Papers by Keyword: Mesoporosity

Abstract: Prototype of FCC catalyst were formulated by mixing the stabilised Y zeolites (68wt%) with polyvinal alcohol (PVA) (7%) as a solution binder and bentonite (25%). The Y zeolite including the original HY with Si/Al of 2.6 (cat.-2.6) and dealuminated HY with Si/Al of 30 (cat.-30) were used and tested for catalytic cracking of Iraqi vacuum gas oil (VGO) obtained from Al-Dura refinery using a pilot plant. The cracking process was carried out at a temperature of 520 °C and atmospheric pressure, The weight ratio of catalyst / oil ratio was 3 and 5. The results show that higher conversion of 77 wt. % and better product distribution (gasoline, kerosene and gas oil) could be obtained over cat.30 resulting to a good liquid product yield. The catalytic activity, in terms of VGO conversion was not affected over cat.-30 in spite of its lower acidity, suggesting the determinate of mesoporosity in the Y zeolite (cat.-30) catalysed cracking reactions. A higher yield of ~ 67 wt% to mid-distillates (i.e.Naphtha and kerosene) was as a result of the improvements in the diffusion to and from catalyst structure.

Abstract: Activated carbons (ACs) were successfully prepared using plane tree seed (PTS) as a cheap and renewable raw material. The plane tree seeds were firstly treated combining magnetic (MM) and ultrasonic mixing (USM) during 0.5, 1 and 3 h in 1 M, 3 M and 6 M of H3PO4 solutions, and then activated at 260 °C during 20 h (low temperature hydrothermal carbonization–low HTC) in above mentioned solutions of the same molarity. The influence of combined mixing and activation processes on physical, structural and morphological properties, and their optimization was studied by X-ray powder diffraction (XRPD), Raman spectroscopy, nitrogen adsorption-desorption isotherms, fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis.

Abstract: Micro-and mesoporous ceramics demonstrate promising properties for applications in energy-and environment-related fields. Due to their high thermal and chemical stability, they are particularly suited for separation in harsh thermal or chemical environments, e.g. as membrane materials for the separation of gas mixtures. In this work, we present the use of a preceramic poly(vinyl)silazane in combination with organic molecular porogens for the generation of micro-/mesoporous non-oxide ceramic structures. Microporosity is generated during the pyrolytic conversion process, while the addition of molecular porogens, to be removed during the heat-treatment, enables further control of the micro-/mesopore structure. A systematic investigation of various porogens showed the suitability of polystyrene for this purpose. Based on these findings, the pore structure and pore connectivity of polysilazane/polystyrene-derived structures were evaluated using gas physisorption and small angle X-ray scattering techniques. This material was further investigated by preparing asymmetric membranes consisting of micro-/mesoporous polysilazane/polystyrene-derived layers on porous ZrO₂/TiO₂ supports. The potential for gas separation applications was then demonstrated by single-gas permance evaluation of the generated structures at temperatures up to 300 °C.

Abstract: Monometallic Ce, Cu and bimetallic Ce-Cu was successfully synthesized at room temperature using silica rice husk (RH) via sol-gel route and were characterized through several physicochemical techniques such as N₂ adsorption-desorption, XRD and DR/UV-Vis analyses. The prepared materials were designated as RH-10Cu, RH-20Ce and RH-10Cu20Ce. High mesoporosity with Type IV characteristics were evidenced for all the materials. The BET surface area registered for RH-10Cu, RH-20Ce and RH-10Cu20Ce were 396.02, 245.54 and 194.87 m²g^-1 respectively. Well-dispersion of metal species was clearly evidenced from XRD analysis. The strong interaction between ceria and copper was observed over RH-10Cu20Ce through DR/UV-Vis analysis.

Abstract: Zeolites are among the main catalysts in the petroleoum and fine-chemical industry. The well-defined channel framework with the acid sites have empowered this kind of material to catalyze many chemical reactions, such as alkylation, isomerization, and hydrocarbon cracking. Controlling the energy consumption towards efficient process in the synthesis of zeolite has been a great interest. In this light, we succesfully show that synthesis of MFI zeolite can be tailored by using high or low temperature heating. Synthesis via high-temperature heating (HTH) at 150 °C, resulted in conventional coffin-type morphology whereas low-temperature heating (LTH) at 90 °C, resulted in a spherical-type morphology. This phenomenon indicates that energy consumption for synthesizing MFI zeolite can be decreased. Moreover, the tetrapropylammonion ion (TPA⁺) amount as structure-directing agents (SDA) can be lowered, hence reducing the synthesis cost. The obtained samples were charaterized by advanced techniques to compare interesting properties between samples synthesized by HTH and LTH. This concerns on the resulting morphology, textural properties, and Si/Al framework ratio.

Abstract: Hydrogen generated from clean and renewable energy sources has been considered as an alternate fuel to carbon based fossil fuels for several decades. Although many advances in hydrogen production and usage have been made, storing hydrogen remains a significant challenge. Many drawbacks including energy intensive processes, low volumetric densities, and safety concerns are associated with storing hydrogen as pressured or liquefied. Solid state hydrogen storage is considered to be the most promising method as a safe and effective storage option, but there is still no material or method that satisfies the requirements for a practical approach. A feasible hydrogen storage media should address several issues including targeted storage capacities, thermodynamics and hydrogen sorption kinetics, and safety. Nanostructured materials can provide tailor-made properties for storing and releasing hydrogen to fulfill, at least, the partial requirements. This short review, not a comprehensive review of all the materials or technologies in hydrogen storage, summarizes some of the recent developments in application of nanostructures for solid state hydrogen storage; particular attention has been devoted to the most recent development of nanocomposites with tuned dehydrogenation temperatures and kinetics through the control of pore size and surface chemistry.

Abstract: Tissue-engineering scaffold-based strategies have suffered from limited cell depth viability when cultured in vitro, with viable cells existing within the outer 250-500μm from the fluid-scaffold interface. This is primarily believed to be due to the lack of nutrient delivery into and waste removal from the inner regions of the scaffold construct. Other issues associated with porous scaffolds involve poor seeding efficiencies and limited cell penetration resulting in heterogeneous cellular distributions. This work focuses on the development a novel hydroxyapatite multi-domain porous scaffold architecture (i.e. a scaffold providing a discrete domain for cell occupancy and a separate domain for nutrient delivery) with the specific objectives of embodying in one scaffold the structures required to optimise cell seeding, cell proliferation and migration and potentially to facilitate vascularisation once implanted in vivo. This paper presents the development of the multidomain architecture and preliminary results on cell viability which show a significant improvement in cell viability in the scaffold interiors.