in the French army as a lieutenant in the tank corps and in 1917 was seriously wounded in the battle of Juvincourt, winning the Croix de Guerre for his actions and later becoming a Chevalier of the Legion of Honor.

After the war, Houdry rejoined his father at Houdry et Fils, but by 1922 was making his way in the field of catalytic processes for the conversion of coal and lignite to gasoline. His interest in high-octane gasoline was fueled by his avid interest in automobile engines and in road racing, where he competed in a Bugatti racing car.

In addition to the process for high-octane gasoline, Houdry also invented a catalytic process for the production of butadiene from the butane gas derived from crude oil production. Butadiene became an important resource during World War II. It was one of the two components used in the synthetic rubber program initiated after natural rubber supplies were eliminated by the war in the Pacific.

Houdry was outspoken in his opposition to wartime collaboration with the Germans by the French Vichy government of Marshall Henri P¸tain. On May 3, 1941, the Vichy government declared that Houdry had lost his French citizenship. He then became president of the U.S. chapter of "France Forever"�an organization dedicated to the support of General Charles de Gaulle, the nominal head of the French government in exile�and in January 1942, he became a United States citizen. His two sons, Jacques and Pierre, served in the United States Army during World War II, and Houdry directed his efforts toward industrial processes crucial to the war effort.

After World War II, Houdry formed the Oxy-Catalyst Company and turned his attention to reducing the health risks associated with the increasing amounts of automobile and industrial air pollution. His generic catalytic converter, which greatly reduced the amount of carbon monoxide and unburned hydrocarbons in automobile exhausts, was granted U.S. Patent 2,742,437 in 1956. Today, catalytic converters made by various companies are standard devices on all American cars.

Houdry's colorful life was full of great ambitions. His unusually productive career was characterized by unique foresight, bold imagination, creative leadership, persistence and, above all, action. Houdry's contributions to catalytic technology were recognized by numerous awards, including the Potts Medal of the Franklin Institute in 1948, the Perkin Medal of the Society of Chemical Industry (American Section) in 1948, the E. V. Murphree Award in Industrial and Engineering Chemistry of the American Chemical Society in 1962, and posthumous election to the National Inventors Hall of Fame in 1990. He was awarded honorary Doctor of Science degrees by Pennsylvania Military College in 1940 and by Grove City College in 1943. In 1967, the Catalysis Society of North America established the Houdry Award in Applied Catalysis.

Houdry died on July 18, 1962, at the age of 70, survived by his sons and his wife, Genevieve Quilleret. At that time he was actively working on creative ideas for using catalytic processes to improve human health.