scholarly journals The impact of steam on the electronic structure of the selective propane oxidation catalyst MoVTeNb oxide (orthorhombic M1 phase)

2015 ◽  
Vol 17 (14) ◽  
pp. 8983-8993 ◽  
Author(s):  
Christian Heine ◽  
Michael Hävecker ◽  
Annette Trunschke ◽  
Robert Schlögl ◽  
Maik Eichelbaum
Keyword(s):  
Electronic Structure ◽  
Acrylic Acid ◽  
Surface Structure ◽  
Propane Oxidation ◽  
Oxidation Catalyst ◽  
M1 Phase ◽  
The Impact

Steam modifies the surface structure of the propane oxidation catalyst MoVTeNbOx and increases the selectivity to the product acrylic acid.

STEM HAADF Image Simulation of the Orthorhombic M1 Phase in the Mo-V-Nb-Te-O Propane Oxidation Catalyst

ChemCatChem ◽  
2011 ◽  
Vol 3 (6) ◽  
pp. 1028-1033 ◽  
Author(s):  
Douglas A. Blom ◽  
Xin Li ◽  
Sonali Mitra ◽  
Thomas Vogt ◽  
Douglas J. Buttrey
Keyword(s):  
Propane Oxidation ◽  
Oxidation Catalyst ◽  
Image Simulation ◽  
M1 Phase ◽  
Haadf Image

scholarly journals The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 336
Author(s):  
Deniz Zengel ◽  
Simon Barth ◽  
Maria Casapu ◽  
Jan-Dierk Grunwaldt
Keyword(s):  
Catalytic Reduction ◽  
Elevated Pressure ◽  
Systematic Investigation ◽  
Diesel Oxidation Catalyst ◽  
Zeolite Catalysts ◽  
Oxidation Catalyst ◽  
Pollutant Concentrations ◽  
Oxidation Of Hydrocarbons ◽  
Negative Effect ◽  
The Impact

Positioning the catalysts in front of the turbocharger has gained interest over recent years due to the earlier onset temperature and positive effect of elevated pressure. However, several challenges must be overcome, like presence of higher pollutant concentrations due to the absence or insufficient diesel oxidation catalyst volume at this location. In this context, our study reports a systematic investigation on the effect of pressure and various hydrocarbons during selective catalytic reduction (SCR) of NOx with NH3 over the zeolite-based catalysts Fe-ZSM-5 and Cu-SSZ-13. Using a high-pressure catalyst test bench, the catalytic activity of both zeolite catalysts was measured in the presence and absence of a variety of hydrocarbons under pressures and temperatures resembling the conditions upstream of the turbocharger. The results obtained showed that the hydrocarbons are incompletely converted over both catalysts, resulting in numerous byproducts. The emission of hydrogen cyanide seems to be particularly problematic. Although the increase in pressure was able to improve the oxidation of hydrocarbons and significantly reduce the formation of HCN, sufficiently low emissions could only be achieved at high temperatures. Regarding the NOx conversion, a boost in activity was obtained by increasing the pressure compared to atmospheric reaction conditions, which compensated the negative effect of hydrocarbons on the SCR activity.

EGR cylinder deactivation strategy to accelerate the warm-up and restart processes in a Diesel engine operating at cold conditions

2021 ◽  
pp. 146808742110395
Author(s):  
José Galindo ◽  
Vicente Dolz ◽  
Javier Monsalve-Serrano ◽  
Miguel Angel Bernal Maldonado ◽  
Laurent Odillard
Keyword(s):  
Steady State ◽  
Diesel Engine ◽  
Internal Combustion Engines ◽  
Cold Start ◽  
Pollutant Emissions ◽  
Oxidation Catalyst ◽  
Maximum Efficiency ◽  
Warm Up ◽  
Cylinder Deactivation ◽  
The Impact

The aftertreatment systems used in internal combustion engines need high temperatures for reaching its maximum efficiency. By this reason, during the engine cold start period or engine restart operation, excessive pollutant emissions levels are emitted to the atmosphere. This paper evaluates the impact of using a new cylinder deactivation strategy on a Euro 6 turbocharged diesel engine running under cold conditions (−7°C) with the aim of improving the engine warm-up process. This strategy is evaluated in two parts. First, an experimental study is performed at 20°C to analyze the effect of the cylinder deactivation strategy at steady-state and during an engine cold start at 1500 rpm and constant load. In particular, the pumping losses, pollutant emissions levels and engine thermal efficiency are analyzed. In the second part, the engine behavior is analyzed at steady-state and transient conditions under very low ambient temperatures (−7°C). In these conditions, the results show an increase of the exhaust temperatures of around 100°C, which allows to reduce the diesel oxidation catalyst light-off by 250 s besides of reducing the engine warm-up process in approximately 120 s. This allows to reduce the CO and HC emissions by 70% and 50%, respectively, at the end of the test.

scholarly journals Accuracy and Reliability in the Simulation of Vibrational Spectra: A Comprehensive Benchmark of Energies and Intensities Issuing From Generalized Vibrational Perturbation Theory to Second Order (GVPT2)

2021 ◽  
Vol 8 ◽  
Author(s):  
Qin Yang ◽  
Marco Mendolicchio ◽  
Vincenzo Barone ◽  
Julien Bloino
Keyword(s):  
Perturbation Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Computational Cost ◽  
Theoretical Data ◽  
Infrared Region ◽  
Second Order ◽  
Basis Set ◽  
Molecular Systems ◽  
The Impact

Vibrational spectroscopy represents an active frontier for the identification and characterization of molecular species in the context of astrochemistry and astrobiology. As new missions will provide more data over broader ranges and at higher resolution, especially in the infrared region, which could be complemented with new spectrometers in the future, support from laboratory experiments and theory is crucial. In particular, computational spectroscopy is playing an increasing role in deepening our understanding of the origin and nature of the observed bands in extreme conditions characterizing the interstellar medium or some planetary atmospheres, not easily reproducible on Earth. In this connection, the best compromise between reliability, feasibility and ease of interpretation is still a matter of concern due to the interplay of several factors in determining the final spectral outcome, with larger molecular systems and non-covalent complexes further exacerbating the dichotomy between accuracy and computational cost. In this context, second-order vibrational perturbation theory (VPT2) together with density functional theory (DFT) has become particularly appealing. The well-known problem of the reliability of exchange-correlation functionals, coupled with the treatment of resonances in VPT2, represents a challenge for the determination of standardized or “black-box” protocols, despite successful examples in the literature. With the aim of getting a clear picture of the achievable accuracy and reliability of DFT-based VPT2 calculations, a multi-step study will be carried out here. Beyond the definition of the functional, the impact of the basis set and the influence of the resonance treatment in VPT2 will be analyzed. For a better understanding of the computational aspects and the results, a short summary of vibrational perturbation theory and the overall treatment of resonances for both energies and intensities will be given. The first part of the benchmark will focus on small molecules, for which very accurate experimental and theoretical data are available, to investigate electronic structure calculation methods. Beyond the reliability of energies, widely used for such systems, the issue of intensities will also be investigated in detail. The best performing electronic structure methods will then be used to treat larger molecular systems, with more complex topologies and resonance patterns.

scholarly journals Deswelling Induced Morphological Changes in Dual pH and Temperature Responsive Ultra-Low Crosslinked Poly (N-Isopropyl Acrylamide)-Co-Acrylic Acid Microgels

2018 ◽  
Author(s):  
Molla Islam ◽  
Maddie Tumbarello ◽  
Andrew Lyon
Keyword(s):  
Light Scattering ◽  
Acrylic Acid ◽  
Morphological Changes ◽  
Scattering Data ◽  
Ionization State ◽  
Force Microscopy ◽  
Temperature Responsive ◽  
Atomic Force ◽  
Isopropyl Acrylamide ◽  
The Impact

<div>We demonstrated the deswelling induced morphological change in dual pH and Temperature responsive ultra-low crosslinked Poly (N-isopropyl acrylamide)-co-acrylic acid microgels. The responsivity with pH and temperature were studied by light scattering and atomic force microscopy. Light scattering data suggest that at pH 4.5 the microgels undergo multiple transitions associated with collapse of pNIPAm-rich segments and repulsion between the AAc-rich segments. The evolution of punctate structures around the periphery or throughout the whole microgels at pH 4.5 and 6.5 respectively was revealed by AFM, further illustrating the heterogeneous deswelling present in the ionized copolymer microgels.</div><div>The impact of this study and understanding how ionization state of copolymer dictates the overall structural properties of microgels will widen our understanding for their applications in biotechnology</div><div><b><br></b></div>

The Effect of Chitosan Addition in Acrylic Resin Matrix towards the Residual Monomers and Impact Strength

2021 ◽  
pp. 2280-2285
Author(s):  
Titik Ismiyati ◽  
Ananto Ali Alhasyimi
Keyword(s):  
Acrylic Acid ◽  
Impact Strength ◽  
Charpy Impact ◽  
Acrylic Resin ◽  
Test Sample ◽  
Acid Group ◽  
Resin Matrix ◽  
Residual Monomer ◽  
Group 2 ◽  
The Impact

Background: A residual monomer might have impact on the quality of acrylic resin since its caused allergic reactions and inflammation. Chitosan is a biocompatible material and potential to reduce residual monomers and ameliorate the impact strength of acrylic resin Objective of the study: To examine the effect of an acrylic resin matrix mixed with chitosan together with 1% and 2% acrylic acid as denture base and orthodontic material on residual monomers and impact strength. Methodology: There were 30 samples for the test analysis. The impact strength test sample formed with a plate size of 55 × 10 × 10mm, whereas the residual monomer test sample was prepared into powder. The test samples were divided into 3 groups, of 10 samples. Group 1 acrylic resin only, group 2 acrylic resin matrix mixed with chitosan and 1% acrylic acid, group 3 is the same as group 2 but with a concentration of 2% acrylic acid. Gas chromatography was used for measuring the residual monomers. The impact strength was tested by the Charpy impact. The data was evaluated using the ANOVA and correlation test. Results: There were significant differences (p < 0.05) in acrylic resin without addition with the matrix of acrylic resin with chitosan and acrylic acid 1% and 2% to the number of monomers and impact strength. Conclusion: The mixture of acrylic resin with chitosan and acrylic acid 1% and 2% can reduce the amount of residual monomer and increase the impact strength.

High-precision synthesis of α-MnO2 nanowires with controllable crystal facets for propane oxidation

CrystEngComm ◽  
2021 ◽  
Author(s):  
Chao Feng ◽  
Gaoyan Xiong ◽  
Yaping Li ◽  
Qianqian Gao ◽  
Yuan Pan ◽  
...  
Keyword(s):  
High Precision ◽  
Propane Oxidation ◽  
Oxidation Catalyst ◽  
Crystal Facet ◽  
Reaction Performance ◽  
Precision Synthesis ◽  
Mno2 Nanowires

Determining the effect of crystal facet on the reaction performance is essential for designing an efficient propane oxidation catalyst. Herein, α-MnO2 nanowires with exposed (110), (211), (310) and (200) facets...

scholarly journals The Impact of Surface Structure Transformations on the Performance of Li-Excess Cation-Disordered Rocksalt Cathodes

2020 ◽  
Vol 1 (9) ◽  
pp. 100187
Author(s):  
Deok-Hwang Kwon ◽  
Jinhyuk Lee ◽  
Nongnuch Artrith ◽  
Hyunchul Kim ◽  
Lijun Wu ◽  
...  
Keyword(s):  
Surface Structure ◽  
The Impact
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