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U. Houston-led project looking for new exhaust treatment catalysts for low-temperature lean-burn combustion engines

A chemical engineer from the University of Houston is leading a $2.1-million project to find new catalytic materials that work at lower exhaust temperatures, allowing automakers to build vehicles that operate more efficiently while retaining the ability to clean emissions before they leave the tailpipe.

Michael Harold, chairman of the Department of Chemical and Biomolecular Engineering at UH, will serve as principal investigator on the grant, funded by the US Department of Energy National Energy Technology Laboratory (DOE NETL). The project also includes researchers from the University of Virginia (UVA); Oak Ridge National Laboratory (ORNL); and Southwest Research Institute (SwRI). Engineers from Fiat-Chrysler Automobiles Inc. and Johnson Matthey Inc. also will be involved in the project.

Catalytic converters clean vehicle exhaust into nitrogen, water and carbon dioxide. Current catalytic converters use precious metals, including platinum and palladium, to eliminate the main pollutants emitted by internal combustion engines.

These expensive precious metals may work, but it’s important to find less expensive materials that have enough activity at the low exhaust temperatures. Not only that, we have to come up with operating strategies so the new catalysts work over the wide range of conditions encountered during driving.

—Michael Harold

In his research at the University, Professor Harold has been investigating the catalytic reduction of NOx to nitrogen in the oxidizing atmosphere of lean burn and diesel vehicles. One approach he has explored involves the use of an adsorptive reactor in which the NOx is trapped as a nitrite/nitrate on an rare earth oxide and then reduced by the intermittent feed of a reductant.

This is a complex system involving the abatement of a key pollutant contained in a time-varying feed utilizing a periodic catalytic process. The challenge is to achieve high NOx conversion with minimal fuel penalty while sustaining long catalyst life.

The new engines, based on a lean-burn, compression-ignition technology, can’t be commercialized without a way to ensure they run cleanly to meet emission rules. Although the conventional three-way catalytic converter doesn’t work for the new engines, Harold said the new converters might be transferrable to current vehicles.

Harold and Lars Grabow, associate professor of chemical and biomolecular engineering at UH who works in fundamental catalysis, will work to discover and determine the effectiveness of new catalytic materials, working both with a class of known materials and developing new ones.

Researchers at UVA will conduct high throughput materials synthesis and screening, ORNL researchers will contribute in materials synthesis and characterization and SwRI will provide evaluation of fuels. Fiat-Chrysler and Johnson Matthey will bring their industrial expertise in vehicles and catalysts, respectively.


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