A Facile One-Step Synthesis of Polystyrene/Cellulose (PS@MFC) Biocomposites for the Preparation of Hybrid Water-Absorbing Sponge Materials

The elaboration of a low-cost and effective approach to synthesize hybrid composite materials based on the conventional thermoplastics and natural biopolymers is a sustainable alternative to the production of "traditional" plastics. Cellulose is one of the most abundant biopolymers. Its fibrils possess outstanding mechanical characteristics and, hence, attract considerable interest of researchers during recent decades. However, modification of the hydrophobic polymer matrix by cellulose fibrils is significantly complicated by the hydrophilic nature of the latter. In this study, we propose an effective and low-cost approach to the synthesis of polystyrene at the cellulose microfibrils composite material via the emulsion polymerization method. The obtained fibrous composite was comprehensively analyzed with FTIR spectroscopy, SEM, TGA, and DSC, and was further employed to produce sponge hybrid materials. We investigated the influence of the cellulose/polystyrene ratio on the density, porosity, pore volume, and water uptake of the obtained sponge materials. The sample containing 70 wt.% of cellulose demonstrated the best water absorption properties while preserving its shape, even after 24 h of floating on water. The produced sponge materials might be employed as sorption materials for the purification and desalination of waters of various origins, filtration, and collection of undesirable elements under specific industrial or natural conditions.

Natural aluminosilicate nanotubes loaded with RuCo as nanoreactors for Fischer-Tropsch synthesis

Following nanoarchitectural approach, mesoporous halloysite nanotubes with internal surface composed of alumina were loaded with 5-6 nm RuCo nanoparticles by sequential loading/reduction procedure. Ruthenium nanoclusters were loaded inside clay tube by microwave-assisted method followed by cobalt ions electrostatic attraction to ruthenium during wetness impregnation step. Developed nanoreactors with bimetallic RuCo nanoparticles were investigated as catalysts for the Fischer-Tropsch process. The catalyst with 14.3 wt.% of Co and 0.15 wt.% of Ru showed high activity (СO conversion reached 24.6%), low selectivity to methane (11.9%), CO₂ (0.3%), selectivity to C₅₊ hydrocarbons of 79.1% and chain growth index (α) = 0.853. Proposed nanoreactors showed better selectivity to target products combined with high activity in comparison to the similar bimetallic systems supported on synthetic porous materials. It was shown that reducing agent (NaBH₄ or H₂) used to obtain Ru nanoclusters at first synthesis step played a very important role in the reducibility and selectivity of resulting RuCo catalysts.

Formation of ruthenium nanoparticles inside aluminosilicate nanotubes and their catalytic activity in aromatics hydrogenation: the impact of complexing agents and reduction procedure

Ruthenium particles with size from 1 to 7 nm were formed by reduction of ruthenium complexes with urea, ethylenediaminetetraacetic acid, acetone azine, 1,2-Bis(2-furylmethylene)hydrazine) inside halloysite nanotubes. Catalysts of different morphology with Ru content from 0.75 to 0.93 %wt. were obtained using NaBH4 or H2 as reducing agents and tested in benzene hydrogenation as a model reaction. NaBH4 reduced catalysts showed similar catalytic activity with 100 % benzene conversion after 1.5 h. Reduction with H2 resulted in a decrease of catalytic activity for all samples. High benzene conversion was achieved only in the case of 1,2-Bis(2-furylmethylene)hydrazine and ethylenediaminetetraacetic acid. It was concluded that the thermal stability of complexing agents plays a key role in activity of catalysts reduced with H2.

Ruthenium-Loaded Halloysite Nanotubes as Mesocatalysts for Fischer-Tropsch Synthesis

Halloysite aluminosilicate nanotubes loaded with ruthenium particles were used as reactors for Fischer–Tropsch synthesis. To load ruthenium inside clay, selective modification of the external surface with ethylenediaminetetraacetic acid, urea, or acetone azine was performed. Reduction of materials in a flow of hydrogen at 400 °C resulted in catalysts loaded with 2 wt.% of 3.5 nm Ru particles, densely packed inside the tubes. Catalysts were characterized by N₂-adsorption, temperature-programmed desorption of ammonia, transmission electron microscopy, X-ray fluorescence, and X-ray diffraction analysis. We concluded that the total acidity and specific morphology of reactors were the major factors influencing activity and selectivity toward CH₄, C_2–4, and C₅₊ hydrocarbons in the Fischer–Tropsch process. Use of ethylenediaminetetraacetic acid for ruthenium binding gave a methanation catalyst with ca. 50% selectivity to methane and C_2–4. Urea-modified halloysite resulted in the Ru-nanoreactors with high selectivity to valuable C₅₊ hydrocarbons containing few olefins and a high number of heavy fractions (α = 0.87). Modification with acetone azine gave the slightly higher CO conversion rate close to 19% and highest selectivity in C₅₊ products. Using a halloysite tube with a 10–20-nm lumen decreased the diffusion limitation and helped to produce high-molecular-weight hydrocarbons. The extremely small C₂–C₄ fraction obtained from the urea- and azine-modified sample was not reachable for non-templated Ru-nanoparticles. Dense packing of Ru nanoparticles increased the contact time of olefins and their reabsorption, producing higher amounts of C₅₊ hydrocarbons. Loading of Ru inside the nanoclay increased the particle stability and prevented their aggregation under reaction conditions.

Clay Composites for Thermal Energy Storage: A Review

The development of novel materials and approaches for effective energy consumption and the employment of renewable energy sources is one of the current trends in modern material science. With this respect, the number of researches is focused on the effective harvesting and storage of solar energy for various applications. Phase change materials (PCMs) are known to be able to store thermal energy of the sunlight due to adsorption and release of latent heat through reversible phase transitions. Therefore, PCMs are promising as functional additives to construction materials and paints for advanced thermoregulation in building and industry. However, bare PCMs have limited practical applications. Organic PCMs like paraffins suffer from material leakage when undergoing in a liquid state while inorganic ones like salt hydrates lack long-term stability after multiple phase transitions. To avoid this, the loading of PCMs in porous matrices are intensively studied along with the thermal properties of the resulted composites. The loading of PCMs in microcontainers of natural porous or layered clay materials appears as a simple and cost-effective method of encapsulation significantly improving the shape and cyclic stability of PCMs. Additionally, the inclusion of functional clay containers into construction materials allows for improving their mechanical and flame-retardant properties. This article summarizes the recent progress in the preparation of composites based on PCM-loaded clay microcontainers along with their future perspectives as functional additives in thermo-regulating materials.

Templated self-assembly of ordered mesoporous silica on clay nanotubes

A novel self-assembly strategy of ordered silica arrays on halloysite clay nanotubes allows us to obtain mesoporous MCM-41 materials with enhanced thermal and mechanical stability. The formation of a structured mesoporous silica phase on halloysite is based on the assembly of cationic amphiphilic molecules onto a negative nanotube surface. The resulting MCM-41/halloysite composite demonstrated thermal and mechanical stability up to 1100 °C and 500 MPa showing great potential for application of mesoporous materials as industrial catalyst carriers and adsorbents.