Papers by Keyword: Silica-Alumina

Abstract: Platinum (Pt), a noble metal, is known for its ability to regenerate and be recycled even without any reactivation procedure, and still demonstrated good stability. The cost of the noble metal can be reduced by incorporating the metal into the pores of catalyst support rather than using it individually. Hence, in this research study, 4 wt.% Pt supported on silica-alumina (SiO₂-Al₂O₃) and gamma-alumina (γ-Al₂O₃) was synthesized using wet impregnation method, then followed by catalyst calcination at 500 °C. The catalyst was then characterized using Thermogravimetric Analysis (TGA), Fourier-Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and particle size analyzer where catalyst with high surface area and pore volume demonstrated an excellent performance for the catalytic reaction of cellulose. Experimental results showed that catalyst Pt/SiO₂-Al₂O₃ with the highest surface area and pore volume (466.4 m²/g and 0.1157 cm³/g, respectively) exhibited the highest catalytic performance with the conversion of cellulose up to 65.8% and 30.9% levulinic acid (LA) yield produced at the reaction temperature of 200 °C in a semi-batch reactor for 8 hrs.

Abstract: Developing an environmentally friendly and high-quality of fuel from vegetable oil (triglycerides) have attracted a great attention among the researches. Deoxygenation reaction using Ca-based catalyst is a potentially promising element for removing an oxygen species from organic compounds and converting the molecule to hydrocarbon. Addition of transition metal in the catalysis synthesis studies not only could enhance the properties of the catalyst but also could tune the selectivity toward desired product. Cooperation of mesoporous support such as silica alumina (SA) exhibit unique and excellent properties (high surface area, high porosity) which simultaneously could increase the catalyst activity. In the present studies, a set of bifunctional acid-base supported on the highly mesoporous SA doped with Ca and Ni were synthesized. The Ca (NO)₃ and Ni (NO)₃ were impregnated on the mesoporous SA support and were calcined at 500 °C for 2 h in order to activate the synthesized catalyst. The physicochemical properties of the catalyst were characterized by X-Ray fluorescence spectroscopy (XRF), X-Ray diffraction spectroscopy (XRD), temperature programme desorption carbon dioxide (TPD-CO₂) and temperature programme desorption ammonia (TPD-NH₃) and scanning electron microscopy (SEM).

Abstract: Dimethyl Ether (DME) an alternative fuel was synthesized by methanol dehydration over the silica-based catalysts. Silica extracted from both rice husk (A) and rice-husk ash (B) was used as the precursors for preparing the catalysts. The SiO₂/Al₂O₃ and the SAPO catalysts prepared from that silica were analyzed using X-ray diffraction (XRD), N₂ adsorption (BET surface area), X-ray fluorescence (XRF), NH₃ temperature-programmed desorption (NH₃-TPD), and thermal gravimetric analysis (TGA). The effects of reaction temperature on the methanol selectivity and conversion to dimethyl ether were investigated. The methanol dehydration reactions were carried out in a packed-bed reactor at the reaction temperature of 250-350°C. DME was the major product and formed with selectivity of 57% over SAPO-B. An increasing of the reaction temperatures resulted in the enhancing of methanol conversion. The highest methanol conversion of 93% was achieved at 325°C. The method of silica extraction had an effect on the selectivity to DME due to the higher BET surface area.

Abstract: In the lost foam casting (LFC) of aluminum alloys, the expandable polystyrene (EPS) foam characteristics (foam composition, polymer processing and bead fusion) influence the formation of deleterious fold defects in the final casting. In this research, four types of EPS beads were investigated: (1) the regular EPS beads, (2) 2wt% hexabromocyclododecane and 2wt% dicumyl peroxide added to the EPS beads during the polymerization process, (3) 2wt% silicaalumina blended to EPS beads after the pre-expansion process of the beads and (4) 2wt% hexabromocyclododecane blended to EPS beads after the pre-expansion process of the beads. The density of the regular and modified EPS beads was kept constant at 25.63 kg/m3. Aluminum alloy A356 was poured at 1023 K into the window pattern. The window patterns with regular EPS beads did not fill completely and had identifiable carbon/oxide defects on the surface. The window patterns with the additives were completely filled with a few surface defects. From thermogravimetric analysis (TGA), it was found that the EPS beads with silica-alumina had a reduced onset temperature of degradation of EPS (from 634 K to 618 K) and a reduced activation energy (from 188 kJ/mol to 147 kJ/mol) relative to the regular beads. In the organic brominatedmodified EPS (both through blending and polymerization), it was found that the value of the preexponential (rate equation) was significantly increased. Through light optical microscopy (LOM) and scanning electron microscopy (SEM), it was found that the polymerization process additives increased the degree of bead fusion whereas the post pre-expansion additives decreased the degree of bead fusion. Finally, the EPS beads treated during the polymerization process produced castings with the least overall surface, subsurface and internal defects.