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For experimental data obtained under different reaction/process conditions over time or temperature, the kinetic compensation effect (KCE) can be expected. Under dynamic (nonisothermal) conditions, at least two analytical pathways forming the KCE were found. Constant heating rate (q = const) and variable conversion degrees (α = var) lead to a vertical source of the KCE, called the isochronal effect. In turn, for a variable heating rate (q = var) and constant conversion degree (α = const), we can obtain an isoconversional compensation effect. In isothermal conditions (analyzed as polyisothermal), the KCE appears only as an isoconversional source of the compensating effect. The scattering of values for the determined isokinetic temperatures is evidence of a strong influence of the experimental conditions and the calculation methodology. The parameters of the Arrhenius law have been shown to allow the determination of the KCE and further the isokinetic temperature. In turn, using the Eyring equations for the same parameters, we can determine the enthalpy–entropy compensation (EEC) for the activation process and the compensation temperature, which is often treated as an isokinetic temperature. KCE effects have also been shown to be able to be amplified or dissipated, but isokinetic temperature is not a compensating quantity in the literal sense in isoconversional methods because T iso → ∞. Thus, in isoconversional methods, isoconversional KCE values are characterized by strong variability of activation energy corresponding to the weak variation of the pre-exponential factor, which in practice means that ln A → const. This is completely in line with the classical Arrhenius law. [ABSTRACT FROM AUTHOR]

Carbon materials are among the most commonly used components of supercapacitor electrodes. Particularly, active carbons are recognized as cheap, available, and easily tailored materials. However, the carbon family, i.e. carbon products and carbon precursors, consists of many members. In this manuscript some of these materials, including laboratory scale-produced carbon gels, carbon nanotubes and carbonized materials, as well as industrial scale-produced graphites, pitches, coke and coal, were compared. Discussion was preceded by a short history of supercapacitors and review of each type of tested material, from early beginning to state-of-the-art. Morphology and structure of the materials were analyzed (specific surface area, pore volume and interlayer spacing determination), to evaluate their applicability in energy storage. Thermal analysis was used to determine the stability and purity. Finally, electrochemical evaluation using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy was performed. Outcomes of each analytical technique were summarized in different sections. [ABSTRACT FROM AUTHOR]

Samples of PM1 were collected in the surroundings of coking plants located in southern Poland. Chemical fractionation provided information on the contents of trace elements As, Cd, Co, Cr, Hg, Mn, Ni, Pb, Sb and Se in all mobile (F1-F3) and not mobile (F4) fractions of PM1 in the vicinity of large sources of emissions related to energochemical processing of coal during the summer. The determined enrichment factors indicate the influence of anthropogenic sources on the concentration of the examined elements contained in PM1 in the areas subjected to investigation. The analysis of health risk for the assumed scenario of inhabitant exposure to the toxic effect of elements, based on the values of the hazard index, revealed that the absorption of the examined elements contained in the most mobile fractions of particulate matter via inhalation by children and adults can be considered potentially harmless to the health of people inhabiting the surroundings of coking plants during the summer (HI < 1). It has been estimated that due to the inhalation exposure to carcinogenic elements, i.e., As, Cd, Co, Cr, Ni and Pb, contained in the most mobile fractions (F1 + F2) of PM1, approximately four adults and one child out of one million people living in the vicinity of the coking plants may develop cancer. [ABSTRACT FROM AUTHOR]

Kinetic studies of CO gasification of different materials were carried out using the Geneva method in an apparatus for determining the reactivity of cokes. The main purpose of these studies was parallel analysis of the Boudouard-Bell (B-B) reaction progress on the basis of both solid-phase and gaseous products combined with the mass balance of the process. The kinetic equations involve the conversion degree of the solid ( x) or gaseous phase (α) with the kinetic reaction rate constant. It was proved that the mathematical form of the mass balance is similar to the simplest kinetic equation, in which the kinetic constant k is replaced by the known process constant C. Complete kinetic description of the B-B reaction is determined by adopting initial conditions and taking into account the chemical reaction that occurs in a short time interval. [ABSTRACT FROM AUTHOR]

In previous studies, a kinetic equation based on the Ergun mechanism and concept presented in 1956 was applied to Boudouard-Bell reactions for granular coke (1-3 mm) in the temperature range T = 1173-1423 K. In contrast to several other works on this subject, the proposed equation was based on only three kinetic constants: k, the rate constant for the Boudouard reaction; k, the rate constant for the Bell reaction; and k, which is related to the oxy-carbon decomposition and CO desorption process. The dependence of these constants on temperature allows certain values characteristic of the aforementioned processes to be calculated, including activation energy of gasification reaction, enthalpy of disproportionation reaction of gasification and activation energy of desorption process. When k > 0, i.e., the Bell reaction and inhibitory effects occur, the kinetic constant k can be determined using a portion of the experimental [CO] versus time data normalized to the maximum contribution of CO in the outlet gases. [ABSTRACT FROM AUTHOR]

A method for the comparison of kinetic parameters of reaction/process for thermogravimetric measurements at isothermal and dynamic conditions and processes on a larger scale were considered. It is based on the concept of finite time and corresponding total conversion of the solid phase. The method allows for the determination of Arrhenius parameters without the selection of process mechanism. The results obtained for isothermal and dynamic conditions (comparison between dehydration process and thermal decomposition of calcite) indicate that the values of parameter E in both cases are similar, but values of ln A (the entropic factor) differ from each other. It also has been shown that the method of coke and char preparation notably influences the activation energy values of the CO gasification reaction, which is associated with varying degrees of devolatilization and corresponding development of the sample pore surface area. [ABSTRACT FROM AUTHOR]