Chemical condensation of layers of silicates has been often proposed as an alternative to thermal condensation, finding limited success. The formation of the industrially relevant MCM-22 zeolite (MWW IZA code) from a mild hydrothermal precursor is the most important example of 2D-3D aluminosilicate condensation. Silanols of opposed layers have been condensed by acid-driven dehydration in concentrated nitric acid, as confirmed by powder XRD and 29Si NMR spectroscopy, implying interlayer template extraction and corresponding dealumination. Milder acid treatments favour template extraction and shrinkage of interlayer distance, but do not provide significant silanol condensation. Template extraction is further favoured by degradation of the organics in the presence of a Cu2+ homogeneous catalyst.

Mild catalytic oxidation of thioethers and thiophenes is an important reaction for the synthesis of molecules with pharmaceutical interest, as well as for the development of efficient processes able to remove sulfur-containing pollutants from fuels and wastewater. With respect to the green chemistry principles, hydrogen peroxide (H2O2) is the ideal oxidant and the Me-containing porous materials (Me = Ti, V, Mo, W, Zr) are among the best heterogeneous catalysts for these applications. The main classes of catalysts, including Me-microporous and mesoporous silicates, Me-layered double hydroxides, Me-metal–organic frameworks, are described in this review. The catalytic active species generated in the presence of H2O2, as well as the probable oxidation mechanisms, are also addressed. The reactivity of molecules in the sulfoxidation process and the role played by the solvents are explored.

Pseudomorphic transformation of pre-shaped silica beads into MCM-41 and MCM-48 is introduced as a new versatile procedure to independently control and finely tune the textural characteristics of advanced high-performance chromatographic supports at nano- and micrometer scale. The reaction takes place in the intergranular porosity of the parent silica-gel particle which acts as a nanoreactor. Because the resulting hybrid mesophase is metastable in its synthesis medium, the kinetics of each of the elementary steps–diffusion of hydroxide and surfactant, dissolution of parent silica, self-assembly, condensation of the new silica network-must be precisely controlled. In the paper examples are given of the preparation of discrete homodisperse spherical particles of MCM-41 and MCM-48, with pore sizes in the range 4 to 9 nm, form different silica sources.

γ-Al 2 O 3 is promising for catalytic ozonation because it produces HO° radicals. To improve its basicity and/or its oxidative character, highly mesoporous γ-Al 2 O 3 was doped with different metals M alone or in mixture (M = Mg, Ca, Zn, Fe, Ba, Zr, Cu, Co, Ni, Ce, Ti, with 0.05 < M/Al < 0.5 molar ratio) prepared either by incipient wetness deposition or by direct sol-gel. Tests to determine the basic and oxidative character of the catalysts have been set up. Results show that Mg-doped alumina materials exhibited the highest basicity and Cu,Mg-doped alumina materials the highest oxidative character. These materials (5 g/L) were tested in the catalytic ozonation of a synthetic saline (NaCl = 50 g/L) petroleum effluent such as produced water (TOC = 216 mg/L) containing phenols, acetic acid and polycyclic aromatic hydrocarbons. Among these catalysts, Mg-doped alumina with molar ratio Mg/Al = 0.1, 0.2 prepared by incipient wetness deposition were the more efficient catalysts. Under reuse the Mg-doped alumina catalyst (Mg/Al = 0.1) exhibited the highest ozonation rate with 98% TOC removal in 5 h. This remarkable behavior was attributed to the in-situ formation during ozonation of spinel (MgAl 2 O 4 ) nanoparticles at the surface of Mg-doped alumina particles.

For the first time, the real-time thermal activation of the NH4-omega zeolite (NH4-omega) was investigated through in situ synchrotron X-ray powder diffraction combined with neutron diffraction. The experimental approach allowed to study the precursor thermal behaviour upon heating, continuously monitoring the evolution of its structural features determined by NH4 ions and TMA calcination and dehydration processes. The activation of the precursor (H-omega sample) is fully reached at similar to 600 degrees C, when all the NH4 content has been released, dehydration mostly occurred and TMA degradation completed. From a structural point of view, Rietveld structural refinements highlighted relevant structural changes. In particular variations in intertetrahedral angles allowed to make hypothesis about the possible distribution of Bronsted acid sites on the framework oxygen atoms. The hypothesis was corroborated through the neutron Rietveld refinement of the deuterated and calcined omega (D-omega sample) that revealed the presence of two acid sites: D1 and D2 located on O5 and O2 framework oxygen atoms, respectively. Besides, neutron data confirmed the strong relation among framework and Br:misted acid sites geometry and short- and/or long-range interactions. In summary, non-conventional sources were successfully used to probe both activation and formation of acidic sites in omega precursor as well as determine the number and location of Bronsted sites in the deuterated omega.

n-Hexadecane hydroconversion has been investigated in a series of bifunctionnal metal/acid catalysts featuring distinct well-defined pore architectures. The acidic components were prepared from dealuminated Y zeolites with Si/Al of 15 and 30 post treated in alkaline medium to generate ordered or non-ordered secondary networks of mesopores and from aluminated ordered mesoporous materials MCM-41, MCM-48, KIT-6 type materials and amorphous silica gel. Activity relates linearly to the strength and number of strong Brönsted acid sites, while selectivity, more precisely the yield in isomerization products, scales directly with the mesopore volume of the catalyst. The architecture of the mesoporous network, namely the ordering, interconnectivity, homogeneity of the mesopores, affects little catalytst behavior. Confrontation of catalytic data with diffusion measurements suggests the existence of an optimal mesopore size above which the number of strong Brönsted sites and the mesopore volume are the only parameters governing catalytic performance.

The performances of binderless FAU-X monoliths (0.5 x 3 cm) build of nanocrystals featuring hierarchical trimodal porosity (micro-/meso-/macroporosity) in decontamination Cs-containing effluents have been evaluated. They have been compared to those obtained with newly synthesized FAU-X particles (1 mm) build with nano crystals. Data have been confronted to those recently reported for a benchmark reference Cs+ adsorbent Sorbmatech (R), based on copper hexacyanoferrate nanoparticles (15 nm) immobilized into mesoporous silica particles (250-500 pm) (Cu-HCF@SiO2). FAU-X monoliths show high rate of adsorption in batch in less than 2 min, much faster than Cs+ adsorption in FAU-X particles (60 min). This result highlights the importance of a homogeneous macropore network in adsorbents to enhance mass transport and access to the zeolite active sites. FAU-X monoliths with 20 mu m macropore diameter have been used in continuous flow experiments for sequestering Cs+ (0.5 mmol/L) in mineral drinking water containing competing cations (Ca2+, Mg2+, Na+, K+) with flow rates of 0.5-1 mL/min, corresponding to Darcy rates of 1.5-3 m/h. FAU-X monoliths are very efficient for Cs+ removal and show ideal steep breakthrough curves characteristic of fast diffusion. FAU-X monoliths are as excellent as Cu-HCF@SiO2 and could represent an alternative adsorbent for safer processes, avoiding the handling of powders or particles. Above all, this study reveals the unique hydrodynamic behavior of FAU-X monoliths and opens the route for process intensification using FAU-X in continuous flow.

C,N-TiO2 monoliths with homogeneous interconnected macro-/mesoporous hierarchical porosity, consisting in 83% anatase phase, exhibiting high visible light absorption were prepared in one pot synthesis. The hierarchical porosity was controlled by coupling a sol-gel method with a spinodal decomposition and the improved visible light absorption was obtained by self C,N-grafting during thermal treatment. Titanium isopropoxide, N-methylformamide, poly(ethylene oxide), and hydrochloric acid were used as reagents to form a sol, which was then treated at 40 and 60 degrees C, followed by a solvothermal treatment in autoclave at 200 degrees C in isopropanol. The monoliths were further heated at different temperatures from 250 to 500 degrees C under air. The best compromise between the structural and textural properties (TiO2 phase, surface, volume, pore diameter), the visible light absorbance and the mechanical properties was obtained for a calcination at 350 degrees C for 5 h. In batch mode, in glass containers, the monoliths demonstrated remarkable efficiency as photocatalysts under natural sunlight and artificial visible light with the total discoloration of the azo dye Orange G aqueous solution in 1 h compared to benchmark TiO2 P25 nanoparticles, which proved inefficient under these conditions. More interestingly, the monoliths used as reactors in flow mode in a recirculating system proved very efficient for the total discoloration of Orange G dye solution revealing the high potential of these TiO2 monoliths for continuous flow wastewater treatment under visible light.

In this study, we show that the Friedel-Crafts (FC) alkylation of aromatic hydrocarbons by thiols to form C-C bond is feasible. The gas-phase reaction between toluene and CH3SH catalyzed by HZSM-5 zeolite was chosen as model reaction. In the temperature range of 350-550 degrees C, the alkylation of toluene to produce xylenes was the main reaction involved in the process. The reaction between toluene and CH3SH was compared with the well-known reaction between toluene and CH3OH. Significant similarities exist, notably the ability of both CH3SH and CH3OH to generate methoxonium species on the zeolite surface and to methylate the aromatic ring in a typical FC process. The maximum alkylation yield of 41% for CH3OH was reached at 350 degrees C, while that of 67.3% for CH3SH was reached at 450 degrees C. This difference in temperature can be correlated with the energy barriers required for the formation of methoxonium species (i.e., 24.6 kcal/mol (CH3OH) and 26.4 kcal/mol (CH3SH)). The high performance in alkylation proved by CH3SH was attributed to its lower consumption in the side reactions (i.e., the formation of light hydrocarbons).

Chemical phase separation and pseudomorphic transformation are very powerful tools for fine tuning the porous architecture of inorganic oxides. In this short review the basic principles of the preparation of centimetric bodies made of zeolites is introduced. The synthesis of monoliths with homogeneous distributions of interconnected macropores with skeleton made of SOD, LTA and FAU crystals is described. Their unique hierarchical porous texture featuring the structural micropores, intercrystalline mesopores and flow-through macropores leads to remarkable hydrodynamic behavior in separation, catalysis and ion exchange processes operated in continuous-flow mode. In the base-catalyzed carbon-carbon bond formation, productivities twice those achievable with fixed-beds of packed particles are observed. In the capture of strontium present in radioactive effluents their efficiency is three orders of magnitude that of traditional powder in batch.

Self-standing binderless FAU-X monoliths with hierarchical trimodal porosity have been synthesized for the first time by a double pseudomorphic transformation. Parent silica monoliths obtained by the combination of spinodal decomposition and sol-gel process have first been synthesized. The silica monoliths have been then transformed into silica-alumina monoliths (0.25 < Al/Si < 0.40) in low NaOH concentration ([NaOH] = 0.24 mol/L) at 40 degrees C for 24 h. Silica-alumina monoliths have been then transformed into FAU-X monoliths featuring nanocrystals in the struts at high NaOH concentration ([NaOH] = 2.2 mol/L) with an aging step at 40 degrees C for 4 days and a crystallization step at 100 degrees C for 24 h. The FAU-X monoliths feature macropores with diameters adjustable from 3 to 20 mu m (similar to the parent silica monolith). The skeleton of the FAU-X monoliths is formed by an aggregation of two populations of FAU-X nanocrystals (100-200 nm/400-500 nm) generating a secondary porosity between the nanocrystals of 30-1000 nm in diameter, centered at 300 nm. The FAU-X monoliths present three levels of porosity with a macropore volume of ca. 1.0 mL/g, a secondary pore volume of ca. 0.40 mL/g and a micropore volume of 0.30 mL/g. These new FAU-X monoliths with hierarchical porous structure fulfill the requirements of high performance adsorbents for continuous flow process intensification.

In this study, we report that ethylene can be simultaneously and selectively converted into propylene and 1-butene through one-pot catalytic cascade reactions. In a single continuous-flow reactor and under identical mild conditions (60 degrees C, 3 MPa), without the use of cocatalyst, ethylene was first dimerized/isomerized over Ni-AlKIT-6 catalysts to form butenes, which reacted then with the excess of ethylene over ReOx/Al2O3 to produce propylene and 1-butene with more than 86% total selectivity. The selectivity for 1-butene was 97.4% in the C-4 fraction. The initial ethylene conversion was 73% and stabilized at 35% after 4 h on stream, with around 45% selectivity in propylene and 42% selectivity in 1-butene.

The texture of mesoporous FAU-Y (FAUmes) prepared by surfactant-templating in basic media is a subject of debate. It is proposed that mesoporous FAU-Y consists of: (1) ordered mesoporous zeolite networks formed by a surfactant-assisted zeolite rearrangement process involving local dissolution and reconstruction of the crystalline framework, and (2) ordered mesoporous amorphous phases as Al-MCM-41, which coexist with zeolite nanodomains obtained by a dissolution-reassembly process. By the present systematic study, performed with FAU-Y (Si/Al = 15) in the presence of octadecyltrimethylammonium bromide and 0 < NaOH/Si ratio < 0.25 at 115 degrees C for 20 h, we demonstrate that mesoporous FAU zeolites consist, in fact, of a complex family of materials with textural features strongly impacted by the experimental conditions. Two main families have been disclosed: (1) for 0.0625 < NaOH/Si < 0.10, FAUmes are ordered mesoporous materials with zeolite walls, which coexist with zeolite nanodomains (100-200 nm) and (2) for 0.125 < NaOH/Si < 0.25, FAUmes are ordered mesoporous materials with amorphous walls as Al-MCM-41, which coexist with zeolite nanodomains (5-100 nm). The zeolite nanodomains decrease in size with the increase of NaOH/Si ratio. Increasing NaOH/Si ratio leads to an increase of mesopore volume, while the total surface area remains constant, and to a decrease of strong acidity in line with the decrease of micropore volume. The ordered mesoporous materials with zeolite walls feature the highest acidity strength. The ordered mesoporous materials with amorphous walls present additional large pores (50-200 nm), which increase in size and amount with the increase of NaOH/Si ratio. This alkaline treatment of FAU-Y represents a way to obtain ordered mesoporous materials with zeolite walls with high mesopore volume for NaOH/Si = 0.10 and a new way to synthesize mesoporous Al-MCM-41 materials containing extralarge pores (50-200 nm) ideal for optimal diffusion (NaOH/Si = 0.25).

Desilication and recrystallization of a low-silica NaK-form ferrierite (NaKFER) were conducted by one-step hydrothermal method in sodium hydroxide solution containing cetyitrimethylammonium bromide (CTAB). The attack by NaOH induced unprecedented mesopore formation in highly stable ferrierite crystals through framework desilication. interestingly, the generated mesopores are parallelepiped shaped and oriented along the [001] directions (10 MR) of the FER structure. The CTAB surfactant could be inserted between the layers of ferrierite crystals under the assistance of NaOH. This process was associated with the formation of occluded mesopores and led to partial delamination of layered crystals. Under severe treatment conditions, NaKFER transformed to GIS and SOD phases, successively. The samples were characterized by XRD, N-2 sorption, SEM, TEM, EDS, TG, etc. The influence of NaOH concentration, temperature, reaction time, CTAB and cation form of the parent zeolite was investigated in order to study the mechanism of mesopores formation, delamination process and phase transformation of ferrierite. Phase diagrams were established to show the transformation process of NaKFER as a function of NaOH concentration, reaction time and temperature. (C) 2017 Elsevier Inc. All rights reserved.

LTA zeolite monoliths (6 mm diameter, 3 cm length) featuring a hierarchical trimodal network of micro-/meso- and macropores (obtained by either controlling the nucleation step of LTA crystallization into nanocrystals or by creating mesopores into micronic crystals by using organosilane surfactant) were used for strontium capture in aqueous medium. LTA monoliths were compared to other LTA zeolite architectures: LTA microcrystals, commercial LTA beads and bimodal micro-/macroporous LTA zeolite monoliths. In batch mode, the presence of mesopores allowed to increase remarkably by a factor 15 the diffusion of ions, whereas macropores had no influence on ions transport. In flow mode, only LTA monoliths featuring flow-through macropores proved suitable as microreactors. The trimodal LTA monoliths were 1000 times more efficient than packed-beds of LTA beads, and 4 times than bimodal (micro-/macroporous) LTA monoliths due to higher rates of diffusion. Trimodal LTA monoliths were able to treat efficiently 4 L of Sr2+ solution (10 mg L-1) with 1 mL of material at a flow rate of 0.5 mL min(-1) (or 1 m h(-1)); ie. 4200 bed volumes (BV) were efficiently treated at a flow rate of 34 BV h(-1), with no Sr2+ detectable by ionic-chromatography in the effluent. This result highlights the fact that the multiscale pore architecture engineering of an adsorbent is crucial for process intensification: macropores allow uniform mass transport of solutions with low pressure drop while the generation of mesopores in zeolites leads to faster ionic transport and more efficient crystal use in cation-exchange processes, both in batch and flow modes. (C) 2016 Elsevier Inc. All rights reserved.

LTA zeolites are used in many applications as diverse as chemistry, physics, medicine, agriculture. By exploiting the concept of pseudomorphic transformation, i.e. using silica monoliths featuring macro- and mesopores as silica source, we manage to shape LTA zeolites as centimetric monoliths (6 mm diameter, 5 cm length) with trimodal hierarchical porosity (micro-, meso- and macropores). The skeleton of the monolith is formed by an aggregation of LTA nanocrystals of ca. 100 nm leading to mesopores due to voids between the nanocrystals. Diverse LTA nanocrystal shapes and sizes were realized by controlling aging time and crystallization temperature. These unique self-standing monoliths of LTA nanozeolites feature flow-trough macropores of 3-4 microns highly suitable for high mass transport of liquids, homogeneous distributions of mesopores for high diffusion of molecules and ions and therefore a high accessibility to zeolites active sites. Together with an easy handling, these materials offer the possibility to intensify many processes using classical LTA zeolite crystals. (C) 2016 Elsevier Inc. All rights reserved.

Silica monoliths featuring either mesopores or flow-through macropores and mesopores in their skeleton are prepared by combining spinodal phase separation and sol-gel condensation. The macroporous network is first generated by phase separation in acidic medium in the presence of polyethyleneoxides while mesoporosity is engineered in a second step in alkaline medium, possibly in the presence of alkylammonium cations as surfactants. The mesoporous monoliths, also referred as aerogels, are obtained in the presence of alkylpolyethylene oxides in acidic medium without the use of supercritical drying. The impact of the experimental conditions on pore architecture of the monoliths regarding the shape, the ordering, the size and the connectivity of the mesopores is comprehensively discussed based on a critical appraisal of the different models used for textural analysis.