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Micropore Volume (micropore + volume)
Selected AbstractsHierarchical Zeolite Catalysts: Zeolite Catalysts with Tunable Hierarchy Factor by Pore-Growth Moderators (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Mater. On page 3972, Pérez-Ramírez et al. introduce the hierarchy factor as a valuable descriptor to categorize hierarchical zeolites and to optimize their design for catalytic applications. They demonstrate a direct correlation between the catalytic performance of ZSM-5 in benzene alkylation and the hierarchy factor. Maximization of the hierarchy factor is achieved by enhancing the mesopore surface area without reducing the micropore volume. For this purpose, a novel desilication variant involving NaOH treatment in the presence of pore growth moderators (quaternary ammonium cations) is presented. [source] Zeolite Catalysts with Tunable Hierarchy Factor by Pore-Growth ModeratorsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Javier Pérez-Ramírez Abstract The design of hierarchical zeolite catalysts is attempted through the maximization of the hierarchy factor (HF); that is, by enhancing the mesopore surface area without severe penalization of the micropore volume. For this purpose, a novel desilication variant involving NaOH treatment of ZSM-5 in the presence of quaternary ammonium cations is developed. The organic cation (TPA+ or TBA+) acts as a pore-growth moderator in the crystal by OH, -assisted silicon extraction, largely protecting the zeolite crystal during the demetallation process. The protective effect is not seen when using cations that are able to enter the micropores, such as TMA+ Engineering the pore structure at the micro- and mesolevel is essential to optimize transport properties and catalytic performance, as demonstrated in the benzene alkylation with ethylene, a representative mass-transfer limited reaction. The hierarchy factor is an appropriate tool to classify hierarchically structured materials. The latter point is of wide interest to the scientific community as it not only embraces mesoporous zeolites obtained by desilication methods but it also enables to quantitatively compare and correlate various materials obtained by different synthetic methodologies. [source] DBD regeneration of GAC loaded with acid orange 7ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Guang-Zhou Qu Abstract Activated carbon (AC) has been widely used as adsorbent in various industrial applications, such as purification of water in sewage facilities and filtration of air in toxicity-treating factories. However, after exhaustion, AC should be regenerated and reused because of the limited resources for AC production and additional secondary pollution of spent-carbon dumped into water or soil. In this study, a process for regenerating AC based on high active species (O3, ·OH, HO2, O2, ·RO, etc.) generated by dielectric barrier discharge (DBD) oxidation was proposed. The regeneration of granular-activated carbon (GAC) exhausted with azo dye acid orange 7 was investigated to assay this method. The influences of the parameters, such as treatment time, electric field and gas kind, on the readsorption rate were studied systematically. The results of structural properties of GAC analyses showed that the surface area, the micropore area, external surface area, micropore volume and total volume of GAC after three cycles DBD treatment decreased to different extent. The adsorption isotherms indicated that the regeneration efficiency was about 81% after three times DBD plasma regeneration cycles, which confirmed the reuse feasibility of the regenerated GAC. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Porosity and surface characteristics of activated carbons produced from waste tyre rubberJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2002Guillermo San Miguel Abstract Waste tyre rubber has proven to be a suitable precursor for the production of high quality activated carbons. The performance of these carbons in commercial applications such as water treatment or gas purification is highly dependent on their surface characteristics. This paper presents an in-depth investigation on how production conditions may affect the yield and characteristics of activated carbons produced from tyre rubber. For this purpose, three tyre rubbers of different particle sizes were consecutively pyrolysed and then activated in a steam atmosphere at 925,°C using a laboratory-scale rotary furnace. Activation was conducted at different intervals over 80,640,min to achieve different degrees of carbon burn-off. The resulting carbons were analysed for their elemental composition, ash content and nitrogen gas adsorption characteristics. The BET and t -plot models were used to investigate various aspects of their porosity and surface area characteristics. SEM analyses were also conducted for visual examination of the carbon surface. Results show that pyrolytic chars, essentially mesoporous materials, developed a very narrow microporosity during the initial stages of the activation process (up to 15,25,wt% burn-off). Further activation resulted in the progressive enlargement of the average micropore width and a gradual development of the mesoporous structure. Total micropore volumes and BET surface areas increased continuously with the degree of activation to reach values up to 0.498,cm3g,1 and 1070,m2g,1 respectively, while external surface areas developed more rapidly at degrees of activation above 45,wt% burn-off. Results presented in this work also illustrate that carbons produced from powdered rubber developed a narrower and more extensive porosity, both in the micropore and mesopore range, than those produced from rubber of a larger particle size. © 2001 Society of Chemical Industry [source] | ||||||||||