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New ceramic hollow fiber substrate for catalytic converters cuts fuel consumption, size and manufacturing costs
28 January 2014
A new ceramic hollow fiber substrate for catalytic converters designed by Dr. Benjamin Kingsbury and colleagues at Imperial College London could cut the size and precious metal loading of the devices in automobiles while reducing fuel consumption and and manufacturing costs. Kingsbury has founded MicroTech Ceramics Ltd. as a spin-out to commercialize the technology.
The new structure can achieve a 2-3% fuel saving in engines (through the elimination of backpressure), or offer high performance cars an equivalent increase in engine power. It also enables the size of catalytic convertors to be reduced by around 50%, offering engine and exhaust system designers greater freedom. The new substrate can use up to 80% less rare metal, a development that could significantly reduce costs for vehicle manufacturers.
A prototype is also predicted to perform better than existing models because the rare metal degrades less over the lifetime of the component. Laboratory tests suggest that it deteriorates by only 4% over a distance of 100,000 kilometers (62,000 miles), compared to 35% for a standard catalytic converter.
Three-way catalytic converters (TWCs) are used in automobiles to convert hydrocarbons, carbon monoxide and nitrogen oxides in exhaust gas to carbon dioxide, water and nitrogen. TWCs commonly comprise two main elements: a substrate (a ceramic block honeycombed with microscopic channels) and a catalytically active washcoat. The devices typically use precious metals such as platinum as the catalyst. These metals currently account for up to 60 to 70% of the cost of the component.
|The maximum GSA of a monolith substrate to date approaches 5,000 m2/m3 for automotive applications. Kingsbury’s micro-structured tube substrate can offer GSAs ranging from 8,000 m2/m3 to 15,000 m2/m3.|
The substrate, which consists of a large number of channels through which the exhaust gases pass, is to provide a large geometric surface area (GSA) for coating by the catalyst. The GSA of a catalyst substrate is a key factor in determining both the quantity of the catalyst that is required and the conversion efficiency of the converter, the inventors noted in their patent application.
Conversion efficiency can be increased by increasing catalyst loading, however the additional benefit of increased catalyst loading becomes substantially reduced as the quantity is increased, due to diffusion limitations within the washcoat. Increasing the loading also increases the cost. Therefore, by increasing the GSA it is possible to reduce the quantity of catalyst and increase the contact between the catalyst and the exhaust gas. The maximum GSA of a monolith substrate achieved to date is a figure approaching 5000 m2/m3 for automotive applications.
Kingsbury advanced an existing manufacturing process to improve the structure of the microscopic channels, increasing the surface area and enabling the rare metal in the device to be distributed more effectively so that less metal is used. The increased surface area also makes the catalytic converter’s chemical reaction process more efficient.
The maximum GSA of a monolith substrate achieved to date is a figure approaching 5,000 m2/m3 for automotive applications. According to the patent applications, Kingsbury’s micro-structured tube substrate can offer GSAs ranging from 8,000 m2/m3 to 15,000 m2/m3—up to a three-fold increase.
The new design of the device increases fuel efficiency because it prevents back pressure—a build up of gases that can make the engine work harder, affecting its performance.
Dr. Kingsbury developed the technology in conjunction with Professor Kang Li and Dr. Zhentao Wu who are both from the Department of Chemical Engineering at Imperial. He has been awarded funding from the Royal Academy of Engineering to take his prototype to the marketplace.
Patent Application: Catalytic converter substrate (WO 2013175239 A2)
Mukhlis A. Rahman, Francisco R. García-García, K. Li (2012) “Development of a catalytic hollow fibre membrane microreactor as a microreformer unit for automotive application,” Journal of Membrane Science, Volumes 390–391, Pages 68-75 doi: 10.1016/j.memsci.2011.11.009
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