The potential of saponite clays, hydrous magnesium silicates with low content of aluminium, is investigated in the selective isopropanol catalytic dehydration to propylene. Their performances are compared with the activity of montmorillonite clays, low-alumina zeolite and amorphous silica-aluminas. All solids were characterized by XRD, N-2 sorption isotherms, TGA-IR, NH3 adsorption FTIR, NH3/SO2 adsorption microcalorimetry, and solid-state H-1 and Al-2(7) NMR. The physico-chemical analyses show that the samples are predominantly mesoporous, except zeolite, with BET surface areas ranging from 130 to 430 m(2)/g. All catalysts display acidic character and are thermally stable below 300 degrees C. Their catalytic performances were evaluated by using a pulse catalytic reactor set inside a calorimeter (DSC-GC). This technique offers a convenient way to screen industrially relevant temperature regimes that balance activity, selectivity and process economy of different type of solids. Catalytic testing revealed that below 150 degrees C, clays outperformed amorphous silica-aluminas, whereas the zeolite, although giving high conversion, is not suitable for the application due to a low selectivity to propylene (10%). An optimized activation temperature is the key parameter allowing clays to preserve structural stability, moderate surface area with favorable pore structure and to maintain a suitable number of acid sites.

This study highlights the potential of natural sepiolites, abundant fibrous hydrated magnesium silicates, as possible eco-friendly acid catalysts. By investigating materials with different aluminum contents, their thermal behavior up to 600 degrees C and leaching by water or acid treatments, the role of Al3+ substituting Si4+ or Mg2+ in the tunning of acid properties of sepiolites is discussed. The amount, strength and strength distribution of the acid sites were determined by NH3 adsorption microcalorimetry. Besides, Fourier Transform InfraRed and Nuclear Magnetic Resonance spectroscopy techniques were used to get insight into the nature of the acid sites when low amount of Al is incorporated in the sepiolite structure. The density of acid sites, key parameter for high catalytic activity, increased with the Al content. Bridging silanol (Si-O[H+]-Al) Br & Oslash;nsted acid sites were evidenced in thermally treated samples. Isopropanol conversion was studied between 100 and 300 degrees C in a pulse system for its practical importance for green propylene production and as test reaction to probe the acid properties of solids. The edge AlVI species able to reversibly reduce their coordination number under the reaction conditions and medium strengths sites (80 to 150 kJ/mol as determined by NH3 adsorption microcalorimetry) are at the origin of active acid sites.

Three bulk oxides were studied to elucidate the dependence of the surface mechanism involved in the dehydration of isopropanol to propylene. Niobium oxide (acid), magnesium oxide (basic) and alumina (amphoteric) were selected for this study due to their distinct acid-base properties. The complementarity of infrared and microcalorimetry methods was used to accurately correlate surface properties with catalytic activity. The latter were evidenced using a reactor inside a microcalorimeter linked to gas chromatography and subsequent kinetic computations. Acid sites are essential for isopropanol to coordinatively adsorb and initiate a surface reaction under catalytic conditions. A solely basic surface exhibits isopropanol physical adsorption under continuous inert flow, with no surface reaction. The presence of both acidic and basic sites allows for easier dissociation of the alcohol. The synergetic effect of acid-base pairs on isopropanol adsorption and conversion is confirmed by the study of amorphous silica-alumina. Surface hydroxyls are also involved in the adsorption. The effective activation energy determined by advanced kinetic computations suggests a first order mechanism on acidic surfaces. On the amphoteric solid, the results suggest the presence of both second order and first-order elimination mechanism. The water produced during the reaction shown to alter the surface properties and reaction pathway. These results highlight the important role of acid-base site strength, nature and distribution and their synergetic effect on reaction mechanisms.

Commercial alumina and silica–alumina catalysts were investigated for propylene (PEN) production via an isopropanol (IPA) dehydration reaction between 200 and 300 °C at an atmospheric pressure and IPA partial pressure of 5136 Pa. The reaction conditions were chosen to fit with the further conversion of PEN into value-added compounds with minimal capital cost, and the conceptual process design was discussed. The textural properties, structure and chemical composition of as-received and hydrothermally treated catalysts were characterised by the adsorption–desorption of N2, X-ray fluorescence, X-ray diffraction and Nuclear Magnetic Resonance spectroscopy. The adsorption microcalorimetry of NH3 and SO2 was used to determine the amount, strength and strength distribution of acid–base sites, while the nature of the acid sites was investigated by Fourier Transform Infraed spectroscopy. Surface area, pore-size distribution and pore volume were not determining factors for the catalytic performances of studied solids in the conditions used here. The best-performing catalyst combined stable textural properties and a high number of high-strength acid sites (Qdiff > 150 kJ/mol NH3) under hydrothermal conditions. The importance of determining the number and strength of acid sites of water-aged catalysts, when considering reactions where water is present as reactive or product, is underlined.

In this study, a pulse catalytic test set inside a microcalorimeter has been developed for studying the different steps of the heterogeneous catalytic mechanism of isopropanol dehydration to propylene. Adsorption of reactants and desorption of products are studied from an energetic point of view at temperatures in the range of 125 to 250 degrees C, and over commercial alumina catalyst. Results are discussed in terms of heats of adsorption, reaction and desorption of the gaseous reagent and products on the active sites of the catalyst surface. Isopropanol conversion and kinetic analysis of calorimetric signals are investigated. Heat flow signals were analyzed both at low temperature (125 degrees C) when only adsorption/desorption occurs, and at high temperature (>175 degrees C) with occurrence of adsorption, reaction and desorption. Strong dissociative adsorption was refuted from the different process steps. Meaningful kinetic parameters gave insight into the limiting steps and the reaction mechanism by analyzing the exothermic and endothermic contribution separately. Two models were used to fit the calorimetric signals, and two possible surface mechanisms are discussed: the second order elimination (E2) and the first order elimination through a carbanion path (E1cb).

All-silica, boron and boron-aluminium substituted MFI-type zeolites were prepared. Different amounts of boron were added to the starting reaction mixtures to investigate their influence on the properties of the obtained zeolites. A comprehensive characterization of the materials was conducted using various techniques: X-ray Diffraction (XRD), nitrogen physisorption, Scanning Electron Microscopy (SEM), infrared (IR), Nuclear Magnetic Resonance (NMR) spectroscopy, thermogravimetric analysis (TGA) as well as microcalorimetry. The MFI topology and crystallinity is preserved regardless the amount of heteroatoms that occupied different local environments, while the morphology of the crystals, their thermal stability, and their acidity differ considerably. For instance, boron assuming both tetrahedral and trigonal coordination, affect the interactions of the framework with both the organic structure directing agents (OSDA) and ammonia species giving rise to detectable differences in acidity.

In recent years, machine learning (ML) techniques have demonstrated a strong ability to solve highly complex and non-linear problems by analyzing large datasets and learning their intrinsic patterns and relationships. Particularly in chemical engineering and materials science, ML can be used to discover microstructural composition, optimize chemical processes, and create novel synthetic pathways. Electrochemical processes offer the advantages of precise process control, environmental friendliness, high energy conversion efficiency and low cost. This review article provides the first systematic summary of ML in the application of electrochemical oxidation, including pollutant removal, battery remediation, substance synthesis and material characterization prediction. Hot trends at the intersection of ML and electrochemical oxidation were analyzed through bibliometrics. Common ML models were outlined. The role of ML in improving removal efficiency, optimizing experimental conditions, aiding battery diagnosis and predictive maintenance, and revealing material characterization was highlighted. In addition, current issues and future perspectives were presented in relation to the strengths and weaknesses of ML algorithms applied to electrochemical oxidation. In order to further support the sustainable growth of electrochemistry from basic research to useful applications, this review attempts to make it easier to integrate ML into electrochemical oxidation.

Steam reforming of methane at 650 degrees C under water-deficient conditions was investigated over Ir/Ce0.9Gd0.1O2-x nanocatalysts (noted Ir/CGO hereafter) with very low Ir loading (0.1 wt%). Our previous works showed the promising performances of Ir/CGO for gradual internal reforming in solid-oxide fuel cells (SOFCs). However, it was observed that the high-temperature (900 degrees C) conditions of the catalyst pretreatment, as required by SOFC devices, lead to low initial catalytic activity when using a purely neutral gas feed, although a slow activation occurs on stream. Herein, we demonstrate that a pretreatment involving trace amount of O2 (10 ppm) maximizes the initial activity. In contrast, overoxidation appears detrimental. Systematic investigations by aberrationcorrected transmission electron microscopies, X-ray photoelectron spectroscopy and synchrotron X-ray absorption spectroscopy at the Ir L3 edge, including operando XANES, allow us to explain the enhancement by identifying the key restructuring phenomena and the active species. Whereas single Ir cations and metallic Ir nanoparticles are spectator species, oxidic Ir clusters exhibit high activity. Subtle changes in O2 concentration during the pretreatment dictate the initial nature of the Ir species as well as their evolution on stream through redox and clustering/redispersion phenomena. These results then suggest optimal conditions for the reforming process.

The hydrogenolysis of tetrahydrofurfuryl alcohol was studied in aqueous phase over a range of bifunctional catalysts based on Rh and an oxophilic promoter (Re, W, Mo) supported on ZrO2. The structures of the catalysts were characterised employing powder XRD, Raman spectroscopy and TEM analysis. The degrees of reduction were evaluated by H2-TPR and XPS analyses. The metallic properties were assessed by CO chemisorption. For the first time, the acidic properties were evaluated in aqueous phase by calorimetric measurements of 2-phenyl-ethylamine adsorption heat. The combination of metallic Rh sites and Bronsted sites (linked to the oxophilic metal on ZrO2) is crucial for the reaction. The bifunctionality of the catalysts was demonstrated and up to 81% yield of 1,5-pentanediol is obtained with 5%Rh-4%Mo/ZrO2.

Composite sorbents based on silica, polyethylene glycol (PEG) and containing calcium chloride were successfully synthetized using the sol-gel method. Their heat storage performance was investigated in a lab-scale open fixed-bed reactor. The silica/PEG matrix managed to stabilize hydrated calcium chloride when the salt content was equal to 32 wt% despite partial salt deliquescence. The presence of a crystallized phase CaCl2/PEG resulting from the complexation of the salt by the polymer may indeed prevent salt leakage, which was observed only when the salt content was increased to 42 wt%. Comparative experiments with a PEG-free control sample confirmed that the polymer enhances material stability. With a regeneration temperature of 130 degrees C, the best performing com-posite sorbent exhibited an average water sorption capacity of 0.37 gH(2)O g(-1) of dehydrated material and an energy density of 782 kJ kg(-1) over four successive sorption cycles at 30 degrees C and 42 % relative humidity. The dispersion and accessibility of the salt was enhanced after its first dissolution in the reactor. Compared to zeolite 13X, the sorption kinetics of the composite is much slower, resulting in a halved generated power. Still, the mass energy density of the composite is 70 % higher than that of zeolite, which makes it a promising material for heat storage applications with moderate required power outputs.

The present review aims at summarizing the scientific literature data and patents concerning the isobutanol, preferably from a fermentation process, selective dehydration reaction to produce isobutene (isobutylene). The benefits and drawbacks of the conditions used on the process design and catalyst performances are illustrated, analyzed and discussed with much objectivity. Thermodynamic equilibria of the various reactants and products are provided together with the limiting step rate. Isobutanol selective dehydration to isobutene can be done under low or high pressure conditions. This choice impacts not only the downstream recovery and purification of isobutene, but also the stability of the catalyst and the reactor volume. Due to the strong inhibition of the alumina catalysts by steam, the reaction under pressure requires longer contact times and catalyst volume. The alumina catalysts need to have a good hydrothermal stability to avoid a rapid deactivation. Isobutene purifi-cation is also addressed. The impact of the water partial pressure on the catalytic dehydration is described and shown to affect the side reactions. Mass transfer limitations and kinetics of the reaction are well documented. Relevant advices are provided to perform the reaction without undesired products.

Through the Mg/MgH2 system case study, this chapter presents the primary interest of thermal analysis and calorimetry to study the hydrogen storage properties of solid-state materials in detail. The dehydrogenation temperature and the hydrogen storage capacity can be obtained by performing temperature programmed desorption and thermogravimetric analysis experiments. These two techniques allow fast experiments with only a few milligrams of sample and are generally used in the literature to study the potential of a new additive, the influence of the preparation method, and to test the performances of new storage systems.

This work reports on the production of acrolein by oxidative coupling of biosourced alcohols (methanol and ethanol). This reaction is performed in a two-step process using iron molybdate catalyst to produce formaldehyde and acetaldehyde and zinc and cobalt aluminate spinels, with or without vacancies, to perform the cross-aldolization of aldehydes. In this study, adsorption microcalorimetry of NH3 and SO2 was used to determine the acid-base properties of the catalysts. The catalytic activity was monitored and correlated to catalysts acid-base properties. Moreover, to enlighten the behavior of reactants over the surface and the mechanism of the reaction, an extensive adsorption microcalorimetric study using acetaldehyde and formaldehyde as probe molecules was performed to determine molar enthalpies, molar entropies, thermokinetic parameters but also energy spectra. This broad calorimetric study provided a better understanding of the reaction and allowed to confirm the preferential adsorption of formaldehyde compared to acetaldehyde thus justifying the absence of crotonaldehyde in the products of the catalytic reaction.

13X zeolite in powder displays higher storage performances and faster hydration kinetics than 13X in beads. Salt-doped zeolite composite in powder form presents lower pore blockage and higher storage performances than composites in beads.

Aluminum fumarate - porous alumina (AF/Al), synthesized by reactive seeding method, has been used for the first time as a host matrix for CaCl2-based composite sorbents (CSPM) for thermochemical heat storage (TCHS) applications. The porous matrix and composites containing varying amounts of CaCl2 (20-60 wt%) were fully characterized by combining multiple techniques (N-2 adsorption/desorption isotherms, powder X-ray diffraction, scanning electron microscopy, elemental analysis). The storage performances of the studied materials have been investigated using thermogravimetry coupled to differential scanning calorimetry (TG/DSC) and a humidity generator. The results show that the hierarchical porous structure of AF/Al impacts the physico-chemical characteristics, water and heat storage performances and water sorption kinetics. The properties of AF/Al, presenting both micro and mesoporosity, as host matrix for CaCl2 have been compared with those of microporous AF and mesoporous Al. It is evidenced that in AF/Al, the presence of micropores arising from the AF membrane enhances the storage capacity of Al by increasing the number of available sorption sites, while the textural mesoporosity of Al offers favorable conditions for water vapor diffusivity, which is crucial for optimal mass and heat transfer. CaCl2-AF/Al composites exhibit enhanced water and heat storage capacities compared to the matrix alone, their performances increasing with the salt content to attain 1930 kJ kg(-1) and 0.68 kgH(2)O kg(-1) for 61 wt% of salt. The hydration level at 25 C and 30%RH did not exceed a maximum of 4.4 nH(2)O/n(anhydrous material), limiting deliquescence and leaching of the salt. A comparative study of the impact of host matrix characteristics on CSPM properties highlights the predominant impact of the salt content on the storage capacity, as well as the influence of porosity on the water vapor sorption behavior.

Electrochemical advanced oxidation processes (EAOPs) are effective and environmentally friendly for the treatment of refractory organic pollutants. Among EAOPs, heterogeneous electro-Fenton (EF) process with in-situ formation of hydrogen peroxide (H2O2) is an eco-friendly, cost-effective and easy-operable technology to generate hydroxyl radicals (•OH) with high redox potential. The generation of •OH is determined by the synergistic H2O2 formation and activation. The surface catalytic mechanisms for H2O2 activation in the heterogeneous EF process were discussed. Some required features such as heteroatom doping and oxygen groups for H2O2 formation via selective two-electron oxygen reduction reaction (ORR) with carbonaceous electrode are summarized. The solid Fenton catalysts and integrated functional cathodes that widely used in heterogeneous EF for wastewater treatment are grouped into few classes. And the brief discussion on catalytic activity and stability of materials over different experimental conditions are given. In addition, the application of heterogeneous EF process on the remediation of emerging contaminants is provided. The challenges and future prospects of the heterogeneous EF processes about catalytic fall-off and multi-step/complex techniques for water purification are emphasized.