Search Results (50)

This study presents a systematic approach for converting low-grade carbon derived from mining waste into functional carbon–zeolite composites with enhanced adsorption performance. To promote carbon deposition within and around zeolite frameworks, four industrially relevant zeolites, including zeolite socony mobil-5 (ZSM-5), Faujasite-type zeolite (Zeolite-Y), beta zeolite (Zeolite-β), and mordenite (MOR), were mechanically mixed with low-grade carbon under controlled stirring conditions (24 h at 250 rpm) and subsequently pyrolyzed at 800 °C. These treatments enabled a detailed assessment of structural stability and carbon–zeolite interactions. Scanning electron microscopy revealed pronounced modifications in surface morphology and carbon distribution after carbon treatment, while X-ray diffraction confirmed that the crystalline zeolite frameworks remained structurally intact despite the deposition of amorphous carbon. The adsorption performance of the resulting composites was evaluated through CO₂ adsorption measurements under controlled temperature and pressure conditions, demonstrating a clear enhancement relative to the pristine zeolites. Overall, this work highlights an effective strategy for valorizing low-grade carbon waste into high-performance carbon–zeolite hybrid adsorbents and provides new mechanistic insights into framework stability, selective atom removal, and carbon–zeolite interactions in high-temperature and acidic environments. Full article

A highly active Co/Beta catalyst was prepared via ion-exchange method, in which sodium cations in the beta zeolite framework were replaced by cobalt ions using an aqueous cobalt nitrate solution. Based on XRD, SEM, TEM, XPS, and nitrogen adsorption–desorption analyses, it was confirmed that cobalt species successfully took the place of sodium ions in beta zeolite, while the cobalt species diffused with a uniform dispersion. Strong electronic coupling between cobalt species and zeolite framework oxygen stabilizes Co²⁺ sites in the material. The catalysts perform high efficiency in dye Acid Orange II (AO7) degradation reactions, which gives more than 99.5% removal efficiency at room temperature and initial pH within 10 min under low catalyst dosage. The advantages of the Co/Beta catalyst are reasonably attributed to its maximized metal−zeolite synergistic efficiency. Full article

Zeolites are promising materials for volatile organic compound (VOC) adsorption and catalytic oxidation, where tuning their structure via defect engineering can enhance adsorption capacity and active metal dispersion. In this study, a concentration-sensitive chelation strategy using diethylenetriaminepentaacetic acid (DTPA) was developed to achieve moderate dealumination for Beta and Y zeolites. For Y zeolite, 0.1 M DTPA treatment increased the toluene adsorption capacity from 59 to 110 mg/g. After platinum (Pt) loading, both DTPA-modified Beta- and Y-based catalysts showed improved toluene oxidation efficiency compared to their unmodified counterparts. Remarkably, the Y-DTPA-0.01-Pt catalyst achieved 90% toluene conversion at 150 °C with CO₂ selectivity above 90%. DRIFTS and H₂-TPR results confirmed that moderate dealumination by DTPA generated silanol defects in zeolite Y that strongly anchored Pt²⁺ in a highly dispersed form and suppressed PtO formation. Severe dealumination using 0.1 M DTPA created larger defects that favored the aggregation of Pt⁰ clusters whilst causing significant loss in the micropores, thus reducing the Pt loading content and catalytic activity. This work demonstrates a simple and effective approach to optimize zeolite-based catalysts by controlling defect formation through controllable chelation, offering new insights into VOC abatement via tailored support design. Full article

Heparin, an essential plasma-derived therapy, acts as a naturally occurring anticoagulant and is essential in various physiological processes. Due to its complex structure, repeating units of sulfated glycosaminoglycan, it attracts attention in the field of commercial pharmaceuticals. In recent decades, significant advancements have been made in the development of economical adsorbents designed especially for the extraction of heparin from the intestinal mucosa of pigs, as evidenced by investments from various pharmaceutical industries. This requirement arises from the demand for efficient, scalable extraction methods for natural sources. In this study, we investigated the application of beta zeolites to increase the recovery of heparin from real porcine mucosa samples, emphasizing materials with greater adsorption surfaces, higher thermal stability, and increased porosity. According to our research, the zeolite CP814E’s macropores and huge surface area allow it to adsorb up to 20.6 mg·g⁻¹ (39%) of heparin from actual mucosa samples. We also investigated the adsorbent’s surface conditions, which are essential for efficient heparin recovery, and adjusted temperature and pH to enhance heparin uptake. These findings demonstrate that zeolite-based adsorbents can enhance the extraction of heparin effectively for use in medicinal applications. Full article

The aim of our work is to theoretically model the conversion of C6 and C5 carbohydrates derived from lignocellulosic biomass waste into C1–C5 carboxylic acids such as levulinic, oxalic, lactic, and formic acids. Understanding the mechanism of these processes will provide the necessary knowledge to better plan the structure of zeolite. In this article, we focus on the theoretical modeling of two carbohydrates, representing C5 and C6, namely xylose and fructose, into levulinic acid (LE) and formic acid (FA). The modeling was carried out with the participation of Na-BEA zeolite in a hierarchical form, due to the large size of the carbohydrates. The density functional theory (DFT) method (StoBe program) was used, employing non-local generalized gradient-corrected functions according to Perdew, Burke, and Ernzerhof (RPBE) to account for electron exchange and correlation and using the nudged elastic band (NEB) method to determine the structure and energy of the transition state. The modeling was performed using cluster representations of hierarchical Na-Al₂Si₁₂O₃₉H₂₃ and ideal Al₂Si₂₂O₆₄H₃₄ beta zeolite. However, to accommodate the size of the carbohydrate molecules in reaction paths, only hierarchical Na-Al₂Si₁₂O₃₉H₂₃ was used. Sodium ions were positioned above the aluminum centers within the zeolite framework. Full article

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to the confinement effect, the as-encapsulated nickel species appears in the form of Ni⁰ and Ni^δ+, which implies its feasibility in metal catalysis and coordination catalysis. In the study reported herein, we further explored the hydrogen production and olefin oligomerization performance of Ni₁@Beta-NO₃⁻. It was found that Ni₁@Beta-NO₃⁻ demonstrated a high H₂ generation turnover frequency (TOF) and low activation energy (E_a) in a sodium borohydride (NaBH₄) hydrolysis reaction, with values of 331 min⁻¹ and 30.1 kJ/mol, respectively. In ethylene dimerization, it exhibited a high butylene selectivity of 99.4% and a TOF as high as 5804 h⁻¹. In propylene oligomerization, Ni₁@Beta-NO₃⁻ demonstrated high selectivity (75.21%) of long-chain olefins (≥C₆⁺), overcoming the problem of cracking reactions that occur during oligomerization using H-Beta. Additionally, as a comparison, the influence of the metal precursor (NiCl₂) on the performance of the encapsulated Ni catalyst was also examined. This research expands the application scenarios of non-noble metal single-atom catalysts and provides significant assistance and potential for the production of H₂ from hydrogen storage materials and the production of valuable chemicals. Full article

Ruthenium-based catalysts were prepared through a deposition–precipitation approach, taking beta zeolites with Si/Al ratios of 12.5, 18.5, and 150, respectively, as supports, and 1–3 wt% loadings of metal. Their activation was performed in the presence of either H₂ or NaBH₄. The dispersion of the Ru species and the acid–base properties were influenced by both the preparation method and the activation protocol. The catalysts reduced under H₂ flow presented well-dispersed Ru(0) and RuO_x nanoparticles, while the reduction with NaBH₄ led to larger RuO_x crystallites and highly dispersed Ru(0). These characteristics exerted an important role in the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL). The H₂ dissociation occurred via a heterolytic mechanism involving Lewis acid–base pairs associated with RuO_x and the framework oxygen (Si-O-Al) located near the zeolite pore edge. The Ru(0) nanoparticles activated the –C=O bond of the LA substrate, while the presence of the carrier zeolite Brønsted acid sites promoted the ring-closure esterification of the 4-hydroxyvaleric acid (4-HVA) intermediate to GVL. An optimal combination of these features was achieved for the catalyst with 3 wt% Ru and a Si/Al ratio of 150, which selectively converted LA (X_LA = 96.5%) to GVL (S_GVL = 97.8%) at 130 °C and 10 bars of H₂. Full article

As an important biomass resource, γ-valerolactone (GVL) shows considerable potential for applications in biofuel production, organic synthesis, polymer, and food industries. Herein, an effective method was presented for synthesizing GVL through the catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) under mild conditions. Using isopropanol as a hydrogen donor, a 100% conversion of ethyl levulinate and an 88.7% yield of GVL were achieved over 2%Zr-Beta-7d catalyst at 110 °C for 8 h. The acidic sites of synthesized Zr-Beta via hydrothermal methods easily adjusted and offered high catalytic activity and selectivity. The Lewis (L) acid sites on the zeolite serve as the active centers for the conversion of EL. Characterization results indicate that the amounts of L acid sites on Zr-Beta increased with the Zr content and crystallization time rose, thus enhancing the selectivity for GVL. Additionally, the influences of catalyst dosage, reaction temperature, and time on catalytic performance are studied, as well as calculations of kinetic parameters such as reaction rate constants and activation energies. The 2%Zr-Beta-7d catalyst retains its high performance after five cycles. The current research may present an efficient approach for the conversion of EL to GVL under mild conditions. Full article

This article presents the conditions for the transformation of pulp containing mixtures that occur in the hemicellulose fraction derived from lignocellulosic biomass. Selected materials with strong acid centers were used as catalytic materials: ion exchange resins, including AMBERLYST 15(H) and DOWEX DR-G8(H), and selected zeolite in the hydrogen form of the Beta type (H-BEA). The group was marked with the abbreviations M1, M2 and M3, where it differs in the content of xylose, mannose, galactose, glucose, rhamnose and uronic acids. The catalytic process was carried out in the reactor as a one-pot technique at temperatures of 180–250 °C for 1–5 h. Based on the collected results, the transformation products of hemicellulose pulp were determined and the catalytic abilities of selected materials were determined. The proposed conditions led to the production of organic acids. Levulinic acid was obtained with a selectivity of 25.95% after 1 h of the process at a temperature of 250 °C with the participation of H-BEA, and lactic acid was obtained with a selectivity of 73.28% after 5 h of the process at a temperature of 250 °C using DOWEX DRG8(H). The presence of oxalic, propionic and acetic acids was also observed. Full article

Commercial NH₄-Beta and Na-ZSM-5 zeolites were fluorinated with different amounts of NH₄F and using different procedures (room temperature, conventional refluxing, microwave refluxing). Samples were characterized by XRD, N₂ physisorption, FTIR, ¹H NMR, SEM-EDS, and TGA of adsorbed cyclohexylamine. An increase in the concentration of NH₄F led to fluorinated zeolites with higher surface areas and slightly lower amounts of Brønsted acid sites due to some dealumination. Fluorination by conventional or microwave refluxing at shorter times did not dealuminate ZSM-5, resulting in the formation of higher particle sizes. Ni/fluorinated beta catalysts were more active than Ni/fluorinated ZSM-5 catalysts for the hydrodeoxygenation of guaiacol at 180 °C and 15 bar of H₂ for 1 h due to their higher amount of acid sites. The appropriate proportion of metallic and Brønsted acid centers allowed for the selective obtention of cyclohexane (58%) for the Ni supported on beta fluorinated with NH₄F 0.1 M catalyst. The combination of this fluorinated beta to a Ni/ordered mesoporous carbon catalyst significantly boosted its selectivity to cyclohexane from 0 to 65%. Fluorinated ZSM-5 samples, although having stronger Brønsted acid sites, as observed by ¹H NMR, they had lower amounts, leading to higher selectivity to cyclohexanol when used as catalytic supports. Full article

H-Beta zeolite is a solid acid catalyst commonly utilized in the catalytic conversion of biomass resources. In this study, H-Beta zeolite was calcined at different temperatures (350, 550, 750, and 1000 °C) to explore the effects of high temperature-induced dealumination on its physicochemical properties and its catalytic ability to convert glucose into 5-hydroxymethylfurfural (HMF). It was shown that as the calcination temperature increased, the Si-O-Al bond of H-Beta zeolite was broken and its dealumination effect was enhanced. Dealumination led to the collapse of the framework of H-Beta zeolite and a reduction in the number of acid sites, which in turn reduced its catalytic performance and the efficiency of HMF formation from glucose. Furthermore, H-Beta zeolite exhibited an extraordinary catalytic ability for the production of HMF from carbohydrates. Using glucose and cellulose as substrates, superior HMF yields of 91% and 46%, respectively, were achieved under optimal reaction conditions. Further, calcination removes carbon deposits in the recovered H-Beta zeolite, but it affects the cycling stability of the catalyst. Meanwhile, the by-products formed during the synthesis of HMF from glucose catalyzed by H-Beta zeolite catalyst were also clearly detected. Full article

Hierarchical Beta zeolites with interconnected intracrystalline mesopores and high structural stability are highly attractive for catalytic applications involving bulky reactants. Here, by introducing a suitable amount of polydiallyldimethylammonium chloride into the initial synthesis system, micron-sized Beta zeolite crystals with abundant hierarchical porosity (Beta-H) were hydrothermally synthesized. The sample named Beta-H_1 exhibited very high catalytic activity and durability for the Friedel–Crafts acylation of anisole with acetic anhydride. A 92% conversion rate of acetic anhydride could be achieved after 1 h of reaction in a fixed bed reactor, and 71% conversion still remained after 10 h, much better than the rate for conventional Beta zeolite (which decreased rapidly from 85% to 37% within 10 h). The enhanced catalytic performance of Beta-H zeolites could be mainly attributed to the relatively lower strong acid density and the faster transport rate of the hierarchical zeolites. In addition, Beta-H showed high structural stability and could be easily regenerated via high-temperature calcination without obvious loss in catalytic activity, demonstrating its great potential for catalytic applications in the industrially important Friedel–Crafts acylation process. Full article

Two multifunctional catalytic systems comprising Sn-based/doped crystalline zeolite Beta were synthesized, and they were employed as heterogeneous catalysts in the selective conversion of glycerol to methyl lactate. The first catalytic system, named Au-Pd-Sn-deAl-7.2-Beta-DP, was created through the post-synthesis dealumination of the parent zeolite Beta (Si/Al = 10) using 7.2 M HNO₃. Subsequently, it was grafted with 27 mmol of SnCl₄, resulting in Sn-deAl-7.2-Beta. Following this, Au and Pd nanoparticles were supported on this catalyst using the deposition–precipitation (DP) method. The second catalytic system was a physical mixture of Au and Pd nanoparticles supported on functionalized carbon nanotubes (Au-Pd-F-CNTs) and Sn-containing zeolite Beta (Sn-deAl-7.2-Beta). Both catalytic systems were employed in glycerol partial oxidation to methyl lactate under the following conditions: 140 °C for 4.5 h under an air pressure of 30 bar. The Au-Pd-Sn-deAl-7.2-Beta-DP catalytic system demonstrated 34% conversion of glycerol with a 76% selectivity for methyl lactate. In contrast, the physical mixture of Au-Pd-F-CNTs and Sn-deAl-7.2-Beta exhibited higher activity, achieving 58% glycerol conversion and a nearly identical selectivity for methyl lactate (77%). The catalytic results and catalyst structure were further analyzed using various characterization techniques, such as X-ray diffraction (XRD), N₂ physisorption, scanning electron microscopy (SEM), X-ray fluorescence (XRF), transmission electron microscopy (TEM), UV-vis spectroscopy, and pyridine Fourier transform infrared (FTIR). These analyses emphasized the significance of adjusting the quantity of active sites, particle size, and active sites proximity under the chosen reaction conditions. Full article

Tetravalent Sn species, such as zeolite or oxide, possess Lewis acidic properties, and thus exhibit prominent catalytic performance in several reactions when they are incorporated into the silica framework. Unfortunately, the synthesis of Sn-based zeolite (Sn–Beta) usually suffers from several drawbacks, including a long crystallization time, limited framework Sn content and complex synthesis steps. Sn-based composite oxides are favored in the industry, due to their simple synthesis steps and easy control of their pore structure, morphology and Sn content. In this work, an aerosol-assisted method is used to prepare Sn–Si composite oxide microspheres, using CTAB as template. The method is based on the formation of aerosol from a solution of Sn, Si precursors and a template (CTAB). The introduction of CTAB causes the surface tension of the atomized droplets to decrease. During the fast drying of the droplets, the Sn–Si composite oxide microspheres with a concave hollow morphology were first formed. After calcination, calibrated mesopores of 2.3 nm were also formed, with a specific surface area of 1260 m²/g and a mesopores ratio of 0.84. Sn species are incorporated in the silica network, mainly in the form of single sites. The resulting material proved to exhibit high catalytic performances in the Baeyer–Villiger oxidation of 2-adamantanone by using H₂O₂ as green oxidant, which was mainly attributed to the enhancement of the access to the catalytic tin sites through both the continuous hollow and mesopore channels, which have a 52% conversion of 2-adamantanone after 3 h of reaction. This method is simple, convenient, cheap and can be continuously produced, meaning it has broad potential for industrial application. Full article

Due to the increasing depletion of petroleum resources, the production route of non-oil-based aviation kerosene has been paid more and more attention. In this regard, the process of preparing aviation kerosene from syngas (CO and H₂) is one of the most promising industrial alternative fuel production routes. The traditional syngas-to-aviation kerosene catalyst uses iron-based and cobalt-based catalysts, which is a complex process with a high cost. In this work, a hierarchical Co/Beta metal-zeolite bifunctional catalyst prepared via the melting method is reported, which can directly and highly selectively produce an aviation kerosene component from syngas (CO and H₂). Compared with the catalyst prepared via the impregnation method, the Co/Beta catalyst prepared via the melting method has smaller, more highly dispersed Co metal active species and more suitable acid properties, the conversion of CO can reach 34.6%, and the selectivity of the C₈-C₁₆ aviation kerosene component can reach 40.2%, which provides a new idea for the industrial production of aviation kerosene. Full article