Papers by Andrzej Kotarba
Journal of Physical Chemistry C, Oct 21, 2011
ABSTRACT In this article a comprehensive molecular modeling of the reaction mechanism complemente... more ABSTRACT In this article a comprehensive molecular modeling of the reaction mechanism complemented by ab initio microkinetic modeling of the catalytic decomposition of N2O on MgO nanocrystals is discussed. The density functional level of theory was used to study the molecular mechanism of conceivable elementary steps of the deN2O reaction over the most stable (100) surface, including the effect of surface morphology. It is shown that terrace sites are responsible for steady state reactivity, whereas the more basic and reactive sites located on edges and corners are involved only in the initial stages of the reaction because of poisoning. Detailed analysis of the reaction progress in terms of the energy profiles and the evolution of partial charges and bond orders for each step allowed for an in-depth insight at the atomic scale into the nature of the catalytic N2O decomposition over anionic redox active sites constituted by surface O2– ions. The harmonic transition state theory along with the calculated free enthalpies of activation were used to model the reaction progress in pulse (transient) and steady state regimes as well as to predict the kinetic isotopic effects (KIE) for 15N and 18O labeled reactants. The proposed kinetic scheme was able to reproduce the results of temperature-programmed surface reaction and KIE experiments with high accuracy without fitting of any parameters.
Frontiers in Chemistry
As an efficient and durable engine, a diesel engine has a broad application. However, soot partic... more As an efficient and durable engine, a diesel engine has a broad application. However, soot particles (PM) and nitrogen oxides (NOx) coming from diesel engines are the main causes of air pollution, so it is necessary to design and prepare an effective catalyst for the simultaneous elimination of PM and NOx. In this work, a novel 3DOM ZrTiO4 support and a series of WxCeMnOδ/3DOM ZrTiO4 catalysts (where x indicates the wt% of W) were designed and fabricated by the colloidal crystal template technique. Among the as-prepared catalysts, the W1CeMnOδ/3DOM ZrTiO4 catalyst exhibits the highest NO conversion rate (52%) at the temperature of maximum CO2 concentration (474°C) and achieves 90% NO conversion in the temperature range of 250–396°C. The excellent catalytic performance is associated with the macroporous structure, abundant oxygen vacancies, sufficient acid sites, and the synergistic effect among the active components. The possible reaction mechanisms of WxCeMnOδ/3DOM ZrTiO4 catalysts...
Engineering of Biomaterials, 2010
Catalysts, 2019
Direct decomposition of nitric oxide (NO) proceeds over Co–Mn–Al mixed oxides promoted by potassi... more Direct decomposition of nitric oxide (NO) proceeds over Co–Mn–Al mixed oxides promoted by potassium. In this study, answers to the following questions have been searched: Do the properties of the K-promoted Co–Mn–Al catalysts prepared by different methods differ from each other? The K-precipitated Co–Mn–Al oxide catalysts were prepared by the precipitation of metal nitrates with a solution of K2CO3/KOH, followed by the washing of the precipitate to different degrees of residual K amounts, and by cthe alcination of the precursors at 500 °C. The properties of the prepared catalysts were compared with those of the best catalyst prepared by the K-impregnation of a wet cake of Co–Mn–Al oxide precursors. The solids were characterized by chemical analysis, DTG, XRD, N2 physisorption, FTIR, temperature programmed reduction (H2-TPR), temperature programmed CO2 desorption (CO2-TPD), X-ray photoelectron spectrometry (XPS), and the species-resolved thermal alkali desorption method (SR-TAD). The...
Catalysts, 2019
Fundamental research on direct NO decomposition is still needed for the design of a sufficiently ... more Fundamental research on direct NO decomposition is still needed for the design of a sufficiently active, stable and selective catalyst. Co-based mixed oxides promoted by alkali metals are promising catalysts for direct NO decomposition, but which parameters play the key role in NO decomposition over mixed oxide catalysts? How do applied preparation conditions affect the obtained catalyst’s properties?
Catalysis Communications, 2014
ABSTRACT The effect of alkali promotion of a Fe3O4 catalyst in soot combustion was systematically... more ABSTRACT The effect of alkali promotion of a Fe3O4 catalyst in soot combustion was systematically investigated for a series of alkali elements (Li, Na, K and Cs) at various surface coverages. The correlation between catalyst performance and work function lowering was established and discussed in terms of the electron donor character of the alkali promotion. This effect was found to follow the sequence of the increasing ionic radii of the alkali promoters Li &lt; Na &lt; K &lt; Cs. For each alkali promoter, the highest activity corresponds to a different optimal surface coverage.
Materials Science and Engineering: C, 2012
The mechanical and protective properties of parylene N and C coatings (2-20 μm) on stainless stee... more The mechanical and protective properties of parylene N and C coatings (2-20 μm) on stainless steel 316L implant materials were investigated. The coatings were characterized by scanning electron and confocal microscopes, microindentation and scratch tests, whereas their protective properties were evaluated in terms of quenching metal ion release from stainless steel to simulated body fluid (Hanks solution). The obtained results revealed that for parylene C coatings, the critical load for initial cracks is 3-5 times higher and the total metal ions release is reduced 3 times more efficiently compared to parylene N. It was thus concluded that parylene C exhibits superior mechanical and protective properties for application as a micrometer coating material for stainless steel implants.
Catalysis Today, 2011
Potassium addition has different influence on the selectivity to isobutene in oxidative dehydroge... more Potassium addition has different influence on the selectivity to isobutene in oxidative dehydrogenation of isobutane for the two chromium based catalysts: the decrease for CrOx/Al2O3(CrAl) and the increase for CrOx/TiO2(CrTi). This contrary effect of potassium was found to be associated with the increase in the rate of oxygen chemisorption (equivalent to the rate of reoxidation) and the increase in coverage
Catalysis Today, 2008
Isothermal and TPSR studies of deN 2 O reaction were performed over model MgO, and Co-MgO systems... more Isothermal and TPSR studies of deN 2 O reaction were performed over model MgO, and Co-MgO systems. Complementary experiments such as O 2-TPD, H 2 O-TPD and IR, supported by DFT molecular modeling were carried out to elucidate the role of topological irregularities such as corners, steps, edges on the principal reaction events in dry and wet environment. The hydroxyl groups produced upon water adsorption were used for selective blocking of the active sites. Topological aspect of the surface reactivity was discussed in terms of the energetics of reaction steps and the relative stability and mobility of reaction intermediates (O 2 2À) and inhibiting (OH À surf) species. Whereas the most active corner sites are depleted by oxygen, produced in the course of N 2 O decomposition, the edge and step sites could be eliminated only by more strongly adsorbed water. In steady state conditions the reaction turns over mainly on terrace sites and is moisture insensitive. Upon introduction of Co 2+ ions to magnesium oxide the N 2 O conversion curve is shifted by 200 8C towards lower temperatures, due to the change in the N 2 O activation step (from anionic redox to cationic redox). However, at such thermal conditions the terrace sites remain still hydroxylated, and the overall reaction rate is clearly deteriorated by water present in the feed.
Catalysis Today, 2007
Molecular DFT modeling combined with computational spectroscopy (EPR and IR) were applied for ana... more Molecular DFT modeling combined with computational spectroscopy (EPR and IR) were applied for analysis of the NO bond breaking and NN and OO bond making in the context of deNOx and deN2O reactions. Interaction of NO, N2O and NO2 with cationic (transition metals) and anionic (surface O2− ions) centers was explored at the molecular level. The elementary events such as
Applied Catalysis A: General, 2011
Composite ferrite catalyst consisting of pristine irregular KFeO 2 crystallites and well develope... more Composite ferrite catalyst consisting of pristine irregular KFeO 2 crystallites and well developed hexagonal nanoplates of selectively doped (2%Ce,2%Cr)-K 2 Fe 22 O 34 was prepared, characterized (XRD, HR-TEM, SEM-EDX, BET) and tested for potassium volatilization and catalytic performance in ethylbenzene dehydrogenation. In comparison with separate parent ferrite phases the obtained composite catalyst exhibited superior overall catalytic performance (stability and activity), combining the best features of its components. Indeed, it exhibits the conversion and selectivity to styrene monomer of the most active phase of 2% Ce, 2% Cr-doped K 2 Fe 22 O 34 , whereas the thermal stability of potassium was even higher than in the most stable KFeO 2 phase.
Materials
Background: The use of nanotechnology in the production of medical equipment has opened new possi... more Background: The use of nanotechnology in the production of medical equipment has opened new possibilities to fight bacterial biofilm developing on their surfaces, which can cause infectious complications. In this study, we decided to use gentamicin nanoparticles. An ultrasonic technique was used for their synthesis and immediate deposition onto the surface of tracheostomy tubes, and their effect on bacterial biofilm formation was evaluated. Methods: Polyvinyl chloride was functionalized using oxygen plasma followed by sonochemical formation and the embedment of gentamicin nanoparticles. The resulting surfaces were characterized with the use of AFM, WCA, NTA, FTIR and evaluated for cytotoxicity with the use of A549 cell line and for bacterial adhesion using reference strains of S. aureus (ATCC® 25923™) and E. coli (ATCC® 25922™). Results: The use of gentamicin nanoparticles significantly reduced the adhesion of bacterial colonies on the surface of the tracheostomy tube for S. aureus ...
Otolaryngologia Polska
Introduction. In hospitalized patients, tracheostomy tubes (TTs) are susceptible to colonization ... more Introduction. In hospitalized patients, tracheostomy tubes (TTs) are susceptible to colonization by biofilm producing potentially pathogenic microorganisms (PPMs). Contact with TTs, which are situated in a critical region of the body with enormous microbial exposure, may lead to the emer-gence of resistant respiratory infections. Objective. Our study aimed to isolate and identify Gram-positive and Gram-negative PPMs, mark their antibiotic resistance and determine the bacteriological pattern of the biofilm colonizing the TTs. Methods. The study was conducted on 45 tracheostomy tubes obtained from 45 hospitalized adult patients with trachestomy with intubation periods ranging from 1 to 28 days. Tracheal aspirates (TA) obtained from polyvinyl chloride (PVC) TTs were used for the analysis. Bacteria in biofilms were identified by standard microbiological techniques, tested for antibiotic resistance and phenotypic resistance according to the EUCAST guidelines and visualized by SEM. Results...
International Journal of Molecular Sciences
Surface-modified graphite is studied as an electrode material, an adsorbent, and a membrane compo... more Surface-modified graphite is studied as an electrode material, an adsorbent, and a membrane component, among other applications. Modifying the graphite with plasma can be used to create relevant surface functionalities, in particular, various oxygen groups. The application of surface-oxidized graphite often requires its use in an aqueous environment. The application in an aqueous environment is not an issue for acid-oxidized carbons, but a discrepancy in the structure–activity relationship may arise because plasma-oxidized carbons show a time-dependent decrease in the degree of functionalization and related properties. Moreover, plasma-oxidized materials are often characterized in terms of their chemical and physical properties, most notably their degree of functionalization after plasma treatment, without contact with water. In this study, we used low-temperature plasma oxidation with pure oxygen and carbon dioxide and sample-washing with concentrated nitric and sulfuric acids. To ...
Engineering of Biomaterials, 2017
Engineering of Biomaterials, 2010
Wstęp Ze względu na swoje własności mechaniczne, zdolność do nadawania kształtów oraz niską cenę ... more Wstęp Ze względu na swoje własności mechaniczne, zdolność do nadawania kształtów oraz niską cenę w porównaniu z innymi metalicznymi materiałami implantacyjnymi (stopy tytanu i kobaltu) stal nierdzewna jest często używanym materiałem implantacyjnym. Jednak, podczas długotrwałego kontaktu z tkankami ludzkimi następują procesy korozyjne na powierzchni stali związane z niepożądanym uwalnianiem jonów metali takich jak: żelazo, chrom i nikiel [1]. Korozja i proces uwalniania jonów powodują nie tylko uszkodzenia mechaniczne implantów, ale również odczuwania bólu w pobliżu wszczepionego implantu. Dlatego też implanty wymagają specyficznego rodzaju obróbki powierzchniowej w celu zminimalizowania szkodliwych zjawisk [2]. Obecnie, powłoki polimerowe wykorzystywane są do modyfikacji
Engineering of Biomaterials, 2013
The multilayer protective polymer coating based on parylene C modified with oxygen plasma was dev... more The multilayer protective polymer coating based on parylene C modified with oxygen plasma was developed. The paper reports an investigation on surface chemical composition (XPS) and surface free energy (contact angle, Owens-Wendt) of modified parylene C. Bioresorbable L-lactide-co-glycolide copolymer (PLGA) was used to obtain drug-loaded matrices. The matrices underwent hydrolytic degradation and estimation of drug release profile. The microstructural changes which appeared during degradation were observed by means of high resolution nuclear magnetic spectroscopy (NMR). The kinetic profiles of drug release were investigated with high performance liquid chromatography (HPLC).
Highlights • Optimization of spinel phase loading for Co3O4|Al2O3|cordierite catalyst. • Evaluati... more Highlights • Optimization of spinel phase loading for Co3O4|Al2O3|cordierite catalyst. • Evaluation of pressure drops for bare support, washcoated monolith and full catalyst. • Investigation of synthesis condition impact on catalyst composition, morphology and performance.
Reaction Kinetics, Mechanisms and Catalysis, 2021
The oxidation of soot over RuRe bimetallic nanoparticles (NPs) supported on γ-Al2O3 has been inve... more The oxidation of soot over RuRe bimetallic nanoparticles (NPs) supported on γ-Al2O3 has been investigated. The catalysts were synthesized by a microwave-polyol method and characterized by ICP, BET, TEM, STEM-EDS, XRD and XPS techniques. The study revealed that the proper choice of the Re loading (0.4–2.0 wt%) is crucial for the catalytic behavior of the 2% Ru–Re/Al2O3 nano-catalysts.The best catalytic properties, in terms of overall activity and stability, were observed for the 2%Ru-0.8%Re/γ-Al2O3 nano-catalyst. The stability of all bimetallic 2% Ru–Re nano-catalysts in catalytic soot oxidation in the presence of oxygen is very high in contrast to the 2% Ru/γ-Al2O3 sample. The presence of rhenium in the catalytic system hinder the formation of large RuO2 agglomerates leading to a better dispersion of active ruthenium phase and a better catalytic performance. The relationship between the catalytic activity of Ru–Re/γ-Al2O3 and the synergetic roles of Ru and Re is discussed.
Uploads
Papers by Andrzej Kotarba