Anna Lind

Formation of hierarchically ordered silicas prepared by spray drying of nanosized spheres

We report on our strategy to synthesise defined arrangements of macro- and mesopores in one single material with spherical morphology using the spray drying technique. As starting materials, nano-sized silica spheres and colloidal suspensions were chosen. The intra-particle as well as inter-particle pore size was independently controlled which allowed to obtain materials with varied bimodal pore networks. The spherical agglomerates were characterised regarding their pore structural parameters and are potential adsorbents in liquid chromatographic separations.

In-situ flow MAS NMR and synchrotron PDF analyses of the local response of the Brønsted acidic site in SAPO-34 during hydration at elevated temperatures

In situ flow magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and synchrotron-based pair distribution function (PDF) analyses were applied to study waters interactions with the Brønsted acidic site and the surrounding framework in the SAPO-34 catalyst at temperatures up to 300 °C for NMR spectroscopy and 700 °C for PDF. 29 Si enrichment of the sample enabled detailed NMR spectroscopy investigations of the T-atom generating the Brønsted site. By NMR spectroscopy, we observed dehydration above 100 °C and a coalescence of Si peaks due to local framework adjustments. Towards 300 °C, the NMR spectroscopy data indicated highly mobile acidic protons. In situ total X-ray scattering measurements analyzed by PDF showed clear changes in the Al local environment in the 250-300 °C region, as the Al-O bond lengths showed a sudden change. This fell within the same temperature range as the increased Brønsted proton mobility. We suggest that the active site in this catalyst under industrial conditions comprises not only the Brønsted proton but also SiO4 . To the best of our knowledge, this is the first work proposing a structural model of a SAPO catalyst by atomic PDF analysis. The combination of synchrotron PDF analysis with in situ NMR spectroscopy is promising in revealing the dynamic features of a working catalyst.

Bioactive Glass (S53P4) and Mesoporous MCM-41-Type SiO2 Adjusting In Vitro Bioactivity of Porous PDLLA

SiO2-based bioceramics, MCM-41-type SiO 2 and the bioactive glass S53P4, in composites with poly(D,L)lactide were studied in the simulated body fluid. The parameters controlling ion dissolutions and calcium phosphate formation were studied a nd the data was used to create multicomposites with locally varying properties ( .g., CaP formation on the other side, uninhibited silica dissolution and possibility to drug release from the other side of com posite)

SAPO-37 microporous catalysts: revealing the structural transformations during template removal

Abstract We have studied the structural behavior of SAPO-37 during calcination using simultaneous in situ powder X-ray diffraction (PXRD) and mass spectroscopy (MS) in addition to ex situ thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A spike in the unit cell volume corresponding to template removal (tracked using the occupancy of the crystallographic sites in the SAPO-37 cages) is revealed from the XRD data and is strongly correlated with the DSC curve. The occupancy of the different template molecules in the faujasite (FAU) and sodalite (SOD) cages is strongly related to the two mass loss steps observed in the TGA data. The templates act as a physical stabilizing agent, not allowing any substantial unit cell response to temperature changes until they are removed. The FAU cages and SOD cages have different thermal response to the combustion of each template. The FAU cages are mainly responsible for the unit cell volume expansion observed after the template combustion. This expansion seems to be related with residual coke from template combustion. We could differentiate between the thermal response of oxygen and T-atoms. The T–O–T angle between two double 6-rings and a neighboring T–O–T linkage shared by SOD and FAU had different response to the thermal events. We were able to monitor the changes in the positions of oxygen and T-atoms during the removal of TPA+ and TMA+. Large changes to the framework structure at the point of template removal may have a significant effect on the long-term stability of the material in its activated form.

Spray drying of porous alumina support for Fischer-Tropsch catalysis

Abstract Porous alumina particles, that are to be used as support in Fischer-Tropsch catalysis, have been produced by spray drying of spherical alumina primary particles, where the material is formed by agglomeration of the primary particles. We have investigated the influence of both instrumental parameters, as well as the condition of the suspension of primary particles on the porosity, as well as the particle size and morphology of the materials. Some of the materials have also been impregnated with cobalt and rhenium by the incipient wetness method and tested in a fixed bed reactor.

Solubilization of benzene derivatives in silicate-surfactant systems

Abstract The solubilization of six polar benzene derivatives with different polar groups by a silicate-surfactant mesophase has been investigated. Depending on the nature of the polar group of the solubilizate a transition to the lamellar phase, a contraction or an increased ordering of the hexagonal phase was observed. The results are discussed in terms of a co-surfactant effect paralleled by competitive adsorption of the solubilizate to the silicate.