Bamboo-shaped carbon nanotubes fabricated by the catalytic growth method with Ni/metallic oxide catalyst are systematically studied using transmission electron microscopy. It is found that except for the nodes the bamboo-shaped carbon nanotubes can be regarded as stacking of truncated conical graphene sheets. Depending on the size of a catalyst, the Ni particles can be encapsulated inside the tubes or at the growth front of the tubes with a plug-shape. A linear relationship between size of the nanotube and the catalyst particle is found. The results suggest that the nanometer-sized Ni catalyst particles are in the liquid state during nanotube growth. A simple model for the growth of bamboo-shaped nanotubes is proposed.

分子筛膜具有优良的反应和分离性能，可用于高温、高压等苛刻环境，在膜分离和膜反应等过程中的应用潜力巨大。迄今为止，已有多种分子筛膜的制备方法，包括聚合物嵌入法、原位水热晶化法和二次生长法等。与原位方法相比，二次生长法更容易操作，对晶体取向、微孔结构和膜厚等方面的控制优势明显，而且重复性也有大幅度提高。本文总结了分子筛膜的合成方法，特别着重于最具使用潜力的二次生长法，对目前存在的晶体取向、缺陷以及晶粒层数等热点问题进行了分析和论述，提出了分子筛膜制备过程中需要进一步解决的关键问题，有助于提高分子筛膜制备技术的水平。

Carbon nano-filament formation in hydrocarbon and syngas based catalytic processes is fatal for supported metal catalysts as this leads to deactivation and crushing, and hence limitation of carbon deposition has been a major topic in catalysis.1-5 Recently, the deliberate preparation of catalytically grown nanocarbons has been investigated because of their specific structure and potential for application in many fields.6-8 Many nanocarbon conformations have been reported, such as tubular, coiled, helical, branched, octopus, etc. and have been found to be sensitive to the reaction conditions and catalyst properties.9-14 Catalytic hydrocarbon decomposition9-13 or arc-discharge evaporation of graphite14-18 have been often used as preparation methods, though in the latter case, the presence of a metal is necessary as catalyst in the form of either vapor or droplets of melt. The selective preparation of a given formation is a challenge to catalysis researchers. Here, several nanocarbon conformations are shown to be formed with high morphological purity from methane on a coppernickel-alumina catalyst, and some interesting phenomena related to the nanosized metal are reported.

The effect of the mechanical failure of catalyst pellets on the pressure drop across a laboratory-scale catalyst packing has been examined by experiment. Results reveal that, along with the mechanical failure ofthe pellets, there exists a point ofmaximum curvature around which the slope of pressure drop increases rapidly. This rapid increase is attributed to a mutation of the packing structure, occurring as the amount off ailed pellets reaches a certain critical value. The secondary breakage ofthe pellets contributes much to the mutation of the packing and to the pressure drop. It has been observed that a trilobite catalyst is more susceptible to a mechanical stress than a cylindrical catalyst, and that a catalyst with a smaller diameter is much easier to result in an increase in the pressure drop. The measurement of the pressure drop across a laboratory-scale catalyst packing as the failure of pellets under a mechanical stress has a satisfactory reproducibility, and has a close meaning to the mechanical reliability of a: xed bed converter, and hence is recommended as a method for catalyst assessment. The multi-scale and multi-disciplinary nature ofcatalyst mechanical reliability is also discussed.

Mathematical models for the e ects ofthe calcination process conditions on the mechanical properties ofa PCoMo/Al2O3 hydrotreating catalyst are developed using a response surface methodology. A central composite design is performed to study collectively the e ects ofcalcination temperature, calcination time and heating rate on the mean strength and Weibull's modulus. A model is obtained for each response with multiple regression analysis and then is re6ned. Analysis ofvariance reveals that the models developed are adequate. The validity ofthe models is also veri6ed by experimental data. Statistics reveals that there is a great potential for increasing the mechanical reliability in the calcination process. Analysis ofresponse surface show that the mean strength and Weibull's modulus increase with the increase ofcalcination temperature. The middle level ofheating rate results in smaller mean strength and higher Weibull's modulus. The mean strength increases as calcination time increases. However, calcination time has no signi6cant e ect on Weibull’s modulus in the experimental domain examined.

A Monte Carlo simulation is used to obtain the statistical properties of the Weibull parameters estimated by the linear regression, weighted linear regression and maximum likelihood schemes, respectively. Results reveal that the natural logarithm of the Weibull size parameter can be determined with about the same precision as the Weibull modulus. For Weibull modulus estimation, a maximum likelihood method results in the highest estimation precision; however, with a low safety factor. The weighted linear regression method with a weight factor Wi=F2i and a probability estimator Pf(Fi)=(i−0.3)=(n+0.4) or Pf(Fi)=(i−3/8)=(n+1/4), which leads to a similar estimation precision and a much higher safety factor, is considered to be the best method for engineering design. Simulations show that the weight factors and the probability estimators have e ects on the estimation precision. It is also concluded that the precision of any estimation method increases with the increase of the sample size. It is rea;rmed that 30-60 specimens are required to obtain a reasonable estimation precision of the Weibull parameters.