Lucjan Chmielarz

Pillared smectite modified with carbon and manganese as catalyst for SCR of NOx with NH3. Part II. Temperature‐programmed studies

Temperature‐programmed desorption (TPD) and surface reaction (TPSR), and additionally FTIR spectroscopy of adsorbed NO molecules were used to characterise surface sites on pillared smectites modified with carbon and manganese. Much higher adsorption of NH3 than NO was found, but acidic pre‐treatment increased NO sorption to comparable values as well as catalytic performance in SCR of NOx. In this case formation of strongly bound NO3− species was recognised, which reacted with NH3 at a temperature 200 °C higher than weaker adsorbed NO.

Advances in selective catalytic oxidation of ammonia to dinitrogen: a review

Ammonia emission to the atmosphere is an important environmental problem. A significant increase in ammonia emission is expected in automotive and energy production sectors in the near future. It is related to the spreading of technologies that use ammonia for NOx conversion in flue gases (e.g. DeNOx, DEF) and combustion of nitrogen rich fuels (e.g. biogas, biomass). Among the various methods of ammonia elimination from flue gases, its catalytic selective oxidation to dinitrogen seems to be the most promising one. Different types of catalytic systems active in selective ammonia oxidation are presented and discussed. Moreover, the possible mechanisms of ammonia oxidation and the concept of a bifunctional catalyst are discussed and analysed. Finally, future trends in these studies are suggested.

Simultaneous removal of dyes and metal cations using an acid, acid-base and base modified vermiculite as a sustainable and recyclable adsorbent

The aim of this work was the modification of vermiculite in order to produce a low cost, efficient and sustainable adsorbent for dyes and metals. Three activation methods consisting of acid, base and combined acid/base treatment were applied to improve the of vermiculites adsorption properties. Adsorbents were tested in single, bi- and tricomponent solutions containing cationic dyes and Cu2+ cations. The raw material showed low adsorption capacity for dyes and metal. The acid/base treated vermiculite had very good adsorption capacity toward dyes while the maximum adsorption capacity for Cu2+ did not change comparing to the starting material. The alkaline treated vermiculite was a good adsorbent for metals, while still being able to remove dyes on the level of the not treated material. Moreover, it was shown that the materials may be regenerated and used in several adsorption-desorption cycles. Furthermore, it was possible to separate adsorbed dyes from metals that were desorbed, using as eluents ethanol/NaCl and 0.05M HNO3, respectively. This opens a possibility for sustainable disposal and neutralization of both of the pollutants or for their further applications in other processes.

Pillared smectite modified with carbon and manganese as catalyst for SCR of NOx with NH3. Part I. General characterization and catalyst screening

Carbon- and manganese-modified zirconia-pillared smectites were prepared, characterized (XRD, BET and pore analysis, XPS) and tested in selective catalytic reduction of NOx with NH3. Both untreated and acidic pretreated smectites were used. The acid pretreatment increased NO conversion and influenced the extent of carbon introduction into the porous system. The carbon deposit improved selectivity of the catalytic reduction to N2.

The influence of acid treatments over vermiculite based material as adsorbent for cationic textile dyestuffs

The influence of different acid treatments over vermiculite was evaluated. Equilibrium, kinetic and column studies have been conducted. The results showed that vermiculite first treated with nitric acid and then with citric acid has higher adsorption capacity, presenting maximum adsorption capacities in column experiments: for Astrazon Red (AR), 100.8 ± 0.8 mg g(-1) and 54 ± 1 mg g(-1) for modified and raw material, respectively; for Methylene Blue (MB) 150 ± 4 mg g(-1) and 55 ± 2 mg g(-1) for modified and raw material, respectively. Materials characterization by X-ray diffraction, UV-vis-diffuse reflectance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, X-ray fluorescence, N2 adsorption and CEC determination, has been performed. The results suggest the existence of exchange of interlayer cations, leaching of metals from vermiculites sheets and formation of an amorphous phase in the material. Adsorption follows pseudo 2(nd) order model kinetics for both dyestuffs and equilibrium occurs accordingly to Langmuirs model for AR and Freundlichs model for MB. In column systems Yans model is the best fit. The enhanced properties of acid treated vermiculite offer new perspectives for the use of this adsorbent in wastewater treatment.

Effect of water vapour and SO2 addition on stability of zirconia-pillared montmorillonites in selective catalytic reduction of NO with ammonia

Abstract A series of acid-treated zirconia-pillared montmorillonites doped with carbon and manganese was studied in selective catalytic reduction (SCR) of NO with NH3. For selected catalysts, various stability tests were performed. Catalysts M2C and M2CMn14 showed very good stability in long-run tests with the use of a standard reaction mixture. Addition of water vapour caused small decrease in NO conversion but the effect was reversible. SO2 poisoning gave different results depending on the applied method. In the conditions well-simulating DENOX process, i.e. when SO2 was added in the course of catalytic reaction, the activity of the studied catalysts did not change.

Hierarchically structured ZSM-5 obtained by optimized mesotemplate-free method as active catalyst for methanol to DME conversion

In the presented studies, a new method for the synthesis of hierarchical porous materials with ZSM-5 zeolite properties was applied. The proposed method is based on the acidification of the zeolite seeds slurry using HCl solution, followed by hydrothermal treatment, enabling the aggregation of zeolite nanoseeds with the formation of the interparticle mesoporous structure. The influence of the duration of zeolite parent mixture aging before and after acidification on the resulting properties of the samples was investigated. The physicochemical properties of the obtained micro-mesoporous samples were analyzed using techniques such as N2-sorption measurements, X-ray diffraction, TG analysis, NH3-TPD and electron microscopy. In the second part of the studies, the influence of the modified zeolite sample parameters (such as porosity, acidity and crystallinity) on their catalytic activity for dimethyl ether (DME) synthesis from methanol was studied. DME is considered as a future clean alternative to diesel fuel and the development of methods for its synthesis is currently of high scientific interest. It was shown that modification of the porous structure and acidity of the zeolitic samples strongly influences their catalytic activity, selectivity and stability for the DME synthesis process. The micro-mesoporous samples, despite their significantly lower acidity, exhibited high catalytic activity (similar to conventional ZSM-5 zeolite) and enhanced selectivity towards DME, as well as higher stability in a long term catalytic test (higher resistance to the formation of coke deposits) in comparison to standard MFI-type zeolites.

Montmorillonite intercalated with SiO2, SiO2-Al2O3 or SiO2-TiO2 pillars by surfactant-directed method as catalytic supports for DeNOx process

The intercalation of natural montmorillonite with SiO2, SiO2-Al2O3 or SiO2-TiO2 pillars by the surfactant-directed method resulted in the formation of high surface area porous materials; these were tested as catalytic supports for the process of selective catalytic reduction of NO (DeNOx). The incorporation of titanium or aluminium into the structure of the silica pillars significantly increased the surface acidity of the clay samples. Iron and copper were deposited onto the surface of the pillared clays mainly in the form of monomeric isolated cations and oligomeric metal oxide species. The contribution of the latter species was higher in the clay intercalated with SiO2-TiO2 pillars than in the samples modified with SiO2 and SiO2-Al2O3 pillars. The pillared clay-based catalysts were active in the DeNOx process but, in this group, the best results were obtained for the clay intercalated with SiO2-TiO2 pillars and doped with iron and copper. The catalytic performance of the samples is discussed in respect of their surface acidity and active forms of transition metal species deposited.

Enhancement of Electrochemical Performance of LiMn2O4 Spinel Cathode Material by Synergetic Substitution with Ni and S

Nickel and sulfur doped lithium manganese spinels with a nominal composition of LiMn2−xNixO4–ySy (0.1 ≤ x ≤ 0.5 and y = 0.01) were synthesized by a xerogel-type sol-gel method followed by subsequent calcinations at 300 and 650 °C in air. The samples were investigated in terms of physicochemical properties using X-ray powder diffraction (XRD), transmission electron microscopy (EDS-TEM), N2 adsorption-desorption measurements (N2-BET), differential scanning calorimetry (DSC), and electrical conductivity studies (EC). Electrochemical characteristics of Li/Li+/LiMn2−xNixO4–ySy cells were examined by galvanostatic charge/discharge tests (CELL TEST), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The XRD showed that for samples calcined at 650 °C containing 0.1 and 0.2 mole of Ni single phase materials of Fd-3m group symmetry and nanoparticles size of around 50 nm were obtained. The energy dispersive X-ray spectroscopy (EDS) mapping confirmed homogenous distribution of nickel and sulfur in the obtained spinel materials. Moreover, it was revealed that the adverse phase transition at around room temperature typical for the stoichiometric spinel was successfully suppressed by Ni and S substitution. Electrochemical results indicated that slight substitution of nickel (x = 0.1) and sulfur (y = 0.01) in the LiMn2O4 enhances the electrochemical performance along with the rate capability and capacity retention.

Ag-loaded zeolites Y and USY as catalysts for selective ammonia oxidation

IR spectroscopic studies of NH3 and CO adsorption were applied to establish the status of Ag0 and Ag+ in silver loaded zeolites Y and USY. The nature of the silver particles and ions and their dispersion were found to be influenced by the type of support. Application of zeolite USY as support allowed to operate such catalysts at low temperatures with high selectivity to nitrogen (95%). Zeolite USY as support guaranteed a high concentration of uniformly dispersed metallic silver species and Ag+ cations with strong electron acceptor properties. The silver species of defined nature together with the highly acidic centres in AgUSY protected NH4+ ions against oxidation thus high selectivity to nitrogen was observed.