Showing papers on "Mesoporous material published in 1988"

Preparation and Sintering of Colloidal Silica‐Potassium Silicate Gels

Abstract: Porous silica gelled from colloidal silica and potassium silicate mixtures as developed by Shoup has been investigated. Various gels exhibit an average pore size from 50 to 250 nm and a porosity up to 85%. Dealkalization by solution leaching is found to depend on the average pore size and is easier for large pore sizes. A domain model has been proposed for the gel networks to account for the observation of both macropores and mesopores as measured by Hg porosimetry and N2 desorption, respectively. The pore coarsening observed during sintering is explained by the material transport from areas around interdomain pores to those around intradomain pores in order to minimize the total surface energy.

Preparation of model mesoporous carbons

Abstract: The objective of this work was to prepare mesoporous carbon solids made of monosized spherical particles, produced from poly(acrylonitrile)(PAN) precursors, after oxidation in air and subsequent carbonization under an inert atmosphere. The precursors were obtained from PAN latices by slow drying in air. The PAN latices stabilized by ABA amphipathic block copolymers were prepared in n-hexane by means of dispersion polymerization. Transmission electron micrographs showed that the particles of the latex dispersions were small spheres with a narrow particle-size distribution. Scanning electron micrographs of the mesoporous carbon samples demonstrated that the particles were arranged either in a regular (orthorhombic) or in a random (disordered) type of packing. The resulting carbon particles were found to have suffered slight coalescence around points of contact. Surface roughness on the surface of the particles was also evident.

Modified Aluminophosphate Microporous Solids

Abstract: A combination of physical techniques, including FTIR, XRD, gas adsorption and thermal methods, have been used to characterise two modified ALPO-5 phases. The first of these, designated as ZAPO-5, was prepared by the incorporation of zinc at the crystallisation step, whereas the second, Si-ALPO-5, resulted from interaction with SiCl 4. The latter phase was found to possess mesopores as well as micropores. The surface acidity of both these solids and of pristine ALPO-5 was investigated.

Porosity and Pore Size Distribution in High Surface Area Monolithic Cellular Ceramic Catalytic Substrates

Abstract: High surface area extruded monolithic cellular substrates are being developed and evaluated for applications in the chemical process industries and for stationary emissions control. Alumina, 93% alumina + 7% silica, magnesium aluminate spinel, silicas, titania, and 91% titania +9% silica compositions are characterized in detail by porosity, pore size distribution and surface area as a function of heat treatment. Extruded high surface area alumina monoliths have the usual surface area and porosity characteristics of gamma alumina substrate material. However, the addition of silica increases the temperature stability and changes the pore size distribution from monomodal to multimodal, i.e. from 95 angstroms for 100% alumina to a material with mesopores concentrated at 70 and 140 angstroms plus pores extending from the mesopore to the macropore range, 0.02–0.18 microns. Titania is similar to alumina because the addition of silica also increases its thermal stability and changes the pore distribution from predominantly monomodal to bimodal. Silica compositions have surface areas that range upto 150 m2/g and have unique bimodal pore distributions. Data for magnesium aluminate spinel show high temperature stability for this material.