固体催化剂宏观结构表征技术

介绍了催化剂宏观结构,包含密度、颗粒形状和尺寸、比表面、孔结构4个方面内容,并针对这几方面,综述了目前常用的一些表征技术,最后对这些表征技术进行了总结。     

球形活性氧化铝的制备和性能研究

本文对球形活性氧化铝的制备和性能进行了初步研究。采用并流法使硝酸与偏铝酸钠溶液反应制得氢氧化铝,考察了干燥方法对其胶粘性的影响。氢氧化铝分别与稀硝酸或铝溶胶混合后采用转动成型法制成球状活性氧化铝,比工业用高强度球形活性氧化铝具有更高的抗压强度、耐水性、比表面和合适的孔结构 。     

对苯二甲酸精制钯炭催化剂载体活性炭的研究

分析了不同厂家生产的对苯二甲酸精制用钯炭催化剂载体活性炭的各种物性指标。实验结果表明,各种活性炭比表面相同时,其吸附量基本相近,但孔结构有较大差异,尤其是中孔孔容相差较大。中孔孔容增大,有利于钯炭催化剂分散度的提高和热稳定性增强.活性炭的表面基团对催化剂分散度也有影响,表面酸性基团含量增加,值化剂分散度提高.     

丙烯氧化制丙烯醛催化剂的孔结构对催化效能影响的初步探讨

本文报导了丙烯选择氧化制丙烯醛片状催化剂(两个配方Bi—Mo系和W—Bi—Mo系)的孔结构参数(比表面、孔容、平均孔半径)的测试结果,分析了催化剂效能(活性、选择性)与诸宏观结构参数的依赖关系,并根据催化过程中催化剂内部物理传递过程的一般原理,参考已报导的该反应的动力学方面的结论,初步探讨了为提高催化剂的效能(在不改变配方的前提下)催化剂孔结构参数应当控制的数值范围。     

载体的性质对CO气相催化偶联反应的影响

考察了以α－Al2O3为载体的负载型钯系双金属催化剂用于CO气相催化偶联制备草酸二乙酯反应的活性。研究了催化剂的比表面和孔结构对负载型钯系双金属催化剂的选择性和活性的影响。结果表明，催化剂的比表面对反应的选择性和活性的影响并不十分明显；孔结构则对其有较大的影响，其中孔容的影响较大，孔径也是有一定的影响；在合适的孔径范围内，CO转化率基本随孔容的减小而增大。     

球形中空催化剂载体的制备

制备了一种用于制造球形中空催化剂载体的造孔材料。用正交实验的方法选择了造孔材料的原料配比,得到最佳制备条件为：造孔材料的质量组成为：15％A（Al2O3）、15％B（NH4HCO3）、8％C（C6H7O6Na）和62％D（H2O）。用造孔材料做球种制造的中空球形催化剂载体的理化性能基本与实心相差不大,抗压强度略有下降,堆积密度的大幅度下降能够满足生产的需要。     

天然气蒸汽转化催化剂的活性与物化性能的关系

通过实验经验和理论计算指出，天然气蒸汽转化催化剂的活性主要与孔结构和活性表面的大小有关，与比表面的关系不大。其次，催化剂要求有高温下稳定的载体和一定的机械强度，指出低镍含量、小比表面、大孔发达、总孔容大的催化剂是较为理想的蒸汽转化催化剂。     

HA2Q型球形催化剂合成氨动力学的初步研究

本文对氨合成钴铁球形催化剂的的活性和动力学做了初步研究,在较广阔的压力、空速、温度范围内,探讨了杰姆金动力学方程对该催化剂的适用性,讨论了指前因子与活化能的关系,并用动力学参数考察了该催化剂的活性及耐性热。     

超轻发泡水泥保温板孔结构与性能关系研究

发泡水泥中的孔结构在很大程度上决定了材料的力学和热学性能.为了深入研究发泡水泥的孔结构与力学和热学性能的关系,本文利用图像分析法表征了发泡水泥的孔结构参数(气孔率、气孔尺寸),测试了材料的抗压强度和导热系数.研究结果表明:气孔率、孔壁厚度、气孔尺寸对干密度、抗压强度以及导热系数均有影响.随着气孔率的增大,干密度、抗压强度和导热系数均呈现下降趋势;在相同容重下,导热系数随着平均孔径的增大而升高,抗压强度随之减小,发泡水泥的孔径每增大1 mm,则抗压强度减小25％ ～ 30％;气孔尺寸分布近遵循对数正态分布(R2=0.95),高密度的发泡水泥的对数正态分布拟合相关系数相对较高.     

合成温度对VPO催化剂比表面的影响

在不同的温度下制备VPO催化剂，采用BET、XRD和SEM等测试手段考察制备温度对催化剂的比表面及晶相结构的影响。实验结果表明，温度对比表面和晶相结构的影响存在一个最佳值。选择适宜的制备温度可以使催化剂晶粒变小，比表面增大，活性相含量增加。     

A301型氨合成催化剂物理化学性能

系统研究了A301型氨合成催化剂还原前、后的物化性能和宏观结构,并与传统熔铁催化剂作了比较.研究结果表明,催化剂的比表面积和孔结构是在还原脱氧过程中产生的,还原前的催化剂可视为无孔隙的致密固体.A301的比表面积和α-Fe晶粒度与A110-2相同,但α-Fe表面积和碱表面积比A110-2小,而酸表面积比A110-2大.A301的堆密度和颗粒密度均比A110-2大,但真密度比A110-2小.A301催化剂的孔容积、孔隙率和孔径都比传统催化剂小,这与Nielsen A的研究结果不一致.Fe_(1-x)O对基的A301催化剂活性的提高,不是因为它的比表面积或孔径增大,也不是因为它的含铁量增加,而是由于Fe_(1-x)O还原得到的α-Fe的表面性质(例如酸表面积增大)和表面结构发生变化,使比活性提高之故.     

Characterization of the compaction and sintering of hydroxyapatite powders by mercury porosimetry

Mercury porosimetry was used to measure the bulk and real densities, pore volumes and pore size distributions of compacts of hydroxyapatite before and after sintering. The hydroxyapatites were prepared by two different methods and had widely different surface areas. The properties were determined as a function of compaction force and sintering temperature. Densities from porosimetry were in good agreement with geometric densities. A linear relation was found between pore volume and log of the applied force. There was also a linear relationship between bulk volume and pore volume of the compacts. A bimodal pore size distribution was observed for the high surface area hydroxyapatite which disappeared with increasing compaction loads. Pressurization and depressurization measurements indicated that the main body of the pores in the compacts attained a more regular “spherical” shape with increasing compaction force than did the “necks”. The pore volume, percent porosity, and bulk density of the compacts remained unchanged up to 600°C; however, the surface area and the average pore diameter changed at 400°C. The distribution of pores became more uniform, narrower in distribution, and larger in size as the sintering temperature increased. The change in pore area with pore volume indicated that two mechanisms were operating during sintering. The pore area proved to be the most sensitive indicator of changes during sintering.     

A comparative study of porous scaffolds with cubic and spherical macropores

Two kinds of polyester porous scaffolds having cubic and spherical macropores were fabricated, and a comparative study of their morphologies and mechanical properties were made in this paper. Poly(d,l-lactic-co-glycolic acid) (PLGA) scaffolds were prepared by room temperature compression molding and particulate leaching method based on cubic NaCl particles and paraffin spheres with a similar size range of 355-450 μm and a series of porosities (77-97%). Scanning electronic microscopy demonstrated that the spherical pore scaffolds exhibited better pore interconnectivity than the cubic pore ones. In compressive tests of both kinds of scaffolds, striking yield peaks were found at relatively low porosities, but just non-linear flexure behavior was observed at high porosities. The power-law relationships of compressive modulus and compressive strength versus porosity were confirmed in both foams. Comparison of the underlying scaling exponents reveals that the scaffolds with spherical pores are, at high porosities, with better compressive properties to a certain degree in contrast to those with cubic pores.     

Influence of porosity on PE molecular weight from the Phillips Cr/silica catalyst

The porosity of Phillips Cr/silica catalysts plays a major role in determining the molecular weight (MW) and molecular weight distribution obtained during ethylene polymerization. A survey of the many different families of silica was made to evaluate this connection. No one single physical catalyst property, such as surface area, pore volume, radius of curvature, or average pore diameter, could be universally correlated with the MW of polyethylene. Instead the data seem to suggest that the trends observed are the result of two independent influences. First, pore volume determines the fragility of the catalyst, which governs the degree of fragmentation during polymerization, and the fragment size. Secondly, pore diameter controls how easily the polymer can escape from the interior of the fragment. These variables are explored, and possible explanations for the observed behavior are discussed.     

载体形状和粒径对Pd/Al2 O3蒽醌加氢性能的影响

研究不同形状和颗粒大小的载体对Pd/Al_2O_3加氢性能的影响,结果表明,载体形状和粒径不影响其比表面积、孔容、孔径和活性组分在表面的粒径分布。齿球形和三叶草形催化剂比球形催化剂有更大的外表面积和更小的内扩散阻滞,从而表现出更好的催化性能。小尺寸催化剂表现出较高的加氢性能和较低的选择性,是因为有较大的外接触表面积和较小的床层空隙率。催化剂粒径为3. 0 mm×3. 1 mm时,催化剂氢化效率达8. 40 g·L~(-1),选择性97. 8%。     

球形纤维素纳米纤丝气凝胶的制备及性能表征

以桉木纸浆为原料,制备了不同纤维素质量分数（1%、1.5%、2%和2.5%）的球形纤维素纳米纤丝（CNF）气凝胶。通过扫描电子显微镜（SEM）、全自动比表面积与孔隙度分析（BET）仪、傅里叶变换红外光谱（FT-IR）仪、组合型多功能水平X射线衍射（XRD）仪和热重分析（TG）仪等技术对制备的CNF气凝胶的进行表征。结果显示：制备的CNF气凝胶为球状,是一种具有三维网络结构的介孔材料,其密度为0.0248~0.0427 g/cm³,孔隙率≥97.33%,孔径≤19.4 nm。该气凝胶材料具有纳米纤维素的红外特征峰,其晶型结构仍然为纤维素Ⅰ型结构,且拥有良好的热稳定性,当CNF质量分数为2%时,气凝胶的最大失重速率温度（T_max）为306.52 ℃。伴随着CNF质量分数的增加,CNF气凝胶的密度、孔隙率逐渐减小,孔体积、BET比表面积先增大后减小,孔径先减小后增大。     

球形氧化铝制备过程中影响因素的研究

介绍了球形氧化铝的各种制备工艺及成形方法，并以油柱成形法制备球形氧化铝。利用低温液氮吸附仪、压汞仪以及智能强度测定仪对其物化性质进行了测定，重点考察了不同铝源合成的水合氧化铝、加料方式、扩孔剂和胶溶剂用量对球形氧化铝性质的影响。实验结果表明，制备水合氧化铝的铝源是影响球形氧化铝的重要因素；并流加料方式能制得大孔容、低表观密度、高强度的球形氧化铝；球形氧化铝的制备过程中，要制得适合于油柱成形的铝溶胶，胶溶剂加入量有最佳的用量范围，胶溶剂用量愈大，球性氧化铝的强度、比表面、孔容愈大，而孔径却随之变小；活性炭粉能有效地提高球形氧化铝的压汞孔容。     

低渗透储层的微观孔隙结构特征研究

本文以鄂尔多斯盆地低渗透储层为例,在岩芯观测、岩石薄片、铸体薄片、扫描电镜以及压汞资料分析的基础上,分析了该地区低孔低渗砂岩的岩石学特征、储层物性及微观孔隙结构特征;分析了储层有效喉道半径、有效喉道体积、有效孔隙半径、有效孔隙体积及孔喉比等特征参数与孔隙度、渗透率之间具有较好的相关性。     

Effect of Porosity in Catalyst Layers on Direct Methanol Fuel Cell Performances

Effects of porosity of catalyst layers (CLs) on direct methanol fuel cell (DMFC) performances are investigated using silicon dioxide (SiO₂) particles as a pore former. The pore size and volume of CLs are controlled by changing the size and content of SiO₂. As the size of pore formed by removal of SiO₂ increases, DMFC performances are enhanced. The augmentation in performances can be explained by facilitation of fuel transport to catalyst particles, increase of utilization efficiency of catalysts, diminishment in methanol crossover, reduction in activation loss and facilitation of water discharging out of CLs of cathode due to the controlled porosity in CLs. The enhanced fuel transport, accessibility of fuels to Pt catalyst surface, is proved by the active areas of Pt catalyst. In addition to the active area of Pt catalyst, porous CLs exhibit a decline in methanol crossover, leading to increase of open circuit voltage (OCV). The porous CLs also show improvements in activation loss due to high porosity, causing enhancement in DMFC performances. In aspect of pore volume contribution to cathode performance, the SiO₂ content is optimized. Based on the DMFC performances, it can be suggested that the optimum conditions of SiO₂ are 500 nm in size and 20 wt.% in content. The porosity effect on both electrodes appears as follows: the pores in cathode are more effective on DMFC performances (55.5%) than those of anodes (44.5%) based on the maximum power of DMFC, indicating that the pores in CLs facilitate removal of water from electrodes.     

Contribution to the study of the submicroscopic structure of macroporous polymers. Calculation of the magnitude of submicroscopic particles and pores from specific pore volumes and specific surfaces

A model series of ordering of submicroscopic spherical particles forming the basic structure of macroporous copolymers is suggested by analogy with elementary crystallographic lattices. This series with various porosity (p=25.95-78.53%) allows not only the calculation of the mean radius of submicroscopic particles, but also a better choice of the coefficient used in calculating the mean pore radius from specific pore volumes and specific surfaces. A general method of calculation of the mean particle radius and of the mean pore radius for macroporous copolymers is also proposed, and a comparison with real systems is made.