CERAMICS INTERNATIONAL
·
2024
·
IF 5.1
Hanqi Xu,Dexiang Li,Ruiwen Luo,Yujun Zhao,Hongjiu Su
The exceptional characteristics of mullite render it a significant candidate for application across several domains. However, finding ways to lower the synthesis temperature of mullite without compromising its purity has been an acknowledged challenge. In this work, we synthesized colloidal mullite precursors featuring a composite structure via ion exchange method and hydrolytic precipitation reaction of hydroxyl-aluminum chloride and effectively prepared high-content mullite materials at low temperatures. The crystalline phase transformations of the composite precursors with varying abundances of aluminum and silicon atoms during the calcination process were examined using X-ray diffraction and thermal analyzer techniques. The silicon-rich precursor was observed to form the mullite phase at 550 °C, with a mullitization rate of approximately 20.08 wt%. In addition, the molecular characterization of the calcined samples, utilizing nuclear magnetic resonance to analyze the near-neighborhood environment and X-ray photoelectron spectroscopy to elucidate surface structure, revealed that no substantial structural rearrangement occurs in the Si-rich samples as the calcination temperature increases. More aluminum and silicon atoms form a homogeneous structure and contribute to the mullite crystallization process. Based on the provided characterization analyses, it is plausible to deduce that the low-temperature crystallization of mullite is associated with the significant mixing of Al and Si species in the precursor at the atomic level. More specifically, the abundance of amorphous silica particles in the Si-rich samples facilitates the formation of massive mullite-like Si-O-Al bonds with aluminum, owing to its migratory and viscous deformation characteristics. Therefore, during the calcination process, the grains begin to grow exponentially through the grain boundary migration mechanism once the crystallization of the mullite phase is complete.
研究领域:
材料科学
·
无机化学
✓ 已验证
DOI
高影响因子
APPLIED CLAY SCIENCE
·
2018
·
IF 3.641
Shun Wang,Peixin Du,Peng Yuan,Xuemin Zhong,Yaqi Liu,Dong Liu,Liangliang Deng
This work investigated changes in the chemical composition, structure and porosity of hollow spherical allophane under alkaline conditions, which are significant not only for understanding its fate in natural environment but also for its functional applications. Hollow spherical allophane with a silicon/aluminium (Si/Al) molar ratio of 0.77 was hydrothermally synthesised followed by treatment with dilute sodium hydroxide (NaOH) solutions with different concentrations (indicated by pH values). The allophane and its alkali-treated products were then characterized using a combination of techniques, such as Fourier-transform infrared spectroscopy, nuclear magnetic resonance and nitrogen physisorption analysis. Allophane showed a weak structural stability in alkaline conditions. At pH ≤ 11.0, the framework of allophane particles was almost intact; its polymerised silicates showed only slight dissolution. At a higher pH (> 11.0), desilication and dealumination enhanced, resulting in the destruction of the imogolite local structure (ImoLS) along the edges of defect pores and the formation of amorphous materials . Most of the defect pores increased in size, becoming accessible to nitrogen and the textural parameters of the micropores reached their maximum values at a pH of 12.5. However, the damage to some secondary pores and the collapse of some hollow spherules reduced total pore volume ( V total ). At a pH of 13.0, most of the hollow spherules were observed to have collapsed, resulting in remarkable decrease in the textural parameters. However, some unbroken and/or mildly broken allophane particles might remain, deduced from the relatively high BET specific surface area (SSA) and V total and the considerable proportion of micropores for Allo 13.0 . These results reveal the dissolution behaviour of allophane in alkaline conditions and the mechanism underlying this behaviour, providing essential insights into the mineral's potential applications.
研究领域:
土壤科学
·
矿物学
✓ 已验证
产品关联
DOI
高影响因子
RSC Advances
·
2025
·Vol. 15
·期 11
·8696-8706
·
IF 4.6
Zijian Wang,Ming Ke,Zhaozheng Song
Mordenite is extensively utilized in the domains of adsorption and catalysis owing to its excellent selectivity, stability, and renewability. In this work, the effects of crystal seeds, the ratio of SiO2/Al2O3, crystallization temperature, silicon source, and structure directing agents on the morphologies of mordenite are investigated by utilizing hexamethyleneimine (HMI) as the OSDA. Results indicate that the transformation of rod-like and flake-like mordenites is mainly related to the increasing ratio of SiO2/Al2O3, and the formation of flake-like morphology is related to various conditions. On a macro level, the rod-like and flake-like zeolites are formed by transforming amorphous precursors into small crystals and growing them epitaxially. On a micro level, HMIH+ progressively displaces Na+ to balance the framework charge with the increasing ratio of SiO2/Al2O3. DFT calculation and nuclear magnetic resonance results confirm the specific guidance of HMI on the T2 and T4 sites of the rod-like and flake-like mordenites. The conclusion can serve as a reference for regulating the morphology and active sites of mordenite.
研究领域:
材料科学
·
催化与吸附领域
✓ 已验证
产品关联
DOI
PubMed
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2023
·
IF 8.6
Ye Li,Yong Wang,Honghao Bai,Shishuai Li,Xiaomin Li,Xiaoqing Wang,Libo Li,Jinping Li,Jiangfeng Yang
The economically efficient separation of ethane (C 2 H 6 )/ethylene (C 2 H 4 ) presents challenges in the petrochemical industry, and the use of traditional adsorbents zeolite provides a reliable guarantee for maintaining the economic viability of adsorption separation technology. In this study, we investigate the impact of different silica-alumina ratios (SiO 2 /Al 2 O 3 = 40, 500, and 1500) of high silica zeolites ZSM-11 on the C 2 H 6 /C 2 H 4 separation performance to develop efficient C 2 H 6 selective adsorbents. The results show that the C 2 H 6 adsorption capacity and C 2 H 6 /C 2 H 4 selectivity of ZSM-11 increase as the silica-alumina ratios increases. The pure silica zeolite (ZSM-11(1500)) exhibits the highest adsorption capacity for C 2 H 6 (59.19 cm 3 /g) and the highest selectivity for C 2 H 6 /C 2 H 4 (2.04), which were superior to ultra-high silica sample (ZSM-11(500)) (55.06 cm 3 /g and 1.62, respectively) and high silica sample (ZSM-11(40)) (47.28 cm 3 /g and 1.23, respectively), at 273 K and 1 bar. The mixed gas breakthrough experiments results show that pure silica sample has outstanding C 2 H 6 /C 2 H 4 separation ability. The PSA simulation calculated data demonstrating promising potential for industrial applications. Importantly, this separation performance remains unaffected even in the presence of H 2 O.
研究领域:
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Kai Gao,Xingyu Liu,Shaochun Hou,Guoguang Zhang,Zongyang Da,Shengfeng Ma,Chunlei Guo,Weihua Guan
The concentration of rare earth elements (lanthanum, cerium, and praseodymium) within rare earth polishing powder waste (REPPW) typically exceeds 50 %, with the majority of impurities comprised of silicon and aluminum-related compounds. Transforming REPPW into recycled rare earth polishing powders that adhere to polishing standards in an eco-friendly and economically viable way presents a significant challenge in the industry. Traditional acid or alkaline processes predominantly recover rare earth elements as oxides, which are underutilized due to their high costs. Considering the varying forms of impurities and rare earth compounds found in REPPW, this research introduces a novel physicochemical decontamination and continuous chemical transformation process aimed at producing regenerated rare earth polishing powders. Under optimal conditions, the physicochemical two-step decontamination process achieved a rare earth recovery rate surpassing 92 %, while silicon and aluminum removal rates reached 86.12 %. During the continuous chemical transformation of REPPW, the rare earth phases in an alkaline setting followed the sequence REOF (CeO 2 ) → RE(OH) 3 → RECO 3 OH→RECO 3 F→CeLa 2 O 3 F 3 (CeO 2 ), which not only facilitated phase reorganization but also enhanced the particle surface structure. Notably, these chemical transformations did not disrupt the rare earth distribution; instead, they indirectly boosted product purity and uniformly dispersed within the regenerated polishing powder particles, thereby improving polishing efficiency. Consequently, the adoption of this innovative regeneration process for polishing powders holds substantial importance for the sustainable utilization of rare earth resources.
研究领域:
材料科学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
·
2024
·
IF 12.2
Qian Zhao,Xin Li,Guangyuan Chen,Zeru Wang,Chuan Tan,Cheng Liu,Hao Zou,Jing Ma,Lin Zhu,Tao Duan
Effective capture of radioactive iodine from nuclear fuel reprocessing is of great importance for public safety as well as the secure utility of nuclear energy. In this work, a hydrophobic nanosheet silicalite-1 (NSL-1) zeolite with an adjustable size was developed for efficient iodine (I 2 ) and methyl iodide (CH 3 I) adsorption. The optimized all-silica zeolite NSL-1 exhibits an excellent I 2 uptake capacity of 553 mg/g within 45 min and a CH 3 I uptake capacity of 262 mg/g within 1 h. Benefiting from the reduced thickness and enhanced porosity, microporous NSL-1 possesses enhanced iodine adsorption capacity and fast adsorption kinetics , which is a considerable high value among inorganic materials . Unexpectedly, the remarkable characters of high hydrophobicity , acid-resistance and anti-oxidation endow it a higher iodine uptake capacity than traditional aluminosilicate zeolites. More importantly, the high uptake selectivity toward I 2 possessed by NSL-1 owing to its hydrophobic skeleton under simulated dynamic conditions. The low cost, facile and scalable synthesis of NSL-1 further highlights great prospects for applications in the nuclear industry. This work provides useful insights for designing efficient adsorbents for iodine capture .
研究领域:
材料科学
·
核能工程
·
环境科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2025
·
IF 11.3
Hailan Wang,Ruobin Dai,Zhiwei Wang
Deciphering the structure and composition of the scaling layer is crucial for understanding its formation mechanisms in the reverse osmosis (RO) process. However, conventional characterization techniques face challenges in providing high three-dimensional resolution and precise compositional analysis of mixed scales, which hinders in-depth elucidation of the underlying mechanisms. In this study, we combined the exceptional depth resolution of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the superior mixed-scale discrimination capability of thermogravimetry-infrared spectroscopy (TG-IR) to analyze Si/Al scaling, a common issue in industrial RO systems. Under acid conditions, ToF-SIMS measurements revealed Al species enrichment on the membrane surface, attributed to the strong affinity between Al3+ and the membrane. The preferential deposition of Al3+ further facilitated the heterogeneous nucleation of polymerized silica through the electrostatic shielding effect, leading to the rapid formation of a thin and dense scaling layer. In contrast, neutral and alkaline conditions produced a slower-developing, uniform, thicker, and loosely structured scaling layer through physical deposition of supersaturated Si/Al complex scales. TG-IR analysis revealed that neutral conditions favored coprecipitated adsorption-bound Si/Al species (6-coordinate Al) and Si/Al polymers (4-coordinate Al), whereas alkaline conditions primarily produced coprecipitated silica and Al(OH)4−. These findings advance the mechanistic understanding of Si/Al scaling and provide a foundation for targeted control strategies in silica-metal combined scaling in RO systems.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2021
·
IF 13.273
Pan Liu,Qin-Hao Zhang,Jian-Qing Zhang,Ji-Ming Hu,Fa-He Cao
A method to quickly prepare highly oriented silicalite-1 zeolite films on different substrates at lower temperature was provided in this work. Compared with the traditional hydrothermal synthesis, rubbing a layer of seed pastes on the pretreated substrate surface in advance and using (NH 4 ) 2 SiF 6 as silicon source for subsequent secondary growth process can effectively reduce the synthesis temperature and shorten the contact time between the substrate and the strong alkaline synthesis solution. The thickness of the zeolite films prepared under three optimal conditions is all around 1 μm and the best contact angle value of 142.5° was achieved for the film prepared at 373 K for 4 h, while this values of the film prepared at 363 K for 6 h and 353 K for 10 h were 97.8° and 41.7°, respectively. The results of SECM showed that the detected localized current value of the film prepared at 353 K for 10 h was similar to that on bare steel after immersion in 0.62 M NaCl solution for 24 h (around 0.4 nA). At the same time, the current value measured under the other two preparation conditions was much higher, suggesting that the corrosion resistance of the film prepared under 353 K was unsatisfactory. In addition, EIS results demonstrated that the corrosion resistance of the films prepared at 363 K for 6 h also decreased significantly after 72 h immersion, while the films prepared at 373 K for 4 h still maintained excellent corrosion resistance and no obvious corrosion products were detected even immersion time up to 720 h. This work provides a new strategy for the application of zeolite in the field of material protection.
研究领域:
材料科学
·
腐蚀与防护
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Yimin Zhang,Meiyu Liu,Chengming Huang,Hang Zhang,Jian Zheng,Yucai Qin,Ye Yang,Yi Mei,Yun Zu
Zn-based catalysts are promising for direct propane dehydrogenation (PDH) to propylene owing to their cheaper and environment-friendly features but are subjected to serious depletion of active Zn component under working conditions. Herein, we successfully open a “black box” for the origin of active Zn speciations confined within the silicalite-1 (S-1) zeolite by thermogravimetric-mass spectrometry analysis and in-situ Fourier transform infrared spectroscopy. Guided by this, single-site, multinuclear and nanometer hydroxylated ZnO x species are separately encapsulated into the channels of S-1 zeolite by the controllable transformation of intermediate Zn(OH) x with assistant of vicinal- and nest-silanols. Delightfully, synthetic m -ZnO x @S-1 catalyst enables enviable propylene formation rate (50.8 mmol∙g cat −1 ∙h −1 ) and propylene selectivity (>96 %) in the PDH reaction. Most importantly, initial activity revives as before and without Zn loss after 7 regeneration cycles. This exceptional PDH performance is benefited from low-coordination and extra-stable multinuclear ZnO x species that can greatly lower the dehydrogenation barrier, favoring the PDH pathway to further produce propylene and hydrogen. These findings elucidate the potential of Zn-based zeolite catalysts for the development of PDH reaction and afford value-filled opportunities in alternative PDH catalyst optimization.
研究领域:
催化化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
INORGANIC CHEMISTRY
·
2022
·
IF 5.436
Qian Zhao,Changzhong Liao,Guangyuan Chen,Ruixi Liu,Zeru Wang,Anhu Xu,Shiyin Ji,Kaimin Shih,Lin Zhu,Tao Duan
Effective capture of radioactive iodine is highly desirable for decontamination purposes in spent fuel reprocessing. Cu-based adsorbents with a low cost and high chemical affinity for I2 molecules act as a decent candidate for iodine elimination, but the low utilization and stability remain a significant challenge. Herein, a facile in situ confined synthesis strategy is developed to design and synthesize a copper-encapsulated flaky silicalite-1 (Cu@FSL-1) zeolite with a thickness of ≤300 nm. The maximum iodine uptake capacity of Cu@FSL-1 can reach 625 mg g–1 within 45 min, which is 2 times higher than that of a commercial silver-exchanged zeolite even after nitric acid and NOX treatment. The Cu nanoparticles (NPs) confined within the zeolite exert superior iodine adsorption and immobilization properties as well as high stability and fast adsorption kinetics endowed by the all-silica zeolite matrix. This study provides new insight into the design and controlled synthesis of zeolite-confined metal adsorbents for efficient iodine capture from gaseous radioactive streams.
研究领域:
材料科学
·
环境科学
·
核能工程
✓ 已验证
DOI
高影响因子
Molecular Catalysis
·
2017
·
IF 0
Shuang Chu,Li’na Yang,Xingcui Guo,Linlin Dong,Xiufang Chen,Yaru Li,Xindong Mu
The catalytic behavior of a series of MFI catalysts with different Si/Al ratio (25–300) in the direct aqueous-phase hydrolysis of α-cellulose was studied. The effects ultrasonic pretreatment time, ZnCl 2 content, zeolite pore structure and acid-basic properties on catalyst activity and products distribution were systematically investigated. The results indicated that HZSM-5 with lower Si/Al ratio was beneficial for production of glucose and LA from α-cellulose. Ultrasonic pretreatment could decrease the degree of crystallinity and polymerization of α-cellulose, enhance the accessibility of acid sites and ZnCl 2 to the loosened amorphous regions of α-cellulose in water, and improve the hydrolysis efficiency of α-cellulose. The desilicated ZSM-5 (HZSM-5-DS(0.2)) showed much higher catalytic activities as compared to commercial ZSM-5 and α-cellulose conversion reached 76.5% over HZSM-5-DS(0.2) at 200 °C. Catalytic conversion of α-cellulose consisted of at least three important parallel reactions under the present hydrothermal conditions and a plausible pathway was proposed. Effective control of these reactions would be helpful to further maximize the target product yield during the catalytic conversion of α-cellulose.
研究领域:
化学工程
·
生物质转化
✓ 已验证
DOI
MICROPOROUS AND MESOPOROUS MATERIALS
·
2017
·
IF 3.615
Chang Wang,Jiaqi Liu,Jiangfeng Yang,Jinping Li
Synthesis of ultra-high silica (SiO 2 /Al 2 O 3 > 1800) MFI type zeolite such as silicalite-1 is still considered to be luxury because of the long synthesis time (5–12 days). Here, this material with a highly uniform mesoporous (20 nm) structure was crystallized in a shorter time (20 h) using a crystal-seeds method when an appropriate amount of potassium fluoride was added. Characterization techniques including XRD , SEM, TEM and liquid nitrogen adsorption provided detailed information on the two kinds of porous structure silicalite-1. Due to the “smooth” adsorption surface of silicalite-1 containing few equilibrium ions, it is ideal for the separation of gas mixtures containing non-polar molecules with similar physical properties. Moreover, the CH 4 , N 2 , CO 2 and C 2 H 6 adsorption properties were also investigated. Microporous silicalite-1 has a high adsorption capacity for CH 4 , N 2 , CO 2 and C 2 H 6 and adsorption selectivity for CH 4 /N 2 , CO 2 /N 2 , CO 2 /CH 4 and C 2 H 6 /CH 4 . Although a lower adsorption capacity was observed for mesoporous silicalite-1, the pore size did not affect the outstanding adsorption selectivity, on the contrary, the selectivity of mesoporous silicalite-1 was improved.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）