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Full-Text Articles in Physical Sciences and Mathematics
Modification Of Active Sites In Catalytic Materials For Gas-Phase Heterogeneous Catalysis, Deependra Man Shakya
Modification Of Active Sites In Catalytic Materials For Gas-Phase Heterogeneous Catalysis, Deependra Man Shakya
Theses and Dissertations
Heterogeneous catalysis remains at the core of chemical manufacturing industries with 80-90 % of chemical processes relying on the use of catalysts. Unlike homogeneous catalyst that has extremely well-defined active sites, active sites in heterogeneous catalysis are complex and show dynamic behavior under reaction conditions, and change their structures, composition, particle size. The complexity associated with these systems has made the rational design of the catalyst a difficult problem. Highly crystalline metalorganic frameworks (MOFs) as heterogeneous catalysts present the unique opportunity to systematically modify the geometries, ensemble sizes, and compositions of highly dispersed active sites due to their tailorable, and …
Cationic Cobalt (Ii) Hydroformylation, Drew Michael Hood
Cationic Cobalt (Ii) Hydroformylation, Drew Michael Hood
LSU Doctoral Dissertations
While investigating a bimetallic cobalt hydroformylation catalyst a new class of monometallic cationic cobalt (II) hydroformylation catalyst were discovered. These newly discovered catalyst proved to be very unique with high hydroformylation activity under mild conditions. The pre-catalyst were characterized using various methods including NMR, EPR, MS, and X-ray crystallography. Similarly the active catalyst was also investigated using NMR, EPR, FTIR, and X-ray crystallography. Various catalyst modifications were investigated for their effects on hydroformylation activity. Likewise various reaction parameters were probed to determine their effect on hydroformylation activity. Finally the best cationic cobalt (II) catalyst were directly compared to industry standards …
Investigating Cationic Metal Centers For Hydroformylation, Ryan Alexander Johnson
Investigating Cationic Metal Centers For Hydroformylation, Ryan Alexander Johnson
LSU Doctoral Dissertations
Bimetallic cooperativity can potentially increase activity of reactions. This concept is another way to increase reactivity besides simply focusing on the steric and electronic effects of a ligand. A binucleating tetrasphosphine ligand has been developed to showcase bimetallic cooperativity between two rhodium metal centers. Hydroformylation is a widely used industrial process to produce aldehydes from alkenes, H2, and CO. The dirhodium catalyst, [Rh2(μ-CO)(CO)3(rac-et,ph-P4-Ph)](BF4)2,is highly active leading to favorable results when using a DMF/water solvent system, 1-hexene, 90 psi 1:1 H2/CO, and 90° C: initial turnover frequency …
Development Of New Useful Methods For Aldehyde Synthesis And Its Application In Synthesis, He Huang
Development Of New Useful Methods For Aldehyde Synthesis And Its Application In Synthesis, He Huang
Chemistry and Chemical Biology ETDs
Development of sustainable synthetic technologies for molecular construction is an important but formidably challenging task in modern organic synthesis. Aldehyde synthesis represents a long-standing interest in synthesis because of the synthetic utility. Classic methods for aldehyde synthesis have the drawbacks of the use of harsh reaction conditions, poor atom-economy and multi-step operation, and production of stoichiometric amount of chemical wastes. The state-of-the-art strategies employ transition metal complexes as catalysts to promote formylation reactions. The concerns of catalyst cost, operation complexity and poor functional group tolerance demands more efficient synthetic technologies. My Ph.D. study focuses on design of conceptually novel catalytic …
Computational Studies On Bimetallic Catalysis And X-Ray Absorption Spectroscopy, Sayakkarage R. G. Fernando
Computational Studies On Bimetallic Catalysis And X-Ray Absorption Spectroscopy, Sayakkarage R. G. Fernando
LSU Doctoral Dissertations
Computational studies are very important to gain an insight into reaction mechanisms and in interpreting and understanding complicated experimental observations. This report contains a discussion on computational studies performed on bimetallic catalysis and on X-ray absorption spectroscopy of insulators. The viability of a bimetallic rhodium and cobalt catalysts for industrially important hydroformylation and aldehyde-water shift catalysis (AWS) is discussed. Density functional theory (DFT) studies were used for bimetallic catalysis and time-dependent DFT studies were used for excited state dynamics. These studies were performed using Gaussian 09 package and NWChem. Hydroformylation is experimentally performed in acetone and 30% water/acetone systems and …
Toward The Advancement Of Tetraphosphine Ligand Synthesis For Homogeneous Bimetallic Catalysis, Marc Anthony Peterson
Toward The Advancement Of Tetraphosphine Ligand Synthesis For Homogeneous Bimetallic Catalysis, Marc Anthony Peterson
LSU Doctoral Dissertations
A tetraphosphine ligand rac-et,ph-P4 (Et2PCH2CH2(Ph)PCH2P(Ph)CH2CH2PEt2) is used for the formation of a highly active and regioselective bimetallic hydroformylation catalyst. The proposed active catalytic species in acetone, [Rh2H2(µ-CO)2(rac-et,ph- P4)]2+, is formed in situ under H2/CO pressure. This is one of the most impressive examples of cooperativity in homogeneous catalysis. The fragmentation of this catalyst by CO has been investigated and confirmed by in situ NMR spectroscopic studies. A new tetraphosphine ligand rac-et,ph-P4-Ph (et,ph-P4-Ph = Et2P(o-C6H4)P(Ph)CH2(Ph)P(o-C6H4)PEt2) has been synthesized to combat this fragmentation problem. However, the inability to successfully separate the meso and racemic diastereomers led to the attempted alteration of the …
Studies On A Dirhodium Tetraphosphine Hydroformylation Catalyst, Darina Polakova
Studies On A Dirhodium Tetraphosphine Hydroformylation Catalyst, Darina Polakova
LSU Doctoral Dissertations
The dirhodium tetraphosphine catalyst [Rh2(nbd)2(rac-et,ph-P4)](BF4)2 was investigated in acetone and water/acetone in order to explain better hydroformylation results in the latter solvent. In-situ NMR spectroscopy showed slower degradation in water/acetone. Less tendency to form penta/hexacarbonyl complexes in water/acetone was shown by 31P{1H} NMR and FT-IR. A pH decrease and hydroformylation studies in presence of a base indicated formation of a monocationic monohydride species. A new reaction mechanism was suggested that takes into account the observed differences from the acetone solvent system. The presence of water enabled production of hydride species when the dirhodium catalyst was exposed to CO gas. We …
Studies Of A Dirhodium Tetraphosphine Catalyst For Hydroformylation And Aldehyde-Water Shift Catalysis, Aaron Rider Barnum
Studies Of A Dirhodium Tetraphosphine Catalyst For Hydroformylation And Aldehyde-Water Shift Catalysis, Aaron Rider Barnum
LSU Doctoral Dissertations
Research into the dirhodium tetraphosphine catalyst precursor [rac-Rh2(nbd)2(et,ph-P4)](BF4)2 shows it is capable of forming a highly active and regioselective hydroformylation catalyst in situ when using an acetone or acetone/water solvent. Hydroformylation experiments (using 1-hexene), FT-IR studies, and acid-base studies were performed to better understand the various complexes of the dirhodium catalyst cycle. These studies lead to the newly proposed catalyst mechanism when performed in an acetone/water solution, using the monocationic [rac-Rh2(H)(µ-CO)2(CO) (et,ph-P4)]+ as the proposed active catalyst complex for hydroformylation. For the conversion of 1-hexene to heptanal, it is capable of performing an initial rate of 30 turnovers per min, …
Synthesis Of Aza-Bridged Tetraphosphine Ligands For A Dirhodium Hydroformylation Catalyst, Scott Michael Boudreaux
Synthesis Of Aza-Bridged Tetraphosphine Ligands For A Dirhodium Hydroformylation Catalyst, Scott Michael Boudreaux
LSU Master's Theses
A novel tetraphosphine ligand rac-et,ph-P4 (et,ph-P4 = PEt2CH2CH2(Ph)PCH2P(Ph)CH2CH2PEt2) is used for the formation of a highly active and regioselective hydroformylation catalyst. The active catalytic species, Rh2H2(ƒÝ-CO)2(et,ph-P4)]2+, is formed in situ under H2/CO pressure. This is one of the most impressive examples of homobimetallic cooperativity in homogeneous catalysis. The fragmentation of this catalyst by CO has been investigated and confirmed by in situ NMR spectroscopic studies. A new tetraphosphine ligand rac-et,ph-P4-Ph (et,ph-P4-Ph = PEt2(o-C6H4)P(Ph)CH2(Ph)P(o-C6H4)PEt2) has been synthesized to combat this fragmentation problem. However, the inability to successfully separate the meso and racemic isomers of the ligand has led to more alteration …
Separation And In Situ Catalytic Testing Of A Dirhodium Tetraphosphine Catalyst, Bobby Lloyd Barker
Separation And In Situ Catalytic Testing Of A Dirhodium Tetraphosphine Catalyst, Bobby Lloyd Barker
LSU Doctoral Dissertations
Attempts to study the asymmetric hydroformylation abilities of [rac-Rh2(nbd)2(et,ph-P4)](BF4)2 were made through the separation of the enantiomers of et,ph-P4 using a chiral HPLC column. Efforts were also made to optimize the NiCl2 separation chemistry for the methyl analogue of et,ph-P4 for use in asymmetric hydroformylation. A study of hydroformylation of olefins using [rac-Rh2(nbd)2(et,ph-P4)](BF4)2 in ionic liquids was also performed, leading directly to the important (and unexpected) effect of increased hydrogen pressure on [rac-Rh2(nbd)2(et,ph-P4)](BF4)2 in the acetone/water system to …
Synthesis, Separation And Reactivities Of Multidentate Phosphine Ligands And Investigation Into Dirhodium Hydroformylation And Hydrocarboxylation Catalysis, David Aubry
LSU Doctoral Dissertations
A dirhodium homogeneous hydroformylation catalyst based on a tetraphosphine ligand, rac-Et2PCH2CH2P(Ph)CH2P(Ph)CH2CH2PEt2, rac-et,ph-P4, is under investigation. The ligand synthesis produces a racemic mixture and a facile and efficient method of separation of the racemic and meso diastereomers was achieved through reaction of et,ph-P4 with two equivalents of NiCl2 in EtOH to yield an almost quantitatively isolable precipitate of meso-Ni2Cl4(et,ph-P4) and the soluble rac-Ni2Cl4(et,ph-P4). Subsequent cyanolysis of these complexes liberates the et,ph-P4 ligand, and the …