Pd-based bimetallic catalysts for parahydrogen-induced polarization in heterogeneous hydrogenations

Burueva, Dudari B.; Stakheev, A. Yu.; Koptyug, Igor V.

doi:10.5194/mr-2-93-2021

Cited by 7 publications

(12 citation statements)

References 62 publications

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“…Specifically, Ag5Pd0.06 with Ag being the dominating component has a remarkable signal enhancement factor of 889, about 102 times higher than that of the monometallic Pd1 catalyst (signal enhancement factor = 8.7). The higher PHIP generation efficiency of bimetallic Pd–Ag catalyst is consistent with the previous report . The higher signal enhancement factor means a higher ratio of pairwise addition in the hydrogenation process, indicating a stronger restriction of proton motion on the catalyst surface.…”

Section: Results and Discussionsupporting

confidence: 91%

“…The higher PHIP generation efficiency of bimetallic Pd−Ag catalyst is consistent with the previous report. 33 The higher signal enhancement factor means a higher ratio of pairwise addition in the hydrogenation process, indicating a stronger restriction of proton motion on the catalyst surface. The diffusion restriction of the split H atoms on the nanoparticle surface facilitates pairwise addition of the protons originated from the same parahydrogen molecule, which leads to higher signal enhancement factor.…”

Section: Density Matrix Simulationsmentioning

confidence: 99%

“…The most recent work by Koptyug and co-workers showed that the Pd−Ag bimetallic catalyst outperforms the monometallic Pd catalyst on the PHIP generation efficiency in the hydrogenation of propyne. 33 The dilution of catalytically active Pd with less active Ag atoms was found to enhance the selectivity of pairwise H 2 addition by directly comparing the Pd−Ag/Al 2 O 3 and Pd/Al 2 O 3 catalysts in propyne hydrogenation, which could be attributed to the formation of atomically dispersed Pd sites on bimetallic surface. The high hydrogenation selectivity and PHIP generation efficiency of the Pd−Ag catalyst provides an ideal model for the exploration of the structure-stereoselectivity relationship with the PHIP technique.…”

Section: Introductionmentioning

confidence: 99%

“…Parahydrogen-induced polarization (PHIP) is an efficient nuclear spin hyperpolarization method to increase the sensitivity of nuclear magnetic resonance (NMR). − PHIP uses parahydrogen (p-H 2 ) as the source of hyperpolarization and enables signal enhancement in theory by a factor of 10 4 –10 5 , which has become a powerful tool for the study of hydrogen addition process due to its unique hyperpolarization mechanism. − Typically, two atoms from the same p-H 2 molecule are added to magnetically nonequivalent positions of the same unsaturated product molecule in a pairwise manner to obtain PHIP. The added protons can be easily identified in the 1 H NMR spectrum from the signal intensity and line shape, which allows for tracing the hydrogen addition pathway.…”

Section: Introductionmentioning

confidence: 99%

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Pairwise Stereoselective Hydrogenation of Propyne on Supported Pd–Ag Catalysts Investigated by Parahydrogen-Induced Polarization

Wang¹,

Wang²,

Qi³

et al. 2021

J. Phys. Chem. C

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Alkyne semihydrogenation offers a key approach for the synthesis of stereodefined molecules. The stereoselective hydrogenation of propyne to propene over Al 2 O 3 -supported Pd−Ag bimetallic catalysts is studied by using parahydrogen-induced polarization (PHIP) NMR technique. The supported catalysts were prepared by an incipient-wetness impregnation method, and their properties were systemically tuned by altering Pd and Ag components. Structural characterization by X-ray diffraction, infrared spectra, and transmission electron microscope shows the formation of highly dispersed bimetallic Pd−Ag nanoparticles with random alloy structures on Al 2 O 3 support. For the hydrogenation of propyne over Pd−Ag catalysts with higher Ag concentration, the adsorbed protons are mostly restricted on the active Pd ensembles, which favors a higher pairwise hydrogen addition to propyne, leading to a stronger PHIP effect. The product stereoselectivity measurements show that the pairwise syn-addition to propyne increases with Ag content in the Pd−Ag alloy. The reaction conditions impact the pairwise hydrogenation stereoselectivity. A lower H 2 /propyne ratio of reactant flow or a higher total reactant flow rate enhances the apparent pairwise syn-addition stereoselectivity, which can be accounted for by the suppressed cis−trans isomerization process and/or a higher intrinsic pairwise syn-addition selectivity.

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Section: Results and Discussionsupporting

confidence: 91%

Section: Density Matrix Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Pairwise Stereoselective Hydrogenation of Propyne on Supported Pd–Ag Catalysts Investigated by Parahydrogen-Induced Polarization

Wang¹,

Wang²,

Qi³

et al. 2021

J. Phys. Chem. C

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Section: Hyperpolarization Techniquesmentioning

confidence: 99%

Spin Hyperpolarization in Modern Magnetic Resonance

et al. 2023

Self Cite

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Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity. This provides new impetus for existing applications of magnetic resonance and opens the gates to exciting new possibilities. In this review, we provide a unified picture of the many methods and techniques that fall under the umbrella term "hyperpolarization" but are currently seldom perceived as integral parts of the same field. Specifically, before delving into the individual techniques, we provide a detailed analysis of the underlying principles of spin hyperpolarization. We attempt to uncover and classify the origins of hyperpolarization, to establish its sources and the specific mechanisms that enable the flow of polarization from a source to the target spins. We then give a more detailed analysis of individual hyperpolarization techniques: the mechanisms by which they work, fundamental and technical requirements, characteristic applications, unresolved issues, and possible future directions. We are seeing a continuous growth of activity in the field of spin hyperpolarization, and we expect the field to flourish as new and improved hyperpolarization techniques are implemented. Some key areas for development are in prolonging polarization lifetimes, making hyperpolarization techniques more generally applicable to chemical/biological systems, reducing the technical and equipment requirements, and creating more efficient excitation and detection schemes. We hope this review will facilitate the sharing of knowledge between subfields within the broad topic of hyperpolarization, to help overcome existing challenges in magnetic resonance and enable novel applications.

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Nanomaterials for hyperpolarized nuclear magnetic resonance and magnetic resonance imaging

Saul

Schröder

Schmidt

et al. 2023

WIREs Nanomed Nanobiotechnol

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Nanomaterials play an important role in the development and application of hyperpolarized materials for magnetic resonance imaging (MRI). In this context they can not only act as hyperpolarized materials which are directly imaged but also play a role as carriers for hyperpolarized gases and catalysts for para-hydrogen induced polarization (PHIP) to generate hyperpolarized substrates for metabolic imaging. Those three application possibilities are discussed, focusing on carbon-based materials for the directly imaged particles.An overview over recent developments in all three fields is given, including the early developments in each field as well as important steps towards applications in MRI, such as making the initially developed methods more biocompatible and first imaging experiments with spatial resolution in either phantoms or in vivo studies. Focusing on the important features nanomaterials need to display to be applicable in the MRI context, a wide range of different approaches to that extent is covered, giving the reader a general idea of different possibilities as well as recent developments in those different fields of hyperpolarized magnetic resonance.

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Pd-based bimetallic catalysts for parahydrogen-induced polarization in heterogeneous hydrogenations

Cited by 7 publications

References 62 publications

Pairwise Stereoselective Hydrogenation of Propyne on Supported Pd–Ag Catalysts Investigated by Parahydrogen-Induced Polarization

Pairwise Stereoselective Hydrogenation of Propyne on Supported Pd–Ag Catalysts Investigated by Parahydrogen-Induced Polarization

Spin Hyperpolarization in Modern Magnetic Resonance

Nanomaterials for hyperpolarized nuclear magnetic resonance and magnetic resonance imaging

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