ChemInform Abstract: NMR STUDIES OF PYRIDINE ON SILICA‐ALUMINA

Maciel, Gary E.; Haw, James F.; Chuang, I. Ssuer; Hawkins, Bill C.; Early, Thomas A.; McKay, Dale R.; Petrakis, L.

doi:10.1002/chin.198348042

Cited by 2 publications

(2 citation statements)

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“…Brønsted acid sites by using IR or solid-state NMR spectroscopy. Recent studies have shown that 15 N MAS NMR, [23][24][25] in particular when combined with DNP-enhanced NMR techniques, [26] is particularly powerful by enabling to readily distinguish between Py bound to Lewis and Brønsted sites with different strength, [25] as well as H-bonded Py [26]. Pyridine is also a typical ligand in coordination chemistry and has been used to tame (passivate) the reactivity of metal sites.…”

Section: Pyridine (Py) Is a Classical Surface Probe That Allows Intermentioning

confidence: 99%

A Formulation Protocol with Pyridine to Enable DNP-SENS on Reactive Surface Sites: Case Study with Olefin Polymerization and Metathesis Catalysts

Yakimov¹,

Mance²,

Searles³

et al. 2020

Preprint

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<div>Dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP-SENS) has emerged as a powerful characterization tool in material chemistry and heterogeneous catalysis by dramatically increasing, by up to two orders of magnitude, the NMR signals associated with surface sites. DNP-SENS mostly relies on using exogenous polarizing agents (PAs) – typically di-nitroxyl radicals, to boost the NMR signals, that may interact with the surface or even react with highly reactive surface sites, thus leading to loss/quenching of DNP enhancements. Herein, we describe the development of a DNP-SENS formulation that allows us to broaden the application of DNP-SENS to samples containing highly reactive surface sites, namely a Ziegler-Natta propylene polymerization catalyst, a sulfated zirconia-supported metallocene and a silica-supported cationic Mo alkylidene. The protocol consists of adsorbing pyridine prior to the impregnation of the DNP formulation (TEKPol/TCE). The addition of pyridine does not only preserve the PAs and thereby restore the DNP enhancement, but it also allows probing the presence of Lewis acid and Brønsted acid surface sites that are often present on these catalysts.</div>

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Section: Pyridine (Py) Is a Classical Surface Probe That Allows Intermentioning

confidence: 99%

A Formulation Protocol with Pyridine to Enable DNP-SENS on Reactive Surface Sites: Case Study with Olefin Polymerization and Metathesis Catalysts

Yakimov¹,

Mance²,

Searles³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…Pyridine (Py) is a classical surface probe that allows interrogating the presence of Lewis and Brønsted acid sites by using IR or solid-state NMR spectroscopy. Recent studies have shown that 15 N MAS NMR, [23][24][25] in particular when combined with DNP-enhanced NMR techniques, [26] is particularly powerful by enabling to readily distinguish between Py bound to Lewis and Brønsted sites with different strength, [25] as well as H-bonded Py [26]. Pyridine is also a typical ligand in coordination chemistry and has been used to tame (passivate) the reactivity of metal sites.…”

mentioning

confidence: 99%