Sebastian Wohlrab

Preparation of BaTiO3 nanocrystals using a two-phase solvothermal method

A two-phase solvothermal synthesis approach for the preparation of hydrophobic BaTiO3 nanocrystals is reported. Three organic solvents, hexadecene, toluene, and heptane were used as the oil phase and compared to each other with respect to the product quality. The BaTiO3 particles are crystalline with a mean size of 3.7 nm and can be dispersed in a variety of organic solvents forming highly transparent dispersions. X-Ray diffraction patterns indicate the presence of the cubic phase even after calcination at 800 °C. Transparent polymer nanocomposites (T > 80%) are obtained from the hydrophobic BaTiO3 nanocrystals (1–3 wt%) and lauryl acrylate.

Methane conversion into different hydrocarbons or oxygenates: current status and future perspectives in catalyst development and reactor operation

This Perspective highlights recent developments in methane conversion into different hydrocarbons and oxygenates (methanol, its derivatives, and formaldehyde) with the purpose to address the global demand for efficient and environmentally friendly production of these bulk chemicals. Our analysis identified possible directions for further research to bring the above approaches to a commercial level. As no progress in the development of catalysts for the oxidative coupling of methane could be identified, improvements are expected through reactor operation, cost- and energy-efficient methods for product separation and for providing pure oxygen. With respect to methane oxidation to methanol, further progress can also be achieved by proper catalyst design on the basis of fundamental knowledge especially gained from homogeneous and enzymatic catalysts as well as from theoretical calculations.

Synthesis of Single Atom Based Heterogeneous Platinum Catalysts: High Selectivity and Activity for Hydrosilylation Reactions

Catalytic hydrosilylation represents a straightforward and atom-efficient methodology for the creation of C–Si bonds. In general, the application of homogeneous platinum complexes prevails in industry and academia. Herein, we describe the first heterogeneous single atom catalysts (SACs), which are conveniently prepared by decorating alumina nanorods with platinum atoms. The resulting stable material efficiently catalyzes hydrosilylation of industrially relevant olefins with high TON (≈105). A variety of substrates is selectively hydrosilylated including compounds with sensitive reducible and other functional groups (N, B, F, Cl). The single atom based catalyst shows significantly higher activity compared to related Pt nanoparticles.

Crystal structure of (E)-pent-2-enoic acid.

The molecule of the title compound, C5H8O2, a low-melting α,β-unsaturated carboxylic acid, is essentially planar [maximum displacement = 0.0239 (13) Å]. In the crystal, molecules are linked into centrosymmetric dimers via pairs of O—H⋯O hydrogen bonds.

Crystal structure of (E)-hex-2-enoic acid.

The crystal structure of the title compound, C6H10O2, an α,β-unsaturated carboxylic acid, displays carboxylic acid inversion dimers linked by pairs of O—H⋯O hydrogen bonds. The packing is characterized by layers of acid dimers. All the non-H atoms of the (E)-hex-2-enoic acid molecule lie almost in the same plane (r.m.s. deviation for the non-H atoms = 0.018 Å).

Crystal structure of (E)-undec-2-enoic acid

In the molecule of the title low-melting α,β-unsaturated carboxylic acid, C11H20O2, the least-squares mean line through the octyl chain forms an angle of 60.10 (13)° with the normal to plane of the acrylic acid fragment (r.m.s. deviation = 0.008 Å). In the crystal, centrosymmetrically related molecules are linked by pairs of O—H⋯O hydrogen bonds into dimers, forming layers parallel to the (041) plane.

Foam-derived multiferroic BiFeO3 nanoparticles and integration into transparent polymer nanocomposites

Transparent BiFeO3/PMMA (PMMA = poly(methyl methacrylate)) nanocomposites with a thickness up to 40 µm are obtained via solution film casting of BiFeO3 nanoparticle dispersions. The multiferroic BiFeO3 nanoparticles are obtained in a space confined crystallisation process in a porous carbon matrix and subsequent removal of the matrix. The average crystallite size ranges from 46 nm to 106 nm for materials synthesised at 803 K and 903 K respectively, but, at higher temperature, significant amounts of side products are detected by means of X-ray powder diffraction. The nanoparticles are multiferroic with a magnetic coercivity of 1.88 A m−1 at 400 K and a polarisation of up to 1.04 µC/cm2 at 65 kV/cm (298 K). Surface functionalisation using oleic acid allows the integration into PMMA films with a high transmittance.

Crystal structure of (E)-dodec-2-enoic acid.

The crystal structure of (E)-dodec-2-enoic acid, C12H22O2, an α,β-unsaturated carboxylic acid with a melting point (295 K) near room temperature, is characterized by carboxylic acid inversion dimers linked by pairs of O—H⋯O hydrogen bonds. The carboxylic acid group and the following three carbon atoms of the chain of the (E)-dodec-2-enoic acid molecule lie almost in one plane (r.m.s. deviation for the four C atoms and two O atoms = 0.012 Å), whereas the remaining carbon atoms of the hydrocarbon chain adopt a nearly fully staggered conformation [moduli of torsion angles vary from 174.01 (13) to 179.97 (13)°].

Phosphate Functionalization of CeO2-ZrO2 Solid Solutions for the Catalytic Formation of Dimethyl Carbonate from Methanol and Carbon Dioxide

Phosphate surface groups on CeO2–ZrO2 solid solutions were generated by treating Ce–Zr–hydroxide precursors with phosphoric acid. In the catalytic formation of dimethyl carbonate (DMC) from methanol and CO2, the performance of the P‐modified samples was markedly affected relative to that of the unmodified ones: Phosphate treatment caused remarkable changes in the phase composition, acid–base properties, and the ability to form monodentate methoxy intermediates. The DMC yield (1.6 %) was successfully improved from 0.24 to 1.6 % by phosphate modification of CeO2–ZrO2 (Ce/Zr=4.7, P/Zr=0.13) and by performing the reaction at 170 °C and 6.5 MPa for 1 h.