Aluminosilicate Research Articles

Use of metakaolins from Eseka and Dibamba‐Cameroon as an optimization additive of CEM I Portland cement mortar

AbstractThe present study deals with two kaolins from Eseka and Dibamba‐Cameroon to determine their potential suitability as additive of CEM I 42.5R and to optimize the properties of cement in the sense to promote low‐carbon cement. X‐ray diffractometry was used to establish the mineralogical composition of two kaolins. X‐ray fluorescence was carried out to determine the chemical composition of kaolins and cement. Fine metakaolin powders obtained at 700°C were used as additive in CEM I 42.5R. Furthermore, consistency, setting time, water absorption, compressive and flexural test, and shrinkage test were evaluated. Scanning electron microscopy analysis was carried out to evaluate the microstructure variation. The substitution of CEM I with metakaolin resulted in a considerable increase in compressive and flexural strength from days 7 to 28 at optimum value. The compressive and flexural strengths at 28 days at optimum value of metakaolin increase to 52% and 44%, respectively, explaining the equilibrium oxides in the cement. The maximum values of strength with 20 wt.% MK1 and 30 wt.% MK2 at 7, 14, and 28 days appear in both cases when the ratio of SiO2/Al2O3 is between 2.8 and 2.9. The silica modulus and alumina modulus of cement–metakaolin improved when metakaolin was added. The properties of cement were optimized with a 52% increase in compressive strength at 28 days.

Effect of Potassium on the Co-Combustion Process of Coal Slime and Corn Stover

In this study, the combined combustion characteristics and gaseous product emissions of coal slime and corn stover were compared at different blending ratios. The TG-DTG curves indicate that the optimal performance is achieved when the corn straw blending ratio is 20%. Furthermore, the TG-FTIR coupling results demonstrated an increase in gas species as the blending ratio increased. The composition analysis of ash samples formed at various combustion temperatures using XRD and XRF indicated that a portion of KCl in the fuel was released as volatile matter, while another part reacted with Al2O3 and SiO2 components in the slime to form silica–aluminate compounds and other substances. Notably, interactions between the components of slime and potassium elements in corn stover primarily occurred within the temperature range of 800–1000 °C. These findings contribute to a comprehensive understanding of biomass and coal co-firing combustion chemistry, offering potential applications for enhancing energy efficiency and reducing emissions in industrial processes.

PROSPECTS FOR USING A COBALT CATALYST FOR FISHER-TROPSCH SYNTHESIS BASED ON SYNTHETIC SILICA ALUMINA

The possibility of the use of commercially available silica-alumina hydrate Siral-40, containing 40 wt.% of SiO2, in the composition of a composite cobalt Fischer–Tropsch synthesis (FTS) catalyst was studied. The use of silica aluminas may become a new promising direction in the development of catalysts for a shortened technological chain based on the use of bifunctional catalysts that make it possible to eliminate the hydroprocessing stage. In addition, such catalysts can be useful for expanding the range of products obtained, including those unconventional for single-reactor Fischer–Tropsch synthesis. The initial silica alumina powder was pretreated in air flow at different temperatures to adjust the concentration of acid cites on its surface. The initial and calcined powders were studied using X-ray diffraction analysis, IR spectroscopy and sorption methods. The catalysts were investigated by diffraction and sorption methods. It has been shown that an increase in the calcination temperature of the initial Siral-40 powder leads to a decrease in the specific surface area and pore volume of catalysts based on it, with temperatures above 900 °C having the greatest effect. The synthesized catalysts were active in FTS, and the composition of the obtained C5+ hydrocarbons depended more on the properties of the Siral-40 powder than the catalytic performance. The composition of C5+ hydrocarbons, obtained in the presence of all investigated catalysts contained at least 60% of diesel fraction and more than 30% of wide base oil fraction. Thus, synthetic amorphous silica aluminas are a promising component for new Fischer–Tropsch synthesis catalysts, which make it possible to obtain a wide range of products without the use of a deep hydroprocessing stage in the technological chain. For citation: Sineva L.V., Asalieva E.Yu., Gryaznov K.O., Mordkovich V.Z. Prospects for using a cobalt catalyst for Fisher-Tropsch synthesis based on synthetic silica alumina. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 88-98. DOI: 10.6060/ivkkt.20246710.7y.

Regeneration and Single Stage Batch Adsorber Design for Efficient Basic Blue-41 Dye Removal by Porous Clay Heterostructures Prepared from Al13 Montmorillonite and Pillared Derivatives.

Porous clay heterostructures are a hybrid precursor between the pillaring process and organoclays. In this study, the organoclay was substituted by an aluminium intercalated species clay or pillared alumina clays. A porous clay heterostructure was successfully achieved from an aluminium intercalated species clay, due to the easy exchange of the aluminium species by the cosurfactant and silica species. However, using alumina pillared clays, the porous clay heterostructures were not formed; the alumina species were strongly attached to clay sheets which made difficult their exchange with cosurfactant molecules. In this case, the silica species were polymerized and decorated the surface of the used materials as indicated by different characterization techniques. The specific surface area of the porous clay heterostructure material reached 880 m2/g, and total pore volume of 0.258 cc/g, while the decorated silica alumina pillared clays exhibited lower specific surface area values of 244-440 m2/g and total pore volume of 0.315 to 0.157 cc/g. The potential of the synthesized materials was evaluated as a basic blue-41 dye removal agent. Porous clay heterostructure material has a removal capacity of 279 mg/g; while the other materials exhibited lower removal capacities between 75 mg/g and 165 mg/g. The used regeneration method was related to the acidity of the studied materials. The acidity of the materials possessed an impact on the adopted regeneration procedure in this study, the removal efficiency was maintained at 80% of the original performance after three successive regeneration cycles for the porous clay heterostructure. The Langmuir isotherm characteristics were used to propose a single-stage batch design. Porous clay heterostructures with a higher removal capacity resulted in a decrease in the quantities needed to achieve the target removal percentage of the BB-41 dye from an aqueous solution.

Carbon sequestration in earth-based alkali-activated mortar: phase changes and performance after natural exposure

This research investigates the effect of carbon sequestration via accelerated carbon curing (ACC) in alkali-activated earth-based alkali-activated mortar (25S-AAM) on the long-term engineering performance, chemical bonding and microstructure. The addition of clay accelerates hydration kinetics and promotes the formation of more cross-linked calcium–(sodium) alumino silicate hydrates (N-A-S-H and C-(N)-A-S-H). This contributes to early strength and a 25% reduction in total shrinkage after 60 days. Although ACC promotes higher carbon sequestration and increases 1-d compressive strength by 13%, it leads to severe decalcification of 25S-AAM after 365 days of natural exposure, resulting in coarsening of the pore structure in the mesoporous size range of 10–100 nm. Due to a relatively low Ca/Si ratio, 25S-AAM is more adversely affected by natural carbonation during the 365-d exposure period than the control (without clay). In summary, ACC is not recommended for earth-based AAM products especially if they are applied for outdoor constructions.

Propylene oligomerization over SiO2-overcoated oxides

Catalytic oligomerization of light olefins is an important CC coupling strategy that can be used to produce high-value transportation fuels and chemicals from shale gas and biomass feedstocks. In this work, vapor-phase propylene oligomerization was studied over a series of overcoated SiO2-MOx materials, whose acid site densities and strengths are tunable by the amount of SiO2 deposition and the nature of the core oxide. These materials contain acid sites only on particle external surfaces, limiting pore diffusion artifacts. SiO2-MOx materials were prepared by depositing stoichiometric amounts of tetraethyl orthosilicate (TEOS) onto Al2O3, anatase TiO2, Nb2O5, and ZrO2. Compared to the unmodified oxides, which are poor propylene oligomerization catalysts, the SiO2-MOx materials exhibit moderate activity with Al2O3, TiO2, and Nb2O5 core materials performing better than commercial amorphous silica alumina (ASA) on a surface area basis. The activity of the materials appears to be primarily driven by their Brønsted acid strength as measured by 31P TMPO MAS NMR with the rates ranked in order SiO2/Al2O3 > SiO2/TiO2 ≈ SiO2/Nb2O5 > SiO2/ZrO2. This study shows that SiO2-overcoated materials are a tunable class of materials that are active for vapor-phase propylene oligomerization.

Effect of heat‐treatment on the microstructure and room‐temperature mechanical properties of alumina–silica fiber

AbstractEffect of heat‐treatment (900°C∼1600°C) on the microstructure and mechanical properties of alumina–silica fiber was well investigated. The results indicated that the recommended temperature threshold for the use of the alumina–silica fiber was not more than 1100°C to maintain its mechanical integrity. Above this temperature, the elastic modulus of the fibers increased, and the tensile strength significantly decreased, mainly because of the transformation of the structure from γ‐Al2O3 and amorphous SiO2 to mullite. The tensile strength of the fiber was 0.87 GPa at 1200°C. Compared to the as‐received fibers, the strength retention was only 63.50%. Moreover, as revealed by Weibull statistical analysis, the formation of more defects due to mullite phase transformation resulted in higher dispersion of the fiber tensile strength. However, at this temperature, the Young's modulus of the fiber increased from the initial value 146.24 ± 5.19 GPa to 183.06 ± 5.83 GPa. Finally, the rate of mullite reaction was seen to be strongly temperature dependent. The higher the heat‐treated temperature, the shorter the time required for γ‐Al2O3 and amorphous SiO2 to completely transform into mullite grains.

Corrosion behavior of co-gasification slag of furfural residue and coal on alumina-silica refractories

Gasification of furfural residue with coal can realize its efficient and clean utilization. But the high alkali metal content in furfural slag is easy to cause the corrosion of gasifier refractory. Two gasification coals with different silica alumina ratio and a furfural residue were selected in the study. The effects of furfural residue additions on corrosion of silica brick, corundum brick, high alumina brick and mullite brick were investigated by using XRD, SEM-EDS and Factsage Software, and the corrosion mechanism was analyzed. With increasing furfural residue addition, the permeability of the slags to high-aluminium-bearing refractories first decreases and then increases, while the permeability on silica brick shows a slight decrease trend. Leucite (KAlSi2O6) with high-melting temperature is generated from the reaction of K2O and SiO2 in slag with Al2O3 in refractories after furfural residue is added, which hinders the infiltration of slag in refractories. Kaliophilite (KAlSiO4) of low-melting point is formed when K2O content increases, and this contributes to the infiltration of slag in refractories. The acid-base reaction between slag and silica brick is distinctly occurred, more slag reacts with SiO2 in the silicon brick, resulting in a decrease in the amount of slag infiltrating into the silicon brick as furfural residue is added. The corrosion of silica brick is mainly caused by the acid-base reaction, while the corrosion of three alumina based refractory bricks of corundum, mullite and high alumina brick is determined by slag infiltration. A linear correlation between the percolation rate and slag viscosity is established, the slag permeability increases with decreasing viscosity, resulting in stronger permeability for the high Si/Al ratio slag with lower viscosity.

Furanic jet fuels – Water-free aldol condensation of furfural and cyclopentanone

A method for the water-free, large-scale synthesis of bio-jet fuel precursors, distinct from traditional fossil-based sources, is introduced. This approach involves the aldol condensation of furfural with cyclopentanone, producing C10-C15 fuel precursors eligible for further hydrodeoxygenation to high-performance diesel and jet fuel hydrocarbons. In the context of process integration, aldol condensation reactions were conducted under water-free conditions, utilizing excess furfural as the solvent. Evaluation of various commercial catalysts confirmed the feasibility of running in excess furfural. Both basic and acidic catalysts demonstrated significant activity, with CaO and amorphous silica-alumina achieving ≥80 mol% conversion of cyclopentanone and yielding ≥80 mol% selectivity towards the desired fuel components within 5 h of reaction. However, an overlooked aspect is the notable formation of undesired heavy side products. Observations indicated that the high furfural concentration, combined with the use of strong acidic catalysts, were the primary cause of heavy side product formation. The strong base catalyst, CaO, significantly reduced the formation of these oligomers, but did not appear to stop it completely. Interestingly, water content did not appear to play a major role in byproduct selectivity. To further suppress the formation of oligomers, the use of process-owned intermediates as solvents is proposed.

Sodium alumino silicate (SAS) neem nanocomposite – A novel seed storage tool against toxigenic Aspergillus flavus causing deterimental effects on seeds health and quality of rice

Infection of rice grains in the field during harvest and storage by Aspergillus flavus, a toxigenic mold causes significant losses to market acceptability of seeds due to its detrimental effects on seed health and quality parameters. Production of aflatoxin by A. flavus interferes with physiological factors affecting the quality of seeds during storage in addition to nutritional losses to the grains. Chemical seed treatments are generally not recommended during storage due to their adverse effects on seed germination and vigor. Leaves of the neem tree (Azadirachta indica) are well known for antifungal properties against phytopathogenic fungi such as A. flavus. The paper presents the effect of neem leaf extract adsorbed onto sodium alumino-silicate (SAS) nanoparticles against A. flavus in rice seeds during storage. SAS-Neem nanocomposite, a novel unexplored seed storage material against toxigenic A. flavus, was synthesized for augmented antitoxin and seed invigorating potential. The nanocomposite was characterized using an array of microscopic and spectroscopic methods to evaluate the adsorption of neem leaf extract components on SAS nanoparticles. The antifungal mechanism of the nanocomposite was evaluated via scanning electron microscope, phase contrast, and fluorescence microscopy. The toxin analysis of pathogen-inoculated seeds was carried out at monthly intervals for 6 months during storage of two rice varieties, i.e. PR114 and Pusa-Basmati 1121. The results indicated that the nSAS-Neem composite used as seed coating material maintained significantly higher seed germination (86.23 and 81.49%) and minimized seed rot (6.70 and 5.30%, respectively) in the two varieties under study than the control after 6 months of storage. There was a notable decrease in toxin concentration from 20.58 to 11.19 μg/kg and 19.16 to 12.58 μg/kg in seeds of the two varieties i.e. PR114 and Pusa Basmati 1121, respectively. The nano-composite proved effective against toxigenic A. flavus during seed storage of rice without compromising the seed quality parameters.

Micro-Nano Dual-Scale Coatings Prepared by Suspension Precursor Plasma Spraying for Resisting Molten Silicate Deposit

Yb-doped Y2O3 stabilized ZrO2 (YbYSZ) coatings, developed through solution precursor plasma spraying (SPPS), are engineered to resist calcium–magnesium–alumino–silicate (CMAS) infiltration by leveraging their unique micro-nano structures. This provides superior anti-wetting properties, crucial for preventing CMAS penetration at high temperatures. The investigation focused on the structural and compositional changes in YbYSZ-SPPS coatings subjected to prolonged thermal exposure at 1300 °C. Results indicate that while the coatings undergo significant sintering, leading to densification and microstructural evolution, the elemental composition and phase stability remain largely intact after up to 8 h of heat treatment. Despite some reduction in CMAS resistance, the coatings maintained their overall protective performance, demonstrating the potential of SPPS coatings for long-term use in high-temperature environments where CMAS infiltration is a concern. These findings contribute to the development of more durable TBCs for advanced thermal protection applications.

Influence of support on Rh-Co bimetallic catalysts for ethylene hydroformylation

Bimetallic Rh- and Co-based catalysts are promising materials for the heterogenous ethylene hydroformylation reaction. Here, the influence of a mesoporous silica (SBA-15) support on Rh and Co bimetallic interactions was investigated through a comparison with silica gel and gamma-alumina supports. The bimetallic catalyst supported on mesoporous silica (RhCo3/SBA-15) showed the best C3 oxygenate yield among the three bimetallic catalysts. In-situ vibrational studies suggested moderate binding of the gem-dicarbonyl and Rh(CO)(C2H4) intermediates due to this bimetallic interaction that led to improved hydroformylation performance. Kinetic studies revealed a lower hydroformylation barrier for the bimetallic compared to a Rh monometallic catalyst, and in-situ X-ray absorption spectroscopy investigations showed clear Rh-Co alloy formation on RhCo3/SBA-15. The bimetallic enhancement effect from the interaction with the mesoporous silica support shown here can be further optimized to design olefin hydroformylation catalysts.

Effect of acidity of solid acid catalysts during non-oxidative thermal decomposition of LDPE

AbstractThermal decomposition of low-density polyethylene (LDPE) was monitored by thermogravimetry under N2 atmosphere in the presence of solid acid catalysts such as alumina (α-Al2O3, γ-Al2O3), crystalline silica-alumina (SA, molar ratio of Si/Al = 0.19) and amorphous silica-alumina catalysts (ASA, molar ratio of Si/Al = 4.9). Crystal structure and surface area of solid acid catalysts were measured by XRD and BET, respectively. The strength and distribution of acid sites of solid acid catalysts were estimated by NH3-TPD. It was observed that total acidity strength is in the order of ASA (1.77 μmmol NH3/g) > AS (1.42 μmol NH3/g) > γ-Al2O3 (1.06 μmol NH3/g) > α-Al2O3 (0.06 μmol NH3/g). Thermal degradation behavior of LDPE with and without solid acid catalyst was monitored by TGA, where heating rates (β) of 5, 10, and 20 °C/min were employed under an inert atmosphere, and their activation energies (Ea), onset temperatures (Tinitial), decomposition temperatures (Tdecomp) were calculated and compared. The activation energy (Ea) was evaluated using the Coats-Redfern method. Solid acid catalysts with stronger acidity and higher surface area showed a decrease in activation energy and onset temperature. Activation energy of LDPE over ASA catalyst is decreased to 97.3 kJ/mol from thermal decomposition of LDPE without catalyst of 117.2 kJ/mol under heating rate of 10 °C/min. The isothermal decomposition of LDPE was monitored at 300 °C for 3 h with a heating rate of 10 °C/min, where 13.1% and 24.2% wt. loss were observed over SA and ASA, respectively, while only 0.7% wt. loss was observed for LDPE without a solid acid catalyst. Graphical abstract Single step decomposition of LDPE Thermal degradation behavior of LDPE monitored by TGA, with different heating rates (β) of 5, 10, 20 °C/min.

Potential improvement in the mechanical performance and thermal resistance of geopolymer with appropriate microplastic incorporation: A sustainable solution for recycling and reusing microplastics

The accumulation of microplastics (MPs) has been a major threat to the natural environment and human health. However, incineration and landfilling may not be appropriate for the management of MPs. This paper evaluated the feasibility of incorporating MPs with diverse dimensions (50 to 500 μm) and contents (2.5 % to 10 %) into geopolymer cured under different temperatures (40 and 80 °C). The compressive (fc) and flexural strength (ff) after curing and thermal exposure (200 to 600 °C) were determined. When cured at 40 °C, fc and ff decreased with percentages of MPs incorporated. By contrast, when cured at 80 °C, the addition of 2.5 % MPs increased fc and ff by up to 33 % (from 52.2 to 69.4 MPa) and 18 % (from 8.2 to 9.7 MPa), depending on MPs’ sizes. The XRD and TGA results suggested that the observed increases in mechanical properties can be attributed to the formation of more calcium alumino (silicate) hydrates (C-(A)-S-H gels) induced by the incorporation of a small quantity of MPs (2.5 %). The SEM images also showed better adhesion between MPs and geopolymeric products when cured under 80 °C, potentially inhibiting crack development. After being exposed to evaluated temperatures (200 and 400 °C), fc of the specimens with 2.5 % MPs and cured at 80 °C was higher than that without MPs. The fc dropped dramatically due to the degradation of MPs between 400 and 600 °C. The increase in strength and heat resistance (up to 400 °C) of MPs-incorporated geopolymer cured under 80 °C indicated the potential recycling and reuse of MPs for geopolymer materials.

Interfacial Cooperative Assembly of Surfactants and Opposite Wettability Nanoparticles Stabilizes Water-in-Oil Emulsions at High Temperature.

Pickering emulsions have promising applications in the development of unconventional oil and gas resources. However, the high-temperature environment of the reservoir is not conducive to the stabilization of Pickering emulsions. In addition, the preparation of Pickering emulsions under low-energy emulsification and low-concentration emulsifier conditions is a difficult challenge. Here, we report a high-temperature resistant water-in-paraffin oil Pickering emulsion, which is synergistically stabilized by polyglycerol ester (PGE) and nanoparticles with opposite wettability (lipophilic silica and hydrophilic alumina). This emulsion can be prepared under mild stirring (500 rpm) conditions and can be stable at 140 °C for at least 30 days. The synergistic effects of surfactant, silicon nanoparticles (MSNPs) with different wettability, and alumina nanoparticles (AONPs) on the stability of both emulsions and water-oil interfacial membranes were investigated through bottle experiments, cryogenic scanning electron microscopy (cryo-SEM), optical microscopy, fluorescence microscopy, etc. The results showed that both hydrophobic MSNPs and hydrophilic AONPs are adsorbed together at the water-oil interface to stabilize the W/O emulsion, which can be prepared by 500 rpm stirring. The stability of emulsions strongly depends on the wettability of MSNPs, and the MSNP with moderate hydrophobicity (for example, aqueous phase contact angle of 136°) makes the emulsion exhibit the highest stability against aggregation and settling at elevated temperatures. The emulsion stabilization mechanism was revealed in terms of the adsorption capacity of the surfactant by MSNPs, the adsorption morphology and desorption energy of nanoparticles at the water-oil interface adsorption layer, and emulsion rheology. These findings demonstrate a novel and simple strategy to prepare Pickering W/O emulsions with high-temperature stability at low shear strength.

Synthesis, Characterization, and Application of Amorphous Silica-Aluminas Support for Fischer-Tropsch Wax Hydrocracking Catalysts.

High-performance amorphous silica-aluminas (ASAs) were prepared prior to the formation of the 10-membered ring (10-MR) ZSM-5 zeolite by regulating the hydrothermal processing time. Their structures, morphologies, acidity properties, and Si-Al coordination were well studied. Particularly, a facile FTIR method of in-situ adsorbing bulky 2,6-dimethlypyridine followed by pyridine adsorption was innovatively utilized to quantify the Brønsted acid sites in micropores. All the ASAs samples were transformed into catalysts by loading with 0.5 wt % Pt. The structure-activity relationship, especially from the strength, density, and location of Brønsted acid sites, was investigated by Fischer-Tropsch synthesis (FTS) wax hydrocracking. The evaluation results showed that the medium strong Brønsted acid sites located on the external surface played a crucial role in the activity. Contrary to the general belief that larger pores favor the production of heavy cracking fractions, the ASAs with a 10-MR microporous structure proved to be more effective for diesel production than those with a 12-membered ring (12-MR). Strong Brønsted acid sites in micropores were less conducive to diesel production mainly due to stronger adsorption at these sites and steric hindrance from the microporous system. Furthermore, the Pt/AS-20 catalyst with few intramicropore Brønsted acid sites exhibited high diesel selectivity (83.3%) at 50.5% conversion under industrially relevant reaction conditions, which provides a significant opportunity to develop FTS wax hydrocracking catalysts more rationally.

Influence of aluminum waste, hydrogen peroxide, and silica fume ratios on the mechanical and thermal characteristics of alkali-activated sustainable raw perlite based geopolymer paste

Geopolymer concretes have great potential in the sustainable construction industry in the future, as they can be produced without using cement and waste materials can be used as binders. This paper explores the use of sustainable, lightweight geopolymer pastes as construction materials using raw perlite as the primary ingredient. It achieves this by alkaline activation with additives such as waste aluminum lathe (Al), Hydrogen peroxide (H2O2) and silica fume (SF). The experiments were conducted in four groups: Al added in the 1st group, Al + Silica fume (SF) in the 2nd group, H2O2+SF in the 3rd group, and Al + H2O2 in the 4th group. Apparent density, compressive strength, flexural strength, and thermal conductivity tests were performed at 7, 14, and 28 days. SEM and EDX analyses were also conducted. The results showed that as the ratio of Al and H2O2, which have a aerating effect, increased, decrease in apparent density and strength was observed. However, when Al + SF were added together, significant improvements of 10%–20% were observed in compressive and flexural strengths, as well as apparent density. 35% water/pearlite ratio and 0.50% Al addition reduced compressive strength by 5% and lightened apparent density by 15%. At 40% water/pearlite ratio, 0.50% Al addition reduced compressive strength by 10% and lightened apparent density by 5%. According to these results, the best performance is obtained with 35% water/pearlite ratio and 0.50% Al addition Furthermore, the addition of lightweight SF resulted in good geomerization and reduced crack formation. This effect was evident in the internal structure based on SEM analysis. Interestingly, despite aluminum's overall high thermal conductivity, its incorporation into raw perlite-based pastes resulted in reduced thermal conductivity.

Study of potassium deactivation rule in supercritical water gasification of coal with K2CO3 as catalyst

K2CO3 has a good catalytic effect in supercritical water gasification (SCWG) of coal. However, researchers have mainly focused on the effects of coal gasification, while the potassium mass transfer process has rarely been studied. Herein, the distribution pattern of potassium during the SCWG of coal and the factors influencing potassium deactivation were experimentally obtained. Through the detection and analysis of the residues after the SCWG of coal, it is found that potassium only exists in the forms of liquid and solid and the potassium in the residue exists in the form of insoluble potassium silica alumina, which does not have a catalytic effect. At a high reaction temperature, the reaction time is longer, and when the silica–aluminum content in coal is higher, the potassium deactivate rate is also higher. The molar contents of potassium and aluminum in the coal gasification residue are linearly correlated, with a ratio of approximately 1:1. Reducing the aluminum content in coal can effectively reduce potassium deactivation. In the SCWG of the Hebi coal, the deactivation rate of potassium reduced from 80.88 % to 17.75 % after acid washing. In the SCWG of the ash-free coal, the carbon gasification efficiency (CE) and potassium content in the liquid were above 95 % after each experiment, there was no deactivation of potassium, and the residual potassium solution remained catalytically effective after the SCWG of the ash-free coal.

Performance comparative study on passively cooled concentrated photovoltaic (PV) using adsorption/desorption and heat sink cooling methods: Experimental investigations

Concentrated photovoltaic (PV) is a suitable solution for reducing the cost of a PV system by focusing solar radiation on the panel with cheap collectors. However, increasing the radiation on the PV panel resulted in a higher operating temperature. The elevated temperature harms the panel's efficiency, which results in a reduced output of the generated power and PV's short life span. Considering these concerns, researchers introduced many cooling methods for more efficient and prolonged PV life. The adsorption/desorption cooling method is a new trend in PV cooling that utilizes atmospheric water harvesters to capture water from the atmosphere at night and release part of the PV heat in the daytime by evaporation of the adsorbed water. This article uses silica gel as the atmospheric water harvester to cool low-concentrated PV in the presence/absence of metal heat sinks. Three configuration designs are investigated for PV cooling: (i) cooling the concentrated PV with silica gel bed, (ii) cooling the concentrated PV with a combination of aluminum heat sink and silica gel bed, and (iii) cooling the concentrated PV with aluminum heat sink only. The work was conducted experimentally over 3 consecutive days, and the three configurations were tested at the same period and compared. It was found that the configuration, which uses a combination of a heat sink and silica gel bed, performs best with an average PV temperature reduction of 9.8 °C and enhanced generated power of 29.8 %.

Aluminosilicate-based material fabricated from fly ash for energy harvesting application

A triboelectric nanogenerator (TENG) is an emerging energy harvesting technology that utilizes the combination of triboelectrification and electrostatic induction to collect wasted mechanical energy and convert it into electricity. In this work, an aluminosilicate (AS)-based composite, considered as a potential alternative to cement material, has been developed for the fabrication of TENGs. Herein, the AS material is synthesized through the alkali activation of fly ash using a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions as activating agents. The electrical output of AS TENGs can be optimized by tuning the liquid-to-solid powder (L/S) ratio during the fabrication of AS composites. The AS composites fabricated at different L/S ratios exhibit the variations in dielectric properties, surface morphology and microstructure. It is found that a high dielectric constant is not the only requirement for achieving optimal TENG output performance. The contribution of dielectric properties and microstructures of the AS composites on TENG performance is discussed. The AS composite with an optimal L/S ratio of 0.5 results in the highest TENG power output density of 2.78 W/m2. Additionally, the versatility of AS TENG to harvest mechanical energy and its application as a power source for portable electronic device are demonstrated. This research has proposed the promising aspect of AS composites as alternative construction materials capable of harvesting mechanical energy, which is essential for the development of green and sustainable power sources.