MRI of Heterogeneous Hydrogenation Reactions Using Parahydrogen Polarization

Thesis/Dissertation · Tue Jan 01 00:00:00 EST 2008

DOI:https://doi.org/10.2172/934962· OSTI ID:934962

Burt, Scott Russell ^[1]

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1. Univ. of California, Berkeley, CA (United States)

The power of magnetic resonance imaging (MRI) is its ability to image the internal structure of optically opaque samples and provide detailed maps of a variety of important parameters, such as density, diffusion, velocity and temperature. However, one of the fundamental limitations of this technique is its inherent low sensitivity. For example, the low signal to noise ratio (SNR) is particularly problematic for imaging gases in porous materials due to the low density of the gas and the large volume occluded by the porous material. This is unfortunate, as many industrially relevant chemical reactions take place at gas-surface interfaces in porous media, such as packed catalyst beds. Because of this severe SNR problem, many techniques have been developed to directly increase the signal strength. These techniques work by manipulating the nuclear spin populations to produce polarized} (i.e., non-equilibrium) states with resulting signal strengths that are orders of magnitude larger than those available at thermal equilibrium. This dissertation is concerned with an extension of a polarization technique based on the properties of parahydrogen. Specifically, I report on the novel use of heterogeneous catalysis to produce parahydrogen induced polarization and applications of this new technique to gas phase MRI and the characterization of micro-reactors. First, I provide an overview of nuclear magnetic resonance (NMR) and how parahydrogen is used to improve the SNR of the NMR signal. I then present experimental results demonstrating that it is possible to use heterogeneous catalysis to produce parahydrogen-induced polarization. These results are extended to imaging void spaces using a parahydrogen polarized gas. In the second half of this dissertation, I demonstrate the use of parahydrogen-polarized gas-phase MRI for characterizing catalytic microreactors. Specifically, I show how the improved SNR allows one to map parameters important for characterizing the heat and mass transport in a heterogeneous catalyst bed. This is followed by appendices containing detailed information regarding the design and use of my experimental setup.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC02-05CH11231; AC05-06OR23100
• OSTI ID: 934962
• Report Number(s): LBNL-683E; TRN: US200815%%49
• Resource Relation: Related Information: Designation of Academic Dissertation: Doctoral Thesis; Academic Degree: Ph.D.; Name of Academic Institution: University of California, Berkeley; Location of Academic Institution: Berkeley
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CATALYSTS
CHEMICAL REACTIONS
DESIGN
DIFFUSION
GASES
HETEROGENEOUS CATALYSIS
HYDROGENATION
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
POLARIZATION
POROUS MATERIALS
SENSITIVITY
SIGNAL-TO-NOISE RATIO
SPIN
THERMAL EQUILIBRIUM
TRANSPORT
VELOCITY
NMR
MRI
parahydrogen
PHIP
pasadena
altadena
heterogeneous hydrogenation