Á. Fudala

Catalytic synthesis of carbon nanotubes using zeolite support

Catalytic synthesis of carbon nanotubes having fullerene-like structure applying supported transition metal/zeolite catalysts is introduced in this work. Decomposition of unsaturated hydrocarbons was carried out under relatively mild conditions in a fixed bed flow reactor. The quality of the carbon deposit was characterized by means of transmission electron microscopy. For the separation of carbon nanotubes and catalyst particles, chemical methods were applied.

Indium and gallium containing ZSM-5 zeolites: acidity and catalytic activity in propane transformation

Abstract Surface acidity and propane transformation on In-and Ga-containing ZSM-5 type zeolites were investigated to find relation between the acidic character of catalysts prepared by conventional or solid state ion-exchange and the catalytic activity in alkane aromatization. On the basis of the concentration of Brensted and Lewis acid sites measured by IR spectroscopy the In and Ga containing samples may be ordered into three main groups. The presence of Brensted acid sites results in cracking of the hydrocarbon molecules, whereas the aromatization activity is attributed to Lewis acidity associated with the intimate contact of the oxide/zeolite assemblies.

Catalytic production of carbon nanofibers over iron carbide doped with Sn2

Abstract Carbon nanofibers with high surface area can be synthesized in a simple one-step reaction under relatively mild conditions using unsupported SnO-doped Fe 3 C catalyst. The highest activity and carbon fibers with high surface area were obtained with catalyst prepared by direct precipitation. Over this sample, selectivity of carbon deposit formation was close to 100%. It was concluded that the interaction of the two phases might be responsible for the catalytic activity, while the method of dispersal seemed to be important for the quality and surface area of the carbon deposit.

Amino acids, precursors for cationic and anionic intercalation synthesis and characterization of amino acid pillared materials

Abstract The preparation and characterization of amino acid pillared materials are reported in this contribution. Host substances were Na-montmorillonite for cationic and hydrotalcite for anionic pillaring. Guest molecules were L -phenylalanine and L -tyrosine. The pillared materials were characterized by powder X-ray diffraction, BET measurements and FT–IR spectroscopy. Pillaring was successful: the layers propped open and the basal distances increased significantly. For hydrotalcite this increase was always significantly larger than for montmorillonite. This fact indicated that the spatial arrangement of the amino acid moieties is widely different. A model for this arrangement is given.

ZSM-5 zeolites modified by solid-state ion-exchange for NO decomposition

ZSM-5 zeolites modified by conventional and solid-state ion-exchange were characterizedby X-ray diffraction, BET measurements, derivatography, IR spectroscopy in the framework vibration range and acidity measurements with pyridine as probe. NO adsorption and transformation on Cu-, Co-, Ni- and FeZSM-5 zeolites were followed by IR spectroscopy. Mono- and dinitrosyl surface species, adsorbed N2O and NO2 were detected in different concentrations on the tested catalysts. Differences in adsorption behaviour were observed for samples exchanged by the conventional and solid-state procedures.

The advantages of ozone treatment in the preparation of tubular silica structures

We applied ozone for removal of templates from meso- and nanoporous silicate of tubular structure. This treatment resulted in MCM-41 and silicon nanotube products of high quality.

Amino acid-pillared layered double hydroxide and montmorillonite : Thermal characteristics

Zn-Al hydrotalcite (HT) and Na-montmorillonite (Na-mont) were pillared by the deprotonated and the protonated forms of L-tyrosine, respectively. Pillaring was successful as the increased basal spacings due to intercalation attest. L-Tyr-HT proved to be thermally less stabile than HT, while that of L-Tyr-mont did not change compared to Na-mont. DTG curves showed more mass loss steps for the hosts than for the intercalated compounds. The extra steps belonged to the decomposition of the amino acid derivatives. FT-IR spectra of the samples pretreated in vacuum in the 293-773 K temperature range also showed that intercalation was successful and L-Tyr-HT is more temperature sensitive than L-Tyr-mont.

Nanoscale redox catalysts: Cr- and Cr,Al-pillared layer clays: Characterization and catalytic activity

Abstract Via the co-hydrolysis of CrCl 3 and AlCl 3 in the presence of swollen Na-montmorillonite, pillared layer clays were prepared. The location of chromium in the pillars and in the primary pillaring agent, the Al 13 -Keggin ion, was investigated by various methods (mid and far IR and 27 Al NMR spectroscopies). We found that isomorphous substitution of chromium for aluminium did not occur, rather co-hydrolysis and co-pillaring took place. Upon heat treatment the loss of outer-sphere water and dehydroxylation at higher temperatures resulted in the formation of bulky alumina pillars decorated with chromia species. The resulting material was used in the oxidation of 1-phenyl-1-propanol in the presence of tert -butylhydroperoxide as co-oxidant.

Behaviour of Hydrotalcite and Its Fe (CN)64- Pillared Derivative on Heat Treatment

Mg-Al L(ayered) D(ouble) H(ydroxide) was prepared and its thermal behaviour was characterized by thermoanalytical methods (TG, DTG, DTA), 27Al M(agic) A(ngle) S(pinning) NMR spectroscopy, X-ray diffractometry (XRD) and S(canning) E(lectron) M(icroscopy). Heat treatment destroyed the layered structure, which could only be partially reconstituted by rehydration. On calcination mixed oxide with the predominance of basic sites were formed. Pillaring the LDH with Fe(CN)64- anions was also performed. The material was characterized by XRD and BET measurements. Heat stability of the pillared substance was investigated, too. Pillaring proved to be successful, however, decreased heat resistance was found in the intercalated material relative to the guest LDH.

Thermogravimetric investigation: Solid-state ion-exchange procedure of Cu2+, Co2+, Ni2+ and Fe2+ ions into montmorillonite

Ion-exchange of transition metal ions into montmorillonite was investigated using two different ion-exchange procedures. Performing ion-exchange from aqueous solution of the respective metal ion leads to material possessing measurable BrØnsted acidity, while the solid-state exchange materials show predominantly Lewis acidity.Measurements by means of a derivatograph allowed us to construct a feasible reaction mechanism for solid-state ion exchange. Satisfactory correlation was found between the results calculated from the reaction steps assumed and the measurements by means of a derivatograph.