Co-reporter:G. Tarantino;L. Botti;N. Dimitratos;C. Hammond
RSC Advances (2011-Present) 2017 vol. 7(Issue 48) pp:30185-30190
Publication Date(Web):2017/06/08
DOI:10.1039/C7RA06180C
Mechanochemically-prepared, Ag2O-containing solid materials, are shown to be efficient heterogeneous catalysts for the synthesis of C(sp3)–F bonds via decarboxylative fluorination. Five catalytic cycles without loss of intrinsic activity could be performed with the optimal catalyst, composed of 1 wt% Ag2O supported on TiO2 (P25), despite the challenging conditions. The catalyst is easily prepared from the corresponding oxides in 20 minutes by simple mechanical mixing methods. In addition to ease of separation and re-use, the turnover numbers obtained over the solid catalyst are over one order of magnitude higher than those obtained with the state-of-the-art homogeneous catalyst, AgNO3, under otherwise identical conditions. To the best of our knowledge, this represents the first true heterogeneous catalyst for the selective formation of C(sp3)–F bonds with electrophilic fluorine donors, representing a major breakthrough in the field of catalytic fluorination.
Co-reporter:D. Padovan;A. Al-Nayili;C. Hammond
Green Chemistry (1999-Present) 2017 vol. 19(Issue 12) pp:2846-2854
Publication Date(Web):2017/06/19
DOI:10.1039/C7GC00160F
The catalytic valorisation of bio-renewable feedstock often relies upon multi-stage processing of highly-functionalised substrates, resulting in selectivity and processs engineering challenges. Herein, we demonstrate that a bifunctional zeolitic material, containing both Lewis and Brønsted acid sites in a single catalytic material, permits the continuous production of bio-renewable furanic ethers, such as (butoxy)methyl furan, which possess potential as fuel additives. In contrast to mono-functional catalysts and physical mixtures thereof, the bifunctional Sn- and Al-containing BEA zeolite results in uniquely-high levels of activity, selectivity and stability. Optimal results were obtained over a bifunctional catalyst containing 2 wt% Sn and 0.5 wt% Al, prepared by modified solid state incorporation, which was highly selective (>75%) to the desired ether for over 100 h on stream, and for over 3000 substrate turnovers.
Co-reporter:Abbas Al-Nayili, Keiko Yakabi and Ceri Hammond
Journal of Materials Chemistry A 2016 vol. 4(Issue 4) pp:1373-1382
Publication Date(Web):21 Dec 2015
DOI:10.1039/C5TA08709K
Pore size limitations typically limit the applicability of Lewis acidic zeolites, such as titano- and stanno-silicates, to catalytic processes based on small-to-mid sized substrates, and increase their rates of deactivation, prohibiting further exploitation. Herein, we demonstrate that tin-containing zeolites possessing modified hierarchical BEA matrices can be prepared. These hierarchical stannosilicates are able to mediate the catalytic conversion of bulky ketone substrates, a pertaining challenge in the field that purely microporous analogues are unable to mediate. Deactivation studies in the continuous regime also demonstrate the exceptional stability of hierarchical Sn-Beta compared to purely microporous Sn-Beta, with <20% loss of activity observed over 700 h on stream. In contrast, the purely microporous analogue lost ±70% activity in only 200 h. To the best of our knowledge, this is the first time a stannosilicate with a beneficial hierarchical BEA framework has been prepared, and the first evidence of cyclododecanone valorisation with stannosilicate catalysts.
Co-reporter:Dr. Ceri Hammond;Dr. Ive Hermans;Dr. Nikolaos Dimitratos
ChemCatChem 2015 Volume 7( Issue 3) pp:434-440
Publication Date(Web):
DOI:10.1002/cctc.201402642
Abstract
Developing inorganic materials that can mimic nature’s ability to selectively oxidise inert CH bonds remains a topic of intense scientific research. In recent years, zeolitic materials containing Fe and/or Cu have been shown to be highly active, heterogeneous catalysts for the selective oxidation of alkanes (including methane), amongst a range of other related oxidation challenges. By using resonance-enhanced Raman spectroscopy, we demonstrate that, following high-temperature pre-treatment (activation), Fe-containing ZSM-5 possesses an active binuclear core, and forms a key FeOOH intermediate upon activation with H2O2. Both factors are reminiscent of biological oxidation catalysts, and may account for the unique ability of this material to selectively oxidise methane to methanol at low temperature.
Co-reporter:Dr. Ceri Hammond;Daniele Padovan;Abbas Al-Nayili;Dr. Peter. P. Wells;Dr. Emma K. Gibson;Dr. Nikolaos Dimitratos
ChemCatChem 2015 Volume 7( Issue 20) pp:3322-3331
Publication Date(Web):
DOI:10.1002/cctc.201500545
Abstract
Lewis acidic zeolites are rapidly emerging liquid-phase Lewis acid catalysts. Nevertheless, their inefficient synthesis procedure currently prohibits greater utilization and exploitation of these promising materials. Herein, we demonstrate that SnIV-containing zeolite beta can readily be prepared both selectively and extremely rapidly by solid-state incorporation (SSI) method. Through a combination of spectroscopic (XRD, UV/Vis, X-ray absorption, magic-angle spinning NMR, and diffuse reflectance infrared Fourier transform spectroscopy) studies, we unambiguously demonstrate that site-isolated, isomorphously substituted SnIV sites dominate the Sn population up to a loading of 5 wt % Sn. These sites are identical to those found in conventionally prepared Sn-beta, and result in our SSI material exhibiting identical levels of intrinsic activity (that is, turnover frequency) despite the threefold increase in Sn loading, and the extremely rapid and benign nature of our preparation methodology. We also identify the presence of spectator sites, in the form of SnIV oligomers, at higher levels of Sn loading. The consequences of this mixed population with regards to catalysis (Meerwein–Pondorf–Verley reaction and glucose isomerization) are also identified.
Co-reporter:Abbas Al-Nayili, Keiko Yakabi and Ceri Hammond
Journal of Materials Chemistry A 2016 - vol. 4(Issue 4) pp:NaN1382-1382
Publication Date(Web):2015/12/21
DOI:10.1039/C5TA08709K
Pore size limitations typically limit the applicability of Lewis acidic zeolites, such as titano- and stanno-silicates, to catalytic processes based on small-to-mid sized substrates, and increase their rates of deactivation, prohibiting further exploitation. Herein, we demonstrate that tin-containing zeolites possessing modified hierarchical BEA matrices can be prepared. These hierarchical stannosilicates are able to mediate the catalytic conversion of bulky ketone substrates, a pertaining challenge in the field that purely microporous analogues are unable to mediate. Deactivation studies in the continuous regime also demonstrate the exceptional stability of hierarchical Sn-Beta compared to purely microporous Sn-Beta, with <20% loss of activity observed over 700 h on stream. In contrast, the purely microporous analogue lost ±70% activity in only 200 h. To the best of our knowledge, this is the first time a stannosilicate with a beneficial hierarchical BEA framework has been prepared, and the first evidence of cyclododecanone valorisation with stannosilicate catalysts.
