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Six different Ni-based fluidizable catalysts were synthesized using both incipient impregnation and co-impregnation. Ni-based catalysts were also promoted with 2.0 wt% La or alternatively with 2 wt% Ce. The preparation procedure included catalysts treated at high temperatures and under free of oxygen conditions. Catalysts were characterized using BET, XRD, AA, PSD, TPR, TPD, H2-chemisorption. TPR and H2 chemisorption showed good metal dispersion with 10 nm- 40 nm metal crystallites. Glucose catalytic gasification runs were performed in a CREC Riser Simulator to evaluate the following catalysts: (a) 5 %Ni/γ-Al2O3, (b) 5 %Ni-2 %La/γ-Al2O3 and (c) 5 %Ni-2 %Ce/γ-Al2O3. In all cases, the preparation steps involved acid solutions with pHs of 1 and 4. In between consecutive runs, different approaches were considered: (a) A catalyst was regenerated by air, (b) A catalyst was regenerated by air followed by hydrogen pretreatment, (c) A catalyst was reused directly without any regeneration or hydrogen pretreatment. It was observed that Ni-based catalysts, which were subjected after every run, to both, air regeneration and hydrogen pretreatment, displayed the best yields in close agreement with thermodynamic equilibrium. On the other hand, Ni-based catalysts regenerated with air only, showed the worst hydrogen yields. In between these two-hydrogen yield limits, where catalysts not contacted with air nor hydrogen, with these yields being moderately below chemical equilibrium. This shows that Ni-based fluidizable catalysts can perform on stream for extended periods, requiring limited reactivation with air and H2. This makes of gasification using the catalysts of the present study, a viable process alternative that could be implemented at industrial scale.

The present work explores the adsorption potential of γ-alumina, a nanoadsorbent for abatement of Ni(II) from aqueous solutions. A response surface methodological approach was adopted to in...

Recent advances in nanotechnology make it possible to create nanomaterials based on γ-alumina with novel hierarchical structure and physicochemical properties. Hierarchical γ-alumina can be synthesized using chemical or physical methods. The nanostructures based on γ-alumina exhibit unique properties, which are utilized in the design of efficient applications. These superior properties are often due to their hierarchical organizations from the nanosize scale to the macroscopic level. The present review is devoted to the contemporary state of the studies on the methods to produce hierarchical γ-alumina. We tried to summarize herein the literature data on the methods of synthesis of hierarchical γ-AlOOH and γ-Al2O3 with controlled morphology and the application of these methods for the synthesis of hierarchical γ-AlOOH and γ-Al2O3 nanocomposites.

Porous &gamma, alumina is widely used as a catalyst carrier due to its chemical properties. These properties are strongly correlated with the physical properties of the material, such as porosity, density, shrinkage, and surface area. This study presents a technique that is less time consuming than other techniques to predict the values of the above-mentioned physical properties of porous &gamma, alumina via an artificial neural network (ANN) numerical model. The experimental data that was implemented was determined based on 30 samples that varied in terms of sintering temperature, yeast concentration, and socking time. Of the 30 experimental samples, 25 samples were used for training purposes, while the other five samples were used for the execution of the experimental procedure. The results showed that the prediction and experimental data were in good agreement, and it was concluded that the proposed model is proficient at providing high accuracy estimation data derived from any complex analytical equation.

International audience; Transitional aluminas are a very important class of materials in catalysis. The detailed understanding of their surface chemistry has attracted much attention with input from spectroscopic and theoretical studies. In this context, NMR is a key technique, which, thanks to recent methodological developments, provides insights into local structures and relative arrangements. In the present paper, we first assess two 1 H− 27 Al heteronuclear correlation NMR methods for studying the surface of γ-Al 2 O 3 dehydroxylated at 500°C. The commonly used cross-polarization (CP) transfer method is compared to the dipolar heteronuclear multiple quantum coherence (D-HMQC) experiment, revealing that the latter is significantly more robust and efficient with less signal distortion that hampers the recording of meaningful signals. Furthermore, a new MQ-D-HMQC pulse sequence is proposed to confirm the presence of sites, with a large quadrupolar coupling constant at the surface of alumina. The robustness of D-HMQC is further probed by two additional alumina-based catalysts, namely, aluminum hydrides supported on γ-Al 2 O 3 , which are active in olefin hydrogenation and polymerization, and ZrCp 2 Me 2 grafted onto γ-Al 2 O 3 , a single-site olefin polymerization catalyst. In both cases, this provides information on the configuration of surface aluminum species in the vicinity of catalytically active sites and on the residual hydroxyl networks. The present study combines advanced NMR methods and complex catalytic materials for which a critical, yet fruitful, spectroscopic approach is required for deeper understanding.

Sulfur-tolerant Pd-based composite membranes were produced by coating a thin layer of MoS2/γ-alumina on the membrane surface. This layer acted as an “armor” to prevent H2S from directly contacting the Pd membrane surface by preferentially adsorbing and decomposing the H2S.

CO2 methanation with Hydrogen to form CH4 offers a solution for off-peak renewable energy storage. γ-alumina-supported Mo and Ni-Mo catalysts were used in CO2 methanation, either in their reduced or in their carburized form. The presence of Ni improved the carburization extent of Mo-species, resulting in increased catalytic activity and selectivity for the catalytic CO2 methanation reaction. Carburization generally enhances the basicity of the materials and thus CO2 absorption on their surface. At 300°C, the conversions of CO2 for the reduced Ni-Mo/Al2O3 catalyst and Ni-Mo2C/Al2O3 catalysts were 5.3% and 13.8% respectively with a corresponding selectivity in CH4 of 10.0% and 98.1%, respectively.

The structures and energies of the B and Ga incorporated γ-alumina surface as well as the adsorption of water are investigated using dispersion corrected density functional theory. The results show that the substitution of surface Al atom by B atom is not so favored as Ga atom. The substitution reaction prefers to occur at the tricoordinated A(4) sites. However, the substitution reaction becomes less thermodynamically favored when more Al atoms are substituted by B and Ga atoms on the surface. Moreover, the substitution of bulk Al atoms is not so favored as the Al atoms by B and Ga on the surface. The γ-alumina surface is found to have stronger adsorption ability for water than the B and Ga incorporated surface. The total adsorption energy increases as water coverage increases, while the stepwise adsorption energy decreases. The studies show the coverage of water at 7.5 H2O/nm2 (five H2O molecules per unit cell) can fully cover the active sites and the further water molecule could only be physically adsorbed on the surface.

γ-Alumina was found as a new efficient heterogeneous catalyst for the synthesis of pyran’s annulated heterocyclic systems. Three-component reaction of various aromatic aldehydes, malononitrile and cyclic CH-acids in the presence of γ-alumina in H2O as a green solvent at 50 °C gave pyran derivatives in high yields. γ-Alumina has some advantages such as cheap, available and recyclable.

High-surface area γ-alumina is industrially used as a catalyst support. Catalytically active elements are doped onto the support, where they can bind to AlO4, AlO5 or AlO6 sites on the surface. Pretreating the surface with alkaline earth oxides can alter the availability of these surface sites, hence affecting the catalytic activity. The surface binding sites of strontium oxide (SrO) on γ-alumina were previously unknown. Direct 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) could not detect AlO5 sites at 9.4 T, so 1H‐27Al cross-polarisation (CP) MAS NMR was used to preferentially select the surface environment signals. We directly observed the three surface environments on dehydrated γ-alumina as a function of SrO impregnation up to 4 wt% SrO. We found that Sr2+ preferentially binds to AlO5 and AlO6 surface sites. 1H MAS NMR revealed SrO impregnation causes a reduction in the terminal (−0.3 ppm) and bridging (2.2 ppm) hydroxyl environments, as well as the promotion of a new peak in between these sites, at 0.5 ppm. By using 1H‐27Al CP/MAS NMR the relative proportions of surface sites on γ-alumina can be determined, allowing an optimal level of SrO doping that can saturate all the AlO5 sites. Importantly, this provides a method of subsequently depositing catalytically active elements on just the AlO4 or AlO6 sites, which can provide a different catalytic activity or stability compared to the AlO5 binding site.

The main goal of the present study is to prepare γ-alumina (γ-Al2O3) ultrafiltration (UF) membranes for separation of oil from a real oily wastewater. A γ-Al2O3 multilayer UF membrane on an α-alumina (α-Al2O3) substrate was successfully fabricated via the sol–gel processing method. The prepared layer from the γ-Al2O3 colloidal sol as the membrane top layer had an average pore size of 20.3 nm and thickness of 4 μm. The resulting γ-Al2O3 multilayer UF membrane did exhibit homogeneity with no cracks or pinholes. Permeate flux (PF) through the membranes was calculated. Response surface methodology (RSM) based on Box–Behnken design was used to design the experiments and analyze three operating parameters including transmembrane pressure (TMP), feed temperature (T), and cross-flow velocity (CFV). The optimum PF of 112.7 kg/m2 h was identified by RSM at feed temperature of 35°C, TMP of 5 bar and CFV of 0.735 m/s. The results showed that these membranes are efficient for treatment of petroleum refinery wa...

Unsaturated fatty acids can be converted into mono and dicarboxylic acids, which are applicably valuable materials, through oxidative cleavage reaction in the presence of a highly efficient catalyst/oxidant system. In this work, two types of advanced heterogeneous catalysts have been developed; (i) high surface area mesoporous tungsten oxide/γ-alumina mixed metal oxide, and (ii) surfactant-capped tungsten oxide nanoparticles. Various technique including N2 adsorption/desorption isotherms, XRD, SEM, EDS, TGA and catalytic test were used to monitor the physicochemical and catalytic properties of these materials. The characterization results revealed that type (i) materials exhibit high surface area and narrow particle size distribution, and the used surfactant could quantitatively enough cap the surface of type (ii) materials. The catalytic activities of these materials in the oxidative cleavage of oleic acid with H2O2 as oxidant were investigated. GC-MS was used to determine the produced amounts of desired products, azelaic and pelargonic acids. The catalytic test results showed more than 90 % conversion for type (ii) catalyst in 5 h reaction at 120 °C with acceptable production yields for azelaic and pelargonic acids. The significantly higher activity of this catalyst compared to type (i) arises from the interesting surface properties of tungsten oxides nanoparticles, which make them able to exploit the good features of homogeneous and heterogeneous catalysts.

Co(II) and Ni(II) are two common toxic heavy metals, and may simultaneously exist in contaminated water, soil, and sediment systems in Earth’s surface environment. Under this circumstance, competitive adsorption between the two metals may influence their migration, toxicity, and bioavailability. In this research, the competitive sorption of Co(II) and Ni(II) on γ-Al2O3 was studied using both macroscopic sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy. Results suggest that Ni(II) reduced the amount of Co(II) sorption in a binary-solute system at pH 6.0. This is because both Co(II) and Ni(II) form inner-sphere surface complexes during sorption on γ-Al2O3 and compete for the surface reactive sites. However, Co(II) exhibited a negligible influence on sorption amount of Ni(II) under the same conditions, which suggests Ni(II) has a stronger affinity to alumina surface. At pH 7.5, Co(II) and Ni(II) sorption density were much higher than that at pH 6.0, but there no mutual competitive effect was observed. EXAFS analysis further revealed that formation of layered double-hydrated precipitates was the dominant sorption mechanism for both Co(II) and Ni(II) at pH 7.5. Because this type of sorption does not rely on surface reactive sites, there was no competition between Co(II) and Ni(II). This finding sheds light on risk assessment and remediation of Ni/Co pollution.

In this study, γ-Al2O3 was synthesized using a hydrothermal method and its morphology and chemical composition was characterized by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and X-ray diffractometer (XRD). The TEM images, EDX and XRD spectrum highlight good crystallization and multi-slice feathery microstructure, involving relatively pure crystal sintering. The Pb(II) concentration analysed by inductively coupled plasma mass spectrometry (ICP-MS) after centrifuging is linked to the γ-Al2O3 adsorption, and a removal method for Pb(II) from water passing through kitchen faucets is proposed. The Pb(II) value below 0.06 mg g−1 relative to the γ-Al2O3 value reveals 94% adsorption. Further assessment of the alumina separation effect for faucets shows Pb(II) precipitation from the downstream of the valve spool is below 0.16 μg L−1. About 0.12 g adsorbent is mixed with 1.0 L tap water to produce a suspension for effective soaking. The proposed method produced satisfactory results, providing a theoretical basis for authorities to exploit on heavy metal removal from kitchen faucets.

Dimethyl ether (DME) is of great interest due to its wide application. It is currently being demonstrated for use as an alternative diesel fuel or substituting LPG for household. DME production via methanol dehydration reaction is affected by textural properties and catalyst surface acidity. The experimental study of textural properties in addition to surface acidity of both γ–Al2O3 prepared in this study and modified γ–Al2O3 over zeolite A and X mixing were conducted. The catalysts were characterized by N2 adsorption-desorption, X-Ray diffraction (XRD), and temperature programmed desorption of ammonia (NH3-TPD). Referring to N2 adsorption/desorption isotherm using the Brunauer-Emmerr-Teller (BET) equation, the catalysts were observed possessing high specific surface area (170–279 m2 g-1) and pore diameters of 5.6 – 8.8 nm (mesoporous). The XRD patterns of all catalysts still reveals clear peaks of γ–Al2O3 components. The strength of the acid sites of alumina modified with zeolite A is categorized as medium acid sites, whereas modified by zeolite X varies.

Nano alumina-supported zinc oxide-copper oxide (ZnO-CuO/γ-Al2O3) solid catalyst that is coded by NZCA, has been successfully synthesized and used to produce biodiesel from Kesambi (Schleichera olesosa l.) oil (KO). The catalyst was synthesized using a combination of precipitation, impregnation, and gel process. Before being used for transesterification of kesambi oil, NZCA catalyst was characterized using the X-ray diffraction (X-RD), Brunauer-Emmett Teller (BET), and Scanning Electron Microscopy (SEM) methods. The transesterification process was conducted in a glass batch type reactor with refluxed methanol. The effect of loading ZnO (wt.% to alumina), reaction temperature, and amount of catalyst (wt.% to kesambi oil) on the yield of biodiesel were investigated, respectively. The results showed that the catalyst of NZCA was potentially used for transesterification of kesambi oil. The highest biodiesel yield of 89.21% was achieved.

This study investigated dry reforming of methane with combined catalysts supported on γ-Al2O3 support doped with 3.0 wt. % TiO2. The physicochemical properties of all the catalysts were determined by inductively-coupled plasma/mass spectrometry metal analysis, nitrogen physisorption, X-ray diffraction, temperature programmed reduction/desorption, thermogravimetric analysis, and scanning electron microscopy. The addition of CeO2 and MgO to Ni strengthened the interaction between the Ni and the support. The catalytic activity results indicated that the CeO2 and MgO addition to Ni did not do much in retarding carbon deposition, but they improved the activity of the catalysts. Among the tested catalysts, it was found that the catalyst with the composition of 5.0 wt % NiO-10.0 wt % CeO2/3.0 wt %TiO2-γ-Al2O3 resulted in the highest CH4 and CO2 conversion with H2/CO mole ratio close to unity. The optimum reaction conditions in terms of reactant conversion and H2/CO mole ratio were achieved by varying space velocity and CO2/CH4 mole ratio.

In this investigation magnetic γ-Al2O3 ceramic nanocomposite particles bearing epoxide functionality are prepared following a multistep process. The ultimate nanocomposite particles are named as γ-Al2O3/Fe3O4/SiO2/poly(glycidyl methacrylate (PGMA). The surface property is evaluated by carrying out the adsorption study of Remazol navy (RN), a model reactive azo dye, on both γ-Al2O3/Fe3O4/SiO2 and γ-Al2O3/Fe3O4/SiO2/PGMA nanocomposite particles. The adsorption is carried out at the point of zero charge (PZC) to neutralize the effect of particle surface charge. The adsorption rate is very fast, reached equilibrium (qe) value within five min. Due to mesoporous structure of silica layer γ-Al2O3/Fe3O4/SiO2 nanocomposite particles possessed relatively higher specific surface area and magnitude of adsorption is dependent on the total specific surface area. The introduction of epoxide functionality favored high adsorption capacity in mass per unit surface area. The adsorption process strictly followed Langmuir model. Thermodynamic equilibrium parameters implied that irrespective of surface functionality the adsorption process is spontaneous and exothermic. Pseudo-second-order rate kinetic model is more appropriate to explain the adsorption kinetics.

The reactions of Ga(i-Bu)3 (i-Bu = CH2CH(CH3)2) with the dehydrated and partially dehydroxylated surfaces of alumina (Al2O3–500) and silica (SiO2–700) were studied by IR, high field solid-state NMR and EXAFS spectroscopies, as well as elemental analysis. Grafting onto Al2O3–500 occurs selectively by protonolysis at individual surface hydroxyl groups, resulting in the formation of mononuclear [(≡AlO)Ga(i-Bu)2L] (L = surface oxygen) sites as the major surface organometallic entities. Conversely, grafting on silica affords dinuclear species [(≡SiO)2Ga2(i-Bu)3] by a combination of protonolysis and isobutyl group transfer to Si. Further evidence for the difference in nuclearity was obtained by analysis of the WT-EXAFS. The mononuclear alumina-supported Ga sites show much higher activity in propane dehydrogenation than their dinuclear silica-supported counterparts. The propane dehydrogenation reaction may require the presence of Al–O–Ga bonds to promote heterolytic C–H bond activation. Comparisons with benchmar...

In this paper, a mesoporous γ-alumina membrane coated on a macroporous α-alumina support via sol-gel method has been reported. A crack-free γ-alumina membrane was obtained by adding PVA to the alumina solution and optimum parameters of roughness, temperature and porosity were achieved. The support was dip-coated in different solutions using two new different solvents with different particle size distributions. Using these two solvents led to the uniform distribution of pore size in the final membrane. The alumina sols showed particle size distributions in the range of 20 to 55 nm which was measured by a DLS Zeta Sizer. X-ray diffraction technique, atomic force microscopy and scanning electron microscopy were used to characterize the membrane layer. XRD and DTA data for the γ-alumina membrane showed its thermal stability up to around 600 °C. The thickness of the mesoporous γ-alumina membrane was about 4 μm with 16 nm of surface roughness and 5 nm pore size. The resultant crack-free mesoporous membrane shows that the membrane preparation procedure was optimum. In this work, it has been investigated the performance of γ-alumina membranes for single gas permeation and separation of binary gas mixtures.

The present study reports a simple and inexpensive method for improving the textural properties and stability of γ-alumina by adding crushed sugar cane bagasse to the synthesis gel (highly crystalline bayerite was used as an aluminum source). The influence of bagasse was evaluated by varying the biomass/bayerite ratio from 0.05 to 1 wt%. The presence of bagasse increased both surface area and pore volume up to 2.5-fold and 1.5-fold respectively. In addition, mesopores with a mean diameter of 5 nm were observed, which were further increased to 6 nm using hydrolyzed biomass prior to the synthesis. HRTEM measurements highlighted that the presence of biomass raised the formation of pores by enclosure of (111) and (002) lattice planes.

The γ-alumina and titania nanocrystallites were coated by sol–gel method on alumina supports respectively, as sub-layer and top-layer to prepare nanomembranes. The analysis represented a meso-porous structure for the coating layers of nanomembrane with the average pore size of 5.8 nm. The performance of the nanomembranes was investigated for permeability of demineralized water as well as rejection of ions and microorganisms using a model wastewater. Results show that in the range of 1–10 bar applied pressure, the permeability was reduced. At higher than 10 bars, with the increase of pressure, the permeability almost stayed constant due to the increase of flux. The multilayer nanomembranes showed different rejections for ions up to 25% but completely separation of the microorganisms.

We developed the polyol synthesis of γ-alumina particles that allows for control of their particle size from the nanometer level to the micrometer level. The developed polyol synthesis utilized a reflux reaction of ethylene glycol solution with aluminum nitrate hexahydrate and poly(vinylpyrrolidone) (PVP). Two important process parameters – the molecular weight of PVP and refluxing temperature – were investigated to control the size of the alumina particles. Further, two growth models for amorphous alumina particles in polyol synthesis were suggested. γ-Alumina with secondary particle size ranging from 142 nm to 1.0 μm with a specific surface area ranging from 81 to 32 m2/g was obtained. The α-alumina prepared by high-temperature annealing of over 1200 °C had secondary particle sizes ranging from 246 to 330 nm, but with specific surface areas of only 5.4–11 m2/g. Therefore, it is proved that the polyol synthesis is able to control secondary particle size of γ-alumina upon maintaining a large specific surface area.

Eight different silanes with chloro or methoxy active ligands have been examined to modify the surface of a standard γ-alumina support to investigate the effect of surface acidity and hydrophobicity in Fischer-Tropsch synthesis (FTS) at common operating conditions (210 °C; 20 bar; H2/CO = 2.1). Silanes were impregnated prior to cobalt (Pre) or after cobalt impregnation and calcination (Post). Samples were characterized by standard techniques (FTIR, XRD, TPD, TPR, TGA, BET). In the Post series, cobalt crystallite size is maintained, while it is reduced when cobalt impregnation is performed on a partly hydrophobic surface. Both series of catalysts have FTS performances that deviate significantly from a reference catalyst and, in combination with characterization data, the silanes have modified all the 15 examined catalysts. The Pre series offer options for improved selectivity to higher hydrocarbons in FTS. The effects of silylation on FT performance mechanisms are discussed in terms of gas diffusion limitations, strain in cobalt particles and partial blocking of CO activation sites. © 2017. This is the authors’ accepted and refereed manuscript to the article. LOCKED until 3.5.2019 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Boehmite (γ-AlOOH) nanosheets with a curtain-like crumpled morphology have been synthesized via a template-free hydrothermal process in two stages. The formation of the crumpled 2D nanostructures was studied at 70–95 °C in stage-1 and 150 °C in stage-2 hydrothermal processes, and a growth mechanism was proposed. The introduction of corrugations and wrinkles prevents the nanosheets from severe interface stacking. Based on the XRD, TEM, and N2 sorption analysis results, the thickness of the nanosheets is ca. 2.5–5 nm, which is composed of 2–4 lattice unit layers only. The crumpled boehmite nanosheets exhibit a high BET surface area of ca. 330 m2 g−1, and can be simply transformed into γ-Al2O3 with preservation of the morphology and ~90% of the surface area after calcination.

The structure of γ-Al2O3 is still under debate. Here we report a H spinel structure evolved from pseudo-boehmite. A unit cell with two octahedral cationic vacancies and one bulk H was preferential in terms of calculated Gibbs energy, which was well consistent with experimental data. Bulk H was found to migrate out with elevated temperatures. Through calculating the migration barriers of every step, we observed that the "hopping" step was rate-determining. The hopping rates were further estimated by assuming a Boltzmann distribution of energies, and as a result they increased by 2 to 3 orders of magnitude from 500 °C to 800 °C. This investigation will encourage us to study more uncertainties in material structures.

There are several technologies for the treatment of oily wastewater generated by the oil industry, not only to separate the emulsified oil in water, but also to reduce its concentration in the aqueous effluent. Among the processes of separation, the separation using membranes should be highlighted when they become an effective material and it also resistant to high temperatures, have good corrosion resistance, easy to clean, and have long life operation, among others. This work aims to synthesize the material (ZSM-5, γ-alumina membrane, and zeolite membrane ZSM-5/γ-alumina) and to evaluate the membranes in the oil/water separation in a continuous flow system. From the XRD results of the individual materials, it can be observed the formation of all the characteristic peaks for each material. The EDX analysis of zeolite ZSM-5 showed the formation of this material with a Si/Al = 19. From the SEM image of these materials, it can be seen that the surface of the γ-alumina is completely covered with ZSM-...

Ni/HZSM-5 catalysts with γ-alumina were prepared by the sol–gel method. At first, reaction performances were investigated over the HZSM-5 catalysts with and without γ-alumina. Then, reaction evaluations were conducted over the Ni/HZSM (different loading amounts of nickel species were investigated) catalysts with and without γ-alumina. The addition of nickel species and γ-alumina increased the total acidity of the catalysts. Furthermore, the introduction of γ-alumina increased the amount of mesopores in the catalysts. Nickel species were much more stable with the presence of γ-alumina. Both nickel species and γ-alumina contributed the aromatization of methanol.

Dimethyl ether (DME) synthesis reaction rate was studied over a commercial sample of γ-Alumina to investigate the accuracy of the most applicable rate models. Due to the deviation of the former proposed models especially at temperatures below 593 K, a new simple empirical rate model was proposed. Besides, previous proposed correlations for methanol dehydration equilibrium constant were examined experimentally and a new equation was developed. Subsequently, one dimensional unsteady state heterogeneous model was applied to simulate adiabatic and non-adiabatic fixed-bed reactors. Temperature profile and methanol conversion along the reactors were predicted while varying feed rate and feed temperature.

The simultaneous adsorption of SO2, NO, and CO2 on K2CO3-modified γ-alumina under different operating conditions was studied in a fixed-bed reactor. The experimental results showed that the influence of a temperature increase on the simultaneous adsorption of the three gases was complex and different from the effects seen when both chemical adsorption and competitive adsorption existed. An increase in O2 concentration and small amounts of water could enhance the adsorption of SO2 and NO while the adsorption of CO2 was not influenced. The breakthrough curves of the simultaneous adsorption experiments suggested that the investigated adsorbent may be a good candidate for the simultaneous adsorption of SO2, NO, and part of the CO2 while the adsorption capacity for CO2 still needs to be enhanced.

The effect of the transformation of phase in nanopowders of transition alumina has showed to be detrimental for the final characteristics of the consolidated materials. It was found that the complete transformation from gamma (γ-Al2O3) to alpha (α-Al2O3) alumina generated larger grain sizes and lower relative densities. This work studies the effect of slip casting preformed on the transformation phase of alumina during microwave sintering of α-alumina nanopowders. The sintering of the samples was carried out in a typical unimodal microwave furnace with a 2.5 GHz frequency. Sintering was carried out under air atmosphere at temperatures vary between 1100 and 1500 °C with heating rate of 100 and 200 °C/min and with a sintering plateau of 5 minutes. Sample characterization was performed by XRD, SEM, and TEM. The phase quantification was calculated using the Rietveld software from the XRD patterns. To have a good heating control in the microwave system it is possible by using slip casting to preform compact. It was observed that the heating rate has a strong effect on the phase transformations. Secondary phases like θ, θ’(x, y) appeared in samples sintered with a heating rate of 200 °C/min no matter the sintering temperature. Meanwhile the complete alumina transformation was found when sample were heating at 100 °C/min.

We report new results on the aldol reactions between aldehydes of three different types (aromatic, aliphatic and cycloaliphatic) and acetone/cycloalkanones as reaction partners, driven by organic–inorganic hybrid catalyst Pro/γ-Al2O3. In contrast to the homogeneous liquid-phase reaction, over Pro/γ-Al2O3 reversal of the enantioselection in up to 20–40 % ee depending on the structure of the aldehyde was observed in reactions of acetone. Reversal of the ee in the presence of γ-Al2O3 cannot be generalized, as it has only been observed for acetone among the ketones studied by us. It was proven using methods of a great variety such as ultrasonic irradiation, reuse measurements on used catalyst and the filtrate of the first reaction, measurements on the l-Pro-l-Pro(OH) dipeptide, studies using mixtures of l-Pro and d-Pro that the organic–inorganic hybrid catalyst Pro/γ-Al2O3 formed in situ is responsible for reversal of the ee. In the reactions of cycloalkanones there is presumably competition between the liquid-phase and the surface reaction over Pro/γ-Al2O3 with preference for the former. Based on these results a surface reaction pathway was proposed. Although, the ees obtained under heterogeneous catalytic conditions are low, further studies may lead to application of this unusual phenomenon for obtaining chiral heterogeneous catalysts suitable for the preparation of the desired enantiomer of a chiral compound using the same chiral source.

Homogeneous Ru catalysts, [RuCl2(p-cymene)]2 (Ru-p-cymene) and (η5-C5Ph4O)2HRu2H(CO)4 (Shvo’s catalyst), were immobilized on phosphotungstic acid (PTA)-modified γ-alumina (Augustine’s method) and applied to the dynamic kinetic resolution (DKR) of 1-phenylethanol (1-PE) with an enzyme (Novozym 435®). The immobilized catalysts showed rates similar to those of homogeneous catalysts in conventional reaction conditions and the immobilized Shvo’s catalyst showed no leaching during reaction. The yield to the ester of the immobilized catalysts was found to be dependent on the solvent and alkali additive. When the DKR of 1-PE was performed in n-octane, the reaction proceeded well without an alkali additive over Ru-p-cymene, which is a new observation. Furthermore, the reaction yields with the immobilized catalysts were greater than those with the corresponding homogeneous catalysts at that condition. The main factors influencing the process carried out in the DKR mode over the Ru complexes are the solvent, the support, the alkali additive and the catalyst type. The effects of the reaction temperature, type of acyl donor and catalyst/enzyme amount were further investigated in order to find the optimum process condition of the DKR using immobilized catalysts without alkali additive in n-octane.

Silver/alumina catalysts are known to be highly active for hydrogen-assisted selective catalytic reduction (SCR) of nitrogen oxides. A comparison of silver/alumina and pure alumina catalysts shows that hydrogen conversion occurs on the silver. Subsequently formed NO2 is crucial for NH3-SCR and in addition products from the hydrogen conversion influence nitrates on the alumina by spill-over.

We have successfully prepared O/W emulsions stabilized with γ-Al2O3 nanostructures for chemical enhanced oil recovery (C-EOR). In this paper, γ-Al2O3 nanostructures with different morphology and surface area were prepared by a very simple and economical wet chemical method. The as-preparedγ-Al2O3 nanostructures were used for emulsion preparation with other ingredients such as water, suitable surfactant, n-decane and 2-propanol. It is observed that cationic surfactants (CTAB) are superior to the anionic (SDBS) and non-ionic (TX-100) surfactants and have suitable stability in different temperatures. Therefore, the as-prepared O/W emulsion can be used in chemical enhanced oil recovery (C-EOR) especially for the carbonate reservoirs.

The γ-alumina catalyzed synthesis of a new series of β-functionalized 5-methyl-1 H -pyrazol-3-ol derivatives by the multi-component reaction of an aldehyde, ethylcyano acetate, and in situ generated 3-methyl-1 H -pyrazol-5(4 H )-one obtained from hydrazine monohyrade and ethyl acetoacetate in aqueous medium is described. The present reaction forms an important variant of the Yonemitsu-type multi-component reaction. The salient features of this present environmentally benign method are: recyclability of the catalysts, mild reaction condition, excellent yields of product, and the use of aqueous medium in the reaction.

Superhydrophobic flaky γ-alumina coating was prepared on AISI 316 2B stainless steel and was field-tested near size roll at a paper machine in a paper mill for 6 weeks consisting of two running periods of machine to check the easy-to-clean property and durability, as compared to an uncoated reference stainless steel. In the end of the field test, both the superhydrophobic and the reference stainless steel were fully covered with substances from the testing environment. Major part of the collected substances on the superhydrophobic stainless steel can be washed away by pressurized water; however, the collected substances remained on the reference stainless steel after washing. The field-tested samples were characterized visually and by stereomicroscopy, field emission scanning electron microscopy, laser profilometry and contact angle tester. The field test revealed the easy-to-clean property of the superhydrophobic surface and the superhydrophobic coating survived rather well after the first running period of 16 days in the field test. The resistance and durability of the superhydrophobic surface still needs to be further improved for longer term application in paper industry. Nanoindentation was used to further study the mechanical properties of the γ-alumina coating. It was found that the γ-alumina coating became much softer after transforming from flat to flaky form. In addition, the flaky γ-alumina coating demonstrated a phenomenon of time-dependent plasticity and some flexibility.

In this study, the nature of the hydroxyl groups present on γ-alumina, γ-Al2O3, pretreated at various temperatures has been reinvestigated by 1H NMR spectroscopy. The peaks are assigned by comparison between experimental and simulated spectra, in agreement with previous IR studies. The lowest chemical shifts δ correspond to OH groups strongly bound to the most acidic Al atoms (AlIV and AlV). High chemical shifts δ are assigned to OH groups making hydrogen bonds. A large range of values is found depending on the strength of these bonds. The structure of the surface complexes obtained by grafting Hf(CH2tBu)4, 1, on γ-Al2O3 at various pretreatment temperatures T (350, 500, 700 °C), referred to as 1-γ-Al2O3-(T), and of their thermolysis products has been determined, by a combined experimental (mass balance, in situ IR,) and theoretical (DFT calculations) study. These results unambiguously prove the presence of two kinds of neopentyl–metal bonds, Hf–CH2tBu and Al–CH2tBu for 1-γ-Al2O3-(500) and 1-γ-Al2O3-(700),...

CuO/γ-Al2O3 catalysts were prepared by impregnation with different CuO loadings. The dispersion of CuO supported on γ-Al2O3 support was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and temperature programmed reduction (TPR). The dispersion threshold of CuO in γ-Al2O3 determined by X-ray quantitative analysis was 0.275 g/g, i.e., 0.275CuAl. Highly dispersed CuO or crystalline CuO would appear on the γ-Al2O3 support when CuO loading was below or more than its dispersion threshold. TPR experiments show that reduction peak temperature ranges of 0.1CuAl and pure CuO are 420–690 °C and 290–380 °C, respectively. 0.1CuAl is not easily reduced due to interaction between CuO and γ-Al2O3. 0.5CuAl shows a two-step reduction range during 210–300 °C and 410–730 °C, which confirms the existence of highly dispersed CuO and crystalline CuO. The sulfation experiments show the optimal CuO loading amount is far below its dispersion threshold, and copper oxide supported on γ-Al2O3 is in the form of submonolayer.

The interaction mechanism between SO(2) and NO on γ-Al(2)O(3) was explored by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and outlet response of the concentrations of NO, NO(2) and SO(2) under exposure of Al(2)O(3) to SO(2) and/or NO in the absence or presence of oxygen at 150°C. The results showed that SO(2) promoted NO oxidation and NO transformed weakly adsorbed SO(2) into strongly adsorbed species on γ-Al(2)O(3), and the presence of O(2) facilitated this transformation. An interaction mechanism between SO(2) and NO on γ-Al(2)O(3) was thus postulated. The exposure of Al(2)O(3) to SO(2) and NO in the presence of O(2) resulted in the formation of at least two types of intermediates. One type was [SO(3)NO], which decomposed to form NO(2), and the other type was [SO(3)NO(2)], which decomposed to form SO(3). The decomposition of both intermediates probably formed O vacancies replaceable by gaseous O(2).

Adsorption of Cr(VI) on γ-alumina was investigated as a function of ionic strength (0.001, 0.01 and 0.1 M NaNO3), pH (4–10), Cr(VI) concentration (10−4 or 10−5 M with 5 g/L solid) and pCO2 (0, atmospheric, 2.5%). Cr(VI) sorption is significant at low pH and decreases with increasing pH, with 50% of the Cr(VI) adsorbed between pH ∼6.5 and 8. Adsorption varies little with ionic strength or pCO2 under most of the studied conditions. However, at low pH under high ionic strength and especially at high ionic strength and high pCO2, Cr(VI) sorption on γ-alumina is suppressed. The adsorption edge data were used to parameterize constant capacitance (CCM), diffuse double layer (DLM) and triple layer (TLM) surface complexation models. None of the models entirely captures the full range of observed adsorption dependence on ionic strength and sorbate/sorbent ratio. The best fits to the full dataset are produced by the CCM, mostly because it has ionic-strength dependent stability constants. The more sophisticated TLM, which requires the most fitting parameters, does not produce better fits than the simpler CCM or DLM approaches for the conditions tested in this study.