Anna Wach

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.

Solvents effects on the fluorescence quenching of anthracene by iodide ions

Abstract Fluorescence quenching of anthracene by iodide ions in ethanol and propanol solutions in the temperature range 293–333 K was investigated under stationary conditions. The fluorescence quenching can be satisfactorily described using Marcus-type theory. Analysis of the experimental data indicates the importance of solvent-dielectric-relaxation properties for the fluorescence quenching.

Oxidative Dehydrogenation of Ethylbenzene Over Poly(furfuryl alcohol)-Derived CMK-1 Carbon Replica

Poly(furfuryl alcohol) was introduced into a pore system of MCM-48 silica by the precipitation polycondensation of furfuryl alcohol (FA). The complete filling of the pores without the deposition of significant amounts of polymer on the external surface of MCM-48 was obtained at the FA/MCM-48 mass ratio close to 1.0. The final structure of carbon replica was formed by subsequent carbonization and extraction of SiO2 with HF. The carbonization temperature strongly influenced the surface composition of the formed carbon replicas. The highest catalytic activity in the oxidative dehydrogenation of ethylbenzene was observed for CMK-1 with the highest concentration of phenol and carbonyl groups, recognized as active sites of the studied reaction.Graphical Abstract

Physicochemical properties of hydrogel template-synthesized copper(II) oxide-modified clay influencing its catalytic activity in toluene combustion

CuO-modified montmorillonite was synthesized by the template-assisted route. Poly(acrylic acid) was intercalated into the interlayer gallery of natural clay. Subsequently, various amounts of Cu2+ cations were introduced into the prepared hydrogel–clay composite using adsorption in different volumes of aqueous Cu(NO3)2 solution at constant pH = 6. The resulting materials were finally calcined at 550 °C (chosen using the results of TGA-IR analyses) to transform them into thermally stable oxide systems. The changes in the structural properties of the clay during the progressive modification were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Moreover, porosity, reducibility and surface composition of the calcined materials were determined by means of low-temperature N2 adsorption, temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). It was shown that a high concentration of CuO nanoparticles, which were well-dispersed and protected against sintering between montmorillonite grains, and weak interaction between CuO and the clay support (resulting in easy reducibility of CuO) were the most important features influencing the catalytic activity of the synthesized materials in the total oxidation of volatile organic compounds (VOCs).

First Steps on the Way to a Modular Concept for the Preparation of Carbon Based Catalysts

The preparation of carbon based catalysts following a modular concept has been investigated. A template assisted route was applied to obtain catalysts exhibiting different fractions of graphitic species while retaining their mesoporosity. The carbon materials were characterized by means of low temperature nitrogen adsorption, powder X-ray diffraction, thermogravimetry, X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectroscopy. The synthesized replicas were tested as catalysts in oxidative dehydrogenation of ethylbenzene and electrochemical oxygen reduction reaction. The role of the different carbon species, namely amorphous carbon, small graphitic crystallites, and large graphitic crystallites in the catalytic behavior was discussed.Graphical Abstract