Two distinct [Cu-O-Cu](2+) sites with methane monooxygenase activity are identified in the zeolit... more Two distinct [Cu-O-Cu](2+) sites with methane monooxygenase activity are identified in the zeolite Cu-MOR, emphasizing that this Cu-O-Cu active site geometry, having a ∠Cu-O-Cu ∼140°, is particularly formed and stabilized in zeolite topologies. Whereas in ZSM-5 a similar [Cu-O-Cu](2+) active site is located in the intersection of the two 10 membered rings, Cu-MOR provides two distinct local structures, situated in the 8 membered ring windows of the side pockets. Despite their structural similarity, as ascertained by electronic absorption and resonance Raman spectroscopy, the two Cu-O-Cu active sites in Cu-MOR clearly show different kinetic behaviors in selective methane oxidation. This difference in reactivity is too large to be ascribed to subtle differences in the ground states of the Cu-O-Cu sites, indicating the zeolite lattice tunes their reactivity through second-sphere effects. The MOR lattice is therefore functionally analogous to the active site pocket of a metalloenzyme, demonstrating that both the active site and its framework environment contribute to and direct reactivity in transition metal ion-zeolites.
Valorization of lignin is essential for the economics of future lignocellulosic biorefineries. Li... more Valorization of lignin is essential for the economics of future lignocellulosic biorefineries. Lignin is converted into novel polymer building blocks through four steps: catalytic hydroprocessing of softwood to form 4-alkylguaiacols, their conversion into 4-alkylcyclohexanols, followed by dehydrogenation to form cyclohexanones, and Baeyer-Villiger oxidation to give caprolactones. The formation of alkylated cyclohexanols is one of the most difficult steps in the series. A liquid-phase process in the presence of nickel on CeO2 or ZrO2 catalysts is demonstrated herein to give the highest cyclohexanol yields. The catalytic reaction with 4-alkylguaiacols follows two parallel pathways with comparable rates: 1) ring hydrogenation with the formation of the corresponding alkylated 2-methoxycyclohexanol, and 2) demethoxylation to form 4-alkylphenol. Although subsequent phenol to cyclohexanol conversion is fast, the rate is limited for the removal of the methoxy group from 2-methoxycyclohexano...
In the valorization of α-pinene, which is an important biomass intermediate derived from turpenti... more In the valorization of α-pinene, which is an important biomass intermediate derived from turpentine oil, hierarchical (mesoporous) zeolites represent a superior class of catalysts. Hierarchical USY, ZSM-5, and beta zeolites have been prepared, characterized, and catalytically evaluated, with the aim of combining the highest catalytic performance with the most sustainable synthetic protocol. These zeolites are prepared by alkaline treatment in aqueous solutions of NH4 OH, NaOH, diethylamine, and NaOH complemented with tetrapropylammonium bromide. The hierarchical USY zeolite is the most attractive catalyst of the tested series, and is able to combine an overall organic-free synthesis with an up to sixfold activity enhancement and comparable selectivity over the conventional USY zeolite. This superior performance relates to a threefold greater activity than that of the commercial standard, namely, H2 SO4 /TiO2 . Correlation of the obtained benefits to the amount of solid lost during t...
... SBA-15 for the oxidative dehydrogenation of isobutane and propane Yolanda Segura a, Johan S. ... more ... SBA-15 for the oxidative dehydrogenation of isobutane and propane Yolanda Segura a, Johan S. Paul b, Kevin Huyghe b ... [25] M. Baltes, K. Cassiers, P. Van der Voort ... [26] MJ Jia, RX Valenzuela, P. Amoros, D. Beltran-Porter, J. EI-Haskouri, MD Marcos, V. Cortes Corberan, Catal. ...
The catalytic activity of alkaline and earth alkaline-modified silica-supported metal oxide was i... more The catalytic activity of alkaline and earth alkaline-modified silica-supported metal oxide was investigated for epoxidizing propylene with nitrous oxide. Iron oxide gave the best results, and surprisingly chromium oxide also produced propylene oxide (PO). Unmodified iron oxide catalyst showed low oxidation activity and produced propanal (57% selectivity) in concert with small amounts of acrolein, allyl alcohol, and acetone. After modification,
... Materials. [ECS Transactions 19, 201 (2009)]. Alexander Klekachev, Mirco Cantoro,Amirhasan No... more ... Materials. [ECS Transactions 19, 201 (2009)]. Alexander Klekachev, Mirco Cantoro,Amirhasan Nourbakhsh, Marleen H. Van der Veen, Francesca Clemente, Andre L. Stesmans, Bert Sels, Marc Heyns, Stefan De Gendt. Abstract. ...
Green Chem., 2010, 12, 1083-1089 DOI:10.1039/B921284A (Paper). Zeolite-catalysed conversion of C ... more Green Chem., 2010, 12, 1083-1089 DOI:10.1039/B921284A (Paper). Zeolite-catalysed conversion of C 3 sugars to alkyl lactates. Paolo P. Pescarmonaa, Kris PF Janssena, Chloë Delaetb, Christophe Stroobantsa, Kristof Houthoofd ...
Two distinct [Cu-O-Cu](2+) sites with methane monooxygenase activity are identified in the zeolit... more Two distinct [Cu-O-Cu](2+) sites with methane monooxygenase activity are identified in the zeolite Cu-MOR, emphasizing that this Cu-O-Cu active site geometry, having a ∠Cu-O-Cu ∼140°, is particularly formed and stabilized in zeolite topologies. Whereas in ZSM-5 a similar [Cu-O-Cu](2+) active site is located in the intersection of the two 10 membered rings, Cu-MOR provides two distinct local structures, situated in the 8 membered ring windows of the side pockets. Despite their structural similarity, as ascertained by electronic absorption and resonance Raman spectroscopy, the two Cu-O-Cu active sites in Cu-MOR clearly show different kinetic behaviors in selective methane oxidation. This difference in reactivity is too large to be ascribed to subtle differences in the ground states of the Cu-O-Cu sites, indicating the zeolite lattice tunes their reactivity through second-sphere effects. The MOR lattice is therefore functionally analogous to the active site pocket of a metalloenzyme, demonstrating that both the active site and its framework environment contribute to and direct reactivity in transition metal ion-zeolites.
Valorization of lignin is essential for the economics of future lignocellulosic biorefineries. Li... more Valorization of lignin is essential for the economics of future lignocellulosic biorefineries. Lignin is converted into novel polymer building blocks through four steps: catalytic hydroprocessing of softwood to form 4-alkylguaiacols, their conversion into 4-alkylcyclohexanols, followed by dehydrogenation to form cyclohexanones, and Baeyer-Villiger oxidation to give caprolactones. The formation of alkylated cyclohexanols is one of the most difficult steps in the series. A liquid-phase process in the presence of nickel on CeO2 or ZrO2 catalysts is demonstrated herein to give the highest cyclohexanol yields. The catalytic reaction with 4-alkylguaiacols follows two parallel pathways with comparable rates: 1) ring hydrogenation with the formation of the corresponding alkylated 2-methoxycyclohexanol, and 2) demethoxylation to form 4-alkylphenol. Although subsequent phenol to cyclohexanol conversion is fast, the rate is limited for the removal of the methoxy group from 2-methoxycyclohexano...
In the valorization of α-pinene, which is an important biomass intermediate derived from turpenti... more In the valorization of α-pinene, which is an important biomass intermediate derived from turpentine oil, hierarchical (mesoporous) zeolites represent a superior class of catalysts. Hierarchical USY, ZSM-5, and beta zeolites have been prepared, characterized, and catalytically evaluated, with the aim of combining the highest catalytic performance with the most sustainable synthetic protocol. These zeolites are prepared by alkaline treatment in aqueous solutions of NH4 OH, NaOH, diethylamine, and NaOH complemented with tetrapropylammonium bromide. The hierarchical USY zeolite is the most attractive catalyst of the tested series, and is able to combine an overall organic-free synthesis with an up to sixfold activity enhancement and comparable selectivity over the conventional USY zeolite. This superior performance relates to a threefold greater activity than that of the commercial standard, namely, H2 SO4 /TiO2 . Correlation of the obtained benefits to the amount of solid lost during t...
... SBA-15 for the oxidative dehydrogenation of isobutane and propane Yolanda Segura a, Johan S. ... more ... SBA-15 for the oxidative dehydrogenation of isobutane and propane Yolanda Segura a, Johan S. Paul b, Kevin Huyghe b ... [25] M. Baltes, K. Cassiers, P. Van der Voort ... [26] MJ Jia, RX Valenzuela, P. Amoros, D. Beltran-Porter, J. EI-Haskouri, MD Marcos, V. Cortes Corberan, Catal. ...
The catalytic activity of alkaline and earth alkaline-modified silica-supported metal oxide was i... more The catalytic activity of alkaline and earth alkaline-modified silica-supported metal oxide was investigated for epoxidizing propylene with nitrous oxide. Iron oxide gave the best results, and surprisingly chromium oxide also produced propylene oxide (PO). Unmodified iron oxide catalyst showed low oxidation activity and produced propanal (57% selectivity) in concert with small amounts of acrolein, allyl alcohol, and acetone. After modification,
... Materials. [ECS Transactions 19, 201 (2009)]. Alexander Klekachev, Mirco Cantoro,Amirhasan No... more ... Materials. [ECS Transactions 19, 201 (2009)]. Alexander Klekachev, Mirco Cantoro,Amirhasan Nourbakhsh, Marleen H. Van der Veen, Francesca Clemente, Andre L. Stesmans, Bert Sels, Marc Heyns, Stefan De Gendt. Abstract. ...
Green Chem., 2010, 12, 1083-1089 DOI:10.1039/B921284A (Paper). Zeolite-catalysed conversion of C ... more Green Chem., 2010, 12, 1083-1089 DOI:10.1039/B921284A (Paper). Zeolite-catalysed conversion of C 3 sugars to alkyl lactates. Paolo P. Pescarmonaa, Kris PF Janssena, Chloë Delaetb, Christophe Stroobantsa, Kristof Houthoofd ...
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