Half-Metallocene Titanium(IV) Phenyl Phenoxide for High Temperature Olefin Polymerization: Ortho-Substituent Effect at Ancillaryo-Phenoxy Ligand for Enhanced Catalytic Performance

2009 ◽  
Vol 42 (18) ◽  
pp. 6932-6943 ◽  
Author(s):  
Tae-Jin Kim ◽  
Sung-Kwan Kim ◽  
Beom-Jun Kim ◽  
Jong Sok Hahn ◽  
Myung-Ahn Ok ◽  
...  
Keyword(s):  
High Temperature ◽  
Substituent Effect ◽  
Olefin Polymerization ◽  
Catalytic Performance ◽  
Ortho Substituent

Structural/Texture Evolution During Facile Substitution of Ni into ZSM-5 Nanostructure vs. its Impregnation Dispersion Used in Selective Transformation of Methanol to Ethylene and Propylene

2020 ◽  
Vol 23 ◽  
Author(s):  
Parisa Sadeghpour ◽  
Mohammad Haghighi ◽  
Mehrdad Esmaeili
Keyword(s):  
High Temperature ◽  
Physicochemical Properties ◽  
Active Sites ◽  
Catalytic Performance ◽  
Fixed Bed Reactor ◽  
Light Olefins ◽  
Isomorphous Substitution ◽  
Impregnation Method ◽  
Hydrothermal Temperature ◽  
X Ray

Aim and Objective: Effect of two different modification methods for introducing Ni into ZSM-5 framework was investigated under high temperature synthesis conditions. The nickel successfully introduced into the MFI structures at different crystallization conditions to enhance the physicochemical properties and catalytic performance. Materials and Methods: A series of impregnated Ni/ZSM-5 and isomorphous substituted NiZSM-5 nanostructure catalysts were prepared hydrothermally at different high temperatures and within short times. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDX), Brunner, Emmett and Teller-Barrett, Joyner and Halenda (BET-BJH), Fourier transform infrared (FTIR) and Temperature-programmed desorption of ammonia (TPDNH3) were applied to investigate the physicochemical properties. Results: Although all the catalysts showed pure silica MFI–type nanosheets and coffin-like morphology, using the isomorphous substitution for Ni incorporation into the ZSM-5 framework led to the formation of materials with lower crystallinity, higher pore volume and stronger acidity compared to using impregnation method. Moreover, it was found that raising the hydrothermal temperature increased the crystallinity and enhanced more uniform incorporation of Ni atoms in the crystalline structure of catalysts. TPD-NH3 analysis demonstrated that high crystallization temperature and short crystallization time of NiZSM-5(350-0.5) resulted in fewer weak acid sites and medium acid strength. The MTO catalytic performance was tested in a fixed bed reactor at 460ºC and GHSV=10500 cm3 /gcat.h. A slightly different reaction pathway was proposed for the production of light olefins over impregnated Ni/ZSM-5 catalysts based on the role of NiO species. The enhanced methanol conversion for isomorphous substituted NiZSM-5 catalysts could be related to the most accessible active sites located inside the pores. Conclusion: The impregnated Ni/ZSM-5 catalyst prepared at low hydrothermal temperature showed the best catalytic performance, while the isomorphous substituted NiZSM-5 prepared at high temperature was found to be the active molecular sieve regarding the stability performance.

On Conformational Flexibility of Half-Titanocene Catalysts with Aryloxy Ligands for High-Temperature Olefin Polymerization Processes: Static and Dynamic Theoretical Studies†

2010 ◽  
Vol 29 (21) ◽  
pp. 5341-5352 ◽  
Author(s):  
Monika Srebro ◽  
Łukasz Piȩkoś ◽  
Tae-Jin Kim ◽  
Minserk Cheong ◽  
Myung-Ahn Ok ◽  
...  
Keyword(s):  
High Temperature ◽  
Olefin Polymerization ◽  
Conformational Flexibility ◽  
Theoretical Studies

scholarly journals Prediction of ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous acetonitrile

2013 ◽  
Vol 11 (12) ◽  
pp. 1964-1975 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Ilmar Koppel
Keyword(s):  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Benzoic Acids ◽  
Aqueous Acetonitrile ◽  
Substituent Constants ◽  
Substituted Benzoic Acids ◽  
Hydrolysis Of ◽  
Ortho Substituent

AbstractThe second-order rate constants k for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, in aqueous 50.9% acetonitrile have been measured spectrophotometrically at 25°C. The log k values for meta and para derivatives correlated well with the Hammett σm,p substituent constants. The log k values for ortho-substituted phenyl benzoates showed good correlations with the Charton equation, containing the inductive, σI, resonance, σ○ R, and steric, E s B, and Charton υ substituent constants. For ortho derivatives the predicted (log k X)calc values were calculated with equation (log k ortho)calc = (log k H AN)exp + 0.059 + 2.19σI + 0.304σ○ R + 2.79E s B − 0.0164ΔEσI — 0.0854ΔEσ○ R, where DE is the solvent electrophilicity, ΔE = E AN — E H20 = −5.84 for aqueous 50.9% acetonitrile. The predicted (log k X)calc values for phenyl ortho-, meta- and para-substituted benzoates in aqueous 50.9% acetonitrile at 25°C precisely coincided with the experimental log k values determined in the present work.The substituent effects from the benzoyl moiety and aryl moiety were compared by correlating the log k values for the alkaline hydrolysis of phenyl esters of substituted benzoic acids, X-C6H4CO2C6H5, in various media with the corresponding log k values for substituted phenyl benzoates, C6H5CO2C6H4-X.

Enhancing the catalytic performance of cobalt oxide by doping on ceria in the high temperature water–gas shift reaction

RSC Advances ◽  
2015 ◽  
Vol 5 (125) ◽  
pp. 103023-103029 ◽  
Author(s):  
Ajay Jha ◽  
Dae-Woon Jeong ◽  
Yeol-Lim Lee ◽  
In Wook Nah ◽  
Hyun-Seog Roh
Keyword(s):  
High Temperature ◽  
Catalytic Performance ◽  
Water Gas Shift ◽  
Precipitation Method ◽  
High Temperature Water ◽  
Wgs Reaction ◽  
Co Precipitation ◽  
Shift Reaction ◽  
Water Gas ◽  
Temperature Water

The high temperature water–gas shift (HT-WGS) reaction was performed using a Co–CeO2 catalyst, prepared through a co-precipitation method.

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