Aline Auroux

Bio: Aline Auroux is an academic researcher from Claude Bernard University Lyon 1. The author has contributed to research in topics: Catalysis & Adsorption. The author has an hindex of 57, co-authored 333 publications receiving 11126 citations. Previous affiliations of Aline Auroux include Centre national de la recherche scientifique & DuPont.

Microcalorimetric study of the acidity and basicity of metal oxide surfaces

Abstract: The adsorption of probe molecules such as NH{sub 3} and CO{sub 2} was studied on about 20 simple metallic oxides by use of microcalorimetry in order to determine the number and character of basic and acidic surface sites. Microcalorimetry allowed a simultaneous determination of the strength and energy distribution of the adsorption sites. The adsorption isotherms, the differential heats, the integral heats, and the energetic histograms are given for NH{sub 3} and CO{sub 2} adsorptions. Relationships between the average adsorption heats of NH{sub 3} and CO{sub 2} have been found as a function of the ionic character percentage and of the charge/radius ratio.

Infrared, Microcalorimetric, and Electron Spin Resonance Investigations of the Acidic Properties of the H-ZSM-5 Zeolite

Abstract: The infrared spectra of the H-ZSM-5 zeolite calcined at temperatures up to 1173 K, and the corresponding electron spin resonance and microcalorimetric data are discussed. Two types of hydroxyl groups are characterized by absorption bands at 3720 and 3605 cm −1 , a small shoulder being present at 3665 cm −1 . Infrared spectra were also recorded after pyridine adsorption, showing the presence of Bronsted acid sites and Lewis acid sites. After calcination at increasing temperatures, dehydroxylation of the zeolite is observed: above 675 K, the number of Bronsted acid sites decreases, while that of strong Lewis acid sites increases; however, a small dealumination occurs as shown by chemical analysis measurements and XPS data. Moreover, dehydroxylation enhances the constraint character of this zeolite, as observed by pyridine inability to titrate the total Lewis sites. Electron spin resonance studies of trapped hydrogen atoms, of adsorbed NO, and of adsorbed benzene radical cations formed on H-ZSM-5 at various calcination temperatures are discussed in terms of the number and strength of the acid sites. It is suggested that the acid sites which are present are very similar to those of H-mordenite although slightly stronger. A microcalorimetric study of ammonia adsorption confirms the very strong acidic character of the acid sites and shows their dependence in strength and heterogeneity upon calcination temperature.

Methanol conversion on acidic ZSM-5, offretite, and mordenite zeolites: A comparative study of the formation and stability of coke deposits

Abstract: The deposition of carbonaceous residues, leading to aging and modifications in the acidic properties of three zeolite samples differing by the size and shape of their interconnecting channel networks (ZSM-5, offretite, and mordenite), has been investigated during the conversion reaction of methanol to hydrocarbons. Catalytic tests, thermogravimetry, and microcalorimetry are used as complementary techniques. For zeolite ZSM-5, it is observed that carbonaceous residues are primarily formed on the outer surface of the crystallites, resulting only in a slight modification of its molecular shape-selective properties and producing a high resistance to aging. For offretite and mordenite, by contrast, the channels are large enough to accommodate carbonaceous residues, which leads to a drastic loss of catalytic activity and a very fast aging. The intimate nature of the channel network is shown to play a determining role in the coke formation and in the ease of removal of carbonaceous deposit. The role played by the shape-selective properties of the zeolites on their behavior towards coking and aging and also the effect of coking on the availability of Bronsted acidic sites have been particularly emphasized.

Acidity and basicity of metal oxide surfaces. II, Determination by catalytic decomposition of isopropanol

Abstract: In Part I of this series (Auroux, A., and Gervasini, A., J. Phys. Chem. 94, 6317 (1990)) a microcalorimetric investigation on the acid-base character of a large series of metal oxides was reported. A study concerning the acid-base catalytic properties of the same series of oxides is now reported together with a comparison with the previous results. The decomposition of isopropanol has been chosen as a test reaction to study the acid-base character of the catalytic sites of the oxides. For each oxide employed as catalyst, the rate coefficients as well as the Arrhenius parameters for both the dehydration and the dehydrogenation of isopropanol were determined. A relationship was found between the strength of the acid sites microcalorimetrically evaluated and the activation energy of the dehydration reaction, while the activation energy of the dehydrogenation reaction was independent of the strength of the catalytic sites. On the basis of the dehydration reaction, sets of oxides can be classified in scales of acid strength.

Textural Properties and Catalytic Activity of Hydrotalcites

Abstract: Double-layered hydroxides with hydrotalcite structure were synthesized with Mg/Al atomic ratios of 2.5 and 3 and with different contents of exchangeable Cl− and CO2−3anions. The basicity of these solids depends on several structural parameters and on the activation temperature. Microcalorimetric measurements, IR spectroscopy using a probe molecule, and a catalytic test reaction were carried out to characterize the basic sites. The structural evolution of the hydrotalcite upon exchange of Cl− for CO2−3 and calcination temperature shows a transformation with simultaneous removal of CO2 and water without phase segregation up to 673 K. The mixed oxide formed later could reversibly lead to the layered structure upon rehydration and carbonation. This process was studied by microcalorimetry and IR spectroscopy. The adsorption isotherm of CO2 shows an increase of the uptake and consequently of the basicity with initial CO2−3 content and calcination temperature up to 800 K. IR spectroscopy shows that the carbonation of the mixed oxide is essentially superficial and that the hydrotalcite structure may be restored upon H2O addition and 373-K treatment. Two types of Lewis acid sites related to a linear coordination of CO2 with Mg2+ and Al3+ cations are assigned. The appearance of a bicarbonate species implies that the basic sites are essentially OH groups. Moreover, a small number of strong basic sites, adsorbing CO2 with 140 kJ/mol, probably correspond to O2− centers. Hammett correlation in the condensation reaction of acetone and different substituted benzaldehydes shows analogies between hydrotalcite catalysis and the homogeneous basic reaction. The activities increase with CO2−3 content, calcination temperature, and Mg/Al ratio of the hydrotalcites. The basic strength of hydrotalcites is comparable to that of piperidine in homogeneous catalysis.

Hydroxymethylfurfural, A Versatile Platform Chemical Made from Renewable Resources

Abstract: Renewable Resources Robert-Jan van Putten,†,‡ Jan C. van der Waal,† Ed de Jong,*,† Carolus B. Rasrendra,‡,⊥ Hero J. Heeres,*,‡ and Johannes G. de Vries* †Avantium Chemicals, Zekeringstraat 29, 1014 BV Amsterdam, the Netherlands ‡Department of Chemical Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands DSM Innovative Synthesis BV, P.O. Box 18, 6160 MD Geleen, the Netherlands Department of Chemical Engineering, Institut Teknologi Bandung, Ganesha 10, Bandung 40132, Indonesia

Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process

Abstract: Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.

Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources

Abstract: Since the time of the industrial revolution, the atmospheric CO(2) concentration has risen by nearly 35 % to its current level of 383 ppm. The increased carbon dioxide concentration in the atmosphere has been suggested to be a leading contributor to global climate change. To slow the increase, reductions in anthropogenic CO(2) emissions are necessary. Large emission point sources, such as fossil-fuel-based power generation facilities, are the first targets for these reductions. A benchmark, mature technology for the separation of dilute CO(2) from gas streams is via absorption with aqueous amines. However, the use of solid adsorbents is now being widely considered as an alternative, potentially less-energy-intensive separation technology. This Review describes the CO(2) adsorption behavior of several different classes of solid carbon dioxide adsorbents, including zeolites, activated carbons, calcium oxides, hydrotalcites, organic-inorganic hybrids, and metal-organic frameworks. These adsorbents are evaluated in terms of their equilibrium CO(2) capacities as well as other important parameters such as adsorption-desorption kinetics, operating windows, stability, and regenerability. The scope of currently available CO(2) adsorbents and their critical properties that will ultimately affect their incorporation into large-scale separation processes is presented.

Ordered mesoporous materials in catalysis

Abstract: Ordered mesoporous catalysts could open the door for new catalytic processes, based partly on novel principles, owing to their hitherto unprecedented intrinsic features. For the preparation of ordered mesoporous catalysts, many strategies have been described. These strategies and the essential properties of the resulting materials are described in the first part of this review. Catalytic processes over such mesoporous materials, especially such reactions where the specific features of ordered mesoporous catalysts are exploited, are described in the second part.