Włodzimierz Miśta

Some catalytic properties of hydrothermally synthesised zinc aluminate spinel

Abstract Two samples of zinc aluminate were hydrothermally synthesised from zinc acetate and different aluminium sources: basic aluminium nitrate or aluminium hydroxide. The textural properties of the prepared ZnAl 2 O 4 samples are different from these one of the zinc aluminate prepared by conventional way. Powder XRD and TEM measurements reveal that samples are single-phase material or mixture of ZnAl 2 O 4 with small amount of γ-Al 2 O 3 , with morphology of quasi-spherical shape. Catalytic properties of the hydrothermally obtained zinc aluminate and Pt (Pd) catalysts supported on them were investigated in the reactions of cyclohexene isomerisation and combustion of trichloroethylene, respectively. It was evidenced that activity and selectivity of the investigated materials could be qualitatively correlated with the part of the strong acid centres measured by TPD of NH 3 .

Promotional effect of molybdenum, chromium and cobalt on a VMgO catalyst in oxidative dehydrogenation of ethylbenzene to styrene

Abstract The influence of molybdenum, chromium and cobalt on the oxidation state and redox processes in VMgO catalyst is studied by means of X-ray diffraction and electron spin resonance spectroscopy. The results obtained are correlated with catalytic activity and selectivity. It is shown that molybdenum doping increases the selectivity and the chromium and cobalt doping improves the activity of the catalyst studied. The promotional effect of the dopants on the catalytic mechanism is discussed.

Morphological and phase changes of transition aluminas during their rehydration

Transition aluminas (TA), obtained by fast (0.5–1 s) calcination of gibbsite in the temperature range 375–600°C, were rehydrated at 20, 70 and 90°C. The rehydration process was investigated using transmission electron microscopy. X-ray, and thermogravimetric-differential thermal analysis. During rehydration, the TAs react yielding aluminium hydroxides: pseudoboehmite, boehmite, and bayerite. The phase-composition changes are accompanied by changes in particle morphology. Using transmission electron microscopy, six stages of rehydration were found, with characteristic morphological changes occurring. The changes are responsible for connecting the particles into stable grains during the process of obtaining catalyst carriers or adsorbents from TA.

A new efficient catalytic method of naphthols ring alkylation

Abstract The attempts carried out so far concerning catalytic ring alkylation of naphthols with alcohols have, as a rule, brought about a complex mixture of products from which the separation of individual compounds with the aim of their practical utilization has been proved to be impossible. We have found that naphthols and some of their derivatives could be easily alkylated with methanol or higher alcohols in the presence of iron oxide catalyst by a gas-phase continuous process. As a result of alkylation the alkyl group enters into the ortho -position to the hydroxyl group. The yields of alkylnaphthols are approximately about 90%, which simplifies their separation and purification considerably. The advantage of the newly developed method of alkylation is that it leads to high degree of raw materials utilization: it is practically wasteless, thus it is well suited to the requirements of modern process technologies. Its application may contribute to the increase of the demand for naphthol derivatives as potential raw materials for many new syntheses of pharmaceuticals, plant protection agents, dyes, etc.

ORTHO-selective phenol methylation over iron-magnesium oxide catalysts

Alkylation of phenol to ORTHO-cresol and 2,6-xylenol with methanol in the presence of iron and iron-magnesium oxide catalysts was investigated. The catalysts displayed high activity and stability. Addition of magnesium oxide to the iron catalyst increases its selectivity towards C-alkylation in ortho-position. It was found that the active phase in the investigated catalysts is highly dispersed magnetite or mixed spinel of Fe(MgFe)O4 type. It is noticed that if Fe+2 ions are replaced by Mg+2 ions in the spinel the basicity of the bifunctional catalyst is augmented, increasing ortho-selectivity of alkylation.

Continuous alkylation of 5-methoxy-1-naphthol and 4-methyl-1-naphthol with alcohols over an iron catalyst

Abstract The vapour phase alkylation of 5-methoxy-1-naphthol and 4-methyl-1-naphthol with alcohols in the presence of an iron catalysts (magnetite) that contained Cr-, Si- and K oxides was investigated. At temperatures of 580–655 K alkylderivatives with high yield in ortho-position to the hydroxyl group were obtained. The reactions were carried out in an continuous process at atmospheric pressure.

Catalytic alkylation of 2-naphthol with C1−C3 alcohols

The vapour phase alkylation of 2-naphthol with C1−C3 alcohols in the presence of an iron catalyst that contains Cr-, Si- and K-oxides was investigated. 2-Naphthol was methylated in a temperature range 520–645 K giving first 1-methyl-2-naphthol and then 1,3-dimethyl-2-naphthol with total selectivity of ortho-alkylation over 98%. In the cases of ethanol and n-propanol, derivatives of 2-naphthol alkylated in the 1-position were obtained with high yield and selectivity. The reactions were carried out in a continuous process at atmospheric pressure.

Zinc aluminates as supports for HDS catalysts

Surface behavior of zinc aluminates prepared according to three different methods has been investigated by TPD NH3 and IR spectroscopy and compared with properties of alumina. It was stated that zinc affects the strength and distribution of acidic sites as well as HDS activity of Mo (CoMo) catalysts supported on Zn doped Al2O3.

Stabilization of hopcalite catalyst in alumina matrix

The properties of hopcalite in alumina matrix have been investigated and compared with conventional hopcalite catalyst. It was found using X-ray diffraction, DTA-TG, TEM, and activity measurements in oxidation of n-butane that the presence of alumina matrix leads to weakening of phase changes of hopcalite and recrystallization of CuMn2O4 spinel. The modified catalyst was also found to show higher activity after calcination at 1073 K than pure hopcalite under the same conditions.AbstractСвойства гопкалита на алюминиевой матрице исследовали и сравнивали с обычным гопкалитным катализатором. С помощью рентгеновской диффракции, ДТА, ТГ и ТЕМ и измерений активности в окислении н-бутана установили, что присутствие матрицы окиси алюминия приводит к уменьшению фазовых изменений гопкалита и перекристаллизации спинельного CuMn2O4. Так, модифицированный катализатор обладает повышенной активностью после кальцинирования при 1073 K по сравнению с чистым гопкалитом в тех же условиях.