Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions

This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.     

强流脉冲电子束作用下金属纯Cu的微观结构状态——空位簇缺陷及表面微孔结构

利用强流脉冲(HCPEB)电子束技术对多晶纯Cu进行了辐照处理,并利用透射电镜对HCPEB诱发的空位簇缺陷进行了表征.实验结果表明,HCPEP辐照金属可在纯Cu表层诱发大量的过饱和空位,并形成四方形空位胞及空位型位错圈和堆垛层错四面体(SFT),HCPEB瞬间的加热和冷却诱发的幅值极大的应力和极高的应变导致的整个原子平面的位移是空位簇缺陷形成的主要原因.此外,扫描电镜分析表明HCPEB辐照可以在纯Cu表面形成高密度、弥散分布和尺寸细小的微孔.过饱和空位或空位团簇沿晶体缺陷向表面扩散、凝聚是表面微孔形成的根     

锡掺杂超微孔二氧化锆的合成及表征

The super microporous tin-doped zirconium oxides were successfully synthesized by sol-gel method using zirconyl chloride as Zr source, tin chloride as Sn source and cetyltrimethylammonium bromide （CTMAB） as template under hydrothermal or refluxing conditions. The structures of the resultant materials were characterized by XRD, BET, FTIR, TG-DTA, XRF and HRTEM techniques. Experimental results indicated that the framework of the samples is typically ordered hexagonal structure. The surface area and pore volume of the materials prepared by refluxing method were larger than by hydrothermal method, but the ordering of pore distributions is lower. The thermal stability of the samples was relatively high （〉773 K） and decreased with the increment of tin content.     

Study of catalytic fibrous carbon microporosity by a new gas-chromatographic probe method

A new gas-chromatographic probe method (GCPM) is proposed to study the microporous structure of solids. This method was applied to analyze the catalytic fibrous carbon (CFC) microtexture by the adsorption of halogenated benzene derivatives used as molecular probes. The micropore size distribution in the range of 0.34–0.40 nm was measured.     

Differential calorimetric enthalpies of adsorption ofp-xylene andm-xylene on y faujasites at 25°C

The differential enthalpies of adsorption ofp-xylene andm-xylene on NaY, KY and BaY zeolites were measured by isothermal calorimetry coupled with isothermal volumetry at 25C. Whatever the zeolite, the enthalpies of adsorption ofp-xylene andm-xylene at low filling were of the same order of magnitude. They did not show significantly the effect of the dipolar moment ofm-xylene. Their absolute values varied in the sequence Q ₀(pX/NaY)<Q ₀(pX/KY) =Q ₀(mX/KY)<Q ₀(pX/BaY)<Q ₀(mX/NaY) =Q ₀(mX/BaY)During the adsorption of the third molecule of xylene per -cage, BaY zeolite exhibited specific behaviour: the differential enthalpies of adsorption decreased with the filling of the -cages in such a way that they became lower than those of the other two zeolites. Some arguments concerning the structures of the zeolite and xylene molecules can explain such behaviour. Whatever the zeolite, the adsorption capacity of the -cages was 3.5 molec.^–1. For relative pressures ranging from 0.2 to 0.5, an additional adsorption of about 0.1 molec.^–1 occurred on the external surface.     

不同方法制备的脱铝Y沸石的孔结构

Y沸石脱铝有多种方法。由于在脱铝过程中发生水解、聚合、重排等反应,分子筛的孔结构将发生很大的变化,如形成空穴,甚至可导致骨架结构单元的崩塌,形成二次孔。由于不同的脱铝方法的脱铝机理不同,即使它们的脱铝程度一致,产生的孔结构也将不同,这必将导致它们的酸性质和催化性能的差异。目前关于Y沸石孔结构的研究报导还很少,尤其对SSY,US-SSY沸石孔结构的报导更为鲜见。本文用低温N_2吸附-脱附等温线和层厚t等方法,对四种不同方法制备的脱铝Y沸石(USY,DAY,SSY和US-SSY)的微孔、二次孔及其孔径分布(2.0～60.0nm)进行了初步研究,得到了一些有用的信息,为进一步研究其酸性质和催化性能打下了基础。     

Equilibria and kinetics characterisation of two different structured nutshell-derived activated carbons

Adsorption equilibria and dynamics ofn-butane on two activated carbon samples prepared from the physical activation of nutshell are studied in this paper. The micropore size distribution (MPSD) is considered as the main source of solid heterogeneity. Lennard-Jones' potential theory and Dubinin's theory (TVFM) are used in the equilibria data to derive the MPSD, which is well fitted by a Gamma distribution function. The adsorption energy distribution derived from the MPSD is very asymmetric for both the samples studied, and this energy distribution used in the HMSD/HMSMD kinetics models for the study of adsorption dynamics ofn-butane.     

Recrystallization-induced defect porous nature of C60 crystals

Defective state of C₆₀ crystals was controlled by the recrystallization and annealing. The defective structure was examined by the X-ray diffraction and N₂ adsorption at 77 K. Recrystallized C₆₀ crystals without annealing showed broad diffraction peaks and the N₂ adsorption isotherm had marked low pressure uptake and a hysteresis in the high pressure region, indicating presence of both micropores and mesopores. The average micropore width was 8 Å which is closed to the C₆₀ molecular size, while the average mesopore one was 50 Å. The mesopores disappeared by annealing up to 393 K. On the other hand micropores of 8 Å remained even by heating up to 673 K.