Gold supported on iron oxy-hydroxides: a versatile tool for the synthesis of fine chemicals

A comprehensive overview on gold supported on iron oxy-hydroxides as tool for the synthesis of fine chemicals is given. We will discuss on the catalytic activity of gold supported on iron oxy-hydroxides in several reactions of potential industrial interest, comprising the selective oxidation of primary alcohol to aldehyde, the selective reduction of α,s unsaturated aldehydes and ketones to the corresponding a,b unsaturated alcohols. Furthermore, a significant application of gold supported on iron oxy-hydroxides is the direct synthesis of hydrogen peroxide from H2 and O2. The versatility showed by Au supported on oxy-hydroxides catalysts is an aspect of great importance for industrial applications

Preparation, processing and analysis of physical properties of calcium ferrite-CNTs/PET nano-composite

The present work is focused on the preparation of composites based on Poly(ethylene terephthalate) (PET) and novel nano-hybrid filler composed of Calcium Ferrite (CF)-Carbon Nanotubes (CNTs), obtained by direct growth of CNTs on CF based iron catalysts. The carbon content in the hybrid filler was 76 wt%. Composites loaded with 1.0, 1.5, 2.0, 3.0 wt% of filler were obtained by melt compounding and processed by thin-wall injection molding. Unfilled Poly(ethylene terephthalate) was processed using the same techniques. Structural characterization and physical properties (thermal, mechanical and electrical) were analyzed and correlated to the hybrid filler loading, and to the percentage of carbon nanotubes

Synthetic strategies for the enhancement of Mg(OH)2 thermochemical performances as heat storage material

Abstract This work deals with the study of influence of multi walled carbon nanotubes (CNTs) characteristics on thermochemical performance of hybrid materials based on Mg(OH) 2 (M) as heat storage medium. Two different functionalized CNTs samples are investigated, separated curly tubes (SN) and bundles of straight nanotubes (BN). Hybrids were synthesized by reverse deposition precipitation method and their structure was characterized by X-ray analysis and scanning electron microscopy. The heat storage performance was studied through a thermogravimetric apparatus, simulating heat storage/release cycles. It is demonstrated that separated CNTs owning mainly carboxylic groups increase the interaction with precipitated magnesium hydroxide, improving the reacted fraction during dehydration/hydration cycle. In terms of dehydration/hydration conversion the samples' rank is SN-M>Mg(OH) 2 >BN-M. SN-M exhibits higher heat storage/output capacity (~1250 kJ/kg Mg(OH)2 , ~350 MJ/m 3 )

Morphological and Structural Evaluation of Hydration/Dehydration Stages of MgSO4 Filled Composite Silicone Foam for Thermal Energy Storage Applications

Salt hydrates, such as MgSO4·7H2O, are considered attractive materials for thermal energy storage, thanks to their high theoretical storage density. However, pure salt hydrates present some challenges in real application due to agglomeration, corrosion and swelling problems during hydration/dehydration cycles. In order to overcome these limitations, a composite material based on silicone vapor-permeable foam filled with the salt hydrate is here presented. For its characterization, a real-time in situ environmental scanning electron microscopy (ESEM) investigation was carried out in controlled temperature and humidity conditions. The specific set-up was proposed as an innovative method in order to evaluate the morphological evolution of the composite material during the hydrating and dehydrating stages of the salt. The results evidenced an effective micro-thermal stability of the material. Furthermore, dehydration thermogravimetric/differential scanning calorimetric (TG/DSC) analysis confirmed the improved reactivity of the realized composite foam compared to pure MgSO4·7H2O.This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31). This work was partially supported by ICREA under the ICREA Academia program

Influence of the Cobalt Phase on the Highly Efficient Growth of MWNTs

In this work, the influence of the cobalt phase on the growth of carbon nanotubes by the catalytic chemical vapour deposition of CH4 with catalysts containing Co, Mo and Mg is investigated. To this end, the catalytic behaviour of physically mixed CoO/MgO+MgMoO4 and CoMoO4+MgMoO4 is studied. The results obtained show that CoMoO4+MgMoO4 allows for the attainment of the highest CNT yield (2407 wt % against 1296 wt %). Its higher activity is ascribed to the greater formation of active sites that, in light of current assessments, are constituted by metallic cobalt adjacent to Mo2C, and the huge exfoliation of the catalyst, which contributes towards enhancing their exposure

On the CVD Growth of C Nanotubes Over Fe-Loaded Montmorillonite Catalysts

The synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD) of isobutane (i‐C4H10) over sodium‐exchanged K10‐montmorillonite based iron‐ catalysts is investigated. By studying the influence of iron‐addition (5–25wt%) on the catalyst performances, at 700 °C, an empirical relationship is derived relating the mass of CNTs synthesized with the exposed surface of loaded iron, as resulting from simultaneous change of number, size and dispersion of Fe‐nanoparticles available for the growth

Do Nanotubes Follow an Amorphization Trajectory as Other Nanocarbons Do?

Various typologies of nanocarbons are considered, including crystalline graphite, amorphous activated carbon, and a large variety of multiwall carbon nanotubes (laboratory-prepared and commercially available, pristine and heat-treated), featured by different purity degree (81.7–99.7 wt %), crystalline quality (amorphous fraction: 0–5 wt %), size (outer diameter: 5–100 nm), and morphology. From the comparative discussion of the results of their systematic investigation by Raman spectroscopy, kinetic thermal analysis, and complementary techniques, the existence of a sharp correlation emerges between the strength of C bonding, as measured by the wavenumber position of the G-band in Raman spectra, and the oxidative resistance of the samples, as monitored by the maximum oxidation-rate temperature. A three-stage model is proposed to account for the effects associated with the increasing localization of states due to the introduction of curvature and lattice defects, accompanying the evolution from crystalline graphite to highly crystallized nanotubes, and from poorly crystallized nanotubes to amorphous activated carbon

Thermo-Physical Characterization of Carbon Nanotube Composite Foam for Oil Recovery Applications

To meet the increasing demands for effective cleanup technologies to deal with the oil spill accidents that significantly affect the ecological and environmental systems, promising composite materials based on carbon nanotubes containing silicone foams were investigated. Pump oil, kerosene, and virgin naphtha had been used to assess, during sorption tests, foams behavior. Test results highlighted the advantage of the hydrophobic and oleophilic behavior of carbon nanotubes, and their high mechanical strength for oil spill recovery application was studied. In order to better relate the property-structure relationship for this class of materials, the role and influence of functionalized nanotubes on thermo-physical and morphological characteristics of the foams had been evaluated. The results showed how the pristine nanotubes fillers, despite functionalized ones, led to optimal composite foam performances with high hydrophobic (62 mg g−1) and oleophilic (6830 mg g−1 in kerosene oil) characteristics. The evidenced high oil selectivity was a relevant key point in order to consider the suitable material for oil spill recovery applications. Eventually, the proposed configuration exhibited the best thermo-physical performances and high reusability, leading to the optimal cost-benefits option