Size and morphology controlled synthesis of gold nanoparticles in green solvent: Effect of reducing agents

The effect of reducing agents on the synthesis of Au(0) metallic nanoparticles (Au NPs) prepared in green solvent medium of β-d-glucose-water dispersions has been reported first. The different equivalent amounts of NaBH₄ and pH values adjusted by NaOH were tested for the reduction of Au salt (HAuCl₄·3H₂O (hydrogen tetrachloroaurate (III) trihydrate) to obtain Au NPs. The type and the amount of reducing agent and the pH of the solution affected the size and morphology of the NPs. Addition of 4 equivalents of NaBH₄ produced homogeneously dispersed 5.3 nm (σ = 0.7) diameter particles. Excess addition of NaBH₄ caused the NPs to settle down as the precipitate forming mesh or wire structure. When salt was reduced by the addition of NaOH (pH = 8.0) the particles were larger (14.2 nm) and less homogeneous (σ = 2.8). At pH = 12.2 the NPs settled at the bottom of the vial when preparation was left overnight. The wire and mesh like structures were obtained at higher pH = 12.2.     

Multi-mode hydrogen storage in nanocontainers

Hydrogen can be stored in containers or in materials (in molecular or atomic forms). The atomic form can further exist as multiple phases. Molecular hydrogen can be adsorbed on the surface or can be present inside the material. By invoking multiple modes of hydrogen storage, we establish a paradigm shift in the philosophy of hydrogen storage. Using a novel strategy of storage of molecular hydrogen in metal (Pd) nanocontainers, we observe that 18% hydrogen is in molecular form. Interestingly, this is achieved at 25 °C and 1 atm pressure; which is in contrast to storage in MOFs and carbonaceous materials like nanotubes. Enhancement in storage capacity as compared to Pd nanocrystals of the same mass is observed (36% increase at 1 atm & 25 °C), along with fast kinetics (0.5 wt% hydrogen absorption in 5 s). A new mechanism for hydrogen storage involving the dual catalytic role of Pd is established.     

Sulfur removal of gas oil using ultrasound-assisted catalytic oxidative process and study of its optimum conditions

Ultrasound-assisted oxidative desulfurization process (UAOD) was applied to reduce sulfur compounds of gas oil containing various types of sulfur content. The environmental regulation requires a very deep desulfurization to eliminate the sulfur compounds. UAOD is a promising technology with lower operating cost and higher safety and environmental protection. For the first time the typical phase transfer agent (tetraoctyl-ammonium-bromide) was replaced with isobutanol because using isobutanol is much more economical than TOAB, imposing no contamination. The reaction was carried out at optimal point with various temperatures, in single-, two- and three step-procedures, investigating the effect of gradual increase of H₂O₂ and TOAB being used instead of isobutanol. Total sulfur concentration in oil phase was analyzed by ASTM-D3120 method. The highest removal of about 90% for gas oil containing 9,500 mg/kg of sulfur was achieved in three-steps during 17 minutes of process at 62±2 °C when 180.3 mmol of H₂O₂ was used and extraction carried out by methanol.     

Supported Gold Nanoparticles Catalysts for Solvent-free Selective Oxidation of Benzylic Compounds into Ketones at 1 atm O2

Supported gold nanoparticles catalyst (Au/TiO₂) was investigated for the oxidation of benzylic compounds into corresponding ketones without any organic solvent at 1 atm O₂ under mild reaction conditions (≤100 °C). For instance, indan was oxidized with conversion of 46% and 1-indanone selectivity of 90% at 90 °C for 24 h. Effect of various reaction parameters viz., temperature, time, and effect of a range of supports was studied for the oxidation of indan. The conversion of indan and selectivity of 1-indanone over recycled catalyst remains almost same.     

A sustainable bio-adsorbent for thermal energy storage for space heating applications

Thermal energy storage is an emerging technology that allows the storage of heat when it is available, which can be used later. One of the available technologies for thermal energy storage is the adsorption of moisture from air by adsorbents. Several adsorbents have been studied in the literature for this application, but there is a need for a sustainable adsorbent that can be eco-friendly, cost effective, and available for scale-up for commercialization of the technology. The current paper focused on the synthesis of a flax shives-based composite (equal weight percent of flax shives and salt hydrates) prepared by the impregnation method and its application in thermal energy storage. The composite showed durability, stability, and reasonable energy storage density with a very low cost per unit of energy. The structural characterization of the hybrid was performed by scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX). The thermal energy storage density, as well as the charging/discharging characteristics were measured using a laboratory-scale thermal energy storage apparatus. The flax/CaCl₂/LiCl hybrid showed reasonable energy storage density at 74 kWh/m³ for 50% inlet relative humidity after regeneration at 120°C. Although the energy storage density was not high, the flax/CaCl₂ composite was found to be the most cost-effective material, as it showed the lowest cost per energy stored at 0.98 CAD/kWh at 50% relative humidity (RH) after regeneration at 120°C.