Preparation and characterization of poly(ethyl acrylate)/bentonite nanocomposites by in situ emulsion polymerization

Transparent poly(ethyl acrylate) (PEA)/bentonite nanocomposites containing intercalated-exfoliated combinatory structures of clay were synthesized by in situ emulsion polymerizations in aqueous dispersions containing bentonite. The samples for characterization were prepared through direct-forming films of the resulting emulsions without coagulation and separation. An examination with X-ray diffraction and transmission electron microscopy showed that intercalated and exfoliated structures of clay coexisted in the PEA/bentonite nanocomposites. The measurements of mechanical properties showed that PEA properties were greatly improved, with the tensile strength and modulus increasing from 0.65 and 0.24 to 11.16 and 88.41 MPa, respectively. Dynamic mechanical analysis revealed a very marked improvement of the storage modulus above the glass-transition temperature. In addition, because of the uniform dispersion of silicate layers in the PEA matrix, the barrier properties of the materials were dramatically improved. The permeability coefficient of water vapor decreased from 30.8 x 10(-6) to 8.3 x 10(-6) g cm/cm(2)s cmHg. (C) 2002 Wiley Periodicals, Inc.

Heterogenization of heteropolyacids: A general discussion on the preparation of supported acid catalysts

Heteropolyacids (HPAs) possess both acidic and redox catalytic properties and held extensive promise of practical application. These type of compound display a great potential of specific synthesis reactions for replacing sulfuric acid to satisfy the requirements of environmental protection. Heterogenizing HPAs would not only make them more useful in liquid phase oxidation with oxygen and in acid-catalyzed reaction, as the catalyst is often difficult to separate from the reaction products, but also create favorable factors for realizing heterogenization of homogeneous reaction and even utilizing new technology of catalytic distillation. In this paper, different kinds of porous materials which are well characterized, including oxides such as Al2O3, SiO2, TiO2, diatomite, bentonite, and active carbon of different sources, were used as support for heterogenizing HPAs (in different media), and the obtained results, the intrinsic characters of supports which may influence both the nature of the interaction between HPAs and supports in the heterogenization and the activity in the catalytic reaction, are explored. It is expected that these can provide a referential model for preparing supported acid catalyst used in liquid phase.

膨润土酸化脱色机理研究

膨润土（Bentonite���又名“斑脱岩”“膨土岩”“（左土右般）土”一般是指主要由蒙脱石组成的一种粘土岩，其中往往含有种类、数量和比例很不相同的其它杂质，由于膨润土具有许多特殊的物化性质强吸附性，触变性、催化活性、阳离子交换性能等。因而可作为粘结剂、吸附剂、填充剂、催化剂、触变剂、稳定剂、增稠剂等。己在一百多个不同生产部门中得到广泛利用。膨润土虽然用途繁多。但其主要用途（约占总产量的百分之七十五以上）用于泥浆、铁矿球团、铸造及油脂脱色等。经过酸化后的膨润土，主要用于矿物油、植物油、动物油的脱色和净化、国际、国内对它的需求量都相当大。目前国际上对于环境污染问题相当重视，导致许多厂家因废酸处理不当而停止生产，因而有人建议：研究低污染的活化工艺；探导用酸量低的就能制成活性土的新型粘土矿物。开展的“氢化”代替“酸化”的新工艺研究。但目前对于蒙脱石酸处理的敏感性的控制因素是什么？以及蒙脱石的脱色机理怎样等一些问题基本上都没有解决。因而，上面这些建议到目前为止还仅仅是建议而已。本文尝试着对上面这些问题作出回答。并附带着对我国最大的广西宁明膨润土矿作为活性土的潜在利用价值方面作出回答。