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Developing an earth-abundant catalyst that is sulfur-tolerant, active, and highly selective is of great interest for valorizing natural gas streams containing sour gas. A tin-modified alumina catal...

Converting the γ phase into the α phase completely is necessary in the presintering stage of industrial alumina (Al2O3), which requires high temperature and energy consumption. To reduce the presintering temperature, γ-Al2O3 was activated by oxalic acid. XRD, 27Al-MAS-NMR and TG-DSC were used to characterize the γ - alumina before and after activation, and the phase transformation was studied. The formation temperature of α-Al2O3 decreased to 1029 °C for oxalic acid activated γ-Al2O3, and the α-fraction was 100% for activated γ-Al2O3 at 1300 °C. After oxalic acid activation, the diffraction peak intensity of γ-Al2O3 decreased significantly; the results of 27Al-MAS-NMR suggested that octahedral [AlO6] in γ-Al2O3 was easier than tetrahedral [AlO4] to be attacked by oxalic acid, and the formation of pentavalent [AlO5] with higher reaction activity, which was in favour of the lowering formation temperature of α-Al2O3. The dissolution concentration of Al increased after oxalic acid activation, and the dissolution process was controlled by surface reactions. Oxalic acid mainly attacked the octahedral aluminium in γ-Al2O3 and extracted Al as three complexes of [Al(C2O4)]+, [Al(C2O4)2]- and [Al(C2O4)3]3-. Oxalic acid activated γ - Al2O3 with a lower phase transformation temperature has broad application prospects in the alumina industry.

A series of γ-alumina with different pore sizes (5.7 nm–21.6 nm) and similar specific surface areas were synthesized via an organic-free method and their adsorption rates and capacities for Congo red (CR), direct blue 78 (DB78) and direct green 26 (DG26) were investigated. The kinetics study reveals that the dye adsorptions of all γ-alumina samples fit the pseudo-2nd-order model. For CR, its k2 and the pore size of absorbent are in a linear relationship at low dye concentrations. Both of the experimental results and Langmuir isotherm calculation results suggest that the dye adsorption capacities of the γ-alumina prepared in our lab are much higher than those of other γ-alumina reported in literatures. GA-1 with the largest specific area of surface and largest size of pores exhibits a CR adsorption capacity up to 4213.6 mg/g. In addition, initial dye adsorption rates of the γ-alumina prepared in-house are much higher than that of the γ-alumina prepared with the commercially available alumina under the same conditions.

Removal of lead from aqueous solutions was studied using nanocomposite absorbent of bentonite/-alumina. The novel absorbent was characterized using XRD, FT-IR and SEM-EDX. Absorption process optimization using response surface methodology (RSM) and experimental design was performed with central composite design technique. The effects of Pb(II) initial concentration, adsorbent dosage, and composite percentage on Pb(II) removal percentage and adsorption capacity were examined. The adsorption capacity of 166.559 mg/g and removal % of 82.9887 with desirability equal to 0.763 were obtained for optimal initial concentration of 200 mg•l-1, adsorbent dosage of 0.5 mg•l-1, and composite percentage of 7.08 % determined using RSM design. The equilibrium adsorption data were investigated by Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. It was found that Freundlich isotherm model fits better compared with other models.

يهتم هذا البحث بعملية إزالة الكبريت بالهيدروجين وعامل مساعد محضر مكون من أوكسيد الكوبالت والمولبدينيومالمحمل على مادة كاما الومينا، و لثلاث أنواع من مادة النفثا وهي النفثا المختلطة والنفثا الثقيلة واخيرا النفثا Mo/γ-Al2O31334.9 ، و 709 جزء بالمليون على التوالي، والتي تم الحصول عليها ، الخفيفة والتي تحتوي على محتوى كبريتي 1642.1من مصفى ميسان.تم استعمال الكاؤولين العراقي الأبيض كمادة أولية لتحضير الكاما الومينا لتكون المادة الحاملة، تم دراسة تحويل الكاؤولينالى ميتا كاؤولين من خلال عملية الحرق بدرجات حرارية وازمان مختلفة، وتم تشخيص التراكيب البلورية لهذه التغيرات.XRD باستعمال تقنية حيود الاشعة السينيةتم تحضير الالومينا البلورية من نوع كاما ذات مساحة سطحية 129.91 م 2/غم وحجم مسام 0.9002 سم 3/غم باستخدامعملية الاستخلاص بوجود حامض الكبريتك وبنسب وزنية مختلفة من الحامض : الطين ووقت قصر مختلف ايضا، تمم، تم تجفيف وحرق الهلام الناتج بدرجة حرارة O استعمال كحول الايثانول كعامل مرسب، تم تجفيف الهلام الناتج بدرجة 70م لمدة ساعتان على التوالي. O م لمدة 10 ساعات و 900 O70تم دراسة تاثير عدد من المتغيرات المختلفة على درجة تبلور واستخلاص مادة الكاما الومينا مثل نسبة الحامض : الطين وتركيز الحامض ووقت ودرجة حرارة عملية القصر عملية تحول الكاؤولين الى ميتا كاؤولين. فيما تم تشخيص مادة كامابينما تم ،FTIR و مطياف الاشعة XRD باستعمال تقنية حيود الاشعة السينية Co-Mo الومينا المحضرة والعامل المساعدلقياس المساحة السطحية وقياس المسامية باستعمالوالمجهر AFM بالامتزاز بالنتروجين، وكذلك تم فحص احجام الدقائق باستعمال مجهر القوى الذرية BJH طريقة.XRF وقوة مقاومة السحق واخيرا نسب المعادن باستخدام الاشعة السينية المفلورة ،SEM الالكترونياستخدمت تقنية التنقيع الجاف وتقنية التشريب شبه الجاف المتعاقب في عملية تحضير العامل المساعد وتحميل المعادن الفعالة% (اوكسيد الكوبلت واوكسيد المولبيدينيوم) على مسحوق الالومينا لتحضير عامل مساعد بنسب تحميل نهائية 21.45مولبيدنيوم و 5.7 % كوبلت.اجري تقييم فعالية أداء العامل المساعد لإزالة الكبريت من مقاطع مادة النفثا المختلطة والثقيلة والخفيفة بعد عملية التشكيل،باستخدام وحدة الهدرجة الريادية الموجودة في مركز البحث والتطوير النفطي وبظروف تشغيلية مختلفة، وتم دراسة تأثيرعدد ن المتغيرات من درجة الحرارة والسرعة الفراغية والضغط والوقت والتوزيع الحجمي للفوهات، وكانت اعلى نسبة(99.72, إزالة للكبريت هي المتحققة بتخفيض السرعة الفراغية الى 2 ساعة - 1 كسياق عام حيث كانت النسب 89.71310 م لكل من النفثا المختلطة والنفثا الثقيلة والنفثا الخفيفة على التوالي، وبقيمة ضغط 34 بار o 99.20 ) وبدرجة حرارة ,. 200 سم 3/سم 3 / ونسبة هيدروجين/هيدروكربون مساوية الى 20

Carbon nanohorns (CNH), other carbon particles (OCP), fine fractions of other carbon particles (OCPf), carbon nanotubes (CNT), and γ-alumina (γ-Al2O3) were utilized as support materials for the Ni–...

Holmia supported γ-alumina nanocatalyst was prepared by impregnation of γ-alumina with aqueous solution of holmium acetate hydrate Ho(CH3COO)3.3.5 H2O. The physicochemical characteristics of the nanocatalyst calcined at 600°C were established by different techniques, using surface adsorption–desorption of N2 (SBET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy (DRS). The recorded optical reflectance of the sample showed that the new self-assembled nanocatalyst is excellent as host material for advanced optical applications. Moreover, the catalyst showed enhanced catalytic activity toward Isopropyl alcohol decomposition.

Addition of Fe to PtPd nanoparticles on γ-alumina is known to increase catalytic activity. This is shown to stem from increased Pt-Pd coordination during thermal aging which induces microstrain. X-ray absorption spectroscopy analysis reveals that the Fe dopant atoms are incorporated into the alumina surface, which fine tunes the electronic state and provides greater oxidation resistance to Pt.

Nickel on alumina support offers opportunity for gasification of biomass for hydrogen production. In a recent contribution from our research team, (González Castañeda, D. G., et al. 2019) showed that cerium or lanthanum co-impregnation at 2 wt% with nickel may have a favorable effect for biomass catalytic gasification. However, and given an observed influence of lanthanum on the formation of small Ni crystallite sizes, five Ni/γ-Al2O3 based fluidizable La promoted catalysts were studied. Nickel-alumina catalysts promotion was effected varying La in the 0.5 and 1.0 wt% range. Once impregnation precursors loaded, they were reduced at 480 °C via an activation step. Catalysts were characterized using BET, XRD, AA, TPR, TPD, H2-chemisorption, TEM-EDX and FTIR. Catalyst performance was established in a fluidized CREC Riser Simulator, using: a) glucose as surrogate biomass, b) 600 °C, c) steam/biomass (S/B) ratio of 1, d) catalyst /biomass (C/B) ratio of 3.2 and e) 20 s reaction time. Data obtained was analyzed using an ANOVA statistical data analysis package with the 5 wt% Ni and 0.5–1 wt% La and Ce on γ-Al2O3 catalysts, prepared using a pH of 1 of impregnating solution were the best yielding 0.53–0.56 hydrogen molar fractions. These catalysts also gave a 39% reduced coke, and this while compared with the coke formed on the 2% Ce – 5 wt%Ni/γ-Al2O3 (González Castañeda, D. G., et al. 2019). This promising performance was assigned to the dominant NH3-TPD medium acidity, the high catalyst specific surface (∼140 m2/g), and the good 9% metal dispersion with 9–10 nm nickel crystallites.

In the present study, the decolourization efficiency of Reactive Red 183 using the solar catalytic ozonation process has been studied using γ-alumina for the first time. To explicate the mechanism of catalytic ozonation, experiments were performed with different combinations like O3, O3/UV, O3/Al2O3, Al2O3, and O3/UV/Al2O3. Moreover, the effect of pH, hydroxyl radical scavenger, and phosphates on Reactive Red 183 removal, were also investigated. The synergic process (O3/UV/Al2O3) was found to be the best as compared with other processes at all studied pH values. The decolourization efficiencies were found to follow order as: O3/UV/Al2O3 > O3/UV > O3/Al2O3 > O3 > Al2O3. The results indicated that the adsorption of dye played a significant role in overall removal efficiency in the synergic process. The synergic process involved radical mechanism and surface hydroxyl groups of alumina were important active sites. Furthermore, solar radiation could impart a key role in the decomposition of formed hydrogen peroxide to accelerate the overall decolourization efficiency of the synergic process. In the end, it was deduced that the synergic process was highly efficient for the decolourization of dyes from wastewater.

Deactivation of a Pd/alumina catalyst has been observed during the hydrogenation of α-methylstyrene and styrene. In both feedstocks, deactivation is caused by an additive, 4-tert-butylcatechol (TBC...

A series of alumina supported Ru nanoparticles (Ru γ -Al2O3-x (x=2-10 Ru wt%) was synthesized using the ethylene glycol reduction method. XRD, TEM, EDX, H2-chemisorption, XPS and H2-TPD analytical techniques were used to understand the physiochemical nature of alumina supported Ru nanoparticles. All the well-characterized Ru#Al2O3-x (x=2-10 Ru wt%) catalysts were used for high-pressure CO2 hydrogenation to formic acid synthesis. A clear correlation was recorded between the physiochemical properties of developed catalysts and the molar quantity of formic acid. Among all the developed catalysts, Ru#Al2O3-2 catalyst with or without ionic liquid reaction medium gave a good molar quantity of formic acid. Application of ionic liquid was also expanded, and ionic liquid medium appeared as a good solvent system as compared to the amine solvent system, which not only provides better solubility of reactants and catalysts but also found useful in the easy recovery of formic acid after the completion of the reaction. The catalyst recycled seven times with easy product isolation stem to make this system very useful and fulfill the requirement of sustainable chemistry.

Mesoporous alumina (MA) has been produced from aluminium foil waste, and its performance as a sorbent in a 99Mo/99mTc generator has been evaluated. The resulting MA demonstrated excellent properties with the specific surface area of 209.8 m2 g−1 and Mo adsorption capacity of 60.2 ± 1.5 mg g−1. It was able to release 99mTc with a high yield percentage and to comply with the required standard. Our successful effort on the synthesis of aluminium foil based alumina sorbent has opened the possibility of further work on the development of waste-based alumina for separation.

Bifunctional catalysts of Cu·ZnO supported on modified γ-Al2O3 were prepared and tested in the direct hydrogenation of CO2 to methanol and dimethyl ether (DME). The γ-Al2O3 modification was carried...

International audience; The clear description of the morphology and location, with respect to the support, of metallic sub-nanometric particles remains a current experimental strenuous challenge in numerous catalytic applications. High resolution-HAADF-STEM coupled with in situ and tomographic analyses are undertaken on platinum (Pt) active phase supported on chlorinated alumina (γ-Al 2 O 3) with 0.3 and 1% w/w Pt loadings highlighting the formation of flat nanoparticles (NPs) of 0.9 nm diameter and Pt single atoms (SAs) in the reduced state. While SAs and weakly cohesive clusters are predominantly observed in the oxide state, with a coordination sphere of Pt composed of O and Cl as revealed by EXAFS, the ratio between SAs and Pt NPs in the reduced state is found to be about 2.8. This ratio is not affected by metal loading which increases both the total number of NPs and SA. Electron tomography reveals that the vast majority of NPs are located on the edges or defects (steps, kinks) of the alumina support crystallites. Density functional theory calculations further highlight the optimized structures of NPs located at the γ-Al 2 O 3 (110)(100) edge and near-edge with a stability competing with NPs located either on the (110) or on the (100) γ-Al 2 O 3 facet. A mathematical analysis of the segmented volumes shows that the average geodesic distances between NPs is linked to Pt loading: 9 nm for 1% w/w Pt, and 16 nm for 0.3% w/w Pt. Evaluation of support tortuosity descriptors using the nanoparticles positions confirms a uniform distribution on the support. A square network geometric model compatible with the geodesic distances between NPs reveals that 1 to 5 NPs can be present at the same time on each alumina crystallite depending on Pt loading.

International audience; A γ-alumina digital twin is created by means of a hierarchical pore network model. For this digital twin, nitrogen porosimetry is simulated, and the parameters of the pore network model are modified by means of a particle swarm optimization (PSO) algorithm until both branches of the digital isotherm match those of the experimental isotherm. After parameter identification, the resulting pore network model provides a digital isotherm that is in good agreement with the experimental results. The same set of parameters also allows to predict the experimental nitrogen scanning curves. The BJH pore size distribution obtained from the digital isotherm corresponds well to the experimental one. Therefore, the generated digital twin can statistically represent the topology of the industrial alumina sample. Diffusion simulations on the final structure allowed one to estimate the tortuosity factor of the structure. The predicted value differs by less than 20% from the tortuosity factor measured by PFG-NMR.

International audience; Obtaining an atomic-scale description of the chemical interactions of phosphates with an oxide support, such as γ-Al2O3, is essential to get a rational understanding of the role of phosphate additives for a great number of heterogeneous catalysts, as well as to improve the use of this element. Combining cutting-edge Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) techniques with Density Functional Theory (DFT) calculations, we provide an accurate molecular description of phosphate speciation on γ-Al2O3 surfaces for various P surface coverages after drying at 120 °C. Thanks to 31P double- and triple-quantum filtered NMR experiments as well as to 27Al–31P dipolar- and scalar-based correlation spectra, we demonstrate the presence of polyphosphates and of Al–O–P connectivities at the exposed facets of γ-Al2O3. DFT-based thermodynamics shows that phosphates (mono- or di-) are preferentially covalently bonded on the (1 1 0) γ-Al2O3 facet with high-dentation modes. These high-dentation modes are favored by entropy gain due to water desorption. We used the gauge-including projector-augmented wave (GIPAW) DFT method for 31P NMR chemical shifts calculations and propose a systematic identification of the various types of phosphates covalently or noncovalently bonded to the alumina surface. The calculations confirm the existence of polyphosphates as observed experimentally. Since the surface condensation into polyphosphates is endergonic, the presence of polyphosphates on the surface is likely to result from their direct adsorption in impregnation solution. The observed increasing concentration of polyphosphates with the coverage could be related to a less likely hydrolysis due to the reduced availability of sites to stabilize the fragmented oligomers. This understanding opens the way to a better control over the speciation of phosphate species that are known to be key in the preparation of supported catalysts over alumina.

Highly stabilized mesoporous core–shell-structured oxygen carriers (OCs) were fabricated by a repetitive coating process of alumina supports using the mesopore-forming surfactant assembly method. T...

A three-dimensional interconnected macroporous alumina monolith was successfully prepared by phase separation combined with microwave-hydrothermal process in ammonia solution. The material calcined...

Our work focuses on the study of the adsorption of methylene blue (MB) on adsorbents based on zeolite HUSY and (γAl2O3-SiO2). To optimize the process of removing MB onto Ni/Co USY, differen...

International audience; An innovative approach using solid/liquid interface characterization (zetametry measurements, ATR-IR), coupled with ex situ FTIR has been used to build a phosphate complexation model at the alumina surface via the PHREEQC software. According to the phosphorus coverage impregnated on the alumina surface, two mechanisms of adsorption have been identified: a specific surface complex adsorbed on the predominant alumina facet and a surface precipitation process. At low phosphorus coverage (P coverage

The ubiquity of amino acids in carbonaceous meteorites has suggested that amino acids are widespread in the Universe, serving as a common class of components for the emergence of life. However, parameters for modeling amino acid polymerization at mineral–water interfaces remain limited, although the interfacial conditions inevitably exist on planets with surface liquid water. Here, we present a set of extended triple-layer model parameters for aspartate (Asp) and aspartyl-aspartate (AspAsp) adsorptions on ferrihydrite, anatase, and γ-alumina determined based on the experimental adsorption data. By combining the parameters with the reported thermodynamic constants for amino acid polymerization in water, the impacts of these minerals on Asp dimerization are calculable over a wide range of environmental conditions. It was predicted, for example, that ferrihydrite strongly increases the AspAsp/Asp equilibrium ratio in neutral to acidic pH; the ratio in the adsorbed state reaches 40% even from a low Asp concentration (0.1 mM) at pH 4. This percentage is approximately 5 × 107 times higher than that attainable without mineral (8.5 × 10–6%). Our exemplified approach enables us to screen wide environmental settings for abiotic peptide synthesis from a thermodynamic perspective, thereby narrowing down the geochemical situations to be explored for life’s origin on Earth and Earth-like habitable planets.

Strontium sorption was analysed in binary mixtures of smectite and γ-alumina nanoparticles under different pH, ionic strength and Sr concentration. The aims were to verify if γ-alumina nanoparticles enhance Sr sorption in smectite and to analyse whether a component additive model satisfactorily described Sr sorption in the mixtures. In smectite, Sr sorption mainly occurs by cation exchange but surface complexation was also accounted for. In both solids, surface complexation was described with a non-electrostatic model. The addition of γ-Al2O3 nanoparticles to smectite improved Sr uptake under alkaline pH and high ionic strength, and the additive model successfully reproduced experimental data. In contrast, under acid pH and low ionic strength, no sorption improvement was observed upon adding the nanoparticles and the additive model overestimated Sr sorption. The competition of Al3+ ions, coming from γ-Al2O3 dissolution, partially explained the differences between data and model. Nevertheless, surface interactions between alumina particles and smectite layers may be shielding the charge, hindering contaminant access to exchangeable sites in smectite.

International audience; γ-alumina, a widely used industrial catalyst support, undergoes irreversible transformation into various aluminum hydroxides under hydrothermal conditions, resulting in strong modification of its intrinsic properties. Most of the strategies that have been proposed to prevent or at least minimize its transformation into oxy-hydroxides consist in covering the alumina surface by a hydrophobic carbon layer, making it less sensitive to modifications induced by water. However, such methods necessitate high carbon contents, which significantly modifies structural and chemical properties of alumina. Here, we propose a new method based on a series of adsorption/pyrolysis cycles using sorbitol molecules previously adsorbed on specific hydration sites of (110) faces of γ-alumina crystals. Those sites, which are responsible for the dissolution f γ-alumina crystals in water, are thus selectively protected by carbon clusters, the rest of the surface being totally exposed and accessible to adsorbates. Under hydrothermal conditions (10 hours in water at 200°C), the formation of hydroxides is almost totally suppressed by covering less than 25% of the surface with only 7 wt. % carbon, which is far below the amount necessary to get similar results with more conventional carbon deposition methods.  INTRODUCTION Molecules derived from existing biomass treatment processes such as fermentation and hydrolysis (sugars, alcohols, polyols, carboxylic acids, etc.) are platform molecules for bio-based products manufacture. They consist of oxygen-rich, highly functionalized and generally water soluble molecules and reactions to convert them into valuable bio-products in aque-ous media may require relatively high temperatures and sometimes high pressures. These particular conditions, which combine water and temperature, are called hydrothermal conditions (HT) and they represent a serious challenge in the field of today's heterogeneous catalysis. 1,2 Indeed, conventional catalysts used in the petroleum refining industry generally consist of an active metal phase deposited onto an inorganic support and they may not be appropriate for applications involving water as solvent under such HT conditions. For exam-γ-alumina, a widely used industrial catalyst support, undergoes irreversible transformation into various aluminum hydroxides by a dissolution/re-precipitation process when placed in a water-rich medium at moderate temperature, resulting in strong modification of its intrinsic properties. 3,4,5-8 The stability of alumina materials in water has been a matter of great interest during the last years and many strategies have been proposed to prevent or at least minimize their transformation into hydroxides. The approach generally consists in modifying the alumina surface in order to make it less sensitive to the modifications produced by water under hydrother-mal conditions. The benefits of organic additives (such as carbon 9,10), inorganic additives (such as silicon 11,12 or phosphorus 13) and metallic additives 14 on the HT stability of alumina have been reported. However, the main parameters that govern the dissolution of alumina remain poorly known, which makes difficult the development of rational methods to improve the stability of this material. Ravenelle and coworkers first noticed that alumina transformation did not occur when polyols were present in the aqueous medium during a hydrothermal process. 15,16 The effect is supposed to result from the chemisorp-tion of the organic molecules on alumina, which avoids direct contact between water molecules and the surface and significantly improves water resistance. 17 This result can be compared with the work of Pham et al. who increased alumina stability in water by covering its surface with an oxygenated carbonaceous layer resulting from sucrose pyrolysis at 400°C. 9 They showed that 10 wt. % of carbonaceous deposit on the alumina surface was enough to prevent the transformation of the solid into boehmite. In another study, the same group used methane as a carbon source to produce graphitic carbon on alumina surface by gas phase carbonization. In this case, a higher amount of carbon was required to effectively protect alumina (35 wt. %), leading to a complete modification of its original properties (textural properties and surface chemistry). 10 Despite a growing number of articles dedicated to the improvement of alumina based materials in hydrothermal conditions, rationalization of predominant parameters that control hydrothermal stability remain unclear. In a previous work, we proposed a mechanism of the first steps of alumina dissolution based on experimental and theoretical approaches. 18 This mechanism involves some specific surface sites located on basal (110) planes of alumina platelets which are particularly reactive towards liquid water. We also showed

The metal-support electronic interaction of dispersed Pt, Pd and Au layers on γ-Al2O3 is studied by density functional theory (DFT) calculations. The results indicate that electrons transfer significantly between the contacting layers of Au, Pt or Pd and the γ-Al2O3. Fukui function calculation results exhibit the electrophilicity of Al and O atoms on the Pt-supported surface is the greatest, while their nucleophilicity is the weakest. DOS calculation results demonstrate that the metal d orbital and O 2p orbital participate in the interactions, and the interaction between Pt 5d orbital and O 2p orbital is the strongest.DOI: http://dx.doi.org/10.5755/j01.ms.24.3.17855

CO2 permeation through imidazolium-based ionic liquids (ILs, [BMIM][Ac], [EMIM][Ac], [OMIM][Ac], [BMIM][BF4], and [BMIM][PF6]) confined in 1.0, 2.0, and 3.5 nm γ-alumina pores was investigated usin...

Spherical mesoporous γ-Al2O3 (γ-Al) particles, embedded with magnetite nanoparticles (MNPs), were successfully prepared using a novel approach combining sol-gel and spray pyrolysis methods. Due to the magnetism of the embedded MNPs, the MNP/γ-Al particles can be utilized as recyclable catalyst supports. To demonstrate their recovery efficacy, Pd nanoparticles were impregnated on the surface of the MNP/γ-Al particles using the wetness impregnation method, and the resulting Pd/MNP/γ-Al catalysts were used to catalyze hydrogenation reactions of 4-nitrophenol. We demonstrated that when the magnetic nanoparticles were embedded in the catalysts, the recovery efficiency of the catalysts was further improved under the magnetic field.

This work reports a facile method to recycle AlP fumigation residue into thermally stable alumina material. Through ball-milling and heating hydrolysis, the phosphorus-containing alumina was prepared. After optimizing, the alumina material retained its γ phase and a relative high surface area (173 m2/g) after ∼1000 °C aging treatment. Based on the results of 31P NMR analysis and DFT computation, It was concluded that phosphate in the form of HPO4 species adsorbed at AlIV sites of γ alumina surface. These phosphate species effectively suppressed the grain growth and phase transformation of the alumina. These findings will inspire us to do more researches on recycling value-added materials from wastes.

Steam reforming of ethylene glycol (EG) was studied using γ-alumina supported 12%Ni, 3%Pt and 3%Pt12%Ni catalysts, in a micro-channel reactor. The parallel micro-channels were etched on a stainless steel plate using micro-milling technique with high speed CNC machine. The catalysts were prepared by the incipient wetness impregnation method and were characterized by using XRD, BET, FE-SEM, H2-TPR and TGA analyses. The effects of reaction temperature and feed flow rate on the EG conversion, hydrogen yield and selectivities of the gaseous products were investigated. Experimental findings revealed that 3%Pt12%Ni/γ-alumina catalyst can provide the highest EG conversion (96.1%) with 76.6% hydrogen yield and 5.3% CO selectivity at 450 °C temperature and 4 mL h−1 feed flow rate. Furthermore, continuous EG steam reforming identified 3%Pt12%Ni/γ-alumina as the most stable catalyst. This catalyst can remain stable after being on stream for more than 20 h.

To achieve high catalytic activities and long-term stability to produce higher alcohols via CO hydrogenation, the catalytic activities were tuned by controlling the loading amounts of γ-alumina nanorods and Al 3+ ions added to modify Cu-Zn catalysts promoted with Li. The selectivity of higher alcohols and the CO conversion to higher alcohols over a Li-modified Cu 0.45 Zn 0.45 Al 0.1 catalyst supported on 10% nanorods were 1.8 and 2.7 times higher than those with a Cu-Zn catalyst without nanorods and Al 3+ ions, respectively. The introduction of the thermally and chemically stable γ-Al 2 O 3 nanorod support and of Al 3+ to the modified catalysts improves the catalytic activities by decreasing the crystalline size of CuO and increasing the total basicity. Along with the nanorods, a refractory CuAl 2 O 4 formed by the thermal reaction of CuO and Al 3+ enhances the long-term stability by increasing the resistance to sintering of the catalyst.

Dissolved gas analysis (DGA) is a useful approach to monitor the electrical faults of transformers. For extraction of dissolved gases from transformer oil in the DGA process, membrane-based separation represents an appealing technology option since the use of an oil-resistant, stable and highly gas permeable dense membrane can greatly enhance the efficiency by shortening the extraction time. However, most membranes reported in the literature have a membrane thickness in the micrometer range, making these membrane devices not sufficiently effective in practical separation of dissolved gasses from transformer oil. To reduce the thickness of membranes, Teflon AF2400 composite membranes synthesized using three different types of alumina (Al2O3) supports were investigated, including macroporous α-Al2O3 disk support, macroporous α-Al2O3 hollow fiber support, and mesoporous γ-Al2O3/α-Al2O3 hollow fiber support. The result shows that the γ-Al2O3/α-Al2O3 supports with a mesoporous top-coating γ-Al2O3 layer prepared by the sol-gel method could provide a high-quality surface for synthesizing an ultrathin and defect-free Teflon AF2400 layer. For the ultrathin Teflon AF2400/γ-Al2O3 composite hollow fiber membranes prepared by coating with a 0.5 wt% Teflon AF2400 solution, the thickness of the Teflon AF2400 layer is about 270 nm, and the permeances of H2, CH4, CO2 and C2H6 at room temperature can reach to 14,069, 2847, 11,901 and 2030 GPU, respectively, which are about 8 times higher than that of the α-Al2O3 disk or hollow fiber supported membranes. This result demonstrates the promise of the ultrathin Teflon AF2400/γ-Al2O3 composite hollow fiber membranes for extraction of dissolved gases from the transformer oil for DGA.

In this study, the adsorption properties of a Pt-decorated γ-Al 2 O 3 (110) surface (Pt-alumina) were investigated to determine the favorable sublayer for Au adsorption using first principles calculations. After full structural relaxation of various configurations, our calculated results indicated that the lowest binding energy and the distance between the Pt atom and the nearest atoms in the alumina (O atom) were −1.87 eV and 2.36 A, respectively. Finally, the adsorption energy, geometry, and electronic structure for the adsorption of an Au atom onto pure (Au-alumina) and Pt-decorated alumina (Au/Pt-alumina) were examined. The binding energy for the Au/Pt-alumina system was −3.06 eV, which is more than that for the Au-alumina system (−1.40 eV). Therefore, the results from our first principles calculations predict that the Au atom adsorptive capability on Pt-alumina is better than that of pure alumina.

Phosphorus-modified boehmite nanosheets were synthesized through equivalent-volume impregnation with Na2HPO4 solutions, which was further calcined to form γ-alumina. The XRD and HR-TEM analyses indicated that the phosphorus modification had no significant effects on the framework of the boehmite nanosheets. The FTIR spectra suggested that the phosphorus groups replaced some –OH groups and formed P–O–Al bonds with the boehmite. The modified boehmite nanosheets impregnated at the P/Al molar ratio of 1% showed a α-phase transition temperature at 1298.3 °C, much higher than that of boehmite (1189.1 °C). The IEP of the phosphorus-modified γ-alumina prepared by 2 h calcination of phosphorus-modified boehmite (P/Al = 5%) at 600 °C was as low as 7.1.

The stability and mobility of atomic cobalt and of cobalt subcarbonyl species on γ-Al2O3 surfaces have been investigated using density functional theory (DFT) with a view to elucidate possible mobile species on these surfaces, which can act as agents in the Ostwald ripening process. The two most stable alumina surfaces γ-Al2O3(100) and γ-Al2O3(110) were probed at different levels of hydration. The stability of cobalt subcarbonyl species on γ-Al2O3(100) at high partial pressure of CO (10 bar) increases with increasing number of CO ligands attached to the central cobalt atom up to Co(CO)3 but exhibits a more complex behavior on γ-Al2O3(110). The effect of the hydration level on the stability of cobalt subcarbonyls was investigated. The interpretation of the DFT results in a thermodynamic model shows that at equilibrium the main cobalt subcarbonyl species present on the alumina surface at ca. 500K in the presence of CO are Co(CO)3 and Co(CO)4, with Co(CO)3 being the dominant species on dry γ-Al2O3(100) and w...

It is shown how the chromatographic experimental technique may be applied, in combination with the use of convolution theorem, to determine the effective diffusivity of a binary pair of non-reacting gases, in spherical γ-alumina pellets (1.0 mm diameter). The experiments were performed on a packed bed (i.d. = 13.8 mm), with two different packed bed depths of 200 and 400 mm, which enabled the first and second moments for a fictitious bed length of 200 mm to be determined. The effective diffusivity of He in N2 was 9.56 × 10−7 m2 s−1 for the γ-alumina pellets, and for N2 in He was 2.31 × 10−7 m2 s−1. Using the parallel pore model, the apparent tortuosity factor was back-calculated and the value was found to be 2.2 –3.5 for the pellets studied.

International audience; We report ab initio molecular dynamics (AIMD) simulations of the (100) and (110) γ-Al2O3/water interfaces at 300 K, using two sets of supercell models for each surface and two time lengths of simulation (10 and 40 ps). We first show that the effect of liquid water on the vibrational frequencies of hydroxyl groups at the interface varies according to the type of surface. This trend is explained by two key parameters affecting the interaction of both surfaces with water: the nature of the OH groups (i.e., μ1-OH, μ1-H2O, μ2-OH, and μ3-OH) and H-bond network among surface OH groups. The hydroxylated (110) surface favors the local structuration of water at the interface and the solvation of its μ1-OH and μ1-H2O groups by water similarly as in bulk liquid water. By contrast, on the (100) surface, a stronger H-bond network among μ1-OH and μ1-H2O groups reduces the water/surface interaction. We illustrate also how the interfacial interacting sites are spatially organized on the surfaces by two-dimensional maps of O–H distances. On both surfaces, the interfacial water layer orientation is predominantly Hup–Hdown. For long AIMD simulation time, Grotthuss-like mechanisms are identified on the (110) surface.

International audience; A new, rapid, and very facile strategy for the large‐scale preparation of highly porous γ‐Al2O3 was developed. Defined γ‐alumina microparticles with a narrow mesopore‐size distribution, specific surface area of 400 m2 g–1, and a pore volume of 0.65 mL g–1 were obtained by merely employing an aqueous aluminum chloride solution.

In the current research work, trace amounts of the Ni(II), Cu(II), Ag(I) and Zn(II) ions in water, cabbage and pomegranate juice were determined via the solid-phase extraction approach based on a n...

Alumina-supported copper chloride serves as an industrial catalyst for ethylene oxychlorination, resulting from its high activity and selectivity. A better understanding of the detailed active site structure and reaction mechanism is highly desired. The present work aims to explore the dependence of the structure of active sites and the adsorption of ethylene on differently sized (CuCl2)n (n = 1–4) clusters supported by γ-Al2O3. The effect of the support facets (i.e., (110) and (100) surfaces) on the interface structures between the active component CuCl2 and the support was also investigated. The stronger CuCl2–support interaction was found on the (110) surface compared to the (100) surface, which is attributed to the stronger Lewis acidity of Al of the (110) surface. The adsorption strength of (CuCl2)n) (n = 1–4) clusters becomes weak with the increment of cluster size on the (110) surface. The cluster size has a profound influence on the interaction between ethylene and the clusters. Ethylene binds to a copper atom on the small clusters (i.e., CuCl2 and (CuCl2)2), while it extracts two chlorine atoms to form dichloroethane from the large clusters (i.e., (CuCl2)3 and (CuCl2)4), which explains the high activity of catalysts with high loadings upon exposure to ethylene. The effects of cluster size and alumina facets on the short d-band center and the Bader charge of the active sites result in the distinct formation energy of the chlorine vacancy and the interaction energy between C2H4 and the clusters. Thus, an improved catalyst could be achieved by the modification of the surface electronic structure via fine-tuning the support or adding promoters.