resumo
This study examines the differences in using two primary methods for adsorbing trimethylphosphine oxide (TMPO) onto acid catalysts and their influence on the NMR spectra of TMPO-loaded zeolites. The findings show that TMPO molecules interact with both Bronsted and Lewis acid sites, and that the amount of (TMPO)2H+ dimers formed increases with the amount of TMPO added. The use of dichloromethane as a solvent inhibits the formation of dimers and crystalline TMPO but may lead to inaccurate estimations of acid site strength and quantification due to interactions with residual solvent molecules. The gas-phase method is preferred for adsorbing TMPO onto zeolites, but caution is needed to avoid forming a high number of dimers that ca pose challenges in the interpretation of the NMR spectra.
palavras-chave
P-31 NMR; CHEMICAL-SHIFT; QUANTIFICATION; SPECTROSCOPY; MOLECULES; CATALYSTS; STRENGTH; PROTONS
categoria
Chemistry; Science & Technology - Other Topics; Materials Science
autores
Bornes, C; Geraldes, CFGC; Rocha, J; Mafra, L
nossos autores
Carlos Bornes
Estudante de doutoramento
João Rocha
Prof. Catedrático
Luís Mafra
Investigador PrincipalProjectos
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
agradecimentos
C. Bornes acknowledges FCT for Doctoral Fellowship PD/BD/142849/2018 integrated in the Ph.D. programme in NMR applied to chemistry, materials, and biosciences (Grant PD/00065/2013) . This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, Grants UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC). We acknowledge ALPACA for the computing resources provided. The NMR spectrometers are part of the National NMR Network (PT NMR) and are partially supported by Infrastructure Project No. 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC) . CFGCG thanks the FCT for funding the Coimbra Chemistry Centre through the programmes UIDB/00313/2020 and UIDP/00313/2020, also co-founded by FEDER/COMPETE 2020-EU. This work has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant Agreement 865974).