Dorota Majda

Preparation and characterization of new Mg–Al–Fe oxide catalyst precursors for dehydrogenation of ethylbenzene in the presence of carbon dioxide

Abstract New catalysts based on hydrotalcite-like precursors (Mg–Fe and Mg–Al–Fe) were synthesized. The structure of catalyst precursors was confirmed by XRD, FT–IR and TG. Appearance of separate brucite phase was observed for Mg–Fe precursors with excess of Mg, while for Mg–Al–Fe precursors, increase in Al content led to a formation of MgAl 2 (OH) 8 and mixed Al–Fe hydroxides apart from hydrotalcite phase. During calcination, the hydrotalcite like precursors spread their surface area and transform into mixed oxide. The mixed oxides were applied in ethylbenzene (EB) dehydrogenation with CO 2 . The activity losses with time-on-stream were completely restored by oxygen pulses.

Synthesis, thermal and electrical properties of Li1+δMn2−δO4 prepared by a sol–gel method

Abstract The Li 1+ δ Mn 2− δ O 4 samples (0.00≤ δ ≤0.20) were obtained by a sol–gel method and characterized using: chemical analyses, XRD, SEM, TGA, DSC, electric conductivity and thermoelectric power. The obtained results were discussed in relation to the calcination temperature, and to the results obtained on commercial LiMn 2 O 4 . The samples calcined at 300 °C (S-samples) consisting small excess of Li ( δ ≤0.04) showed no phase transition at 285 K and no disturbance in electric conductivity and thermoelectric power, as observed for the related samples calcined at 800 °C (H-samples). Partial thermal decomposition of the S-samples or oxygen uptake by the H-samples were observed during TGA experiments above 350 °C. The beginning of the thermal decomposition of the H-samples started at higher temperatures, depending on Li-contents. At about 920 °C, the rapid acceleration took place independently on type of the samples. The thermal decomposition up to 800 °C seems to be reversible, owing to the samples reoxidation.

Water thermoporosimetry as a tool of characterization of the textural parameters of mesoporous materials

Water thermoporosimetry (TPM) is a powerful method for studying the properties of porous materials, devoted especially for investigation of the samples that can be destroyed in drying process. However, this method is not very popular and relatively rarely used because of problems with proper measurement procedure and choosing correct equation for the result interpretation. This report focused on refinement of general experimental protocols for water TPM. For the first time, the role of various parameters on the TPM outcomes was deeply investigated and simple and fast experimental mode was proposed. Additionally, based on the series of mesoporous silica SBA-15, the calibration procedure was employed and the reliable calibration equations were established.

Physicochemical Properties of Bosentan and Selected PDE-5 Inhibitors in the Design of Drugs for Rare Diseases.

The study provides the physicochemical characteristic of bosentan (BOS) in comparison to tadalafil (TA) and sildenafil citrate (SIL). Despite some reports dealing with thermal characteristic of SIL and TA, physicochemical properties of BOS have not been investigated so far. Recent clinical reports have indicated that the combination of bosentan and PDE-5 inhibitor can improve the effectiveness of pharmacotherapy of pulmonary arterial hypertension (PAH). However, in order to design personalized medicines for therapy of chronic rare diseases, detailed information on the thermal behaviour and solubility of each drug is indispensable. Thus, XRD, DSC and TGA-QMS analyses were applied to compare the properties of the drugs, their thermal stability as well as to identify the products of thermal degradation. The dehydration of BOS started at 70°C and was followed by the chemical degradation with the onset at 290°C. The highest thermal stability was stated for TA, which decomposed at ca. 320°C, whereas the lowest onset of the thermal decomposition process was stated for SIL, i.e. 190°C. The products of the drug decomposition were identified. FT-FIR was applied to study intra- and intermolecular interactions between the drug molecules. FT-MIR and Raman spectroscopy were used to examine the chemical structure of the drugs. Chemoinformatic tools were used to predict the polar surface area, pKa, or logP of the drugs. Their results were in line with solubility and dissolution studies.

Dynamics in ferro- and antiferroelectric phases of a liquid crystal with fluorinated molecules as studied by dielectric spectroscopy

For 1-[3-fluoro-4-(1-methylheptyloxycarbonyl)phenyl]-2-[4-2,2,3,3,4,4,4-heptafluorobutoxybutoxy)biphenyl-4-yl]ethane (1F7), built of chiral molecules, results of dielectric measurements of liquid-crystalline and solid phases are presented. Rich polymorphism of liquid-crystalline (SmC*, SmC*A and SmI*A) phases as well as of solid (Cr1 and Cr2) phases were observed down to –130°C. At a frequency range from 0.1 Hz to 3 MHz, the relaxation processes were detected in ferroelectric SmC*, antiferroelectric SmC*A and highly ordered SmI*A smectic phases. The mechanism of complex dynamics (moleculear and collective) was identified with the help of the bias field. Vitrification of conformationally disordered crystal phase Cr2 was found in accordance with calorimetric observations.

Potassium Ferrites Formation in Promoted Hematite Catalysts for Dehydrogenation. Thermal and structural analyses

K-promoted hematite catalysts for ethylbenzene dehydrogenation were studied by thermal analysis (TG/DTG) and high-temperature XRD. The formation of potassium ferrite (K2Fe2O4), considered to be a catalytically active phase, was observed during calcination of the Ce-promoted catalysts. A linear correlation of the catalytic activity and the temperature of potassium ferrites formation was found.

Effect of electrolyte composition on thermal stability and electrochemical performance of LiMn2O4-ySy cathodes for Li-ion batteries

Electrolytes are indispensable for the proper operation of every battery technology. Hence, in this paper, our major focus concerns identification of the most appropriate electrolyte composition in order to minimise the reactions on the electrode surface as well as enhance the electrochemical performance of Li-ion batteries containing as a cathode LiMn2O4-ySy (LMOS) spinel materials. For this purpose, thermal stability of LiPF6 and LiClO4 salts in a mixture of EC:DEC, TMS:EMC solvents towards LMOS cathode materials was investigated. All the electrolyte solutions were also tested in Li/Li+/LMOS cells. The electrochemical behaviour of electrolyte-cathode material systems was further examined by the electrochemical impedance spectroscopy. As demonstrated, LiMn2O3.99S0.01 (LMOS1) electrode exhibits remarkable thermal and electrochemical stability in LiPF6 solution of alkyl carbonates (EC:DEC). The satisfactory cycling performance is due to the development of highly stable passivating surface film on the LMOS1 cathode in aforementioned electrolyte that protects the active material from unfavourable reactions.

New, thermally stable, rigid polyurethane foams based on polyols obtained using morpholine-2,3-dione derivatives:

In this work, the research results of the synthesis and properties of the polyols with the oxamidoester group, obtained in the reaction of N-substituted morpholine-2,3-dione derivatives with excess of alkylene carbonates have been presented. Using these derivatives as polyol components, rigid foamed polyurethane materials of high thermal stability and mechanical strength have been obtained. New polyurethane foams obtained using hydroxypropyl morpholine-2,3-dione derivatives can be used as heat-insulating materials of operating temperature as high as 150°C.

Leak testing of carbon–tin nanocomposites by thermal analysis methods

Electrode materials consisted of tin nanograins encapsulated in different origin carbon buffer matrix (starch or water soluble polymer) were obtained in a simple and inexpensive process. The tin precursor was synthesized using modified reverse nanoemulsion technique (w/o) and then coated by a source of carbon. The composites precursors were pyrolysed, affording formation of C/Sn anode materials. The resulting samples were investigated by powder X-ray diffraction studies in order to verify the structure and calculate crystallites sizes. The morphology of the nanocomposites was characterized by low-temperature nitrogen adsorption method (N2-BET). Thermal analysis measurements (EGA-TG/DTG/DTA and DSC) allowed determining optimal conditions of preparation process and estimating carbon content in the obtained anode materials. Thermogravimetric studies also proved to be highly useful in establishing the leak behaviour of C/Sn nanocomposites. The electrochemical performance of the nanopowders was examined by charge–discharge tests in R2032-type coin cell. The thermal analysis results as well as low-temperature nitrogen adsorption data indicated that the origin of carbon precursor has major impact on morphology and leak behaviour of the obtained carbon buffer matrix. The electrochemical tests showed that better tightness of carbon–tin nanocomposites resulted in higher gravimetric capacity and better cell performance.

Study on Stability and Electrochemical Properties of Nano-LiMn1.9Ni0.1O3.99S0.01-Based Li-Ion Batteries with Liquid Electrolyte Containing LiPF6

Herein, we report on the stability and electrochemical properties of nanosized Ni and S doped lithium manganese oxide spinel LiMn1.9Ni0.1O3.99S0.01, LMN1OS in relation to the most commonly used electrolyte solution containing LiPF6 salt. The influence of electrochemical reaction in the presence of selected electrolyte on the LMN1OS electrode chemistry was examined. The changes in the structure, surface morphology, and composition of the LMN1OS cathode after 30 cycles of galvanostatic charging/discharging were determined. In addition, thermal stability and reactivity of the LMN1OS material towards the electrolyte system were verified. Performed studies revealed that no degradative effects, resulting from the interaction between the spinel electrode and liquid electrolyte, occur during electrochemical cycling. The LMN1OS electrode versus LiPF6-based electrolyte has been indicated as an efficient and electrochemically stable system, exhibiting high capacity, good rate capability, and excellent coulombic efficiency. The improved stability and electrochemical performance of the LMN1OS cathode material originate from the synergetic substitution of LiMn2O4 spinel with Ni and S.