Search Results (525)

A series of Cu-MnO_x/GF catalytic electrodes, with graphite felt (GF) pretreated via microwave modification as the catalyst carrier, were prepared under various hydrothermal conditions and characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, and Raman spectroscopy. The catalytic oxidation activity of catalytic Cu-MnO_x/GF electrodes toward toluene was evaluated in an all-solid-state electrocatalytic device under mild operating conditions. The evaluation results demonstrated that the microwave-modified catalytic electrode exhibited high electrocatalytic activity toward toluene oxidation, with Cu-MnO_x/700W-GF exhibiting significantly higher catalytic activity, indicating that an increase in catalyst loading capacity can promote the removal of toluene. Only CO₂ and CO were detected, with no other intermediates observed in the reaction process. Moreover, the catalytic effect was significantly affected by the relative humidity. The catalytic oxidation of toluene can be fully realized under a certain humidity, indicating that the conversion of H₂O to strongly oxidizing ·OH on the catalytic electrode is a key step in this reaction. Full article

Biodiesel, as one of the alternatives to fossil fuels, faces significant challenges in large-scale industrial production due to its high production costs. In addition to raw material costs, catalyst costs are also a critical factor that cannot be overlooked. This review summarizes various methods for preparing biodiesel catalysts from solid waste. These methods not only enhance the utilization rate of waste but also reduce the production costs and environmental impact of biodiesel. Finally, the limitations of waste-based catalysts and future research directions are discussed. Research indicates that solid waste can serve as a catalyst carrier or active material for biodiesel production. Methods such as high-temperature calcination, impregnation, and coprecipitation facilitate structural modifications to the catalyst and the formation of active sites. The doping of metal ions not only alters the catalyst’s acid-base properties but also forms stable metal bonds with functional groups on the carrier, thereby maintaining catalyst stability. The application of microwave-assisted and ultrasound-assisted methods reduces reaction parameters, making biodiesel production more economical and sustainable. Overall, this study provides a scientific basis for the reuse of solid waste and ecological protection, emphasizes the development potential of waste-based catalysts in biodiesel production, and offers unique insights for innovation in this field, thereby accelerating the commercialization of biodiesel. Full article

This study investigated the effect of KOH activation on biochar, with a focus on how porosity and potassium content influence microwave-assisted catalytic biodiesel production, using experimental design approaches. Activated biochar was synthesized from oat hull waste through KOH activation, followed by pyrolysis under controlled conditions. The biochar was characterized through chemical, morphological, and physical analyses, and its catalytic performance in converting used waste cooking oil (WCO) into biodiesel was evaluated using methanol as the acyl acceptor and microwave irradiation to optimize the reaction via experimental design. Results revealed that increasing the KOH/biomass ratio significantly enhanced the specific surface area (SSA) of the catalyst, achieving a maximum SSA of 637.28 m²/g under optimal pyrolysis conditions: 600 °C for 3 h with a KOH/biomass ratio of 2. A maximum fatty acid methyl ester (FAME) yield of 100% was achieved within 1 min of microwave-assisted reaction using an optimized catalyst dosage of 2.5%, a WCO/MeOH molar ratio of 1/12, and a reaction temperature of 150 °C, with the catalyst being successfully recycled across three cycles. An economic and energy evaluation estimated a catalyst production cost of USD 176.97/kg and a biodiesel production cost of USD 8.9/kg of FAMEs. This research provides a straightforward and cost-effective approach for biofuel production. Full article

Catalysts are ubiquitous in manufacturing industries and gas phase pollutant abatement but are not widely used in wastewater treatment, as high temperatures and concentrated waste streams are needed to achieve the reaction degradation rates required. Heating water is energy intensive, and alternative, low temperature solutions have been investigated, collectively known as advanced oxidation processes. However, many of these advanced oxidation processes use expensive oxidants such as perchlorate, hydroxy radicals or ozone to react with contaminants, and therefore have high running costs. This study has investigated microwave catalysis as a low-energy, low-cost technology for water treatment using NiO catalysts that can be heated in the microwave field to drive the decomposition of azo-dye contaminants. Using this methodology for the microwave-assisted degradation of two azo dyes (azorubine and methyl orange), conversions of >95% were achieved in only 10 s with 100 W microwave power. Full article

Plastic waste is currently a major concern in Romania due to the annual increase in quantities generated from anthropogenic and industrial activities, especially from end-of-life vehicles (ELVs), and the need to reduce environmental impact. This study investigates an alternative valorization route for polypropylene (PP) and polyethylene (PE) plastic waste through microwave-assisted pyrolysis, aiming to maximize conversion into gaseous products, particularly hydrogen-rich gas. A monomode microwave reactor was employed, using layered configurations of plastic feedstock, silicon carbide as a microwave susceptor, and activated carbon as a catalyst. The influence of catalyst loading, reactor configuration, and plastic type was assessed through systematic experiments. Results showed that technical-grade PP, under optimal conditions, yielded up to 81.4 wt.% gas with a hydrogen concentration of 45.2 vol.% and a hydrogen efficiency of 44.8 g/g. In contrast, PE and mixed PP + PE waste displayed lower hydrogen performance, particularly when containing inorganic fillers. For all types of plastics studied, the gaseous fractions obtained have a high calorific value (46,941–55,087 kJ/kg) and at the same time low specific CO₂ emissions (4.4–6.1 × 10⁻⁵ kg CO₂/kJ), which makes these fuels very efficient and have a low carbon footprint. Comparative tests using conventional heating revealed significantly lower hydrogen yields (4.77 vs. 19.7 mmol/g plastic). These findings highlight the potential of microwave-assisted pyrolysis as an efficient method for transforming ELV-derived plastic waste into energy carriers, offering a pathway toward low-carbon, resource-efficient waste management. Full article

Ni-based catalysts have been widely used in catalytic reactions by researchers due to their advantages such as abundant resources, high catalytic activity and lower prices than precious metals. However, the problems of easy agglomeration and poor dispersion of Ni-based catalysts have hindered their large-scale application. Therefore, it is necessary to select a suitable preparation method to reduce the agglomeration of the catalyst and improve its dispersion. In this paper, the Ni-NiAl₂O₄/tourmaline composite material was prepared by using the microwave hydrothermal reduction method. The most favorable conditions for preparing NiAl₂O₄/tourmaline are as follows: using TEOA as the additive, the microwave hydrothermal temperature is 220 °C, the calcination temperature is 800 °C, and the addition amount of tourmaline is 7.4 wt.%. NiAl₂O₄ has a good dispersion over the surface of tourmaline support and the optimal NiAl₂O₄/tourmaline catalyst exhibits a specific surface area of 106.5 m²/g. Metallic nickel was reduced at 650 °C to further obtain Ni-NiAl₂O₄/tourmaline composites. Finally, the Ni-NiAl₂O₄/tourmaline composites showed significantly improved catalytic dry reforming of methane (DRM) activity compared to Ni-NiAl₂O₄ sample under low-temperature conditions (500–600 °C), meaning that the tourmaline carrier could effectively optimize the low-temperature catalytic performance of Ni-NiAl₂O₄. Full article

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule with the potential to replace many fossil fuel derivatives. It can be obtained through the dehydration of carbohydrates. In this study, we present a simple and cost-effective microwave-assisted method for producing HMF. This method involves the use of readily available sucrose as a substrate and glucose-derived bifunctional hydrochars as carbocatalysts. These catalysts were produced via hydrothermal carbonisation using thiourea and urea as nitrogen and sulphur sources, respectively, to introduce Brønsted acidic and basic sites into the materials. Using a microwave reactor, we found that the S, N-doped hydrochars were active in sucrose dehydration in water. Catalytic results showed that HMF yield depended on the balance between acidic and basic sites as well as the types of S and N species present on the surfaces of these hydrochars. The best-performing catalyst achieved an encouraging HMF yield of 37%. The potential of N, S-co-doped biochar as a green solid catalyst for various biorefinery processes was demonstrated. A simple kinetic model was developed to elucidate the kinetics of the main reaction pathways of this cascade process, showing a very good fit with the experimental results. The calculated rate constants revealed that reactions with a 5% sucrose loading exhibited significantly higher fructose dehydration rates and produced fewer side products than reactions using a more diluted substrate. No isomerisation of glucose into fructose was observed in an air atmosphere. On the contrary, a limited rate of isomerisation of glucose into fructose was recorded in an oxygen atmosphere. Therefore, efforts should focus on achieving a high glucose-to-fructose isomerisation rate (an intermediate reaction step) to improve HMF selectivity by reducing humin formation. Full article

Microwave-assisted ionothermal strategies offer an effective pathway for rapid zeolite crystallization under mild conditions, while conventional ionothermal approaches are still constrained by prolonged crystallization cycles that limit their industrial applicability. Herein, we report a microwave-activated, ionic liquid-mediated synthesis strategy that enables the precise modulation of crystallization kinetics and composite assembly. By introducing ZSM-5 seeds into the ionic liquid system, the nucleation and growth of AlPO₄-5 were significantly accelerated, reducing crystallization time by up to 75% (optimal condition: 60 min). Among various imidazolium-based ionic liquids, [BMMIm]Br demonstrated an optimal balance of hydrophilic and hydrophobic interactions, yielding composite zeolites with high surface area (350 m²·g⁻¹) and large pore volume (0.28 cm³·g⁻¹). Comprehensive characterization (XRD, SEM-EDX, NH₃-TPD) confirmed the formation of well-defined ZSM-5/AlPO₄-5 core–shell structures and revealed tunable acid site distributions depending on the ionic liquid used. In methanol to olefins (MTO) reactions, the composite catalyst exhibited outstanding selectivity towards light olefins (C₂=–C₄=: 72.84%), markedly outperforming the individual ZSM-5 and AlPO₄-5 components. The superior catalytic behavior is primarily attributed to the synergistic effect of hierarchical acid site tuning and the integrated core–shell architecture, which together optimize reaction selectivity. This strategy provides a promising route for the rational design of high-performance zeolites with significant industrial applicability. Full article

Several benzothiazole (BT) derivatives have recently been explored in medicinal chemistry, and they are frequently reported in the literature. The interest in this kind of heterocyclic compounds and their structural hybrids has been increasing, as shown by several reviews reported over the last decade. In this context, we found that about 70 articles related to the synthesis of BT derivatives that studied their biological activities were published in the last five years. From this, we prepared a review on the synthesis and biological activity studies about this topic. In this bibliographic review it was found that medicinal chemists also explore BT derivatives in search of anticancer and anti-Alzheimer’s candidates. This review comprehends 70 articles, published between 2020 and 2024, related to the synthesis of BT derivatives with the purpose of assessing their biological activities. On the other hand, BT derivatives have been explored as molecular species that perform two or more biological actions, called multifunctional drugs. Some accounts related to the structure–activity relationship which provide a framework for drug discovery and design are also discussed. The synthetic methods of BT synthesis include the use of biocatalysts, solvent-free conditions, photocatalysts, and catalysts supported on nanoparticles. Studies also explore renewable energy sources such as microwave, UV, and visible-light and mechanochemical sources. Full article

This work studies the effect of mesostructured silica–zirconia–tungstophosphoric acid (SiO₂-ZrO₂-TPA) composites used as catalysts in the synthesis of nifedipine by the Hantzsch methodology. The selectivity for nifedipine is determined, along with that of secondary products that may form depending on the reaction conditions. The materials were synthesized via the sol–gel method and characterized by N₂ adsorption–desorption isotherms, infrared spectroscopy (FT-IR), ³¹P solid-state nuclear magnetic resonance (NMR-MAS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectra (XPS), and potentiometric titration. The characterization results from the XPS spectra showed that as the Si/Zr ratio drops, the Si-O-Si signal size decreases, while the Zr-O signal size increases. Characterization by titration indicated that an increase in the total acidity of the material, resulting from support modification with tungstophosphoric acid (H₃PW₁₂O₄₀, TPA), enhances the reaction yield. The catalytic activity in the solvent-free Hantzsch reaction was evaluated under thermal heating and microwave irradiation. The experiments conducted at 80 °C achieved a maximum yield of 57% after 4 h of reaction using the Si20Zr80TPA30 catalyst (50 mg), while by microwave heating, the yield significantly improved, reaching 77% in only 1 h of reaction. This catalyst exhibited stability and reusability without significant loss of activity up to the third cycle. Depending on the type of material and the reaction conditions, it is possible to modify the selectivity of the reaction, obtaining a 1,2-dihydropyridine isomeric to nifedipine. Reaction intermediates and other minor secondary products that may be formed in the process were also evaluated. Full article

Composite catalysts combining absorbers and active metal hold significant potential for improving the efficiency of biomass microwave-assisted pyrolysis (MAP). Compatibility optimization of composite catalysts can be facilitated through comparative analysis for the influential mechanisms of absorbers and catalysts. Therefore, decoupling experiments about the MAP of Sargassum and calculations based on density functional theory (DFT) were conducted in this research, to investigate the influential mechanisms of absorbers and active metal. The results show the introduction of both the absorbers (SiC) and active metal (MgO) increase the yields of high-value components, such as hydrogen and hydrocarbons. However, their influential mechanisms are different. The introduction of SiC enhances the heating rate within the reaction zone, shortening the duration of MAP and inhibiting the condensation of bio-oil and the interaction between bio-oil and bio-char, and thereby increasing the bio-oil yield by 4%. The introduction of MgO lowers the energy barriers for macromolecular decomposition and gas generation, promoting the decomposition of bio-char and bio-oil, and thus leading to a 12% increase in the yield of bio-gas. This research conclusion provides a theoretical basis for the optimization and design of composite catalysts. Full article

Magnetic Fe and N-doped biochar (FeN-BC) was synthesized from waste bamboo through microwave pyrolysis and used as a catalyst for the degradation of tetracycline hydrochloride (TC) with peroxymonosulfate (PMS). The results showed that doping with Fe improved the recovery performance of biochar and the N-doping enhanced the activity of PMS. Simultaneously, it achieved a high degradation efficiency for TC (93%) under optimized conditions within 30 min. Electron paramagnetic resonance (EPR) and quenching experiments indicated that the main active radicals present in the experiment were SO₄^•− and •OH. Additionally, FeN-BC demonstrated good catalytic performance in the TC degradation process in a real water environment after five cycles. This work presents a practical strategy for preparing magnetic biochar to degrade organic pollutants from wastewater. Full article

Poly(lactic acid) (PLA) is a widely used biobased polyester which can be derived from renewable resources. Due to its excellent properties, it has already been adopted in various industrial sectors. While PLA is compostable, its degradation to the environment is very slow, necessitating the development of efficient recycling methods. This study focuses on the chemical recycling via microwave-assisted alkaline hydrolysis of PLA and its copolymers with poly(ethylene azelate) (PEAz), aiming to recover both carboxylic acid monomers: lactic acid and azelaic acid. Moreover, our method tunes the degradation of PLA via the synthesis of the novel aliphatic PLA-based copolyesters, targeting engineering-like applications, specifically in the field of printed electronics. Various process parameters were analyzed, including the temperature and the duration of the experiments as well as different phase transfer catalysts. Complete degradation was achieved at low temperatures (110–125 °C) and short times (12–15 min) for the PLA-based copolyesters, offering significant environmental benefits, as considerably less energy is consumed compared to chemical conventional methods. So, by changing the composition of the copolyesters through the incorporation of PEAz blocky segments, the ester bonds became more susceptible to hydrolysis under alkaline conditions assisted with microwave irradiation. Additionally, enzymatic hydrolysis was also studied in parallel for comparative purposes, revealing low degradation rates, thus establishing the microwave-assisted alkaline hydrolysis as a solid and reliable method for tuning the degradation of PLA-based materials. Full article

In this work, a biochar catalyst was developed from residual brewery spent grain (BSG) biomass and iron oxide to be applied in the counter electrode (CE) in dye-sensitized solar cells (DSSCs). The composite was obtained using a two-stage methodology based on microwave-assisted hydrothermal carbonization and pyrolysis, evaluating the influence of the pyrolysis temperature (700, 800 and 900 °C) on the properties and performance of the material. As result, composites with a high carbon and iron oxide content were obtained in a magnetite state attached to the surface. Furthermore, the physicochemical characteristics of the biochar showed similarities to those of reduced graphene oxide (rGO), which was attributed to the incorporation of iron oxide and the pyrolysis temperature. Electrochemical analysis showed that the composite pyrolyzed at 800 °C presented better catalytic activity and lower charge transfer resistance. Its application in the CE of a DSSC presented a current density of 10.44 mA/cm² and an efficiency of 3.05%, values close to the conventional Pt catalyst in DSSCs (Pt = 4.43%). This study validates the use of a composite based on residual brewery biomass with iron oxide in a CE, making it an alternative that contributes to the recovery of residues and the generation of sustainable technologies. Full article

In the face of the intensifying energy and environmental challenges, the exploration of clean and sustainable approaches to energy conversion and utilization holds paramount significance. 5-Hydroxymethylfurfural (HMF), as a biomass platform compound with great potential, has drawn extensive attention for its oxidation to prepare 2,5-Furandicarboxylic acid (FDCA). In this study, a CoS-doped CuS composite catalyst (CoS–CuS) was synthesized via a one-step microwave–hydrothermal method for the electrocatalytic oxidation of HMF. The catalyst was comprehensively analyzed by means of multiple characterization techniques and electrochemical testing methods. The results demonstrate that the doping of CoS optimizes the surface electronic structure of the catalyst, enhancing its adsorption capabilities for HMF and OH⁻. Compared with the CuS catalyst, CoS–CuS in the 5-hydroxymethylfurfural oxidation reaction (HMFOR) shows a lower onset potential decreasing from 1.32 V_RHE to 1.29 V_RHE. At a potential of 1.4 V_RHE, the current density of CoS–CuS attains a value 2.02-fold that of CuS. Significantly, CoS–CuS demonstrates a substantially higher Faraday efficiency in the generation of FDCA, reaching nearly 89.1%. This study provides a promising approach for the construction of other efficient copper-based electrocatalysts. Full article