Enhanced Low-Temperature NOx Conversion by High-Frequency Hydrocarbon Pulsing on a Dual Layer LNT-SCR Catalyst

Low temperature and dilute Homogenous Charge Compression Ignition (HCCI) and Spark Assisted Compression Ignition (SACI) can improve fuel economy and reduce engine-out NOx emissions to very low values, often less than 30 ppm. However, these combustion modes are unable to achieve stringent future regulations such as SULEV 30 without the use of lean aftertreatment. Though active selective catalytic reduction (SCR) with urea injection and lean NOx traps (LNT) have been investigated as options for lean gasoline engines, a passive TWC-SCR system is investigated in this work because it avoids the urea storage and dosing hardware of a urea SCR system, and the high precious metal cost of an LNT. The TWC-SCR concept uses periodic rich operation to produce NH3 over a TWC to be stored on an SCR catalyst for subsequent NOx conversion during lean operation. In this work a laboratory study was performed with a modified 2.0 L gasoline engine that was cycled between lean HCCI and rich SACI operation, or between lean and rich SI (spark ignited) combustion, to evaluate NOx conversion and reduced fuel consumption. Different lambda values during rich operation and different times held in rich operation were investigated. Results are compared to a baseline case in which the engine is always operated at stoichiometric conditions. SCR system simulations are also presented that compare system performance for different levels of stored NH3. With the configuration used in this study, lean/rich HCCI/SACI operation showed a maximum NOx conversion efficiency of 10%, while lean/rich SI operation showed a maximum NOx conversion efficiency of 60%. However, if the low conversion efficiency of lean/rich HCCI/SACI operation could be improved through higher brick temperatures or additional SCR bricks, simulation results indicate TWC-SCR aftertreatment has the potential to provide near-zero SCR-out NOx concentration and increased system fuel efficiency. In these simulations, fuel efficiency improvement relative to stoichiometric SI were 7 to15% for lean/rich HCCI/SACI with zero tailpipe NOx and −1 to 5% for lean/rich SI with zero tailpipe NOx emissions. Although previous work indicated increased time for NH3 to start forming over the TWC during rich operation, less NH3 production over the TWC per fuel amount, and increased NH3 slip over the SCR catalyst for advanced combustion systems, if NOx conversion efficiency could be enhanced, improvements in fuel economy and low engine-out NOx from advanced combustion modes would more than make up for these disadvantages.

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Low-temperature Shift DeNOx Activity of Nanoflake V2O5 loaded WO3/TiO2 as NH3-SCR Catalyst

Inorganic Chemistry Communications ◽

10.1016/j.inoche.2021.109191 ◽

2022 ◽

pp. 109191

Author(s):

Jae Gu Heo ◽

Mahboob Ullah ◽

Myoung-Pyo Chun ◽

Yong Sik Chu ◽

Seong Gwan Seo ◽

...

Keyword(s):

Low Temperature ◽

Temperature Shift ◽

Scr Catalyst ◽

Nh3 Scr

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LOW-TEMPERATURE ION-PLASMA DEPOSITION TECHNOLOGY OF NANOSTRUCTURED FILMS OF ALUMINUM AND BORON NITRIDES

Optoelektronìka ta napìvprovìdnikova tehnìka ◽

10.15407/iopt.2021.56.097 ◽

2021 ◽

Vol 56 ◽

pp. 97-107

Author(s):

M. S. Zayats ◽

Keyword(s):

Dielectric Properties ◽

Low Temperature ◽

Magnetron Sputtering ◽

High Frequency ◽

Plasma Deposition ◽

Heating Temperature ◽

Substrate Heating ◽

Ion Plasma ◽

Technological Cycle ◽

Physical And Chemical

A low-temperature (substrate heating temperature up to 400 °C) ion-plasma technology for the formation of nanostructured AlN and BN films by the method of high-frequency reactive magnetron sputtering of the corresponding targets has been developed (the modernized installation "Cathode-1M"), which has in its technological cycle the means of physical and chemical modification, which allow to purposefully control the phase composition, surface morphology, size and texture of nanocrystalline films. The possibility of using the method of high-frequency magnetron sputtering for deposition of transparent hexagonal BN films in the nanoscale state on quartz and silicon substrates is shown. Atomic force microscopy (AFM) has shown that AlN films can have an amorphous or polycrystalline surface with grain sizes of approximately 20-100 nm, with the height of the nanoparticles varying from 3 to 10 nm and the degree of surface roughness from 1 to 10 nm. It was found that the dielectric penetration of polycrystalline AlN films decreases from 10 to 3.5 at increased frequencies from 25 Hz to 1 MHz, and the peak tangent of the dielectric loss angle reaches 0.2 at 10 kHz. Such features indicate the existence of spontaneous polarization of dipoles in the obtained AlN films. Interest in dielectric properties in AlN / Si structures it is also due to the fact that there are point defects, such as nitrogen vacancies and silicon atoms, which diffuse from the silicon substrate during synthesis and play an important role in the dielectric properties of AlN during the formation of dipoles. The technology makes it possible, in a single technological cycle, to produce multilayer structures modified for specific functional tasks with specified characteristics necessary for the manufacture of modern electronics, optoelectronics and sensorics devices. It should also be noted that the technology of magnetron sputtering (installation "Cathode-1M") is highly productive, energetically efficient and environmentally friendly in comparison with other known technologies for creating semiconductor structures and allows them to be obtained with minimal changes in the technological cycle.

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Effects of Electrically Heated Catalyst on the Low Temperature Performance of Vanadium-Based SCR Catalyst on Diesel Engine

10.4271/2014-01-1527 ◽

2014 ◽

Cited By ~ 3

Author(s):

Xiangyu Feng ◽

Yunshan Ge ◽

Jianwei Tan ◽

Jiaqiang Li ◽

Yao Zhang ◽

...

Keyword(s):

Diesel Engine ◽

Low Temperature ◽

Scr Catalyst ◽

Temperature Performance ◽

Low Temperature Performance

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An Efficient Two-Step Method for NH3 Removal at Low Temperature Using CoOx-CuOx/TiO2 as SCO Catalyst Followed by NiMn2O4 as SCR Catalyst

Energy & Fuels ◽

10.1021/acs.energyfuels.7b01329 ◽

2017 ◽

Vol 31 (8) ◽

pp. 8580-8593 ◽

Cited By ~ 6

Author(s):

Xiaolong Tang ◽

Jingying Li ◽

Honghong Yi ◽

Qingjun Yu ◽

Fengyu Gao ◽

...

Keyword(s):

Low Temperature ◽

Step Method ◽

Scr Catalyst

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Enhanced microstructure and dielectric properties of low-temperature sintered MgO-xwt%LiF ceramics for high-frequency applications

Ceramics International ◽

10.1016/j.ceramint.2021.10.055 ◽

2021 ◽

Author(s):

Zheng Liang ◽

Jie Li ◽

Jian Wu ◽

Yan Yang ◽

Bing Lu ◽

...

Keyword(s):

Dielectric Properties ◽

Low Temperature ◽

High Frequency

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The impact of treating graphene oxide with a pulsed high-frequency discharge on the low-temperature sorption of hydrogen

Low Temperature Physics ◽

10.1063/10.0000701 ◽

2020 ◽

Vol 46 (3) ◽

pp. 293-300 ◽

Cited By ~ 1

Author(s):

A. V. Dolbin ◽

N. A. Vinnikov ◽

V. B. Esel’son ◽

V. G. Gavrilko ◽

R. M. Basnukaeva ◽

...

Keyword(s):

Graphene Oxide ◽

Low Temperature ◽

High Frequency ◽

High Frequency Discharge ◽

The Impact

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The Effect of Tourmaline on SCR Denitrification Activity of MnOx/TiO2 at Low Temperature

Catalysts ◽

10.3390/catal10091020 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1020

Author(s):

Yizhe Helian ◽

Suping Cui ◽

Xiaoyu Ma

Keyword(s):

Low Temperature ◽

Catalytic Reduction ◽

Catalytic Performance ◽

Scr Catalyst ◽

Highly Efficient ◽

Nh3 Scr ◽

Catalytic Material ◽

Acidic Sites ◽

Denitrification Activity ◽

The Stability

Selective catalytic reduction (SCR) technology is the most widely used flue gas denitration technology at present. The stability of a catalyst is the main factor limiting the development of this technology. In this study, an environmentally friendly and highly efficient NH3-SCR catalyst was prepared by coprecipitation method from acidolysis residue of industrial waste and tourmaline. We found that the addition of tourmaline has an important impact on the denitration activity of the catalytic material. The NOx conversion exceeded 97% at 200 °C with the dosage of 10% tourmaline, which is about 7% higher than that without doping. The improvement of catalytic performance was mostly attributed to the permanent electrodes of tourmaline, which effectively promotes the dispersion of MnOx/TiO2 catalytic materials, increases the number of acidic sites and changes the valence distribution of manganese ions in products, which speeds up the diffusion of protons and ions, resulting in the acceleration of redox reaction. These as-developed tourmaline-modified MnOx/TiO2 materials have been demonstrated to be promising as a new type of highly efficient low-temperature NH3-SCR catalyst.

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