Studies of Hydrogenation Catalysis Using Hyperpolarized NMR

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Material Information

Title:
Studies of Hydrogenation Catalysis Using Hyperpolarized NMR
Physical Description:
1 online resource (1 p.)
Language:
english
Creator:
Zhou, Ronghui
Publisher:
University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Chemistry
Committee Chair:
BOWERS,CLIFFORD RUSSELL
Committee Co-Chair:
MCELWEE-WHITE,LISA ANN
Committee Members:
POLFER,NICOLAS CAMILLE
MURRAY,LESLIE JUSTIN
HAGELIN,HELENA AE

Subjects

Subjects / Keywords:
altadena -- catalysis -- heterogeneous -- hydrogenation -- hyperpolarization -- isomerization -- nanoparticle -- nmr -- parahydrogen -- pasadena -- phip -- simulation -- stereoselectivity
Chemistry -- Dissertations, Academic -- UF
Genre:
Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract:
Surface processes involved in heterogeneous catalysis can be effectively studied by in-situ/operando techniques. For example, in heterogeneous hydrogenation, molecular hydrogen dissociates into atomic hydrogen upon chemisorption on metal surfaces followed by migration, spillover and even dissolution into the lattice, leading to random addition. Pairwise addition, where the two hydrogen atoms come from a single molecule and retain their nuclear spin correlations, is not typically considered as a distinct process. Nevertheless, surface reaction activities and pathways have been shown to be affected by the presence of reactants, intermediates, products and by-products such as carbonaceous deposits. Other factors affecting heterogeneous catalysis include the nature of the catalyst, such as metal type, particle size, shape, morphology, dispersion, as well as the properties of the supports, especially those with strong metal-support interactions (SMSI). Such factors are also important in determining the favorability of pairwise addition. While it would be extremely difficult to distinguish between these two pathways using conventional methods such as gas chromatography, hyperpolarized NMR based on Parahydrogen Induced Polarization (PHIP) provides a unique tool to study pairwise hydrogen addition, since only this pathway leads to dramatically enhanced (105) NMR signals. In this study, a variety of catalysts were prepared with transition metals (Pt, Ir, etc.) supported on different oxides (Al2O3, TiO2, etc.), through precipitation of metal salts onto supports from an aqueous solution by controlling solution pH followed by aging and calcination. Active surface area, dispersion and particle size of the catalysts were characterized by CO chemisorption measurements. For PHIP experiments, a home-built micro-reactor with heating unit was installed on the top of the magnet. The precise delivery of gas mixture (propylene, p-H2 and carrier gas) was facilitated with Mass Flow Controllers (MFCs). The resultant hyperpolarized propane flew down to the NMR probe for detection. Kinetic parameters, such as reaction temperature, gas composition and flow rate, were varied to optimize PHIP enhancement. Kinetic studies about reaction orders and activation energies were made possible with the dramatic signal enhancement. In addition, by comparing resultant NMR spectra from reactions with n-H2 or p-H2, contributions from pairwise addition was able to be derived.
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Ronghui Zhou.
Thesis:
Thesis (Ph.D.)--University of Florida, 2014.
Local:
Adviser: BOWERS,CLIFFORD RUSSELL.
Local:
Co-adviser: MCELWEE-WHITE,LISA ANN.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2016-05-31

Record Information

Source Institution:
UFRGP
Rights Management:
Applicable rights reserved.
Classification:
lcc - LD1780 2014
System ID:
UFE0046487:00001