Must the best laboratory prepared catalyst also be the best in an operational application?

Three cobalt mixed oxide deN(2)O catalysts, with optimal content of alkali metals (K, Cs), were prepared on a large scale, shaped into tablets, and tested in a pilot plant reactor connected to the bypassed tail gas from the nitric production plant, downstream from the selective catalytic reduction of NOx by ammonia (SCR NOx/NH3) catalyst. High efficiency in N2O removal (N2O conversion of 75-90% at 450 degrees C, VHSV = 11,000 m(3) m(bed)(-3) h(-1)) was achieved. However, a different activity order of the commercially prepared catalyst tablets compared to the laboratory prepared catalyst grains was observed. Catalytic experiments in the kinetic regime using laboratory and commercial prepared catalysts and characterization methods (XRD, TPR-H-2, physisorption, and chemical analysis) were utilized to explain this phenomenon. Experimentally determined internal effectiveness factors and their general dependency on kinetic constants were evaluated to discuss the relationship between the catalyst activity in the kinetic regime and the internal diffusion limitation in catalyst tablets as well as their morphology. The theoretical N2O conversion as a function of the intrinsic kinetic constants and diffusion rate, expressed as effective diffusion coefficients, was evaluated to estimate the final catalyst performance on a large scale and to answer the question of the above article title.Web of Science92art. no. 16

The Physiology and Proteomics of Drought Tolerance in Maize: Early Stomatal Closure as a Cause of Lower Tolerance to Short-Term Dehydration?

Understanding the response of a crop to drought is the first step in the breeding of tolerant genotypes. In our study, two maize (Zea mays L.) genotypes with contrasting sensitivity to dehydration were subjected to moderate drought conditions. The subsequent analysis of their physiological parameters revealed a decreased stomatal conductance accompanied by a slighter decrease in the relative water content in the sensitive genotype. In contrast, the tolerant genotype maintained open stomata and active photosynthesis, even under dehydration conditions. Drought-induced changes in the leaf proteome were analyzed by two independent approaches, 2D gel electrophoresis and iTRAQ analysis, which provided compatible but only partially overlapping results. Drought caused the up-regulation of protective and stress-related proteins (mainly chaperones and dehydrins) in both genotypes. The differences in the levels of various detoxification proteins corresponded well with the observed changes in the activities of antioxidant enzymes. The number and levels of up-regulated protective proteins were generally lower in the sensitive genotype, implying a reduced level of proteosynthesis, which was also indicated by specific changes in the components of the translation machinery. Based on these results, we propose that the hypersensitive early stomatal closure in the sensitive genotype leads to the inhibition of photosynthesis and, subsequently, to a less efficient synthesis of the protective/detoxification proteins that are associated with drought tolerance

Genetic determination of CO2 fixation in C3 and C4 plants

Department of Genetics and MicrobiologyKatedra genetiky a mikrobiologieFaculty of SciencePřírodovědecká fakult

Inter- and intraspecific variability in Vicia faba L. and Zea mays L. response to water deficit

This work monitors the response of plants to water deficit and subsequent restoration of water availability with the aim to expand our knowledge about plant behaviour during and after drought stress from the perspective of two plant species with a different type of photosynthesis. A particular attention was paid to the intraspecific differences and their possible changes during stress and post-stress periods. The plant response was monitored as the changes of selected photosynthetic, morphological and developmental characteristics caused by the cessation of watering for six days followed by a six-day period of renewed optimal water supply. The experiments were carried out on plants with different types of photosynthesis - C3 plant Vicia faba L and C4 plant Zea mays L.; for both plant species, three varieties / genotypes were monitored. The response of both plant species to insufficient water supply differed by the extent of changes in relative water content (RWC), chlorophyll fluorescence parameters, the dry mass of individual leaves (developed during the stress period), the ratio between the aboveground dry mass and dry mass of roots. In drought-stressed plants, downward trend in RWC was observed, as well as the increase of the minimum yield of chlorophyll fluorescence in dark-adapted leaves (F ),..

Genetic determination of CO2 fixation in C3 and C4 plants

Department of Genetics and MicrobiologyKatedra genetiky a mikrobiologieFaculty of SciencePřírodovědecká fakult

Catalytic activity of rhodium grafted on ordered mesoporous silica materials modified with aluminum in N2ON_2O decomposition

Three different ordered mesoporous silica materials, such as MCM-41, Al-containing MCM-41 (with 1.6 wt% of Al incorporated into the silica framework) and SBA-15, were prepared. Furthermore, aluminum (1.8 wt%) was grafted on the silica surface by the molecular designed dispersion method (MDD). In a next step, rhodium (1.4–2.9 wt%), as an active metal for the catalytic reaction of N2O decomposition, was introduced by the MDD technique. The following order of the catalytic activity was found under an inert atmosphere: Al(incorporated)-MCM-41 + Rh > MCM-41 + Al(grafted) + Rh > SBA-15 + Rh ≈ MCM-41 + Rh. The influence of textural properties, total acidity and rhodium dispersion on the activity of catalysts was studied

Oxidation of Methanol and Dichloromethane on TiO₂-CeO₂-CuO, TiO₂-CeO₂ and TiO₂-CuO@VUKOPOR^®A Ceramic Foams

The application-attractive form of TiO2, CeO2 and CuO-based open-cell foam supported catalysts was designed to investigate their catalytic performance in oxidation of two model volatile organic compounds—methanol and dichloromethane. TiO2-CeO2, TiO2-CuO and TiO2-CeO2-CuO catalysts as thin films were deposited on VUKOPOR®A ceramic foam using a reverse micelles-controlled sol-gel method, dip-coating and calcination. Three prepared catalytic foams were investigated via light-off tests in methanol and dichloromethane oxidation in the temperature range of 45–400 °C and 100–500 °C, respectively, at GHSV of 11, 600 h−1, which fits to semi-pilot/industrial conditions. TiO2-CuO@VUKOPOR®A foam showed the best catalytic activity and CO2 yield in methanol oxidation due to its low weak Lewis acidity, high weak basicity and easily reducible CuO species and proved good catalytic stability within 20 h test. TiO2-CeO2-CuO@VUKOPOR®A foam was the best in dichloromethane oxidation. Despite of its lower catalytic activity compared to TiO2-CeO2@VUKOPOR®A foam, its highly-reducible -O-Cu-Ce-O- active surface sites led to the highest CO2 yield and the highest weak Lewis acidity contributed to the highest HCl yield. This foam also showed the lowest amount of chlorine deposits

Oxidation of methanol and dichloromethane on TiO₂-CeO₂-CuO, TiO₂-CeO₂ and TiO₂-CuO@VUKOPOR®A ceramic foams

Abstract The application-attractive form of TiO₂, CeO₂ and CuO-based open-cell foam supported catalysts was designed to investigate their catalytic performance in oxidation of two model volatile organic compounds—methanol and dichloromethane. TiO₂-CeO₂, TiO₂-CuO and TiO₂-CeO₂-CuO catalysts as thin films were deposited on VUKOPOR®A ceramic foam using a reverse micelles-controlled sol-gel method, dip-coating and calcination. Three prepared catalytic foams were investigated via light-off tests in methanol and dichloromethane oxidation in the temperature range of 45–400 °C and 100–500 °C, respectively, at GHSV of 11, 600 h⁻¹, which fits to semi-pilot/industrial conditions. TiO₂-CuO@VUKOPOR®A foam showed the best catalytic activity and CO₂ yield in methanol oxidation due to its low weak Lewis acidity, high weak basicity and easily reducible CuO species and proved good catalytic stability within 20 h test. TiO₂-CeO₂-CuO@VUKOPOR®A foam was the best in dichloromethane oxidation. Despite of its lower catalytic activity compared to TiO₂-CeO₂@VUKOPOR®A foam, its highly-reducible -O-Cu-Ce-O- active surface sites led to the highest CO₂2 yield and the highest weak Lewis acidity contributed to the highest HCl yield. This foam also showed the lowest amount of chlorine deposits

The differences in leaf proteins observed either between the genotypes or between control (C) and drought-stressed (S) plants of 2023 and CE704 maize genotypes, as evaluated by the 2D-electrophoresis method.

<p>AT  =  <i>Arabidopsis thaliana</i> (L.) Heynh.; ETC  =  electron transport chain; OEC  =  oxygen evolving complex of photosystem II; OS  =  <i>Oryza sativa</i> L.; LE  =  <i>Lycopersicon esculentum</i> Mill.; TA  =  <i>Triticum aestivum</i> L.; ZM  =  <i>Zea mays</i> L. The following symbols indicate the quantity of individual spots: –  =  absence, +/−  =  very weak intensity, +  =  medium intensity, ++  =  high intensity.</p

The functional classification of differentially expressed drought-related proteins from maize leaves.

<p>The number of proteins identified by the iTRAQ method in two maize genotypes (2023 and CE704) with up-regulated (<b><i>A</i></b>) or down-regulated (<b><i>B</i></b>) levels is shown; only those proteins whose levels changed due to drought in at least one genotype by at least twofold were included. ET: proteins of the photosynthetic electron-transport chain and chlorophyll synthesis; SM: proteins participating in photosynthetic carbon fixation and saccharide metabolism; MT: membrane proteins participating in transport; LM: proteins participating in lipid metabolism; AM: proteins participating in amino acid metabolism; DX: detoxification proteins; ST: stress proteins; DH: dehydrins; CP: chaperones; SG: proteins involved in cell signaling; PT: proteases and their inhibitors; GE: proteins participating in gene expression and its regulation; MS: miscellaneous proteins.</p