Alina Krawczyk

Adam Mickiewicz University, Poznań, Greater Poland Voivodeship, Poland

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Publications (5)3.19 Total impact

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    ABSTRACT: Studies of carbonaceous deposits, intercalated within alumina pores, were carried out from the point of view of their catalytic activity for a number of reactions of alkyl-substituted benzenes. Alumina was not active for ammoxidation of ethylbenzene and m-xylene as well as oxidative dehydrogenation of ethylbenzene until certain amount of the deposit was generated on acid sites of alumina surface. Carbonaceous deposits formed during reactions of decomposition of 2-propanol and hexafluoro-2-propanol were used as supports for platinum catalysts for hydrosilylation of allyl chloride and 1-octene to result in excellent selectivity. Precursor of carbonaceous deposit formed from hexafluoro-2-propanol has been identified and scheme of the deposit formation was proposed.
    Journal of Physics and Chemistry of Solids 01/2004; 65(2):627-632. · 1.53 Impact Factor
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    ABSTRACT: This study was aimed at characterizing paramagnetic properties of cokes formed on aluminas of different origin (calcined at 400 and 800°C) during catalytic reactions of hexafluoro-2-propanol decomposition and, for the sake of comparison, 2-propanol decomposition at 300 and 400°C. No significant differences in coke-forming activities were found between alumina obtained by hydrolysis of aluminium isopropoxide and that prepared by precipitation with ammonia from aluminium sulfate solution at pH 6.1, although they differed substantially in their acidity patterns. On the other hand, clear differences were observed between intensities of electron paramagnetic resonance (EPR) spectra recorded for samples covered with coke produced by reactions of the two alcohols. When hexafluoro-2-propanol was the parent substance, spectral lines were stronger and narrower than those obtained for 2-propanol. The smaller linewidth (ΔBpp=0.29-0.54 mT compared to ΔBpp=0.51-0.92 mT) was most likely a result of exchange interactions between electrons of paramagnetic centers, whose concentrations were higher in the carbonaceous deposit formed from fluorine-containing alcohol. Higher temperature of coke formation (400°C) resulted in higher intensities of EPR spectra, whereas higher temperature of alumina calcination (800°C), prior to its use in alcohol decomposition reaction, brought about lower spectral intensities.
    Applied Magnetic Resonance 09/2003; 24(3-4):343-349. · 0.83 Impact Factor
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    ABSTRACT: This study was aimed at characterizing paramagnetic properties of cokes formed on aluminas of different origin (calcined at 400 and 800~ during catalytic reactions of hexafluoro-2-propanol decomposition and, for the sake of comparison, 2-propanol decomposition at 300 and 400~ No significant differences in coke-forming activities were found between alumina obtained by hydrolys[s of alurninium isopropoxide and that prepared by precipitation with ammonia from aluminium sulfate solution at pH 6.1, although they differed substantially in their acidity patterns. On the other hand, clear differences were observed between intensities of electron paramagnetic resonance (EPR) spectra recorded for samples covered with coke produced by reactions of the two alcohols. When hexafluoro- 2-propanol was the parent substance, spectral lines were stronger and narrower than those obtained for 2-propanol. The smaller linewidth (ABvp = 0.29-0.54 tot compared to ABpp = 0.51-0.92 mT) was most likely a result of exchange interactions between electrons of paramagnetic centers, whose concentrations were higher in the carbonaceous deposit formed from fluorine-containing alcohol. Higher temperature of coke formation (400~ resulted in higher intensities of EPR spectra, whereas higher temperature of alumina calcination (800~ prior to its use in alcohol decomposition reaction, brought about lower spectral intensities.
    Applied Magnetic Resonance 01/2003; 24(3-4):343-349. · 0.83 Impact Factor
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    ABSTRACT: Surface properties of fluorinated carbon were characterised from the point of view of its use as a material for catalytic purposes. Samples with different fluorine content (from 10 to 65 wt.%) were tested for their catalytic activity for a number of reactions of acid-base catalysis involving residual hydroxyl groups as active centres. It was found that they were capable of catalysing only such a reaction proceeding through the formation of carbenium ion for which the presence of very weak acid centres is sufficient. The generation of only weak acidity as a result of fluorination was unexpected, therefore calculations were performed using AM1 method to explain this fact. A simple molecule used as a model of fluorinated carbon surface enabled to predict acidity of residual OH groups which was in agreement with experimental findings.
    Molecular Crystals and Liquid Crystals - MOL CRYST LIQUID CRYST. 01/2000; 354(1):435-442.
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    ABSTRACT: Suitability of fluorinated carbon samples containing from 10 to 65 wt% F for catalytic purposes was evaluated by means of ESR spectroscopy. It has been concluded that samples of high fluorine content make a good material for catalyst support intended for the use in the processes requiring as low as possible contribution of side reactions proceeding according to free radical mechanism. The obtained spectra of all samples investigated consist of two component lines which are characterised by almost identical g factors (g = 2.0023 ± 0.0005) but linewidths are different. The increase in fluorine content to 65 wt% results in a rise in width of the broad component line by a factor of about two and in a reduction in line intensity by a factor of about five compared to those observed in the spectra of the samples containing 10-28 wt% F.
    Molecular Physics Reports. 01/2000; 28:69-73.