Schnell-Methode zur Umsetzung von Kohlenwasserstoffen zu Wasserstoff für die Isotopenanalyse

Es wird eine weiterentwickeltes, isotopenanalytisches Verfahren zur probenchemischen Umsetzung von Kohlenwasserstoffen mit Chromium zu Wasserstoff bei 1300 K vorgestellt. Die erzielten Testergebnisse zeigen anhand der gemessenen δD-Werte, daβ Quarzöfen bei diesen Temperaturen noch keine die Isotopenmeβwerte beeinflussende Diffusion von Wasserstoff durch die Wandung zulassen. Auβerdem erfolgte die Reaktion nahezu spontan und vollständig, was die Methode zeitlich sehr effektiv macht.

A modified isotope analytical method is presented for the chemical reaction of hydrocarbons with chromium at 1300 K to form hydrogen. The test results obtained (i.e. the measured δD-values) show that at this temperature quartz heating tubes do not allow hydrogen to diffuse through the wail, which fact would influence the isotopic composition. Furthermore the reaction proceeds nearly spontaneously and quantitatively, which yields an effective method, especially with respect to time.     

Langmuir-Blodgett self-assembly and electrochemical catalytic property of FePt magnetic nano-monolayer

Dispersed-well FePt nanoparticles with particle size ~5 nm have been prepared by hydrazine hydrate reduction of H₂PtCl₆·6H₂O and FeCl₂·4H₂O in ethanol–water system. By employing as-synthesized FePt nanoparticles, the monolayer can be formed by LB Technique. The structural, magnetic properties and electrochemical properties of FePt monolayer were respectively studied by XRD, TEM, VSM and CHI 820 electrochemical workstation. The as-synthesized particle has a chemically disordered fcc structure and can be transformed into chemically ordered fct structure after annealing treatment above 400°C. The coercivity of ordered fct FePt phase can be up to 2515Oe. CVs of 0.5 M H₂SO₄/0.5M CH₃OH on GCE modified with FePt nanoparticles monolayer films illustrate that the as-synthesized FePt is a kind of active electrochemical catalyst.     

Theoretical study on the catalytic properties of single-atom catalyst stabilised on silicon-doped graphene sheets

ABSTRACT

The stable configurations, electronic structures and catalytic activities of single-atom metal catalyst anchored silicon-doped graphene sheets (3Si-graphene-M, M?=?Ni and Pd) are investigated by using density functional theory calculations. Firstly, the adsorption stability and electronic property of different gas reactants (O₂, CO, 2CO, CO/O₂) on 3Si-graphene-M substrates are comparably analysed. It is found that the coadsorption of O₂/CO or 2CO molecules is more stable than that of the isolated O₂ or CO molecule. Meanwhile, the adsorbed species on 3Si-graphene-Ni sheet are more stable than those on the 3Si-graphene-Pd sheet. Secondly, the possible CO oxidation reactions on the 3Si-graphene-M are investigated through Eley–Rideal (ER), Langmuir–Hinshelwood (LH) and new termolecular Eley–Rideal (TER) mechanisms. Compared with the LH and TER mechanisms, the interaction between 2CO and O₂ molecules (O₂?+?CO → CO₃, CO₃?+?CO → 2CO₂) through ER reactions (< 0.2?eV) are an energetically more favourable. These results provide important reference for understanding the catalytic mechanism for CO oxidation on graphene-based catalyst.     

Microwave-assisted synthesis of SrFe12O19 hexaferrites

Ultra-fine and homogeneous SrFe₁₂O₁₉ hexaferrites were synthesized by a microwave-assisted calcination route. The calcined precursors were prepared by a sol-gel auto-combustion method using Fe(NO₃)₃·9H₂O, Sr(NO₃)₂ and citric acid as starting materials. The structures, powder morphology and magnetic properties of the products were characterized by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. The results showed that microwaves are helpful to reduce the calcination temperature and shorten the calcination time. The ferrites with saturation magnetization, remanence and intrinsic coercivity of 54.80 emu/g, 29.52 emu/g and 5261 Oe, respectively, were obtained in samples calcined at 800 °C for 80 min.     

A facile and eco-friendly approach for preparation of microkeratin and nanokeratin by ultrasound-assisted enzymatic hydrolysis

Protein is one of the most abundant natural polymeric materials, but only a few studies on nanoproteins have been conducted. In this paper, a novel approach based on ultrasound-assisted enzymatic hydrolysis was employed for the preparation of microkeratin and nanokeratin from wool. The hydrolysis system included a solution containing enzyme (esperase) and reductant (L-cysteine) and treated ultrasonically to remove the scales and amorphous regions within wool. Results showed that the reaction was most effective at 50 °C and pH 7, when incubated for 3 h, followed by sonication for 6 h. The products included spindle-shaped microkeratin (4–7 μm in diameter and 70–120 μm in length) and cone-shaped nanokeratin (50–300 nm in diameter and less than 15 μm in length). Under ultrasonic-assisted conditions, the yields of microkeratin and nanokeratin increased significantly, while the treatment time decreased. Fourier transform infrared spectroscopy (FTIR) showed that the chemical structures of microkeratin and nanokeratin did not change, compared to that of wool. X-ray diffraction (XRD) analysis showed that the microkeratin was mainly composed of α-helical structure, while the β-sheet structure was more prevalent in nanokeratin. The presented method is facile and eco-friendly, thereby paving new pathways for the preparation of microkeratin and nanokeratin.     

Enhancing hydrogen evolution of MoS2 basal planes by combining single-boron catalyst and compressive strain

MoS₂ is a promising candidate for hydrogen evolution reaction (HER), while its active sites are mainly distributed on the edge sites rather than the basal plane sites. Herein, a strategy to overcome the inertness of the MoS₂ basal surface and achieve high HER activity by combining single-boron catalyst and compressive strain was reported through density functional theory (DFT) computations. The ab initio molecular dynamics (AIMD) simulation on B@MoS₂ suggests high thermodynamic and kinetic stability. We found that the rather strong adsorption of hydrogen by B@MoS₂ can be alleviated by stress engineering. The optimal stress of −7% can achieve a nearly zero value of ΔG_H (~ −0.084 eV), which is close to that of the ideal Pt–SACs for HER. The novel HER activity is attributed to (i) the B– doping brings the active site to the basal plane of MoS₂ and reduces the band-gap, thereby increasing the conductivity; (ii) the compressive stress regulates the number of charge transfer between (H)–(B)–(MoS₂), weakening the adsorption energy of hydrogen on B@MoS₂. Moreover, we constructed a SiN/B@MoS₂ heterojunction, which introduces an 8.6% compressive stress for B@MoS₂ and yields an ideal ΔGH. This work provides an effective means to achieve high intrinsic HER activity for MoS₂.     

SO_4~(2-)_ZrO_2-TiO_2催化剂的制备及性能

本文用三种不同的方法制备了SO_4~(2-)/ZrO_(2-)TiO_2催化剂,并用Caro Eala自动吸附仪、PE683型红外光谱仪及LCT-2型高温差热天平仪分别有选择地测定了催化剂比表面及催化剂表面硫酸根的红外吸收光谱、脱附量、脱附温度,还测定了对酯化反应的催化性能。同时,讨论了制备条件和方式对催化剂性能的影响。     

磷钼酸四氢三铵的制备及其交换性能

磷钼酸四氢三铵的制备及其交换性能臧二乐，梁树权（北京农业大学应用化学系北京１０００９４）（中国院学院化学研究所北京）关键词磷钼酸四氢三铵，制备，离子交换性能通式为Ｍ＿ｎＸＹ＿（１２）Ｏ＿（４０）·ｐＨ＿２Ｏ（其中Ｍ为一价阳离子；Ｘ为Ｐ、Ａｓ、Ｓｉ、Ｇ...     

二甲苯在TFJF型催化剂上深度氧化动力学的研究

在193-225 iC温度范围内，在轴向取样的管式积分反应器中研究了二甲苯在TFJF型催化剂上深度氧化的宏观动力学，在试验条件下，该反应的速度方程为: