Effect of Gas Atmosphere on Catalytic Behaviour of Zirconia, Ceria and Ceria Zirconia Catalysts in Valeric Acid Ketonization

[EN] Ketonization of valeric acid, which can be obtained by lignocellulosic biomass conversion, was carried out in a fixed bed flow reactor over ZrO2, 5-20 % CeO2/ZrO2 and CeO2 both under hydrogen and nitrogen stream at 628 K and atmospheric pressure. Regardless gas-carrier 10 wt% CeO2/ZrO2 was found to show higher catalytic activity compared to zirconia per se as well as other ceria modified zirconia while ceria per se exhibited very low catalytic activity. All catalysts provided higher acid conversion in H-2 than in N-2 whereas selectivity to 5-nonanone was insensitive to gas atmosphere. XRD, FTIR, UV-Vis DRS, XPS, HRTEM methods were applied to characterize catalysts in reduced and unreduced states simulating corresponding reaction conditions during acid ketonization. XRD did not reveal any changes in zirconia and ceria/zirconia lattice parameters as well as crystalline phase depending on gas atmosphere while insertion of ceria in zirconia caused notable increase in lattice parameter indicating some distortion of crystalline structure. According to XPS, FTIR and UV-Vis methods, the carrier gas was found to affect catalyst surface composition leading to alteration in Lewis acid sites ratio. Appearance of Zr3+ cations was observed on the ZrO2 surface after hydrogen pretreatment whereas only Zr4+ cations were determined using nitrogen as a gas-carrier. These changes of catalyst's surface cation composition affected corresponding activity in ketonization probably being crucial for reaction mechanism involving metal cations catalytic centers for acid adsorption and COO- stabilization at the initial step.Financial support from the Russian Foundation of Basic Research (RFBR Grant No 11-03-94001-CSIC) is gratefully acknowledged. This work was supported by the Federal Program "Scientific and Educational Cadres of Russia'' (Grant No 2012-1.5-12-000-1013-002). The authors also wish to thank Dr. Evgeniy Gerasimov, Dr. Igor Prosvirin, Dr. Demid Demidov from the Department of Physicochemical Methods at the Boreskov Institute of Catalysis for TEM and XPS measurements.Zaytseva, YA.; Panchenko, VN.; Simonov, MN.; Shutilov, AA.; Zenkovets, GA.; Renz, M.; Simakova, IL.... (2013). Effect of Gas Atmosphere on Catalytic Behaviour of Zirconia, Ceria and Ceria Zirconia Catalysts in Valeric Acid Ketonization. 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Superconducting cuprates of the series Bi₂Ca_1-xLn_xSr₂Cu₂O_{8+ δ} (Ln = rare earth or Y)

A systematic investigation of the properties of the series Bi2Ca1-xLnxSr2Cu2O8+ δ (Ln-rare earth or Y) of superconducting cuprates has been carried out by employing a variety of techniques. In these cuprates, the a and b parameters of the unit cell increase with x while the c parameter decreases. These cuprates show interesting superlattice modulation with both 4b and 8b periodicity depending on the rare earth when x=1.0. This observation suggests that the superlattice modulation has nothing to do with superconductivity, but may be determined by the oxygen stoichiometry. The oxygen excess, delta , increases linearly with x, but the hole concentration shows a maximum around x = 0.25 or delta approximately = 0.225+or-0.025. Interestingly, Tc also shows a maximum around x = 0.25. The authors have examined the nature of copper by XANES and Cu core level spectra. The relative intensity of the satellite in the Cu(2p) spectrum shows a minimum at x = 0.25. The Raman band around 630 cm-1 due to the oxygen atoms in Bi-O layers decreases with increase in x, as does the a parameter

Superconducting cuprates of the series Bi<SUB>2</SUB>Ca<SUB>1-x</SUB>Ln<SUB>x</SUB>Sr<SUB>2</SUB>Cu<SUB>2</SUB>O<SUB>8+&#948;</SUB> (Ln=rare earth or Y)

A systematic investigation of the properties of the series Bi2Ca1-xLnxSr2Cu2O8+ delta (Ln-rare earth or Y) of superconducting cuprates has been carried out by employing a variety of techniques. In these cuprates, the a and b parameters of the unit cell increase with x while the c parameter decreases. These cuprates show interesting superlattice modulation with both 4b and 8b periodicity depending on the rare earth when x=1.0. This observation suggests that the superlattice modulation has nothing to do with superconductivity, but may be determined by the oxygen stoichiometry. The oxygen excess, delta , increases linearly with x, but the hole concentration shows a maximum around x=0.25 or delta approximately=0.225+or-0.025. Interestingly, Tc also shows a maximum around x=0.25. The authors have examined the nature of copper by XANES and Cu core level spectra. The relative intensity of the satellite in the Cu(2p) spectrum shows a minimum at x=0.25. The Raman band around 630 cm-1 due to the oxygen atoms in Bi-O layers decreases with increase in x, as does the a parameter

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The immune system was identified as a protective factor during infectious diseases over a century ago. Current definitions and textbook information are still largely influenced by these early observations, and the immune system is commonly presented as a defence machinery. However, host defence is only one manifestation of the immune system’s overall function in the maintenance of tissue homeostasis and system integrity. In fact, the immune system is integral part of fundamental physiological processes such as development, reproduction and wound healing, and a close crosstalk between the immune system and other body systems such as metabolism, the central nervous system and the cardiovascular system is evident. Research and medical professionals in an expanding range of areas start to recognise the implications of the immune system in their respective fields. This chapter provides a brief historical perspective on how our understanding of the immune system has evolved from a defence system to an overarching surveillance machinery to maintain tissue integrity. Current perspectives on the non-defence functions of classical immune cells and factors will also be discusse

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