Identifying and Evading Olefin Isomerization Catalyst Deactivation Pathways Resulting from Ion-Tunable Hemilability

ACS Catalysis ◽  
2020 ◽  
Vol 10 (21) ◽  
pp. 13019-13030
Author(s):  
Henry M. Dodge ◽  
Matthew R. Kita ◽  
Chun-Hsing Chen ◽  
Alexander J. M. Miller
Keyword(s):  
Catalyst Deactivation ◽  
Olefin Isomerization ◽  
Isomerization Catalyst

scholarly journals Selecting Double Bond Positions with a Single Cation- Responsive Iridium Olefin Isomerization Catalyst

2020 ◽  
Author(s):  
Andrew M. Camp ◽  
Matthew R. Kita ◽  
Thomas P. Blackburn ◽  
Henry M. Dodge ◽  
Chun-Hsing Chen ◽  
...  
Keyword(s):  
Mechanistic Model ◽  
Computational Studies ◽  
Olefin Isomerization ◽  
Positional Isomerization ◽  
Iridium Catalyst ◽  
Commodity Chemicals ◽  
Covalent Modifications ◽  
Insight Into ◽  
Selective Access ◽  
Isomerization Catalyst

<div><div><div><p>The catalytic transposition of double bonds holds promise as an ideal route to alkenes with value as fragrances, commodity chemicals, and pharmaceuticals; yet, selective access to specific isomers is a challenge, requiring independent development of different catalysts for different products. In this work, a single cation-responsive iridium catalyst is developed for the selective production of either of two different internal alkene isomers. In the absence of salts, a single positional isomerization of 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity and stereoselectivity. The same catalyst, in the presence of Na+, mediates two positional isomerizations to produce 3-alkenes. The synthesis of new iridium pincer-crown ether catalysts based on an aza-18-crown-6 ether proved instrumental in achieving cation-controlled selectivity. Experimental and computational studies guided the development of a mechanistic model that explains the observed selectivity for various functionalized 1-butenes, providing insight into strategies for catalyst development based on non-covalent modifications.</p></div></div></div>

scholarly journals Selecting Double Bond Positions with a Single Cation- Responsive Iridium Olefin Isomerization Catalyst

2020 ◽  
Author(s):  
Andrew M. Camp ◽  
Matthew R. Kita ◽  
Thomas P. Blackburn ◽  
Henry M. Dodge ◽  
Chun-Hsing Chen ◽  
...  
Keyword(s):  
Mechanistic Model ◽  
Computational Studies ◽  
Olefin Isomerization ◽  
Positional Isomerization ◽  
Iridium Catalyst ◽  
Commodity Chemicals ◽  
Covalent Modifications ◽  
Insight Into ◽  
Selective Access ◽  
Isomerization Catalyst

<div><div><div><p>The catalytic transposition of double bonds holds promise as an ideal route to alkenes with value as fragrances, commodity chemicals, and pharmaceuticals; yet, selective access to specific isomers is a challenge, requiring independent development of different catalysts for different products. In this work, a single cation-responsive iridium catalyst is developed for the selective production of either of two different internal alkene isomers. In the absence of salts, a single positional isomerization of 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity and stereoselectivity. The same catalyst, in the presence of Na+, mediates two positional isomerizations to produce 3-alkenes. The synthesis of new iridium pincer-crown ether catalysts based on an aza-18-crown-6 ether proved instrumental in achieving cation-controlled selectivity. Experimental and computational studies guided the development of a mechanistic model that explains the observed selectivity for various functionalized 1-butenes, providing insight into strategies for catalyst development based on non-covalent modifications.</p></div></div></div>

Stabilities of nickel–alkyl compounds

1970 ◽  
Vol 48 (21) ◽  
pp. 3443-3446 ◽  
Author(s):  
J. Thomson ◽  
M. C. Baird
Keyword(s):  
Thermal Decomposition ◽  
Olefin Isomerization ◽  
Xylene Solution ◽  
Isomerization Catalyst

The compounds π-C5H5Ni(PPh3)R (R = Me, Et, n-Pr, iso-Pr, n-Bu, sec-Bu, iso-Bu) have been prepared and characterized. Thermal decomposition of these compounds in xylene solution yields, in all cases except the methyl, an olefin and an olefin isomerization catalyst.

Selecting Double Bond Positions with a Single Cation-Responsive Iridium Olefin Isomerization Catalyst

2021 ◽  
Vol 143 (7) ◽  
pp. 2792-2800
Author(s):  
Andrew M. Camp ◽  
Matthew R. Kita ◽  
P. Thomas Blackburn ◽  
Henry M. Dodge ◽  
Chun-Hsing Chen ◽  
...  
Keyword(s):  
Double Bond ◽  
Olefin Isomerization ◽  
Isomerization Catalyst

What catalysis needs from the electron microscopist

1988 ◽  
Vol 46 ◽  
pp. 694-695
Author(s):  
Alexis T. Bell
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Surface Composition ◽  
Internal Surface ◽  
Active Phase ◽  
Atomic Scale ◽  
Metal Catalyst ◽  
Internal Surface Area ◽  
Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

Analytical Electron Microscopy study of two vehicle-aged automotive exhaust catalysts having dissimilar activities

1989 ◽  
Vol 47 ◽  
pp. 272-273
Author(s):  
Sooho Kim ◽  
M. J. D’Aniello
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Noble Metal ◽  
Catalyst Deactivation ◽  
Analytical Electron Microscopy ◽  
Microscopy Study ◽  
Metal Particles ◽  
Automotive Exhaust ◽  
Exhaust Catalysts ◽  
Analytical Electron

Automotive catalysts generally lose-agtivity during vehicle operation due to several well-known deactivation mechanisms. To gain a more fundamental understanding of catalyst deactivation, the microscopic details of fresh and vehicle-aged commercial pelleted automotive exhaust catalysts containing Pt, Pd and Rh were studied by employing Analytical Electron Microscopy (AEM). Two different vehicle-aged samples containing similar poison levels but having different catalytic activities (denoted better and poorer) were selected for this study.The general microstructure of the supports and the noble metal particles of the two catalysts looks similar; the noble metal particles were generally found to be spherical and often faceted. However, the average noble metal particle size on the poorer catalyst (21 nm) was larger than that on the better catalyst (16 nm). These sizes represent a significant increase over that found on the fresh catalyst (8 nm). The activity of these catalysts decreases as the observed particle size increases.

An analytical microscopic study of metals in fluidized catalytic cracking catalyst

1986 ◽  
Vol 44 ◽  
pp. 854-855
Author(s):  
Clifford S. Rainey
Keyword(s):  
Electron Microscopy ◽  
Spatial Distribution ◽  
Catalytic Cracking ◽  
Catalyst Deactivation ◽  
Coke Formation ◽  
Acid Sites ◽  
Y Zeolite ◽  
Fcc Catalyst ◽  
Fluidized Catalytic Cracking ◽  
High Regeneration

The spatial distribution of V and Ni deposited within fluidized catalytic cracking (FCC) catalyst is studied because these metals contribute to catalyst deactivation. Y zeolite in FCC microspheres are high SiO2 aluminosilicates with molecular-sized channels that contain a mixture of lanthanoids. They must withstand high regeneration temperatures and retain acid sites needed for cracking of hydrocarbons, a process essential for efficient gasoline production. Zeolite in combination with V to form vanadates, or less diffusion in the channels due to coke formation, may deactivate catalyst. Other factors such as metal "skins", microsphere sintering, and attrition may also be involved. SEM of FCC fracture surfaces, AEM of Y zeolite, and electron microscopy of this work are developed to better understand and minimize catalyst deactivation.

scholarly journals Ordered Mesoporous Carbon as a Support for Palladium-Based Hydrodechlorination Catalysts

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 23
Author(s):  
Farzeen Sakina ◽  
Carlos Fernandez-Ruiz ◽  
Jorge Bedia ◽  
Luisa Gomez-Sainero ◽  
Richard Baker
Keyword(s):  
Photoelectron Spectroscopy ◽  
Mesoporous Carbon ◽  
Catalyst Deactivation ◽  
Average Diameter ◽  
Pd Nanoparticles ◽  
Ordered Mesoporous Carbon ◽  
Catalyst Composition ◽  
Ordered Mesoporous ◽  
Higher Hydrocarbons ◽  
Carbon Catalysts

Ordered mesoporous carbon (OMC) was employed as a support for palladium nanoparticles in catalysts for the gas phase hydrodechlorination (HDC) of trichloromethane (TCM). 1 wt% palladium was incorporated using three methods: incipient wetness (IW); a dilute solution (DS) method; and a solid-liquid (SL) method. The effect of the preparation method on catalyst structure and activity was investigated. Catalyst composition and nanostructure were studied using gas physisorption, high specification transmission electron microscopy and X-ray photoelectron spectroscopy. Catalytic conversion and product selectivities were determined in steady-state activity tests at temperatures between 70 and 300 °C. Two of the catalysts (IW and DS) showed excellent dispersion of fine Pd nanoparticles of average diameter ~2 nm. These materials showed excellent activity for HDC of TCM which compares favourably with the performance reported for Pd on amorphous carbon catalysts. In addition, they showed relatively high selectivities to the more valuable higher hydrocarbons. However, the SL method gave rise to catalysts with larger particles (~3 nm) and a less uniform palladium distribution. This resulted in lower conversion and lower selectivities to higher hydrocarbons and in more severe catalyst deactivation at the highest reaction temperatures.

Catalyst deactivation during deep oxidation of chlorohydrocarbons

1992 ◽  
Vol 82 (2) ◽  
pp. 259-275 ◽  
Author(s):  
S.K. Agarwal ◽  
J.J. Spivey ◽  
J.B. Butt
Keyword(s):  
Catalyst Deactivation ◽  
Deep Oxidation
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