The synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described. MCM-41, one member of this family, exhibits a hexagonal arrangement of uniform mesopores whose dimensions may be engineered in the range of - 15 A to greater than 100 A. Other members of this family, including a material exhibiting cubic symmetry, have ken synthesized. The larger pore M41S materials typically have surface areas above 700 m2/g and hydrocarbon sorption capacities of 0.7 cc/g and greater. A templating mechanism (liquid crystal templating-LCT) in which surfactant liquid crystal structures serve as organic templates is proposed for the formation of these materials. In support of this templating mechanism, it was demonstrated that the structure and pore dimensions of MCM-41 materials are intimately linked to the properties of the surfactant, including surfactant chain length and solution chemistry. The presence of variable pore size MCM-41, cubic material, and other phases indicates that M41S is an extensive family of materials.

http://dns2.asia.edu.tw/~ysho/ysho-english/1000 wc/pdf/j ame che soc114, 10834.pdf

A new family of mesoporous molecular sieves prepared with liquid crystal templates

A brief history and review of geopolymer technology is presented with the aim of introducing the technology and the vast categories of materials that may be synthesized by alkali-activation of aluminosilicates. The fundamental chemical and structural characteristics of geopolymers derived from metakaolin, fly ash and slag are explored in terms of the effects of raw material selection on the properties of geopolymer composites. It is shown that the raw materials and processing conditions are critical in determining the setting behavior, workability and chemical and physical properties of geopolymeric products. The structural and chemical characteristics that are common to all geopolymeric materials are presented, as well as those that are determined by the specific interactions occurring in different systems, providing the ability for tailored design of geopolymers to specific applications in terms of both technical and commercial requirements.

Geopolymer technology: the current state of the art

The Hydrothermal Synthesis of Zeolites: History and Development from the Earliest Days to the Present Time

Preface. 1. Introductory Remarks. 2. Fundamental Factors for Designing Adsorbent. 3. Sorbent Selection: Equilibrium Isotherms, Diffusion, Cyclic Processes, and Sorbent Selection Criteria. 4. Pore Size Distribution. 5. Activated Carbon. 6. Silica Gel, MCM, and Activated Alumina. 7. Zeolites and Molecular Sieves. 8. &pi -Complexation Sorbents and Applications. 9. Carbon Nanotubes, Pillared Clays, and Polymeric Resins. 10. Sorbents for Applications. Author Index. Subject Index.

/pdf/adsorbents-fundamentals-and-applications-2732spmgdj.pdf

Adsorbents: Fundamentals and Applications

The hydrothermal synthesis of zeolites: precursors, intermediates and reaction mechanism

Hydrothermal Chemistry of Zeolites

The crystal structure of the synthetic zeolite, Linde L, K6N aaA19Si27072 . 21H20, has been determined from powder data at room temperature. The zeolite is hexagonal with unit-cell dimensions a = 18.4 A and c = 7.5 A. The structure has been refined assuming space group P6/mmm. The aluminosilicate framework is based upon the polyhedral cages which are formed by five six-membered and six four-membered rings and are found in can- crinite, erionite and offretite. These cavities are linked through the planes of their upper and lower six-membered ring, thus forming columns in which hexagonal

The crystal structure of the synthetic zeolite L

An account has been given of four modes of sorption based on clay minerals and their cation exchanged and pillared forms. non-polar molecules on outgassed layer s tructures containing only inorganic interlayer cations such as Na+ or Ca2+ is confined to external surfaces only. palygorskites. layer structures, but only after a threshold pressure is exceeded. thermodynamic basis of this behaviour has been given. space is completely filled by long chain organic cations, as in dimethyldioctadecylammonium montmorillonite, imbibition with swelling can occur to an extent governed by the cohesive energy density of the sorbate relative to that of the interlayer region. for aromatics and heterocycles. Finally, after exchange with organic cations or with inorganic oxy-cations which permanently expand the inter- layer region but do not fill all the space, a diverse range of microporous sorbents can be produced which possess many zeolite properties such as shape-selective sorption. Some aspects of these sorbents are discussed. Sorption of

/pdf/clay-minerals-as-selective-and-shape-selective-sorbents-2k6e58hrjk.pdf

Clay minerals as selective and shape-selective sorbents

Molecular sieve adsorbents

Zeolite synthesis has been considered in terms of factors influencing the species formed and aspects important for systematic study. Zeolites can be divided into categories according to the Si/A1 ratios. Synthesis behaviour varies to some extent between the most aluminous and most siliceous groups. Synthesis of the most siliceous zeolites, which tend to be hydrophobic, is promoted by many organic species, usually basic in nature. Two roles of such compounds have been indicated. Firstly, the host crystal is stabilised by inclusion of guest molecules. This has a thermodynamic basis and is considered specifically in connection with the synthesis of melanophlogite. Secondly, a component of the mixture may act as a template assisting nucleation and crystal growth. Finally, attention has been directed to the method of analysis of curves of yield of crystals against time, developed by Zhdanov and Samulevich. This requires measurements of linear growth rates of the largest crystals and of the final size distribution of crystals.

Richard M Barrer

Papers

Hydrothermal Chemistry of Zeolites

The crystal structure of the synthetic zeolite L

Clay minerals as selective and shape-selective sorbents

Molecular sieve adsorbents

Synthesis of Zeolites