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Open Access
Abstract: Furfural (Fur) represents an interesting bio-based platform chemical to pave the way to enhanced biorefinery integration in the modern chemicals industry. The production of this xylose- derived compound by its dehydration is catalysed by Brønsted acidity and has effectively been performed in biphasic systems using methyl isobutyl ketone (MIBK), where furfural is effectively partitioned. A selection of commercially available solid-acid catalysts were evaluated (different ion exchange resins, zeolites and sulfated zirconia), with top candidates being subjected to recycling experiments over six runs with carbon deposition removal and acid site regeneration. A sulfated zirconia (SO2/ZrO2-1) catalyst proved effective with maximum yield of Fur of 53.8% after 180 mins at 160 °C, with xylose conversion of 98.4%. A phenomenological approach to model developments was employed to describe the formation of each component of the reaction scheme and distribution in a biphasic system, with 18 separate kinetic models including both homo- and heterogeneous reaction pathways reported. The most optimal model, identified through statistical model discrimination (RMSE = 0.088), was a pseudohomogenous model with first order reaction kinetics for xylose conversion to Fur via a reactive intermediate and second order with respect to humin formation. Apparent activation energies for xylose dehydration were reported at 44.70 ± 7.89 kJ mol-−1, with results stating the formation of Fur proceeded preferentially through this reactive intermediate.
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Jan 2025
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Shengzhe
Ding
,
Dario Luis
Fernandez Ainaga
,
Min
Hu
,
Boya
Qiu
,
Ushna
Khalid
,
Carmine
D’agostino
,
Xiaoxia
Ou
,
Ben
Spencer
,
Xiangli
Zhong
,
Yani
Peng
,
Nicole
Hondow
,
Constantinos
Theodoropoulos
,
Yilai
Jiao
,
Christopher
Parlett
,
Xiaolei
Fan
Open Access
Abstract: Spatial control over features within multifunctional catalysts can unlock efficient one-pot cascade reactions, which are themselves a pathway to aviation biofuels via hydrodeoxygenation. A synthesis strategy that encompasses spatial orthogonality, i.e., one in which different catalytic species are deposited exclusively within discrete locations of a support architecture, is one solution that permits control over potential interactions between different sites and the cascade process. Here, we report a Pd doped hierarchical zeolite, in which Pd nanoparticles are selectively deposited within the mesopores, while acidity is retained solely within the micropores of ZSM-5. This spatial segregation facilitates hydrodeoxygenation while suppressing undesirable decarboxylation and decarbonation, yielding significant enhancements in activity (30.6 vs 3.6 moldodecane molPd−1 h−1) and selectivity (C12:C11 5.2 vs 1.9) relative to a conventionally prepared counterpart (via wet impregnation). Herein, multifunctional material design can realise efficient fatty acid hydrodeoxygenation, thus advancing the field and inspiring future developments in rationalised catalyst design.
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Sep 2024
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Open Access
Abstract: Synthesis of 2,5-furandicarboxylic acid (FDCA) can be achieved via catalytic oxidation of 5-hydroxymethylfurfural (5-HMF), in which both base and catalyst play important roles. This work presents the development of a simple synthesis method (based on a commercial parent 10 wt.% Pd/C catalyst) to prepare the bimetallic AuPd alloy catalysts (i. e., AuPd/C) for selective 5-HMF oxidation to FDCA. When using the strong base of NaOH, Pd and Au cooperate to promote FDCA formation when deployed either separately (as a physical mixture of the monometallic Au/C and Pd/C catalysts) or ideally alloyed (AuPd/C), with complete 5-HMF conversion and FDCA yields of 66 % vs 77 %, respectively. However, NaOH also promoted the formation of undesired by-products, leading to poor mass balances (<81 %). Comparatively, under weak base conditions (using NaHCO3), an increase in Au loading in the AuPd/C catalysts enhances 5-HMF conversion and FDCA productivity (due to the enhanced carbonyl oxidation capacity) which coincides with a superior mass balances of >97 %. Yet, the excessive Pd content in the AuPd/C catalysts was not beneficial in promoting FDCA formation.
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Oct 2023
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B18-Core EXAFS
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Run
Zou
,
Sarayute
Chansai
,
Shaojun
Xu
,
Bing
An
,
Shima
Zainal
,
Yangtao
Zhou
,
Ruojia
Xin
,
Pan
Gao
,
Guangjin
Hou
,
Carmine
D’agostino
,
Stuart M.
Holmes
,
Christopher
Hardacre
,
Yilai
Jiao
,
Xiaolei
Fan
Diamond Proposal Number(s):
[29271]
Open Access
Abstract: Stabilisation of metal species using hydroxyl-rich dealuminated zeolites is a promising method for catalysis. However, insights into the interactions between the hydroxyl groups in zeolite and noble metals and their effects on catalysis are not yet fully understood. Herein, comparative studies were conducted using Pt catalysts supported on hydroxyl-rich dealuminated Beta (deAl-Beta) and the pristine proton-form Beta (H-Beta) for catalytic oxidation of toluene. The findings suggest that during impregnation the Pt precursor (i.e., Pt(NH3)4(NO3)2) interacted with different sites on deAl-Beta and H-Beta, leading to the formation of supported Pt nanoparticles with different physicochemical properties. The resulting Pt/deAl-Beta exhibited improved activity and anti-coking ability than Pt/H-Beta in catalytic toluene oxidation. According to toluene-TPD, 1H NMR relaxation and in situ DRIFTS characterisation, the enhanced performance of Pt/deAl-Beta could be ascribed to (i) the active Pt-O sites stabilised by hydroxyl groups, which interact with toluene easily for conversion, and (ii) the acid-free feature of the deAl-Beta support, which avoids the formation of coke precursors (such as benzoate species) on the catalyst surface. Findings of the work can serve as the design guidelines for making effective supported metal catalysts using zeolitic carriers.
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Sep 2023
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Open Access
Abstract: Realising sustainability within the chemical industry necessitates a shift from the traditional linear approach, based on crude oil, to a circular economy using alternative feedstock such as biomass, from which 5-hydroxymethylfurfural (HMF) is a potentially highly interesting platform chemical. While its production is relatively straightforward via the dehydration of fructose, derived from either saccharides or lignocellulosic biomass, its production is hindered by undesirable side reactions, which diminish overall HMF yield. Here we report a green, highly selective approach to producing 5-hydroxymethylfurfural (HMF) from fructose based on the co-deployment of a biphasic reaction media, microwave radiation, and a commercial solid acid catalyst (FAU Y zeolites). Following an initial evaluation of catalyst-solvent interactions and diffusion, a hierarchical mesoporous Y zeolite was chosen and deployed within a range of reaction media and process conditions for process optimisation, identifying a biphasic system consisting of ((6:4 Water:DMSO) / (7:3 MIBK:2-BuOH)) as the optimal reaction media. This solvent combination facilitated an HMF yield of ~73.9 mol% with an excellent selectivity of ~86.1 % at 160 ℃ after only 45 minutes under the microwave condition. These, in turn, result in optimal energy efficiency and excellent green credentials relative to conventional heating.
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Jul 2023
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Open Access
Abstract: In this paper we carry out a surface study of promising supported solid acid catalysts commonly used for the production of high value chemicals derived from glycerol. In particular, γ, θ and α alumina (Al2O3) were modified by (i) grafting with 5 wt% zirconia, (ii) doping with 30 wt% silicotungstic acid (STA), and (iii) using both zirconia and STA. The aim is to rationalise the effect of these different parameters on structural properties and surface adsorption through a comprehensive multi-technique approach, including recently developed NMR relaxation techniques. XRD and laser Raman spectroscopy confirmed a strong interaction between STA and the γ-/θ-Al2O3 resulting in a distortion of the supported STA Keggin structure relative to that of bulk STA. Conversely, a much weaker interaction between the supported STA and α-Al2O3 was measured. NMR relaxation demonstrated that the STA doping increases the adsorption properties of the catalyst, particularly for γ-/θ-Al2O3. For catalysts based on α-Al2O3, such effect was negligible. Thermogravimetric/differential thermogravimetry (TGA/DTG) analysis suggested that zirconia-grafted and non-grafted θ-Al2O3 and γ-Al2O3 are suitable materials for increasing the thermal stability of STA whereas α-Al2O3 (both grafted and non-grafted) does not improve the thermal stability of STA.
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Dec 2022
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E01-JEM ARM 200CF
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Shanshan
Xu
,
Thomas J. A.
Slater
,
Hong
Huang
,
Yangtao
Zhou
,
Yilai
Jiao
,
Christopher M. A.
Parlett
,
Shaoliang
Guan
,
Sarayute
Chansai
,
Shaojun
Xu
,
Xinrui
Wang
,
Christopher
Hardacre
,
Xiaolei
Fan
Diamond Proposal Number(s):
[29468]
Open Access
Abstract: The stability of catalysts in dry reforming of methane (DRM) is a known issue. In this paper an encapsulation strategy has been employed to improve the stability compared with conventional impregnation methods. Herein, nickel nanoparticles encapsulated in silicalite-1 were prepared using a range of methods including post treatment, direct hydrothermal and seed-directed methods to investigate the effect of synthesis protocol on the properties of catalysts, such as degree of encapsulation and Ni dispersion, and anti-coking/-sintering performance in DRM. The Ni@SiO2-S1 catalysts obtained by the seed-directed synthesis presented the full encapsulation of Ni NPs by the zeolite framework with small particle sizes (∼2.9 nm) and strong metal-support interaction, which could sterically hinder the migration/aggregation of Ni NPs and carbon deposition. Therefore, Ni@SiO2-S1 showed stable CO2/CH4 conversions of 80% and 73%, respectively, with negligible metal sintering and coking deposition (∼0.5 wt.%) over 28 h, which outperformed the other catalysts prepared. In contrast, the catalysts developed by the post-treatment and ethylenediamine-protected hydrothermal methods showed the co-existence of Ni phase on the internal and external surfaces, i.e. incomplete encapsulation, with large Ni particles, contributing to Ni sintering and coking. The correlation of the synthesis-structure-performance in this study sheds light on the design of coking-/sintering-resistant encapsulated catalysts for DRM.
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Jun 2022
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B22-Multimode InfraRed imaging And Microspectroscopy
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Diamond Proposal Number(s):
[22476]
Open Access
Abstract: Systematic investigation was performed to understand the change of physiochemical properties in Y zeolite after the microwave (MW)-assisted dealumination (using mineral acid, HCl, and chelating agent, EDTA4−) and the subsequent alkaline treatment (of the dealuminated zeolites). The findings show that the combination of EDTA4− and hydrogen ions was effective to achieve dealumination of zeolite Y under MW irradiation, which formed complexed framework Al, instead of extra-framework Al (EFAl), to be extracted readily by the sequential alkaline treatment for mesopore formation. Conversely, under the same MW condition, the use of HCl encouraged the formation of EFAl species in the defective Y framework, which did not benefit the mesopore formation. The disclose of the distinct dealumination mechanisms of the MW-assisted method using different agents can benefit the further development of effective MW methods for dealumination of zeolites and/or making mesoporous zeolites.
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Feb 2022
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B18-Core EXAFS
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Diamond Proposal Number(s):
[15151]
Open Access
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.
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Oct 2021
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I20-EDE-Energy Dispersive EXAFS (EDE)
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Abstract: The use of X-ray absorption spectroscopy (XAS) to follow liquid phase catalysed reactions is widely used. However, in catalysis, small quantities of active species are usually present, complicating the differentiation of spectator and active species. In these cases, the use of Modulation Excitation (ME) techniques can be used to achieve a better signal-to-noise ratio by cycle averaging. ME coupled with phase-sensitive detection can significantly improve the sensitivity of the spectroscopic technique by filtering out contributions of spectator species that are unaltered by the external stimulation. This has been used in combined XAS/DRIFTS studies of gas phase reactions, successfully identifying surface intermediates present in small concentration. [1]
In this study, ME assisted by phase-sensitive detection analysis has been applied to the study of liquid-phase reactions using XAS. This methodology has been successfully applied to the study of the electrochemical oxidation of Na4FeII(CN)6. The experiment was undertaken in a newly three-electrode designed electrochemical cell at the I20-EDE beamline at Diamond Light Source. 30, 50, and 75 mM aqueous solutions of the iron complex in 1 M NaF/NaCl electrolytes were investigated. Cyclic voltammograms were measured during potential cycling with potential limits ± 1.5 V, at 200 and 300 mV/s scan rates, for 100 cycles. This perturbed the system reversibly allowing the cycle averaging of the XAS data.
This study shows that ME assisted by phase-sensitive detection analysis can be successfully applied to XAS for the study of liquid-phase reactions. Signal-to-noise ratios were improved significantly through cycle averaging, and additional information were extracted from the phase-resolved FT-EXAFS spectra demonstrating the enhanced sensitivity.
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Jul 2021
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