Tuning component enrichment in amino acid functionalized (organo)silicas

A straightforward procedure to synthesize cysteine functionalized materials with tailored support properties has been developed. It allows tuning the hydrophobicity of the material via the incorporation of aliphatics, aromatics or silica in the framework structure. The aldol condensation of 4-nitrobenzaldehyde and acetone, as a probe reaction for the catalytic activity of the produced materials, exhibited a remarkable interplay between the reactant, solvent, traces of water and support hydrophobicity. A selective enrichment in the catalyst pores of specific bulk phase molecules is believed to be the key to achieve the targeted catalyst performance

Thermal transformation of polyacrylonitrile deposited on SBA-15 type silica : effect on adsorption capacity of methyl-ethyl ketone vapor

Thermogravimetry, diffuse reflectance infrared Fourier transform spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used for the studying of ther- mally induced structural changes of polyacrylonitrile (PAN) deposited on the surface of SBA-15 type meso- porous silica. Polymer was introduced onto the support by the precipitation polymerization of acrylonitrile in aqueous suspension of SBA-15. Low temperature transformation (to 723 K) of the deposited PAN was analyzed. It was found that at about 523 K, exothermic cyclization of polymer chains to the so-called ladder form of PAN occurred. However, the total cyclization of PAN required higher carbonization temperatures, at which gradual dehydroge- nation followed by graphitization was initiated. XPS revealed that the cyclic form of PAN and a relatively large amount of carbonyl species, formed during the carboniza- tion of the PAN/SBA-15 composite at 623 K, were responsible for the high sorption capacity in the methyl– ethyl ketone (MEK) vapor elimination. The efficiency in the MEK adsorption was also influenced by the content of PAN-derived carbon deposited on the SBA-15 surfac

Investigation on the Low-Temperature Transformations of Poly(furfuryl alcohol) Deposited on MCM-41

MCM-41-type mesoporous silica was used as a support for poly(furfuryl alcohol) deposition. This material was produced by precipitation–polycondensation of furfuryl alcohol (FA) in aqueous slurry of the SiO2 support followed by controlled partial carbonization. By tuning the FA/MCM-41 mass ratio in the reaction mixture, various amounts of polymer particles were introduced on the inner and outer surface of the MCM support. The thermal decomposition of the PFA/MCM-41 composites was studied by thermogravimetry (TG) and spectroscopic techniques (DRIFT, XPS), whereas the evolution of textural parameters with increasing polymer content was investigated using low-temperature adsorption of nitrogen. The mechanism of thermal transformations of PFA deposited on the MCM-41 surface was discussed in detail. It was found that heating at a temperature of about 523 K resulted in opening of the furan rings and the formation of γ-diketone moieties, which were found to be the highest effective surface species for the adsorption of polar volatile organic compounds. A further increase in calcination temperature caused a drop in the amounts of surface carbonyls and the appearance of condensed aromatic domains.This work was supported by the Polish Ministry of Science and Higher Education under Grant N N507 553238. Rafał Janus thanks the Foundation for Polish Science MPD Programme cofinanced by the EU European Regional Development Fund for the financial support. The research was carried out with equipment purchased thanks to financial help from the European Regional Development Fund within the framework of the Polish Innovation Economy Operational Program (Contract POIG.02.01.00-12-023/08)

SBA-15 mesoporous silica modified with rhodium by MDD method and its catalytic role for N2ON_2O decomposition reaction

SBA-15 mesoporous silicas modified with rhodium were studied as catalysts for the N2O decomposition reaction. Rhodium was deposited on SBA-15 by the Molecular Designed Dispersion (MDD) method using Rh(acac)3 as a precursor of active phase. The same method was used for the deposition of Cu, Fe, Al and Ti. The SBA-15 support modified with metals were characterized with respect to metal loading (EPMA), structure (XRD), texture (BET), morphology (SEM), Rh dispersion (oxygen chemisorption), surface acidity (pyridine adsorption) and chemical nature of introduced copper and iron species (UV-vis-DRS). The rhodium-containing SBA-15 samples were found to be active catalysts for the N2O decomposition reaction. Deposition of Al on the Rh-loaded catalyst increased its activity. An opposite effect was observed for the samples modified with Cu and Fe

Pore REconstruction and Segmentation (PORES) method for improved porosity quantification of nanoporous materials

Electron tomography is currently a versatile tool to investigate the connection between the structure and properties of nanomaterials. However, a quantitative interpretation of electron tomography results is still far from straightforward. Especially accurate quantification of pore-space is hampered by artifacts introduced in all steps of the processing chain, i.e., acquisition, reconstruction, segmentation and quantification. Furthermore, most common approaches require subjective manual user input. In this paper, the PORES algorithm “POre REconstruction and Segmentation” is introduced; it is a tailor-made, integral approach, for the reconstruction, segmentation, and quantification of porous nanomaterials. The PORES processing chain starts by calculating a reconstruction with a nanoporous-specific reconstruction algorithm: the Simultaneous Update of Pore Pixels by iterative REconstruction and Simple Segmentation algorithm (SUPPRESS). It classifies the interior region to the pores during reconstruction, while reconstructing the remaining region by reducing the error with respect to the acquired electron microscopy data. The SUPPRESS reconstruction can be directly plugged into the remaining processing chain of the PORES algorithm, resulting in accurate individual pore quantification and full sample pore statistics. The proposed approach was extensively validated on both simulated and experimental data, indicating its ability to generate accurate statistics of nanoporous materials

Efficient degradation and mineralization of diclofenac in water on ZnMe (Me: Al; Co; Ga) layered double hydroxides and derived mixed oxides as novel photocatalysts

The removal of diclofenac (DCF) from aqueous solutions was attempted using photocatalytic processes, involving a series of novel photocatalysts based on ZnMe (Me: Al; Co; Ga) layered double hydroxides (LDHs) and their derived mixed oxides. The catalysts were characterized using specific techniques. Under solar light, ZnCo and ZnGa catalysts degraded almost completely DCF from water, while the mineralization, expressed by total organic carbon removal, reached $\sim$85%. The degradation mechanisms of DCF photolysis and photocatalytic degradation under solar and UV irradiation were investigated

Automated discrete electron tomography – Towards routine high-fidelity reconstruction of nanomaterials

Electron tomography is an essential imaging technique for the investigation of morphology and 3D structure of nanomaterials. This method, however, suffers from well-known missing wedge artifacts due to a restricted tilt range, which limits the objectiveness, repeatability and efficiency of quantitative structural analysis. Discrete tomography represents one of the promising reconstruction techniques for materials science, potentially capable of delivering higher fidelity reconstructions by exploiting the prior knowledge of the limited number of material compositions in a specimen. However, the application of discrete tomography to practical datasets remains a difficult task due to the underlying challenging mathematical problem. In practice, it is often hard to obtain consistent reconstructions from experimental datasets. In addition, numerous parameters need to be tuned manually, which can lead to bias and non-repeatability. In this paper, we present the application of a new iterative reconstruction technique, named TVR-DART, for discrete electron tomography. The technique is capable of consistently delivering reconstructions with significantly reduced missing wedge artifacts for a variety of challenging data and imaging conditions, and can automatically estimate its key parameters. We describe the principles of the technique and apply it to datasets from three different types of samples acquired under diverse imaging modes. By further reducing the available tilt range and number of projections, we show that the proposed technique can still produce consistent reconstructions with minimized missing wedge artifacts. This new development promises to provide the electron microscopy community with an easy-to-use and robust tool for high-fidelity 3D characterization of nanomaterials

SI methane hydrate confined in C8-grafted SBA-15: A highly efficient storage system enabling ultrafast methane loading and unloading

Confinement of water and methane in mesopores of hydrophobized SBA-15 is demonstrated to promote methane hydrate formation. In comparison to as-synthesized SBA-15, hydrophobization by C8 grafting accelerates the kinetics of methane storage in and delivery from the hydrate. C8 grafting density was determined at 0.5 groups nm-2 based on TGA and quantitative NMR spectroscopy. Multinuclear 1H-1H DQSQ and 1H-1H RFDR NMR provided spectroscopic evidence for the occurrence of C8 chains inside the mesopores of SBA-15, by showcasing close spatial proximity between the grafted C8 chains and pore-intruded water species. X-ray diffraction demonstrates formation of Structure I hydrate on SBA-15 C8. At 7.0 MPa and 248 K, the water-to-hydrate conversion on hydrophobized SBA-15 C8 reaches 96 pct. as compared to only 71 pct. on a pristine SBA-15 sample with comparable pore size, pore volume and surface area. The clathrate loading amounted to 14.8 g g-1. 2D correlation NMR spectroscopy (1H-13C CP-HETCOR, 1H-1H RFDR) reveals hydrate formation occurs within pores of SBA-15 C8 as well as in interparticle volumes. Following the initial crystallization of SBA-15 C8-supported methane hydrate taking several hours, a pressure swing process at 248 K allows to desorb and re-adsorb methane from the structure within minutes and without thawing the frozen water structure. Fast loading and unloading of methane was achieved in 19 subsequent cycles without losses in kinetics. The ability to harvest the gas and regenerate the structure without the need to re-freeze the water represents a 50 pct. energy gain with respect to melting and subsequently recrystallizing the hydrate at 298 K and 248 K, respectively. After methane desorption, a small amount of residual methane hydrate in combination with an amorphous yet locally ordered ice phase is observed using 13C and 2H NMR spectroscopy