Journal of the Taiwan Institute of Chemical Engineers
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2014
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IF 2.637
Chuan-Jun Yue,Miao-Miao Gan,Li-Ping Gu,Ya-Feng Zhuang
Cu/ZSM-5 prepared by in situ impregnated reduction was used for the catalytic dehydration of glycerol under solvent-free conditions. The catalyst was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), ammonia temperature programmed desorption (NH 3 -TPD), and thermogravimetry-differential scanning calorimetry (TG-DSC) analyses. Results showed that the nano-copper in Cu/ZSM-5 was evenly distributed onto the surface of ZSM-5 pores. Under the optimum conditions of the catalytic dehydration of glycerol, conversion was 92.1 wt.%. The selectivities of acrolein and acetol were 80.4 wt.% and 11.5 wt.%, respectively. Moreover, the low temperature favored for acetol selectivity. The synergic catalysis of Cu and ZSM-5 through the enol intermediate was responsible for the selectivity in the catalytic dehydration of glycerol.
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CATALYSIS TODAY
·
2013
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IF 2.98
Tong Zhang,Xiongfu Zhang,Xinjuan Yan,Lu Lin,Haiou Liu,Jieshan Qiu,King Lun Yeung
A well-designed Pd/ZSM-5@ZIF-8 core–shell structure has been prepared by application of a combination of seed-induction synthesis strategy and self-assembly synthesis techniques. First, uniform ZSM-5 particles with micron size and high crystallinity were prepared from organic-template-free gel systems containing 200 nm ZSM-5 seeds and exchanged with Pd(NO 3 ) 2 aqueous solution. Then incompatibility between the Pd/ZSM-5 core material and ZIF-8 shell precursor was circumvented by surface modification using a layer by layer self-assembly of polyelectrolyte, followed by a subsequent two-step temperature synthesis process inducing the formation of continuous and well-intergrown ZIF-8 shell. Thickness of ZIF-8 shell can be simply tuned by monitoring the assembly cycles. Furthermore, hydrogenations of 1-hexene and cyclohexene were chosen as model reactions to evaluate the catalytic behavior of the Pd/ZSM-5@ZIF-8 core–shell architecture and tert-dodecylthiol was used as a poison to test its anti-poisoning ability. Results show that such core–shell architecture exhibits excellent poison resistance and selectivity control properties for the hydrogenation reactions and can be potentially used as a membrane reactor in the field of heterogeneous catalysis.
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ChemCatChem
·
2017
·Vol. 9
·期 19
·3646-3654
·
IF 4.803
Bin Zhang,Qifan Wu,Chao Zhang,Xinluona Su,Ruhui Shi,Weiwei Lin,Yan Li,Fengyu Zhao
Graphical Stability from the support : The excellent stability of a Ru/ZSM-5 catalyst for levulinic acid hydrogenation in water relies on the higher tetrahedral-coordinated Al content and preferable pore connectivity in well-crystallized ZSM-5 zeolite, which suppress Ru aggregation and leaching and the formation of carbonaceous residues in the acidic environment. A long-life topic in the field of heterogeneous catalysis has been to develop supported catalysts that are stable against the aggregation of active metal and carbon deposition. Herein, we report a highly stable Ru/ZSM-5 catalyst for the hydrogenation of levulinic acid in water, which can be recycled at least 10 times without apparent loss of activity (conv. >95 %, yield >85 %). The influences of types of Al species, structure of support, Ru sizes, Ru leaching, and carbon deposition, etc. on activity and stability were discussed in detail. It was confirmed that the tetrahedral-coordinated framework Al in ZSM-5 contributed to the favorable metal–support interaction, and thus suppressed the aggregation and leaching of ruthenium during recycling. Besides, the suitable pore volume and channel network connectivity successfully prevent from deposition of carbonaceous residues.
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FUEL
·
2024
·
IF 6.7
Mei Ren,Jun Li,Manhong Huang,Donghui Chen,Xuelian Chen,Qi An,Songmei Sun
The escalating environmental issues resulting from waste plastic necessitate innovative decomposition methods that optimize conversion rates and product selectivity. In this study, we demonstrate that linear low-density polyethylene (LLDPE) can be effectively hydrothermolyzed into C1 − C4 compounds with a selectivity of 100 % in the presence of trace water on H-ZSM-5 catalyst under a relatively low temperature of 220 °C. Water plays a dual role here as both a solvent and a reactant. It was found the density of Brønsted acid sites is crucial for LLDPE decomposition, serving as the primary active centers for cracking LLDPE chains. In-situ EPR studies indicate a synergistic mechanism of free radical and carbenium ion pathways in LLDPE depolymerization. Density Functional Theory (DFT) simulations show that the depolymerization starts with the cleavage of a C–C bond in polyethylene, instigated by a hydrogen radical from the Brønsted acid site, leading to various intermediate stages for the formation of tert -butanol, acetone and acetic acid from two potential pathways. The presence of water is crucial in these pathways, aiding bond breakages and the creation of oxygenated products in the Brønsted acid site. This study represents a substantial leap forward in sustainable methodologies for upcycling plastic waste.
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FOOD CHEMISTRY
·
2024
·
IF 8.5
Yuchi Zhang,Le Han,Bohan Li,Yan Xu
Exploring materials with the dual functionality of detecting and removing tetracycline (TC) residues is crucial because of the environmental and health risks posed by antibiotic overuse. This study introduces a dual-emissive luminescent probe, CDs@ZSM-5:Eu 3+ , created through a solvent-free method combined with subsequent Eu 3+ ion exchange. The nanocomposite's blue emission, originating from carbon dots (CDs), is quenched by TC via an internal filtering effect, while an antenna effect triggers a strong red fluorescence of a TC-Eu 3+ chelate. The ratiometric fluorescence changes in CDs@ZSM-5:Eu 3+ endow a self-calibrated sensing mechanism for TC, offering a low detection limit of 5.04 nM and a broad detection range of 0.01–50 μM. Demonstrated in real milk samples, the probe exhibits high selectivity and accuracy in detecting TC. The nanocomposite also displayed an impressive TC removal capacity of 238.1 mg g −1 in water, ascribing to the enrichment and electrostatic attraction effects of ZSM-5 toward TC molecules. This research offers a facile strategy for constructing multifunctional zeolite-based hybrids for simultaneous TC detection and removal from aqueous solutions.
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PubMed
高影响因子
Sustainable Energy & Fuels
·
2024
·Vol. 9
·期 1
·152-171
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IF 5
Haoyu Liu,Wenbo Luo,Ke Wang,Yanlin Wang,Hong Yuan
The bolaform surfactant C6H13-N+(CH3)2-C6H12-N+(CH3)2-C6H12-O-C6H4-C6H4-O-C6H12-N+(CH3)2-C6H12-N+(CH3)2-C6H13 (BCPH-6-6-6) was synthesized and used to guide the synthesis of hierarchical ZSM-5 nanosheets (HZN) for use as zeolite catalysts. The number of acidic sites and the Al distribution in the zeolite pores were varied by changing the amounts of sodium sulfate and Al in the initial gel. The X-ray diffraction, Fourier transform infrared spectroscopy, scanning electronic microscopy, NH3 temperature programmed desorption, 27Al magic angle spinning nuclear magnetic resonance spectroscopy and N2 adsorption/desorption were used to characterize these materials. These zeolites each had a well-developed hierarchical system and specific surface areas as high as 631 m2 g−1, indicating that the BCPH-6-6-6 formed lamellar micelles based on π–π stacking. Interconnected hierarchical pore structures were retained after the templating agent was removed. The HZN sample exhibited a 90° rotational intergrowth structure and retained a large number of lamellae. The same material had a high concentration of acidic sites and contained Al in a tetrahedral coordination framework. The catalytic cracking of oleic acid using this zeolite gave light olefin yields up to 52.2% at 500 °C, exceeding the performance of conventional ZSM-5 (38.9%), and the catalyst remained active for up to 60 h. At 450 °C, the BTX selectivity of 6.72% obtained with this material also exceeded that from the conventional ZSM-5. These results were attributed to the connected hierarchical pores of the HZN, which promoted diffusion and provided higher carbon resistance.
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FUEL
·
2025
·
IF 7.5
Ke Yan,Yimin Zhang,Xinyu Xu,Yucai Qin,Yi Mei,Yun Zu
Non-classical crystallization pathways have emerged as a pivotal strategy for the synthesis of zeolites with tailored structures, with the initial feed composition being one of the most critical factors influencing this process. As primary raw material for the formation of zeolite networks, the physicochemical properties of Si sources significantly affected structural and acid properties of zeolites via non-classical crystallization pathways. While, the present operating mechanism between each other was still confusing. In this work, the precipitated silica with tunable Si-hydroxyls was home-made using one-step synthesis of fluorosilicic acid and ammonia aqueous in a SK static reactor. Leveraging this tailored silica, a series of hierarchically layered L-ZSM-5 zeolites were successfully prepared by a non-classical crystallization pathway regulated by Si-hydroxyl engineering. The findings revealed a linear positive correlation between the percentage of layered structures and framework single Al distribution of L-ZSM-5 zeolites and the number of silanol nests present in the precipitated silica. Under comparable conditions, the as-prepared hierarchical L-ZSM-5(7/6) zeolite with more layered structures and framework Al located in the straight/sinusoidal channels exhibited excellent propylene selectivity (44.09 %) and reaction lifetime (25 h, WHSV = 6 h −1 ) in methanol-to-propylene reaction. This work elucidates a decisive relationship between Si-hydroxyls engineering and zeolite crystallization, offering novel insights into the synthesis of zeolites with specific structural features through non-classical crystallization pathways.
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Catalysts
·
2024
·Vol. 14
·期 7
·397
·
IF 3.8
Yuxuan Zhang,Ruibo Wei,Lin Yang,Jinming Ge,Feiyang Hu,Tingting Zhang,Fangyin Lu,Haiwang Wang,Jian Qi
The low-temperature oxidation of methane gas in coal mine exhaust gas is important for reducing the greenhouse effect and protecting the environment. Unfortunately, the carbon–hydrogen bonds in methane molecules are highly stable, requiring higher reaction temperatures to achieve effective catalytic oxidation. However, metal oxide-based catalysts face the problem of easy sintering and the deactivation of active components at high temperatures, which is an important challenge that catalysts need to overcome in practical applications. In this work, a series of Mn-Co3O4active components were grown in situ on ZSM-5 zeolite with mesoporous pore structures treated with an alkaline solution via a hydrothermal synthesis method. Due to the presence of polyethylene glycol as a structure-directing agent, manganese can be uniformly doped into the Co3O4lattice. The large specific surface area of ZSM-5 zeolite allows the active component Mn-Co3O4to be uniformly dispersed, effectively preventing the sintering and growth of active component particles during the catalytic reaction process. It is worth mentioning that the Mn-Co3O4/meso-ZSM-5-6.67 catalyst has a methane conversion rate of up to 90% at a space velocity of 36,000 mL·g−1·h−1and a reaction temperature of 363 °C. This is mainly due to the mesoporous ZSM-5 carrier with a high specific surface area, which is conducive to the adsorption and mass transfer of reaction molecules. The active component has an abundance of oxygen vacancies, which is conducive to the activation of reaction molecules and enhances its catalytic activity, which is even higher than that of noble metal-based catalysts. The new ideas for the preparation of metal oxide-based low-temperature methane oxidation catalysts proposed in this work are expected to provide new solutions for low-temperature methane oxidation reactions and promote technological progress in related fields.
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Molecular Catalysis
·
2025
·
IF 4.9
Shengxin An,Shuaibo Zhao,Jingting Jin,Tao He,Yuhao Wang,Na Kong,Jie Zhou,Wenzhi Li
Great expectations have been placed on bimetallic co-modified zeolite for the direct oxidation of methane to methanol. In this work, H-ZSM-5 zeolite was modified with bimetallic copper and zinc via ion-exchange method. Numerous experiments were conducted and the methanol yield of 44,302.70 μmol·g cat −1 ·h −1 was obtained over 1Cu/2Zn-ZSM-5 catalyst. A series of characterization analyses confirmed that the introduction of Zn increased the proportion of active Cu species bound to extra-framework oxygen by altering the electronic state of copper. The bis (μ-oxo) dicopper ligand was identified as the active site for methane oxidation. The possible reasonable reaction pathway was the free radical reaction. This work provides a valuable guidance for the preparation of co-modified zeolite catalysts for the direct oxidation of methane to methanol.
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ADVANCED POWDER TECHNOLOGY
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2024
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IF 4.2
Hu Wen,Yuxin Li,Haitao Yin,Wei Wang,Zhengchao Jin,Shunyu Han,Nanzhe Jiang
The conversion of natural clay to crystalline zeolites has been the subject of considerable interest from both academic and industrial circles. We present an effective strategy for converting kaolin to ZSM-5 zeolite, addressing the issue of reduced mesopore formation in conventional nano-ZSM-5 aggregates due to close-packing. This strategy utilizes kaolin as the sole source of silicon and aluminum, and by decoupling the nucleation and growth of ZSM-5 crystals, loosely stacked nano-H-ZSM-5 aggregates with high crystallinity crystals can be synthesized in a solid-like system by employing a tiny amount of TPAOH (TPAOH/SiO 2 = 0.064). The resulting nano-H-ZSM-5 aggregates exhibited high specific surface area (405.66 m 2 /g), high mesopore volume (0.64 cm 3 /g), and superior catalytic activity. This strategy offers a novel approach to the cost-effective synthesis of nano-H-ZSM-5 aggregates suitable for industrial applications.
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高影响因子
CHINESE JOURNAL OF CATALYSIS
·
2025
·
IF 17.7
Qisong Yi,Lu Lin,Huawei Geng,Shaohua Chen,Yuanchao Shao,Ping He,Zhifeng Liu,Haimei Xu,Tiehong Chen,Yuanshuai Liu,Valentin Valtchev
The hydrothermal stability of zeolites is essential for their potential applications in biomass conversion, especially in processes involving elevated temperatures alongside the use or generation of H 2 O. In this study, we employed F - ions as mineralizers to synthesize hydrothermally stable ZSM-5 zeolites under acidic conditions. The acidic synthesis system promotes zeolites with fewer silanol-terminated lattice defects (ZSM-5(A)) compared to the traditional basic conditions (ZSM-5(B)), endowing materials with substantially higher structural integrity and hydrophobicity. After 10 days of autoclave treatment at 200 °C in aqueous phase, H-ZSM-5(A) demonstrated nearly unchanged reaction rates in the dehydration of cyclohexanol, while H-ZSM-5(B) lost > 50% of the dehydration activity. Additionally, H-ZSM-5(A) delivered higher initial dehydration rates compared to H-ZSM-5(B). The different measured activation energies further revealed variations in reaction pathways during cyclohexanol dehydration, i.e., the monomer- or dimer-mediated routes depending on the concentration of alcohol molecule within zeolite pores, providing additional evidence for the strengthened hydrophobic nature of H-ZSM-5(A). Beyond this, the zeolite surface properties and the strength of cyclohexanol-zeolite interactions may impose additional transport/adsorption barriers attributed to multi-phase phenomena on the more polar H-ZSM-5(B) zeolite surfaces. More importantly, the hydrothermal treatment did not induce significant desilication and dealumination in H-ZSM-5(A), thereby preserving its active acid sites and ensuring exceptional hydrothermal stability. The present work fundamentally studies the synthesis of hydrothermally stable zeolites in an acidic medium using fluorides and expands the understanding of polar interactions in catalysis, characterized by the dehydration of cyclohexanol, for future application in biomass conversion.
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CANADIAN JOURNAL OF CHEMICAL ENGINEERING
·
2025
·
IF 1.9
Xudong Wang,Yanyang Wu,Tianyou Wang,Bin Wu,Kui Chen,Lijun Ji
M-cresol and p-cresol, typically produced as mixtures in industrial processes, are crucial chemical intermediates. However, their separation is challenging due to their similar structures and properties. ZSM-5 zeolite has shown potential as an adsorbent for separation, while the performance is yet to be improved. In this study, ZSM-5-F(x) was synthesized via hydrothermal method, incorporating F − ions during the synthesis process. The adsorption behaviour of m-cresol and p-cresol on ZSM-5-F(x) was investigated through static experiments, with ZSM-5-F(8) demonstrating the highest selectivity (9.01). Both ZSM-5-F(0) and ZSM-5-F(8) were characterized using XRD, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) techniques. In addition, the introduction of F − ions increased the material's electronegativity, as demonstrated by the change in zeta potential from 53.22 to −45.93 mV. Single-component adsorption of m-cresol or p-cresol on ZSM-5-F(0) and ZSM-5-F(8) respectively were investigated in detail. The adsorption of m-cresol on ZSM-5-F(8) showed a non-monotonic phenomenon with a significant decrease after 0.06 mol/L. The thermodynamic parameters including Δ G , Δ H , and Δ S were calculated accordingly. All the values |Δ G |, |Δ H |, and |Δ S | of both components on ZSM-5-F(8) were greater than those on ZSM-5-F(0), suggesting that the introduction of F − ions facilitated the adsorption. Competitive adsorption experiments on both ZSM-5-F(0) and ZSM-5-F(8) were conducted at 298.2 K. The results indicated that the selectivity α p/m on ZSM-5-F(8) increased with increasing initial concentration and laid between 13 and 14. After seven consecutive regeneration cycles, the selectivity (α p/m ) only decreased to 13. This study suggests that ZSM-5-F(8) could be a promising adsorbent for m-cresol and p-cresol in industrial applications.
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