Do catalysts provide the only practical route for the ultra-purification of hydrocarbons?

Presented at Spring Conference 2011, Copenhagen - 26 May, 2011

Dr. Peter Carnell, Johnson Matthey

The gas processing industry is well endowed with processes for the bulk removal of the acid gases CO2 and H2S. The most widely used rely on wash processes that involve weak bases or physical solvents chosen to allow regeneration by heat or depressurisation. However, these do not allow complete removal of these acid gases or of other undesirable species that may be present such as organic sulphur compounds, organometallic compounds, O2, Hg and COS.  Fixed bed adsorbents are effective for the removal of water and will adsorb higher molecular weight compounds but their capacity is limited and frequent regeneration is needed and they may adsorb undesirable species such as radon. Membranes and activated carbon have been proposed but have processing problems. There is a growing requirement for the ultra-purification of gases within the chemical and electronic industries. This can only be achieved by the use of chemical rather than physical reactions. These may be carried out with a single fixed bed absorbent or may require a two-stage process in which the impurity is converted to a more reactive compound (or compounds) before removal. This may involve the use of precious metal catalysts, as is the case in so-called Catox technology for oxygen removal or the more conventional catalytic systems used in the production of carbon fibres and aerosol grade propellants.