Mohamed A. Betiha

Direct synthesis and the morphological control of highly ordered mesoporous AlSBA-15 using urea-tetrachloroaluminate as a novel aluminum source

The synthesis of AlSBA-15 under mild acidic conditions was performed through adjusting the molar H2O/HCl ratio, which indicates the formation of Si–O–Al linkages that lead to isomorphous substitution of Si4+ by some Al3+ ions. In this paper, the direct incorporation of Al3+ onto a SBA-15 framework in acid mediated synthesis with a nSi/nAl molar ratio of 7 was optimized using urea tetrachloroaluminate ionic liquid as a new aluminum source. The hydrothermal temperature was varied from 80 to 140 °C and the samples were denoted as AlSBA-15(Ux). The conventional AlSBA-15 also was prepared using direct synthesis [AlSBA-15(D)] and post synthesis [AlSBA-15(P)] aiming to study the influence of aluminum sources and preparation conditions on their structural, textural, and physicochemical properties. The synthesized materials were characterized by N2 physisorption, XRD, FT-IR, Py-FT-IR, NH3-TPD, XRF, HRTEM and SEM. All preparation methods led to the formation of aluminum containing SBA-15 samples with different Si/Al contents. Nevertheless, depending on the preparation methods, the AlSBA-15 samples exhibited different structural, morphology, and surface characteristics, especially in terms of Bronsted and Lewis acid site content. AlSBA-15(U100) had high surface area (813 m2 g−1) and high acidity. TEM images of synthesized AlSBA-15(U100) showed well-ordered hexagonal arrays of uniform cylindrical channels. The effectiveness of AlSBA-15, as an acid catalyst, was studied for the esterification of acetic acid with butanol and cumene cracking. The high activity of AlSBA-15(U100) is attributed to its good ordered structure and high acidity.

Hafnium pentachloride ionic liquid for isomorphic and postsynthesis of HfKIT-6 mesoporous silica: catalytic performances of Pd/SO4 2−/HfKIT-6

Isomorphic substitution or post-synthesis incorporation of hafnium into KIT-6 mesoporous material has been fabricated for the first time in highly acidic media using triethylamine hafnium pentachloride ionic liquid (TEA-HfCl5) as a novel hafnium precursor ionic liquid (Si/Hf molar ratio of 90). The prepared catalysts were characterized by X-ray diffraction, Fourier transfer infrared (FT-IR), pyridine-FT-IR, N2-adsorption, transmission electron microscopy and the surface acidity was tested by temperature programmed desorption (NH3-TPD) of ammonia. The effect of the nature of hafnium source in the KIT-6 synthesis has been investigated using different hafnium source, viz., triethylamine hafnium pentachloride ionic and hafnium chloride. Triethylamine hafnium pentachloride ionic was found to be the better hafnium source for HfKIT-6 material synthesis and enhanced the amount of hafnium incorporation in the KIT-6 silica walls. ICP-AES studies evidenced that the proportion of Hf4+ increases using triethylamine hafnium pentachloride ionic. The catalytic performance of SO42−/HfKIT-6 was investigated by cracking of 1,3,5-triisopropylbenzene, esterification of acetic acid with n-butanol, while Pd/SO42−/HfKIT-6 was examined by n-C7 isomerization reaction. Our findings indicated that HfKIT-6 prepared by ionic liquid approach offered distinct structural and surface features, particularly in terms of Brønsted and Lewis acid site contents. As compared with SO42−/HfKIT-6 (direct ionic liquid) and SO42−/HfKIT-6 (direct), SO42−/HfKIT-6 prepared by post ionic liquid exhibited higher yield percentage of 1,3,5-triisopropylbenzene cracking and n-butyl acetate yield. Furthermore, Pd/SO42−/HfKIT-6 catalyst prepared by post ionic liquid shows high isomerization activities compared with Pd/SO42−/HfKIT-6 prepared by direct method using TEA-HfCl5 ionic liquid or HfCl4 materials.

Synthesis and thermal properties of nanocomposites based on exfoliated organoclay polystyrene and poly(methylmethacrylate)

Abstract Exfoliated organoclay-polystyrene (OC-PS) and organoclay-poly(methyl methacrylate) (OC-PMMA) nanocomposites were prepared using novel modified/clay-polymer through both bulk polymerization and solution techniques. The synthesis was achieved by formation of derivative vinylbenzyl ammonium salt intercalated with montmorillonite (MMT) clay. The clay-vinyl/monomer was dispersed in PS or MMA monomers followed by solution polymerization. The clay-PS and clay-PMMA were used as highly compatibilizer organoclay to produce highly exfoliated nanocomposites. Morphological structure of the nanocomposites was investigated by SEM and XRD which confirmed that the clay is homogenously dispersed and exfoliated in the polymer matrixes with interlayer spacing at least of d001-value ≥4 nm for both PS and PMMA. Thermal properties of the nanocomposites show an increase in the decomposition temperature comparing to neat polymer.

Optimization of batch Novozym435-catalyzed transesterification of waste cooking oil with methanol for biodiesel production in a solvent-free medium

ABSTRACT In this study, response surface methodology based on face center composite – 1/2 factorial fraction design (FCCD) of experiments was employed to optimize the batch transesterification process of waste cooking oil as one of the most abundant and readily available domestic wastes with methanol using immobilized Candida antarctica lipase (Novozym435) to maximize the production of high-purity biodiesel. Statistically significant second-order quadratic model equations (p < 0.0001) were elucidated through multiple regression analysis to describe the interrelationships between response of interest (biodiesel yield wt% and % conversion, i.e. the transesterification efficiency) and five independent variables (methanol:oil molar ratio, enzyme concentration wt%, reaction temperature °C, reaction time h, and mixing rate rpm). The statistical significance of the effect of these variables (factors) and their interactions on the transesterification efficiency was evaluated and the validity of the predicted models was confirmed. The optimum operating conditions were found to be: 3.63:1 M:O, 8.94 wt% Novozym435, 45.23°C, 2.76 h, and 535.84 rpm. This produced 97 wt% biodiesel yield with % conversion of ≈ 91.79%. An overall acceptable agreement was achieved between the produced biodiesel fuel properties at the aforementioned optimal operating conditions and the Egyptian petrodiesel and international biodiesel standards.

Facile tailoring of hierarchical mesoporous AlSBA-15 by ionic liquid and their applications in heterogeneous catalysis

Significant enhancement in the performance of incorporation of high content of aluminum within hierarchical mesoporous SBA-15 has been achieved by direct route using urea tetrachloroaluminate ionic liquid as novel aluminum source. The fabricated materials were fully characterized by N2 sorption isotherms, powder X-ray diffraction (XRD), FT-IR, 27Al MAS NMR, XRF, HRTEM and FESEM. The acidic properties of these materials have been examined using NH3-TPD. The catalytic performance was investigated using cumene cracking and the esterification reaction as a probe molecules to estimate the acidity of the material. It is worth noting that the ionic liquid with accomplished Al–O–Si bonds is an efficient precursor to synthesis AlSBA-15 with high aluminum content (nSi/mAl = 7) without destroying the structural order of the material in acidic medium. 27Al MAS NMR spectra of AlSBA-15 show that all aluminum species were incorporated into the SBA-15 framework with nSi/mAl ratio up to 7. Overall, this work emphasize that the AlSBA-15 materials contain Bronsted and Lewis acid sites with medium acidity which makes them adequate to be adopted as acid catalysts in heterogeneous catalysis.

Optimization of a batch CaO-catalyzed transesterification of used domestic waste oil with methanol and elucidation of a mathematical correlation between biodiesel yield and percent conversion

ABSTRACT The major drawback of the wide applicability of biodiesel is its price compared to the conventional petro-diesel. The feedstock and the applied catalyst in the transesterification reaction are the main contributor for the overall cost of the biodiesel production. Thus, this study summarizes the optimization of a batch transesterification reaction of used domestic waste oil (UDWO) with methanol using CaO, which can be easily prepared from different cheap and readily available natural sources. Quadratic model equations were elucidated describing the effect of methanol:oil molar ratio, CaO concentration wt.%, reaction temperature °C, reaction time h, and mixing rate rpm on biodiesel yield and conversion percentage. The optimum operating conditions were found to be competitive with those of the high-cost immobilized enzyme Novozym435. An overall acceptable agreement was achieved between the produced biodiesel, its blends with petro-diesel and the available commercial petro-diesel, and the international fuel standards. A precise and reliable logarithmic mathematical model was predicted correlating the production of pure high-quality biodiesel yield with the conversion percentage which were measured based on the fatty acid methylester content and decrease in viscosity, respectively.

Statistical enhancement of lipase extracellular production by Bacillus stratosphericus PSP8 in a batch submerged fermentation process

The aim of this study was to isolate and identify lipolytic bacteria. Perform a statistical stepwise physicochemical optimization for maximum production of extracellular lipase and its validation in a bioreactor.