Houdry cracking process

What is Houdry cracking process?

The Houdry cracking process is an industrial technique for breaking down petroleum or heavy petroleum fractions into more useful lower-boiling substances. This process was first introduced by Eugene Houdry in 1934 and is carried out by heating the oil to 500 °C and 30 psi, using a clay catalyst composed of silica, alumina, and manganese oxide MnO2. The process is named after its inventor and is also known as the Houdry cracking process.

Houdry cracking process - general reaction scheme
Houdry cracking process

R1, R2 = either an aryl or a long hydrocarbon chain, with or without branches.

The first commercial fixed-bed, three-case cracker was built in 1936, which could crack up to 2000 barrels of oil daily. Following the invention of the process, the Houdry Process Corporation was established, and its research branch, Houdry Laboratories, was established in Marcus Hook, Pennsylvania, to focus on studying catalysts for such petroleum-cracking processes.

However, during the thermolytical degradation of oil, continuous coking occurs, which deactivates the catalyst. To address this issue, vaporized gas oil and air were passed alternately over the catalyst bed in each case of the first three-case cracker. In a single cycle of a three-case cracker, one case is cracking, another is burning carbon, and the third is being purged. The typical cycle duration is approximately 10 minutes.

Several factors, such as the chemical nature of the oil gas, the time and temperature for the catalyst’s exposure to oil gas, contamination of the catalyst by metals entrained in the stock, and the type of catalyst, affect the effectiveness of a catalyst. Heavy metals, such as iron, nickel, vanadium, and copper, are detrimental to the catalyst. At high cracking temperatures, it is believed that the decomposition of oil follows a radical mechanism. More information on this process is available.

Oil refinery manufacturing plants have widely adopted this process for the production of gas and other petrochemicals.