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[en] The work discusses the use of some catalytic reactors based on non-permselective porous barriers, which look particularly promising in the short term, while the synthesise inorganic membranes with permselectivity and permeability higher than those of their current counterparts will be developed
[it]L'articolo discute l'uso dei reattori catalitici basati su barriere porose non permeoselettive, che sono utilizzati nello sviluppo di processi di produzione alternativi rispetto a quelli tradizionali (deidrogenazioni, produzione di gas di sintesi), in attesa che sia perfezionata la produzione di membrane inorganiche piu' permeoselettive e permeabili di quelle del passato
[en] Interest in heterogeneous catalysis has increased dramatically in the last decade. The extent of interest in this and related field can be accessed from the newly coined terms like, semi-heterogeneous catalysis, for the processes and mechanisms that are amalgam of homogeneous and heterogeneous catalysis. Whereas the progresses made I the area of science and technology of nano materials has provided the main impetus, the innovative processing of carbon nano tubes has added to potential applications in process engineering and consumer applications. The graphene based catalysts are yet another emerging class of catalysts with huge potential. This technical review summarizes the developments made in the area of material developments, a better understanding of processes involved and role of computational chemistry in the recent achievements. The emerging applications in the areas of process engineering have also been discussed. (author)
[en] Nanoparticles are reactive, and their final interactions with the surrounding media are ultimately determined by their reactivity, which in turns depends on the nanoparticles morphology, surface chemistry and environment in which they are embedded. One simple and informative approach for the study of the reactivity of nanoparticles is the determination of their photocatalytic activity. In the present work, we briefly summarize the importance of different parameters such as the size, shape and agglomeration state on the photocatalytic activity of colloidal inorganic nanoparticles. The study of the use of nanoparticles as photocatalyts is relevant not only for its potential applications in environmental remediation issues but also it can provide relevant information about the role of these parameters at the nanoscale.
[en] Hydrogen is considered to be an ideal fuel for future energy demands when it is sourced from clean and renewable energy resources. Photocatalytic splitting of water offers a promising method for the clean, low cost production of hydrogen using solar energy. The inherent problem of pristine TiO2 nanostructured photocatalysts are (i) fast recombination of photogenerated charge carriers before their utilization at catalyst surface-interface and (ii) weak excitation of charge carriers under visible spectrum of solar light. Hence, we have developed efficient photocatalysts that can utilize visible or visible spectrum of solar light and effective transfer of charge carriers at the catalyst-adsorbent interface. This talk discusses design and development of two different types of photocatalysts (a) one dimensional nanostructure(s) and its composites and (b) core-shell nanostructure. In addition, parametric studies on photocatalytic experiments, types of photocatalytic reactors and calculation of quantum efficiency will discussed in detail. (author)
[en] Optimized compositions of a four-color CMYK plus a green pigment have been prepared by the ceramic method: cobalt doping in Celsian (Ba0,9Co0,1)Al2Si2O8 (cyan), chromium in armalcolite (MgFe)(Cr0,2Ti2,8Fe)O10 (magenta), nickel in geikielite (Mg0,5Ni0,5)TiO3 (yellow), the perovskite CrNdO3 (green) and the same perovskite mineralized with alkaline earth fluorides (BaF2 and MgF2) (black). Both pigment powder and glazed sample in a conventional double firing frit (1050°C) have been characterized with respect to its colorimetric performance by the model CIEL*a*b*, its cooling capacity (as cool pigments) by the measurement of the solar reflection index SRI and its photocatalytic capacity by means of the OrangeII degradation test. The obtained results are compared with those obtained with commercial pigments of the CMY family of the zircon. The results indicate that the coloration of the powders and the enamelled samples is more intense, with L* values lower than the zircon homologous pigments, whereas the obtained chroma with the pigments of the zircon is better (b* negative for cyan, a* positive for magenta and b* positive for yellow). Regarding its cooling capacity, the results indicate high SRI values for all samples. In the case of Celsian SRI is higher than for vanadium-zircon, the green of perovskite slightly exceeds the eskolaite Cr2O3 value that is taken as reference. In the case of the black perovskite, very low SRI values are measured (SRI=0 in the case of powder) and associated with high middle-infrared emissivity values, making it interesting as a pigment for absorbent substrates in solar collectors. The photocatalytic capacity over OrangeII indicates half-life values around 55-70minutes, lower than those measured in zircons (110-190minutes).
[es]Se han preparado por el método cerámico composiciones optimizadas de una cuatricromía CMYK más un pigmento verde, basados en el dopado de cobalto en celsiana (Ba0,9Co0,1)Al2Si2O8 (cian), de cromo en armalcolita (MgFe)(Cr0,2Ti2,8Fe)O10 (magenta), de níquel en geikielita (Mg0,5Ni0,5)TiO3 (amarillo), la perovskita CrNdO3 (verde) y la misma perovskita mineralizada con fluoruros alcalinotérreos (BaF2 y MgF2) (negro). Los pigmentos en polvo y los vidriados obtenidos con una frita convencional de bicocción (1.050°C) se han caracterizado respecto de su rendimiento colorimétrico mediante el modelo CIEL*a*b*; su capacidad refrigerante (como cool pigment), mediante la medida del índice de reflexión solar SRI, y su capacidad fotocatalítica, mediante el test de degradación de NaranjaII. Los resultados obtenidos se comparan con los obtenidos con pigmentos comerciales de la familia CMY del circón tomados como referencia. Los resultados indican una coloración intensa de los polvos y de las plaquetas vidriadas con valores L* inferiores a los pigmentos homólogos del circón, en cambio el chroma obtenido con los pigmentos del circón es superior (b* negativo para el cian, a* positivo para el magenta o b* positivo para el amarillo). Respecto a su capacidad refrigerante, los resultados indican valores SRI altos y superiores en el caso de la celsiana al del vanadio-circón, el verde supera ligeramente a la eskolaita Cr2O3, que se ha tomado como referencia, y en el caso de la perovskita negra sus valores SRI muy bajos (SRI=0 en el caso del polvo) y asociados a altos valores de emisividad en el infrarrojo medio la hacen interesante como pigmento para sustratos absorbentes en colectores solares. La capacidad fotocatalítica sobre NaranjaII indica valores de periodo de semivida en torno a 55-70min, inferiores a los medidos en los circones de referencia (110-190min).
[en] In this communication we present a theoretical study of chemical reactions in a system of solid particles, immersed in a fluid environment. Our primary concern here is investigation of the systems of catalytic particles in a liquid media; however with some slight modifications our results are applicable to aerosol systems as well. We consider a second-order reaction, which proceeds both homogeneously in the environment, and heterogeneously at surfaces of catalyst particles. The Langmuir adsorption-desorption kinetics is considered explicitly. For definiteness, we are considering the so-called 'three-step mechanism' of the heterogeneous reaction.
[en] Microcystins (MCs) is a kind of hepatotoxin, which is the secondary metabolite of cyanobacteria. Bi2O2CO3 (BOC) is a kind of cheap and nontoxic semiconductor material. BOC was synthetized by solvothermal method and then microcystin-LR (MC-LR) and microcystin-RR (MC-RR) were removed by BOC, through adsorption and photocatalytic degradation. When the dosage of BOC is 6 g/L, the MC-LR and MC-RR in the natural water sample can be completely adsorbed in 30 min and then after 12 h irradiation, MC-LR and MC-RR were photocatalytically degraded by BOC.
[en] Highlights: → We review the current status of catalytic and non-catalytic VOC abatement based on a vast number of research papers. → The underlying mechanisms of plasma-catalysis for VOC abatement are discussed. → Critical process parameters that determine the influent are discussed and compared. - Abstract: This paper reviews recent achievements and the current status of non-thermal plasma (NTP) technology for the abatement of volatile organic compounds (VOCs). Many reactor configurations have been developed to generate a NTP at atmospheric pressure. Therefore in this review article, the principles of generating NTPs are outlined. Further on, this paper is divided in two equally important parts: plasma-alone and plasma-catalytic systems. Combination of NTP with heterogeneous catalysis has attracted increased attention in order to overcome the weaknesses of plasma-alone systems. An overview is given of the present understanding of the mechanisms involved in plasma-catalytic processes. In both parts (plasma-alone systems and plasma-catalysis), literature on the abatement of VOCs is reviewed in close detail. Special attention is given to the influence of critical process parameters on the removal process.