scholarly journals Physicochemical surface-structure studies of highly active zirconocene polymerisation catalysts on solid polymethylaluminoxane activating supports

2020 ◽  
Vol 4 (11) ◽  
pp. 3226-3233
Author(s):  
Alexander F. R. Kilpatrick ◽  
Nicholas H. Rees ◽  
Zoë R. Turner ◽  
Jean-Charles Buffet ◽  
Dermot O’Hare
Keyword(s):  
Surface Structure ◽  
Supported Catalyst ◽  
Drift Spectroscopy ◽  
Highly Active ◽  
Catalyst Systems

Static 91Zr ssNMR, SEM-EDX, and DRIFT spectroscopy indicate that a common zirconium species, [CpR2ZrMe]+, is present in all sMAO supported catalyst systems.

scholarly journals Highly Active Catalysts Based on the Rh4(CO)12 Cluster Supported on Ce0.5Zr0.5 and Zr Oxides for Low-Temperature Methane Steam Reforming

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 800 ◽  
Author(s):  
Andrea Fasolini ◽  
Silvia Ruggieri ◽  
Cristina Femoni ◽  
Francesco Basile
Keyword(s):  
Low Temperature ◽  
Steam Reforming ◽  
Supported Catalysts ◽  
Supported Catalyst ◽  
Methane Steam Reforming ◽  
Small Scale ◽  
Methane Reforming ◽  
Hydrogen Purification ◽  
Highly Active ◽  
Reforming Reactions

Syngas and Hydrogen productions from methane are industrially carried out at high temperatures (900 °C). Nevertheless, low-temperature steam reforming can be an alternative for small-scale plants. In these conditions, the process can also be coupled with systems that increase the overall efficiency such as hydrogen purification with membranes, microreactors or enhanced reforming with CO2 capture. However, at low temperature, in order to get conversion values close to the equilibrium ones, very active catalysts are needed. For this purpose, the Rh4(CO)12 cluster was synthetized and deposited over Ce0.5Zr0.5O2 and ZrO2 supports, prepared by microemulsion, and tested in low-temperature steam methane reforming reactions under different conditions. The catalysts were active at 750 °C at low Rh loadings (0.05%) and outperformed an analogous Rh-impregnated catalyst. At higher Rh concentrations (0.6%), the Rh cluster deposited on Ce0.5Zr0.5 oxide reached conversions close to the equilibrium values and good stability over long reaction time, demonstrating that active phases derived from Rh carbonyl clusters can be used to catalyze steam reforming reactions. Conversely, the same catalyst suffered from a fast deactivation at 500 °C, likely related to the oxidation of the Rh phase due to the oxygen-mobility properties of Ce. Indeed, at 500 °C the Rh-based ZrO2-supported catalyst was able to provide stable results with higher conversions. The effects of different pretreatments were also investigated: at 500 °C, the catalysts subjected to thermal treatment, both under N2 and H2, proved to be more active than those without the H2 treatment. In general, this work highlights the possibility of using Rh carbonyl-cluster-derived supported catalysts in methane reforming reactions and, at low temperature, it showed deactivation phenomena related to the presence of reducible supports.

Tuning the Potential Energy Landscape to Suppress Ostwald Ripening in Surface-Supported Catalyst Systems

Nano Letters ◽  
2019 ◽  
Vol 19 (12) ◽  
pp. 8388-8398 ◽  
Author(s):  
Huashan Li ◽  
Steven C. Hayden ◽  
Arthur France-Lanord ◽  
Elisha Converse ◽  
Brian S. Hanna ◽  
...  
Keyword(s):  
Potential Energy ◽  
Ostwald Ripening ◽  
Energy Landscape ◽  
Supported Catalyst ◽  
Potential Energy Landscape ◽  
Catalyst Systems

scholarly journals Gas-Phase Epoxidation of Propylene to Propylene Oxide on a Supported Catalyst Modified with Various Dopants

Catalysts ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 638 ◽  
Author(s):  
Sugiyama ◽  
Sakuwa ◽  
Ogino ◽  
Sakamoto ◽  
Shimoda ◽  
...  
Keyword(s):  
Gas Phase ◽  
Propylene Oxide ◽  
Active Catalyst ◽  
Supported Catalyst ◽  
Acid Base ◽  
Epoxidation Of Propylene ◽  
Highly Active ◽  
Acidic Catalysts ◽  
Carbonate Species ◽  
Metal Doped

In the present study, the production of propylene oxide (PO) from propylene via gas-phase epoxidation was investigated using various catalysts. Although Ag is known to be a highly active catalyst for the epoxidation of ethylene, it was not active in the present reaction. Both Al and Ti showed high levels of activity, however, which resulted in confusion. The present study was conducted to solve such confusion. Although the employment of MCM-41 modified with Ti and/or Al was reported as an active catalyst for epoxidation, the combination resulted in the formation of PO at a less than 0.1% yield. Since this research revealed that the acidic catalyst seemed favorable for the formation of PO, versions of ZSM-5 that were both undoped and doped with Na, Ti, and Ag were used as catalysts. In these cases, small improvements of 0.67% and 0.57% were achieved in the PO yield on H‒ZSM-5 and Ti‒ZSM-5, respectively. Based on the results of the Ti-dopant and acidic catalysts, Ag metal doped on carbonate species with a smaller surface area was used as a catalyst. As reported, Ag‒Na/CaCO3 showed a greater yield of PO at 1.29%. Furthermore, the use of SrCO3 for CaCO3 resulted in a further improvement in the PO yield to 2.17%. An experiment using CO2 and NH3 pulse together with SEM and TEM examinations for Ag‒Na/CaCO3 revealed that the greatest activity was the result of the greater particle size of metallic Ag rather than the acid‒base properties of the catalysts.

Highly active copper catalyst obtained through rapid MOF decomposition

2019 ◽  
Vol 6 (2) ◽  
pp. 521-526 ◽  
Author(s):  
Anh H. T. Nguyen-Sorenson ◽  
Clifton M. Anderson ◽  
Santosh K. Balijepalli ◽  
Kyle A. McDonald ◽  
Adam J. Matzger ◽  
...  
Keyword(s):  
Copper Catalyst ◽  
Metal Organic Framework ◽  
Supported Catalyst ◽  
Highly Active ◽  
Reactive Carbon ◽  
Metal Organic ◽  
Organic Framework

A decomposed copper based metal–organic framework containing amorphous Cu species was found to be a highly reactive carbon supported catalyst (a-Cu@C).

Automated linescan analysis in the electron microprobe

1994 ◽  
Vol 52 ◽  
pp. 422-423
Author(s):  
G. E. Spinnler ◽  
D. Christenson ◽  
C. H. Nielsen
Keyword(s):  
Electron Microprobe ◽  
Supported Catalyst ◽  
Elemental Distribution ◽  
Analytical Functions ◽  
Catalyst Pellet ◽  
Distribution Of Elements ◽  
Special Software ◽  
Catalyst Pellets ◽  
And Performance ◽  
Catalyst Systems

Elemental linescan analysis in the electron microprobe (EMPA) or the SEM is useful for determining athe spatial distribution of elements. In many supported catalyst systems, the elemental distribution in pellets is important for their manufacture and performance. More important than determining the distribution of an individual pellet, is determining the distribution of many pellets in a sample to represent the lot. For this reason, multiple pellets must be analyzed. Various manufactures have systems that provide various degrees of automation for this type of analysis, however, there are no systems that allow complete unattended operation necessary to collect data on many samples.The hardware consists of a JEOL JXM 8600 with four wavelength spectrometers, an EDX detector and a NORAN Voyager. Special software was written to completely automate the linescan procedure from finding the catalyst pellet to printing the report. This software combines the imaging and other analytical functions of the Voyager with a search and identify routine that locates the catalyst pellets and determines the positions of the linescan in accordance with predetermined criteria.

Highly Active Surface Structure in Nanosized Spinel Cobalt-Based Oxides for Electrocatalytic Water Splitting

2018 ◽  
Vol 122 (26) ◽  
pp. 14447-14458 ◽  
Author(s):  
Jing Zhou ◽  
Jiong Li ◽  
Linjuan Zhang ◽  
Sanzhao Song ◽  
Yu Wang ◽  
...  
Keyword(s):  
Surface Structure ◽  
Water Splitting ◽  
Active Surface ◽  
Highly Active
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