Jerzy Walendziewski

Thermal and catalytic conversion of waste polyolefines

Abstract Waste samples of polyethylene and polystyrene were cracked thermally or in the presence of catalyst and hydrogen in closed autoclaves. The obtained products were submitted to analysis, unsaturated hydrocarbons in gasoline and diesel fuel range boiling were hydrogenated over platinum catalyst. It was stated that the optimum thermal cracking temperature of waste polyolefines is 410–430°C, in the case of catalytic process lower temperature, ca. 390°C, can be used, with reaction time ca. 1.5 an hour. More than 90% yield of gas and liquid fractions with b.p.

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.

Physicochemical properties and hds activity of CoMo−P−Al2O3 catalysts

Porous structure, acidity and hds activity of the CoMo−P−Al2O3 catalysts have been studied. Phosphorus was introduced jointly with molybdenum. This method of phosphorus incorporation gave substantial diminution of surface area, moderate changes of acidity and decrease in hds activity for the catalysts with P2O5 content higher than 5 wt.%.AbstractИсследовали пористую структуру, селективность и гдс активность катализатров CoMo−P−Al2O3. фосфор вводили совместно с молибденом. Этот метод встраивания фосфора приводит к частичномы уменьшению повернностной площади, умеренным изменениям кислотности и уменьшению гдс активности для катализаторов с содержанием P2O5 више 5 вес.%.

Doped aluminas as hydrorefining catalyst supports

Abstract The influence of the addition of boron, calcium, magnesium, zirconium and zinc compounds on the physicochemical properties of alumina supports has been studied. Dopants were introduced during aluminium hydroxide precipitation. It was concluded that the effect of dopant incorporation depends on the type of additive and its concentration in the precipitated slurry. Aluminas doped with boron and magnesium showed the best physicochemical properties as hydrorefining catalyst supports. The obtained results are discussed on the basis of the open literature results.

Influence of the forming method on the pore structure of alumina supports

Abstract Four types of forming devices (twin-system screw extruder, single screw extruder, piston extruder, disc granulator) and four sorts of peptizing solutions (some of them with sugar as pore regulating agents) were applied to prepare alumina supports. Aluminum hydroxide was mixed with peptizing agents, kneaded, formed, dried and calcined at 773 K. The used forming devices as well as the sugar and nitric acid containing peptizing solutions were shown to enable the preparation of bimodal aluminas with various pore structures. The pore structure of these supports typically had a first dominating pore radius in the range 3–5 nm, a second one in the range 20–1250 nm and a macropore volume from 0.1 up to ca. 1 dm 3/ kg. It was evidenced that the calcination temperature does not influence the structure of the macropores.

Preparation of large pore alumina supports for hydrodesulfurization catalysts

Abstract Two types of active carbons and three types of carbon blacks were used as pore forming agents for alumina support preparation. Aluminum hydroxide was mixed with different quantities of these materials (2.5 to 20wt.%) then peptized, formed, dried and calcined at 823 K in order to remove inflammable materials. The use of carbon blacks was shown to enable the preparation of bimodal aluminas with the first dominating a pore radius in the range 4 to 6 nm and the second one dominating a pore radius in the range 10 to 20 nm. The use of active carbons also resulted in bimodal aluminas, however, with these dominating a pore radius in the range of 50 to 250 nm.

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.

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.

Skeletal isomerization of 1-pentene

Series of ZSM-5 and Y zeolite catalysts have been prepared. Zeolites were submitted to ion exchange, drying, formation with 50 wt.% of aluminium hydroxide as a binder and then to final thermal treatment. Determination of catalysts activity in 1-pentene isomerization reaction was carried out in the temperature range of 175–325°C. The highest activity in isomerization reaction was attained in the presence of ZSM-5 zeolite catalysts with strong and medium strength acidity.

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.