Papers by Mirek Derewinski
Molecules, Apr 6, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Steamed zeolites have improved catalytic properties for hydrocarbon activation (alkane cracking r... more Steamed zeolites have improved catalytic properties for hydrocarbon activation (alkane cracking reaction as well as alkane dehydrogenation). The nature of this practically important phenomenon has remained a mystery for the last six decades and was speculated to be related to increased Bronsted acidity during dealumination. We now prove that during steaming aluminum oxide clusters evolve (due to hydrolysis of Al out of framework positions with the following clustering) in the zeolitic micropores with properties very similar to (nano)facets of hydroxylated transition-alumina surfaces. Bronsted acidity of zeolite does not increase and the total number of Bronsted acid sites decreases during steaming. O5Al(VI)-OH surface sites of alumina clusters dehydroxylate at elevated temperatures to form penta-coordinate Al1O5 sites that are capable of initiating alkane cracking by breaking the first C-H bond very effectively, with the following reaction steps catalyzed by nearby zeolitic Bronsted acid sites. This explains the underlying reason behind the improved alkane cracking and alkane dehydrogenation activity of steamed zeolites: heterolytic C-H bond breaking occurs on penta Al(V)1O5 sites of aluminum oxide clusters confined in zeolitic pores. Furthermore, slightly decreased number of adjacent Al framework sites (due to Al dislodgement from the framework) decreases the coking activity, prolonging catalyst lifetime. Our findings explain the origin of enhanced activity of steamed zeolites at the molecular level and provide the missing understanding of the nature of extra-framework Al species formed in steamed/dealuminated zeolites. Furthermore, our findings suggest that similar La2O3 clusters exist for La-containing zeolites and the origin of their cracking activity promotion should be similar. Zeolites are arguably the most important industrial materials employed in petroleum refining and cracking [1-9]. They are crystalline and microporous solids composed of tetrahedral SiO4 and Si-OH-Al units, with ordered arrays of micropores/microcavities: alkane transformations into more
Thermochimica Acta, 1995
The non-isothermal desorption of water adsorbed on ZSM-5 zeolites at room temperature shows, depe... more The non-isothermal desorption of water adsorbed on ZSM-5 zeolites at room temperature shows, depending on the cation type (H+, Na'), differently structured desorption curves. A kinetic analysis based on various methods shows that the course of desorption is well described by a first order rate equation considering a distribution function for the desorption energy. In addition, adsorption isotherms were measured at room temperature. The adsorption energy distribution functions calculated with a regularization method can be correlated with the desorption energy distributions. FTIR investigations of water-loaded zeolites enables the assignment of desorption steps to different adsorbate complexes.
We report the formation of a new Lewis acid Al site in H-FAU zeolite upon 650 ⁰C thermal treatmen... more We report the formation of a new Lewis acid Al site in H-FAU zeolite upon 650 ⁰C thermal treatment, unknown for any zeolite. Spectroscopy and DFT calculations reveal this site is a naked Al +3 ion which is charge balanced by a triplet of adjacent framework oxygens with net charge of-1 for each Si-O-Al moiety. This is the first reported observation of a +3 cation stabilized in a zeolite and the first confirmation of existence of aluminum triplets (as opposed to Al pairs) in that can stabilize such cations in siliceous zeolites. This site forms a thermally stable carbonyl O3Al-CO complex with the highest known frequency at 2252 cm-1 for a carbonyl complex on any solid material. These findings open new horizons in zeolite chemistry and expand our understanding of polyvalent metals' interactions with zeolites. Zeolites are crystalline and microporous materials consisting of tetrahedral SiO4 and AlO4 units in a periodic arrangement [1]. Siliceous zeolites (Si/Al ratio of 5 and higher) are more thermally and hydrothermally stable, and widely used industrially for various applications either in their proton or metal-exchanged form [1-4]. The bridging hydroxyl groups of Si-OH-Al units possess BrÖnsted acidity, and they can exchange protons for cations. It is well-known that metals and non-metals of +1 charge can be easily exchanged into zeolites [5-8] to produce materials with interesting catalytic and adsorptive properties [5-12]. Metals of +2 charge can be exchanged either as M(II)-OH units (where only 1 framework Al-O is binds +1 cation and the-OH group on M(II) maintains the valence state) or M(II) cation bound by the Al pairs (2 nearby Al-O sites) [13-16]. We recently showed that certain bare transition and noble M(I) and M(II) cations in zeolites have unusually high electrophilicity [13,14, 18], with zeolite acting as a weakly-coordinating ligand, that explains their high coordinative unsaturation, ability to coordinate multiple ligands simultaneously, useful
ChemInform, Aug 23, 2010
ChemInform Abstract The catalyst which is obtained by CO-precipitation of sodium silicate, alumin... more ChemInform Abstract The catalyst which is obtained by CO-precipitation of sodium silicate, aluminum sulfate, and TiCl4 from dilute nitric acid (pH 4) proves to be most effective one, TiO2 exerting a synergistic effect. Increase in temp. affects the product ratio (III)/(IV) in favor of the p-isomer. Increased formation of (V) is observed at 165-200 rc C and with the passing of reaction time.
Microporous and Mesoporous Materials, Aug 1, 2023
ACS Applied Materials & Interfaces, Apr 17, 2018
Alkali-exchanged SSZ-13 adsorbents were investigated for their applicability in separating N2 fro... more Alkali-exchanged SSZ-13 adsorbents were investigated for their applicability in separating N2 from CO2 in flue gas streams using a dynamic breakthrough method. In contrast to IAST calculations based on equilibrium isotherms, K+ exchanged SSZ-13 was found to yield the best N2 productivity, comparable to Ni-MOF-74, under dynamic conditions where diffusion properties play a significant role. This was attributed to the selective, partial blockage of access to the chabazite cavities, enhancing the separation potential in a 15/85 CO2/N2 binary gas mixture.
Elsevier eBooks, 1993
Abstract The n-octane cracking has been studied with a series of H-SAPO-37 of increasing Si conte... more Abstract The n-octane cracking has been studied with a series of H-SAPO-37 of increasing Si content and for HY, dealuminated HY and LZY-82. The influence of framework Si content in SAPO-37 strongly depends on the pretreatment temperature which very likely modifies the distribution of atoms in the structure. Silica impurities are not involved in this process. The catalytic activity of H-SAPO-37 increases up to a pretreatment of 1173 K while that of the Si-Al faujasites decreases. In this high pretreatment temperature range SAPO-37 is more active than the faujasites. The selectivity indicates a higher olefin/paraffin ratio for the Si rich SAPO-37 samples i.e. a lower hydrogen transfer activity. The ratio iso-olefin/iso-paraffin is higher in SAPO-37 than in LZY-82 while it is the opposite for the ratio branched/non branched products.
Elsevier eBooks, 1984
Abstract Physicochemical and catalytic properties of ZSM-5 zeolites modified with nickel, magnesi... more Abstract Physicochemical and catalytic properties of ZSM-5 zeolites modified with nickel, magnesium and phosphorus have been studied. Conversion of methanol and alkylation of toluene with methanol were used as test reactions. Measurements of sorption capacity of argon, water, cyclohexane, para- and ortho-xylene revealed plugging of channels and modication of hydrophilicity due to impregnation. Introduction of phosphorus blocked all strong acid centers, whereas Ni and Mg had only little effect on their distribution. Unmodified HZSM-5 and Ni/HZSM-5 gave near-equilibrium composition of xylene isomers, whereas with P/HZSM-5 95-100% of para-isomer was formed. Introduction of nickel resulted in considerable increase of the content of aromatics in methanol conversion.
Nature Communications, Oct 15, 2021
CO oxidation is of importance both for inorganic and living systems. Transition and precious meta... more CO oxidation is of importance both for inorganic and living systems. Transition and precious metals supported on various materials can oxidize CO to CO 2. Among them, few systems, such as Au/TiO 2 , can perform CO oxidation at temperatures as low as −70°C. Living (an) aerobic organisms perform CO oxidation with nitrate using complex enzymes under ambient temperatures representing an essential pathway for life, which enables respiration in the absence of oxygen and leads to carbonate mineral formation. Herein, we report that CO can be oxidized to CO 2 by nitrate at −140°C within an inorganic, nonmetallic zeolitic system. The transformation of NO x and CO species in zeolite as well as the origin of this unique activity is clarified using a joint spectroscopic and computational approach.
Chemical Science, 2022
Cu/zeolites efficiently catalyze selective reduction of environmentally harmful nitric oxide with... more Cu/zeolites efficiently catalyze selective reduction of environmentally harmful nitric oxide with ammonia. Despite over a decade of research, the exact NO reduction steps remain unknown. Herein, using a combined spectroscopic, catalytic and DFT approach, we show that nitrosyl ions (NO +) in zeolitic micropores are the key intermediates for NO reduction. Remarkably, they react with ammonia even below room temperature producing molecular nitrogen (the reaction central to turning the NO pollutant to benign nitrogen) through the intermediacy of the diazo N 2 H + cation. Experiments with isotopically labeled N-compounds confirm our proposed reaction path. No copper is required for N 2 formation to occur during this step. However, at temperatures below 100 C, when NO + reacts with NH 3 , the bare Brønsted acid site becomes occupied by NH 3 to form strongly bound NH 4 + , and consequently, this stops the catalytic cycle, because NO + cannot form on NH 4-zeolites when their H + sites are already occupied by NH 4 +. On the other hand, we show that the reaction becomes catalytic on H-zeolites at temperatures when some ammonia desorption can occur (>120 C). We suggest that the role of Cu(II) ions in Cu/zeolite catalysts for low-temperature NO reduction is to produce abundant NO + by the reaction: Cu(II) + NO / Cu(I)/NO +. NO + then reacts with ammonia to produce nitrogen and water. Furthermore, when Cu(I) gets re-oxidized, the catalytic cycle can then continue. Our findings provide novel understanding of the hitherto unknown steps of the SCR mechanism pertinent to N-N coupling. The observed chemistry of Cu ions in zeolites bears striking resemblance to the copper-containing denitrification and annamox enzymes, which catalyze transformation of NO x species to N 2 , via di-azo compounds.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
ChemInform, Oct 30, 1990
The results of 1H NMR self‐diffusion experiments show that H3PO4 penetrates into the channel netw... more The results of 1H NMR self‐diffusion experiments show that H3PO4 penetrates into the channel network of the ZSM‐5 zeolite.
The Journal of Physical Chemistry C, 2018
Mesoporous layered aluminosilicates were prepared by a two-stage route using tetrapropylammonium ... more Mesoporous layered aluminosilicates were prepared by a two-stage route using tetrapropylammonium hydroxide (TPAOH) and hexadecylamine (HDA). First, aluminosilicate sols were prepared from very dilute solutions under mild conditions. The optically clear sols contained aluminosilicate nanoclusters of the average size 4-5 nm. 27 Al NMR studies demonstrated that tumbling alone of the small aluminosilicate nanoclusters due to Brownian motions was removing effectively chemical shift anisotropy, dipolar interactions and narrowing quadrupolar interactions; thus, magic-angle-spinning was not required for obtaining good quality
Studies in Surface Science and Catalysis, 1986
The acid-base properties of a series of alkali metal exchanged ZSM5 zeolites were investigated by... more The acid-base properties of a series of alkali metal exchanged ZSM5 zeolites were investigated by i.r. spectroscopy, temperature programmed desorption and reaction and with catalytic measurements. The samples have moderately strong Lewis acid sites (Li > Na > K > Rb > Cs) and weak base sites. A comparison of the desorption behaviour of ammonia and pyridine with that of benzene revealed that the former compounds adsorb exclusively via their nitrogen atom, while benzene interacts with its x electron system. With all probe molecules LiZSM5 was found to be the most acidic and CsZSM5 to be the least acidic sample prepared. Temperature programmed and catalytic reactions of propan-2-ol reveal a similar order of acidity, the base properties seem, however, not to change significantly.
Studies in Surface Science and Catalysis, 2008
Abstract A method of preparation of high-silica zeolite crystals (MFI type) containing meso-/macr... more Abstract A method of preparation of high-silica zeolite crystals (MFI type) containing meso-/macrovoids is described. The modification of the crystals was obtained during the hydrothermal synthesis with the use of different meso-/macro matrices like mono- and polydispersed carbon particles. Presence of the meso-/macrovoids in the crystals was directly proved with TEM analysis. The modified MFI zeolite crystals could be successfully used for the deposition of highly dispersed metal (Pd) phase when the impregnation with a metal salt solution (the incipient wetness technique) followed by the reduction in an H2/N2 stream was applied. The deposition of small (2–4 nm) Pd clusters inside the meso-/macrovoids was proved with HRTEM and STEM/HAADF technique. The deposition of Pd in the crystals limited the size and number of bigger metal particles deposited at the outer surface.
Angewandte Chemie, 2019
Acid functionalization of a carbon support allows to enhance the electrocatalytic activity of Pd ... more Acid functionalization of a carbon support allows to enhance the electrocatalytic activity of Pd to hydrogenate benzaldehyde to benzyl alcohol proportional to the concentration of Brønsted‐acid sites. In contrast, the hydrogenation rate is not affected when H2 is used as a reduction equivalent. The different responses to the catalyst properties are shown to be caused by differences in the hydrogenation mechanism between the electrochemical and the H2‐induced hydrogenation pathways. The enhancement of electrocatalytic reduction is realized by the participation of support‐generated hydronium ions in the proximity of the metal particles.
Springer eBooks, Nov 10, 2005
The conversion of gas condensate has been studied over monofunctional acidic MFI zeolites and bif... more The conversion of gas condensate has been studied over monofunctional acidic MFI zeolites and bifunctional Zn-, Co-, Ni- and Mo-containing MFI catalysts. The active sites were characterized by IR spectroscopy of adsorbed pyridine. The correlation obtained between the catalytic activity of various MFI catalysts and the strength of their Lewis and Brönsted sites suggested that the strong Lewis sites and medium Brönsted are responsible for gas-condensate conversion into gasoline and propane-butane fraction.
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Papers by Mirek Derewinski