NOx reduction Efficiency is increased by up to 45% compared to Platinum.
Wayne Gerdes -
CleanMPG - Aug 19, 2012
A diesel powered Freightliner Cascadia making its way East with a load of goods destined for shelves near you. Its NOx emissions systems may have just been simplified for a far lower cost.
Professors from the University of Texas at Dallas may have solved one of compression ignition – internal combustion engines (CI-ICE) or diesels long term problems. That being excessive NOx generated at the higher air-fuel combustion chamber temperatures needed to ignite the mixture vs. regular gasoline engines whose spark ignited (SI-ICE) ignition occurs at much lower temperatures yielding far less NOx after combustion.
In a release from the University of Texas at Dallas, Dr. Kyeongjiae Cho, Professor of Materials Science, Engineering, and Physics said platinum is too scarce and expensive to be a long-term answer to diesel's emission problems.
Engineers at a company co-founded by the professor have identified a far more common and less expensive material that can reduce NOx by a greater percentage than being done today.
The material could replace platinum, a rare and expensive metal that is currently used to try to control the amount of NOx produced.
In a study published in the August 17 issue of Science, researchers found that when a manmade version of the oxide mullite replaces platinum,
emissions are reduced by up to 45 percent compared with the current state of the art platinum catalysts!
Platinum, because of its expense to mine and limited supply, is considered a precious metal. Estimates suggest that for 10 tons of platinum ore mined; only about 1 ounce of usable platinum is produced.
In 2003, Cho became a co-founder and lead scientist at Nanostellar, a company created to find catalysts through a material design that would replace platinum in reducing diesel exhaust (CO, and NOx). His company has designed and commercialized a platinum-gold alloy catalyst that is a viable alternative to platinum alone but it is more expensive than the current platinum based systems. Until experiments with mullite, no one had found a less expensive solution to this age old problem.
Cho’s team synthesized mullite and used advanced computer modeling techniques to analyze how different forms of the mineral interacted with oxygen and NOx. After computer modeling confirmed the efficiency of mullite to consume NOx, researchers used the oxide catalyst to replace platinum in diesel engine experiments.
Dr. Kyeongjae Cho:
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“We’ve found new possibilities to create renewable, clean energy technology by designing new functional materials without being limited by the supply of precious metals.”
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The mullite alternative is being commercialized under the trademark name Noxicat. Dr. Cho and his team will also explore other applications for mullite including fuel cells.
Which all comes down the fact diesels emissions hurdles have been met at each stage of CARB’s and the EPA’s look ahead rulings but not without expensive internal engine designs that include pre-cooling the air-fuel mixture prior to injection, higher pressure and multiple injections per ignition event, micro control of the flame front and combustion pressures down into the piston bowl, reduced back pressure on exhaust, large percentage Exhaust Gas Recirculation (EGR), Diesel Oxidation Catalysts (DOC), Lean NOx Traps (LNT) or Selective Catalyst Reduction systems (SCR) with Urea injection along with diesel particulate filters (DPF). The aftertreatment systems and their acronyms have become far more complex than the NOx and particulate these systems are supposed to remove. At least the various NOx catalyst system schemes (DOC, LNT, SCR or a combination of them) escalating costs appear to have been circumvented thanks to advanced science and engineering being performed out of the University of Texas – Dallas and its satellite start-ups.
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