Nanocatalysis in Flow

Ricciardi, Roberto; Huskens, Jurriaan; Verboom, Willem

doi:10.1002/cssc.201500514

Cited by 61 publications

(39 citation statements)

References 178 publications

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“…In the flow nanocatalysis approach the advantages of both nanocatalysis and flow chemistry are exploited and boosted. [28][29][30] In our previous works we have presented the preparation, without any need of additional reducing and/or stabilizing agents, of a variety of stable silica-supported Au NPs by using different functionalized-silica supports and a chloroauric acid (HAuCl 4 ) aqueous solution as the only reactants. [31][32][33][34] We started using commercial polyethyleneimine-functionalized silica beads 30 and we went on preparing silica nanoparticles with alkynyl carbamate moieties synthetized by cocondensation of the di-functional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) with tetraethoxysilane (TEOS) in alkaline medium.…”

mentioning

confidence: 99%

Supported Gold Nanoparticles for Alcohols Oxidation in Continuous-Flow Heterogeneous Systems

Ballarin

Barreca

Boanini

et al. 2017

ACS Sustainable Chem. Eng.

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Gold nanoparticles (AuNPs) were anchored on alkynyl carbamate-functionalized support materials having the suitable features for application as catalysts in continuous-flow packed bed reactors. The functionalization step was carried out by grafting with the di-functional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) three commercial micrometer-sized oxide supports, i.e. silica, alumina, and titania. The alkynyl-carbamate moieties were capable to straightforwardly reduce the gold precursor HAuCl4 yielding the supported AuNPs systems Au/SiO2@Yne, Au/Al2O3@Yne, and Au/TiO2@Yne. A comparison among the three materials revealed that silica allowed the highest organic functionalization (12 wt%) as well as the highest gold loading (3.7 wt%). Moreover, TEM investigation showed only for Au/SiO2@Yne the presence of homogeneously distributed, spherically shaped AuNPs (av. diameter 15 nm). Au/SiO2@Yne is an efficient catalyst, both in batch and flow conditions, in the oxidation of a large variety of alcohols, using H2O2 as oxidizing agent, at a temperature of 90 °C. Furthermore, under flow conditions, the catalyst worked for over 50 h without any significant decrease in the catalytic activity. The catalytic activity of the three catalysts was evaluated and compared in the oxidation of 1-phenylethanol as a model substrate. We found that the flow approach plays a strategic role in preserving the physical and chemical integrity of the solid catalysts during its use, with remarkable consequences for the reaction conversion (from 2% in batch to 80 % in flow) in the case of Au/TiO2@Yne

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mentioning

confidence: 99%

Supported Gold Nanoparticles for Alcohols Oxidation in Continuous-Flow Heterogeneous Systems

Ballarin

Barreca

Boanini

et al. 2017

ACS Sustainable Chem. Eng.

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“…Nanocatalysis has found application in continuous‐flow technology in the so‐called flow nanocatalysis . The stability of both NPs and their anchoring to the microreactor is a critical issue that has been addressed by three classical approaches: i) packed beads with the catalyst tethered onto the bead, ii) monolithic columns with the catalyst in porous channels resulting from the copolymerization of the catalyst with other monomers inside the reactor, and iii) wall‐coated by which the catalyst is immobilized onto the inner walls of the reactor .…”

Section: Resultsmentioning

confidence: 99%

Catalytic Materials Based on Surface Coating with Poly(ethyleneimine)‐Stabilized Gold Nanoparticles

et al. 2017

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Gold nanoparticles (AuNPs) can be obtained from HAuCl4 by using poly(ethyleneimine) (PEI) as both reductant and stabilizing agent. However, the known affinity of PEI for different materials has not been exploited to coat them and turn their surface catalytic. We demonstrate that the irradiation of a solution of HAuCl4 and branched PEI 1800 (bPEI2K) with microwave (MW) yields PEI‐stabilized AuNPs (MW‐PEI@AuNPs) with an average size of 7.6 nm that are catalytically active in the reduction with NaBH4 of different nitroarenes functionalized with a variety of functional groups. Moreover, the as‐prepared MW‐PE@‐AuNPs show affinity for different materials such as polystyrene (standard spectrophotometry disposal cuvettes), polypropylene (Falcon‐type tubes), and silica (Silica gel 60), turning their surface catalytic without any additional synthetic step. This feature was exploited to transform standard tubing (Tygon, poly(ether ether ketone), and stainless steel) into flow reactors by simple passage of a solution of MW‐PEI@AuNPs. This straightforward functionalization is especially appealing in the case of the stainless‐steel tubing, one of the materials more widely used in HPLC, which is of interest for flow nanocatalysis.

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“…The presence of as low as 2wt% niobium resulted in the highest furfural yield at 140 8Cu nder continuous-flowc onditions, by using H 2 O/g-valerolactone as as afe monophasic solvent system.T he interception of at ransient 2,5-anhydroxylose species suggested the dehydration process occurs via ac yclic intermediates mechanism. [35,36] One reason for this is the hard to reproduce preparation of monoliths with 2-15 mm diameter to perform microsynthesis, [37,38] owing to the extreme structure sensitivity from the phase system composition. issues typicalo fp acked-bed systems, such as high backpressure evolution, low contacting efficiency,b road distribution of residence times, formation of hot-spots or stagnation zones, which result in uncontrolled fluid dynamics, hence in unsatisfactory performance.…”

Section: Introductionmentioning

confidence: 99%

“…[34] Despite their advantages, use of hierarchically porous inorganic monoliths in flow catalysis hasb een scarcely investigated so far,b eing essentially exploredf or HPLC applications. [35,36] One reason for this is the hard to reproduce preparation of monoliths with 2-15 mm diameter to perform microsynthesis, [37,38] owing to the extreme structure sensitivity from the phase system composition. [39] Specific functionalization of the monolithic material may also be required for catalytic applications.…”

Section: Introductionmentioning

confidence: 99%

Low‐Temperature Continuous‐Flow Dehydration of Xylose Over Water‐Tolerant Niobia–Titania Heterogeneous Catalysts

et al. 2018

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The sustainable conversion of vegetable biomass-derived feeds to useful chemicals requires innovative routes meeting environmental and economical criteria. The approach herein pursued is the synthesis of water-tolerant, unconventional solid acid monolithic catalysts based on a mixed niobia-titania skeleton building up a hierarchical open-cell network of meso- and macropores, and tailored for use under continuous-flow conditions. The materials were characterized by spectroscopic, microscopy, and diffraction techniques, showing a reproducible isotropic structure and an increasing Lewis/Brønsted acid sites ratio with increasing Nb content. The catalytic dehydration reaction of xylose to furfural was investigated as a representative application. The efficiency of the catalyst was found to be dramatically affected by the niobia content in the titania lattice. The presence of as low as 2 wt % niobium resulted in the highest furfural yield at 140 °C under continuous-flow conditions, by using H O/γ-valerolactone as a safe monophasic solvent system. The interception of a transient 2,5-anhydroxylose species suggested the dehydration process occurs via a cyclic intermediates mechanism. The catalytic activity and the formation of the anhydro intermediate were related to the Lewis acid sites (LAS)/Brønsted acid sites (BAS) ratio and indicated a significant contribution of xylose-xylulose isomerization. No significant catalyst deactivation was observed over 4 days usage.

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Nanocatalysis in Flow

Cited by 61 publications

References 178 publications

Supported Gold Nanoparticles for Alcohols Oxidation in Continuous-Flow Heterogeneous Systems

Supported Gold Nanoparticles for Alcohols Oxidation in Continuous-Flow Heterogeneous Systems

Catalytic Materials Based on Surface Coating with Poly(ethyleneimine)‐Stabilized Gold Nanoparticles

Low‐Temperature Continuous‐Flow Dehydration of Xylose Over Water‐Tolerant Niobia–Titania Heterogeneous Catalysts

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