On the oxidative coupling of methane with carbon dioxide over CeO2/ZnO nanocatalysts

The nano-CeO₂/ZnO catalysts were prepared using a novel combination of homogeneous precipitation with micro-emulsion for oxidative coupling of methane with CO₂ as an oxidant. The prepared catalysts were compared with those prepared using the conventional impregnation. The catalysts prepared in two ways were characterized with FTIR, TEM, XRD and CO₂-TPD. The effects of the reaction temperature, the amount of ZnO doped in the catalysts and the average size were investigated. The experimental investigation demonstrated that methane conversion over the nano-CeO₂/ZnO catalysts prepared by the combined technique was higher than that obtained over catalysts prepared by the conventional impregnation. A better low-temperature activity has also been achieved over the nanocatalysts. There was no clear trend between the average size of nano-CeO₂/ZnO catalysts and their catalytic performance but methane conversion increased with increasing fractal dimension of nanocatalysts.     

萃取氧化法再生Pd/C催化剂的研究

通过甲醇用量、回流时间和硝酸浓度对催化剂活性的影响进行了讨论，研究了非那甾胺合成工艺中孕烯醇酮氢化Pd/C催化剂的再生方法。实验发现，对于1 g废Pd/C催化剂，以30 mL甲醇为萃取剂，回流萃取60 min，然后用35%的硝酸在80 ℃氧化30 min，可以达到满意的再生效果，新鲜和再生的Pd/C催化剂孕烯醇酮的氢化转化率分别为97.5%和98.5%。     

尼龙/聚丙烯合金的性能与制备

介绍国外各种尼龙/聚丙烯合金的性能和制备工艺。聚合物合金的相容性原理,以及PA/PP合金适用的各种相容剂。     

华润贵港5000t/d燃无烟煤生产线预分解系统的设计与工程应用

分解炉是烧成系统的关键设备，尤其是对于燃无烟煤的分解炉，既要保证无烟煤粉在炉内的充分燃烧．又要利于系统的操作控制。基于分解炉煤粉燃烧机理，并通过分析影响炉内煤粉燃烧的各种因素及依据所用无烟煤的热失重分析结果，中材国际南京水泥设计研究院开发设计出了用于华润贵港5000砌工程的喷旋管道式在线分解炉，并与高效、低阻、防堵的旋风预热系统组成了性能优异的预分解系统。从实际运行情况看，该预分解系统易于操作控制，且对物料适应性强、阻力损耗小。     

Study of the NOχ reaction with reducing gases on Fe/ZrO2 catalyst

The Fe/ZrO₂ catalyst (1% Fe by weight) shows a strong adsorption capacity toward the nitric oxide (at room temperature the ratio NOFe is ca. 0.5) as a consequence of the formation of a highly dispersed iron phase after reduction at 500–773 K. Nitric oxide is adsorbed mainly as nitrosyl species on the reduced surface where the Fe²⁺ sites are prevailing, but it is easily oxidised by oxygen forming nitrito and nitrato species adsorbed on the support. However, in the presence of a reducing gas such as hydrogen, carbon monoxide, propane and ammonia at 473–573 K the Fe-nitrosyl species react producing nitrogen, nitrous oxide, carbon dioxide and water, as detected by FTIR and mass spectrometers. The results show that nitric oxide reduction is more facile with hydrogen containing molecules than with CO, probably due the co-operation of spillover effects. Experiments carried out with the same gases in the presence of oxygen show, however, a reduced dissociative activity of the surface iron sites toward the species NO_χ formed by NO oxidation and therefore the reactivity is shifted to higher temperatures.     

Role of La2O3 in Pd-Supported Catalysts for Methanol Decomposition

Systems of Pd supported on various La₂O₃-modified -Al₂O₃ and CeO₂–Al₂O₃ catalysts were tested for catalytic methanol decomposition and characterized by means of XRD, BET, TPR, H₂-chemisorption and CO–FTIR. The addition of lanthanum significantly improved the selectivity of CO and H₂ for all the catalysts but showed a different influence on the catalytic activity in two systems. Methanol conversion decreased on La₂O₃-modified Pd/-Al₂O₃ catalysts, in line with the reduction of Pd dispersion, while the addition of La₂O₃ improved the dispersion of Pd and reinforced Pd–CeO₂ interaction for La₂O₃-modified Pd/CeO₂–Al₂O₃ catalysts, which resulted in a high production rate of CO and H₂. Thus, a synergistic effect between CeO₂ and La₂O₃ was observed on -Al₂O₃-supported Pd catalyst for methanol decomposition.     

The effect of fibre-matrix interactions on structure and property changes during the fabrication of unidirectional carbon/carbon composites

This paper reports the systematic characterisation of changes in the structure and properties of a series of unidirectional carbon-carbon composites at key stages of processing. The composites were fabricated from PAN-based carbon fibres (surface treated and untreated) and two carbon matrix systems (graphitising and non-graphitising). The effects of matrix shrinkage, together with thermal expansion mismatch and interfacial bonding, established the composite structure and hence the composite properties. The morphology and interconnectivity of the shrinkage cracks, the strength and nature of the fibre-matrix interfacial interaction and the development of matrix texture were identified as key structural features. These features were characterised and their effect on subsequent processing stages (densification) and composite properties was determined.     

复合材料纤维缠绕成型CAD/CAM相关技术研究

纤维缠绕成型是制造高强度复合材料制品的一种重要的工艺方法，将CAD／CAM方法应用其中可以大大提高生产效率，降低设计成本。本文提出了纤维缠绕CAD／CAM系统的总体方案，并对其中缠绕数学模型、线型优化、丝嘴轨迹生成等量要组成部分进行了分析与研究，为CAD／CAM系统的开发奠定了理论基础。     

Deformation Dynamics of a Reactive Medium During Gasless Combustion

Deformation during gasless combustion of 5Ti + 3Si and Ti + C samples was studied experimentally. The dynamics of motion of the material in a gasless combustion wave was studied using highspeed video recording (500 frames/sec) with a spatial resolution of the order of 10 m. It was shown that behind the combustion front, the medium was first expanded and then compressed. The dimensions of the expansion and compression zones were determined.     

Physical characteristics of sweet potato pulp/polycaprolactone blends

Sweet potato pulp (SSP) obtained as a by‐product from starch extraction was blended with polycaprolactone (PCL) to prepare a biodegradable plastic material. In the blends, PCL was used as a reinforcing agent. The SPP/PCL blends were prepared by compression‐molding under high temperature and pressure, at different SPP/PCL ratios, and the mechanical properties of the molded specimens were tested. Matrix structure and thermal properties were measured by using a Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). Mechanical properties (tensile and flexural properties) were also measured to find the most suitable ratio in a SSP/PCL blend. During compression molding of the SPP/PCL blends under high pressure and temperature, chemical reaction occurred between SPP and PCL, and thus, thermal stability and mechanical strength of the blends increased and water uptake decreased. Also, by increasing the PCL content in the blend, the matrix in the blend became more homogeneous, and consequently, mechanical strength of the molded specimen increased. At 7/3 or 6/4 weight ratio of SSP/PCL, water uptake of the molded specimen became substantially less than that at 8/2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 861–866, 2004