Search Results (25)

Despite significant advancements in designing tandem catalysts for CO₂ hydrogenation to aromatics, the role of zeolite acid property in regulating the selectivity of light aromatics (benzene, toluene, and xylene, abbreviated as BTX) remains unclear. Herein, we report H-ZSM-5 zeolite (denoted as HZ-X, where X represents the Si/Al ratio) integrated with a Na-promoted FeCo-based catalyst (NaFeCo) for CO₂ hydrogenation into aromatics via a modified Fischer–Tropsch synthesis pathway. This study systematically modulates the Si/Al ratio of acidic zeolite and examines its critical role in influencing the light aromatics selectivity. The optimized NaFeCo/HZ-50 catalyst achieves a CO₂ conversion of 43% with an aromatics selectivity of 41%, including a BTX fraction of 57% in total aromatics. Multiple characterization techniques (NH₃-TPD, Py/DTBPy-IR, ²⁷Al NMR, etc.) clarify that acidic zeolite HZ-50 exhibits appropriate acid density and lower external surface acid sites, which synergistically boost the efficient aromatics and BTX synthesis while suppressing the undesirable alkylation and isomerization reactions on the external acid sites. This work develops a highly efficient multifunctional catalyst for CO₂ hydrogenation to light aromatics, especially offering guidance for the rational design of acidic zeolite with unique shape-selective functions. Full article

The present study investigates the catalytic conversion of low-density polyethylene (LDPE) into high-grade fuel oil using a semi-batch reactor at 350 °C under ambient pressure, with a catalyst-to-LDPE ratio of 1:20. Zeolite-based catalysts were synthesized by impregnating different metals (Fe, Zn, Cr, Mn, and Ga) onto ZSM-5 with a silica-to-alumina ratio of 30 (Z30). These catalysts were characterized using BET, XRD, and NH3-TPD techniques to evaluate their physicochemical properties. The results showed that catalytic pyrolysis of LDPE yielded less pyrolytic oil compared to non-catalytic pyrolysis. The obtained pyrolytic oil was analysed through elemental composition, gross calorific value (GCV), Simulated Distillation, and GC-DHA. The elemental analysis revealed a high carbon (85–86%) and hydrogen (13–14%) content, resulting in a high GCV of approximately 42 MJ/kg. GC-DHA analysis indicated that the pyrolytic oil was rich in aromatic and olefinic compounds. Among the catalysts, 5Fe/Z30 exhibited the highest aromatic selectivity (35%), a research octane number of 91, and 100% LDPE conversion. These findings underscore the potential of low-cost iron-based catalysts for efficiently converting LDPE waste into valuable chemicals and fuels. Full article

In response to the increasing global demand for sustainable energy alternatives, this research explores the efficient conversion of sugarcane bagasse to bio-oil through hydrothermal liquefaction (HTL) processes with modified Zeolite Socony Mobil-5 catalysts (ZSM-5). The study systematically investigates the impact of feedstock quantity, reaction temperature, duration, and catalyst loading on bio-oil yield and quality. Optimisation experiments revealed that a feedstock amount of 10 grammes, an HTL temperature of 340 °C for 60 min and a ZSM-5 catalyst loading of 3 grammes resulted in the highest bio-oil yield. Furthermore, the introduction of Ni and Fe metals to ZSM-5 exhibited enhanced catalytic activity without compromising the structure of the zeolites. Comprehensive characterisation of modified catalysts using SEM-EDS, XRD, TGA, TEM, and FTIR provided insight into their structural and chemical properties. The successful incorporation of Ni and Fe into ZSM-5 was confirmed, highlighting promising applications in hydrothermal liquefaction. Gas chromatography–mass spectrometry (GC-MS) analysis of bio-oils demonstrated the effectiveness of the 2% Fe/ZSM-5 catalyst, highlighting a significant increase in hydrocarbon content. FTIR analysis of the produced bio-oils indicated a reduction in functional groups and intensified aromatic peaks, suggesting a shift in chemical composition favouring aromatic hydrocarbons. This study provides valuable information on HTL optimisation, catalyst modification, and bio-oil characterisation, advancing the understanding of sustainable biofuel production. The findings underscore the catalytic prowess of modified ZSM-5, particularly with iron incorporation, in promoting the formation of valuable hydrocarbons during hydrothermal liquefaction. Full article

CO₂ oxidative dehydrogenation of propane (CO₂-ODHP), being not only favorable for olefin production but also beneficial for CO₂ emission control, has recently attracted great attention. Here, a series of single metal (Cr) and bimetal (Zr, La, Fe) modified ZSM-5 zeolites were prepared via an impregnation method. It was found that the bimetal modified ZSM-5 possessed much higher C₃H₈ and CO₂ conversion than that of monometallic modified Cr_3%-ZSM-5 (Cr_3%-Z5), especially for Cr_3%Zr_2%-ZSM-5 (Cr_3%Zr_2%-Z5), which displayed the highest activity (65.4%) and olefin yield (1.65 × 10³ μmol·$g_{cat}^{-1}$ h⁻¹). Various characterizations were performed, including XRD, N₂ adsorption-desorption, H₂-TPR, Raman, XPS, HAAD-STEM, and TEM. It was revealed that Zr not only favored an improvement in the redox ability of Cr, but also contributed to the surface dispersion of loaded Cr species, constituting two major reasons explaining the superior activity of Cr_3%Zr_2%-Z5. To further improve CO₂-ODHP catalytic behavior, a series of Cr_3%-ZSM-5@SBA-15-n composite zeolite catalysts with diverse (ZSM-5/SBA-15) mass ratios were prepared (Cr_3%-ZS-n, n = 0.5, 2, 6, 16), which screened out an optimum mass ratio of six. Based on this, the Cr_3%Zr_2%-ZS-6 compound was further prepared, and it eventually achieved even higher CO₂-ODHP activity (76.9%) and olefin yield (1.72 × 10³ μmol·$g_{cat}^{-1}$ h⁻¹). Finally, the CO₂-ODHP reaction mechanism was further investigated using in situ FTIR, and it was found that the reaction followed the Mars–van Krevelen mechanism, wherein CO₂ participated in the reaction through generation of polydentate carbonates. The Cr⁶⁺ constituted as the active site, which was reduced to Cr³⁺ after the dihydrogen reaction, and was then further oxidized into Cr⁶⁺ by CO₂, forming polydentate carbonates, and thus cycling the reactive species Cr⁶⁺. Additionally, assisted by a Brönsted acid site (favoring breaking of the C-C bond), C₂H₄ and CH₄ were produced. Full article

Nitrous oxide (N₂O) is an industrial waste gas (e.g., from the production of adipic acid), which damages the ozone layer and causes the greenhouse effect. Density functional theory calculations were employed to investigate the mechanism of direct catalytic decomposition of N₂O and selective catalytic reduction (SCR) of N₂O by CO over Fe-ZSM-5 zeolites. Two stable Fe-active sites with six-membered ring structures on Fe-ZSM-5 were considered. The calculations indicate that the decomposition of N₂O is affected by the coordination environment around Fe and can occur through two reaction pathways. However, there is invariably a more considerable energy hurdle for the initiation of the second stage of N₂O decomposition. When CO participated in the reaction, it showed good reactivity and stability, the reaction energy barriers of the rate-limiting step were reduced by roughly 20.57 kcal/mol compared to the direct catalytic decomposition of N₂O. CO exhibited a superior electron-donating ability and orbital hybridization performance during the reaction, which enhanced the cyclicity of the N₂O reduction catalytic process. Our calculations confirmed the significant role of CO in N₂O reduction over Fe-ZSM-5 observed in previous studies. This study provides a valuable theoretical reference for exploring CO-SCR methods for N₂O reduction over Fe-based zeolite catalysts. Full article

This study aims to investigate the catalytic co-pyrolysis of beech wood with polystyrene as a synergic and catalytic effect on liquid oil production. For this purpose, a tubular semi-continuous reactor under an inert nitrogen atmosphere was used. Several zeolite catalysts were modified via incipient wetness impregnation using iron and/or nickel. The liquid oil recovered was analyzed using GC-MS for the identification of the liquid products, and GC-FID was used for their quantification. The effects of catalyst type, beechwood-to-polystyrene ratio, and operating temperature were investigated. The results showed that the Fe/Ni-ZSM-5 catalyst had the best deoxygenation capability. The derived oil was mainly constituted of aromatics of about 92 wt.% for the 1:1 mixture of beechwood and polystyrene, with a remarkably high heating value of around 39 MJ/kg compared to 18 MJ/kg for beechwood-based bio-oil. The liquid oil experienced a great reduction in oxygen content of about 92% for the polystyrene–beechwood 50-50 mixture in comparison to beechwood alone. The catalytic and synergetic effects were more realized for high beechwood percentages as a 75-25 beechwood–polystyrene mix. Regarding the temperature variation between 450 and 600 °C, the catalyst seemed to deactivate faster at higher temperatures, thus constituting a quality reduction in the pyrolytic oil in high-temperature ranges. Full article

The catalytic activity of the binary composite catalysts of Fe₂O₃-CoO/CaA and Fe₂O₃-CoO/ZSM-5 was studied. They were obtained by impregnation of CaA and ZSM-5 zeolites with aqueous solutions of sulfates of iron (FeSO₄·7H₂O) and cobalt (CoSO₄·7H₂O). The total metal content was no more than 5%. Then, oxidizing burning at 720 °C for 60 min was performed to produce the metal oxides. It was found that the obtained Fe-Co/CaA catalyst contains iron and cobalt as CoFe₂O₄ compound, and the Fe-Co/ZSM-5 catalyst includes CoFe₂O₄ and CoFe. The phase composition of the obtained catalysts was detected by the X-ray diffraction analysis. The surface morphology was investigated by the electron microscopy. The elemental composition of the obtained catalysts was determined by energy dispersive spectroscopy with mapping and inductively coupled plasma atomic emission spectroscopy. The atomic absorption analysis by the IR-spectroscopy showed the shifts of absorption bands in the infrared spectra of the pure zeolites and with added Fe and Co. The catalytic hydrogenation of anthracene was performed to determine the catalytic properties of the obtained catalysts. It is one of the most common model compounds applied to investigate the efficiency of catalytic systems. The result of hydrogenation found that conversion of anthracene at 400 °C, initial pressure of 6 MPa and duration of 60 min using the Fe-Co/CaA catalytic system equaled to ~87%. However, hydrogenation products equaled to ~84%. Anthracene conversion using the Fe-Co/ZSM-5 catalytic system and the same conditions was ~91%; among them, hydrogenated derivatives were ~71%. The proposed method is characterized by its simple execution. The obtained catalysts are be slightly inferior to platinum and rhodium catalysts in the catalytic activity. Full article

Adsorption of toxic compounds from water using zeolites and magnetite was developed due to the various advantages of their applicability. In the last twenty years, the use of zeolite-based compositions in the form of zeolite/inorganic or zeolite/polymer and magnetite has been accelerated for the adsorption of emergent compounds from water sources. The main adsorption mechanisms using zeolite and magnetite nanomaterials are high surface adsorption, ion exchange capacity and electrostatic interaction. This paper shows the capacity of Fe₃O₄ and ZSM-5 nanomaterials of adsorbing the emerging pollutant acetaminophen (paracetamol) during the treatment of wastewater. The efficiencies of the Fe₃O₄ and ZSM-5 in the wastewater process were systematically investigated using adsorption kinetics. During the study, the concentration of acetaminophen in the wastewater was varied from 50 to 280 mg/L, and the maximum Fe₃O₄ adsorption capacity increased from 25.3 to 68.9 mg/g. The adsorption capacity of each studied material was performed for three pH values (4, 6, 8) of the wastewater. Langmuir and Freundlich isotherm models were used to characterize acetaminophen adsorption on Fe₃O₄ and ZSM-5 materials. The highest efficiencies in the treatment of wastewater were obtained at a pH value of 6. Fe₃O₄ nanomaterial presented a higher removal efficiency (84.6%) compared to ZSM-5 nanomaterial (75.4%). The results of the experiments show that both materials have a potential to be used as an effective adsorbents for the removal of acetaminophen from wastewater. Full article

The synthesis of gasoline-range hydrocarbons by gas-phase dimethyl ether (DME) conversion was investigated on various ZSM-5 zeolites with different morphologies and Fe contents. The different morphologies of ZSM-5 significantly altered the distributions of the acidic sites, which showed different selectivities to gasoline-range hydrocarbons. Nanostructured ZSM-5 (N-ZSM-5) revealed the highest C₅₊ selectivity of 41.7% with an aromatics selectivity of 23.6% at ~100% DME conversion. The superior catalytic activity of N-ZSM-5 was attributed to the largest strong Brønsted acidic sites and smaller crystallite sizes, which were beneficial for the faster removal rate of heavy hydrocarbons due to its shorter diffusion pathlength compared to conventional ZSM-5 (C-ZSM-5). In addition, 10 wt% Fe-impregnated N-ZSM-5 revealed an enhanced C₅₊ selectivity of 60.6% with a smaller C₁–C₄ selectivity of 21.9%, which were attributed to the adjusted acidic sites by suppressing the cracking reactions of the surface intermediates, which are responsible for the selective formation of smaller light hydrocarbons. However, the excess amount of Fe on N-ZSM-5 showed a lower DME conversion of 83.5% with a lower C₅₊ selectivity of 38.5% due to the blockages of the active acidic sites. Nanostructured N-ZSM-5 possessing a larger amount of strong Brønsted acid sites with 10 wt% Fe modification clearly showed a higher formation rate of gasoline-range hydrocarbons due to an enhanced secondary oligomerization of surface intermediates to form heavier aromatic hydrocarbons. Full article

N₂O is a greenhouse gas and a candidate oxidant. Volatile organic pollutants (VOCs) have caused great harm to the atmospheric ecological environment. Developing the technique utilizing N₂O as the oxidant to oxidize VOCs to realize the collaborative purification has significant importance and practical value for N₂O emission control and VOC abatement. Therefore, the study of N₂O catalytic oxidation of tert-butanol based on zeolite catalysts was carried out. A series of molecular sieves, including FER, MOR, ZSM-5, Y, and BEA, were selected as the catalyst objects, and the 1.5% wt Fe and Co were, respectively, loaded on the zeolite catalysts via the impregnation method. It was found that the catalytic performance of BEA was the best among the molecular sieves. Comparing the catalytic performance of Fe-BEA under different load gradients (0.25~2%), it was found that 1.5% Fe-BEA possessed the best catalytic activity. A series of characterization methods showed that Fe³⁺ content in 1.5% Fe-BEA was the highest, and more active sites formed to promote the catalytic reaction. The α-O in the reaction eventually oxidized tert-butanol to CO₂ over the active site. The Co mainly existed in the form of Co²⁺ cations over Co-BEA samples; the 2% Co-BEA possessing higher amounts of Co²⁺ exhibited the highest activity among the prepared Co-BEA samples. Full article

Transition-metal-modified zeolites have recently gained the greatest interest among scientists. Ab initio calculations within the density functional theory were used. The exchange and correlation functional was approximated with the Perdew–Burke–Ernzerhof (PBE) functional. Cluster models of ZSM-5 (Al₂Si₁₈O₅₃H₂₆) zeolites were used with Fe particles adsorbed above aluminum. The adsorption of three iron adsorbates inside the pores of the ZSM-5 zeolite—Fe, FeO and FeOH—was carried out with different arrangements of aluminum atoms in the zeolite structure. The DOS diagram and the HOMO, SOMO and LUMO molecular orbitals for these systems were analyzed. It has been shown that depending on the adsorbate and the position of aluminum atoms in the pore structure of the zeolite, the systems can be described as insulators or conductors, which significantly affects their activity. The main aim of the research was to understand the behavior of these types of systems in order to select the most efficient one for a catalytic reaction. Full article

Nickel-supported hierarchical zeolite catalysts were prepared through a desilication reassembly process under optimized conditions and applied in one-pot menthol synthesis. In this work, the hierarchical zeolite-supported metal bifunctional catalysts were prepared with the help of desilication re-assembly and wetness impregnation techniques and applied in menthol synthesis via citral hydrogenation. The prepared catalysts were characterized using PXRD, BET, FE-TEM, NH₃-TPD, H₂-TPR, pyridine adsorption, and ICP-OES techniques. As a result, the physicochemical and acidic properties, such as mesopore surface area, metal dispersion, acidity, catalytic activity, and strong Lewis acid sites of pure microporous ZSM-5/USY zeolites, were significantly improved. Consequently, with the occurrence of superior physicochemical and acidic properties, the Ni/HZ-0.5 M catalyst exhibited outstanding catalytic activity (100% conversion, TOF 7.12 h⁻¹) and menthol selectivity (83%, 4 h) with uniform stability at 100 °C, 1.0 MPa hydrogen. Similarly, the cracking rate decreased with the decrease in Bronsted acid sites. Full article

The catalytic fast pyrolysis (CFP) of bio-derived furans offers a promising approach for sustainable aromatic production. ZSM-5 modified by different metal species (Zn, Mo, Fe, and Ga) was employed in the CFP of bio-derived furans for enhancing aromatic production. The effects of metal species, metal loadings, and the weight hourly space velocity (WHSV) on the product distributions from the CFP of 2-methylfuran (MF) were systemically investigated. It is found that the introduction of Zn, Mo, Fe, and Ga on ZSM-5 significantly increases the MF conversion and aromatic yields. The maximum MF conversions of 75.49 and 69.03% are obtained, respectively, by Fe-ZSM-5 and Ga-ZSM-5, which boost the aromatic yield by 34.5 and 42.7% compared to ZSM-5. The optimal loading of Fe on ZSM-5 is 2%. Additionally, the highest aromatic yield of 40.03% is achieved by 2%Fe-ZSM-5 at a WHSV of 2 h⁻¹. The catalyst characterization demonstrates that the synergistic effect of Brønsted and Lewis acid sites in Fe-ZSM-5 is responsible for achieving the efficient aromatization of MF. The key to designing improved zeolite catalysts for MF aromatization is the introduction of large numbers of new Lewis acid sites without a significant loss of Brønsted acid sites in ZSM-5. These findings can provide guidelines for the rational design of better zeolite catalysts used in the CFP of biomass and its derived furans. Full article

A WO₃/Fe-Cu-ZSM-5 catalyst was prepared using the solid state ion exchange method (SSIE) and its performance for the Selective Catalytic Reduction of NO with NH₃ (NH₃-SCR of NO) was investigated. The study shows that the tungsten addition can slightly improve the high temperature catalytic activity of Fe-Cu-ZSM-5. The influence of hydrothermal aging at 850 °C for 5 h on the structural and textural properties of WO₃/Fe-Cu-ZSM-5 was also studied in this paper. The XRD and FE-SEM measurements did not indicate a breakdown of the zeolite structure upon steam treatment for both aged catalysts. The aged W-base catalyst demonstrates a lower deactivation and better catalytic activity for NO reduction than the bimetallic catalyst after hydrothermal aging despite the lower acidic properties as shown by FTIR-Pyr spectroscopy owing to the presence of tungsten oxide crystallites. The “severe” stage of aging occurring in the absence of W led to the formation of copper oxide agglomerates detected using STEM and H₂-TPR techniques being responsible for the deterioration of SCR activity of the aged Fe-Cu-ZSM-5. Full article

Commercial separators (polyolefin separators) for lithium-ion batteries still have defects such as low thermostability and inferior interface compatibility, which result in serious potential safety distress and poor electrochemical performance. Zeolite/Polyacrylonitrile (Z/PAN) composite separators have been fabricated by electrospinning a polyacrylonitrile (PAN) membrane and then dip-coating it with zeolite (ZSM-5). Different from commercial separators, the Z/PAN composite separators exhibit high electrolyte uptake, excellent ionic conductivity, and prominent thermal stability. Specifically, the Z/PAN-1.5 separator exhibits the best performance, with a high electrolyte uptake of 308.1% and an excellent ionic conductivity of 2.158 mS·cm⁻¹. The Z/PAN-1.5 separator may mechanically shrink less than 10% when held at 180 °C for 30 min, proving good thermal stability. Compared with the pristine PAN separator, the Li/separator/LiFePO₄ cells with the Z/PAN-1.5 composite separator have excellent high-rate discharge capacity (102.2 mAh·g⁻¹ at 7 C) and favorable cycling performance (144.9 mAh·g⁻¹ at 0.5 C after 100 cycles). Obviously, the Z/PAN-1.5 separator holds great promise in furthering the safety and performance of lithium-ion batteries. Full article