NOx Adsorber Catalysts with Improved Desulfation Properties and Enhanced Low-Temperature Activity

2009 ◽  
Author(s):  
Hai-Ying Chen ◽  
Shadab Mulla ◽  
Mahesh Konduru ◽  
Julian P. Cox ◽  
Paul J. Andersen
Keyword(s):  
Low Temperature ◽  
Nox Adsorber

scholarly journals The Superior Hydrothermal Stability of Pd/SSZ-39 in Low Temperature Passive NOx Adsorption (PNA) and Methane Combustion

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Nicholas R. Jaegers ◽  
Libor Kovarik ◽  
Meng Wang ◽  
Jian Zhi Hu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Methane Combustion ◽  
Significant Loss ◽  
Hydrothermal Stability ◽  
Spectroscopic Techniques ◽  
Performance Measurements ◽  
Hydrothermal Aging ◽  
Nox Adsorber ◽  
Nox Adsorption ◽  
Synthesized Materials

We successfully synthesized uniform SSZ-39 with an average crystal size of about a micron. Pd (0.7 - 3 wt%) was supported on SSZ-39 with Si/Al ratio ~12. The as-synthesized materials were characterized by FTIR, XRD, Helium Ion Microscopy, HAADF-STEM imaging, 27Al, 29Si and H solid state NMR spectroscopic techniques. <br>FTIR studies with CO and NO probe molecules reveal that the 0.7 wt% Pd/SSZ-39 material with Si/Al ~12 has the majority of Pd dispersed atomically as isolated Pd(II) and Pd(II)-OH centers, and thus can be used as a low-temperature passive NOx adsorber. Pd(II)-NO, Pd(II)(OH)(NO) and Pd(II)(CO)(NO) complexes form during PNA in this material. We compare this PNA material directly with the Pd/SSZ-13 system (with Si/Al ratio ~12) and show its superior hydrothermal stability. Remarkably, Pd/SSZ-39 with Si/Al ratio ~12 survives hydrothermal aging up to 815 ºC in 10% H2O/Air vapor for 16 hours without significant loss in activity. The SSZ-39 crystal structure remains intact during hydrothermal aging up to 1,000 ºC as we elucidate it with XRD and HAADF-STEM imaging/EDS mapping. However, changes to the framework during such harsh hydrothermal treatment significantly change the NOx release profiles during PNA as evidenced by high-field 27Al NMR on fresh and aged Pd/SSZ-39 samples as well as PNA performance measurements. <br>Besides PNA application, these hydrothermally very stable materials (3 wt% Pd on SSZ-39 with Si/Al ratio ~12) can be used as a robust methane combustion catalyst under industrially relevant conditions (GHSV~600,000hr-1). This catalyst shows minimal deactivation after both harsh hydrothermal aging at 750 and 800 ºC, and prolonged time on stream (105 hrs) at 425 ⁰C. In contrast, both 3wt% Pd/alumina and 3wt% SSZ-13 supported samples lose a significant portion of their activity.<br>

Effect of various activation conditions on the low temperature NO adsorption performance of Pd/SSZ-13 passive NOx adsorber

2019 ◽  
Vol 320 ◽  
pp. 175-180 ◽  
Author(s):  
YoungSeok Ryou ◽  
Jaeha Lee ◽  
Hyokyoung Lee ◽  
Chang Hwan Kim ◽  
Do Heui Kim
Keyword(s):  
Low Temperature ◽  
No Adsorption ◽  
Adsorption Performance ◽  
Nox Adsorber ◽  
Activation Conditions ◽  
Passive Nox Adsorber

A PGM-free NOx adsorber + selective catalytic reduction catalyst system (AdSCR) for trapping and reducing NOx in lean exhaust streams at low temperature

2018 ◽  
Vol 8 (9) ◽  
pp. 2467-2476 ◽  
Author(s):  
Tommaso Selleri ◽  
Federica Gramigni ◽  
Isabella Nova ◽  
Enrico Tronconi ◽  
Simone Dieterich ◽  
...  
Keyword(s):  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Catalyst System ◽  
Selective Catalytic Reduction Catalyst ◽  
Nox Adsorber ◽  
Lean Exhaust

Novel AdSCR systems are able to trap and reduce NOx in lean exhausts at low temperature.

scholarly journals The Superior Hydrothermal Stability of Pd/SSZ-39 in Low Temperature Passive NOx Adsorption (PNA) and Methane Combustion

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Nicholas R. Jaegers ◽  
Libor Kovarik ◽  
Meng Wang ◽  
Jian Zhi Hu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Methane Combustion ◽  
Significant Loss ◽  
Hydrothermal Stability ◽  
Spectroscopic Techniques ◽  
Performance Measurements ◽  
Hydrothermal Aging ◽  
Nox Adsorber ◽  
Nox Adsorption ◽  
Synthesized Materials

We successfully synthesized uniform SSZ-39 with an average crystal size of about a micron. Pd (0.7 - 3 wt%) was supported on SSZ-39 with Si/Al ratio ~12. The as-synthesized materials were characterized by FTIR, XRD, Helium Ion Microscopy, HAADF-STEM imaging, 27Al, 29Si and H solid state NMR spectroscopic techniques. <br>FTIR studies with CO and NO probe molecules reveal that the 0.7 wt% Pd/SSZ-39 material with Si/Al ~12 has the majority of Pd dispersed atomically as isolated Pd(II) and Pd(II)-OH centers, and thus can be used as a low-temperature passive NOx adsorber. Pd(II)-NO, Pd(II)(OH)(NO) and Pd(II)(CO)(NO) complexes form during PNA in this material. We compare this PNA material directly with the Pd/SSZ-13 system (with Si/Al ratio ~12) and show its superior hydrothermal stability. Remarkably, Pd/SSZ-39 with Si/Al ratio ~12 survives hydrothermal aging up to 815 ºC in 10% H2O/Air vapor for 16 hours without significant loss in activity. The SSZ-39 crystal structure remains intact during hydrothermal aging up to 1,000 ºC as we elucidate it with XRD and HAADF-STEM imaging/EDS mapping. However, changes to the framework during such harsh hydrothermal treatment significantly change the NOx release profiles during PNA as evidenced by high-field 27Al NMR on fresh and aged Pd/SSZ-39 samples as well as PNA performance measurements. <br>Besides PNA application, these hydrothermally very stable materials (3 wt% Pd on SSZ-39 with Si/Al ratio ~12) can be used as a robust methane combustion catalyst under industrially relevant conditions (GHSV~600,000hr-1). This catalyst shows minimal deactivation after both harsh hydrothermal aging at 750 and 800 ºC, and prolonged time on stream (105 hrs) at 425 ⁰C. In contrast, both 3wt% Pd/alumina and 3wt% SSZ-13 supported samples lose a significant portion of their activity.<br>

scholarly journals Mn-based mixed oxides for low temperature NOx adsorber applications

2018 ◽  
Vol 567 ◽  
pp. 90-101 ◽  
Author(s):  
Yaying Ji ◽  
Dongyan Xu ◽  
Mark Crocker ◽  
Joseph R. Theis ◽  
Christine Lambert ◽  
...  
Keyword(s):  
Low Temperature ◽  
Mixed Oxides ◽  
Nox Adsorber

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Low temperature x-ray microanalysis of frozen-hydrated tobacco leaves

1984 ◽  
Vol 42 ◽  
pp. 284-285
Author(s):  
S. Edith Taylor ◽  
Patrick Echlin ◽  
May McKoon ◽  
Thomas L. Hayes
Keyword(s):  
Low Temperature ◽  
Lemna Minor ◽  
Root Tips ◽  
Tobacco Leaves ◽  
X Ray ◽  
Whole Cells ◽  
Carbon Coated ◽  
The Right ◽  
Beam Currents ◽  
The University

Low temperature x-ray microanalysis (LTXM) of solid biological materials has been documented for Lemna minor L. root tips. This discussion will be limited to a demonstration of LTXM for measuring relative elemental distributions of P,S,Cl and K species within whole cells of tobacco leaves.Mature Wisconsin-38 tobacco was grown in the greenhouse at the University of California, Berkeley and picked daily from the mid-stalk position (leaf #9). The tissue was excised from the right of the mid rib and rapidly frozen in liquid nitrogen slush. It was then placed into an Amray biochamber and maintained at 103K. Fracture faces of the tissue were prepared and carbon-coated in the biochamber. The prepared sample was transferred from the biochamber to the Amray 1000A SEM equipped with a cold stage to maintain low temperatures at 103K. Analyses were performed using a tungsten source with accelerating voltages of 17.5 to 20 KV and beam currents from 1-2nA.

Bulk standards for low-temperature biological x-ray microanalysis

1984 ◽  
Vol 42 ◽  
pp. 282-283
Author(s):  
P. Echlin ◽  
M. McKoon ◽  
E.S. Taylor ◽  
C.E. Thomas ◽  
K.L. Maloney ◽  
...  
Keyword(s):  
Phase Separation ◽  
Low Temperature ◽  
Analytical Method ◽  
Salt Solutions ◽  
Absolute Concentration ◽  
Cooling Process ◽  
X Ray ◽  
The Absolute ◽  
Analytical Procedures ◽  
Electrical Conductors

Although sections of frozen salt solutions have been used as standards for x-ray microanalysis, such solutions are less useful when analysed in the bulk form. They are poor thermal and electrical conductors and severe phase separation occurs during the cooling process. Following a suggestion by Whitecross et al we have made up a series of salt solutions containing a small amount of graphite to improve the sample conductivity. In addition, we have incorporated a polymer to ensure the formation of microcrystalline ice and a consequent homogenity of salt dispersion within the frozen matrix. The mixtures have been used to standardize the analytical procedures applied to frozen hydrated bulk specimens based on the peak/background analytical method and to measure the absolute concentration of elements in developing roots.

Field ion microscopy

1988 ◽  
Vol 46 ◽  
pp. 434-435
Author(s):  
Gert Ehrlich
Keyword(s):  
Low Temperature ◽  
Sample Surface ◽  
Low Pressure ◽  
Radius Of Curvature ◽  
Field Ion Microscopy ◽  
Phosphor Screen ◽  
Ion Microscopy ◽  
Field Ion Microscope

The field ion microscope, devised by Erwin Muller in the 1950's, was the first instrument to depict the structure of surfaces in atomic detail. An FIM image of a (111) plane of tungsten (Fig.l) is typical of what can be done by this microscope: for this small plane, every atom, at a separation of 4.48Å from its neighbors in the plane, is revealed. The image of the plane is highly enlarged, as it is projected on a phosphor screen with a radius of curvature more than a million times that of the sample. Müller achieved the resolution necessary to reveal individual atoms by imaging with ions, accommodated to the object at a low temperature. The ions are created at the sample surface by ionization of an inert image gas (usually helium), present at a low pressure (< 1 mTorr). at fields on the order of 4V/Å.

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