Development of In–Cu binary oxide catalysts for hydrogenating CO2 via thermocatalytic and electrocatalytic routes

Carbon dioxide (CO2) hydrogenation to obtain valuable chemicals and fuels via thermocatalysis or electrocatalysis is a promising and sustainable method for CO2 utilization. Here, binary In-Cu oxide co-precipitated materials were investigated to evaluate the catalytic performance in the mentioned conversion processes. The In-rich binary material exhibits remarkable selectivity (>60%) to methanol along with high activity for CO2 conversion (>2%) at 21 bar and 300 °C, achieving a productivity of about 265 mgMeOH h−1 gIn2O3−1, which is almost 3 times higher than that of the bare In2O3 catalyst. CO2-temperature programmed desorption revealed that the basicity of the In-rich catalyst remains constant between the calcined and spent samples, so the capacity to adsorb CO2 does not vary when the catalyst is exposed to the reaction atmosphere. Such a catalyst was demonstrated to be active for formate production in the electrochemical process as the main product. Ex situ characterization after testing proved that the In2O3 phase was the active site of methanol synthesis during CO2 hydrogenation at high temperatures and pressures. In contrast, depending on the cell configuration, different indium interfaces were stabilized at the electrocatalyst surface under ambient conditions. It is envisioned that the co-presence of In0, In2O3, and In(OH)3 phases increases the local amount of *CO intermediates, promoting the formation of more reduced products, such as ethanol and 2-propanol, through the *CO dimerization reaction in the electrochemical process. These findings highlight the potential of nonreducible hydroxides as promoters in the electrochemical CO2 reduction process

Advances and challenges in zeolite synthesis and catalysis

Zeolites are the most important heterogeneous catalysts in industrial applications and number of the processes catalyzed by them continuously increases. In this short overview we address key issues and challenges of the synthesis of zeolites in particular focusing on novel types of zeolites like two-dimensional zeolites (layered materials), manipulation with them using novel ADOR protocol, hierarchical systems and organozeolites. Some challenges in potential applications of these types of zeolites are also discussed

Swelling and interlayer chemistry of layered MWW zeolites MCM-22 and MCM-56 with high Al content

Swelling of layered zeolite precursors such as MCM-22P with cationic surfactants at high pH is the key step in their subsequent conversion into expanded lamellar materials by pillaring and delamination. Increasing Al content in the precursors can yield more active catalysts but affects their swelling efficiency especially at lower temperature, which was reported as favorable for layer structure preservation with more siliceous MCM-22P. The latter, a (multi)layered precursor, was investigated in this work and showed inadequate swelling of its high-Al representatives with organic hydroxide/surfactant mixtures and especially when NaOH is the source of high pH. In contrast, the unilamellar MCM-56 was found to swell readily at room temperature with various hydroxide sources, and notably with NaOH, in combination with the surfactant. The observed differences between MCM-56 and MCM-22P, especially with regard to swelling with NaOH, are attributed to the fundamentally different nature of their layer surface and interlayer linking. The former has surface terminated with ≡Al—OH–Na+ moieties, producing weak connections, instead of the pyramidal ≡Si—OHs populating the MCM-22P surface and forming interlayer H-bonding. The methods used for validating the swelling and product characterization included XRD, nitrogen sorption, IR spectroscopy and TEM imaging. The microscopy confirmed, by direct visualization, the extensive but not complete swelling of MCM-56, which can be enhanced by treatment at higher temperature

The state of nickel in spent Fluid Catalytic Cracking catalysts

The speciation of Ni in spent Fluid Catalytic Cracking catalysts is studied. Carefully performed XRD analyses with NiO/SiO2 samples used as calibration standards, demonstrate that the presence of NiO as a separate phase is reliably detected also for NiO concentration close to 0.1 wt% (1000 ppmw). Actually, both on real spent FCC catalysts (ECAT's) and on artificially contaminated industrial FCC catalysts, NiO is not detectable as a separate phase, even after contamination of the order of 15,000 ppmw of Ni. SEM-EDS experiments provide evidence of a largely preferential location of Ni on alumina particles present in the FCC catalyst mixture, thus acting as "nickel traps". XRD, UV-vis and TPR data confirm that Ni deposits on alumina particles forming a hardly reducible surface and subsurface layer, giving rise to a solid whose composition is NixAl2O3+x with x << 0.25. As a result of this, the formation of extended Ni metal particles in the raiser reactor is avoided, being their unwanted dehydrogenation activity essentially eliminated. The absence of bulk NiO in the spent FCC catalysts (at least when Ni content is in the range 2000-10,000 ppmw) allows the classification of this material as a non-hazardous waste. (C) 2014 Elsevier B.V. All rights reserved

Flexible Structure of a Thermally Stable Hybrid Aluminosilicate Built with Only the Three-Ring Unit

Organic–inorganic aluminosilicate hybrids are an attractive new class of materials that add organic functionalities to conventional properties of solid inorganic catalysts. ECS-17, a novel crystalline hybrid, was synthesized using 1,4-bis-(triethoxysilyl)-benzene as the sole silicon source. Its structure was solved by direct methods starting from high-resolution synchrotron X-ray diffraction data and is composed of inorganic layers, characterized by 10 rings, held together by phenylene rings. ECS-17 is the first aluminosilicate built from only the three-ring secondary building unit. This new material shows intriguing reversible collapsibility upon dehydration/rehydration. Mild thermal treatment under vacuum causes its crystalline structure to collapse due to facile elimination of the water molecules around the cations. Successive exposure to ambient atmospheric moisture gives back the hydrated crystalline form. ECS-17 shows remarkably high thermal stability for a hybrid, being stable up to 450 °C under vacuum and breaking down at 350 °C in air. Structural, thermal, and optical properties were examined by X-ray powder diffraction, thermogravimetric analysis, nuclear magnetic resonance, and ultraviolet–visible-near-infrared reflectance and fluorescence spectroscopies

The role of boric acid in the synthesis of Eni Carbon Silicates

The influence of H3BO3 on the crystallization of hybrid organic–inorganic aluminosilicates denoted as Eni Carbon Silicates (ECS's) was investigated. Syntheses were carried out at 100 °C under different experimental conditions, using bridged silsesquioxanes of general formula (EtO)3Si–R–Si(OEt)3 (R = –C6H4– (BTEB), –C10H6– (BTEN) and –C6H4–C6H4– (BTEBP)), in the presence of equimolar concentrations of NaAlO2 and H3BO3. The study, involving the synthesis of three different but structurally related phases (ECS-14 from BTEB, ECS-13 here described for the first time from BTEN, and ECS-5 from BTEBP), confirmed a catalytic role for H3BO3 which in general increased the crystallization rate and improved the product quality in terms of amount of crystallized phase (crystallinity), size of the crystallites and phase purity, while it was weakly incorporated in trace amounts in the framework of ECS's

Eni Carbon Silicates: Innovative Hybrid Materials for Room-Temperature Gas Sensing

The purpose of this work was to satisfy both materials and technological sciences, on the one hand implementing innovative hybrid materials referred to as ECS (Eni Carbon Silicate) in gas sensors manufacturing, and on the other hand verifying their possible operation at room temperature as a technological progress. The ECS-14 and ECS-13 phases were employed as functional materials for films deposited by drop coating onto alumina substrates. Room-temperature gas tests were performed to study their potential sensing properties. In humidity conditions, the ECS-14 based sensor showed outstanding performance and a complete calibration vs. moisture concentration was obtained

Crystalline Microporous Organo-Silicates with Reversed Functionalities of the Organic and Inorganic Components for Room-Temperature Sensing of Humidity

deepened investigation on an innovative organic−inorganic hybrid material, referred to as ECS-14 (where ECS = Eni carbon silicates), revealed the possibility to use them as gas sensors. Indeed, among ECS phases, the crystalline state and the hexagonal microplateletlike morphology characteristic of ECS-14 seemed favorable properties to obtain continuous and uniform films. ECS-14 phase was used as functional material in screen-printable compositions and was thus deposited by drop coating for morphological, structural, thermal, and electrical characterizations. Possible operation at room temperature was investigated as technological progress, offering intrinsic safety in sensors working in harsh or industrial environments and avoiding high power consumption of most common sensors based on metal oxide semiconductors. Electrical characterization of the sensors based on ECS-14 versus concentrations of gaseous analytes gave significant results at room temperature in the presence of humidity, thereby demonstrating fundamental properties for a good quality sensor (speed, reversibility, and selectivity) that make them competitive with respect to systems currently in use. Remarkably, we observed functionality reversal of the organic and inorganic components; that is, in contrast to other hybrids, for ECS-14 the functional site has been ascribed to the inorganic phase while the organic component provided structural stability to the material. The sensing mechanism for humidity was also investigated

Eni Carbon Silicates: innovative hybrid sensing materials for room-temperature humidity detection

The purpose of this work was to satisfy both materials and technological sciences, on the one hand implementing innovative hybrid materials referred to as ECS (Eni Carbon Silicate) in gas sensors manufacturing, and on the other hand verifying their possible operation at room temperature as a technological progress. The ECS-14 and ECS-13 phases were employed as functional materials for films deposited by drop coating onto alumina substrates. Room-temperature gas tests were performed to study their potential sensing properties. In humidity conditions, the ECS-14 based sensor showed outstanding performance and a complete calibration vs. moisture concentration was obtained