Hybrid Alginate-Brushite Beads Easily Catalyze the Knoevenagel Condensation On-Water

An innovative hybrid organic-inorganic material composed of alginate-brushite xerogel beads was successfully applied for the catalysis of the Knoevenagel condensation. The catalyst was derived from phosphated alginate xerogel microspheres formed from the ionotropic gelling effect of phosphated alginate. To this end, alginate was phosphated by the addition of diammonium hydrogen phosphate in a 1% w/w alginate gel. The phosphated alginate was subsequently precipitated by chelation of Ca²⁺ cations, generating a phosphated alginate hydrogel microsphere, which was washed and dried, forming hybrid organic-inorganic xerogel beads as a crystalline phosphate-rich mineral fraction covered by alginate. X-ray diffraction analysis revealed that the crystalline inorganic matrix of the material was composed predominantly of brushite. SEM analysis revealed plate-like, ribbon-like, or needle-like morphologies in the hybrid alginate-brushite beads. The hybrid material was tested as a catalyst for Knoevenagel condensation, which was performed ″on-water″ under mild conditions with aromatic aldehydes and activated methylene compounds, giving high yields (up to 97%). The reaction rate and product yield increased together with the reaction temperature for all reagents. The recyclable solid catalyst was effective for three runs, revealing the potential of the innovative hybrid catalyst as an eco-friendly heterogeneous catalyst.

A Short Review on the Utilization of Incense Sticks Ash as an Emerging and Overlooked Material for the Synthesis of Zeolites

The traditional hydrothermal synthesis methods are mainly performed under batch operation, which generally takes few days to weeks to yield a zeolite with the desired properties and structure. The zeolites are the backbone of the petrochemical and wastewater industries due to their importance. The commercial methods for zeolite synthesis are expensive, laborious and energy intensive. Among waste products, incense sticks ash is a compound of aluminosilicates and could act as a potential candidate for the synthesis of zeolites for daily needs in these industries. Incense sticks ash is the byproduct of religious places and houses and is rich in Ca, Mg, Al and Si. As a result, incense sticks ash can be proven to be a potential candidate for the formation of calcium-rich zeolites. The formation of zeolites from incense sticks ash is an economical, reliable and eco-friendly method. The application of incense sticks ash for zeolite synthesis can also minimize the problem related to its disposal in the water bodies, which will also minimize the solid waste in countries where it is considered sacred and generated in tons every day.

Efficient production of γ-aminobutyric acid by glutamate decarboxylase immobilized on an amphiphilic organic-inorganic hybrid porous material

A novel organic-inorganic hybrid porous material (KCS-2), containing both lipophilic and hydrophilic nanospaces to mimic a lipid bilayer, was utilized as an immobilization support and reaction accelerator for glutamate decarboxylase (GADβ). Upon evaluation of the adsorption of GADβ on KCS-2, the amount of immobilization was found to be approximately four times higher than that on non-porous silica, and a comparable adsorbability to mesoporous silica was observed. Following γ-aminobutyric acid (GABA) production by the decarboxylation of l-glutamic acid using these immobilized enzymes, the enzymatic activity of the GADβ-KCS-2 composite was found to be significantly higher than that of the free enzyme. In contrast, the activity of the more common GADβ-mesoporous silica composite decreased. Furthermore, the enzymatic activity of the GADβ-KCS-2 composite was superior to those of the un-immobilized free enzyme and the amorphous material itself over a wide temperature range. Thereby, these findings suggest that the amphiphilic nanospace of KCS-2 is suitable as a stable enzyme immobilization field and reaction acceleration field under such conditions. In addition, the durability of the immobilized enzyme was examined in terms of GABA production, with approximately 20% activity retention being observed after 10 cycles using KCS-2. Such durability was not observed for the non-porous silica material due to enzyme desorption.

Organoclays with carbosilane dendrimers containing ammonium or phosphonium groups

New composite materials could reveal attractive capabilities and favourable properties.

Reflections on the value of electron microscopy in the study of heterogeneous catalysts

Electron microscopy (EM) is arguably the single most powerful method of characterizing heterogeneous catalysts. Irrespective of whether they are bulk and multiphasic, or monophasic and monocrystalline, or nanocluster and even single-atom and on a support, their structures in atomic detail can be visualized in two or three dimensions, thanks to high-resolution instruments, with sub-Ångstrom spatial resolutions. Their topography, tomography, phase-purity, composition, as well as the bonding, and valence-states of their constituent atoms and ions and, in favourable circumstances, the short-range and long-range atomic order and dynamics of the catalytically active sites, can all be retrieved by the panoply of variants of modern EM. The latter embrace electron crystallography, rotation and precession electron diffraction, X-ray emission and high-resolution electron energy-loss spectra (EELS). Aberration-corrected (AC) transmission (TEM) and scanning transmission electron microscopy (STEM) have led to a revolution in structure determination. Environmental EM is already playing an increasing role in catalyst characterization, and new advances, involving special cells for the study of solid catalysts in contact with liquid reactants, have recently been deployed.

Recent advances in the textural characterization of hierarchically structured nanoporous materials

This review focuses on important aspects of applying physisorption for the pore structural characterization of hierarchical materials such as mesoporous zeolites.

Zeolite science and technology at Eni

This article reviews the results obtained in the synthesis, characterization and applications of zeolites and related microporous materials, focusing on catalytic processes developed in Eni research laboratories over the last 40 years.

Magnetic organic–inorganic nanocomposite with ultrathin imprinted polymers via an in situ surface-initiated approach for specific separation of chloramphenicol

An approach for preparing novel magnetic organic–inorganic nanocomposites with ultrathin imprinted polymers was reported, via an in situ surface-initiated grafting technique from magnetic halloysite nanotubes (MHNTs).