Solvent-free ketalization of polyols over germanosilicate zeolites: The role of the nature and strength of acid sites

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F20%3A10424022" target="_blank" >RIV/00216208:11310/20:10424022 - isvavai.cz</a>

Výsledek na webu

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=m1HjQAgSyf" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=m1HjQAgSyf</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1039/d0cy01662d" target="_blank" >10.1039/d0cy01662d</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Solvent-free ketalization of polyols over germanosilicate zeolites: The role of the nature and strength of acid sites

Popis výsledku v původním jazyce

Isomorphic substitution of silicon for germanium affords germanosilicate zeolites with weak acid centers capable of catalyzing key reactions such as Baeyer-Villiger oxidation of ketones and etherification of levulinic acid. Herein, we show for the first time that UTL (Si/Ge = 4.2) and IWW (Si/Ge = 7.2) germanosilicate zeolites are active and selective catalysts of polyol (e.g., ethylene glycol, glycerol and 1,4 butanediol) ketalization to dioxolanes. Large-pore IWW outperformed the extra-large-pore UTL zeolite in the ketalization of polyols, thus indicating diffusion limitations in bulky platelet-like UTL crystals. FTIR spectroscopy of adsorbed pyridine revealed the Lewis acidity of the UTL zeolite, whereas the more active IWW catalyst was characterized by water-induced Bronsted acidity. Increasing the activation temperature (200-450 degrees C) reduced the concentration of Bronsted acid centers in the IWW germanosilicate (i.e., 0.16; 0.07 and 0.05 mmol g(-1) for T-act = 200, 300 and 450 degrees C, respectively) but increased the number of Lewis acid sites in both zeolites. Under optimized reaction conditions (e.g., acetone/glycerol = 25, T-act = 300 degrees C), almost total transformation of glycerol into solketal was achieved within 3 h of reaction time over the IWW zeolite at room temperature (&gt;99% yield of the target product). The results from the present study clearly show that weak acid centers of germanosilicate zeolites can serve as active sites in ketalization reactions.

Název v anglickém jazyce

Solvent-free ketalization of polyols over germanosilicate zeolites: The role of the nature and strength of acid sites

Popis výsledku anglicky

Isomorphic substitution of silicon for germanium affords germanosilicate zeolites with weak acid centers capable of catalyzing key reactions such as Baeyer-Villiger oxidation of ketones and etherification of levulinic acid. Herein, we show for the first time that UTL (Si/Ge = 4.2) and IWW (Si/Ge = 7.2) germanosilicate zeolites are active and selective catalysts of polyol (e.g., ethylene glycol, glycerol and 1,4 butanediol) ketalization to dioxolanes. Large-pore IWW outperformed the extra-large-pore UTL zeolite in the ketalization of polyols, thus indicating diffusion limitations in bulky platelet-like UTL crystals. FTIR spectroscopy of adsorbed pyridine revealed the Lewis acidity of the UTL zeolite, whereas the more active IWW catalyst was characterized by water-induced Bronsted acidity. Increasing the activation temperature (200-450 degrees C) reduced the concentration of Bronsted acid centers in the IWW germanosilicate (i.e., 0.16; 0.07 and 0.05 mmol g(-1) for T-act = 200, 300 and 450 degrees C, respectively) but increased the number of Lewis acid sites in both zeolites. Under optimized reaction conditions (e.g., acetone/glycerol = 25, T-act = 300 degrees C), almost total transformation of glycerol into solketal was achieved within 3 h of reaction time over the IWW zeolite at room temperature (&gt;99% yield of the target product). The results from the present study clearly show that weak acid centers of germanosilicate zeolites can serve as active sites in ketalization reactions.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10403 - Physical chemistry

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2020

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Catalysis: Science and Technology

ISSN

2044-4753

e-ISSN

—

Svazek periodika

10

Číslo periodika v rámci svazku

24

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

11

Strana od-do

8254-8264

Kód UT WoS článku

000598674500010

EID výsledku v databázi Scopus

2-s2.0-85098102986