Search Results (886)

Plastic pollution, driven by the durability and widespread use of polyolefins such as polypropylene (PP) and high-density polyethylene (HDPE), poses a formidable environmental challenge. To address this issue, we have developed an integrated multiscale framework that combines thermocatalytic experimentation, process-scale simulation, and molecular-level modeling to optimize the catalytic pyrolysis of PP and HDPE waste. Under the identified optimal conditions (300 °C, 10 wt % HMOR zeolite), liquid-oil yields of 60.8% for PP and 87.3% for HDPE were achieved, accompanied by high energy densities (44.2 MJ/kg, RON 97.5 for PP; 43.7 MJ/kg, RON 115.2 for HDPE). These values significantly surpass those typically reported for uncatalyzed pyrolysis, demonstrating the efficacy of HMOR in directing product selectivity toward valuable liquids. Above 400 °C, the process undergoes a pronounced shift toward gas generation, with gas fractions exceeding 50 wt % by 441 °C, underscoring the critical influence of temperature on product distribution. Gas-phase analysis revealed that PP-derived syngas contains primarily methane (20%) and ethylene (19.5%), whereas HDPE-derived gas features propylene (1.9%) and hydrogen (1.5%), highlighting intrinsic differences in bond-scission pathways governed by polymer architectures. Aspen Plus process simulations, calibrated against experimental data, reliably predict product distributions with deviations below 20%, offering a rapid, cost-effective tool for reactor design and scale-up. Complementary density functional theory (DFT) calculations elucidate the temperature-dependent energetics of C–C bond cleavage and radical formation, revealing that system entropy increases sharply at 500–550 °C, favoring the generation of both liquid and gaseous intermediates. By directly correlating catalyst acidity, molecular reaction mechanisms, and process-scale performance, this study fills a critical gap in plastic-waste valorization research. The resulting predictive platform enables rational design of catalysts and operating conditions for circular economy applications, paving the way for scalable, efficient recovery of fuels and chemicals from mixed polyolefin waste. Full article

The selective hydrogenation of the C=O bond over the C=C bond in α,β-unsaturated aldehydes remains a well-known challenge. This work investigates the liquid-phase catalytic transfer hydrogenation of crotonaldehyde to crotyl alcohol over ReOx-based catalysts, using formic acid (FA) as an in situ hydrogen donor. A series of 10 wt% Re catalysts supported on G200, g-C₃N₄, TiO₂, and ZrO₂ were synthesized and tested in a batch reactor at 20 bar and temperatures of 140–180 °C. Catalysts were characterized by XRD, BET, NH₃-TPD, and XPS to correlate their physicochemical properties with catalytic behavior. Among the studied materials, ReO_x/ZrO₂ and ReO_x/g-C₃N₄ exhibited the highest crotyl alcohol selectivity above 57% for all reaction temperatures, evaluated at crotonaldehyde conversion of 25%. The nature of the support strongly influenced the dispersion and oxidation state of Re species, as well as the surface acidity, which governed the activation of both the carbonyl group and the FA decomposition. Compared with molecular hydrogen, FA improved both conversion and selectivity due to its superior hydrogen-donating ability in the aqueous phase. These findings demonstrate that tailoring the acid–base characteristics of ReO_x catalysts and employing biomass-derived hydrogen donors represent an effective strategy for selective hydrogenation of α,β-unsaturated aldehydes. Full article

This review summarizes the recent developments in titanium suboxide (TSO) doping and the application of doped materials in pollutant degradation and electrochemistry. Doping is mainly limited to transition and rare-earth metals, with some exceptions, of similar ionic radii and charge, that can replace Ti ions in TSO without too much disturbance to the lattice. Consequently, doping is limited to below 10 at%, which predominantly induces oxygen vacancy formation. Doping mechanisms are weighted, and their effect on conductivity, stability, and catalytic activity is overviewed. High-temperature H₂ reduction of TiO₂ is still the dominant preparation method, with carbothermal reduction and Ti reduction gaining ground due to safety and energy concerns. Doping predominantly increases the conductivity 2–5 times, while the stability can be both improved or worsened, depending on the size and charge of the doping ion. Electrochemical oxidation, at positive overpotentials, of per- and polyfluoroalkyl substances (PFAS), antibiotics, and other water pollutants, is the main avenue of application. Doping almost exclusively leads to complete selected pollutant degradation and improvement of the pristine TSO, which is summarized in detail. New niche applications of peroxide, hydrogen, and chlorine production are also viable on doped TSO and are touched upon. Complementing experimental results are theoretical calculations, and we give an overview of density functional theory (DFT) results of transition metal-doped TSOs, identifying active centers, degradation trends, and potential new doping candidates. Full article

The design of sustainable nanomaterials for catalysis is a key challenge in green chemistry. Herein, we report the synthesis of halloysite nanotube (Hal)-based nanomaterials selectively functionalized with a bio-inspired polydopamine (PDA) coating, which enables the controlled anchoring of palladium and copper nanoparticles (PdNPs and CuNPs). This mild and ecofriendly strategy yields highly dispersed and ultrasmall (<5 nm) metal nanoparticles without the need for surfactants or harsh reagents. The resulting materials, Hal@PDA/PdNPs and Hal@PDA/CuNPs, were evaluated in two well-established model reactions commonly employed to probe catalytic performance: cinnamaldehyde hydrogenation and 4-nitrophenol reduction. Hal@PDA/PdNPs displayed complete conversion and >90% selectivity toward hydrocinnamaldehyde at low Pd loading (0.8 wt%) and maintained its efficiency over six catalytic cycles (TOF up to 0.1 s⁻¹), while Hal@PDA/CuNPs retained high activity through eight consecutive runs in the reduction of 4-nitrophenol. Hal@PDA/CuNPs proved to be an excellent recyclable catalyst for the reduction of 4-nitrophenol, retaining high activity through eight consecutive runs. Overall, this study introduces a robust and modular approach to fabricating halloysite-based nanocatalysts, demonstrating their potential as green platforms for metal nanoparticle-mediated transformation. Full article

The growing demand for air connectivity, coupled with the forecasted increase in passengers by 2040, implies an exigency in the aviation sector to adopt sustainable approaches for net zero emission by 2050. Sustainable Aviation Fuel (SAF) is currently the most promising short-term solution; however, ensuring its overall sustainability depends on reducing the life cycle carbon footprints. A key challenge prevails in hydrogen usage as a reactant for the approved ASTM routes of SAF. The processing, conversion and refinement of feed entailing hydrodeoxygenation (HDO), decarboxylation, hydrogenation, isomerisation and hydrocracking requires substantial hydrogen input. This hydrogen is sourced either in situ or ex situ, with the supply chain encompassing renewables or non-renewables origins. Addressing this hydrogen usage and recognising the emission implications thereof has therefore become a novel research priority. Aside from the preferred adoption of renewable water electrolysis to generate hydrogen, other promising pathways encompass hydrothermal gasification, biomass gasification (with or without carbon capture) and biomethane with steam methane reforming (with or without carbon capture) owing to the lower greenhouse emissions, the convincing status of the technology readiness level and the lower acidification potential. Equally imperative are measures for reducing hydrogen demand in SAF pathways. Strategies involve identifying the appropriate catalyst (monometallic and bimetallic sulphide catalyst), increasing the catalyst life in the deoxygenation process, deploying low-cost iso-propanol (hydrogen donor), developing the aerobic fermentation of sugar to 1,4 dimethyl cyclooctane with the intermediate formation of isoprene and advancing aqueous phase reforming or single-stage hydro processing. Other supportive alternatives include implementing the catalytic and co-pyrolysis of waste oil with solid feedstocks and selecting highly saturated feedstock. Thus, future progress demands coordinated innovation and research endeavours to bolster the seamless integration of the cutting-edge hydrogen production processes with the SAF infrastructure. Rigorous techno-economic and life cycle assessments, alongside technological breakthroughs and biomass characterisation, are indispensable for ensuring scalability and sustainability. Full article

Understanding the role of synthesis parameters in tailoring catalyst morphology is crucial for enhancing performance in electrochemical water splitting. This research systematically explores how different solvent environments affect the structural evolution and morphology of cobalt-doped nickel sulfide (Co-Ni₃S₂) nanomaterials. By systematically modifying the solvent environment using ethylene glycol and glycerol, distinct morphologies of Co-Ni₃S₂ were obtained, leading to variations in their electrocatalytic water-splitting performance. The fabricated compounds were thoroughly tested for their catalytic performance in facilitating hydrogen and oxygen evolution processes. Notably, the use of ethylene glycol as a synthesis medium led to the formation of a unique interconnected petal-like structure, significantly improving electrocatalytic activity, as evidenced by low overpotentials of 190.7 mV for HER at 10 mA cm⁻² and 414 mV for OER at 30 mA cm⁻². In contrast, when glycerol was employed as the solvent, the resulting Co-Ni₃S₂ material displayed overpotentials of 223.8 mV and 535 mV for HER and OER, respectively. Eventually, Co-doping was found to enhance the electrocatalytic performance, as pure Ni₃S₂ synthesized under the same solvent conditions exhibited higher overpotentials for both HER and OER. These findings underscore the crucial role of solvent selection in tailoring the structural and functional properties of materials for high-performance electrochemical applications. Full article

Ammonia is an ideal candidate for clean energy in the future, and its large-scale production has long relied on the Haber–Bosch process, which operates at a high temperature and pressure. However, this process faces significant challenges due to the growing demand for ammonia and the increasing need for environmental protection. The high energy consumption and substantial CO₂ emissions associated with the Haber–Bosch method have greatly limited its application. Consequently, increasing research efforts have been devoted to developing green ammonia synthesis technologies. Among these, the electrocatalytic nitrogen reduction reaction (NRR), which uses water and nitrogen as raw materials to synthesize NH₃ under mild conditions, has emerged as a promising alternative. This method offers the potential for carbon neutrality and decentralized production when coupled with renewable electricity. However, it is important to note that the current energy efficiency and ammonia production rates of NRR under ambient aqueous conditions generally lag behind those of modern Haber–Bosch processes integrated with green hydrogen (H₂). As the core of the NRR process, the performance of electrocatalysts directly impacts the efficiency, energy consumption, and product selectivity of the entire reaction. To date, significant efforts have been made to identify the most suitable electrocatalysts. In this paper, we focus on the current research status of metal catalysts—including both precious and non-precious metals—as well as non-metal catalysts. We systematically review important advances in performance optimization, innovative design strategies, and mechanistic analyses of various catalysts. We clarify innovative optimization strategies for different catalysts and summarize and compare the catalytic effects of various catalyst types. Finally, we discuss the challenges facing electrocatalysis research and propose possible future development directions. Through this paper, we aim to provide guidance for the preparation of high-efficiency NRR catalysts and the future industrial application of electrochemical ammonia synthesis. Full article

This article reviews recent advances in heterogeneous hydroformylation, with a particular focus on rhodium-based catalysts supported on oxide surfaces. The hydroformylation reaction is a vital industrial process for producing aldehydes from petrochemicals. This reaction involves the addition of carbon monoxide (CO) and hydrogen (H₂) to alkenes, resulting in the formation of aldehydes. Aldehydes serve as essential building blocks for various downstream products in the chemical industry, including alcohols, esters, and amines. Although homogeneous catalysts such as rhodium complexes coordinated with phosphorus-based ligands (e.g., [RhCl(PPh₃)₃]) are highly active and selective, their separation and recovery remain significant challenges. This has fueled growing interest in the development of heterogeneous catalysts, which offer advantages in terms of sustainability, reusability, and catalyst recovery. This review highlights recent progress in the design of heterogeneous hydroformylation catalysts, with emphasis on rhodium-based systems on oxide supports. Key challenges and emerging strategies for enhancing catalytic performance and stability are also discussed. Full article

Nickel phosphide catalysts (Ni₂P) were prepared using mesoporous molecular sieves as supports during isobaric co-impregnation. Ni₂P catalysts with different loading values were characterized, showing that the active phase on the surface of the catalysts was mainly Ni₂P and the catalysts still retained the mesoporous structural characteristics of the supports. The catalysts were evaluated using a 10 mL fixed-bed hydrogenation unit. The results showed that the nickel phosphide catalysts had a higher hydrogenation capacity than the sulfide catalysts and were able to preferentially hydrogenate and saturate most of the quinolines to decahydroquinolines, reduce the conversion of 1,2,3,4-tetrahydroquinoline to o-propylaniline, and reduce the inhibition of reactivity due to competitive adsorption. The effect of the catalyst on the path selectivity of quinoline hydrogenation was investigated, and the products of quinoline hydrogenation and denitrogenation consisted mainly of propylbenzene and propylcyclohexane, with propylcyclohexane accounting for 91.7% of the product and propylbenzene for 4.8%, under the conditions of nickel phosphide catalysts. Furthermore, the 25 wt% Ni₂P/SBA-15 catalyst exhibited no significant loss of catalytic activity during a 72 h stability evaluation conducted at 360 °C. Full article

Developing bifunctional electrocatalysts that simultaneously enable green hydrogen production and water purification is essential for advancing sustainable energy and environmental technologies. In this study, we present Cu@Pd core–shell nanostructures fabricated through template-assisted electrodeposition of Cu, followed by galvanic Pd modification on pyrolytic graphite electrodes (PGEs). The optimised catalyst exhibited superior hydrogen evolution reaction (HER) activity, with an onset potential of 70 mV, a low Tafel slope of 33 mV dec⁻¹ and excellent stability during prolonged HER operation. In addition to hydrogen evolution, Cu@Pd/PGE shows significantly enhanced nitrate reduction reaction (NRR) activity compared to Cu/PGE in both alkaline and neutral conditions. Under ideal conditions, the catalyst achieved 60% nitrate removal with high selectivity towards ammonia and minimal nitrite formation, emphasising its superior performance. This enhanced bifunctionality arises from the synergistic Cu–Pd interface, facilitating efficient nitrate adsorption and selective hydrogenation. Despite their high catalytic activity for both HER and NRR, the Cu@Pd nanostructures could often emerge as a versatile platform for integration into sustainable hydrogen production and an effective denitrification process. Full article

CO₂ hydrogenation to methanol has attracted considerable attention as a promising catalytic route for both reducing CO₂ emissions and producing valuable chemical intermediates. Among various catalysts, Cu–ZnO-based systems are the most widely studied; however, their performance remains constrained by limited methanol selectivity and stability, highlighting the need for improved catalytic strategies. In this work, liquid metal gallium (Ga) was incorporated into Cu–ZnO catalysts as an additive for CO₂ hydrogenation to methanol. Owing to its high dispersibility and fluidity, Ga helps maintain long-term catalyst stability. We investigated different introduction methods for Ga promoters and found that the physical mixing approach generated the strongest alkaline sites, thereby enhancing CO₂ activation and increasing the CO₂ conversion to methanol. Moreover, this catalyst effectively suppressed carbon deposition, further improving its stability. These findings offer new insights into the use of liquid metal Ga in CO₂ hydrogenation and provide fresh perspectives for the rational design of efficient methanol synthesis catalysts. Full article

Methane pyrolysis produces hydrogen (H₂) with solid carbon black as a co-product, eliminating direct CO₂ emissions and enabling a low-carbon supply when combined with renewable or low-carbon heat sources. In this study, we propose a hybrid geothermal pyrolysis configuration in which an enhanced geothermal system (EGS) provides base-load preheating and isothermal holding, while either electrical or solar–thermal input supplies the final temperature rise to the catalytic set-point. The work addresses four main objectives: (i) integrating field-scale geothermal operating envelopes to define heat-integration targets and duty splits; (ii) assessing scalability through high-pressure reactor design, thermal management, and carbon separation strategies that preserve co-product value; (iii) developing a techno-economic analysis (TEA) framework that lists CAPEX and OPEX, incorporates carbon pricing and credits, and evaluates dual-product economics for hydrogen and carbon black; and (iv) reorganizing state-of-the-art advances chronologically, linking molten media demonstrations, catalyst development, and integration studies. The process synthesis shows that allocating geothermal heat to the largest heat-capacity streams (feed, recycle, and melt/salt hold) reduces electric top-up demand and stabilizes reactor operation, thereby mitigating coking, sintering, and broad particle size distributions. High-pressure operation improves the hydrogen yield and equipment compactness, but it also requires corrosion-resistant materials and careful thermal-stress management. The TEA indicates that the levelized cost of hydrogen is primarily influenced by two factors: (a) electric duty and the carbon intensity of power, and (b) the achievable price and specifications of the carbon co-product. Secondary drivers include the methane price, geothermal capacity factor, and overall conversion and selectivity. Overall, geothermal-assisted methane pyrolysis emerges as a practical pathway to turquoise hydrogen, if the carbon quality is maintained and heat integration is optimized. The study offers design principles and reporting guidelines intended to accelerate pilot-scale deployment. Full article

Aromaticity tuning of biaryl monophosphines can significantly impact their catalytic performance. Biaryl monophosphines constitute a crucial class of compounds due to their potential as ligand precursors in asymmetric Pd-catalyzed cross-coupling and some other catalytic reactions. In this study, we investigate the tuning of aromaticity within a series of selected biaryl monophosphine derivatives exhibiting diverse steric and electronic properties. XRD structures and Hirshfeld surface analyses were complemented by DFT calculations. Aromaticity indices, such as geometric HOMA, HOMER, and magnetic NICS, were evaluated and correlated with ligand properties. NICS(1)zz was the most sensitive to aromaticity changes. The results showed that among the ring-activating substituents, methoxy groups were more beneficial than hydroxy ones. The hydroxy groups not only modulated the aromaticity but also induced unfavorable conformational changes of the catalyst precursors through strong inter- and intramolecular hydrogen bonding. The spatial arrangement of the P atom adjacent to the aryl ring system confers catalytic advantages by promoting the assembly of coordination compounds (catalysts) in which Pd—C bond formation occurs, yielding C,P-chelated five-membered palladacyclic structures. The hydroxy substituents blocked access to the P atom, thereby hindering catalytic performance. The studies show that even subtle changes in the monophosphine biaryl scaffold, especially aromaticity tuning should be carefully evaluated during the rational design of new efficient catalysts. The studied compounds were evaluated for their biological activity against three Gram-positive and four Gram-negative bacteria as model microorganisms. The research was supplemented by in vitro cytotoxicity evaluation. Full article

Given the limitations of clinical and potent natural α-glucosidase inhibitors, novel selective inhibitors are urgently needed. To accelerate discovery, we employed machine learning-integrated virtual screening to rapidly evaluate a library of 100 K⁺ compounds, identifying a series of selective α-glucosidase inhibitors. Activity validation demonstrated that these inhibitors exhibit significantly enhanced selectivity and potency compared to the positive control acarbose. Mechanistic studies through inhibition kinetics and fluorescence quenching revealed their improved inhibitory profile. Molecular docking indicates that key interactions—hydrogen bonding or salt bridges with the catalytic residue ASP526—strengthen binding within the active site. These interactions competitively obstruct enzyme-substrate binding, thereby amplifying inhibition. In vitro and in vivo starch digestion assays further corroborated these findings. Full article

The chemical looping steam reforming of methane (CLSR) employing Fe-containing oxygen carriers can produce syngas and hydrogen simultaneously. However, Fe-based oxygen carriers exhibit low CH₄ activation ability and cyclic stability. In this work, oxygen carriers with fixed Fe content and different Fe/Ni ratios were synthesized by the sol–gel method to investigate the effects of Ni-Fe-Al interactions on CLSR performance. Ni-Fe-Al interactions promote the growth of the spinel structure and regulate both the catalytic sites and the available lattice oxygen, resulting in the CH₄ conversion and CO selectivity being maintained at 96–98% and above 98% for the most promising oxygen carrier, with an Fe₂O₃ content of 20 wt% and Fe/Ni molar ratio of 10. The surface, phase, and particle size were kept the same over 90 cycles, leading to high stability. During the CLSR cycles, conversion from Fe³⁺ to Fe²⁺/Fe⁰ occurs, along with transformation between Ni²⁺ in NiAl₂O₄ and Ni⁰. Overall, the results demonstrate the feasibility of using spinel containing earth-abundant elements in CLSR and the importance of cooperation between oxygen release and CH₄ activation. Full article