Papers by Magdolna Mihályi
Applied catalysis. A, General, Apr 1, 2024
New Journal of Chemistry, 2022
Cyclic alkyl amino mono-and biscarbene ruthenium (CAAC-Ru) complexes were immobilized on mesoporo... more Cyclic alkyl amino mono-and biscarbene ruthenium (CAAC-Ru) complexes were immobilized on mesoporous Y zeolite (catalysts 3 and 4) and showed high activity and stability in ammonia borane (AB) hydrolytic dehydrogenation. Both catalysts have as low as 0.1 wt% Ru content. Catalysts 3 and 4 render reasonable activity even at 10 ppm (0.001 mol%) loading giving a TON value of 79000 (molH2•molcat-1). The optimal loading, however, was found to be slightly higher for catalyst 4, around 50 ppm (0.005 mol%) giving a TON value of 8500 (molH2•molcat-1 •h-1) and TON: 49375 (molH2•molcat-1) retaining high nH2/nAB ratio (2.51). This value is higher than those observed for their homogeneous analogue 2 (TOF: 7500 molH2•molcat-1 •h-1 ; TON: 43600 molH2•molcat-1 ; released nH2/nAB ratio: 2.18). Interestingly, it was found that the zeolite-supported catalyst was of better performance than the non-supported water-soluble derivatives. No ruthenium leaching was detected for any of the zeolite-supported systems. Catalyst 4 showed significantly higher activity than catalyst 3 and could be recycled up to 10 times. Catalyst 4 revealed reasonable hydrolytic dehydrogenation activity even after three days in water upon exposure to air. The highest TON (79000) obtained with catalyst 4 is equal to 1.68 kg H2 per 1 g ruthenium metal.
Microporous and Mesoporous Materials, Oct 1, 2023
Zárójelentés a Mikro-/mezopórusos kompozit zeolitanalóg ferriszilikátok előállítása és vizsgálata... more Zárójelentés a Mikro-/mezopórusos kompozit zeolitanalóg ferriszilikátok előállítása és vizsgálata c. K 68414 sz. OTKA projektről * A zárójelben álló szám a vonatkozó közlemény sorszáma a publikációs jegyzékben brought to you by CORE View metadata, citation and similar papers at core.ac.uk
Microporous and Mesoporous Materials, 2007
A method for the preparation of phase-pure [Al]-BEA and [Al,B]-BEA zeolites based on solid-state ... more A method for the preparation of phase-pure [Al]-BEA and [Al,B]-BEA zeolites based on solid-state recrystallization of synthetic aluminum-containing magadiites is presented. For comparison [B]-BEA was prepared by conventional hydrothermal synthesis. From X-ray diffraction (XRD) measurements conclusions could be drawn in respect to kinetics and mechanism of the recrystallization process. Coordination state and resistance to hydrolysis of framework boron species in as-synthesized and ion-exchanged BEA varieties were investigated by 11 B MAS NMR spectroscopy. The acidity of the samples was studied by temperature-programmed ammonia elimination (TPAE) from the NH 4-forms and by IR spectroscopy using pyridine as probe molecule. An effect of framework boron on the acid strength of bridged hydroxyls associated with framework aluminum could not be evidenced. Nevertheless, incorporated boron gives rise to weak acid sites which are involved in ion-exchange processes. The number of strong Brønsted sites can be controlled by the aluminum content of the layer silicate.
Journal of Molecular Catalysis A: Chemical, 2013
Phase-pure [Al]BEA and [Al,B]BEA zeolites, prepared by solid-state recrystallization of synthetic... more Phase-pure [Al]BEA and [Al,B]BEA zeolites, prepared by solid-state recrystallization of synthetic aluminum-containing magadiites and conventionally synthesized [B]BEA, were tested, after ion exchange with nickel, as bifunctional catalysts for hydroconversion of n-heptane. The reducibility of nickel ions incorporated into BEA zeolites by ion exchange was investigated by temperature-programmed reduction (TPR). The acidity of the samples was characterized with strong (pyridine (Py), ammonia (NH 3)) and weak (nitrogen) bases. The adsorbed bases were studied by transmission FT-IR (Py), diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy (N 2), and temperatureprogrammed ammonia evolution (TPAE, NH 3). Over Ni/H-[B]BEA the reactants were completely converted via fast hydrogenolysis, whereas this reaction pathway plays only a negligible role in the hydroconversion over Ni/H-[Al]BEA and Ni/H-[Al,B]BEA zeolites. Boron-containing BEA zeolites were less active catalysts than the boron-free catalyst in the principal unimolecular hydroconversion reactions. However, incorporation of boron into the framework of BEA zeolite results in a considerable selectivity shift towards isomerization. Results suggest that the acid strength of bridged hydroxyls, probed with weak (N 2) and strong basis (pyridine), was found to be similar in the boron-free and boroncontaining BEA samples. The decrease in the isomerization rate and the increase of the apparent activation energy upon incorporation of boron may be attributed to the decrease in the heat of n-heptane adsorption.
Catalysts
The hydroconversion of γ-valerolactone (GVL) over Co/SiO2 catalyst proceeds in a complex reaction... more The hydroconversion of γ-valerolactone (GVL) over Co/SiO2 catalyst proceeds in a complex reaction network, resulting in 2-methyltetrahydrofuran (2-MTHF) as the main product, and C4–C5 alcohol and alkane side-products. The catalyst was shown to contain Co0 sites and Lewis acid (Co2+ ion)/Lewis base (O2− ion) pair sites, active for hydrogenation/dehydrogenation and dehydration reactions, respectively. The initial reaction step was confirmed to be the hydrogenation of GVL to key intermediate 1,4-pentanediol (1,4-PD). Cyclodehydration of 1,4-PD led to the main product 2-MTHF, whereas its dehydration/hydrogenation gave 1-pentanol and 2-pentanol side-products, with about the same yield. In contrast, 2-pentanol was the favored alcohol product of 2-MTHF hydrogenolysis. 2-Butanol was formed by decarbonylation of 4-hydroxypentanal intermediate. The latter was the product of 1,4-PD dehydrogenation. Alkanes were formed from the alcohol side-products via dehydration/hydrogenation reactions.
Molecules
Catalytic conversion of ethanol to 1-butanol was studied over MgO–Al2O3 mixed oxide-based catalys... more Catalytic conversion of ethanol to 1-butanol was studied over MgO–Al2O3 mixed oxide-based catalysts. Relationships between acid-base and catalytic properties and the effect of active metal on the hydrogen transfer reaction steps were investigated. The acid-base properties were studied by temperature-programmed desorption of CO2 and NH3 and by the FT-IR spectroscopic examination of adsorbed pyridine. Dispersion of the metal promoter (Pd, Pt, Ru, Ni) was determined by CO pulse chemisorption. The ethanol coupling reaction was studied using a flow-through microreactor system, He or H2 carrier gas, WHSV = 1 gEtOH·gcat.−1·h−1, at 21 bar, and 200–350 °C. Formation and transformation of surface species under catalytic conditions were studied by DRIFT spectroscopy. The highest butanol selectivity and yield was observed when the MgO–Al2O3 catalyst contained a relatively high amount of strong-base and medium-strong Lewis acid sites. The presence of metal improved the activity both in He and H2...
Journal of Porous Materials, 2014
Hierarchical zeolite ZSM-5 synthesized by applying amphiphilic organosilane as mesopore template,... more Hierarchical zeolite ZSM-5 synthesized by applying amphiphilic organosilane as mesopore template, nanosized zeolite Beta and zeolite MCM-22 have been studied, for the first time in the conversion of mixed ethylbenzene-m-xylene feed. The effects of the channel structure, nanosizing and presence of mesopores in these zeolite materials with close Si/Al molar ratio on the catalytic activity and selectivity have been discussed. It was found that the diverse zeolites have different advantages and disadvantages in dependence on their structure and morphology. MCM-22 zeolite provides promising ethylbenzene conversion at low xylene loss with high production of the p-isomer among xylene.
Molecules
Monometallic (Cu, Ni) and bimetallic (Cu-Ni) catalysts supported on KIT-6 based mesoporous silica... more Monometallic (Cu, Ni) and bimetallic (Cu-Ni) catalysts supported on KIT-6 based mesoporous silica/zeolite composites were prepared using the wet impregnation method. The catalysts were characterized using X-ray powder diffraction, N2 physisorption, SEM, solid state NMR and H2-TPR methods. Finely dispersed NiO and CuO were detected after the decomposition of impregnating salt on the silica carrier. The formation of small fractions of ionic Ni2+ and/or Cu2+ species, interacting strongly with the silica supports, was found. The catalysts were studied in the gas-phase upgrading of lignocellulosic biomass-derived levulinic acid (LA) to γ-valerolactone (GVL). The bimetallic, CuNi-KIT-6 catalyst showed 100% LA conversion at 250 °C and atmospheric pressure. The high LA conversion and GVL yield can be attributed to the high specific surface area and finely dispersed Cu-Ni species in the catalyst. Furthermore, the catalyst also exhibited high stability after 24 h of reaction time with a GVL y...
Molecules, 2021
Mono-, and bimetallic Ni-, Ru-, and Pt-modified nanosized Beta zeolite catalysts were prepared by... more Mono-, and bimetallic Ni-, Ru-, and Pt-modified nanosized Beta zeolite catalysts were prepared by the post synthesis method and characterized by powder X-ray diffraction (XRD), nitrogen physisorption, HRTEM microscopy, temperature-programmed reduction (TPR-TGA), ATR FT-IR spectroscopy, and by solid-state MAS-NMR spectroscopy. The presence of nanosized nickel-oxide, ruthenium-oxide, and platinum species was detected on the catalysts. The presence of Brønsted and Lewis acid sites, and incorporation of nickel ions into zeolite lattice was proven by FT-IR of adsorbed pyridine. The structural changes in the catalyst matrix were investigated by solid state NMR spectroscopy. The catalysts were used in a gas-phase hydrodemethoxylation and dealkylation of 2-methoxy-4-propylphenol as a lignin derivative molecule for phenol synthesis.
A projektben a metannal vegzett szelektiv katalitikus NO redukcio (NO-SCR) mechanizmusanak alapos... more A projektben a metannal vegzett szelektiv katalitikus NO redukcio (NO-SCR) mechanizmusanak alaposabb megerteset es ezaltal a reakcioban hatekonyabb katalizator kifejlesztesenek megalapozasat tűztuk ki celul. Vizsgalataink elsősorban a reakciohoz legigeretesebb Co-, In-, es Pd-, valamint Co,In-, es Pd,In-zeolitokra iranyultak. A katalitikus kiserletekben a reduktiv szilardfazisu ioncserevel (RSSIE) előallitott, promovealt In-zeolitok bizonyultak a legaktivabb es legszelektivebb katalizatoroknak. Ramutattunk arra, hogy az RSSIE folyamat illekony InOH koztitermek keletkezesen es annak a savas helyekkel lejatszodo reakciojan keresztul megy vegbe. Megvizsgaltuk, hogy a katalizatorban hogyan es milyen aktiv helyek alakulnak ki. Operando DRIFT spektroszkopiai modszerrel tanulmanyoztuk az NO-SCR reakcio korulmenyei kozott kialakulo feluleti kepződmenyeket es reaktivitasukat. Az eredmenyekből a katalizatorszerkezet es aktivitas kozotti osszefuggesekre, valamint az NO-SCR reakcio mechanizmusara kovetkeztettunk. Kimutattuk, hogy az NO-SCR reakcio korulmenyei kozott az aktiv centrumokon NO+/NO3- kepződmenyek alakulnak ki. A metan az NO3- kepződmennyel reagalva aktivalodik, mig az NO+ a keletkezett aktiv intermedierrel a nitrogen kepződesehez vezető lepesben vesz reszt. Az NO+/NO3- kepződmenyek kialakulasahoz NO2, ill. annak kepződeset katalizalo katalitikus funkcio szukseges. A Co es Pd promotor az NO oxidaciojat gyorsitja fel oxigennel NO2-ve, ami nagyobb feluleti NO+/NO3- koncentraciohoz, s vegul nagyobb NO-SCR aktivitashoz vezet. | The present project concerns the understanding of the mechanism of selective catalytic reduction of NO (NO-SCR) with methane and, thereby, to provide better scientific bases for the development of a more effective catalyst for the reaction. The investigation was focused on the most promising Co-, In-, Pd-, Co,In-, and Pd,In-zeolites. The results of the study revealed that promoted In-zeolites prepared by reductive solid state ion-exchange (RSSI) method were the most active and selective catalysts. It was shown that the RSSIE process proceeded via volatile InOH intermediate and its reaction with the Br?nsted acidic sites of the zeolite. We studied the relation between the method of catalyst preparation and catalytic properties. The surface species formed under reaction conditions in the NO-SCR reaction and their reactivity were investigated by operando DRIFT spectroscopy. The results obtained allowed us to verify the relationship between the catalyst structure and activity and outline a plausible reaction mechanism. It was shown that under conditions of the NO-SCR reaction NO+/NO3- species were formed on the active sites. Methane was activated in reaction with NO3- species, whereas NO+ took part in the reaction with the thus obtained active intermediate leading to the formation of N2. A catalytic function was necessary to obtain NO2 that was needed for the formation of NO+/NO3- species. The Co and Pd promoters accelerated the oxidation of NO to NO2 with O2, which resulted in a higher NO+/NO3- concentration and finally in a higher NO-SCR activity.
Ujfajta modon, gőzfazisu anyagtranszport eljarassal alakitottunk ki vekony, reszben orientalt MFI... more Ujfajta modon, gőzfazisu anyagtranszport eljarassal alakitottunk ki vekony, reszben orientalt MFI zeolitreteget makroporusos hordozon, magadiit Si prekurzorbol. Tovabba szintetizaltunk nagy ateresztőkepessegű, termikusan stabil, nagy szelektivitasu zeolitmembrant in-situ eljarassal es un. masodlagos novesztessel amorf Si-forrasbol kiindulva. Az ecetsav etanolos eszterezeseben sikerult az egyensulyt az etilacetat kepződes iranyaba eltolni a viz folyamatos pervaporacios eltavolitasaval [Fe]MFI (Si/Fe=100) zeolit membranon keresztul. Ebben a kiserletben a zeolitmembran inert szeparatorkent funkcionalt. Borral izomorfan szubsztitualt MFI membran az 1-buten izomerizaciojaban katalizatorkent es szeparatorkent műkodott. Ramutattunk, hogy a vazszerkezetbe beepult borhoz kapcsolodo hidroxilcsoportok gyenge Bronsted-savas centrumok, amit a termekeloszlas (transz-2-buten, cisz-2-buten) is igazolt. A permeat oldali, termodinamikai egyensulyi koncentracional magasabb transz-2-buten koncentracio oka, hogy a zeolit csatornaiban transz-2-buten diffuzioja gyorsabb. A katalitikus modszert alkalmasnak tartjuk a membrant alkoto zeolitkristalyok saverőssegenek jellemzesere, a zeolit vazszerkezetben az izomorf szubsztitucio bizonyitasara, a membranreteg irreverzibilis karosodasa nelkul. Anyagtudomanyi ismereteink bővulesen, kutatasi infrastrukturank javulasan tul a projekt lehetőseget nyujtott Kollar Marton PhD hallgato felkeszult szakemberre valasahoz. | Thin, oriented zeolite layer was synthesized on macroporous alfa-Al2O3 support by vapor-phase transport method applying sheet silicate as Si precursor. High-throughput and high selectivity zeolite membranes, having high thermal and chemical stability were also prepared by in-situ and secondary growth techniques. In the esterification of acetic acid with ethanol the equilibrium was shifted to the formation of ethyl acetate by removing the formed water through the [Fe]MFI (Si/Fe=100) zeolite membrane by pervaporation. In this experiment zeolite membrane worked as inert separator. However, in the reaction of 1-butene isomerization the studied boron substituted MFI membrane had the dual role of the catalyst and the permselective layer. It was proved that double-bond shift occurred, thus cis- and trans-2-butenes were formed. The catalytic selectivity is due to the low acid strength of the Bronsted-sites generated by the framework boron. The ratio of the trans/cis-2-butenes in the permeate stream was higher than the equilibrium value, which was attributed to the permeation selectivity of the membrane for the trans-2-butene. The catalytic method can be applied as acidity characterization technique for the zeolite crystals that build the continuous membrane layer, without irreversible damage of the zeolite film. The project gave opportunity for Marton Kollar Phd student to be trained in membrane techniques and gain experience in this research areas and obtain PhD degree.
Applied Catalysis A: General, 2004
A solid-state ion-exchange method is described that introduces vanadium into zeolites BZSM-5, BBe... more A solid-state ion-exchange method is described that introduces vanadium into zeolites BZSM-5, BBeta and their deboronated by washing forms at 773 K in hydrogen. Two types of vanadium species (vanadium ions in cationic position and VO 2+ complex in a silanol nest) are identified when the amount of V 2 O 5 is equivalent to the framework boron. The vanadium-loaded samples have been characterised by the methods of IR-KBr, FTIR and UV-Vis spectroscopies; temperature-programmed reduction/oxidation cycles (TPR/TPO).
Studies in Surface Science and Catalysis, 1988
Abstract Catalysts containing Bronsted acid sites are active for hydration of 1-butene. The rate ... more Abstract Catalysts containing Bronsted acid sites are active for hydration of 1-butene. The rate determining step is the surface reaction between 1-butene adsorbed in very small amounts and water adsorbed in larger amounts on hydrated protons which are presumably the active sites. Product 2-butanol exerts a competitive inhibition which can be suppressed by water. Zeolites containing late transition metal ions were found to catalyze the hydration of acetylene. This transformation is also kinetically controlled by the rate of the surface reaction between weakly adsorbed acetylene and rather strongly adsorbed water. Acetaldehyde bound to the active sites poisons the reaction reversibly. Its crotonic condensation which would result in a permanent poisoning can be avoided by the elimination of the acidic OH-groups generated by the electrostatic field of bivalent cations.
Egyfajta retegszilikat, a magadiit szilard-fazisu atkristalyositasaval aluminium es bortartalmu b... more Egyfajta retegszilikat, a magadiit szilard-fazisu atkristalyositasaval aluminium es bortartalmu beta zeolitokat allitottunk elő. A bor nem befolyasolta a zeolit vazszerkezeteben a Si(OH)Al(OSi)3 helyekkel kapcsolatban levő Bronsted savas centrumok saverősseget. A bor beepitese gyengen savas centrumokat hoz letre, melyek reszt vesznek az ioncsere folyamatokban. Az [Al,B]-BEA zeolitokban az erősen savas Bronsted centrumok szamat a retegszilikat aluminium-tartalmaval szabalyozhatjuk. A Ni/[Al,B]-BEA zeolitok az alkanok hidrokonverziojaban kevesbe aktiv katalizatorok mint a Ni/[Al]-BEA, azonban a bor beepitese az izomerizacios szelektivitas jelentős novekedeset eredmenyezte. A zeolitok katalitikus tulajdonsagaiban mutatkozo kulonbsegek a kemiai osszeteteltől fuggő adszorpcios tulajdonsagokban jelentkező elteressel magyarazhatok. Nanokristalyos, mikroporusos MCM-22 zeolitbol es mezoporusos MCM-41 szilikatbol allo kompozitokat allitottunk elő. A kompozitok nagy fajlagos feluletűek es nagy...
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Papers by Magdolna Mihályi