Search results for "porous material"
showing 10 items of 361 documents
Transport of amino acids through liquid membranes supported on novel poly(vinylidenefluoride) porous flat-sheet matrix
1997
Flat-sheet membranes from poly(vinylidenefluoride) (PVDF) were prepared by the phase inversion process. LiCl was used as a modifying agent. The porosity, maximum pore size and LEPW (liquid entry pressure of water) were determined. Three types of these membranes were tested as a support for n-decanol supported liquid membranes (SLM). Transport of eight amino acids, selected to cover a wide variety of side chains, and of phenylalanine methyl ester through n-decanol SLM were studied. The ability of amino acids to permeates through these membranes depends on the type of flat-sheet PVDF used as a support. An increase in porosity and pore size of the microporous matrix resulted in an increase of …
Catalytic Performance of the New Delaminated ITQ-2 Zeolite for Mild Hydrocracking and Aromatic Hydrogenation Processes
2001
Abstract Catalysts based on NiMo and Pt supported on the new delaminated ITQ-2 zeolite have been prepared and their catalytic properties evaluated for the mild hydrocracking (MHC) of vacuum gasoil and aromatic hydrogenation. The results were compared with those obtained using other conventional supports, e.g., silica, γ-alumina, amorphous silica–alumina (25 wt% Al 2 O 3 ), and USY zeolite, all of which contain the same metal loading as the ITQ-2 material. In the case of MHC of vacuum gasoil, NiMo/ITQ-2 displayed a higher hydrocracking activity than NiMo/SiO 2 –Al 2 O 3 and NiMoγ-Al 2 O 3 , and even higher activity than NiMo/USY in the range 375–425°C. Moreover, NiMo/ITQ-2 had a selectivity …
A novel approach to polymer-template mesoporous molecular sieves
2000
A novel synthesis route was developed to produce spherical silica particles. The synthesis is based on a modified Stoeber method and the room-temperature synthesis of MCM 41S-materials applying tetraethoxysilane, alcohol, water, ammonia and homopolymers as template. The specific surface area, the specific pore volume and the average pore diameter were varied in the following ranges: 5 – 1,000 m2/g; 0.1 – 1.0 cm3/g and 2-50 nm. With respect to catalytic applications hetero-atoms e.g. Al were incorporated into the silica framework.
Synthesis of Microporous Carbon Nanofibers and Nanotubes from Conjugated Polymer Network and Evaluation in Electrochemical Capacitor
2009
One-dimensional fibers and tubes are constructed through the oriented carbon-carbon cross-linking reactions towards rigid conjugated polymer networks. As the result, a template-free and one-step synthesis of CNTs and CNFs is achieved through a simple carbonization of the as-formed carbon-rich tubular and fiberlike polyphenylene precursors under argon. Microporous CNTs and CNFs with a surface area up to 900 m2 g–1 are obtained, together with HR-TEM characterizations indicating the formation of intrinsic microporous structure in these rigid carbon-rich networks. The primary electrochemical experiments reveal their promising applications as advanced electrodes in electrochemical double-layered…
Electrical Voltage Control of the Pressure-Induced Spin Transition at Room Temperature in the Microporous 3D Polymer [Fe(pz)Pt(CN)4]
2019
Fine control and direct monitoring of the spin crossover properties driven by pressure at room temperature are reported for the porous three-dimensional coordination polymer {Fe(pz)[Pt(CN)4]} by us...
Enlarged pore size in nanoparticulated bimodal porous silicas: Improving accessibility
2016
Abstract Mass-transfer kinetics seems to be highly favored in siliceous materials constructed from the aggregation of mesoporous nanoparticles. Besides intra-particle mesopores, over the course of the aggregation process an inter-particle (textural) large pore system is generated. Diffusion constrains through the resulting hierarchically structured pore systems mainly depend on the characteristics of the intra-particle mesopores. By using alkanes as swelling agents, we have been able to significantly increase the intra-particle mesopore size in previously well characterized UVM-7 materials. The Winsor-III-like behavior associated with the presence of alkanes in the hydro-alcoholic reaction …
Mesoporous silicon carbide via nanocasting of Ludox® xerogel
2016
Porous SiC with uniformly sized 12 nm and 22 nm spherical mesopores was synthesized from nanocomposites of polycarbosilane (PCS) preceramic polymer and xerogels of Ludox® SiO2 nanoparticles as templates. The influence of PCS type (Mw 800 and 2000 Da), PCS : SiO2 ratio, pyrolysis temperature 1200–1400 °C, and addition of Ni complex to the preceramic composite was studied with respect to the SiC porous morphology, crystalline structure and chemical properties. We found that the pore walls of Ni-free por-SiC are composed of relatively large (20 nm) crystallites embedded inside a poorly crystalline SiC/SiC1+x phase. Increasing the pyrolysis temperature resulted in an increase of the large cryst…
Hierarchically Structured Titania Films Prepared by Polymer/Colloidal Templating
2010
Hierarchically structured titania films for application in hybrid solar cells are prepared by combining microsphere templating and sol-gel chemistry with an amphiphilic diblock copolymer as a structure-directing agent. The films have a functional structure on three size scales: (1) on the micrometer scale a holelike structure for reduction of light reflection, (2) on an intermediate scale macropores for surface roughening and improved infiltration of a hole transport material, and (3) on a nanometer scale a mesoporous structure for charge generation. Poly(dimethyl siloxane)-block-methyl methacrylate poly(ethylene oxide) (PDMS-b-MA(PEO)) is used as a structure-directing agent for the prepara…
Identification of Manganese(IV) Centers in Archaeological Glass Using Microsample Coatings Attached to PolymerFilm Electrodes
2001
Identification of MnO2 nodulae in archaeological glass by linear scan and differential pulse voltammetry using abrasive-conditioned microsamples attached to polymer film (Elvacite 2044) electrodes is described. Voltammetric responses for manganese-containing samples parallels to those obtained for β- and γ-MnO2 upon immersion of modified electrodes into NaCl, KCl and acetic/acetate aqueous media. The observed electrochemical response provides information on the open microporous structure of the MnO2 forms and the conditions of their formation during the weathering process of buried glass.
MCM-41 and related materials as media for controlled polymerization processes
1994
The synthesis of mesoporous MCM-41 type materials based on transition metal oxides and the polymerization of several monomers within MCM-41 is presented with the aim to specifically investigate the effects of the interface and confinement on host-guest interactions. In addition to standard MCM-41, material based on transition metal oxides is obtained although template removal has been unsuccessful for such compounds until now. In situ polymerization of styrene, methyl methacrylate and vinyl acetate is possible within the mesopore system. The properties of some of the encapsulated polymers differ markedly with those obtained in the bulk.