Thermal diffusivity of fiber-reinforced composites using the laser flash technique

The applicability of the flash technique for measuring thermal diffusivity of fiber-reinforced composites has been examined. While the usefulness of this technique has been demonstrated previously for randomly dispersed composites and for layered structures, problems arise from preferential heat paths in fibrous-reinforced composites. For these materials the concept of diffusivity must be expanded to include dependencies upon sample thickness to unit cell ratios and transient times in addition to the usual constituent property ratios and temperature dependencies of properties. Nevertheless, the flash technique has been shown to be a powerful tool for examining heat flow in these materials. It is possible to obtain diffusivity data which are equivalent to steady-state properties. In addition, it is possible to determine in situ properties for the fiber and matrix and to examine defect structures.     

Liquid-phase synthesized mesoporous electrochemical supercapacitors of nickel hydroxide

Electrochemical supercapacitive (ES) properties of liquid-phase synthesized mesoporous (pore size distribution centered ∼12 nm) and of 120 m²/g surface area nickel hydroxide film electrodes onto tin-doped indium oxide substrate are discussed. The amounts of inner and outer charges are calculated to investigate the contribution of mesoporous structure on charge storage where relatively higher contribution of inner charge infers good ion diffusion into matrix of nickel hydroxide. Effect of different electrolytes, electrolyte concentrations, deposit mass and scan rates on the current-voltage profile in terms of the shape and enclosed area is investigated. Specific capacitance of ∼85 F/g at a constant current density of 0.03 A/g is obtained from the discharge curve.     

New mesoporous carbon materials synthesized by a templating procedure

The new porous carbon materials were obtained by templating procedure using mesoporous silica (SBA-15) as template. The ordered mesoporous silica materials were synthesized by using Pluronic P123 (non-ionic triblock copolymer, EO₂₀PO₇₀O₂₀). SBA-15/cryogel carbon composites were obtained by sol–gel polycondenzation of resorcinol and formaldehyde in the presence of different amount of SBA-15. The polycondenzation was followed by freeze drying and subsequent pyrolysis. One set of SBA-15/sucrose carbon composites was prepared by using sucrose as carbon source. The silica template was eliminated by dissolving in hydrofluoric acid (HF) to recover the carbon material. The obtained carbon replicas were characterized by nitrogen adsorption–desorption measurements, X-ray diffraction and scanning electron microscopy (SEM). It was revealed that the samples have high specific surface (533–771 m² g^?1), developed meso- and micro-porosity and amorphous structure. Porous structure of carbon replicas was found to be a function of the carbon source, properties of SBA-15 and silica/carbon ratio. Room temperature adsorption of nitrogen and adsorption of phenol from aqueous solutions were investigated.     

Liquid-phase oxidation of benzene to phenol by molecular oxygen over transition metal substituted polyoxometalate compounds

Transition metal substituted polyoxometalate (TMSP) compounds were used as catalysts for the liquid-phase oxidation of benzene to phenol by molecular oxygen with ascorbic acid as a reducing agent in an acetone/sulfolane/water mixed solvent. [(C₄H₉)₄N]₅[PW₁₁CuO₃₉(H₂O)] is the best catalyst tested in this study. It showed 9.2% benzene conversion (TON = 25.8) and 91.8% selectivity to phenol for the oxidation of benzene at 323 K for 12 h. The effect of the substituted transition metal in the TMSP compounds on the benzene conversion is in the order: Cu > V > Fe ≫ Mn > Ti > Cr > Co > Ni > Zn. The effect of the central atom in the TMSP compounds on the benzene conversion is in the order: P ≈ Si > Ge > B. [SiW₁₁O₃₉]⁸⁻ is a good polyoxometalate ligand for transition metal ions as [PW₁₁O₃₉]⁷⁻ for the oxidation of benzene. The selectivity to phenol was dramatically improved by adding the sulfolane solvent, but the benzene conversion decreased when a large amount of sulfolane was used in the mixed solvent. Ascorbic acid is indispensable for forming phenol from benzene oxidation by O₂ over TMSP compounds. Higher O₂ pressure in the catalytic system ensured more oxygen molecules solving in the solvent, and promoted the benzene conversion.     

介孔材料合成研究进展

介孔材料具有比表面积大、孔径结构均一和可调等优良性能,在催化、吸附、分离、传感器以及光、电、磁等领域具有潜在的应用价值。综述了介孔材料的研究进展,介绍了介孔材料的分类、合成方法、合成机理及其应用。阐述了液晶模板、电荷匹配、棒状自组装、层状折皱模型和协同作用等介孔材料的合成机理,对介孔材料进行了展望。     

疏水微／介孔材料的合成及其对苯及其同系物的吸附

以含氢聚甲基硅氧烷(PMHS)、正硅酸乙酯(TEOS)为硅源,在室温、无模板剂条件下合成了一种疏水微孔/介孔材料,通过调节PMHS/TEOS的比例,获得了3种具有不同微孔,介孔比例的多孔材料.并通过N2吸附,脱附、HRTEM、热重等手段对上述3种材料的结构特征及热稳定性进行了表征.结果发现,所得材料均具有微孔和介孔两种孔隙结构,且具有良好的热稳定性和疏水性,在500℃以下不会发生热分解.进一步利用脉冲色谱技术研究了上述3种材料对苯及其同系物的热力学吸附行为.结果表明,上述3种材料均能够实现苯及其同系物的完全分离,相应的亨利常数、吸附热、分离因子的大小顺序为:正丁基苯>正丙基苯>乙苯>甲苯>苯,且随着PMHS/TEOS比例的增加,亨利常数、吸附热以及分离因子都增加.     

Molecular origin of decreased diffusivity with loading for benzene/HY

On the basis of our recently proposed “ideal” and “insertion” adsorption mechanisms of aromatics in HY zeolites, changes in energetic and dynamic properties with loading were investigated through Monte Carlo and molecular dynamic (MD) calculations. Loading‐dependent isosteric heat could be divided into three linear ranges. The two inflection points were attributed to adsorbate interactions and inherent adsorption mechanism changes. With regard to the loading dependence of diffusivity, diffusivity decreased faster at high loadings than at low and medium loadings, separated by an inflection point. This result confirmed a two‐stage diffusion mechanism based on the distribution of adsorbate from MD simulations which was able to qualitatively predict the further restriction of the mobility. This study provided insights into the modeling of mobility at high loadings on the basis of site‐hopping mechanism. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2778–2785, 2016     

催化裂化干气制乙苯中二乙苯的液相烷基转移

在绝热固定床反应装置上比较了3994催化剂和3984催化剂上二乙苯与苯液相烷基转移反应性能。与工业化3984催化剂相比, 3994催化剂具有低温和高空速特点。在起始温度245 ℃、 压力3.5 MPa、空速7 h^-1和n(苯)∶n(二乙苯)=1条件下,进行了189 h的强化实验,3994催化剂上二乙苯转化率稳定在35 %以上, 而对于3984催化剂, 只有提高温度才能维持二乙苯转化率大于 35 %。     

Ethylene polymerization catalyzed by metallocene supported on mesoporous materials

Summary  In this work, different mesoporous materials were employed for the preparation of supported metallocene catalysts to be evaluated in ethylene polymerization and their performance was related to the chemistry of the materials surface used as support. The supports employed were MCM-41, SBA-15 and mesoporous TiO₂. The performance of the prepared catalysts was compared with the homogeneous catalyst precursor system. Those mesoporous materials, as well as the prepared metallocene catalysts, were analyzed by infrared absorption spectrometry (FTIR). Polymers were also characterized by FTIR, for the determination of the number-average molecular weight, and by differential scanning calorimetry (DSC) to determine thermal characteristics of the produced polyethylene. Among the studied metallocene supported catalysts, the one based on the mesoporous support SBA-15 achieved the highest activities, almost as high as that observed for the homogeneous system.     

水采硝液相分离技术

根据水采硝液栩分离技术,对甘肃高台县芒硝伴生矿,成功地实施了开采。搜集和验证了水、温度、浓度之间的比例系数,建成了我国又一个中型无机盐化工基地。     

磺酸型介孔材料催化合成甲基葡萄糖苷

以甲醇和葡萄糖为原料,采用一步合成法合成甲基葡萄糖苷。以磺酸型介孔材料作为催化剂,借助扫描电子显微镜、高分辨率透射电子显微镜、低温氮气吸附/脱附、热重分析等方法研究了材料的结构和性能。实验结果表明,催化剂用量为0.6g,醇糖摩尔比为28∶1,反应温度为115℃,反应时间为2 h为最佳反应条件,此条件下合成产物的收率可达95.67%。同时使用Fourier红外光谱仪对产物进行了表征。     

Benzylation of benzene and other aromatics by benzyl chloride over mesoporous AlSBA-15 catalysts

Aluminum-containing mesoporous molecular sieves AlSBA-15 with different n_Si/n_Al ratios and AlMCM-41 have been synthesized hydrothermally and characterized in detail by physicochemical methods, viz. XRD, N₂ adsorption and ²⁷Al NMR spectroscopy. The low angle XRD and N₂ adsorption measurements reveal that the structural order of SBA-15 was retained after the incorporation of Al. The increase of the unit cell parameter with increasing aluminum content and ²⁷Al MAS NMR spectroscopy confirm the incorporation of aluminum in the framework. Benzylation of benzene and substituted benzenes reaction employing benzyl chloride as the alkylating agent over AlSBA-15 and AlMCM-41 have been investigated. The influence of various reaction parameters such as reaction temperature, reactant feed ratio and catalyst amount affecting the activity and selectivity of AlSBA-15, have been studied. Among the mesoporous catalysts studied, AlSBA-15(45), where the number in parentheses indicates the molar n_Si/n_Al ratio, shows both high conversion and high selectivity for the benzylation of benzene. The activity of this catalyst for the benzylation of different aromatic compounds is in the following order: benzene > toluene > p-xylene > mesitylene > anisole. Kinetics of the benzene benzylation over different catalysts have also been investigated.     

体积排阻色谱法测定介孔材料的孔结构

分别合成了球形的苯基桥键和乙烷桥键两种新型杂化介孔材料.选用已知平均相对分子质量且具有窄相对分子质量分布的葡聚糖为探针溶质,采用动态光散射法测定了粒径,与经验公式计算结果接近.通过体积排阻法对两种材料的孔隙率和孔径分布进行测定并与氮气吸附法结果进行比较,实现介孔材料孔结构快速测定.结果表明,体积排阻色谱法测定苯基桥键和...     

有机基团改性介孔硅基材料的研究进展

介绍了有机基团改性介孔硅基材料的种类及研究现状。经不同有机基团改性后,材料的活性位点增多,亲疏水性能改变以及水热稳定性增加,使其在吸附、医疗以及建筑领域有着广泛的应用。详细介绍了其在吸附重金属离子,染料分子,气体分子以及阴离子中的应用,同时介绍了经有机基团改性后材料接触角改变在古建筑保护和油水分离方面的应用。并对目前研究中存在的问题进行总结并对该杂化材料的发展趋势进行了展望。     

有机基团改性介孔硅基材料的研究进展

介绍了有机基团改性介孔硅基材料的种类及研究现状。经不同有机基团改性后,材料的活性位点增多,亲疏水性能改变以及水热稳定性增加,使其在吸附、医疗以及建筑领域有着广泛的应用。详细介绍了其在吸附重金属离子,染料分子,气体分子以及阴离子中的应用,同时介绍了经有机基团改性后材料接触角改变在古建筑保护和油水分离方面的应用。并对目前研究中存在的问题进行总结并对该杂化材料的发展趋势进行了展望。     

Determination of appropriate effective diffusivity for different food materials

Effective diffusivity is the most important key parameter needed in the analysis, design, and optimization of heat and mass transfer during food drying process. In general, two types of effective diffusivities are used to develop the mathematical modeling of food drying, namely, moisture-dependent effective diffusivity (MDED) and temperature-dependent effective diffusivity (TDED). However, no study has extensively investigated which effective diffusivity is more accurate in predicting drying kinetics. The main goal of this study is to determine the appropriate effective diffusivity for predicting the drying kinetics. Drying models were developed for different fruits and vegetables based on moisture-dependent and temperature-dependent effective diffusivities. COMSOL Multiphysics, a finite element-based engineering simulation software is used to solve the coupled heat and mass transfer equations. 3D moisture profiles were developed to investigate the spatial moisture distribution during drying. Extensive experimental investigation on five types of fruits and vegetables was conducted and results were compared with the simulated results. The experiments were repeated thrice, and the average of the moisture content at each value was used for constructing the drying curves. Close agreement between experimental and simulated results validates the models developed. It was observed that the moisture profile and temperature profile in case of MDED were more closely fitted with the experimental results. For all fruits and vegetables, the moisture ratio with MDED was significantly lower than moisture ratio with TDED. This finding confirms that the MDED is more accurate for predicting kinetics in food drying. Moreover, the moisture ratio of apple was lowest whereas pear showed the highest moisture ratio. On the other hand, carrot showed a considerably lower moisture ratio compared to potato.     

软模板法合成有序介孔材料的研究进展

有序介孔材料具有高度有序的孔道结构,较高的比表面积和较多活性位,已经广泛应用于气体吸附、催化剂和功能材料等领域。本文系统评述了软模板法制备有序介孔材料的合成路线及其组装机理,并对课题组采用软模板法组装介孔氧化钛粒子的机理进行了分析。