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ZSM-5 zeolite is the synthetic counterpart to mutinaite. After thermal activation of the as-synthesized form, the symmetry of the ZSM-5 zeolite is lowered to the monoclinic P21/n. ZSM-5 then undergoes a polymorphic displacive phase transition from the monoclinic P21/n to the orthorhombic Pnma, Pn21a or P212121 space groups, which occurs upon heating. This phase transition can be influenced by factors such as the type and amount of sorbate molecules present in the zeolite channels. ZSM-5 has many applications, including as a catalyst or sorbent in various industries, where high thermal stability is required. In this study, four ZSM-5 zeolites with different Si/Al ratios were investigated by synchrotron X-ray powder diffraction at both room temperature and high temperature conditions to determine the effects of chemical composition on the structural response of the zeolite lattice. The results showed that the ZSM-5 zeolites retained their crystallinity and structural features throughout the thermal treatment, indicating that they could be used as effective acid catalysts. Distortions in the zeolite framework can occur after TPA+ decomposition and thermal activation, affecting thermal regeneration and efficiency. The charge balance in ZSM-5 is achieved by the formation of Brønsted acid sites, and variations in bonding geometries are influenced by the initial Si/Al ratio.

A modified technique of epitaxial growth employed to produce “core-shell” catalysts coating microporous ZSM-5 with a layer of Silicalite-1 is presented in this paper. The aim was to passivate surface acidity of a ZSM-5 zeolite, in the view of potential limitation of surface effect generally responsible for coke formation. Core-shell catalysts have been synthetised starting from a ZSM-5 core with Si/Al=25. Two different hydrothermal Silicalite-1 synthesis were performed: one using the ZSM-5 as made-form and the second using the ZSM-5 H+-form as core. This allowed to investigate the effect of the organic template, filling the pores of the core, on the shell growth mechanism. Coating procedure lasted 24 h and it was repeated twice to increase Silicalite-1 thickness. All catalysts were tested for the reaction of methanol dehydration to DME in an atmospheric system at 180-240° and time on stream tests were carried out to analyse the stability of the samples. Considering the catalytic performances in terms of methanol conversion, DME selectivity and deactivation, core-shell catalysts, synthetized using an as-made form core, exhibited interesting performances, resulting from a more controlled growth of the passivating layer. These materials could constitute valid option for hybrid (Metal-Zeolite) catalyst, where the reduction of surface acidity could better stabilise the metallic function.

International audience

Acid catalysis is recognised as the most reliable industrial ì way to convert hydrocarbons into various products (methanol to olefins and aromatics, glycerol to olefins, methane dehydroaromatization, isomerization, etc.). In this concern, ZSM-5 is extensively used, also because of peculiar type of active sites of such zeolite. In this paper, a fine tuning of the acidity content and strength of ZSM-5 was investigated through a combination of post- synthesis treatments: desilication via alkaline solution and wet impregnation with Mg2+ions followed by calcination. Results show that the insertion of Mg2+has a large influence on the distribution and strength of Brønsted and Lewis acid sites of the hierarchical ZSM-5, as well as an improved crystallinity with respect to the desilicated-one. The hierarchical ZSM-5 zeolite incorporating Mg-species was tested in Methanol- to-olefins reaction and the reduction of acid strength of catalyst increased the selectivity toward light olefins (mainly propylene) as well as it suppressed oligomerisation reactions delaying the coke formation.

The high-pressure behavior of six synthetic zeolites with the MFI topology, characterized by different chemical composition (framework-Si partially replaced by Al or B and counterbalanced by Na or H as extra-framework cations), has been investigated by in-situ powder synchrotron X-ray diffraction using silicone-oil and methanol as hydrostatic pressure-transmitting fluids. For each sample, the compressibility in silicone-oil has been found to be considerably higher than that in methanol. This difference in terms of bulk elasticity is due to the adsorption of methanol already at P < 0.1 GPa, with different magnitudes as a function of the sample crystal-chemistry. The high number of experimental pressure points allowed an accurate determination of the monoclinic-to-orthorhombic phase transition (MOPT), detected between 0.3 and 0.7 GPa in the samples compressed in silicone-oil, whereas the orthorhombic Pnma polymorph has been found to be stable already at ∼ 0.1 GPa in four samples compressed in methanol. This suggests that the adsorption of methanol may increase the P-stability range of the orthorhombic Pnma phase. A comparative analysis of the effect of pressure on the methanol adsorption by MFI-zeolites with different chemical composition is provided, which offers potentially useful information on their application as catalysts in the methanol-to-olefins conversion processes and in industrial high-pressure processes.

Rare earth elements (REEs) are strategic materials widely used in different applications from Information and Communication Technologies (ICT) to catalysis, which are expected to grow more in the future. In order to reduce the impact of market price and reduce the environmental effect from soil extraction, recovery/purification strategies should be exploited. This paper presents a combined acid-leaching/oxalate precipitation process to recover lanthanum from spent FCC catalyst using nitric acid. Preferred to hydrochloric and sulphuric acid (preliminary assessed), HNO3 showed a good capability to completely leach lanthanum. The combination with an oxalate precipitation step allowed demonstrating that a highly pure (&gt, 98% w/w) lanthanum solid can be recovered, with a neglectable amount of poisoning metals (Ni, V) contained into the spent catalyst. This could open a reliable industrial perspective to recover and purify REE in the view of a sustainable recycling strategy.

The production of DME via one-pot CO2 hydrogenation is a strategic way of recycling CO2 with the production of a high-value added product. This work aims to investigate the effect of the main zeolite features, e.g. structure or acidity, on the activity, selectivity and stability of the catalyst for DME production via both methanol dehydration and one-pot CO2 hydrogenation. Several zeolites (i.e. FER and MFI) were synthesized and deeply characterized with XRD, B.E.T, NH3-TPD and FTIR. Obtained crystals were used as catalysts for methanol dehydration as well as for one-pot CO2-to-DME process. Obtained results allow giving new insights about the role of the interaction between metals and acid sites for an efficient DME production via one-pot CO2 hydrogenation. In particular, zeolite acidity plays a crucial role in methanol dehydration step and Lewis acid sites seems to be more active than Brønsted sites. Furthermore, metal/acid proximity plays are a key factor in one-pot CO2 hydrogenation; in fact, the catalytic performances of multifunctional catalytic bed improve by increasing the metal/acid sites proximity. The findings of this research allow to highlight the main factors to be taken into account in terms of design and optimization of new catalytic systems for DME synthesis.

The catalytic conversion of methanol to dimethyl ether (DME) over a series of home-made FER-type zeolites having different acidities and commercial γ-Al2O3 has been studied with the aim to understand the impact of adding water in the reactant stream on the catalytic behavior on investigated materials. Co-feeding water with methanol, the alcohol conversion was slightly reduced over the investigated zeolites while the catalytic activity of γ-Al2O3, the traditional catalyst of MeOH-to-DME conversion, was strongly inhibited. It was also found that, for the investigated zeolites, both the amount and the initial deposition rate of the coke formed during the reaction were reduced when water was co-fed with methanol while no significant effects on both methanol conversion and DME selectivity were observed under the investigated conditions.

The adsorption of the amino acid, l -lysine, on two ZSM-5 having different silicon to aluminium ratio (i.e. Si/Al = 15 and 37) has been investigated by experiments at macroscopic and at atomistic level resolution. The kinetic and equilibrium constants of the adsorption processes obtained for both the adsorption materials, show that Al content is an important factor in tuning the adsorption of the amino acid on the zeolite. Both the saturation capacity and the binding constant decrease as Si/Al ratio increases. The refinements of high resolution X-ray diffraction data obtained from synchrotron radiation, indicate that adsorption of l -lysine in ZSM-5 is a surface-confined supramolecular self-assembly process. l -lysine molecules at the intersection of the sinusoidal and the straight channels, are arranged in a α-helical conformation stabilized by the simultaneous occurrence of strong H-bonds among the tail of l -lysine molecules, water molecules and framework oxygens. l -lysine molecules within the sinusoidal channel are arranged as β-sheets forming infinite hydrogen-bonding β-strands with the framework oxygens. Our results suggest that l -lysine conformation strongly depends on both pH and hydration state influencing amino acids physico-chemical properties and intermolecular bond energies.

FER-type zeolite was recently recognized as good catalyst for DME synthesis via methanol dehydration or one-pot CO2 hydrogenation, in terms of DME selectivity, stability and coke formation. In this research, we investigated the role of crystal size of both FER- and MFI-type zeolites on catalysis of methanol dehydration to DME reaction. The results show that FER-type zeolites, both micro- and nano-sized, exhibit better performances than micro-sized MFI-type zeolite. On the contrary, the application of nano-sized MFI allows to obtain a DME selectivity similar to FER, but with higher DME production rate and a lower coke deposition.

Porous carbon materials are currently subjected to strong research efforts mainly due to their excellent performances in energy storage devices. A sustainable process to obtain them is hydrothermal carbonization (HTC), in which the decomposition of biomass precursors generates solid products called hydrochars, together with liquid and gaseous products. Hydrochars have a high C content and are rich with oxygen-containing functional groups, which is important for subsequent activation. Orange pomace and orange peels are considered wastes and then have been investigated as possible feedstocks for hydrochars production. On the contrary, orange juice was treated by HTC only to obtain carbon quantum dots. In the present study, pure orange juice was hydrothermally carbonized and the resulting hydrochar was filtered and washed, and graphitized/activated by KOH in nitrogen atmosphere at 800 &deg, C. The resulting material was studied by transmission and scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and nitrogen sorption isotherms. We found porous microspheres with some degree of graphitization and high nitrogen content, a specific surface of 1725 m2/g, and a pore size distribution that make them good candidates for supercapacitor electrodes.

In this work, two ZSM-5 type zeolite supported membranes were used as catalytic membrane reactors for dimethyl ether (DME) synthesis via MeOH dehydration. The membranes, both commercial and tubular, had the same ZSM-5 zeolite layers, but a different support each (TiO2 and gamma-Al2O3) and were operated as contactors in through flow configuration. The performance of the two membrane reactors was analyzed as a function of the temperature (150-250 degrees C) and feed pressure (120-300 kPa), spanning a wide range of WHSV (1-13.3 g(MeOH) g(Catalyst)(-1) h(-1)) and feed composition (25-100%(mol) MeOH). The ZSM-5-Al2O3 membrane (Si/Al = 200; porosity of the zeolite layer = 0.2; thickness = 50 mu m; area = 50.6 cm(2)) exhibited always a greater conversion than ZSM-5-TiO2 (Si/Al = 200; porosity of the zeolite layer = 0.2; thickness = 63 mu m; area = 18.8 cm(2)), revealing an influence of the membrane support, correspondent to an additional catalytic effect induced by the Al2O3, which further enhanced the DME production. At 200 degrees C and 1 h(-1), this reactor achieved a MeOH conversion of 86.6 +/- 6.7%, very close to thermodynamic equilibrium conversion. In addition, both membrane reactors showed 100% DME selectivity.

International audience; Ferrierite zeolite crystals were successfully prepared by a long amine as 1,8diaminoctane (DAO) as organic structure directing agent. By comparison, shorter amine, i.e. ethylenediamine (EN), was also used as OSDA. Results shows that the presence of DAO reduces the crystallization time and allows to obtain single FER-type crystlas with smaller size and higher acidity, being these significant parameters to take into account when zeolites are applied in catalysis. The obtained samples were characterized with XRD, TG/DTA, SEM, N 2 adsoprtion/desorption, FTIR and 27 Al-NMR. In particular, TGA clearly shows that DAO may be accommodate in zeolite framework and theoretical modeling suggests a preferential location in the 10-MR ring channels.

The modification of the physicochemical properties of synthetic zeolites is an important element when these materials are applied as heterogeneous catalysts in the view of more sustainable and effective processes. In this work, desilicated ZSM5 samples were tested on the methanol to dimethyl ether dehydration. Desilication time strongly affects the textural and acidic properties of the samples, and those characteristics determined a different catalytic behaviour. Contact time of 60 min with NaOH solution (alkaline desilication) favourably impact on the activity of the catalysts and its stability against deactivation in terms of methanol conversion and yield to DME, in comparison with parent zeolite and sample prepared after 30 min of desilication. This effect is due to a combination of changes in the properties of acidic sites and mesoporous volume, as confirmed by stability test over 80 h of reaction. The analysis of formed coke confirmed this evidence since the most performing catalyst showed the lowest tendency to form coke as the main consequence of the improved accessibility to the acid sites determined by the induced mesoporosity.

The procedures for the extraction and separation of lipids and nutraceutics from microalgae using classic solvents have been frequently used over the years. However, these production methods usually require expensive and toxic solvents. Based on our studies involving the use of eco-sustainable methodologies and alternative solvents, we selected ethanol (EtOH) and cyclopentyl methyl ether (CPME) for extracting bio-oil and lipids from algae. Different percentages of EtOH in CPME favor the production of an oil rich in saturated fatty acids (SFA), useful to biofuel production or rich in bioactive compounds. The proposed method for obtaining an extract rich in saturated or unsaturated fatty acids from dry algal biomass is disclosed as eco-friendly and allows a good extraction yield. The method is compared both in extracted oil percentage yield and in extracted fatty acids selectivity to extraction by supercritical carbon dioxide (SC-CO2).

MOR, BEA, MFI (containing or not Al) zeolites in the ammonium and protonic forms are studied in the etherification of HMF (5-hydroxymethylfurfural) in anhydrous ethanol. The conversion of HMF to 5-(ethoxymethyl)furan-2-carbaldehyde (EMF), and ethyl 4-oxopentanoate (EOP) occurs through two parallel reactions, which may be good described kinetically by pseudo-first order rates of formation, being the ethanol the co-reactant and the reaction medium. FTIR data with pyridine and 2,4,6-collidine as probe molecules are used to quantify the amount of Lewis and Bronsted sites in the samples. In the MOR, BEA, MFI (containing or not Al) series of zeolites in acid and ammonium form, a good relationship between the rate constant in EMF formation (k1) and the amount of strong Lewis acid sites (LAS) is observed. A correlation between rate constant in EOP formation (k2) and the amount of Bronsted acid sites (BAS) is instead observed. While the first correlation is independent on the acid or ammonium form, the second correlation depends on this aspect.

Conversion of methanol to dimethyl ether (DME) and hydrocarbons was investigatedover zeolites with several 1-dimensional channel systems: ZSM-12, ZSM-22 and EU-1. The effect of reaction temperature, contact time and Time-On-Stream towards methanol conversion and products selectivity was investigated. It was found that ZSM-22 zeolite exhibits the best performances during conversion of methanol to DME (temperature range 180–240 °C) as consequence of the particular shape selectivity that inhibits coke formation and deactivation. On the contrary, when formation of hydrocarbons is desired (temperature up to 320 °C), ZSM-12 shows the highest activity in terms of light olefin yield with the highest C 3 /C 2 ratio. The low selectivity towards C 2 formation can be associated to the absence of both di- and tri-methyl benzenes formed during the reaction because when these species were detected, a higher ethylene productivity was observed lowering the C 3 /C 2 ratio on the reactor out-stream.

The paper deals with the application of multiwall carbon nanotubes (CNTs) to the adsorption of dyes from wastewater. Textile dyes are dangerous and diffused pollutant in wastewater, and the paper results confirmed the good adsorption ability of CNTs, with respect to classic active carbon, even for different dye types. The effect of surface treatments of CNTs was primarily investigated, revealing that neither the presence of residual catalyst nor common surface treatment (oxidation) affects the CNT's performances. Therefore less expensive non-purified CNTs were assessed as good and economically convenient alternative for the process. In order to gain in generality in adsorption kinetic modelling, the parameters of the “best fitting” pseudo-second order model have been correlated to the main process variables (the dye initial concentration and the specific mass of CNTs.) setting-up a predictive kinetic model useful design new application of these materials in currently operating industrial operations for adsorption. In addition, isothermal data were used to screen all the relevant adsorption isotherms models and the Temkin model was confirmed as the more effective to accurately fit equilibrium data for any of the considered different dye types.

The FER-type zeolite was found to be a reliable catalyst for DME synthesis via both direct CO2 hydrogenation or gas phase methanol dehydration. In this work, the effect of the crystal size of FER-type zeolites on the catalytic behavior during methanol-to-DME conversion is studied. A series of FER-type crystals ranging from 0.1 μm to 10 μm in size were synthesized and their physicochemical properties (e.g. crystal morphology, acidity, textural characteristics) analyzed. The catalytic performance of FER-type catalysts was studied in a wide range of reaction temperatures (120–280 °C). The set experimental data show that the catalytic effectiveness of FER-type catalysts in terms of methanol conversion, DME selectivity and coke resistance, can strongly be improved by reducing the zeolite crystal size.

In this paper, a preliminary study of anaerobic digestion of organic fraction of municipal solid wastes (OFMSW) in presented with the aim to compare the performances of both wet- and dry-type reactors. The treatment of OFMSW via anaerobic digestion (AD) producing biogas is a process that is receiving a growing interest because two different needs can be coupled: the request of sustainable municipal waste treatments and increasing demand renewable energy. This paper aims to offer experimental results comparing batch test and continuous experimental reactors under different conditions of humidity and solid content. Results show that both the investigated configurations may be used for converting OFMSW into a high quality biogas and that the increase of dry matter in the continuous process still allows to achieve significant biogas production rates. A slight reduction of the methane content was observed (less than 5% relative) that can be also related to the change in the level of volatile fatty acids. These results are very promising in supporting the possibility of operating an industrial scale plant with a dry-process without affecting the system performance.

The treatment in NH4OH of Fe-Silicalite (Fe-MFI) catalysts creates mesopores with a different mechanism with respect to the conventional desilication treatment. A reassembling of Fe-MFI nanocrystals is induced by the creation of isolated defects on the surface of these nanocrystals, as well as a change in the amorphous layer between nanocrystals acting as “glue” to assemble them into larger round-shaped particles occurs. The reassembling process induces also changes in the acidity and hydrophobic character, leading to an enhanced reactivity, and influences the relatives rate constants in the HMF (5-hydroxymethylfurfural) etherification to 5-(ethoxymethyl)furan-2-carbaldehyde (EMF) via acetalization. Moreover, for treatment times with NH4OH longer than 6 h, there is an effective, although minimal, desilication process which leads to a loss of crystallinity, microporous surface area, mesoporosity and acidity characteristics with consequent worsening of the catalytic performances.

In contrast to high silica zeolites, it is difficult to obtain mesoporosity in zeolites with low Si/Al ratio (e.g., 2, HCl, and NaOH solutions and investigate the effect of both NaAlO2 solution concentration and time of treatment on the textural properties. The obtained materials exhibit a mesoporous volume higher than the parent ferrierite with no significant effect on the sample acidity. The catalytic activity of some samples was investigated in vapour-phase methanol dehydration to dimethyl ether, revealing the superiority of hierarchical zeolites in terms of methanol conversion, although the presence of mesopores causes formation of light hydrocarbons at high temperatures.

The production of DME from CO2 hydrogenation is a way of recycling CO2 and it requires the use of a hybrid multifunctional catalyst to efficiently catalyze the two consecutive reaction paths of methanol synthesis and methanol dehydration directly in one single step. The aim of this work is to investigate the utilization of zeolite-based catalysts for dimethyl ether synthesis by assessing the role of catalyst features in both methanol dehydration and one-pot CO2 hydrogenation. Obtained results, discussed in terms of turnover frequency reveal that FER-type zeolite prepared with Si/Al=10 exhibits the best performances during vapor-phase methanol dehydration whilst the efficiency of CO2-to-DME process strongly depends on the way in which metallic and acidic materials are coupled. Single grain prepared via gel-oxalate precipitation of CuZnZr over zeolite crystals exhibit the best performances in terms of CO2 conversion and DME productivity.

CO2 hydrogenation to dimethyl ether (DME) is a promising strategy to drive the current chemical industry towards a low-carbon scenario since DME can be used as an eco-friendly fuel as well as a platform molecule for chemical production. A Cu‒ZnO‒ZrO2/ferrierite (CZZ/FER) hybrid grain was recently proposed as a catalyst for CO2-to-DME one-pot conversion exhibiting high DME productivity thanks to the unique shape-selectivity offered by ferrierite zeolite. Nevertheless, such a catalyst deactivates but no direct evidence has been reported of activity loss over time. In this work, CZZ/FER catalysts with different acidity levels were characterized with the FTIR technique before and after reactions, aiming to give new insights about catalyst deactivation. Results show that activity loss can be related to both (i) copper particle sintering, which decreases CO2 activation towards methanol, and (ii) acidity loss due to H+/Cu2+ ion exchange.

Furfural is a platform bio-molecule for which is valuable to develop new green upgrading processes in biorefinery. We report here for the first time the high performance of Au/ZTC catalyst for the selective oxidation of furfural to 2-furoic acid, as first step to develop electrodes. The ordered nanostructure and high surface area of BEA structure replica ZTC allows to develop 3D-type electrodes. Au/ZTC catalyst shows higher performance than commercial Vulcan, used as reference conductive carbon in fuel cells. The weak acidity on ZTC avoids decarboxylation and esterification reactions, leading to about 90% of furfural conversion fully selectivity to 2-furoic acid.

The synthesis of dimethyl ether (DME) is an important step in the production of chemical intermediate because it is possible to prepare it by direct hydrogenation of CO2. This paper reports the effect of different zeolitic frameworks (such as: BEA, EUO, FER, MFI, MOR, MTW, TON) on methanol conversion, DME selectivity and catalyst deactivation. The effect of crystal size, Si/Al ratio and acidity of the investigated catalysts have been also studied. Finally, the kinetic parameters (such as: ∆H, ∆S and ∆G) have been evaluated together with pre-exponential factor and activation energy for catalysts with FER and MFI structure topology.

The aim of the paper is a comparison among three innovative process layouts for biomethane and power production from humid biomasses: anaerobic digestion (AD), supercritical water gasification integrated in a supercritical steam turbine stages (SCWG + SuST) and a technology that combines these two, AD plus SCWG and SuST. All the solutions were implemented in an ad hoc simulative tool of Aspen Hysis® v.7.0.1. Livestock sludge (LS) with an energy content up to 10 wt% (ashes free) was used as reference biomass to establish and compare the performance of any proposed process scheme. LS feedstocks introduced in the SCWG + SuST increased both biomethane production and power production of about 50 % compared to AD process that produces 25 Nm3/(day t) of pure biomethane. Combining both technologies, the digestate from AD outflow is feeding the SCWG + SuST process, there is an increase of 50 % of power generation with a production of biomethane of about 36 Nm3/(day t). Another advantage of the SCWG + SuST is that, set the fed, it is possible to reduce drastically the volume of the plant because the fermentation step, which usually corresponds to 15–30 days, is not required. Considering that although AD process is a simple and consolidated technology, it does not allow the total recovery of the organic compounds and requires long period for the biomass, the proposed innovative processes could offer new solutions for biomethane and power production. © 2016, Springer Science+Business Media Dordrecht.

[EN] In this study, the immobilization of Rhizomucor miehei lipase into hybrid nanospheres containing a liposomal core was reported. Organic internal liposomal enzyme phase was protected by inorganic silica matrix, obtained with and without surfactant, that stabilizes the internal organic phase and isolates and protects the bioactive molecules. The optimized heterogeneous catalyst thus prepared was used for enantioselective esterification of (R,S)-ibuprofen. The influence of several catalytic parameters on the activity of hybrid nanospheres (type of solvent, nature of the alcohol, reaction temperature, etc.,) was investigated. The heterogeneous biocatalysts best performed at 37 degrees C, using isooctane as solvent and 1-propanol as alcohol (with ester yield ranging between 78 and 93%). High activity and stability (up to nine reaction cycles) of enzyme-immobilized hybrid nanospheres, with respect to the free form, were observed. R. miehei lipase, both in its free and immobilized forms, reacts only with the S(+) enantiomer of (R,S)-ibuprofen, in all the tested reaction conditions. (C) 2015 Elsevier Ltd. All rights reserved., The authors thank the financial support from Consolider-Ingenio MULTICAT CSD2009-00050, MAT2014-52085-C2-1-P, and Severo Ochoa Excellence Program SEV-2012-0267.

The assessment of the catalytic performance of &ldquo, hybrid&rdquo, metal/zeolite catalysts (based on FER or MFI structure and CuZnZr metal complexes) in the methanol dehydration step to DME has been studied in this work. The results clearly show that there is an important effect of the interaction between metal and acid sites affecting the acid catalyst performances. Additionally, deactivation, studied by means of a Timo-on-Stream (TOS) test, was affected by the type of zeolite structure used for hybrid catalyst preparation. The decrease in DME selectivity can be attributed to the cooperation of metal and acid sites in the production of different compounds (mainly methyl formate and dimethoxy methane) converting methanol and DME. The presence of these compounds (indicating different reaction pathways active) was found to be dependent on the zeolite structure and on the type of co-precipitation medium (water or ethanol) used to prepare the hybrid catalyst.

International audience; Tailoring of physicochemical properties of synthetic zeolites is of paramount importance when these materials are applied as heterogenous catalysts. In this work, the effect of the synthesis system and in particular of the organic structure directing agent (OSDA) on acidity, crystal morphology, and catalytic behaviour of FER-type materials is studied. FER-type zeolites with similar Si/Al ratio and crystal size range 0.3–15 μm are synthesised by changing OSDA type or by adding surfactant. A crystallization kinetic analysis shows that the stability of the zeolitic phase strongly depends on the OSDA type. In particular, the crystallization time strongly affects the purity of the FER phase when tetrahydrofuran is used as a template. Furthermore, it is found that long amines as 1,8-diaminooctane can play a role of OSDA obtaining highly crystalline FER-type crystals and with a high Lewis acid sites concentration. FT-IR and 27Al-NMR analyses show that all of the synthesised samples possess different Lewis acid sites concentration associated with extra-framework Al–OH species that are not detected by NMR analysis. Catalytic tests in methanol-to-dimethyl ether reaction reveal that synthesised samples exhibit different catalytic behaviour. In particular, large (10–15 μm) FER-type catalyst synthesised with tetrahydrofuran suffer deactivation caused by a higher carbon deposit level. On the contrary, nano-sized FER-type crystals, prepared by using pyrrolidine as OSDA and a surfactant, exhibits high selectivity and considerable resistance to coke deposition.

The effect of channel-system of zeolite on methanol-to-DME reaction was studied. Results revealed that channels size and topology affect catalyst lifetime, type and location of coke precursors. FER and MFI showed the best resistance towards coke deposition, whilst fast deactivation was observed on MOR. Although the higher concentration and strength of acid sites, FER structure formed a lower coke amount, preferably located within the pores, while coke cluster deposited on the external surface of MOR. Analysis of acid sites distribution and strength was performed during deactivation–regeneration process. Coke location assessment was also supported by molecular simulations.