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15 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2 [Next/Last]

Instruments / Technical Area	Publication Details	Published
	Continuous-flow synthesis of mesoporous SBA-15 Christopher M. A. Parlett , Hamidreza Arandiyan , Lee J. Durndell , Mark A. Isaacs , Antonio Torres Lopez , Roong J. Wong , Karen Wilson , Adam Lee Microporous And Mesoporous Materials 329 DOI: 10.1016/j.micromeso.2021.111535 Show Abstract ▼ Abstract: Ordered mesoporous silicas are widely used in separation science and catalysis, however, their slow batch synthesis is a barrier to scale-up and new applications. SBA-15 is one of the most extensively studied and commercially available mesoporous silicas, whose textural properties can be readily tuned through judicious choice of synthesis conditions. Here we demonstrate the continuous flow synthesis of SBA-15 in high yield at 80 °C using a simple tube reactor without any mixing device. The resulting SBA-15 exhibits excellent textural properties, with a BET surface area of 566 m2 g−1 and ordered 5.1 nm mesopore channels in a p6mm arrangement, akin to those from conventional batch synthesis, but with far higher productivity than previously reported in batch or flow (5.3 g L−1 h−1 versus 0.4 and 0.6 g L−1 h−1 respectively).	Nov 2021
B18-Core EXAFS	Palladium-doped hierarchical ZSM-5 for catalytic selective oxidation of allylic and benzylic alcohols Shengzhe Ding , Muhammad Ganesh , Yilai Jiao , Xiaoxia Ou , Mark Isaacs , Mark S'Ari , Antonio Torres Lopez , Xiaolei Fan , Christopher M. A. Parlett Royal Society Open Science 8 DOI: 10.1098/rsos.211086 Diamond Proposal Number(s): [15151] Open Access Show Abstract ▼ Abstract: Hierarchical zeolites have the potential to provide a breakthrough in transport limitation, which hinders pristine microporous zeolites and thus may broaden their range of applications. We have explored the use of Pd-doped hierarchical ZSM-5 zeolites for aerobic selective oxidation (selox) of cinnamyl alcohol and benzyl alcohol to their corresponding aldehydes. Hierarchical ZSM-5 with differing acidity (H-form and Na-form) were employed and compared with two microporous ZSM-5 equivalents. Characterization of the four catalysts by X-ray diffraction, nitrogen porosimetry, NH3 temperature-programmed desorption, CO chemisorption, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy allowed investigation of their porosity, acidity, as well as Pd active sites. The incorporation of complementary mesoporosity, within the hierarchical zeolites, enhances both active site dispersion and PdO active site generation. Likewise, alcohol conversion was also improved with the presence of secondary mesoporosity, while strong Brønsted acidity, present solely within the H-form systems, negatively impacted overall selectivity through undesirable self-etherification. Therefore, tuning support porosity and acidity alongside active site dispersion is paramount for optimal aldehyde production.	Oct 2021
B18-Core EXAFS	PdCu single atom alloys supported on alumina for the selective hydrogenation of furfural Mohammed J. Islam , Marta Granollers Mesa , Amin Osatiashtiani , Jinesh C. Manayil , Mark A. Isaacs , Martin J. Taylor , Sotirios Tsatsos , Georgios Kyriakou Applied Catalysis B: Environmental 1 DOI: 10.1016/j.apcatb.2021.120652 Diamond Proposal Number(s): [19850] Show Abstract ▼ Abstract: Single-atom catalysts serve as a skilful control of precious metals on heterogenous catalysts where all active sites are accessible for catalytic reactions. Here we report the adoption of PdCu single-atom alloys supported on alumina for the selective hydrogenation of furfural. This is a special class of an atom efficient, single-site catalyst where trace concentrations of Pd atoms (0.0067 wt%) displace surface Cu sites on the host nanoparticle. Confirmed by EXAFS, the Pd atoms are entirely coordinated to Cu, with Pd-Cu bond lengths identical to that of a Cu-Cu bond. Selectively surface oxidised catalysts also confirm surface Pd atoms by EXAFS. These catalysts improve the conversion of furfural to furfuryl alcohol compared to monometallic catalysts, as they have the advantages of Cu (high selectivity but poor activity) and Pd catalysts (superior activity but unselective) without the drawbacks, making them the optimal catalysts for green/atom efficient catalysis.	Aug 2021
I13-2-Diamond Manchester Imaging	Enhanced near-infrared absorption for laser powder bed fusion using reduced graphene oxide Chu Lun Alex Leung , Iuliia Elizarova , Mark Isaacs , Shashidhara Marathe , Eduardo Saiz , Peter D. Lee Applied Materials Today 23 DOI: 10.1016/j.apmt.2021.101009 Diamond Proposal Number(s): [19354] Open Access Show Abstract ▼ Abstract: Laser powder bed fusion (LPBF) is a revolutionary manufacturing technology that fabricates parts with unparalleled complexity, layer-by-layer. However, there are limited choices of commercial powders for LPBF, constrained partly by the laser absorbance, an area that is not well investigated. Carbon additives are commonly used to promote near infra-red (NIR) absorbance of the powders but their efficiency is limited. Here, we combine operando synchrotron X-ray imaging with chemical characterisation techniques to elucidate the role of additives on NIR absorption, melt track and defect evolution mechanisms during LPBF. We employ a reduced graphene oxide (rGO) additive to enable LPBF of low NIR absorbance powder, SiO2, under systematic build conditions. This work successfully manufactured glass tracks with a high relative density (99.6%) and overhang features (> 5 mm long) without pre/post heat treatment. Compared to conventional carbon additives, the rGO increases the powder's NIR absorbance by ca. 3 times and decreases the warpage and porosity in LPBF glass tracks. Our approach will dramatically widen the palette of materials for laser processing and enable existing LPBF machines to process low absorbance powder, such as SiO2, using a NIR beam.	Jun 2021
	Atom efficient PtCu bimetallic catalysts and ultra dilute alloys for the selective hydrogenation of furfural Martin J. Taylor , Simon K. Beaumont , Mohammed J. Islam , Sotirios Tsatsos , Christopher A. M. Parlett , Mark A. Isaacs , Georgios Kyriakou Applied Catalysis B: Environmental DOI: 10.1016/j.apcatb.2020.119737 Show Abstract ▼ Abstract: A range of Pt:Cu bimetallic nanoparticles were investigated for the liquid-phase selective hydrogenation of furfural, an important platform biomass feedstock. Alloying of the two metals had a profound effect on the overall catalytic activity, providing superior rates of reaction and achieving the needed high selectivity towards furfuryl alcohol. Furthermore, we investigated the catalytic activity of an Ultra Dilute Alloy (UDA) formed via the galvanic replacement of Cu atoms by Pt atoms on dispersed host Cu nanoparticles (atomic ratio Pt:Cu 1:20). This UDA, after overcoming an induction period, exhibits exceptionally high initial rates of hydrogenation under modest hydrogen pressures of 10 and 20 bar, rivalling the catalytic turnover for the monometallic Pt (containing 12 times more Pt), and outdoing the pure Cu or other compositions of bimetallic nanoparticle alloy catalysts. These atom efficient catalysts are ideal candidates for the valorization of furfural due to their activity and vastly greater economic viability.	Nov 2020
	Bandgap lowering in mixed alloys of Cs2Ag(SbxBi1−x)Br6 double perovskite thin films Zewei Li , Seán R. Kavanagh , Mari Napari , Robert G. Palgrave , Mojtaba Abdi-Jalebi , Zahra Andaji-Garmaroudi , Daniel W. Davies , Mikko Laitinen , Jaakko Julin , Mark A. Isaacs , Richard H. Friend , David O. Scanlon , Aron Walsh , Robert L. Z. Hoye Journal Of Materials Chemistry A 8, 21780 - 21788 DOI: 10.1039/D0TA07145E Open Access Show Abstract ▼ Abstract: Halide double perovskites have gained significant attention, owing to their composition of low-toxicity elements, stability in air and long charge-carrier lifetimes. However, most double perovskites, including Cs2AgBiBr6, have wide bandgaps, which limits photoconversion efficiencies. The bandgap can be reduced through alloying with Sb3+, but Sb-rich alloys are difficult to synthesize due to the high formation energy of Cs2AgSbBr6, which itself has a wide bandgap. We develop a solution-based route to synthesize phase-pure Cs2Ag(SbxBi1−x)Br6 thin films, with the mixing parameter x continuously varying over the entire composition range. We reveal that the mixed alloys (x between 0.5 and 0.9) demonstrate smaller bandgaps than the pure Sb- and Bi-based compounds. The reduction in the bandgap of Cs2AgBiBr6 achieved through alloying (170 meV) is larger than if the mixed alloys had obeyed Vegard's law (70 meV). Through in-depth computations, we propose that bandgap lowering arises from the type II band alignment between Cs2AgBiBr6 and Cs2AgSbBr6. The energy mismatch between the Bi and Sb s and p atomic orbitals, coupled with their non-linear mixing, results in the alloys adopting a smaller bandgap than the pure compounds. Our work demonstrates an approach to achieve bandgap reduction and highlights that bandgap bowing may be found in other double perovskite alloys by pairing together materials forming a type II band alignment.	Oct 2020
	Shining light on the solid–liquid interface: in situ / operando monitoring of surface catalysis Leila Negahdar , Christopher M. A. Parlett , Mark A. Isaacs , Andrew M. Beale , Karen Wilson , Adam F. Lee Catalysis Science & Technology 10, 5362 - 5385 DOI: 10.1039/D0CY00555J Open Access Show Abstract ▼ Abstract: Many industrially important chemical transformations occur at the interface between a solid catalyst and liquid reactants, despite which relatively little attention has been paid to spectroscopic methods for interrogating the working solid–liquid interface. This partly reflects a limited number of analytical techniques that give access to interface-specific information. Direct observation of surface species at catalytic solid–liquid interfaces is a daunting challenge for many in situ techniques due to the low concentration and/or short lifetime of chemical species in dynamic reactions. This review discusses the application of in situ and operando spectroscopies to probe solid–liquid interfaces, with a focus on the resulting mechanistic insight in the context of catalysis for sustainable chemistry.	Aug 2020
	Metal–acid synergy: Hydrodeoxygenation of anisole over Pt/Al‐SBA‐15 Atal Shivhare , James A. Hunns , Lee J. Durndell , Christopher M. A. Parlett , Mark A. Isaacs , Adam F. Lee , Karen Wilson Chemsuschem 2013 DOI: 10.1002/cssc.202000764 Show Abstract ▼ Abstract: Hydrodeoxygenation (HDO) is a promising technology to upgrade fast pyrolysis bio‐oils but it requires active and selective catalysts. Here we explore the synergy between the metal and acid sites in the HDO of anisole, a model pyrolysis bio‐oil compound, over mono‐ and bi‐functional Pt/(Al)‐SBA‐15 catalysts. Ring hydrogenation of anisole to methoxycyclohexane occurs over metal sites and is structure sensitive; it is favored over small (4 nm) Pt nanoparticles, which confer a turnover frequency (TOF) of approximately 2000 h−1 and a methoxycyclohexane selectivity of approximately 90 % at 200 °C and 20 bar H2; in contrast, the formation of benzene and the desired cyclohexane product appears to be structure insensitive. The introduction of acidity to the SBA‐15 support promotes the demethyoxylation of the methoxycyclohexane intermediate, which increases the selectivity to cyclohexane from 15 to 92 % and the cyclohexane productivity by two orders of magnitude (from 15 to 6500 mmol gPt−1 h−1). Optimization of the metal–acid synergy confers an 865‐fold increase in the cyclohexane production per gram of Pt and a 28‐fold reduction in precious metal loading. These findings demonstrate that tuning the metal–acid synergy provides a strategy to direct complex catalytic reaction networks and minimize precious metal use in the production of bio‐fuels.	Jun 2020
	Ethanol steam reforming for hydrogen production over hierarchical macroporous mesoporous SBA-15 supported nickel nanoparticles Christopher M. A. Parlett , Lee J. Durndell , Mark A. Isaacs , Xiaotong Liu , Chunfei Wu Topics In Catalysis 63, 403 - 412 DOI: 10.1007/s11244-020-01265-4 Open Access Show Abstract ▼ Abstract: The influence of complementary macropores, present in hierarchical macroporous mesoporous SBA-15, on the performance of supported Ni nanoparticles for ethanol steam reforming has been investigated. The increased open nature of the architecture, afforded through the incorporation of the secondary macropore network, enables superior metal dispersion. This, in turn, enhances catalytic hydrogen production performance through the generation of a greater density of active sites.	May 2020
B18-Core EXAFS	The effect of metal precursor on copper phase dispersion and nanoparticle formation for the catalytic transformations of furfural Mohammed J. Islam , Marta Granollersmesa , Amin Osatiashtiani , Martin J. Taylor , Jinesh C. Manayil , Christopher M. A. Parlett , Mark A. Isaacs , Georgios Kyriakou Applied Catalysis B: Environmental DOI: 10.1016/j.apcatb.2020.119062 Show Abstract ▼ Abstract: The formation of copper-based catalysts ranging from nanoparticles to isolated and dimeric Cu species supported on nanophased alumina is reported and utilised for the catalytic liquid-phase hydrogenation of furfural. The materials were synthesised via wet impregnation using various copper precursors (nitrate, acetate and sulphate) at two different loadings. A high Cu loading (5 wt%) led to the formation of well-defined nanoparticles, while a lower loading (1 wt%) generated a highly dispersed phase consisting mostly of atomic and dimeric Cu species dispersed on Al2O3. The catalytic reaction was found to be structure sensitive, promoting decarbonylation reactions with low Cu loading. Copper sulphate derived catalysts were found to severely decrease furfuryl alcohol selectivity from 94.6% to 0.8%, promoting the formation of side reactions. The sulphur-free catalysts represent a greener and more sustainable alternative to the toxic catalysts currently used in industry, operating at milder conditions of 50 °C and 1.5 bar H2.	Apr 2020

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