The Problem With Cold Converters

University of Kentucky researchers aim to reduce emissions that occur in cold starts

Mark Crocker and Yaying Ji

Two professors at the University of Kentucky are tackling the problem of lowering highly reactive nitrogen oxides (NOx) that a vehicle emits when it is first started and the gas is still cold. Currently, vehicles use a catalytic converter to remove the NOx, but the converter needs to warm in order to efficiently remove the pollution.

Mark Crocker, a professor of chemistry in the University of Kentucky College of Arts and Sciences and assistant director of the Biofuels and Environmental Catalysis Group at the UK Center for Applied Energy Research (CAER), along with CAER research scientist Yaying Ji have developed and received a patent on a novel technology that addresses this problem.

Named “passive NOx absorbers,” the technology uses a material that traps NOx emissions at low temperatures and then releases them at higher temperatures, at which point in time the catalytic converter has warmed up enough to remove them.

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“Once they’ve reached operating temperature, present-day catalytic converters are extremely efficient, typically removing more than 99 percent of NOx emissions,” Crocker said. “Consequently, the majority of vehicle emissions occur during cold starts — in other words, before the catalytic converter is working properly.

“We conducted research on a class of materials that can effectively trap pollutants until the vehicle’s catalytic converter is warm enough to convert them to harmless products, like nitrogen and water.”

The project’s industrial partner is Luxfer MEL Technologies, which is currently providing samples of the technology to vehicle manufacturers for evaluation. Luxfer MEL Technologies provides innovative products and solutions to customers worldwide for use in a broad range of industries, including aerospace, automotive, catalysis, oil and gas, ceramics and healthcare.

The new technology is a result of a $900,000 grant Crocker’s CAER group received from the National Science Foundation in conjunction with the U.S. Department of Energy’s Vehicle Technologies Office.

Crocker, Ji and chemistry graduate student Robby Pace are looking at another class of material — zeolites — for this same purpose.

“Zeolites are potentially even more promising for trapping NOx; however, the chemistry of NOx storage in zeolites is highly complex,” Crocker said. “Funding is being provided in the form of a $2 million grant from the U.S. Department of Energy’s Vehicle Technologies Office.”

As part of this grant, the CAER is partnering with the University of California, Berkeley; Purdue University; Oak Ridge National Laboratory; the Ford Motor Co.; and BASF, the largest chemical producer in the world.

The UK CAER conducts research focused on the optimal use of Kentucky’s and the nation’s energy resources for the benefit of its people. Its goal is to solve existing energy problems while identifying potential future technologies.


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