Activation and Deactivation of Gold/Ceria–Zirconia in the Low‐Temperature Water–Gas Shift Reaction

Gold (Au) on ceria–zirconia is one of the most active catalysts for the low‐temperature water–gas shift reaction (LTS), a key stage of upgrading H₂ reformate streams for fuel cells. However, this catalyst rapidly deactivates on‐stream and the deactivation mechanism remains unclear. Using stop–start scanning transmission electron microscopy to follow the exact same area of the sample at different stages of the LTS reaction, as well as complementary X‐ray photoelectron spectroscopy, we observed the activation and deactivation of the catalyst at various stages. During the heating of the catalyst to reaction temperature, we observed the formation of small Au nanoparticles (NPs; 1–2 nm) from subnanometer Au species. These NPs were then seen to agglomerate further over 48 h on‐stream, and most rapidly in the first 5 h when the highest rate of deactivation was observed. These findings suggest that the primary deactivation process consists of the loss of active sites through the agglomeration and possible dewetting of Au NPs.     

Ceria–Zirconia Nanoparticles as an Enhanced Multi‐Antioxidant for Sepsis Treatment

The two oxidation states of ceria nanoparticles, Ce³⁺ and Ce⁴⁺, play a pivotal role in scavenging reactive oxygen species (ROS). In particular, Ce³⁺ is largely responsible for removing O₂⁻ and ^.OH that are associated with inflammatory response and cell death. The synthesis is reported of 2 nm ceria–zirconia nanoparticles (CZ NPs) that possess a higher Ce³⁺/Ce⁴⁺ ratio and faster conversion from Ce⁴⁺ to Ce³⁺ than those exhibited by ceria nanoparticles. The obtained Ce_0.7Zr_0.3O₂ (7CZ) NPs greatly improve ROS scavenging performance, thus regulating inflammatory cells in a very low dose. Moreover, 7CZ NPs are demonstrated to be effective in reducing mortality and systemic inflammation in two representative sepsis models. These findings suggest that 7CZ NPs have the potential as a therapeutic nanomedicine for treating ROS‐related inflammatory diseases.     

Nanostructured Copper Oxide on Silica–Zirconia Mixed Oxides by Chemical Implantation

A new route to chemical implantation of copper(II) N,N‐dialkylcarbamato complexes on silica and nanostructured silica–zirconia matrices and subsequent thermal treatment (see scheme) is an efficient method of functionalizing the oxide matrices with nanostructured CuO. The materials have been characterized thoroughly and the effect of selected experimental parameters on the grafting reaction was investigated.

     

Conversion of Methane into Methanol and Ethanol over Nickel Oxide on Ceria–Zirconia Catalysts in a Single Reactor

The conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value‐added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria–zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady‐state process at 723 K using O₂ as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO₂ as the product of catalytic combustion. The unusual activity of this catalyst is attributed to the synergy between the small Lewis acidic NiO clusters and the redox‐active CZ support, which also stabilizes the small NiO clusters.     

Ceria–Zirconia Particles Wrapped in a 2D Carbon Envelope: Improved Low‐Temperature Oxygen Transfer and Oxidation Activity

Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria‐based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high‐energy milling of CeO₂–ZrO₂ powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria‐zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities.     

Boc–Pro–Hyp–Gly–OBzl and Boc–Ala–Hyp–Gly–OBzl,two repeating triplets found in collagen

The protected tripeptides benzyl N‐{2‐[N‐(tert‐butoxy­carbon­yl)­prol­yl]‐4‐hydroxy­prol­yl}glycinate or Boc–Pro–Hyp–Gly–OBzl, C₂₄H₃₃N₃O₇, and benzyl N‐{2‐[N‐(tert‐butoxy­carbon­yl)­alan­yl]‐4‐hydroxy­prol­yl}glycinate or Boc–Ala–Hyp–Gly–OBzl, C₂₂H₃₁N₃O₇, are the minimum repeating triplets found in collagen. Within the crystal structure of each are two independent peptide mol­ecules with similar structures. The peptides are arranged anti­parallel to one another and inter­act through hydrogen bonds involving the main chains and the 4‐hydroxy­prolyl groups. The structures exhibit characteristics of a triple helix, but the peptides tend to assume a sheet‐like structure.     

Two-Dimensional Sol-Gel Synthesis of Ultrathin Zirconia and Hetero-Layered Titania/Zirconia Films

Synthesis of ZrO₂ and hetero-layered TiO₂/ZrO₂ ultrathin films was investigated by two-dimensional sol-gel process assisted by n-octadecylacetoacetate (C₁₈AA). When a hexane solution of tetrabutoxyzirconium (TBZ) and C₁₈AA was spread on the water surface, Zr-based gel films stabilized with C₁₈AA were formed at the air/water interface. After deposition on substrates, the gel films were successfully transformed into ZrO₂ ultrathin films by heating at 773 K for 0.5 h, the thickness of which was controllable on the order of sub-nanometer level by the number of gel-layer deposition and the molar ratio of [TBZ]/[C₁₈AA]. Well-organized hetero-multilayers composed of ultrathin TiO₂ and ZrO₂ layers could be fabricated by the alternate deposition of C₁₈AA-stabilized Ti- and Zr-gel films.     

Metastable liquid–liquid and solid–liquid phase boundaries in polymer–solvent–nonsolvent systems

In general liquid–liquid demixing processes are responsible for the porous morphology of membranes obtained by immersion precipitation. For rapidly crystallizing polymers, solid–liquid demixing processes also generate porous morphologies. In this study, the interference of both phase transitions has been analyzed theoretically using the Flory–Huggins theory for ternary polymer solutions. It is demonstrated that four main thermodynamic and kinetic parameters are important for the structure formation in solution: the thermodynamic driving force for crystallization, the ratio of the molar volumes of the solvent and the nonsolvent, the polymer–solvent interaction parameter, and the rate of crystallization of the polymer compared to the rate of solvent-nonsolvent exchange. An analysis of the relevance of each of these parameters for the membrane morphology is presented. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 763–770, 1997     

Thermal Plasma Synthesis of Zirconia Powder and Preparation of Premixed Ca-Doped Zirconia

A novel study about the synthesis of zirconia and calcia-stabilized zirconia powders were carried out by DC thermal plasma starting from cheap precursors as the carbonates. Different operational parameters were investigated to explore the effects of the process conditions, such as the plasma torch power and the gas flow rate on the composition and the morphology of the powders. The products phase changes from a metastable tetragonal to monoclinic/tetragonal mixture. Basically a main tetragonal phase was obtained at low torch power (7 kW) while the amount of monoclinic phase linearly rises with the power, up to 66 wt% at 26 kW of plasma power and high gas flow rate. The gas flow rate also affects the shape and the size of the powder, where high values reduce powder aggregation and enhance the spherical shape. The best results were achieved at 22 kW of plasma power and high gas flow rate, with powders of roundness about 79% and a wide particle size distribution. Adding the calcium carbonate to the zirconium carbonate (corresponding to 8 wt% CaO in the final mixture), the plasma treatment mainly produces a tetragonal phase zirconia, that at 1400 °C in furnace changes in a stable cubic phase. These powders could be made suitable for further industrial applications after proper treatments.

     

1H and 13C NMR study of phosphopeptides: 2—Ac–PSer–Gly,Ala–PSer–Gly and Gly–PSer–Phe

¹H and ¹³C NMR spectra of AC–PSer–Gly, Ala–PSer–Gly and Gly–PSer–Phe have been measured and analysed as a function of pD. The NMR parameters of the PSeryl side chain are a function of the sequence. The second titration step of the phosphate group (pK₂ = 5.7) is much more difficult to detect in Ac–PSer–Gly and Ala–PSer–Gly than in Gly–PSer–Phe. The conformation in which H-α? C-α? C-β? O? P forms a planar W-type arrangement predominates only for Ala–PSer–Gly. In the other two phosphopeptides the gauche conformations contribute increasingly, in particular for Gly–PSer–Phe.     

Synthesis,Crystal Structure,and Ultraviolet–Visible Spectrum of 8–Substituted–10,10–Dimethyl–10H–pyrido[1,2–a]indolium Perchlorates–Containing Thienyl Moiety

Two novel compounds, 8–[2–(2–thienyl)vinyl]–10,10–dimethyl–10H–pyrido[1,2–a] indolium perchlorate ( 3a ) and 8–[2–(5–phenyl–2–thienyl)vinyl]–10,10–dimethyl–10H–pyrido[1,2–a]indolium perchlorate ( 3b ) were synthesized and characterized by IR, ¹H–NMR, elemental analyses, and X–ray diffraction. Crystal structural analysis suggested that either 3a or 3b exhibited good coplanarity and rings and vinyl in the target molecule could make up a large conjugated system. Ultraviolet–visible absorption analysis indicated both 3a and 3b possessed large maximum absorptions, and 3b underwent a significant redshift (43.0 nm) in comparison with 3a .     

Synthesis and Reactivity of 2,2,4,4–Tetrakis(tri–tert–butoxysilanethiolato)–1,3,2,4–dithiadistannetane – Crystal and Molecular Structures of Two Polymorphic Forms

The title compound, [Sn(μ–S){SSi(O^tBu)₃}₂]₂ ( 1 ), containing four–coordinated tin(IV), crystallizes in two polymorphic modifications. The orthorhombic 1a –form has been obtained in the reaction of (^tBuO)₃SiSH and Et₃N with SnCl₂, whereas the triclinic 1b –form in the reaction with SnCl₄ as substrate. The crystal and molecular structures of both polymorphs ( 1a as a redetermination) have been determined by a single–crystal X–ray diffraction study at room temperature. The title compound was shown to react with ammonia and ammonia complexes of some d–block metal cations giving products of Sn–S bond cleavage.     

S2O2-8和SO2-4促进ZrO2固体超强酸正戊烷反应性能差异的研究

考察了常温下S2O2-8促进ZrO2(PSZ)固体超强酸催化剂上正戊烷的反应性能,并与SO2-4促进ZrO2(SZ)反应相比较,观察到PSZ和SZ对正戊烷都具有异构化和裂解的双重作用,主要产物分别为异戊烷和异丁烷.正戊烷的异构化转化率和表观反应速率常数主要取决于样品的焙烧温度.但对于正戊烷异构化反应,PSZ的最佳焙烧温度为550℃,比SZ的低50℃.在各自的最佳焙烧温度下反应1h后,前者的异戊烷生成率为后者的1.3倍.通过S含量和比表面积测定以及用XRD和FTIR等手段分析了PSZ的物理化学特性.从原位FTIR谱图发现,PSZ(550℃)表面S-O键的红外吸收明显比SZ(600℃)的强;通过吡啶红外手段发现PSZ(550℃)吡啶离子吸收峰的红移大于SZ(600℃),表明前者的Lewis酸强于后者.     

S2O8^2—和SO4^2—促进ZrO2固体超强酸正戊烷反应性能差异的研究

考察了常温下S2O8^2-促进ZrO2(PSZ)固体超强酸催化剂上正戊烷的反应性能，并与SO4^2-促进ZrO2（SZ）反应相比较，观察到PSZ和SZ对正戊烷都具有异构化和裂解的双重作用，主要产物分别为异戊烷和异丁烷。正戊烷的异构化转化率和表观反应速率常数主要取决于样品的焙烧温度。但对于正戊烷异构化反应，PSZ的最佳焙烧温度为550℃，比SZ的低50℃。在各自的最佳焙烧温度下反应1h后，前者的异戊烷生成率为后者的1．3倍。通过S含量和比表面积测定以及用XRD和FTIR等手段分析了PSZ的物理化学特性。从原位FTIR谱图发现，PSZ（550℃）表面S－O键的红外吸收明显比SZ（600℃）的强；通过吡啶红外手段发现PSZ（550℃）吡啶离子吸收峰的红移大于SZ（600℃），表明前者的Lewis酸强于后者。