Methane activation without using oxidants over Mo/HZSM-5 zeolite catalysts

The effect of Mo loading, calcination temperature, reaction temperature and space velocity on the catalytic performance of methane dehydrogenation and aromatization without using oxidants over Mo/HZSM-5 has been studied. The XRD and BET measurements show that Mo species are highly dispersed in the channels of the HZSM-5 zeolite, resulting from the interaction between the Mo species and the zeolite, which also leads to a decrease in its crystallinity. The Brønsted acidity, the channel structure and the state and location of Mo species in the zeolite seem to be crucial factors for its catalytic performance. It was found that 2% Mo/HZSM-5 calcined at 773 K showed the best aromatization activity among the tested catalysts, the methane conversion being 9% at 1013 K with the selectivity to aromatics higher than 90%. The experimental results obtained from the variation of space velocity gave evidence that ethylene is an initial product. On the basis of these results a possible mechanism for methane dehydrogenation and aromatization has been proposed in which both the heterolytic splitting of methane in a solid acid environment and a molybdenum carbene-like complex as an intermediate are of significance.     

莠去津的生态毒理学及其环境行为学研究进展

莠去津是世界范围内广泛使用的除草剂,在曾经使用莠去津的地区的水体中均检测到莠去津的残留,由于莠去津属于内分泌干扰物,长期暴露在该有机污染物的环境中,势必对各种生物产生不良影响。介绍了莠去津的生态毒理学研究进展及其环境行为研究的内容和热点,着重评述了莠去津对哺乳动物的各种毒性、在土壤中的吸附机制和迁移以及治理措施。     

PU改性TDE-85/ MeTHPA环氧体系的显微形貌特征研究

本实验选用聚醚二元醇、甲苯二异氰酸酯（TDI）作为原料，合成了聚醚型聚氨酯预聚体。采用该预聚体扩链剂1，4-丁二醇（1，4-BDO）、交联剂三羟甲基丙烷（TMP）对TDE-85／甲基四氢苯酐（MeTHPA）环氧树脂体系行改性。利用扫描电镜分析，探讨了聚氨酯（PU）改性TDE-85／甲基四氢苯酐（MeTHPA）环氧树脂体系结构特征。结果表明，当合成PＵ预聚体的PPG相对分子质量不同时，改性环氧树脂体系的表面形貌随聚氨酯预聚体加入量的变趋势是相同的。当聚氨酯含量较小时，呈明显的“海岛”结构。随着聚氨酯加入量增多到一定量时，两网络互穿程度高，相分离程度不明显，具有互穿网络聚合物结构特征。随着聚氨酯含量的继续增多，相区尺寸明显增大，两相相容变差，相界面变得较清晰。     

Preparation and characterization of calcium carbonate/low‐density‐polyethylene nanocomposites

Calcium carbonate/low‐density‐polyethylene (LDPE) nanocomposites have been prepared by melting blend with twin‐screw extruder. The mechanical properties of composites and the dispersion of the nanoparticles were studied. The reinforcement mechanism was discussed. The results show that not only the tensile property but also the flexural modulus of the system have been evidently increased by the addition of calcium carbonate. The calcium carbonate particles have been dispersed in the matrix in the nanometer scale. The reinforcement mechanism of the calcium carbonate lies on that the calcium carbonate particles, acting as hetero‐nuclei, can induce higher crystallinity at the matrix‐particle interface compared to regions away from the interface. Consequently, in the process of the tensile test, the nanocomposites have better tensile yield strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

裂解炉对流段二次注汽过热炉管失效原因分析

通过对发生腐蚀穿孔的BA-1104裂解炉对流段二次注汽过热炉管进行了宏观腐蚀形貌分析,对含裂纹部位进行了光学显微镜观察,断口进行扫描电镜观察以及对腐蚀产物的化学成分和金相组织分析,指出造成炉管腐蚀穿孔的决定性因素与操作温度及介质中存在的碱有关。进而提出了腐蚀控制与防范的措施,确保裂解炉的安全运行。     

合成堇青石陶瓷材料的研究进展

概述了堇青石材料的组成、结构、性能特点及应用领域。阐述了堇青石的合成方法以及基本原理，重点介绍了天然矿物原料合成堇青石的研究进展。     

Curing and pyrolysis of cresol novolac epoxy resins containing [2‐(6‐oxido‐6H‐dibenz(c,e)(1,2)oxaphosphorin‐6‐yl)‐1,4‐naphthalenediol]

This study investigates the curing kinetics, thermal properties and decomposition kinetics of cresol novolac epoxy (CNE) with two curing agents, 2‐(6‐oxido‐6H dibenz(c,e)(1,2) oxaphosphorin‐6‐yl)‐1,4‐benzenediol (ODOPN), and phenol novolac (PN). In comparison with the conventional PN system, introducing ODOPN, a phosphorus‐containing bulky pendant group, into CNE increases T_g by 33°C, char yield from 30% to 38%, and LOI from 22 to 31. The DSC curing study reveals that the E_a of the CNE/ODOPN epoxy can be obtained by Kissinger's method. The resulting E_a values indicate that the catalytic effect of EMI is insignificant on CNE/ODOPN but is marked on CNE/PN, whose E_a was reduced from 131.5 to 75.6 KJ/mole. This result may be caused by the fact that the symmetric diol attached to the 1 and 4 positions of the naphthalene ring in ODOPN sets up a steadily resonating structure and inhibits the catalytic action. Further investigating the conversion ratio with curing temperature yielded experimental data that agreed closely with Kaiser's model. The orders of the autocatalyzed reaction, m, and the crosslinking reaction, n, are close to 0.5 and 1.0, respectively, independently of the scan rate. Finally, the TGA decomposition study by Ozawa's method demonstrates that the mean E_a declines with the phosphorus content, because the easy decomposition of the phosphorus compound in the initiation stage facilitates the formation of an insulating layer. However, results in this study further reveal an increasing tendency for E_a with decomposition conversion for an ODOPN/PN mixture with the ODOPN content of over 50%, probably because of the retardation of gas diffusion by the insulating layer of phosphorus compound.     

腐植酸生物活性影响植物根系发育的研究

介绍了腐植酸(HA)对植物根系的刺激作用，并以详实的数据说明三种不同腐植酸、黄腐酸在不同浓度下所具有的生物活性。为更加合理地利用腐植酸提供参考，是评价腐植酸原料生长调节性能的主要方法之一，对泥炭、风化煤及褐煤资源在农业上的应用起重要的指导作用。     

A novel cyclodextrin-derived tellurium compound with glutathione peroxidase activity

A novel dicyclodextrinyl ditelluride (2-TeCD) compound was devised as a functional mimic of the glutathione peroxidase (GPX) enzymes that normally remove hydroperoxides from the cell. The GPX activity of the mimic was found to be 46.7 U microM(-1), which is 46 times as active as Ebselen, a well-known GPX mimic. A detailed steady-state kinetic study was undertaken to probe the reason for the high catalytic efficiency of 2-TeCD. This high efficiency can be explained based on both the binding of the substrate to the cyclodextrin and the catalytic mechanism of 2-TeCD, which is different from that of diselenide compounds. 2-TeCD exhibits good water solubility and is chemically and biologically stable. The biological effect of 2-TeCD was evaluated by its ability to protect mitochondria from oxidative damage. 2-TeCD exhibited excellent antioxidant capacity in comparison with Ebselen.     

Marvelous self-assembly of hierarchically nanostructured porous zirconium phosphate solid acids with high thermal stability

A hierarchical structure of thermally stable macroporous zirconium phosphate solid acids with supermicroporous walls was prepared by a simple self-assembly process from the precursors of zirconium propoxide and orthophosphoric acid solution. The macroporous structures are uniform with the diameters ranging from 300 to 800 nm, one-dimensional channel-like. The effect of surfactant Brij 56 on the formation of macroporous structures has been studied. The frameworks of the synthesized hierarchical zirconium phosphates are amorphous with Zr–O–P bonding, exhibiting remarkably high thermal stability (at least 800 °C), on the basis of the X-ray diffraction (XRD), N₂ adsorption, X-ray photoelectron spectroscopy (XPS) analysis, Fourier transform infrared (FT-IR) and ³¹P nuclear magnetic resonance (NMR) spectra. Larger quantities of Zr–OH and P–OH groups are observed besides surface hydroxyl groups, suggesting the presence of acidity and the possibility of surface functionalization for practical applications including catalysis. The macroporous zirconium phosphates with hierarchical structures could also be the potential and efficient catalyst supports for the design of the structured catalysts and reactors.