Electron spin resonance spectra and catalytic activity of molybdenum oxide on various supports

1970 ◽  
Vol 74 (23) ◽  
pp. 4102-4109 ◽  
Author(s):  
Kalkunte S. Seshadri ◽  
Leonidas Petrakis
Keyword(s):  
Catalytic Activity ◽  
Electron Spin Resonance ◽  
Molybdenum Oxide ◽  
Electron Spin ◽  
Spin Resonance

scholarly journals Facile Investigation of Ti3+ State in Ti-based Ziegler-Natta Catalyst with A Combination of Cocatalysts Using Electron Spin Resonance (ESR)

2019 ◽  
Vol 15 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Thanyaporn Pongchan ◽  
Piyasan Praserthdam ◽  
Bunjerd Jongsomjit
Keyword(s):  
Catalytic Activity ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Ethylene Polymerization ◽  
Moderate Activity ◽  
Catalyst Activation ◽  
Spin Resonance ◽  
Natta Catalyst ◽  
The One ◽  
Ziegler Natta Catalyst

This study aims to investigate the influences of a combination of cocatalysts including triethylaluminum (TEA) and tri-n-octylaluminum (TnOA) for activation of a commercial Ti-based Ziegler-Natta catalyst during ethylene polymerization and ethylene/1-hexene copolymerization on the change in Ti3+ during polymerization. Thus, electron spin resonance (ESR) technique was performed to monitor the change in Ti3+ depending on the catalyst activation by a single and combination of cocatalyst. It revealed that the amount of Ti3+ played a crucial role on both ethylene polymerization and ethylene/1-hexene copolymerization. For ethylene polymerization, the activation with TEA apparently resulted in the highest catalytic activity. The activation with TEA+TnOA combination exhibited a moderate activity, whereas TnOA activation gave the lowest activity. In case of ethylene/1-hexene copolymerization, it revealed that the presence of 1-hexene decreased activity. The effect of different cocatalysts tended to be similar to the one in the absence of 1-hexene. The decrease of temperature from 80 to 70 °C in ethylene/1-hexene copolymerization tended to lower catalytic activity for TnOA and TEA+TnOA, whereas only slight effect was observed for TEA system. The effect of different cocatalyst activation on the change of Ti3+ state of catalyst was elucidated by ESR measurement. It appeared that the activation of catalyst with TEA+TnOA combination essentially inhibited the reduction of Ti3+ to Ti2+ leading to lower activity.  Furthermore, the polymer properties such as morphology and crystallinity can be altered by different cocatalysts. Copyright © 2020 BCREC Group. All rights reserved

Electron spin resonance studies of the surface chemistry of molybdenum–alumina catalysts

1978 ◽  
Vol 56 (13) ◽  
pp. 1769-1772 ◽  
Author(s):  
K. C. Khulbe ◽  
R. S. Mann ◽  
M. Ternan
Keyword(s):  
Electron Spin Resonance ◽  
Surface Chemistry ◽  
Molybdenum Oxide ◽  
Electron Spin ◽  
Oxygen Species ◽  
Heavy Oils ◽  
Strong Signal ◽  
Spin Resonance ◽  
Alumina Catalysts

When alumina was doped with molybdenum oxide, the concentration of the electron accepting sites increased linearly up to 18 wt% MoO3, and then decreased. The colour of the Mo–alumina changed from whitish yellow to grayish black when degassed at 320 °C for 2 h. This depended on the concentration of Mo. A strong signal for Mo5+ was observed. Oxygen species were formed when the degassed sample was treated with oxygen or air. A reversible behaviour of oxygen on these species was observed. A possible mechanism has been discussed for the formation of O2− species and the reversible behaviour of oxygen. The concentration of electron accepting centers has been correlated with the activity for the hydrodenitrogenation of heavy oils over MoO3–alumina catalysts.

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