scholarly journals Influence of the ZrO2 Crystalline Phases on the Nature of Active Sites in PdCu/ZrO2 Catalysts for the Methanol Steam Reforming Reaction—An In Situ Spectroscopic Study

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1005
Author(s):  
Daniel Ruano ◽  
Beatriz M. Pabón ◽  
Càtia Azenha ◽  
Cecilia Mateos-Pedrero ◽  
Adélio Mendes ◽  
...  
Keyword(s):  
Steam Reforming ◽  
Active Sites ◽  
Surface Composition ◽  
Ambient Pressure ◽  
Chemical Properties ◽  
Spectroscopic Studies ◽  
Metal Species ◽  
Methanol Steam Reforming ◽  
Reaction Products

In this work, the electronic properties of the metal sites in cubic and monoclinic ZrO2 supported Pd and PdCu catalysts have been investigated using CO as probe molecule in in-situ IR studies, and the surface composition of the outermost layers has been studied by APXPS (Ambient Pressure X-ray Photoemission Spectroscopy). The reaction products were followed by mass spectrometry, making it possible to relate the chemical properties of the catalysts under reaction conditions with their selectivity. Combining these techniques, it has been shown that the structure of the support (monoclinic or cubic ZrO2) affects the metal dispersion, mobility, and reorganization of metal sites under methanol steam reforming (MSR) conditions, influencing the oxidation state of surface metal species, with important consequences in the catalytic activity. Correlating the mass spectra of the reaction products with these spectroscopic studies, it was possible to conclude that electropositive metal species play an imperative role for high CO2 and H2 selectivity in the MSR reaction (less CO formation).

scholarly journals In situ X-ray absorption spectroscopic studies of TiO2 photocatalytic active sites for degradation of trace CHCl3 in drinking water

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
T.-L. Hsiung ◽  
L.-W. Wei ◽  
H.-L. Huang ◽  
H. Paul Wang
Keyword(s):  
Drinking Water ◽  
Photocatalytic Degradation ◽  
Active Sites ◽  
Spectroscopic Studies ◽  
Band Gap Energy ◽  
Disinfection Byproducts ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Toxic disinfection byproducts such as trihalomethanes (e.g. CHCl3) are often found after chlorination of drinking water. It has been found that photocatalytic degradation of trace CHCl3 in drinking water generally lacks an expected relationship with the crystalline phase, band-gap energy or the particle sizes of the TiO2-based photocatalysts used such as nano TiO2 on SBA-15 (Santa Barbara amorphous-15), TiO2 clusters (TiO2–SiO2) and atomic dispersed Ti [Ti-MCM-41 (Mobil Composition of Matter)]. To engineer capable TiO2 photocatalysts, a better understanding of their photoactive sites is of great importance and interest. Using in situ X-ray absorption near-edge structure (XANES) spectroscopy, the A1 (4969 eV), A2 (4971 eV) and A3 (4972 eV) sites in TiO2 can be distinguished as four-, five- and six- coordinated Ti species, respectively. Notably, the A2 Ti sites that are the main photocatalytic species of TiO2 are shown to be accountable for about 95% of the photocatalytic degradation of trace CHCl3 in drinking water (7.2 p.p.m. CHCl3 gTiO2 −1 h−1). This work reveals that the A2 Ti species of a TiO2-based photocatalyst are mainly responsible for the photocatalytic reactivity, especially in photocatalytic degradation of CHCl3 in drinking water.

scholarly journals The Promoting Effect of Ni on Glycerol Hydrogenolysis to 1,2-Propanediol with In Situ Hydrogen from Methanol Steam Reforming Using a Cu/ZnO/Al2O3 Catalyst

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 412 ◽  
Author(s):  
Yuanqing Liu ◽  
Xiaoming Guo ◽  
Garry Rempel ◽  
Flora Ng
Keyword(s):  
Steam Reforming ◽  
Molecular Hydrogen ◽  
Biodiesel Production ◽  
Precipitation Method ◽  
Methanol Steam Reforming ◽  
Phase Reaction ◽  
Promoting Effect ◽  
High Hydrogen ◽  
Al2o3 Catalyst

Production of green chemicals using a biomass derived feedstock is of current interest. Among the processes, the hydrogenolysis of glycerol to 1,2-propanediol (1,2-PD) using externally supplied molecular hydrogen has been studied quite extensively. The utilization of methanol present in crude glycerol from biodiesel production can avoid the additional cost for molecular hydrogen storage and transportation, as well as reduce the safety risks due to the high hydrogen pressure operation. Recently the hydrogenolysis of glycerol with a Cu/ZnO/Al2O3 catalyst using in situ hydrogen generated from methanol steam reforming in a liquid phase reaction has been reported. This paper focusses on the effect of added Ni on the activity of a Cu/ZnO/Al2O3 catalyst prepared by an oxalate gel-co-precipitation method for the hydrogenolysis of glycerol using methanol as a hydrogen source. It is found that Ni reduces the conversion of glycerol but improves the selectivity to 1,2-PD, while a higher conversion of methanol is observed. The promoting effect of Ni on the selectivity to 1,2-PD is attributed to the slower dehydration of glycerol to acetol coupled with a higher availability of in situ hydrogen produced from methanol steam reforming and the higher hydrogenation activity of Ni towards the intermediate acetol to produce 1,2-PD.

Characteristic of Cu-Based Catalytic Coating for Methanol Steam Reforming Prepared by Cold Spray

2010 ◽  
Vol 156-157 ◽  
pp. 68-73 ◽  
Author(s):  
Feng Wang ◽  
Jing Zhou ◽  
Zi Long An ◽  
Xin Jing Zhou
Keyword(s):  
Cold Spray ◽  
Steam Reforming ◽  
Fixed Bed ◽  
Copper Coating ◽  
Methanol Steam Reforming ◽  
Reaction Products ◽  
Al2o3 Coating ◽  
Transfer Resistance ◽  
Catalytic Coating ◽  
Al2o3 Composite

Cu-based catalyst is active for methanol steam reforming (MSR) at low temperature. The Cu、Cu+Al2O3 composite and CuO/ZnO/Al2O3 catalytic powers are used as feedstock for coating fabrication by cold spray. MSR experiment and SEM、EDX 、XRD analysis before and after the MSR on the coating has been carried out to study the micostructure and catalytic characteristic of the deposits. Results show that, after reaction the morphology of the Cu coating changes from piled sheets structure to mciro-ramify structure, its porosity obviously increase, the net weight of O、Al in the coating increases, H2 content in the reaction products reaches 74.9%. While for the Cu+Al2O3 composite coating, the content of copper in the coating decreases compared with the initial powder, and the stability of Cu+Al2O3 coating is better than the copper coating in MSR reaction. Particle bonding between coating and substrate and the bonding between the particles in the coating is mainly belonged to mechanical bite and physical bonding; Porosity in the latter two coating is higher than the copper coating. But there is no phase change of the coating. CuO/ZnO/Al2O3 coating shows a much higher activity than conventional fixed bed catalyst due to the reduction of heat and mass transfer resistance in the reactor. So it is available to fabricate catalytic coating by cold spray.

Temperature dependence of Cu–Al spinel formation and its catalytic performance in methanol steam reforming

2017 ◽  
Vol 7 (21) ◽  
pp. 5069-5078 ◽  
Author(s):  
Yajie Liu ◽  
Shaojun Qing ◽  
Xiaoning Hou ◽  
Fajie Qin ◽  
Xiang Wang ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Steam Reforming ◽  
Catalytic Performance ◽  
Methanol Steam Reforming ◽  
Spinel Formation ◽  
Synthetic Temperature

Synthetic temperature strongly influences the properties of Cu1−3xVxAl2+2xO4. Active Cu generated in situ can be stabilized by defect spinels.

Hydrogen from bioethanol: Catalytic honeycombs loaded with Co-Fe/ZnOfor small-scale energy applications

2011 ◽  
Vol 1326 ◽  
Author(s):  
Cristian Ledesma ◽  
Maria Roig ◽  
Jordi Llorca
Keyword(s):  
Steam Reforming ◽  
Molar Ratio ◽  
Small Scale ◽  
Reaction Products ◽  
Energy Applications ◽  
Steam Reforming Of Ethanol ◽  
One Step ◽  
Ethanol Steam ◽  
Urea Method

ABSTRACTCatalytic monoliths loaded with ZnO-supported Co-Fe catalysts were prepared in one step by the in situ urea method and tested in the ethanol steam reforming reaction to produce hydrogen. The most active and selective formulation was attained with a Fe/Co molar ratio between 0.05 and 0.1, which showed negligible amounts of methane among the reaction products, thus offering an active and selective material for the low-temperature steam reforming of ethanol for small-scale energy applications.

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