Catalytic reduction of nitric oxide by solid carbonaceous material under lean condition

The reactions of O_2, NO_x and soot from Diesel exhaust over Cu containing catalysts can significantly reduce soot and NO_x emissions while producing N_2 and CO_2. The author has evaluated the performance of Cu ion exchanged ZSM-5 and Cu adsorbed on Granulated Activated Carbon (Cu-GAC) using GAC as a surrogate for soot in a packed bed reactor. CO, formed primarily by the oxidation of GAC with O_2, appears to be a stable intermediate in the reduction of NO. With experimental parameters chosen to simulate Diesel exhaust conditions, Cu-GAC is much more effective than GAC mixed with Cu-ZSM-5, converting six times more NO_x to N_2 at 500 C at the representative gas hourly space velocity of 50,000. Both catalysts are poisoned by H2O and SO_2. A mechanism is presented that is consistent with the experimental results. Catalytic reduction of nitric oxide (NO) with solid carbonaceous materials to N_2 was also investigated over palladium based catalysts. Catalysts consisting of 4 wt.% Palladium on CeO_2, A1203 and TiO_2, prepared by the impregnation method, were evaluated as lean NO_x control catalysts with granular activated carbon (GAC) as the reductant. The performance of these catalysts was measured with a gas containing 590 ppm NO, 10% 0_2, and the balance He at gaseous hourly volumetric space velocities of 50,000 and 80,000 and at temperatures in the range of 200-600 C. All catalysts exhibited high activity for NO reduction with GAC. The PdO/Al2O3 showed the highest activity among the tested catalysts with maximum conversion over 80% at GHSV of 50,000. The PdO/CeO2 had the lowest light-off temperature of 450 C with a maximum conversion of 80% at GHSV of 50,000. The effects of SO_2 and water on the catalysts were also investigated by including 20 ppm SO_2 and 10% water into the gas feed mixture. The results indicated that the palladium catalysts outperform fresh copper exchanged ZSM-5, and are much more slowly poisoned by sulfur compounds and water while promoting NO reduction with GAC to N_2. The purpose of this study was to develop a novel catalyst that can be used in a rotating fluidized bed reactor (RFBR) containing an attrition resistant high surface area catalytic powder to filter soot and promote the reaction between soot and NO at elevated temperatures and at high space velocities. Consequently, this system is self-cleaning i.e., the soot layer is oxidized by NO_x + O_2 and removed as CO_2, while the NO_x is removed as N_2. The RFBR provides good contact between the catalyst and reactants, and a lower relative pressure drop compared to particulate traps and other existing particulate control devices.

Name thesis:degree_name

Doctor of Philosophy in Chemistry - (Ph.D.)

Discipline thesis:degree_discipline

Chemical Engineering, Chemistry and Environmental Science

Year

2002

Author dc:creator

• Xiao, Shan

Contributors dc:contributor

• Robert Pfeffer
• Henry Shaw
• John G. Stevens

• Nitric Oxide (NO) reduction
• Lean condition
• Carbonaceous material
• Palladium
• Cu-ZSM-5
• Chemistry

Repository record dc:identifier

https://digitalcommons.njit.edu/dissertations/550

OAI identifier oai:identifier

oai:digitalcommons.njit.edu:dissertations-1605