Novel metal oxide nanocomposites for oxygen storage, sulfur dioxide adsorption and hydrogen sulfide absorption

Increasingly stringent regulations on automotive emissions have resulted in the need for improved pollution control technology. To reduce mobile emissions, researchers have investigated alternatives such as lean-bum engines and fuel cells. This work is focused on the synthesis, characterization and testing of novel metal oxide nanocomposites to facilitate the utilization of these technologies. In lean-bum engines, the use of adsorbents to remove NOx faces two major challenges: (1) excess hydrocarbon and CO emissions during fuel-rich pulses for adsorbent regeneration, and (2) reduced NOx adsorption efficiencies due to competitive adsorption of SO2 in the gas stream. To provide for the low-temperature oxidation of hydrocarbons and CO under a reducing atmosphere, CeO2, a well-known oxygen storage material, was modified through secondary metal oxide doping to improve thermal stability and oxygen accessibility. 20 at% substitution of Pr, Sc and Zr in CeO2 successfully promoted microstructural stability, with Ceo.8Zro0.202- retaining grain size of 30 nm even after calcination at 10000C. At high doping levels, Zr improved grain size stability further, but ZrO2 phase segregation was noted in CelxZrxO2.8 with x > 0.2. TPR experiments under 2.5% H2 in He showed that Ceo8Pr0.202- provided superior low-temperature reduction and overall reducibility amongst Ce0.8M0.2026- materials. Moreover, CelxPrxO2-8 showed increased reducibility with increasing x, achieving a maximum weight loss of 4.8% at x = 1.0. CO oxidation studies over Ceo.8M0.202-8 identified Sc and Zr doping with the lowest CO light-off temperatures (247⁰C and 264⁰C, respectively).

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Chemical Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Sweeney, Jason T. (Jason Thomas), 1971-

Advisor dc:contributor.advisor

• Jackie Y. Ying.

• Chemical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29295

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29295