Scalable fractionation of iron oxide nanoparticles using a CO2 gas-expanded liquid system

Vengsarkar, Pranav S.; Xu, Rui; Roberts, Christopher B.

doi:10.1007/s11051-015-3196-x

Cited by 4 publications

(3 citation statements)

References 60 publications

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“…36 In the GXL fractionation process, we exploit this reduction in solubility to controllably precipitate nanoparticles of progressively smaller size from solution using increasing amounts of applied CO 2 pressure. The nanoparticles used in this process are usually coated with an aliphatic ligand (e.g., dodecanethiol 31 or oleic acid 38 ) for dispersion in an organic solvent and to ensure that they do not aggregate after precipitation. 33 The CO 2 , which dissolves into the solvent upon applied CO 2 pressure, is an antisolvent for these stabilizing ligands causing these ligands to collapse 39 and induce the precipitation of the particles attached to them.…”

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confidence: 99%

Deposition of Iron Oxide Nanoparticles onto an Oxidic Support Using a Novel Gas-Expanded Liquid Process to Produce Functional Fischer–Tropsch Synthesis Catalysts

Vengsarkar

Roberts

2015

Ind. Eng. Chem. Res.

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Gas expanded liquids (GXL) are solvent systems which enable the controlled deposition of presynthesized iron oxide nanoparticles, based on their size, onto a surface through the use of compressible gas such as CO 2 . By controlling the applied CO 2 pressure, and hence the solvent strength, one can systematically deposit/precipitate nanoparticles of desired sizes. In this study, a technique using a GXL has been developed to controllably deposit iron oxide nanoparticles onto oxidic materials such as alumina and silica. The nanomaterials generated using this technique were then tested for their effectiveness as catalysts in Fischer−Tropsch (FT) synthesis in a fixed bed reactor system under standard low temperature FT conditions. The catalytic performance of these nanoscale iron FT catalysts was compared to control catalysts that were prepared by traditional incipient wetness methods using the same iron loading. Characterization of these GXL-synthesized materials demonstrated that the iron oxide nanoparticles were deposited in a size controlled manner onto the oxidic support. A CO conversion of 18% was observed using a silica catalyst generated using this GXL technique along with a 69% selectivity toward C 5+ hydrocarbons. The nanoscale iron catalysts prepared by the GXL technique employed in this study exhibit weaker interactions between the iron oxide nanoparticles and the support material, offering a new strategy to investigate the effect of metal−support interaction on the activity and selectivity of iron based FT synthesis catalysts.

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Deposition of Iron Oxide Nanoparticles onto an Oxidic Support Using a Novel Gas-Expanded Liquid Process to Produce Functional Fischer–Tropsch Synthesis Catalysts

Vengsarkar

Roberts

2015

Ind. Eng. Chem. Res.

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“…The procedure for synthesizing iron oxide nanoparticles has been reported previously. 10 Briefly, two solutions of iron chloride (Fe 2+ and Fe 3+ ) were synthesized with concentrations formulated to achieve the desired amount (wt %) of iron to later be deposited onto the SiO 2 support. These solutions were then mixed in a three-necked flask.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Fischer–Tropsch Synthesis Performance of Supported Nano-Iron Catalysts Synthesized By a Gas-Expanded Liquid Deposition Technique

Vengsarkar

Roe

et al. 2017

Energy Fuels

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A gas-expanded-liquid technique (GXL) was applied to the preparation of supported iron catalysts for Fischer− Tropsch synthesis (FTS). A mixture of presynthesized iron oxide nanoparticles with an average size of 12 nm was deposited onto a SiO 2 support in a manner such that nanoparticles smaller than 5 nm were excluded from the final catalyst product. A series of SiO 2 -supported iron oxide nanoparticle catalysts were prepared with iron loadings of 11.4, 18.0, 24.0, and 28.8 wt %. Catalysts were characterized by nitrogen adsorption, inductively coupled plasma optical emission spectrometry, H 2 temperatureprogrammed reduction (H 2 -TPR), X-ray diffraction (XRD), trasmission electron microsopy (TEM), X-ray photoelectron spectroscopy, and carbon monoxide temperature-programmed desorption. TEM analysis showed that iron oxide nanoparticles were well-distributed over the surface of the SiO 2 support with an increase in the iron loading resulting in the formation of multilayers and three-dimensional islands of iron oxide nanoparticles. H 2 -TPR indicated that the reducibility of the iron oxide nanoparticles increased monotonically with iron loading. According to XRD results, the increase in the iron loading resulted in an increase in the iron oxide crystallite size, and iron carbides were present in the used catalysts after solvent treatment. FTS was carried out in a fixed-bed reactor at reaction conditions of 230 °C, 2 MPa, H 2 /CO = 1.70, and GHSV = 3000 L/kg cat /h. For the catalysts studied, the highest syngas conversion and iron time yield were observed at intermediate (18, 24 wt %) iron loadings. The C 5+ selectivity and carbon chain growth probability factor were approximately 68% and 0.76, respectively, for each catalyst. A 16 wt % iron on SiO 2 catalyst prepared by the same GXL technique was promoted with 0.7 wt % potassium using the incipient wetness method. As expected, K promotion resulted in a slight decrease in FTS activity and increased selectivity toward CO 2 and C 5+ selectivity.

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“…CXL system was reported effective at separating large volumes of concentrated nanoparticle solutions. Large quantities of iron oxide nanoparticles were successfully fractionated in CXL media based upon particle size [7] . By adjusting the parameters of CO 2 expanded hexane, colloidal nanoparticles of controlled size can be embedded in ordered mesoporous silica for high-load recyclable catalysis [8] .…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic cavitation in CO2-expanded N, N-dimethylformamide (DMF)

Gao

Pei

Dong

et al. 2021

Ultrasonics Sonochemistry

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Highlights Ultrasonic cavitation is recorded by high-speed camera and hydrophone in a gas-expanded liquid system. Content of CO 2 has an important influence on evolution of bubble cloud. Cavitation intensity depends on ultrasonic power and gas content. The combination of ultrasound and gas-expanded liquid system greatly promotes mass transfer.

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Scalable fractionation of iron oxide nanoparticles using a CO2 gas-expanded liquid system

Cited by 4 publications

References 60 publications

Deposition of Iron Oxide Nanoparticles onto an Oxidic Support Using a Novel Gas-Expanded Liquid Process to Produce Functional Fischer–Tropsch Synthesis Catalysts

Deposition of Iron Oxide Nanoparticles onto an Oxidic Support Using a Novel Gas-Expanded Liquid Process to Produce Functional Fischer–Tropsch Synthesis Catalysts

Fischer–Tropsch Synthesis Performance of Supported Nano-Iron Catalysts Synthesized By a Gas-Expanded Liquid Deposition Technique

Ultrasonic cavitation in CO2-expanded N, N-dimethylformamide (DMF)

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