Andrey J. Zarur

Reverse microemulsion synthesis of nanostructured complex oxides for catalytic combustion

Catalysts play an important role in many industrial processes, but their use in high-temperature applications—such as energy generation through natural gas combustion, steam reforming and the partial oxidation of hydrocarbons to produce feedstock chemicals—is problematic. The need for catalytic materials that remain stable and active over long periods at high operation temperatures, often in the presence of deactivating or even poisoning compounds, presents a challenge. For example, catalytic methane combustion, which generates power with reduced greenhouse-gas and nitrogen-oxide emissions, is limited by the availability of catalysts that are sufficiently active at low temperatures for start-up and are then able to sustain activity and mechanical integrity at flame temperatures as high as 1,300 °C. Here we use sol–gel processing in reverse microemulsions to produce discrete barium hexaaluminate nanoparticles that display excellent methane combustion activity, owing to their high surface area, high thermal stability and the ultrahigh dispersion of cerium oxide on the their surfaces. Our synthesis method provides a general route to the production of a wide range of thermally stable nanostructured composite materials with large surface-to-volume ratios and an ultrahigh component dispersion that gives rise to synergistic chemical and electronic effects, thus paving the way to the development of catalysts suitable for high-temperature industrial applications.

Lean-Burn Natural Gas Engine Exhaust Remediation Using Nanostructured Catalysts and Coatings

We have developed nanocrystalline catalytic systems with excellent thermal stability that reduce NO, CH4 and CO emissions from exhaust streams containing excess oxygen. Magnesium oxide, yttrium oxide and samarium oxide catalysts were synthesized using a controlled wet-chemical precipitation technique. This process produces nanocrystalline, high surface area metal oxide powders that can be easily coated onto monoliths and substrates. Greater than 50% conversion of NO to N2 was achieved in excess O2 at high space velocities with the nanocrystalline oxide catalysts. Nanostructured barium hexaaluminate coated with manganese oxide was used to aid in the complete oxidation of CO and CH4. The nanocrystalline oxide systems have superior hydrothermal stability compared to noble metal and zeolitic catalysts. Presence of water vapor in the feed stream resulted in only a slight loss of activity for the nanocrystalline Y2O3 system, the full activity of which was restored upon removal of water from the feed stream.