Modifying the structure of red mud by simple treatments for high and stable performance in COx-free hydrogen production from ammonia

Red mud (RM) modified by various treatments was used as a catalyst for ammonia decomposition. Catalytic activity measurements performed at 500 °C and differential conversions illustrated that the rate increases with a decrease in the size of Fe₃N_y nanoparticles formed during activation in NH₃ flow. Measurements at 700 °C showed that a catalyst prepared by digesting RM in 6 M HCl followed by calcination at 900 °C provides a stable ammonia conversion of 98.8 ± 0.5% for more than 70 h at a space velocity of 120 000 cm³ NH₃ h^?1 g_cat^?1. This rate is premier among all iron-based catalysts in terms of both activity and stability and even on par with the performance of other non-noble metal catalysts. Detailed characterization indicated Fe₃N_y species readily available on the surface as the active species. Results provided here enable the utilization of RM as an environmentally-friendly, highly efficient, and almost cost-free catalyst for CO_x-free hydrogen production.     

Study of intrinsic sulfidation behavior of Fe2O3 for high temperature H2S removal

Iron-based sorbent was preferable for desulfurization from coal-derived gas due to economic consideration and favorable dynamic property. The intrinsic behavior of Fe-based sorbent should be primarily understood in the sulfidation process for improving its performance. A series of tests were carried out with Fe₂O₃, Fe and other compounds containing-Fe (FO) made from the same precursor FeC₂O₄·2H₂O in H₂S-N₂ mixture in this study. The formation of H₂ was observed with Fe and FO as sorbents. While SO₂ was detected with FO and Fe₂O₃ as sorbents, its concentration in outlet was gradually decreased. The crystal phase and surface chemical state of fresh and sulfided Fe₂O₃ with different reaction times were characterized by XRD and XPS measurements. The result suggested that the intrinsic H₂S removal by Fe₂O₃ would produce multi-phase of sulfides. The possible mechanism of sulfidation reaction was discussed.     

Pairing insights in iron-based superconductors from scanning tunneling microscopy

Scanning tunneling microscopy (STM) has made tremendous progress in the study and understanding of both classical and unconventional superconductors. This has motivated a rapidly growing effort to apply the same techniques to the iron-based high-T_c superconductors since their discovery in 2008. Five years have brought exciting advances in imaging and spectroscopic investigation of this new class of materials. In this review, we focus on several recent STM contributions to the identification of the gap symmetry and pairing glue. We highlight the unique capabilities and challenges still ahead for STM studies of iron-based superconductors.     

一种吡啶二亚胺类铁催化剂的合成及乙烯齐聚研究

通过控制合成三齿吡啶亚胺配体的反应条件及所用的催化剂的不同,使得到配体的产率在80％以上,并与亚铁盐络合得到一种铁系催化剂.以甲苯为溶剂,甲基铝氧烷(MAO)为助催化剂,催化乙烯齐聚合成线性α-烯烃.催化剂表现出高活性和对α-烯烃的高选择性.考察了反应温度、Al/Fe 摩尔比和反应压力等因素对催化活性和齐聚产物分布的影响.     

Mechanism study of iron-based catalysts in co-liquefaction of coal with waste plastics

The state and active site of iron-based catalysts in co-liquefaction of coal with low-density polyethylene (LDPE) have been discussed. The catalysts used were sulfur-promoted iron oxides (Fe₂O₃+S), ferrous sulfide (FeS), ferrous sulfate (FeSO₄·7H₂O) and the mineral pyrite (FeS₂). It was found by X-ray photoelectron spectrometry that the active site in the working state of Fe₂O₃+S catalyst was not Fe_1−XS and the main form of sulfur existing in the spent Fe₂O₃+S catalyst was sulfate, followed by sulfite (SO₃²⁻). A finding from autoclave tests was that the ferrous sulfate before and after oxidation treatments showed sufficiently high activity for the co-liquefaction of coal with LDPE. It was concluded that an active site of the iron-based catalysts was sulfate species formed on the catalyst surface during the hydroliquefaction process of coal.     

Synthesis and characterization of syndiotactic 3,4-polyisoprene prepared with diethylbis(2,2′-bipyridine)iron-MAO

The soluble system diethylbis(2,2′-bipyridine)Fe-MAO is very active for the polymerization of isoprene to predominantly 3,4 polymers (ca. 80%). The polymers obtained at 25 °C are amorphous by X-ray examination, while those obtained below 10 °C are crystalline. The identity period determined from the X-ray fiber spectrum, ca. 5.2 Å, and the NMR analysis show that the polymer contains stereoregular sequences of 3,4 syndiotactic structure. An interpretation is given of the effect of polymerization temperature on stereospecificity. Some differences between the 1,2 polymerization of butadiene and the 3,4 polymerization of isoprene are examined.     

Vanadium removal by metal (hydr)oxide adsorbents

Vanadium is listed on the United States Environment Protection Agency (USEPA) candidate contaminant list # 2 (CCL2), and regulatory guidelines for vanadium exist in some US states. The USEPA requires treatability studies before making regulatory decisions on CCL2 contaminants. Previous studies have examined vanadium adsorption onto some metal hydroxides but not onto commercially available adsorbents. This paper briefly summarizes known vanadium occurrence in North American groundwater and assesses vanadium removal by three commercially available metal oxide adsorbents with different mineralogies. GTO (Dow) is TiO2 based and E-33 (Seven Trents) and GFH (US Filter) are iron based. Preliminary vanadate adsorption kinetics onto GFH, E-33 and GTO has been studied and the homogenous surface diffusion model (HSDM) is used to describe the adsorption kinetics data. The effects of pH, vanadium concentration, and volume/mass ratio are assessed. Vanadium adsorption decreases with increasing pH, with maximum adsorption capacities achieved in at pH 3-4. Results indicate that all adsorbents remove vanadium; GFH has the highest adsorption capacity, followed by GTO and E-33. Data are best fit with the Langmuir model rather than Freundlich isotherms. Both the sorption maxima (Xm) and binding energy constant (b) follow the trend GFH>GTO>E-33. Naturally occurring vanadium is also removed from Arizona ground water in rapid small-scale column tests (RSSCTs). Metal oxide adsorption technologies currently used for arsenic removal may also remove vanadium but not always with the same effectiveness.     

高铬铁基熔体中磷和铬的热力学性质的研究

通过Fe－Cr－C系中碳的溶解平衡实验和铝、磷在BaO－BaCl2渣和Fe－Cr－C—P系间的分配平衡实验，心别测定11723K时三元系中碳的溶解度和个街时铬、磷在渣余间的浓度关系根据实验结果，应用热力学理论求得了和，并提出厂适用于高铬含碳铁基熔体中格和磷的活度系数计算式     

A novel dual phase BaCe0.5Fe0.5O3-δ cathode with high oxygen electrocatalysis activity for intermediate temperature solid oxide fuel cells

A novel iron-based perovskite BaCe_0.5Fe_0.5O_3-δ (BCF) powders were successfully fabricated and the phase composition, lattice structure, oxygen surface exchange coefficient and electrochemical performance were investigated. The ultrafine BCF powder with grain size of about 200 nm consisted of dual phase BaCe_0.15Fe_0.85O_3-δ and BaCe_0.85Fe_0.15O_3-δ. Electrical conductivity relaxation measurement illustrates the low conductivity activation energy and the high oxygen surface exchange kinetics with oxygen surface exchange coefficient of 3.8 × 10⁻⁵ cms⁻¹ at 600 °C. BCF cathode exhibits 1.04 Ωcm² on doped ceria electrolyte and remains stable in 400 h long term test at 600 °C. A single cell based on doped ceria electrolyte with BCF cathode shows a maximum power density of 228 mW cm⁻² at 650 °C. The preliminary results indicate that the dual phase BCF can be applied as cathode material for oxygen ion conductive solid oxide fuel cells.     

Photoinduced Quasiparticle Relaxation Dynamics in Near-optimally Doped SmFeAsO0.8F0.2 Single Crystals

We investigate the quasiparticle relaxation and low-energy electronic structure in a near-optimally doped pnictide superconductor with T _c=49.5 K by means of femtosecond spectroscopy. Multiple relaxation processes are evident, with distinct superconducting state dynamics and a clear “pseudogap”-like feature with an onset above 180 K indicating the existence of a temperature-independent gap of magnitude Δ _PG=61±9 meV above and below T _c. The fluence and temperature dependence of the superconducting state dynamics shows similar behaviour to the cuprate superconductors with the superconducting-condensate vaporization energy of E _va/k _B≈1.5 K per Fe ion.