The implementation of the hydroformylation reaction for the conversion of long-chain alkenes into aldehydes still remains challenging on an industrial scale. One possible approach to overcoming this challenge is to apply tunable systems employing surfactants. Therefore, a novel process concept for the hydroformylation of long-chain alkenes to aldehydes in microemulsions is being investigated and developed at Technische Universität Berlin, Germany. To test the applicability of this concept for the hydroformylation in microemulsions on a larger scale, a miniplant has been constructed and operated. This contribution presents the proof of concept for hydroformylation in microemulsions carried out during a 200 h miniplant operation. Throughout the operation a stable aldehyde yield of 21% and a catalyst loss in the product phase below 0.1 ppm were achieved, which confirms previous lab scale findings. Additionally, solution strategies for a stable continuous operation to overcome challenges such as foaming, phase separation issues, and coalescence dynamics are discussed herein.
Nowadays, the development of chemical processes using environmentally friendly solvents is of high importance. As an alternative to conventional reaction media based on organic solvents, we show a novel aqueous surfactant-based process concept which is used for the three step synthesis of the fungicide Boscalid®. By applying three phase microemulsion systems for the Suzuki coupling reaction, the first step within the Boscalid® synthesis, a simple product and catalyst separation can be achieved, whereby the water-soluble homogeneous Pd/SPhos catalyst complex can be reused several times.Together with an easily recyclable heterogeneous PtIr@TiO 2 catalyst, which is applied for the hydrogenation reaction in the second step, followed by base-assisted condensation to the final product Boscalid® in the third step, overall yields up to 90% are achievable for the whole reaction sequence. This result was obtained without any purification step in between that requires the use of further solvents. In this way the total synthesis costs can be reduced and solvent wastage can be avoided.
The application of microemulsion systems as switchable reaction media for the rhodium-catalyzed hydroformylation of 1dodecene is being reported. The influence of temperature, phase behavior, and the selected nonionic surfactant on the reaction has been investigated. The results revealed that the structure and the hydrophilicity (degree of ethoxylation) of the applied surfactant can have a strong impact on the performance of the catalytic reaction in microemulsion systems, in particular on the reaction rate. The surfactant determines the boundary conditions for catalysis (interfacial area, local concentrations) and can also interact with the catalyst at the oil−water interface and hinder the reaction. In addition to the discussion of the experimental results, we present a proposal for the impact of surfactantbased reaction media on the reaction mechanism of the catalyst reaction.
Electron capture dissociation (ECD) has recently been shown in some cases to produce abundant N-terminal b-ion peptide fragments. These product ions are usually only observed when activation occurs via vibrational excitation as in collision-induced dissociation (CID). Here, we show that occurrence of b-ions in the ECD spectra of synthetic peptides are correlated with low gas-phase basicity and that the observed b-ion fragments are N-terminal products. Furthermore, all ECD spectra containing b-ions also had abundant losses of hydrogen and ammonia from the charge-reduced species.
Emulsions stabilized by solid particles are so called Pickering emulsions which are characterized by their high stability against coalescence. This type of emulsion can be used for a lot of applications. Very little is known about how reaction conditions affect their properties. In this study the influence of important reaction conditions like shear stress, pressure, temperature, and the influence of synthesis gas on Pickering emulsions is investigated. It is shown that the emulsions remain stable in terms of coalescence in a broad range of the reaction conditions and are suitable as reaction media for industrial processes and for a reaction optimization with a subsequent separation step.
For the first time, a significant boost in catalytic activity in the rhodium-catalysed hydroformylation of an alkene by using a bidentate bis(N-heterocyclic silylene) ligand is reported. This is shown by the hydroformylation of styrene at 30 bar CO/H 2 pressure in the presence of [HRh(CO)(PPh 3 ) 3 ] with an excess of the ferrocenediyl-based bis-NHSi ligand 4, [({η 5 -C 5 H 4 {PhC(NtBu) 2 }Si}) 2 Fe], which results in superior catalytic activity, compared with the bidentate diphosphines DPPF (3a) and xantphos (3b). In contrast, the hydroformylation of styrene in the presence of [HRh(CO)(PPh 3 ) 3 ] with excesses of the monodentate NHSi ligands [{PhC(NtBu) 2 }SiNMe 2 ] (1) and [{C 2 H 2 (NtBu) 2 }Si:] (2) at 30 bar CO/H 2 pressure revealed consid-[a]
We demonstrate the controlled preparation of heteroepitaxial diamond nano-and microstructures on silicon wafer based iridium films as hosts for single color centers. Our approach uses electron beam lithography followed by reactive ion etching to pattern the carbon layer formed by bias enhanced nucleation on the iridium surface. In the subsequent chemical vapor deposition process, the patterned areas evolve into regular arrays of (001) oriented diamond nano-islands with diameters of < 500 nm and a height of ≈ 60 nm. In the islands, we identify single SiV color centers with narrow zero phonon lines down to 1 nm at room temperature.Color centers in diamond are being extensively investigated as stable, room temperature single photon emitters 1 simultaneously hosting highly controllable electronic spin systems. They are promising candidates for quantum information processing architectures (single photon sources and spin qubits) and as quantum sensors (e.g. for magnetic fields 2 and optical near fields 3 ). For all these applications, efficient collection of the fluorescence light emitted by color centers is crucial. The high refractive index of diamond (n = 2.4) here is an ambivalent property: on one hand, it renders light extraction from bulk material highly challenging due to total internal reflection; on the other hand, it enables controlling the emission properties of color centers using versatile diamond photonic structures like waveguides and nanocavities. 4 Recent work on color centers in diamond often uses top-down fabricated singlecrystal diamond nano/microstructures enabling efficient light collection. Top-down nanofabrication creates many photonic structures, e.g. nanopillars, in regular arrays in which color centers can be straightforwardly identified and (re-)addressed. 5 However, diamond nanofabrication requires sophisticated, non-standard procedures e.g. for plasma etching, that are challenging due to the chemical inertness of diamond. Avoiding diamond nanofabrication, 5 enhanced out-coupling of light is alternatively obtained using nanodiamonds (NDs) combined with non-diamond photonic structures. 4 However, color centers in NDs may suffer from unstable fluorescence and short spin coherence times. Random spatial placement and orientation of NDs, e.g. resulting from spin-coating deposition, renders identifying and re-addressing suitable color centers challenging. In this paper, we introduce an approach to unite the advantages of ND based systems and top-down fabrication of photonic structures i.e. controlled growth of regular arrays of heteroepitaxial diamond nano-and microstructures on iridium (Ir).In previous work, regular arrays of diamond nanostructures have been obtained by chemical vapor deposition (CVD) on diamond substrates through openings in a mask. 6-9 However, etching of the mask material in the CVD plasma led to the formation of high densities of color centers. 6,7 Thus, this method can so far not be considered as an approach capable of high purity diamond growth for single color center appl...
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