Phase-transfer catalyst separation and re-use by solvent resistant nanofiltration membranes

Luthra, Satinder Singh; Yang, Xiaojin; Santos, L. M. Freitas dos; White, Lloyd S.; Livingston, Andrew G.

doi:10.1039/b103645a

Cited by 31 publications

(18 citation statements)

References 4 publications

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“…From the above two experiments, it is clear that Cu(II), Cl -and O2 are the active components of the etchant. It appears that the quaternary salts adsorbed on {111} facets of Au microcrystals (obtained from AuToABr) get removed during toluene washing due to the high solubility of the ToABr in toluene (380 g/L) [40], while Br -may remain intact on{100} facets due to poor solubility in toluene. Hence the {111} facets are easily accessible for the etchant which is devoid of the capping agent.…”

Section: Etching Of {111} Facetsmentioning

confidence: 99%

Facet selective etching of Au microcrystallites

Mettela

2015

Nano Res.

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Selectively, the {100} and {111} facets of Au microcrystallites are etched using a capping method. The specific etchants etch the facets that are free of capping agents and produce crystallites with well-defined corrugation involving high-index microfacets. Such facets exhibit enhanced Raman activity compared to smooth facets. Provide the authors' website if possible. ABSTRACTHigh symmetry crystals, by nature, exhibit isotropic properties. Inducing anisotropy for example by facet selective etching, is considered implausible in face centered cubic (FCC) metals, particularly in gold, which besides being FCC, is also noble. Here, for the first time, facet selective etching of Au microcrystals obtained in the form of cuboctahedrons and pentagonal rods from thermolysis of a gold-organic precursor is reported. The selective etching of {111} and {100} facets has been achieved via a capping method. In this method, tetraoctylammonium cations selectively cap the {111} facets, while Br -ions protect the {100} facets. The exposed facets are oxidized by O2/Cl -, producing a variety of interesting geometries. Facet selective etching of Au microcrystallites is governed only by the nature of the facets as geometry does not seem to play any significant role. Etched surfaces appear rough but a closer examination reveals well-defined corrugations indexable to high hkl values. Such surfaces exhibit enhanced Raman activity.

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Section: Etching Of {111} Facetsmentioning

confidence: 99%

Facet selective etching of Au microcrystallites

Mettela

2015

Nano Res.

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“…Most importantly, the concentrated solution can catalyze the reaction in fresh organic reactant solution directly without any further purification or treatment. 173,174 Compared with the recovery of phase transfer catalysts, SRNF should be more suitable to recover homogeneous catalysts, especially transition metal catalysts. [175][176][177][178][179][180][181][182][183] Schoeps et al 178 developed a type of PDMS SRNF membrane on a PAN porous support and thermally cross-linked the membranes.…”

Section: Recovery Of Catalystsmentioning

confidence: 99%

“…Sheth et al 165 claimed that precompacting commercial MPF-50 or MPF-60 with used solvents at operational pressures and temperatures is necessary to remove erythromycin because precompaction increased the rejection of erythromycin by SRNF membranes, which reduced the loss of erythromycin and increased the purification efficiency. Shi et al 166 fabricated a type of PI membrane to concentrate spiramycin 220 (n-alkanes in toluene) [168][169][170][171][173][174][175]180,182,184,[190][191][192]195,197 Starmem TM 228 280 (n-alkanes in toluene) 169,179,184,196 Starmem TM 240 400 (n-alkanes in toluene) [171][172][173][174][175]180,182,184,185,189,196,197 Puramem TM extracts and recover the used solvent (butyl acetate). They indicated that the permeability of the spiramycin solution was significantly affected by the operating conditions, although the rejection of spiramycin (higher than 99%) was not influenced.…”

Section: Pharmaceutical Applicationsmentioning

confidence: 99%

“…124,[161][162][163][164] Most recently, the separation and purification of active molecules in organic medium by NF membranes (called SRNF membranes) has attracted significant attention because unlike conventional distillation, this process is athermal. The SRNF membranes can potentially be used in the pharmaceutical manufacturing industry, [165][166][167][168][169][170][171][172][198][199][200] catalysis recovery processes, [173][174][175][176][177][178][179][180][181][182][183]196,197 the concentration of biologically active compounds in food technology, 192 the recovery of ion liquids, [184][185][186] the purification of fuels and solvents, 188,189 refining technologies, 187 and many other fields. 205 All of these fields have a common feature: the cost and the energy consumption to prepare or recover active molecules are very high, which makes the application of SRNF economically attractive.…”

Section: Advanced Applications Of Srnf Membranesmentioning

confidence: 99%

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Recent Advances in Polymeric Solvent‐Resistant Nanofiltration Membranes

et al. 2014

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When considering energy consumption and environmental issues, solvent-resistant nanofiltration (SRNF) based on polymeric materials emerges as a process for substituting conventional separation processes of organic solutions, such as distillation, which consume high amounts of energy. Because SRNF does not involve phase transition, this process can potentially decrease the energy consumption and solvent waste and increase the yield of active components. Such improvements could significantly benefit a number of fields, such as pharmaceutical manufacturing and catalysis recovery, among others. Therefore, SRNF has gained a lot of attention since the recent introduction of solvent-stable polymeric materials in the manufacture of nanofiltration membranes. The membrane materials and the membrane structures depending on the fabrication methods determine the separation performance of polymeric SRNF membranes. Therefore, this article gives a comprehensive overview of the current state-of-art technologies of generating membrane materials and corresponding fabrication methods for SRNF membranes made from polymeric materials expected to provide the most benefit. The transport mechanisms and the corresponding models of SRNF membranes in organic media are also reviewed to better understand the mass transfer process. Various SRNF applications, such as in pharmaceutical and catalyst, among others, are also discussed. Finally, the difficulties and future research directions to overcome the challenges faced by SRNF processes are proposed. C

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“…The PTC remains in the retentate phase and is recycled to the next reaction. More detailed accounts of this technique can be found elsewhere 17,18…”

Section: Homogeneous Catalyst Recyclementioning

confidence: 99%

Membrane Separation in Green Chemical Processing

Livingston

Peeva

Han

et al. 2003

Annals of the New York Academy of Sciences

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This paper describes ideas together with preliminary experimental results for applying solvent nanofiltration to liquid phase organic synthesis reactions. Membranes for organic solvent nanofiltration have only recently (during the 1990s) become available and, to date, have been applied primarily to food processing (vegetable oil processing, in particular) and refinery processes. Applications to organic synthesis, even at a laboratory feasibility level, are few. However, these membranes have great potential to improve the environmental performance of many liquid phase synthesis reactions by reducing the need for complex solvent handling operations. Examples that are shown to be feasible are solvent exchanges, where it is desired to swap a high molecular weight molecule from one solvent to another between separate stages in a complex synthesis, and recycle and reuse of homogeneous catalysts. In solvent exchanges, nanofiltration is shown to provide a fast and effective means of swapping from a high boiling point solvent to a solvent with a lower boiling point—this is a difficult operation by means of distillation. Solvent nanofiltration is shown to be able to separate two distinct types of homogeneous catalysts, phase transfer catalysts and organometallic catalysts, from their respective reaction products. In both cases the application of organic solvent nanofiltration allows several reuses of the same catalyst. Catalyst stability is shown to be an essential requirement for this technique to be effective. Finally, we present a discussion of scale‐up aspects including membrane flux and process economics.

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Phase-transfer catalyst separation and re-use by solvent resistant nanofiltration membranes

Cited by 31 publications

References 4 publications

Facet selective etching of Au microcrystallites

Facet selective etching of Au microcrystallites

Recent Advances in Polymeric Solvent‐Resistant Nanofiltration Membranes

Membrane Separation in Green Chemical Processing

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