Mieczysław Kozłowski

Ammoxidation of brown coals for supercapacitors

The paper reports results of a study on the use of active carbon from ammoxidated brown coal as electrode material for supercapacitors. The raw coal was subjected to demineralisation and ammoxidation by a mixture of ammonia and air, then it was carbonised and activated by steam or carbon dioxide. The electrochemical properties of carbons were determined by galvanostatic and potentiodynamic methods for water electrolytes. The best capacitance parameters of ca. 220 F/g in acidic and ca. 140 F/g in alkaline conditions were obtained for active carbon containing from 2 to 3 wt.% of nitrogen.

Microbial desulfurization of coal with Thiobacillus ferrooxidans bacteria

Abstract Microbial desulfurization of Polish flame coal, characterized by high total concentration of sulfur and a high concentration of pyrite sulfur, was studied. The optimum conditions of the process were established. When using Thiobacillus ferrooxidans bacteria, the best results were obtained with desulfurization carried out on coal samples making 2.4 wt% of the extraction mixture at the initial concentration of ferrous ions of 15 g dm −3 and for a process duration of seven days. Since desulfurization of coal mainly involves oxidation of the pyrite, a kinetic model of Fe 2+ oxidation by Thiobacillus ferrooxidans bacteria was proposed. The process was found to be described well by the equation derived for autocatalytic reaction of the first-order, both towards the inorganic substrate (Fe 2+ ) and the biocatalyst (protein). The rate constants and induction times of Fe 2+ oxidation and protein growth were determined for different temperatures, pH values and initial concentrations of Fe 2+ . The highest rate constant and the shortest induction time were obtained for 35°C and the initial Fe 2+ concentration of 3 g Fe 2+ dm −3 . No effect of pH changes, in a range 2.0–3.0, on the kinetics of the process was noted.

AP-TPR study of sulphur in coals subjected to mild oxidation. Part 1. Demineralised coals

Abstract Five samples of coal characterised by different degree of coalification and different content of sulphur have been subjected to oxidation in the dry phase and in aqueous media in order to determine the effect of oxidation on the sulphur groups. The transformations were studied by the classical chemical methods and by atmospheric pressure–temperature programmed reduction. It has been shown that the greatest changes in sulphur groups occurs in the case of the oxidation with HNO3 and peroxyacetic acid, while the air oxidation and the oxidation in the O2/Na2CO3 system is much less effective. The oxidation leads to formation of sulphoxides, sulphones and sulphonic acids. The non-thiophene groups have been found much more susceptible to oxidation than the thiophene ones.

The influence of extraction with organic solvents on coking properties of raw and reduced coals

The dilatometric properties and Roga index of two orthocoking coals, subject to extraction with n-pentane, methylene chloride and chloroform, were determined in order to investigate the influence of low-molecular weight substances on coking properties of the coals. With increasing extraction yield, their dilatation and agglomerating capacity were observed to decrease, whereas their softening point was shifted towards higher temperatures. The effect of reduction by potassium in liquid ammonia on dilatometric properties of coals, as well as on their agglomerating capacity, was also studied. This reduction was found to cause a significant increase in coal dilatation, a decrease in softening temperature of the coals, and an insignificant increase in their agglomeration capacity. The extracts obtained from raw and reduced coals are characterized and their role as well as the role of the reduction process in the phenomenon of coal plasticity is discussed.

Studies of reduction and reductive alkylation of coals in the potassium/liquid ammonia system. 1. The influence of demineralization on the course of reduction and reductive alkylation of coals

Five Polish coals of different rank were subjected to the reactions of reduction and reductive alkylation in the system potassium/liquid ammonia. The influence of demineralization on the course of these processes as well as on the amount and kind of the reaction products was analysed. Formation of a certain amount of impurities containing mainly alkylammonium iodides was detected during reductive alkylation. Reductive butylation was found to be more effective than reductive ethylation, which is determined mainly by the energy of dissociation of the iodine-alkyl group bond in the applied alkylating agents. A relationship between the kind of substituents introduced into coal and solubility of the reaction products in methylene chloride and n-pentane is discussed.

Multistage butylation of coals in a potassium-liquid ammonia system

Abstract The reductive butylation of different rank coals was investigated using metallic potassium and butyl iodide in liquid ammonia. Multistage butylation was carried out until a high conversion of coal organic substance to products soluble in methylene chloride was reached. The extractability of butylated coals depended on the rank of coal. The best results were obtained for orthocoking coal. The degree of coal conversion to products soluble in methylene chloride after the four-stage butylation reached 93 wt%. The extracts were characterized by means of i.r. and 1 H n.m.r. spectroscopy, molecular weight determination and elemental analysis. On the basis of the n.m.r. spectra, changes in structural parameters of extracts occurring in the course of reductive butylation were determined.

Reductive and non-reductive methylation of high-sulphur coals studied by atmospheric pressure-temperature programmed reduction technique

Abstract Two kinds of high sulphur content coals Mequinenza and Illinois No. 6 have been subjected to reductive and non-reductive alkylation. The reductive alkylation was performed in the potassium/liquid ammonia system, while the non-reductive one was performed according to the procedure proposed by Liotta. In both processes the alkylating reagent was iodomethane. The products were subjected to elemental analysis and studied by IR spectroscopy and Atmospheric Pressure–Temperature Programmed Reduction (AP–TPR) technique. It has been established that much more information can be elicited from AP–TPR results obtained for the samples after modification by reductive or non-reductive alkylation than for non-modified coals. The Mequinenza coal has been found to contain aryl thiols and almost no alkyl thiols, whereas the Illinois No. 6 coal has been shown to contain alkyl thiols while practically no presence of aryl thiols has been detected.

Reduction of high-sulphur coal in the potassium–liquid ammonia system

Abstract Polish high-sulphur coal was twice subjected to reduction in the potassium–liquid ammonia system. The process was carried out on both raw and demineralised coal. Elemental and spectral analyses of the initial coal and the reduction products were performed. Different forms of sulphur found in the samples were studied by the classical chemical methods and by atmospheric pressure–temperature programmed reduction (AP–TPR). The effect of reduction on particular sulphur compounds is discussed. It was found that reduction in the potassium–liquid ammonia system led to cleavage of C–S bonds, appearance of thiol groups, and the partial removal of pyrite and sulphates from the coal whereas the content of elemental sulphur did not change significantly.

Reductive alkylation of coals in liquid ammonia

Abstract The reductive alkylation of two different rank coals was investigated using metallic potassium and alkyl iodide in liquid ammonia. The reduction reaction alone increases the dissolution of the coals in dichloromethane only to a very small extent. However, the reduction process in conjunction with alkylation leads to readily dichloromethane soluble products. The solubilization of alkylated coals depends on the type of coal and the length of the substituent alkyl chain. The extracts were characterized by infra red spectroscopy, molecular mass, hydrocarbon class analysis and elemental analysis.

Multistage reduction of coals in the potassium/liquid ammonia system

Two Polish coals and an anthracite were subjected to four-stage reduction in potassium/liquid ammonia. After each stage, solubility of the products in methylene chloride was studied. Extraction yield was found to increase with increasing number of stages. The highest yield of transformation to soluble products was obtained for the orthocoking coal. The 1H n.m.r. investigations proved that aromaticity of the extracts from flame coal is lower than that of the orthocoking coal extracts. The main substituents of the aromatic system of the average structural unit of the extracts from orthocoking coal are alkyl or naphthene groups. In the case of flame coal their contribution is lower and can be related to a higher contribution of oxygen groups.