Catalytic behavior of chromium oxide supported on nanocasting-prepared mesoporous alumina in dehydrogenation of propane

Mesoporous alumina with narrow pore size distribution centered in the range of 4.4–5.0 nm and with a specific surface area as high as 270 m2·g−1 was prepared via the nanocasting approach using a CMK-3 carbon replica as a hard template. Based on this support, a series of catalysts containing 1, 5, 10, 20 and 30 wt % of chromium was prepared by incipient wetness impregnation, characterized, and studied in the dehydrogenation of propane to propene (PDH). Cr species in three oxidation states—Cr(III), Cr(V) and Cr(VI)—were found on the oxidized surface of the catalysts. The concentration of these species varied with the total Cr loading. Temperature-programmed reduction (H2-TPR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRS) studies revealed that Cr(VI) species dominated at the lowest Cr content. An increase in the Cr loading resulted in an appearance of an increasing amount of Cr(III) oxide. UV-Vis-DRS measurements performed in situ during the PDH process showed that at the beginning of the catalytic test Cr(VI) species were reduced to Cr(III) redox species. A crucial role of the redox species in the PDH process over the catalysts with the low Cr content was confirmed. The stability test for the catalyst containing 20 wt % of Cr showed that this sample exhibited the reproducible catalytic performance after the first four regeneration–dehydrogenation cycles. Moreover, this catalyst had higher resistance on deactivation during the PDH process as compared to the reference catalyst with the same Cr loading, but was supported on commercially available alumina

Application of krypton and nitrogen isotherms to characterisation of hydrophobized fine dispersional limestone material

The knowledge about the sorptive character of porous materials is important during their manufacturing, checking their quality and exploitation. In the case of hydrophobized materials such characterisation may be useful not only for description of porous structure but also for measurement of their hydrophobization degree. Two grain fractions of fine dispersional limestone of grain diameter in accordance with the manufacturer's data (Limestone Mine Czatkowice) equals less than 80 mu m for lime meal and 100-400 mu m for lime sand were investigated. The techniques of limestone powder hydrophobization were carried out in apparatuses of own design and are described in previous works of authors (Vogt, Opaliski, Chem. Engineer. Trans. 17:1711-1716, 2009; Vogt, Pol. J. Environ. Stud. 20:801-804, 2011; Vogt, Pol. J. Chem. Technol. 10:49-51, 2008; Buczek, Vogt, Polish Patent. PL 396668, 2013). All modified samples acquired the hydrophobic character but hydrophobic degree of materials was measured with the use of various techniques, therefore it was difficult to compare obtained results. It is the reason why the authors used the adsorption measurements as a method to characterize the hydrophobic properties of materials. In the adsorption measurement two gases: nitrogen and krypton were used as adsorbats. The adsorption isotherms were determined for both raw and modified by commercial modifiers (stearic acid, silicone preparation and bituminous preparation) fine dispersional limestone material. The volume of pores, specific surface area were calculated from the experimental adsorption isotherms (Rouquerol et al., Adsorption by powders and porous solids, Academic press, London, 1999; Gregg, Sing, Adsorption, Surface Area and Porosity, Academic Press, London, 1982). The adsorption value obtained for hydrophobized materials is generally lower than for raw materials. Obtained results enable us to make characterization of the fine dispersional limestone after the hydrophobization process. Regardless of the gas (nitrogen or krypton) used the adsorption value obtained for hydrophobized materials is in principle lower than for raw materials. However, it is more important that the mutual position of the isotherms obtained for materials modified with the use of individual modifiers is the same for both used adsorbs, krypton and nitrogen. This fact makes it possible to determine the degree of hydrophobization of the lime material modified with the use of various modifiers.Web of Science25348347

Maternal Inheritance in Hybrids of Three Honey Bee Subspecies

The identification of honey bee (Apis mellifera) subspecies is often based on the measurements of workers’ fore-wings. The interpretation of the measurements can be difficult because the phenotype of workers is affected by both genetic and environmental factors. Moreover, it is not clear how the phenotype is affected by maternal inheritance. We have used the methodology of geometric morphometrics to verify if hybrids of honey bee subspecies and their backcrosses are more similar to either the father or mother colony. The comparison was based on fore-wing venation of three honey bee subspecies: A. m. carnica, A. m. caucasica, A. m. mellifera. First generation hybrids and backcrosses of those subspecies were obtained through instrumental insemination. Workers of the hybrids were compared with their parental colonies. The shape of wing venation was more similar to the maternal than to parental colony. This phenomenon was particularly visible in first generation of hybrids but it was also present in backcrosses. There were also symptoms of genetic dominance of some subspecies but this effect interacted with maternal inheritance and was difficult to interpret

Municipal Sewage Sludge as a Source for Obtaining Efficient Biosorbents: Analysis of Pyrolysis Products and Adsorption Tests

In the 21st century, the development of industry and population growth have significantly increased the amount of sewage sludge produced. It is a by-product of wastewater treatment, which requires appropriate management due to biological and chemical hazards, as well as several legal regulations. The pyrolysis of sewage sludge to biochar can become an effective way to neutralise and use waste. Tests were carried out to determine the effect of pyrolysis conditions, such as time and temperature, on the properties and composition of the products obtained and the sorption capacity of the generated biochar. Fourier transform infrared analysis (FTIR) showed that the main components of the produced gas phase were CO2, CO, CH4 and to a lesser extent volatile organic compounds. In tar, compounds of mainly anthropogenic origin were identified using gas chromatography mass spectrometry (GC-MS). The efficiency of obtaining biochars ranged from 44% to 50%. An increase in the pyrolysis temperature resulted in a decreased amount of biochar produced while improving its physicochemical properties. The biochar obtained at high temperatures showed the good adsorption capacity of Cu2+ (26 mg·g−1) and Zn2+ (21 mg·g−1) cations, which indicates that it can compete with similar sorbents. Adsorption of Cu2+ and Zn2+ proceeded according to the pseudo-second-order kinetic model and the Langmuir isotherm model. The biosorbent obtained from sewage sludge can be successfully used for the separation of metal cations from water and technological wastewater or be the basis for producing modified and mixed carbon sorbents