条状超细镍基负载型催化剂性能研究

用溶胶-凝胶法制备了Ni/TiO_2-SiO_2催化剂粉状前驱体,挤条成型,预还原后用于苯加氢反应,其比表面积和孔容分别达到349 m~2·g~(-1)和0.35 cm~3·g~(-1)。采用BET、XRD和TEM对催化剂物化性能进行表征。利用脉冲氢吸附法考察催化剂中活性组分镍的表面分散度。在固定床微反装置上,以噻吩为毒物,考察了催化剂抗硫中毒性能。在100 mL中试装置上,考察了预还原后催化剂的苯加氢反应的活性、选择性和热稳定性能。实验结果表明,条状Ni/TiO_2-SiO_2催化剂有较大的比表面积,单一的孔径分布,活性组分镍高度分散。每克镍上极限耐硫量达到467.25 μL噻吩。在试验条件下,催化剂能在较宽的温度和液苯空速范围使用,经25天运转,进行100 h催化老化实验,催化剂的比表面性能无显著变化。     

The influence of different factors on the porous structure of the positive electrode in lead-acid batteries

Geometric structure measurements of positive electrodes have been determined by measuring cumulative pore volume, pore size distribution, porosity, pore specific surface area and BET specific surface area. The influence of technological parameters such as concentration of SO₄²⁻ ions in the paste, the temperature of the paste and the quality of oxides on the structure of porous positive electrode have been studied. The relation between BET specific surface area and the electrical capacity of the positive electrode is shown and interpreted.     

Large pore heavy oil processing catalysts prepared using colloidal particles as templates

Macroporous FCC catalyst and macroporous HDS catalyst were prepared using polystyrene spheres as template. The size of the macropores can be tailored by controlling the size of template. The BET surface area and the pore volume of the macroporous catalysts are larger than those of catalysts prepared without template, and the more template used, the larger the surface area and pore volume obtained. When the same amount of template was used, the smaller diameter template produced a catalyst with larger surface area and pore volume. The increments in surface area and pore volume of the catalysts were greater than those predicted from the geometry of the template, indicating particle template could inhibit the shrinkage of the catalyst during drying. When used as heavy oil FCC catalysts and heavy oil HDS catalyst, the prepared macroporous catalysts are much more active than catalysts prepared without the template.     

双电层电容器活性炭电极的优化

通过物理方法对双电层电容器用活性炭电极进行改性实验,探讨了活性炭电极的结构（比表面积、孔径分布、孔容）和性能（比电容、充放电特性）的优化问题.改性后活性炭电极BET比表面积从1739.77 m²•g^-1增至2215.40 m²•g^-1,其中微孔比表面积增幅22％,中孔比表面积增幅35％,孔容积也有20%～30％的增幅量,孔径分布更为合理.优化的活性炭电极结构改善了电极材料的电化学特性,比电容量可达424 F•g^-1,增幅10％.     

采用KOH与NaOH活化剂所制活性炭表面化学性质及孔结构的比较

采用沥青焦为原料,以KOH和NaOH活化剂制备出不同碱炭质量比（R）系列活性炭。利用X射线衍射（XRD）和X射线光电子能谱（XPS）表征出所制活性炭的石墨层结构和表面化学性质,并用氮气吸附和脱附等温线计算出BET比表面积、DFT孔径分布及孔容。实验结果表明,与NaOH活化剂相比,KOH活化剂所制活性炭石墨层破坏更明显,表面含氧官能团也明显增加。当R=5时,KOH活化剂所制样品BET比表面积高达2939m^2／g,孔容为1．43cm^2／g;而NaOH活化剂所制样品BET比表面积和孔容分别只有1098m^2／g、0．53cm^2／g。     

The effect of experimental parameters on the synthesis of carbon nanotube/nanofiber supported platinum by polyol processing techniques

Developing corrosion resistant carbon nanotube (CNT) and carbon nanofiber (CNF) supported Pt catalysts with optimized particle size is important for proton exchange membrane fuel cells. We investigated the effects of deposition technique (conventional refluxing and microwave irradiation), water content, carbon support and metal loading on the average Pt particle size and electrochemically active surface area (ECSA). BET surface area measurements, Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, transmission electron microscopy and cyclic voltammetry were used to characterize all the CNT/CNF supported catalysts. Processing was accelerated via microwave irradiation without significantly affecting Pt particle size as compared to conventional refluxing especially for high surface area CNT supported low Pt loading (10 wt%) catalyst. Adjusting the water content during synthesis effectively controlled the Pt particle size and size distribution regardless of the heating method, carbon support and metal loading. The ECSA of the samples was found to be dependent on Pt particle size which further depends on the water content during synthesis, support surface area and Pt loading. Optimization of deposition conditions leads to higher ECSA than seen in a commercially available carbon black supported catalyst.     

Surface studies on catalysts used for deuterium exchange between hydrogen and water vapour

Platinum/charcoal and nickel/chromium oxide catalysts for the isotopic exchange of deuterium between hydrogen and water vapour were prepared under optimum experimental conditions. The catalytic activity determination of both indicated higher activity for Pt/charcoal than for Ni/Cr₂O₃. BET measurements of the specific surface area and pore structure showed higher values for Pt/charcoal than for Ni/chromia. Chemisorption data of both catalysts allowed the determination of the specific metallic surface area, the degree of dispersion and the average particle size of the supported metals. A comparison between the results of the catalytic activity, BET measurements and chemisorption was made and indicated close agreement.     

美罗培南合成用钯炭催化剂的失活及再生研究

采用物理吸附、X射线衍射、扫描电镜、X射线能谱及等离子体发射光谱法对在美罗培南合成过程中失活的Pd/C催化剂比表面积、孔容、孔径、钯粒径形貌、表面元素及钯含量的变化进行分析,对催化剂的失活原因及再生方法进行研究。结果表明,催化剂在反应过程中吸附体系物质对钯活性中心的覆盖包裹及金属钯的少量流失是催化剂失活的主要原因。以30%四氢呋喃水溶液在超声条件下洗涤可以部分去除催化剂表面沉积的有机物,同时补加质量分数30%催化剂时,再次使用时效果较好。     

水蒸气活化法制备椰壳活性炭的孔结构特征

以农林废弃物椰壳在600℃炭化2h后的炭化料为原料,以水蒸气为活化剂,研究了活化温度、活化时间、水蒸气用量对活性炭的比表面积、微孔容积和收率等的影响。结果表明：椰壳炭化料的比表面积仅为185m^2／g,且以中孔为主。在活化过程中,通过提高活化温度和水蒸气用量缩短了活化时间,扩宽了孔径;当水蒸气用量和活化温度较为适宜时,延长活化时间,有利于微孔的形成。活性炭的比表面积、总孔容积、微孔容积可达：1465m^2／g,0．9703cm^3/g,0．7519cm^2／g。并通过非定域密度函数理论（NLDFT）对活性炭的孔径分布进行了表征。     

Nitrogen BET surface area measurement as a fingerprint method for the estimation of pore volume in active carbons

A good correlation was found between apparent BET surface area and total pore volume determined for a number of active charcoals by measurement of the nitrogen adsorption isotherms at 77 K. A similar correlation is also illustrated in which apparent BET surface area is calculated from the uptake of nitrogen at relative pressure $\text{p}\text{p°}\text{= 0.1}$. This method is suggested as a rapid means of estimating pore volume in predominantly microporous carbons.     

中孔碳负载Pt催化剂用于抗氧剂7PPD合成反应

以纳米氧化锌为模板剂,酚醛树脂为碳源,通过硬模板法制备了中孔碳,并以其为载体制备了Pt/MC催化剂,通过BET、SEM、ICP、TEM等表征手段对中孔碳及其负载的Pt/MC催化剂进行表征。结果表明,可以通过模板剂有效调控中孔碳的比表面积和孔结构。将制备的Pt/MC催化剂用于抗氧剂7PPD合成反应,对比普通Pt/AC催化剂,p-ADPA的转化率由97.5%提高至100%,7PPD选择性由94.5%提高至99.5%,催化剂的稳定性明显提高。通过CO化学吸附、ICP、BET等对新鲜和使用十次后的催化剂进行表征,结果表明,催化剂载体的孔结构是影响催化剂稳定性的重要因素,平均孔径较小时,7PPD等大分子尺寸的分子容易堵塞孔道;平均孔径较大时,孔壁较薄,催化剂使用过程中容易磨损,活性组分流失。     

Characterization of porous structure of coal char from a single devolatilized coal particle: Coal combustion in a fluidized bed

The combustion characteristics of coal char are highly dependent on initial pore structure of devolatilized char as well as on the structural evolution during the combustion of char. The development of pore structure also throws light on the mechanism of the combustion process. In the present work evolution of pore structure of partially burnt coal char of Indian origin has been investigated experimentally in a batch-fluidized bed and analyzed. The BET surface area, micropore surface area and porosity of char at various levels of carbon burn-off have been determined. Experimental specific surface area has been found to agree well with theoretical prediction using random pore model. Modified random pore model is used to determine the active surface area. Char combustion mechanism based on shrinking unreacted core and shrinking reacted core models are delineated during the course of reaction at various bed temperatures. This is substantiated with the proportional representation of ash and carbon matrix in scanning electron microscope images. It is also concluded that in the present investigation the mean pore size is much smaller and hence the Knudsen diffusion predominates. Analysis based on similar experimental observations and models for pore structure evolution to investigate char combustion reaction regime has not been reported in literature.     

硝基苯催化加氢Pt-MoS2/C催化剂的制备及使用寿命的研究

采用浸渍法制备Pt/C和Pt-MoS2/C催化剂,用于催化硝基苯加氢反应。采用BET、压汞仪等测试方法测定新鲜催化剂和重复使用后的催化剂的比表面积和孔容。结果表明,比表面积下降27.3%,微孔孔容下降13.2%,总孔容下降5.8%。催化剂失活的主要原因为有机物覆盖在催化剂表面,造成表面积下降和孔堵塞。负载MoS2可使Pt/C催化剂延缓比表面积下降和孔堵塞,寿命显著提高,可循环使用14次左右。     

SURFACE PROPERTIES AND ADSORPTION BREAKTHROUGH CURVES OF PLASMA-TREATED SILICA GELS

Plasma treatments are used widely in surface modification of thin films and membranes. A similar treatment method was used for granular silica gel by using both argon and oxygen plasma. The surface properties, such as contact angle of water, pore diameter, and BET surface area, and the adsorption breakthrough curves for water were obtained on the plasma-treated silica gel. The contact angle of water decreased rapidly and then remained approximately constant during the plasma treatment. This indicated that argon- or oxygen-plasma treatment made the silica gel surface more hydrophilic. The increase in BET surface area of the plasma-treated silica gels was 13 to 15%. The experimental breakthrough curves showed that modification not only increased the effective surface area and active sites but also reduced the mass transfer resistance. The time for breakthrough increased by about 4 minutes when either argon- or oxygen-plasma treated silica gels were compared to the untreated one. The amount of moisture adsorbed by the modified silica gel as calculated from the breakthrough curve was increased by 18% compared to the untreated sample.     

SURFACE PROPERTIES AND ADSORPTION BREAKTHROUGH CURVES OF PLASMA-TREATED SILICA GELS

Plasma treatments are used widely in surface modification of thin films and membranes. A similar treatment method was used for granular silica gel by using both argon and oxygen plasma. The surface properties, such as contact angle of water, pore diameter, and BET surface area, and the adsorption breakthrough curves for water were obtained on the plasma-treated silica gel. The contact angle of water decreased rapidly and then remained approximately constant during the plasma treatment. This indicated that argon- or oxygen-plasma treatment made the silica gel surface more hydrophilic. The increase in BET surface area of the plasma-treated silica gels was 13 to 15%. The experimental breakthrough curves showed that modification not only increased the effective surface area and active sites but also reduced the mass transfer resistance. The time for breakthrough increased by about 4 minutes when either argon- or oxygen-plasma treated silica gels were compared to the untreated one. The amount of moisture adsorbed by the modified silica gel as calculated from the breakthrough curve was increased by 18% compared to the untreated sample.     

Maya crude hydrodemetallization and hydrodesulfurization catalysts: An effect of TiO2 incorporation in Al2O3

Hydrotreating of Maya heavy crude oil over high specific surface area CoMo/TiO₂–Al₂O₃ oxide supported catalysts was studied in an integral reactor close to industrial practice. Activity studies were carried out with Maya crude hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), and hydrodeasphaltenization (HDAs) reactions. The effect of support composition, the method of TiO₂ incorporation, and the catalyst deactivation are examined. Supported catalysts are characterized by BET specific surface area (SSA), pore volume (PV), pore size distribution (PSD), and atomic absorption. It has been found that sulfided catalysts showed a wide range of activity variation with TiO₂ incorporation into the alumina, which confirmed that molybdenum sulfided active phases strongly depend on the nature of support. The pore diameter and nature of the active site for HDS, HDM, HDN, and HDAs account for the influence of the large reactant molecules restricted diffusion into the pore, and/or the decrease in the number of active sites due to the MoS₂ phases buried with time-on-stream. The textural properties and hysteresis loop area of supported and spent catalysts indicated that catalysts were deactivated at the pore mouth due to the metal and carbon depositions. The atomic absorption results agreed well regarding the textural properties of spent catalysts. Thus, incorporation of TiO₂ with γ-Al₂O₃ alters the nature of active metal interaction with support, which may facilitate the dispersion of active phases on the support surface. Therefore, the TiO₂ counterpart plays a promoting role to HDS activity due to the favorable morphology of MoS₂ phases and metal support interaction.     

Characterisation of Catalysts Used in Wall Reactors for the Catalytic Dehydrogenation of Methylcyclohexane

The catalytically active coatings of tube wall reactors, consisting of an aluminium oxide washcoat and platinum, platinum/tin, or platinum/rhenium deposited by incipient wetness impregnation, are characterized using BET surface area measurements, CO chemisorption, X-ray photoelectron spectroscopy, plasma atomic emission spectroscopy, high resolution transmission electron microscopy (HRTEM), and extended X-ray absorption fine structure analysis (EXAFS). The mesoporous catalysts show a type-IV adsorption isotherm, yielding an average pore diameter of 9 nm, and a BET surface area between 178 and 197 m²/g. From the bulk and surface analysis results, an enrichment of tin or rhenium, respectively, is found to take place at the surface of the bimetallic catalysts. Very good agreement between the particle sizes estimated from EXAFS, CO-chemisorption, and HRTEM data is found for a low loading (1.5 wt%) platinum catalyst, leading to dispersion values between 75 and 80%, a cluster size of 30 atoms, and a particle diameter around 13 Å. Using the catalytic dehydrogenation of methylcyclohexane as a test reaction, it is demonstrated that a pretreatment at high reduction temperatures leads to a decrease in activity. EXAFS show that this effect is due to a stronger metal–support interaction, as indicated by the appearance of a Pt-O contribution at 2.25 Å in the coordination sphere of the surface platinum atoms.     

Comparisons of pore properties and adsorption performance of KOH-activated and steam-activated carbons

Carbonaceous adsorbents with controllable pore sizes derived from carbonized pistachio shells (i.e., char) were prepared by the KOH activation and steam activation methods in this work. The pore properties including the BET surface area, pore volume, pore size distribution, and pore diameter of these activated carbons were characterized by the t-plot method based on N₂ adsorption isotherms. Through varying the KOH/char ratios from 0.5 to 3, the KOH-activated carbons exhibited BET surface areas ranging from 731 to 1687 m²/g with a similar micropore content (80–92%). The carbons activated by steam at 830 °C for 2 h had a BET surface area of 821 m²/g with the micropore content of 42%. The micropore/total pore volume ratio (V_micro/V_pore) and average pore size (D_pore) were independent of the KOH/char ratio, revealing that KOH activation is a powerful method in developing and controlling the number of micropores with a very similar pore size distribution. The adsorption equilibria and kinetics of methylene blue, basic brown 1, acid blue 74, 2,4-dichlorophenol, 4-chlorophenol, and phenol from water on all activated carbons at 30 °C were investigated to demonstrate the fact that adsorption of organics is not only dependent upon the BET surface area but is also determined by the relative size between pores and molecules. The adsorption isotherms were subjected to the model fitting according to Langmuir and Freudlich equations. By comparing the projected area of adsorbates, the surface coverage of phenols is about 3.6 times of that of dyes (based on unit gram of activated carbon). The Elovich equation was found to suitably describe the adsorption process of all KOH-activated carbons while the adsorption behavior on the steam-activated carbon was reasonably fitted with the intraparticle diffusion model.     

Particle structure change of CaO during high temperature sulphatization

The effects of particle size (layer thickness), BET surface area and pore size distribution on the reactivity of CaO derived from limestone were studied by using a pH-stat and the BET method. Visual analysis was obtained with SEM, and X-ray diffraction was used to determine the crystalline components present. It was found that the pore size distribution, including pore volume and pore surface distribution, affected the sulphatization behaviour. The larger pores (D > 50 Å) with their pore volume and pore surface were to some extent responsible for both initial reactivity and ultimate capacity of CaO.     

溶胶凝胶法合成中孔氧化锆分子筛

以无水乙醇为溶剂，采用溶胶-凝胶法合成中孔氧化锆，对合成的样品进行低温N2吸附-脱附、X—ray粉末衍射（XRD）、傅立叶变换红外光谱（FT—IR）等表征。结果表明，溶胶-凝胶法可以制备出具有单一晶型的四方相中孔氧化锆，其比表面积（BET）72．98m2／g，孔径2．2nm。