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Oxygen exchangers increase propene yield

22 October 2009 NWO (Netherlands Organization for Scientific Research)

Dutch researcher Jurriaan Beckers has shown that the yield of propene can be increased by adding cerium oxide during the production process. Propene is an important raw material for the chemical industry and its uses include the production of medical equipment. However, it is difficult to produce.

Making propene

There has been a rapid rise in the demand for propene in recent years due to the increased use of polypropylene, a polymer that is highly resistant to bacteria and chemical solvents. Propene can be made by converting propane, obtained from natural gas, into propene and hydrogen. One disadvantage of this so-called propane dehydrogenation is that the propene and hydrogen can easily react and become propane again. Consequently the propene yield remains low. Beckers discovered that this reverse reaction can be reduced by adding oxygen in the form of cerium oxide. The hydrogen is converted into water, making the reverse reaction impossible.

Stable and selective

As propane dehydrogenation takes place at temperatures between 550 and 600°C, the addition of gaseous oxygen to the mixture of hydrogen and hydrocarbons can be extremely dangerous. Besides the combustion of hydrogen, it can also lead to the combustion of the valuable propane and propene. Beckers solved this problem by adding the oxygen as a solid substance and not as a gas. For this he used cerium oxide, also know as ceria. This crystal is composed from cerium and oxygen atoms. Ceria is stable at high temperatures and easily exchanges oxygen.

Yet, unfortunately, ceria is not selective enough and it also combusts part of the propane and propene. In order to prevent this, Beckers substituted a small proportion of the cerium atoms with atoms of other elements. This substitution is also referred to as doping. For example, doping the ceria with copper, bismuth, chromium or lead creates an active and selective catalyst for the combustion of hydrogen from the dehydrogenation mixture. Due to the success of the research, Beckers' professor shall receive a new grant from the NWO programme ASPECT.

ASPECT programme

Beckers carried out his PhD research within the ASPECT programme, which focuses on using catalysts to improve the sustainability of chemical processes in the bulk chemical industry. ASPECT is a programme of the NWO temporary task force ACTS (Advanced Chemical Technologies for Sustainability).

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