Semen E. Lapuk

Obtaining amorphous forms of drugs is one of the ways to increase bioavailability. This is especially important for active pharmaceutical ingredients belonging to class II and IV according to the biopharmaceutical classification. These compounds include the currently widely used fluoroquinolone antibiotics. They have low solubility in water and are therefore typically used as hydrochlorides. The presence of a strong acid and a charged active pharmaceutical ingredient in the drug increases solubility, but can also lead to additional side effects and decreased permeability. One way to improve the properties of active pharmaceutical ingredients is to convert them to amorphous form. In this study, an amorphous form of the fluoroquinolone antibiotic norfloxacin was obtained, its stability was determined, and its solubility was studied. It was shown that the resulting amorphous form has good temporal stability. The optimal models describing the cold crystallization process are the Nakamura and Sbirrazzuoli models. Despite the slower dissolution kinetics compared to the crystalline sample, the amorphous form shows higher equilibrium solubility values. These results can be used in pharmaceutical engineering to produce amorphous forms of active pharmaceutical ingredients and determine their stability.

Complex compounds are under close scrutiny by scientists as precursors, which are needed to produce functional materials. When the thermolysis method of double complex salts is used on an industrial scale, the most detailed information on the thermal decomposition, including the kinetics of decomposition, is required. The kinetics of pyrolysis, solid, and gaseous products of [Co(NH₃)₆][Fe(C₂O₄)₃]∙2H₂O (I) and [Co(en)₃][Fe(C₂O₄)₃] (II) (en—ethylenediamine) thermolysis were studied in this work. The solid products of thermal decomposition were studied using scanning electron microscopy and elemental analysis, and the specific surface area (8 and 71 m²/g, respectively) was measured. It was determined that a double complex salt (DCS) with a coordinated en has a higher thermal stability than with NH₃ due to the chelation effect.

Reducing the amount of CO₂ in the atmosphere is a very important task. Therefore, the development and search for new approaches to the synthesis of catalytic systems, allowing for the catalytic conversion of CO₂ into valuable products, is an urgent task. In this work, the catalyst was obtained by the thermolysis of a double complex compound. In this regard, kinetic studies of the parameters of the thermolysis process of double complex salts-[Co(NH)₃]₆][Fe(CN)₆] were additionally determined using isoconversion and model approaches of non-isothermal kinetics. The catalyst was studied using various physicochemical methods—X-ray diffraction (XRD), infrared (IR)-spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). It was shown that, at the stage of catalyst preparation, the formation of a CoFe alloy occurred, while the surface mainly consisted of carbon in sp₂-hybridization, and the metals existed in the form of spinel CoFe₂O₄. It was shown that catalysts based on bimetallic salts were active in the process of hydrogenation of carbon dioxide without a pre-activation stage (CO₂ conversion reached 28%, with a specific activity of 4.0 µmolCO₂/gMe·s). It was established that it was possible to change the selectivity of the carbon dioxide hydrogenation process by pre-treating the catalyst with hydrogen (selectivity for methane formation in the presence of an unreduced catalyst is 46.4–68.0%, whereas in the presence of a reduced catalyst it is 5.1–16.5%).

Peat has attracted considerable interest as a potential source of alternative fuel in terms of improving hydrocarbons production and satisfying market demand. The next decade is likely to witness a raise in its exploitation. Nevertheless, the characteristics of peat pyrolysis process, via which many experts expect a considerable generation of hydrocarbons, have not been dealt with in depth. In the present study we have applied thermal analysis combined with isoconversional and model methods for clarifying the kinetic and thermodynamic aspects of the process of generating hydrocarbons from peat via pyrolysis in the absence and presence of iron tallates as a catalytic agent. The obtained results showed a positive effect of the opted catalyst on the process of peat pyrolysis. It has been shown that the catalyst is able to reduce the energy of activation of peat pyrolysis process. Moreover, the Gibbs energy, enthalpy and entropy of complex formation values have been found lower in the presence of iron tallates for all the applied isoconversional methods (Friedman and KAS). The evidence from the present study points toward the beneficial effect generated from the utilization of iron tallates in the processes of hydrocarbons generation from peat for improving energy production in the future.

There is still considerable controversy surrounding the mechanisms, thermodynamics, and kinetics of heavy oil aquathermolysis and pyrolysis processes. The present paper aims to widen our knowledge about the effect of iron tallates on pyrolysis and aquathermolysis of Cuban heavy oil. The obtained SARA (S: saturates, A: aromatics, R: resins, A: asphaltenes) analysis has shown a significant increase in light hydrocarbon content during aquathermolysis. Moreover, the elemental analysis has indicated an increase in C and H content by almost 4% and 6%, respectively, with a significant decrease in S and O content by up to 23% in the presence of iron tallates. These results have been further confirmed by infrared spectrometry. The obtained IR data indicated that asphaltene and resin compounds transform into light hydrocarbons after aquathermolysis. On another hand, the activation energy of heavy oil pyrolysis decreased in the presence of the utilized catalyst; meanwhile, the reaction rate increased, especially in the temperature range of 200–480 °C, which may validate a significant effect of the used catalyst in real conditions. Moreover, the obtained thermodynamic data showed a decrease in the enthalpy and entropy of activation of oil pyrolysis in the presence of iron tallates. Our results are encouraging in terms of energy consumption, optimization, and process control and should be validated by a larger sample size.

Peat is a resource used for heat and energy, particularly in countries where peat is abundant and conventional fuels are not available. Some countries have made extensive use of peat resources to produce electricity and heat in addition to light hydrocarbons. By doing so, they were able to reduce the cost of importing fossil fuels. To the best of our knowledge, there is a lack of a detailed description of the peat oxidation process in the presence of other substances. Herein, the process of peat oxidation was studied in-depth by means of thermal analysis in the presence of iron tallate acting as a catalytic agent. Differential scanning calorimetry and thermogravimetric analysis demonstrated an oil-like oxidation behavior during the combustion of the used peat. The process of peat oxidation includes two main regions: low-temperature oxidation (LTO), which occurs during the oxidation of light hydrocarbons, followed by the so-called high-temperature oxidation (HTO), which includes the oxidation of the obtained coke-like product. Moreover, the application of non-isothermal kinetics experiments based on the isoconversional and model approach principle have confirmed the role of 2% iron tallate in peat mass by improving the oxidation rate at low- and high-temperature oxidation (HTO) regions. The results obtained from this study have proven that the added catalyst improves efficiency with regards to the energy activation in the process by leading to its significant decrease from 110.8 ± 7.8 kJ/mol to 81.8 ± 7.5 kJ/mol for LTO and from 157.8 ± 19.1 kJ/mol to 137.6 ± 9.3 kJ/mol for HTO. These findings clearly confirm the improvement in the rate of the process by shifting the LTO and HTO peaks to lower regions in the presence of the catalyst. These results further emphasize the possible impact which could be generated by the application of thermally enhanced oil recovery methods on peat development and exploitation.