The membrane properties of alumina-coated alumina support layers and alumina-coated diatomite–kaolin composite support layers

ABSTRACT

Porous ceramic membranes are a current research focus because of their outstanding thermal and chemical stability. Recent research has utilised inexpensive natural materials such as diatomite to reduce the expense of these porous ceramic membranes. However, insufficient data exist for microfiltration applications using the diatomite-based membranes. The measured membrane properties of alumina-coated alumina support layers and alumina-coated diatomite–kaolin composite support layers have been compared. These experiments have been used to determine whether the average pore size could be reduced effectively by controlling the thickness of the alumina coating layer, while maintaining acceptable water permeability. The membrane properties of the alumina-coated alumina support layers and the alumina-coated diatomite–kaolin composite support layers were examined using the scanning electron microscopy, mercury porosimetry, and a dead-end microfiltration system.     

以低温固相碱熔活化高岭土为原料合成ZSM-5分子筛

以天然矿物高岭土为主要硅铝原料,经低温固相碱熔活化后,在常规水热条件下合成ZSM-5分子筛,考察m(高岭土)∶m(氢氧化钠)、碱熔温度及碱熔时间等因素对高岭土活化效果的影响。采用XRF、XRD、FT-IR和N2-吸脱附等对不同样品进行表征。结果表明,在m(高岭土)∶m(氢氧化钠)=1∶1.5、碱熔温度250℃和碱熔时间30 min条件下,可以实现高岭土完全活化。该活化方式不仅降低了活化温度,且能在极短时间内提高高岭土活性。以最适宜低温固相碱熔活化条件下所得活性硅铝物质为主要原料,硅溶胶为外加硅源,采用水热法合成高相对结晶度的纯相ZSM-5分子筛。与工业ZSM-5分子筛相比,合成ZSM-5分子筛具有更大的比表面积和孔容。     

xCeO_2/高岭土催化剂上丙烷氧化脱氢制丙烯

采用浸渍法制备不同CeO_2负载量的xCeO_2/高岭土催化剂,采用XRD、N_2吸附-脱附、H_2-TPR和XPS等对催化剂物化性质进行表征。将xCeO_2/高岭土催化剂应用于丙烷氧化脱氢反应中,考察CeO_2负载量对丙烷氧化脱氢反应的影响,同时对催化剂进行原位电导测试。结果表明,CeO_2负载质量分数8%时,CeO2/高岭土催化剂的催化性能最好,500℃时,丙烷转化率为17.92%。在氧-丙烷-氧+丙烷连续变化的不同气氛下均显示了氧化还原可逆性。     

高岭土深加工技术研究的进展

较全面地介绍了高岭土的纯化处理、超微粉碎、煅烧和表面改性处理的试验研究和应用情况，为推动高岭土深加工技术的研究和开发提供了有效方法。     

采用化学漂白法提高湛江路西高岭土产品由度的研究

采用化学漂白法，对湛江路百高岭土从矿浆ｐＨ值、浓度、时间、温度、药剂用量等方面进行探索，制定出最佳的漂白方案，最终获得白度为８７％的高岭土精选产品．     

酸碱改性高岭土性能的研究 Ⅱ.比表面积和孔结构

研究了酸、碱改性高岭土的孔结构性质以及影响酸改性高岭土比表面积的因素。结果表明,多种酸反应体系相比,在Ａｌ２Ｏ３／ＨＣｌ体系中形成的酸改性白土具有明显的中孔分布,提高反应温度,中孔特征突出,孔道更加通畅。碱改性白土的吸附脱附等温线为Ⅳ型,具有典型的中孔特征。高岭土经过酸或碱改性,都可以获得平均孔径在４．０ｎｍ左右的中孔材料,但是碱改性白土的吸附量更大,孔分布更集中。另外,酸量和酸浓度适中才有利于提高改性高岭土的比表面积,提高反应温度和延长反应时间也可以增加其比表面积     

AN INVESTIGATION OF FACTORS AFFECTING THE VISCOSITY OF SUZHOU KAOLIN SUSPENSIONS

Factors affecting the viscosity of the concentrated kaolin suspensions of Suzhou kaolins were studied. Experiments were carried out to use different kinds of dispersants to reduce the viscosity of the concentrated kaolin suspensions. The results indicated that good effects on reducing the viscosity of the concentrated kaolin suspensions were achieved by using the dispersants prepared in this laboratory , especially the combination of dispersants D III plus D IV . The viscosity of the concentrated kaolin suspensions was reduced from greater than 10000 MPa ' s to less than 500 MPa s. Analytical tests indicated that in the presence of the dispersants the surface properties were the major factors affecting the viscosity. The action of the dispersants is to change the surface properties rather than the morphology and structure of the minerals in the kaolin ores. The addition of the dispersants increased the hydrophilicity of particle, surfaces and the electrostatic repulsion between particles, resulting in i     

Leaching of kaolin iron-oxides with organic acids

Bleaching of kaolin with a high content of iron oxides by means of three organic acids (citric, gluconic and oxalic) was studied. The first two release small quantities of iron oxides from the kaolin, which means they will not be adequate for large-scale processes. Oxalic acid is capable of dissolving all the leachable iron in kaolin, reaching a whiteness index of 80%, thus making the kaolin suitable for its basic industrial applications. ©1997 SCI     

造纸黑液混凝处理中助凝剂的替代性研究

造纸黑液的处理常采用聚合氯化铝（PAC）作混凝剂、聚丙烯酰胺（PAM）作助凝剂。但是PAM价格很高,本文目的在于寻求一种PAM替代物。通过混凝实验比较,采用粉煤灰或高岭土作为助凝剂可以与PAM作为助凝剂达到相当的污染物去除效果。采用粉煤灰或高岭土作为助凝剂可以大大降低生产运行成本。