Quantifying the fraction and activity of catalytic sites at different surface densities of aminosilanes in SBA-15 for the aldol reaction and condensation

Chen, Jee-Yee; Pineault, Hannah; Brunelli, Nicholas A.

doi:10.1016/j.jcat.2022.08.015

Cited by 6 publications

(2 citation statements)

References 42 publications

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“…As the pyrrolidine active sites are immobilized by partial substitution of hydroxyl groups, the number of promoting hydroxyl groups per active site decreases with increasing loading. Typically, it can be expected that if the ratio of promoting groups per active site becomes too low, insufficient promotion is provided, which negatively affects the catalytic activity [13,41]. However, here, similar activities were obtained for both low-and high-loaded materials, which implies that within the investigated range, the amine active sites are sufficiently promoted by the hydroxyl groups and, hence, loading effects can be excluded.…”

Section: Catalyst Performance Assessmentsupporting

confidence: 53%

A Pyrrolidine Functionalized Poly[(ethylene glycol) Methacrylate] Resin as a Heterogeneous Catalyst for Aqueous Aldol Reactions

et al. 2022

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The development of a performant aminated catalyst for aldol condensations requires the combined tuning of the active site, support and solvent system. For this purpose, a pyrrolidine group was immobilized on a swellable polymer resin. Favorable interactions between the support and water (in its role as solvent) resulted in a turnover frequency (TOF) amounting to 3.0 ± 1.5·10−3 s−1, despite potential inhibition of the active sites by formation of iminium species. The affinity of the solvent for the poly[(ethylene glycol) methacrylate] support resulted in efficient swelling of the catalytic material, which was shown to be key to the observed catalytic performance.

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Section: Catalyst Performance Assessmentsupporting

confidence: 53%

A Pyrrolidine Functionalized Poly[(ethylene glycol) Methacrylate] Resin as a Heterogeneous Catalyst for Aqueous Aldol Reactions

et al. 2022

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“…Site quantification experiments have been applied to zeolite Beta, ,, other zeolite frameworks, and mesoporous catalysts such as amine-functionalized SBA-15. − For Sn-Beta, Harris et al used pyridine for titration experiments and complemented these results with FTIR using acetonitrile to identify open defect sites as the dominant sites for glucose isomerization, corroborating earlier findings. , Bates et al later expanded upon this work and determined that closed Sn sites were more active than open defect Sn sites for ethanol dehydration using similar techniques …”

Section: Introductionmentioning

confidence: 73%

Counting Sites in Lewis Acid Zeolite Sn-Beta: Connecting Site Quantification Experiments and Spectroscopy To Investigate the Catalytic Activity for the Alcohol Ring Opening of Epoxides

2023

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Sn-Beta is a promising catalyst for numerous reactions involved in biomass upgrading and fine chemical production, but it is complex with multiple types of active sites. The activity for Sn-Beta can be calculated on a per-site basis using site quantification experiments that involve adding a Lewis basic probe molecule, but it is not clear which types of sites are being titrated. Our work connects site quantification experiments with spectroscopic measurements to explain differences in the catalytic activity of materials crystallized for different amounts of time. For alcohol ring opening of epoxides, experiments reveal that Sn-Beta crystallized for 10 days (Sn-Beta-200-10d) is more active than Sn-Beta crystallized for 40 days (Sn-Beta-200-40d). These materials are investigated using site quantification experiments with three probestriethylamine, pyridine, or 2,6-lutidineto reveal the different fractions and types of sites. As the probe:Sn ratio is increased, these experiments result in two distinct slopes, indicating two distinct activities: high and low activity. The difference in activity between Sn-Beta-200-10d and Sn-Beta-200-40d can be attributed to the reduced fraction of high-activity sites. Although the two slopes have typically been assigned to open defect Sn sites for high activity and closed Sn sites for low activity, 15N NMR measurements of materials dosed with 15N-labeled pyridine contradict this assignment. Indeed, at low concentrations, pyridine adsorbs on both open defect and closed Sn sites whereas the low activity corresponds to pyridine binding to SnOH groups in addition to closed Sn sites. Overall, the identification of appropriate site quantification experiment parameters and the combination of these titrations with NMR techniques allows for the establishment of a synthesis–structure–activity relationship that has the potential to improve the performance of Sn-Beta.

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Evaluating the per site activity of common mesoporous materials as supports for aminosilica catalysts for the aldol reaction and condensation

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Chen

Pineault

et al. 2023

Applied Catalysis A: General

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Quantifying the fraction and activity of catalytic sites at different surface densities of aminosilanes in SBA-15 for the aldol reaction and condensation

Cited by 6 publications

References 42 publications

A Pyrrolidine Functionalized Poly[(ethylene glycol) Methacrylate] Resin as a Heterogeneous Catalyst for Aqueous Aldol Reactions

A Pyrrolidine Functionalized Poly[(ethylene glycol) Methacrylate] Resin as a Heterogeneous Catalyst for Aqueous Aldol Reactions

Counting Sites in Lewis Acid Zeolite Sn-Beta: Connecting Site Quantification Experiments and Spectroscopy To Investigate the Catalytic Activity for the Alcohol Ring Opening of Epoxides

Evaluating the per site activity of common mesoporous materials as supports for aminosilica catalysts for the aldol reaction and condensation

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