Search Results (324)

Ethanol upgrading via catalytic C–C coupling, commonly known as the Guerbet reaction, offers a sustainable route to produce 1-butanol, a high-performance biofuel. To address gaps in the mechanistic understanding of the catalytic reaction, we investigated the process involving a fixed-bed reactor, operated at 275–325 °C, 21 bar, and weight hourly space velocities of 0.25–2.5 g_EtOH/(g_cat·h), using helium as a carrier gas, with a 5:1 He/EtOH molar ratio. The catalyst was a MgO–Al₂O₃ mixed oxide (Mg/Al = 2:1), derived from a hydrotalcite precursor. A detailed kinetic model was developed, encompassing 15 species and 27 reversible steps (10 sorption and 17 reaction steps), within a 1+1D sorption–reaction–transport framework. Four C₄-forming pathways were included: aldol condensation to form crotonaldehyde, semi-direct coupling to form butyraldehyde and crotyl alcohol, and direct coupling to form 1-butanol. To avoid overfitting, Arrhenius parameters were grouped by reaction type, resulting in sixty rate parameters and one active site-specific density parameter. The optimized model achieved high accuracy, with an average prediction error of 1.44 times the experimental standard deviation. The mechanistic analysis revealed aldol condensation as the dominant pathway below 335 °C, with semi-direct coupling to crotyl alcohol prevailing above 340 °C. The resulting model provides a robust framework for understanding and predicting complex reaction networks in ethanol upgrading systems. Full article

Layered double hydroxide Ti-Zn-CO₃ was synthesized by the co-precipitation method with a molar ratio of 2. The synthesized material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA/DTG), UV–vis diffuse reflection spectroscopy (DRS), and Scanning Electron Microscopy (SEM). The photocatalytic degradation of Trypan Blue (TB) and Naphthol Green B (NGB) dyes from aqueous solutions under UV irradiation was investigated. The effects of contact time, photocatalyst dose, dye concentration, solution pH, scavenger effect, and regeneration of catalyst were investigated. The kinetic study showed that the equilibrium was reached within 30 min and 40 min for TB and NGB dyes, respectively, with photodegradation efficiency of around 91% and 83% for TB and NGB dyes, respectively, for dye concentration of 25 mg∙L⁻¹, and the pseudo-first order showed good agreement with the reaction. The optimum photocatalyst dose is 20 mg (1 g∙L⁻¹) and 30 mg (1.5 g∙L⁻¹) for TB and NGB dyes, respectively, and the optimal pH of reaction was found to be 7 for both TB and NGB dyes. This study was established to highlight the photodegradation performance of the prepared catalyst Ti-Zn-CO₃ for the degradation of (TB and NGB) dyes chosen as pollutants, and the fact that it can be used many times, which has an economical effect. This mean that the prepared sample is a potential catalyst with good photocatalytic activity, stability, and reusability. Full article

Acrylic resin composites with a high filler loading, consisting of a fluoride-containing hydrotalcite incorporated into silica nanoparticles, were prepared. The filler was obtained by a multi-step process. First, ZnAl hydrotalcite in fluoride form (HTlc/F) was functionalised with tetraethoxysilane to form Si-O-M bonds (M = Al or Zn) with the brucitic layers. The ethoxysilane groups exposed on the layers were used as nucleation seeds for silica nanoparticles. The composite, named SiO₂@HTlc/F, was then functionalised with 3-(trimethoxysilyl)-propyl methacrylate groups and used as a filler for acrylic resins. The methacrylate groups on the surface of the inorganic composite participated in the polymerisation process of the resin by minimising the phase separation between inorganic and polymer through the formation of chemical bonds at the polymer–inorganic interface. The filler in the resin increases the degree of polymerisation, bringing it to values very close to 100%. Finally, preliminary studies on the release of fluoride anions showed that they are released slowly over time. Full article

Metal carbonyl clusters, which can be seen as monodispersed and atomically defined nanoparticles stabilized by CO ligands, were used to prepare Ru-based catalysts with tuned basic properties to conduct the 5-hydroxymethylfurfural (HMF) aerobic oxidation to produce 2,5-furandicarboxylic acid (FDCA) in base-free conditions. The controlled decomposition of the carbonyl cluster [HRu₃(CO)₁₁]⁻, a methodology not yet applied to Ru catalysts for this reaction, on different supports focusing on controlling and tuning the basic properties of support allowed the formation of small Ru nanoparticles with a mean diameter of around 1 nm. The catalytic systems obtained resulted in more activity in the HMF oxidation than those prepared through a more common salt-impregnation technique, and the deposition of Ru nanoparticles on materials with basic functionalities has allowed avoiding the use of basic solutions in the reaction. The characterization by CO₂-TPD of Mg(Al)O catalysts obtained from decomposition of layered double hydroxide hydrotalcites with different composition and activation has allowed disclosure of an important correlation between the selectivity of FDCA and the fraction of weak basic sites, which is decreased by the calcination treatment at increased temperature. Full article

Background: The antidiabetic drug gliclazide is often taken with antacids due to its gastrointestinal side effects. However, patients rarely report antacid use, making drug–drug interactions a potential cause of therapy failure. Therefore, this study aimed to investigate the in vitro effects of various antacids on gliclazide permeability and to explore the underlying mechanisms. Methods: The permeability of gliclazide alone and in the presence of antacids (sodium bicarbonate, calcium carbonate, aluminum hydroxide, hydrotalcite and calcium carbonate/magnesium carbonate) was investigated using the parallel artificial membrane permeability assay (PAMPA) in four media (buffers pH 1.2, pH 4.5, pH 6.8 and water). The permeability coefficients were calculated, and the effect of pH on gliclazide permeability was also evaluated. Results: At simulated fasting gastric conditions (pH 1.2), groups with calcium carbonate, hydrotalcite and the combination of calcium carbonate/magnesium carbonate showed significantly higher permeability of gliclazide than the control group. At fed-state gastric conditions (pH 4.5), only hydrotalcite did not significantly change the permeability of gliclazide. Sodium bicarbonate, aluminum hydroxide and hydrotalcite significantly reduced the gliclazide permeability in comparison to the control group at pH 6.8 as a representative of fasted-state intestinal fluid. Conclusions: Antacids significantly impact the permeability of gliclazide at different pH values, potentially influencing its bioavailability. Gliclazide permeability is mainly influenced by pH-dependent ionization, though complex or salt formation may also play a role. Since both gliclazide and antacids are taken with food, and gliclazide is primarily absorbed in the small intestine, calcium- and magnesium-based antacids can be considered the most suitable choice. Full article

In order to effectively recover Li from cathode active materials of lithium-ion batteries, model samples of LiCoO₂ mixed with polyvinylidene fluoride (PVDF) were calcined at temperatures of 350–700 °C under an Ar or air atmosphere. Complete Li recovery was achieved by calcining the model sample at 400 °C under an Ar atmosphere, followed by water leaching. Additionally, to immobilize PVDF-derived F, an impurity in Li purification, we explored the use of calcium compounds (Ca(OH)₂ and CaCO₃) and a layered double hydroxide in both dry and wet processing methods. In the wet process, F was fixed by adding Ca(OH)₂ to an aqueous LiF solution containing 1000 ppm of F. We confirmed that 98.6% of F was successfully removed from the solution after repeated fixation procedures. Furthermore, the unreacted Ca in the solution was separated and removed as CaCO₃ by concentrating the solution. Full article

The worldwide demand for sustainable bioprocesses is undeniable, as well as for research aimed at the biotechnological exploitation of lignocellulosic materials, especially their hemicellulosic fractions rich in xylose. Various bioproducts can be obtained from these fractions, although some bottlenecks still exist, such as the presence in hemicellulosic hydrolysates of compounds that are toxic for microorganisms, which requires a previous step of detoxification to reduce them to non-inhibitory levels. The present investigation proposes the use of hydrotalcites as a new detoxifying agent for the hemicellulosic hydrolysate of sugarcane straw to produce xylitol by Candida tropicalis, aiming at a greater removal of phenolics and less loss of sugars. The design of these experiments was used for factorial effect analysis in a simultaneous way; the influences of pH and temperature were evaluated, considering the detoxification process at different times for both uncalcined and calcined hydrotalcite adsorbents. While for the calcined hydrotalcite, the temperature was the significant factor, for the uncalcined, there was also an influence of pH and little effect on the factors of yield and productivity. The effectiveness of hydrotalcites as demonstrated in this research, mainly regarding the ability to reduce the content of phenolic compounds in hydrolysates with a low loss of sugar content, followed by fermentability to produce xylitol, is a strong requirement for the proposition of these new adsorbents in investigations of the development of sustainable technologies for obtaining bioproducts in a biorefinery context. Full article

The inherent flammability and toxic smoke emission of epoxy resins (EPs) pose significant challenges to their advanced engineering applications. To address this limitation, we developed a novel flame-retardant additive through the organic modification of layered double hydroxides (LDHs) using a ternary MgAlLa hydrotalcite structure intercalated with phosphotungstic acid (PWA). This innovative design established a synergistic mechanism by combining the catalytic carbonization effect of lanthanum with the radical scavenging capability of PWA. The optimized MgAlLa-PWA/EP composite demonstrated remarkable flame retardancy and smoke suppression improvements, exhibiting 77.9% and 62.4% reductions in the peak heat release rate (pHRR) and total heat release (THR), respectively, compared to pure EP. Particularly noteworthy was the 72.6% decrease in total smoke release (TSR), accompanied by a significant elevation of the limiting oxygen index (LOI) value to 26.8% and achievement of UL-94 V-0 rating. Microstructural analysis revealed that the modified composite formed a continuous and uniform layer with increased density during combustion, effectively inhibiting oxygen exchange, smoke diffusion, and heat transfer. This study provides a novel strategy for designing multi-element synergistic LDHs additive for high-efficiency flame retardancy and smoke suppression of EP. Full article

2-Methyltetrahydrofuran (2-MTHF), a hydrogenated derivative of levulinic acid (LA), is a biomass-derived platform compound with diverse and significant applications as a biofuel, gasoline additive, green solvent, and pharmaceutical synthesis intermediate. This study investigates the preparation of a Cu₁Ni₂/Al₂O₃ catalyst through the calcination–reduction of CuNiAl hydrotalcite as a precursor, which was subsequently utilized in the hydrogenation of LA to produce 2-MTHF. The calcination–reduction process applied to CuNiAl hydrotalcite results in a lattice confinement effect. This method not only disperses the active metal sites but also alters the bonding patterns of the active metals, thereby enhancing the activity and stability of the Cu₁Ni₂/Al₂O₃ catalyst. The results indicate that complete conversion of LA and a 2-MTHF yield of 87.6% can be achieved under optimal conditions of 190 °C, 5 MPa hydrogen, and a reaction time of 5 h, demonstrating an efficient one-step conversion process. Additionally, the catalyst’s recyclability was assessed through multiple reuse tests, with a loss of activity of only 9.2% after six cycle experiments, suggesting its feasibility and reliability for industrial applications. Full article

Mg-Al hydrotalcite (HT), comprising Mg²⁺ and Al³⁺ as layered hydroxide cations, was synthesized via a hydrothermal process at 200 °C. The HT was evaluated as a carrier, and subsequently, palladium was immobilized on the surface of the hydrotalcite (HT/NC), resulting in the development of an innovative biomass-based palladium catalyst. The catalyst underwent analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). It exhibited remarkable catalytic efficiency and superior activity as a catalyst in the Suzuki–Miyaura coupling reaction in water. The catalyst was recyclable without a decline in activity and could be utilized more than 10 times, with exceptional yield. Furthermore, the commercially accessible anticancer drug Elacestrant can be readily produced using this protocol. Full article

The pyrolysis carbon black (CBp) from waste tires contains zinc, iron, and other metal elements, which have high recycling value. This study proposes a simple method of recovering zinc and iron from waste tire-derived CBp to synthesize hydrotalcite-type adsorbents for the treatment of anodic dye wastewater. Firstly, zinc-aluminum hydrotalcite (LDH) and zinc-iron aluminum hydrotalcite (FeLDH) were obtained by leaching the zinc and iron ions from CBp with an acid solution. As compared with LDH, FeLDH shows increased laminate metal ion arrangement density and layer spacing. By calcining the LDH and FeLDH at 500 °C, zinc aluminum oxides (LDO) and zinc iron aluminum oxides (FeLDO) were then prepared and applied for the adsorption of dye methyl orange (MO). The results demonstrate that the maximum adsorption capacity of LDO and FeLDO are 304.9 and 609.8 mg g⁻¹ at pH of 4.0, respectively. The adsorption processes of both LDO and FeLDO are consistent with the Langmuir adsorption isotherm and the proposed second-order kinetic model. The adsorption regeneration performance and adsorption mechanism of LDO and FeLDO were also investigated in detail. Regeneration experiments show that after three cycles, the removal rate of MO by LDO remains above 80%, while that of FeLDO only remains around 64% in the first cycle after regeneration. This work would provide a new pathway to realize the high-value metal recycling of waste tire-derived CBp and solve the contamination of dye wastewater. Full article

Growing concern about anthropogenic climate change and the continuous increase in the energy demand have driven the need to explore new energy sources, particularly in the transportation sector. Biodiesel is one of the most widely used biofuels, but its disadvantages restrict its use in blends with conventional diesel. A better alternative is green diesel, a hydrocarbon biofuel that can be used in its pure form and is produced through the catalytic deoxygenation of vegetable oils. In this study, a NiMoAl catalyst derived from layered double hydroxides (LDHs) was synthesized and used for the catalytic deoxygenation of rapeseed oil to produce green diesel. The catalyst was characterized using IR, XRD, and BET analysis. The reactions were carried out in a batch reactor, and parameters such as the temperature, pressure, catalyst loading, and reaction time were examined. The results demonstrated that the complete conversion of rapeseed oil was achieved under optimal conditions (320 °C, 40 bar H₂, 4 wt% catalyst), with a diesel-range hydrocarbon content of over 90%. The recyclability of the catalyst was also evaluated, showing sustained activity over multiple reaction cycles while maintaining high conversion and selectivity toward hydrocarbons in the diesel range. Full article

γ-Valerolactone (GVL) is a promising bio-based platform molecule with significant potential for energy applications. The production of GVL via biomass-based levulinic acid (LA) is an important reaction. To enhance the conversion and selectivity of non-precious-metal catalysts in the LA-to-GVL process and to better understand the key factors influencing this conversion, we conducted a series of experiments. In this study, supported Cu-Ni bimetallic catalysts (Cu-Ni₂/Al₂O₃) were prepared using layered double hydroxides (LDHs) as a precursor. Compared with Cu-Ni catalysts synthesized via the conventional impregnation method, the Cu-Ni₂/Al₂O₃ catalysts exhibit higher catalytic activity and stability. The results demonstrated that efficient conversion was achieved with isopropanol as the hydrogen donor solvent, a reaction temperature of 180 °C, and a reaction time of 1 h. The yield of GVL reached nearly 90%, with a decrease of approximately only 6% after six consecutive cycles. The Cu-Ni₂/Al₂O₃ catalyst proved to be effective for converting biomass-derived LA to GVL, offering a route that not only reduces production costs and environmental impact but also enables efficient biomass-to-energy conversion. Full article

In order to reuse granulated blast furnace slag (GBFS) and low-strength soft clay (SC), this study developed a curing material using magnesium oxide (MgO) as an alkali activator to excite the GBFS and basalt fiber (BF) as reinforcing material to prepare the SC. The mixing ranges of GBFS, MgO, and BF were established as 9.48%~14.52%, 0.48%~5.52%, and 0%~1.00454% of the dry clay mass, respectively, and the mixing ratios of the three were optimized using the central composite design (CCD) test. Through the analysis of variance, factor interaction analysis, and parameter optimization of the CCD test, the optimal mass ratio of GBFS, MgO, and BF was determined to be 13.35:4.47:0.26. The curing material of this ratio was named GMBF and mixed with SC to prepare GMBF solidified clay. An equal amount of ordinary Portland cement (OPC) was taken and formed with SC to form OPC solidified clay. The mechanical properties, durability, and hydration products of GMBF solidified clay were clarified by the unconfined compressive strength (UCS) test, freeze–thaw cycle test, X-ray diffraction (XRD) test, and scanning electron microscopy (SEM) test. The UCS of the GMBF solidified clay was 1.08 MPa and 2.85 MPa at 7 and 91 days, respectively, which was 45.9% and 33.8% higher than that of the OPC solidified clay (0.74 MPa and 2.13 MPa) at the same curing time. After ten freeze–thaw cycles, the UCS of GMBF and OPC solidified clay decreased from the initial 2.85 MPa and 2.13 MPa to 1.59 MPa and 0.7 MPa, respectively, with decreases of 44.2% and 67.1%, respectively. By XRD and SEM, the hydration products of GMBF solidified clay were mainly calcium silicate hydrate gel and hydrotalcite. The interface bonding and bridging effect formed between BF and SC or hydration products, indicating that these interactions contributed to the solidified clay enhanced structural integrity. This study demonstrates that the CCD approach provides solution for recycling SC and GBFS. Laboratory tests confirm the potential of the optimized GMBF formulation for practical engineering applications. Full article

Polyphenols are organic molecules extracted from various fruits, such as coffee and citrus, that possess biological activity and antioxidant properties. However, the presence of polyphenols in the environment is hazardous to water quality and living health. Among a variety of water remediation methods, adsorption remains a staple in the field. Therefore, this work aims to develop porous polycaprolactone: poly(methyl methacrylate) (PCL:PMMA) membranes as a support for hydrotalcite immobilization for the removal of chlorogenic acid polyphenol (CGA) from aqueous solutions. Due to the hydrophilic nature of hydrotalcite, the adsorbent was functionalized with hexadecyltrimethylammonium bromide (CTAB) to increase its affinity for CGA, resulting in a removal efficiency of approximately 96%. Composite fiber membranes were prepared by solution-blowing spinning with specific amounts of hydrotalcite added (i.e., 1 to 60 wt%). A 3:1 PCL:PMMA blend resulted in superior mechanical traction (0.8 MPa) and stress deformation (70%) compared to pure PCL (0.7 MPa and 37%) and PMMA (0.1 MPa and 5%) fibers. PCL:PMMA membranes with 60% LDH-CTAB exhibited CGA removal rates equal to 55% in the first cycle while maintaining the capacity to remove 30% of the polyphenol after five consecutive reuses. Removal rates up to 90% could also be achieved with an appropriate adsorbent dose (2 g L⁻¹). Adsorption was found to follow pseudo-second-order kinetics and was adequately described by the Langmuir model, saturating LDH-CTAB active sites in four hours. PCL:PMMA:LDH-CTAB composites can be considered a potential alternative to support adsorbents for water remediation. Full article