Low-Temperature SCR of NO with NH 3 over USY-Supported Manganese Oxide-Based Catalysts

A series of catalysts of manganese oxide, manganese–cerium and iron–manganese oxide supported on USY (ultra-stable Y zeolite) were studied for the low-temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen. It was found that MnO x /USY have high activity and high selectivity to N 2 in the temperature range 80-180 °C. The addition of iron and cerium oxide increased NO conversion significantly although the single-component Fe/USY and Ce/USY catalysts had low activities. Among the catalysts studied in this work, the 14% Ce-6% Mn/USY showed the highest activity. The results showed that this catalyst yielded nearly 100% NO conversion at 180 °C at a space velocity of 30 000 cm 3 g -1 h -1 . The only product is N 2 (with no N 2 O) below 150 °C. The effects of the concentration of oxygen, NO and NH 3 were studied and the steady-state kinetics were also investigated. The reaction order is 1 with respect to NO and zero with respect to NH 3 on the 14% Ce-6% Mn/USY catalyst at 150 °C.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44262/1/10562_2004_Article_462760.pd

Low-temperature SCR of NO with NH 3 over noble metal promoted Fe-ZSM-5 catalysts

We have reported previously the excellent performance of Fe-exchanged ZSM-5 for selective catalytic reduction (SCR) of NO with ammonia at high temperatures (300–400 °C). In this work, we found that the reaction temperature could be decreased to 200–300 °C when a small amount of noble metal (Pt, Rh, or Pd) was added to the Fe-ZSM-5. The SCR activity follows the order Pt/Fe-ZSM-5 > Rh/Fe-ZSM-5 > Pd/Fe-ZSM-5 at 250 °C. On the Pt promoted Fe-ZSM-5, 90% NO conversion was obtained at 250 °C at GHSV  = 1.1 ×  10 5  h −1 . Moreover, the noble metal improved the resistance to H 2 O and SO 2 . The presence of H 2 O and SO 2 decreased the SCR performance only very slightly.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44250/1/10562_2004_Article_3462.pd

New nano-structured materials for nitric oxide/ammonia abatement, desulfurization and hydrogen storage.

Nanoporous materials as catalysts and adsorbents with unique surface chemistry have high surface areas and unique morphologies, which influence catalytic behavior and adsorption capacity. This property provides scope of the synthesis and screening of new nanomaterials for catalytic reaction, adsorption and storage. This dissertation discusses the synthesis, characterization and evaluation of several nano-structured materials for nitrogen oxides, ammonia emission control by selective catalytic reaction, desulfurization from liquid fuel and natural gas and hydrogen storage applications. These materials include iron exchanged zeolite, mixed cerium-manganese oxides, titania support ironmanganese, titanium-pillared clay support palladium, vanadium modified titanium-alumina support palladium, copper salts dispersed on alumina, pi-complex sorbents, such as silver and copper exchanged zeolite and active carbon/carbon nanotube. Fe-ZSM-5 prepared by several methods was examined for high temperature SCR of NO with ammonia and a cheaper method used for preparation of Fe-ZSM-5 with high activity was found. Mixed oxides were tailored for low temperature SCR of NO with ammonia. Cerium-manganese oxides were found to exhibit superior activity for this reaction. The SCR of NO with hydrogen in the presence of excess oxygen was studied over Pd based catalysts for applications for heavy-duty diesel engines, and found that the sample containing vanadium show high activity and wider temperature window. Silver and copper exchanged zeolite show high efficiency for sulfur removal from natural gas. A simple and effective technique was developed to build carbon bridges that serve to improve contact between a spillover source and a secondary receptor, and then increase the capacity of hydrogen storage.Ph.D.Applied SciencesChemical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125739/2/3208536.pd

Impact of Ni Content on the Electrochemical Performance of the Co-Free, Li and Mn-Rich Layered Cathode Materials

Li and Mn-rich layered cathode (LLC) materials show great potential as the next generation cathode materials because of their high, practical and achievable specific capacity of ~250 mAh/g, thermal stability and lower raw material cost. However, LLC materials suffer from degradation of specific capacity, voltage fading due to phase transformation upon cycling and transition-metal dissolution, which presents a significant barrier for commercialization. Here, we report the effects of Ni content on the electrochemical performance, structural and thermal stability of a series of Co-free, LLC materials (Li1.2NixMn0.8-xO2, x = 0.12, 0.18, 0.24, 0.30 and 0.36) synthesized via a sol-gel method. Our study shows that the structure of the material as well as the electrochemical and thermal stability properties of the LLC materials are strongly dependent on the Ni or Mn content. An increase in the Ni to Mn ratio results in an increase in the average discharge voltage and capacity, as well as improved structural stability but decreased thermal stability

Insight of platinum poisoning Cu/SAPO-34 during NH3-SCR and its promotion on catalysts regeneration after hydrothermal treatment

This study mainly focused on selective catalytic reduction of air pollutants NOx by ammonia (NH3-SCR), and a series of Pt impregnated Cu/SAPO-34 (homemade) samples were employed to elucidate its negative impact on DeNOx activity and hydrothermal treatment's acceleration on NH3-SCR activity resurgence. Firstly, XRD, NH3-TPD and DRIFTs were performed to examine platinum interaction with zeolites structure and contribution to acidity. Then, Pt inhibition on NH3-SCR activity Was evaluated and its impact on reaction network, including ammonia oxidation, NO oxidation and NO + NH3, was concluded based on gas switching tests. H-2-TPR and EPR further reflected various Cu species coordination and redox capacity variation caused by platinum doping. It was intriguing to find out that the further hydrothermal treatment benefited rejuvenation of Pt-poisoned Cu/SAPO-34 and even activity enhancement from Pt presence under the condition of zeolites structure integrity. Hydrothermal treatment induced platinum sintering and STEM illustrated platinum species combined with copper oxides and generated oxo-complexes, weakening ammonia oxidation. And Pt presence promoted copper oxides further dispersion during hydrothermal treatment. Finally, platinum poisoning on Cu/SAPO-34 and its regeneration after hydrothermal treatment were concluded to indicate their application potential. (C) 2016 Elsevier B.V. All rights reserved

Thermally stable single-atom platinum-on-ceria catalysts via atom trapping

Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temperatures. High temperatures are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoring the platinum. Performing synthesis at high temperatures ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst