Marek Stolarski

Synthesis and characteristic of silica aerogels

The synthesis of silica aerogels had been carried out by hydrolysis of tetraethoxysilane (TEOS) as an aerogel precursor in ethanol solution, followed by gelation of the sols obtained and drying under supercritical conditions. The influence of concentration of TEOS, pH of hydrolysis and pH of gelation on the bulk density, specific surface area and porosity of silica aerogels were investigated.

Supercritical gas extraction of Polish brown coals

Abstract Properties of nine selected samples of Polish brown coals from both strip mines and perspective deposits varying in lithotype have been determined. This involved technical analysis of the elementary, group and petrographie compositions. The coals were extracted with supercritical toluene at 410 °C and 13 M Pa. The humic acid content and humodetrinite content were found to be well correlated with the yield of coal extract. The optimal conditions of gas extraction for a selected coal sample were determined.

Structural characterization of residues from supercritical gas extraction of brown coal

Abstract Residues from supercritical gas extraction of brown coal with toluene and butanol were studied by proximate and ultimate analyses, optical microscopy and X-ray diffractometry. The type of solvent appeared to have a decisive influence on the yield, properties and structure of the residues produced in the range 380–440 °C. The residues from extraction with toluene had a microstructure and structural ordering similar to those of the raw coal. Extraction with butanol gave caked and optically anisotropic residues with a relatively high degree of structural ordering.

Synthesis and properties of alumina aerogels

The synthesis of alumina aerogels has been carried out by hydrolysis of aluminium isopropylate as an aerogel precursor dissolved in isopropanol or methanol, followed by gelation of the sols obtained and drying under supercritical conditions and calcination. The influence of two main preparation parameters, precursor concentration and reagents (water to aluminium isopropylate) mole ratio, on the physicochemical properties of aerogels was investigated.

Mathematical analysis of hydrogenating depolymerization of asphaltenes from coal extracts

Abstract The mathematical analysis of hydrogenating depolymerization of asphaltenes from coal extracts is presented. The experiments were carried out in an autoclave in the presence of natural aluminosilicate with high content of iron at temperatures 673–733 K, and under hydrogen pressure 9.8–29.4 MPa. The parameters of the process have been optimized and suggestions regarding the conversion routes for asphaltenes formulated. An extensive depolymerization of asphaltenes into oils is possible in the presence of a disposable, natural aluminosilicate catalyst.

Photodegradation of organic compounds in water

Photodegradation of organic compounds in water The application of photocatalytic processes for the decontamination treatment of polluted water has inspired very extensive studies. Titanium dioxide with its large band gap energy and appropriate redox potential was found as one of the most promising semiconductors for the photodegradation of pollutants in the water as well as in gas phase. The titania-silica aerogels obtained by a simple co-hydrolysis method was applied in the photodegradation of the model organic compound. Different ageing times and heat treatment temperatures were found to influence both the activity and the textural properties of the photocatalysts. The obtained aerogels are efficient photodegradation catalysts of methylene blue and allow a removal up to 98 and 78% of the model pollutant from 20 and 500 ppm solutions, respectively.

PHYSICOCHEMICAL PROPERTIES AND HYDROGENATION ACTIVITY OF NICKEL-ALUMINA AEROGELS

Nickel-alumina aerogel catalysts were prepared by three methods: (I) hydrolysis of a mixture of aerogel precursors, followed by cogelation of the sols obtained and drying under supercritical conditions; (II) impregnation of thermally treated alumina aerogels with nickel salt solutions followed by drying of the suspensions obtained under supercritical or (III) conventional conditions. Activity of the aerogel catalysts prepared was determined in cyclohexene hydrogenation.

Mathematical analysis of the depolymerization of asphaltenes from coal extract

Abstract Results of mathematical analysis of a catalytic process for hydrogenating depolymerization of asphaltenes obtained from coal extract is presented. The experiments analysed were carried out in an autoclave under pressures of 9.8–29.4 MPa at 673–733 K in the presence of a Polish commercial catalyst G-1 (Co,Mo/Al 2 O 3 ). The parameters of hydrogenation have been optimized and a hypothesis concerning directions of asphaltenes conversion has been proposed. Formation of oil components via benzene-insolubles is probable.