Topics in Catalysis最新文献

Thermal and catalytic aqueous hydrothermal liquefaction of Ricinus communis and Jatropha curcas L. seeds, after mechanical defatting, was conducted at 260 °C for 40 min under subcritical water conditions with a biomass-to-water ratio of 1:5 (expressed in wt.). For catalytic aqueous hydrothermal liquefaction, Ni-Pt/Al₂O₃ was used as heterogeneous catalyst besides a solution of glycerol as in situ hydrogen donor agent. It was noticed that the combination of heterogeneous catalytic aqueous phase glycerol reforming and hydrothermal liquefaction favours and increases the biocrude yield, without external H₂ supply. Indeed, a maximum biocrude yield of 59 wt% was registered when Ricinus communis defatted seed was used as starting biomass, which represents an increase of 28 wt% compared to the yield obtained by the non-catalytic HTL process. The biocrudes analysis by GC/MS confirmed that approximately 60% were C16 and C18 hydrocarbon compounds, indicating that the catalyst linked with aqueous glycerol reforming has a marked effect on distribution and upgraded fuel-biocrude stability and quality respect to direct hydrothermal liquefaction (HTL-D). The bimetallic Ni-Pt/Al₂O₃ conformed catalyst (with a Ni: Pt = 100:1 expressed as an atomic ratio) was effective in the coupled reactions of aqueous reforming of glycerine as well as hydrodeoxygenation and hydrocracking. It upgrades the biocrude with a lower O/C ratio and a higher H/C ratio, which is directly reflected in the HHV of the biocrude that reaches the value of 37 MJ·kg^− 1 and can be used as direct fuel. The heterogeneous catalytic process technology, by coupling the glycerol APR and the assisted hydrolysis-depolymerisation of wet-biomass in water subcritical conditions yield to a biomass-derived biocrude with liquid fuel quality.

Landfill leachate is a highly hazardous effluent characterized by a high concentration of recalcitrant pollutants, presenting a significant environmental challenge. This study investigated the solidification of landfill leachate contaminants using sodium hydroxide-activated Granulated Blast Furnace Slag (GBFS). The stability of the resulting geopolymer was evaluated through unconfined compressive strength and leaching tests. Optimal curing conditions were identified as 7 days at a sodium hydroxide concentration of 12 M, achieving an unconfined compressive strength of 45.738 MPa at a liquid-to-solid ratio of 15%. A linear relationship was observed between the liquid-to-solid ratio and flow workability, with maximum flow workability evidenced by an average diameter of 242 mm at a liquid-to-solid ratio of 0.25. However, a minimum liquid-to-solid ratio of 0.15 was necessary to obtain a workable mortar. The produced geopolymers were characterized using X-ray Fluorescence (XRF) for mineralogical analysis, Scanning Electron Microscopy (SEM) for morphological examination, and the Toxicity Characteristic Leaching Procedure (TCLP) for leaching tests. The findings demonstrated the successful solidification of landfill leachate using GBFS geopolymer. The leachability tests revealed that the geopolymer did not release metals in concentrations exceeding the allowable limits set by the United States Environmental Protection Agency (USEPA), indicating effective encapsulation of the pollutants within the geopolymer matrix. Furthermore, the resultant geopolymer brick is eco-sustainable and can be classified as a green construction material.

Dimethyl carbonate (DMC) has emerged as a promising candidate for sustainable chemical processes due to its remarkable versatility and low toxicity. From a green chemistry perspective, the direct synthesis of DMC has been considered the most promising route, as water is the only byproduct generated in the reaction between CO₂ and methanol. However, this synthetic route has faced significant thermodynamic limitations, even at elevated pressure conditions. Therefore, a two-part study explored low-pressure synthesis of DMC via the direct route, and a low-pressure kinetic model for the CeO₂ catalyst was developed based on the results. Proposed Langmuir–Hinshelwood mechanisms were verified using experimental data generated in our labs. The investigation suggests that DMC formation in the direct synthetic route is a surface reaction of CO₂ and methanol on the catalyst. The kinetic model predictions closely aligned with experimental data, demonstrating a 17% mean absolute percentage error and indicating a high level of predictability. Additionally, a rigorous assessment was conducted on CO₂ fixations in DMC synthesis, quantifying CO₂ capture and its conversion into stable or high-value products, formally designated as CO₂ Fixation (CO2Fix). The CO2Fix analysis revealed that, at a conversion rate of 27%, the process can achieve a "net zero" state when operated at an approximate pressure of 30 bar, thereby supporting the viability of low-pressure synthesis. Increasing the conversion rate to levels exceeding 95% significantly enhances the CO2Fix metric, potentially surpassing 3.5 or higher.

Polyalkylene oxides and polyether polyols are the most frequently used raw materials in polyurethane production, and are commonly produced via the ring-opening polymerization of epoxides, particularly propylene oxide. However, the resulting polyols predominantly contain predominantly secondary hydroxyl groups (up to 95%) that are less reactive than those capped with primary hydroxyl groups, thereby limiting the applications of the former in polyurethane synthesis. In this study, a viable procedure for producing α,ω-primary hydroxyl-terminated polyols using various Prussian blue analogs as heterogeneous catalysts was developed. The reaction kinetics were first investigated to gain insight into the reactivity of primary and secondary alcohols in the ring-opening of ε-caprolactone. Subsequently, ε-caprolactone-capped polyols with predominantly primary hydroxyl groups were successfully synthesized via the ring-opening reaction of ε-caprolactone using polypropylene glycol as the macroinitiator. The reactivities of the resultant ε-caprolactone-capped polyols for polyurethane synthesis were greatly enhanced compared to those of conventional polyols.

In this work, hydrocalumite, a layered double hydroxide with formula Ca₂Al(OH)₆Cl·2H₂O, has been prepared for the first time using flow semi-continuous mechanochemistry with a DYNO®-MILL RESEARCH LAB (Willy A. Bachofen AG, Switzerland), with stoichiometric amount of reactants in water, after only 5 min at 25 °C. Hydrocalumite, before and after thermal treatment, was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG–DTA) and N₂ sorption at − 196 °C. Moreover, calcined hydrocalumite has been evaluated as catalyst for the isomerization of glucose to fructose, a catalytic process which has also been performed in the same flow semi-continuous mechanochemical reactor. This mechanochemical system, unlike conventional ball milling, allows working in semi-continuous and/or continuous mode, using solvents and allowing heating control up to temperatures of 80 °C. The isomerization of glucose to fructose was successfully carried out in this reactor, demonstrating that hydrocalumite prepared by mechanochemistry is more active than that prepared by co-precipitation. The optimization of several experimental variables (reaction temperature and time, glucose/catalyst weight ratio and concentration of glucose in water) has resulted in a 23.5% fructose yield, with a glucose conversion of 38.1%, after 1 h of reaction, at 50 °C, with a 17 wt% glucose and a glucose/catalyst weight ratio of 6. However, the highest fructose productivity was reached under similar experimental conditions, but after only 5 min, with a value of 0.50 kg_fructose L_H2O⁻¹ h⁻¹ (equivalent to 15 kg_fructose Kg_cat⁻¹ h⁻¹), which is susceptible to be improved by implementing a continuous mode, assisted with a liquid pump, in the mechanochemical reactor. Therefore, this work has evidenced the versatility and potential of this new flow semi-continuous mechanochemical reactor for the synthesis of crystalline layered double hydroxides, under sustainable experimental conditions, and to perform catalytic processes with high performance, using water as solvent and atmospheric conditions.

Activated carbon based Cobalt nanoparticles (Co@AC NPs), considered in the context of hydrogen energy, which is a renewable and sustainable energy, were synthesized by the hydrothermal method, and their catalytic activities were tested. For this, hydrogen production tests were carried out with the help of sodium borohydride (NaBH₄) methanolysis of Co@AC NPs synthesized by the thermal method. Ultraviolet–visible spectroscopy (UV–Vis), Fourier transmission spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray diffraction (XRD) characterization tests were performed. According to the TEM characterization result, it has been observed that the NPs have a spherical shape and an average size of 2.52 ± 0.92 nm. Then, using the catalytic studies, it was observed that hydrogen production’s reusability is found to be 86% . The activation energy (Ea), enthalpy (∆H), and entropy (∆S) values were found to be 20.28 kJ⋅mol⁻¹, 17.74 kJ⋅mol⁻¹, and −125.97 J⋅mol⁻¹ K⁻¹, respectively. The obtained values have yielded excellent results and guide future sustainable and renewable hydrogen energy studies by reducing costs, ensuring environmental sustainability by avoiding the formation of undesirable by-products, and producing hydrogen from NaBH₄ through its high catalytic properties.

In this work, a practical approach was utilized to fabricate a zirconium (Zr)-based metal organic framework (UiO-66 MOF) via a one-pot solvothermal method, with the intention of employing it as an electrocatalyst. The characterization of UiO-66 MOF was investigated by several techniques. The synthesized UiO-66 MOF was employed to modify a screen-printed graphite electrode (UiO-66 MOF/SPGE) using a drop-casting technique. The electrochemical characteristics of the UiO-66 MOF/SPGE sensor for morphine oxidation were analyzed through various techniques, including cyclic voltammetry (CV), chronoamperometry, and differential pulse voltammetry (DPV). Under the optimized conditions, the prepared UiO-66 MOF/SPGE exhibited a linear range of 0.03 to 440.0 µM for morphine detection, as evidenced by the DPV results. The limit of detection for morphine was found to be 0.01 µM. The proposed sensor displayed excellent electro-catalytic activity toward the simultaneous determination of tramadol and morphine. The peak-to-peak potential separations between tramadol and morphine are 400 mV. Furthermore, the developed sensor was effectively utilized for the quantification of tramadol and morphine in real samples, yielding satisfactory recovery values.

The review paper delves into the intricacies of water quality index (WQI) and its relationship with land use and land cover in the Ganga River basin of Uttar Pradesh. The study highlights the significance of the Ganga River, a major perennial river in India, and presents findings from previous paper work shows that 57 sites of Ganga basin show fair, poor, or heavily polluted water quality. Analysis of live storage data within the basin revealed a notable increase in LULC compared to previous years, resulting in decrease water quality indicators such as low rate of dissolved oxygen (DO) levels and high concentrations of pollutants like faecal coliform, total coliform, and nitrate (NO₃^-). The observed increased in nitrate concentration, particularly attributed to enhance industrial activities and agricultural runoff during the harvesting season, suggests a negative trend towards water quality restoration. The prevalence of untreated commercial and industrial wastewater remains a significant challenge to sustained water quality improvement. In conclusion, the paper advocates for addressing land use land cover of the Ganga basin and ensuring adequate flow releases to rejuvenate the river effectively. It underscores the need for comprehensive measures to sustainably manage land use and cover water resources and mitigate anthropogenic impacts on the middle Ganga River.