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Improvement of ceramic substrate of three-way catalysts (twc) to develop a regeneration and/or reactivation procedure of used catalysts

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A big role to play for the humble exhaust catalyst

In an industry where cutting costs can make a competitive difference, the EU-funded project Regencats considered the practical aspects of reactivating aged car exhaust catalysts. By prolonging their life, catalysts are put at the forefront of the ongoing battle to meet ever more exacting emission requirements around the world.

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Cars have been in mass production since the beginning of the 20th century, and their increasing numbers give personal mobility to an ever larger mass of people. With approximately 800 million cars currently in service worldwide, the impact of such an increase on an already heavily strained environment is, and will be, substantial. Incomplete combustion and the presence of impurities in the fuel cars burn result in the release of carbon monoxide, nitrogen oxides and unburned hydrocarbons. Fortunately, a way has been found to convert these highly toxic gases into harmless end-products and crack the problem of pollution before they get pumped out into the air. That is the job of catalytic converters, which are able to abate simultaneously all three of the above-mentioned pollutants, hence the name three-way catalysts (TWCs). Although a well-established technology, research continues in order to enhance the durability of catalysts if increasingly low levels of emissions are to be met during the lifetime of the catalysts. The Regencats project partners decided on following two different pathways towards achieving this goal. Either by improving the thermal stability of the metallic or ceramic material supporting the active catalytic material, or by the regeneration of the catalyst. With time, TWCs inevitably succumb to degradation. The harsh environment under which they work leads not only to ageing, but also to the contamination of their active surface with reactants, products and impurities in the exhaust. To restore the lost catalytic activity of worn out TWCs, different gas and heat treatment were put to the test. First, chemicals were applied to remove the poisons that have contributed to the degradation of the catalyst. Chemical reactivation is then followed by a second step, heat treatment. Process advances accomplished during the Regencats project made it possible to fully restore the catalyst activity to its original level. Perhaps what is even more important is the economic upside that the project partners saw in the regeneration of used catalysts. Because regenerated catalysts are expected to have a life longer than the original, the cost of regeneration would be capitalised in the same manner as its replacement with a new catalyst. Moreover, when the car reaches the end of its useful life, reusing its catalyst on another car would be profitable not only from an economical point of view but also an ecological standpoint. As car ownership continues to increase, it is important that the proportion of end-of-life vehicles being reused is maximised, so that the environmental burden is reduced. The proportion of cars currently being recycled is much greater than any other consumer product. Even so, the technology proposed by the Regencats project promises to further reduce the remaining material being buried in landfill sites.

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