scholarly journals Effect of Zirconia Polymorph on Vapor-Phase Ketonization of Propionic Acid

Catalysts ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 768 ◽  
Author(s):  
Shuang Ding ◽  
Jiankang Zhao ◽  
Qiang Yu
Keyword(s):  
Propionic Acid ◽  
Vapor Phase ◽  
Surface Concentration ◽  
X Ray Diffraction ◽  
In Situ Drifts ◽  
X Ray ◽  
Surface Intermediates ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared

Vapor-phase ketonization of propionic acid derived from biomass was studied at 300–375 °C over ZrO2 with different zirconia polymorph. The tetragonal ZrO2 (t-ZrO2) are more active than monoclinic ZrO2 (m-ZrO2). The results of characterizations from X-ray diffraction (XRD) and Raman suggest m-ZrO2 and t-ZrO2 are synthesized by the solvothermal method. NH3 and CO2 temperature-programmed desorption (NH3-TPD and CO2-TPD) measurements show that there were more medium-strength Lewis acid base sites with lower coordination exposed on m-ZrO2 relative to t-ZrO2, increasing the adsorption strength of propionic acid. The in situ DRIFTS (Diffuse reflectance infrared Fourier transform spectroscopy) of adsorbed propionic acid under ketonization reaction reveal that as the most abundant surface intermediates, the monodentate propionates are more active than bidentate propionates. In comparison with m-ZrO2, the t-ZrO2 surface favors monodentate adsorption over bidentate adsorption. Additionally, the adsorption strength of monodentate propionate is weaker on t-ZrO2. These differences in adsorption configuration and adsorption strength of propionic acid are affected by the zirconia structure. The higher surface concentration and weaker adsorption strength of monodentate propionates contribute to the higher ketonization rate in the steady state.

scholarly journals “PdO vs. PtO”—The Influence of PGM Oxide Promotion of Co3O4 Spinel on Direct NO Decomposition Activity

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 62 ◽  
Author(s):  
Gunugunuri K. Reddy ◽  
Torin C. Peck ◽  
Charles A. Roberts
Keyword(s):  
Photoelectron Spectroscopy ◽  
No Decomposition ◽  
Single Element ◽  
X Ray Diffraction ◽  
X Ray ◽  
Promotional Effect ◽  
Ft Ir ◽  
Temperature Programmed ◽  
Thermal Stability Of

Direct decomposition of NO into N2 and O2 (2NO→N2 + O2) is recognized as the “ideal” reaction for NOx removal because it needs no reductant. It was reported that the spinel Co3O4 is one of the most active single-element oxide catalysts for NO decomposition at higher reaction temperatures, however, activity remains low below 650 °C. The present study aims to investigate new promoters for Co3O4, specifically PdO vs. PtO. Interestingly, the PdO promoter effect on Co3O4 was much greater than the PtO effect, yielding a 4 times higher activity for direct NO decomposition at 650 °C. Also, Co3O4 catalysts with the PdO promoter exhibit higher selectivity to N2 compared to PtO/Co3O4 catalysts. Several characterization measurements, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), and in situ FT-IR, were performed to understand the effect of PdO vs. PtO on the properties of Co3O4. Structural and surface analysis measurements show that impregnation of PdO on Co3O4 leads to a greater ease of reduction of the catalysts and an increased thermal stability of surface adsorbed NOx species, which contribute to promotion of direct NO decomposition activity. In contrast, rather than remaining solely as a surface species, PtO enters the Co3O4 structure, and it promotes neither redox properties nor NO adsorption properties of Co3O4, resulting in a diminished promotional effect compared to PdO.

scholarly journals In-Exchanged CHA Zeolites for Selective Dehydrogenation of Ethane: Characterization and Effect of Zeolite Framework Type

Catalysts ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 807
Author(s):  
Zen Maeno ◽  
Xiaopeng Wu ◽  
Shunsaku Yasumura ◽  
Takashi Toyao ◽  
Yasuharu Kanda ◽  
...  
Keyword(s):  
Active Sites ◽  
Temperature Programmed Desorption ◽  
X Ray Diffraction ◽  
Zeolite Framework ◽  
X Ray ◽  
Catalytic Activities ◽  
Ethane Dehydrogenation ◽  
Temperature Programmed

In this study, the characterization of In-exchanged CHA zeolite (In-CHA (SiO2/Al2O3 = 22.3)) was conducted by in-situ X-ray diffraction (XRD) and ammonia temperature-programmed desorption (NH3-TPD). We also prepared other In-exchanged zeolites with different zeolite structures (In-MFI (SiO2/Al2O3 = 22.3), In-MOR (SiO2/Al2O3 = 20), and In-BEA (SiO2/Al2O3 = 25)) and different SiO2/Al2O3 ratios (In-CHA(Al-rich) (SiO2/Al2O3 = 13.7)). Their catalytic activities in nonoxidative ethane dehydrogenation were compared. Among the tested catalysts, In-CHA(Al-rich) provided the highest conversion. From kinetic experiments and in-situ Fourier transform infrared (FTIR) spectroscopy, [InH2]+ ions are formed regardless of SiO2/Al2O3 ratio, serving as the active sites.

Chemical Vapor Functionalization of ZnO Nanocrystals

2010 ◽  
Vol 1260 ◽  
Author(s):  
Moazzam Ali ◽  
Marty D. Donakowski ◽  
Markus Winterer
Keyword(s):  
Gas Phase ◽  
Diffuse Reflectance ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zno Nanocrystals ◽  
In Series ◽  
Lower Temperature ◽  
Diffuse Reflectance Infrared

AbstractChemical Vapor Functionalization (CVF) is a method in which nanocrystals undergo in situ functionalization in the gas phase. In CVF, two reactors are used in series. The first reactor consists of a hot quartz tube (1073 K) where ZnO nanocrystals are synthesized in the gas phase from diethylzinc and oxygen. The second reactor, connected at the exit of the first one and kept at lower temperature (673 K), is used as functionalization chamber. At the connecting point of the two reactors, vapors of organic functionalizing agents are injected which react with the surface of ZnO nanocrystals. ZnO nanocrystals have been functionalized by 1-hexanol, n-hexanoic acid, n-hexanal and 1-hexylamine. Functionalized ZnO nanocrystals have been characterized by Dynamic Light Scattering, X-ray Diffraction and Diffuse Reflectance Infrared Fourier Transform Spectroscopy.

scholarly journals Modification of V2O5-WO3/TiO2 Catalyst by Loading of MnOx for Enhanced Low-Temperature NH3-SCR Performance

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1900
Author(s):  
Xianlong Zhang ◽  
Qinchao Diao ◽  
Xiaorui Hu ◽  
Xueping Wu ◽  
Kesong Xiao ◽  
...  
Keyword(s):  
Manganese Oxides ◽  
Catalytic Reduction ◽  
In Situ Growth ◽  
X Ray Diffraction ◽  
Scr Catalyst ◽  
X Ray ◽  
Nh3 Scr ◽  
Growth Method ◽  
Temperature Programmed

V2O5-WO3/TiO2 as a commercial selective catalytic reduction (SCR) catalyst usually used at middle-high temperatures was modified by loading of MnOx for the purpose of enhancing its performance at lower temperatures. Manganese oxides were loaded onto V-W/Ti monolith by the methods of impregnation (I), precipitation (P), and in-situ growth (S), respectively. SCR activity of each modified catalyst was investigated at temperatures in the range of 100–340 °C. Catalysts were characterized by specific surface area and pore size determination (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), etc. Results show that the loading of MnOx remarkably enhanced the SCR activity at a temperature lower than 280 °C. The catalyst prepared by the in-situ growth method was found to be most active for SCR.

scholarly journals Applicability of V2O5-WO3/TiO2 Catalysts for the SCR Denitrification of Alumina Calcining Flue Gas

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 220 ◽  
Author(s):  
Ruliang Ning ◽  
Li Chen ◽  
Erwei Li ◽  
Xiaolong Liu ◽  
Tingyu Zhu
Keyword(s):  
Flue Gas ◽  
Photoelectron Spectroscopy ◽  
Catalytic Performance ◽  
Inhibitory Effect ◽  
Impregnation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
So2 Resistance ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared

V2O5-WO3/TiO2 catalysts with different V2O5 and WO3 loadings were prepared by the impregnation method. H2O and SO2 resistance of the catalysts under high H2O concentration (30 vol.%) was studied. Influence of various basic metal oxides, such as Al2O3, CaO, Na2O, and K2O on the catalytic performance was studied and compared. It is revealed that the inhibitory effect is in the sequence of K > Na > Ca > Al, which is consistent with their alkalinity. X-ray diffraction (XRD), N2 physisorption (BET), temperature-programmed desorption of NH3 (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were carried out, and the results were well-correlated with the catalytic studies.

Thermally induced transformations of Au@Cu2O core–shell nanoparticles into Au–Cu nanoparticles from temperature-programmed in situ powder X-ray diffraction

2019 ◽  
Vol 52 (3) ◽  
pp. 579-586 ◽  
Author(s):  
Robert Koch ◽  
Guangfang Li ◽  
Shubham Pandey ◽  
Simon Phillpot ◽  
Hui Wang ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Core Shell ◽  
X Ray Diffraction ◽  
Shell Nanoparticles ◽  
Thermally Induced ◽  
X Ray ◽  
Cu Content ◽  
Temperature Programmed ◽  
Core Shell Nanoparticles

Temperature-programmed in situ X-ray diffraction with whole-powder-pattern modeling is used to investigate the reaction of Au@Cu2O core–shell nanoparticles to form nanocrystalline bimetallic Cu x Au1−x alloys (x = 0, 0.25, 0.5, 0.75, 1.0) in a reducing atmosphere. The mechanisms of the reactions are key to informed design of tailored non-equilibrium nanostructures for catalytic and plasmonic materials. The Au@Cu2O reaction is initiated by reduction of the Cu2O cuprite shell to form nanocrystalline metallic Cu at about 413 K. Alloying begins immediately upon formation of metallic Cu at 413 K, with the nucleation of an Au-rich alloy phase which reaches the nominal Cu content of the overall system stoichiometry by 493 K. All bimetallic alloys form a transient ordered Cu3Au intermetallic compound at intermediate temperatures, with the onset of ordering and subsequent disordering varying by composition. No evidence for an ordered Au3Cu intermetallic is found for any composition. Significant crystal growth in the bimetallic phase is apparent at higher temperatures, with the onset temperature increasing with Cu concentration and initial Cu-shell thickness. The reduction of the cuprite phase is slowed by the presence of the core–shell interface, and crystal growth in the Cu shell is completely suppressed within the alloy systems.

scholarly journals Characterization of Highly Dispersed Rod- and Particle-Shaped CuFe19Ox Catalysts and Their Shape Effects on WGS

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 635
Author(s):  
Lingjuan Ma ◽  
Dawei Han ◽  
Hongbin Ma ◽  
Longgang Liu ◽  
Huichao Guo
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
In Situ Xrd ◽  
Transmission Electron ◽  
Highly Dispersed ◽  
Shape Effects ◽  
Temperature Programmed ◽  
Water Gas

Highly dispersed CuFe19Ox catalysts with different shapes were prepared and further characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), and in-situ XRD. XRD and TEM results showed that the synthesized CuFe19Ox nanoparticles consisted of CuO and Fe2O3, while CuFe19Ox nanorods consisted of CuFe2O4 and Fe2O3. The reduction properties of CuFe19Ox samples were finely studied by H2-TPR, and the phase composition was identified by in-situ XPS, HR-TEM, and surface TPR (s-TPR). In-situ X-ray photoelectroscopy (XPS) indicated that the metallic Cu and Fe3O4 were the main species after reduction. Moreover, s-TPR studies showed that the reduction performance of copper was significantly affected by the shapes of the Fe3O4 supports. Low-temperature water gas shift (LT-WGS) was chosen to characterize the Cu species on the surface. It was found that reduced CuFe19Ox nanorods had no activity. On the contrary, reduced CuFe19Ox particles showed higher initial WGS activity, where the active Cu0 should originate from the reduction of Cu2O at lower temperatures, as confirmed by the s-TPR profiles.

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