Nanomaterials
·
2020
·Vol. 10
·期 11
·2170
·
IF 4.324
Jialing Chen,Gang Peng,Tingyu Liang,Wenbo Zhang,Wei Zheng,Haoran Zhao,Li Guo,Xiaoqin Wu
The NH3-SCR activities and hydrothermal stabilities of fivexCu/MCM-22 zeolites with different Cu loadings (x= 2–10 wt%) prepared by incipient wetness impregnation method were systematically investigated. The physicochemical properties ofxCu/MCM-22 zeolites were analyzed by XRD, nitrogen physisorption, ICP-AES, SEM, NH3-TPD, UV-vis, H2-TPR and XPS experiments. The Cu species existing inxCu/MCM-22 are mainly isolated Cu2+, CuOxand unreducible copper species. The concentrations of both isolated Cu2+and CuOxspecies inxCu/MCM-22 increase with Cu contents, but the increment of CuOxspecies is more distinct, especially in high Cu loadings (>4 wt%). NH3-SCR experimental results demonstrated that the activity ofxCu/MCM-22 is sensitive to Cu content at low Cu loadings (≤4 wt%). When the Cu loading exceeds 4 wt%, the NH3-SCR activity ofxCu/MCM-22 is irrelevant to Cu content due to the severe pore blockage effects caused by aggregated CuOxspecies. Among the fivexCu/MCM-22 zeolites, 4Cu/MCM-22 with moderate Cu content has the best NH3-SCR performance, which displays higher than 80% NOxconversions in a wide temperature window (160–430 °C). Furthermore, the hydrothermal aging experiments (xCu/MCM-22 was treated at 750 °C for 10 h under 10% water vapor atmosphere) illustrated that all thexCu/MCM-22 zeolites exhibit high hydrothermal stability in NH3-SCR reactions.Keywords:Cu/MCM-22;NH3-SCR;Cu loading;hydrothermal aging
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CATALYSIS TODAY
·
2014
·
IF 3.309
Yuxi Gao,Xiaodong Wu,Shuang Liu,Duan Weng,Hongwei Zhang,Rui Ran
MnO x –CeO 2 mixed oxides were synthesized using a sol–gel method and the barium-loaded catalyst was prepared by a wet impregnation. Both catalysts were hydrothermally aged at 800 °C for 10 h. The fresh and aged catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), high-resolution transmission electron microscopy (HRTEM), H 2 temperature-programmed reduction (H 2 -TPR), NO temperature-programmed oxidation (NO-TPO) and soot temperature-programmed oxidation (soot-TPO). Compared with MnO x –CeO 2 , the Ba-modified mixed oxides show a much higher hydrothermal stability. Barium exists in the form of orthorhombic carbonate and cubic nitrate on the fresh sample. BaMnO 3 nanoparticles are identified to form at the interface of CeO 2 crystallites upon the hydrothermal ageing. The formation of the perovskites prohibits the sintering of ceria significantly, and consequently maintains the redox property of the aged mixed oxides to a great degree. Additionally, the nanoscaled perovskites themselves also contribute to the catalytic activity of the aged oxides catalyst.
研究领域:
催化材料
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
POLYMER COMPOSITES
·
2024
·
IF 4.8
Fei Yan,Junming Wang,Gang Li,Shengtao Dai,Yuhui Ao,Liu Liu
A carbon fiber-tannic acid-silicon dioxide (CF-TA-SiO 2 ) reinforcement with a “diatom frustule-like” structure was built via biomimetic mineralization to boost the performance of carbon fiber/epoxy resin (CF/EP) composites. As a bio-based polyphenolic compound, TA was used to modulate the mineralization of SiO 2 , and the easy agglomeration of SiO 2 was effectively avoided. The interfacial adhesion of the CF/EP composites was considerably heightened by improving the roughness and wettability of CF as well as by increasing the interfacial interactions between CF and the EP. Compared with the pristine composites, the flexural strength, interlaminar shear strength and interfacial shear strength of the CF-TA-SiO 2 /EP composites increased by 41.2%, 56.6%, and 50.4%, respectively. Moreover, the introduction of Si-O-Si and C-O-Si bonds at the interface led to a remarkable improvement in the hydrothermal aging resistance. This research provides a novel interfacial design for advanced composites with excellent interfacial properties, which broadens the application of these composites in hygrothermal environments. Highlights A “diatom frustules-like” structure was successfully constructed on the CF surface. This biomimetic mineralization was simple and environmentally friendly. This method solved the problem of easy agglomeration of SiO 2 . The interfacial properties of composites were obviously improved. The hydrothermal aging resistance of composites was enhanced.
研究领域:
材料科学
·
仿生学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2019
·
IF 14.229
Tong Zhang,Hui Li,Zhi Yang,Fengren Cao,Liang Li,Haijun Chen,Hui Liu,Ka Xiong,Jie Wu,Zhanglian Hong,Weichao Wang
Nanofiber catalysts are potentially promising to be equipped in the lean-burned vehicle exhaust emission system considering its facile synthesis, low-cost, long durability in contrast to the traditionally complicated powder based catalyst. Here, via electrospinning method, we synthesized YMn 2 O 5 nanofibers (average diameter: ˜93 nm) including nanowire stacked with particles, and hollow tubes with or without inside nanowires. The morphologies remained even after hydrothermal aging at 800 ℃ for 10 h with 10% H 2 O stream. X-ray photoelectron spectrum revealed Mn 4+ /Mn 3+ ratio 0.589 on the surface of YMn 2 O 5 catalyst (YMO), indicating the existence of oxygen vacancies. The highest conversion of electrospun mullite fibers at 310 ℃ is ˜18% higher than powder-based YMO at 352 ℃ in the presence of 5% H 2 O at WHSV = 240,000 ml g −1 h −1 . The extracted activation energy from NO-to-NO 2 conversion curves of YMO nanofiber (61.68 kJ/mol) is slightly lower than that of powder-based mullite (91.45 kJ/mol), consistent with calculated 68.16 kJ/mol on the fiber YMO surface (121) with a rate-limiting step of the NO 2 desorption. The catalytic activity can be attributed to the unit occupy of the e g ( d z 2 and d x 2 -y 2 ) orbitals of Mn-dimer atoms around fermi level based on the combination of the theoretical calculations and DRIFTS spectra analysis. Importantly, after the hash hydrothermal-aging, the highest NO oxidation conversion of powder-based mullite is less than 50%, while the fiber maintains a conversion of 62%. Moreover, the fresh YMO fiber maintained superior oxidation stability for 12 h at its maximum conversion of 66%. This work provides the possibility for mullite oxide fibers to replace powder-based precious metal catalyst coating on monolith converter.
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
CHEMICAL ENGINEERING JOURNAL
·
2019
·
IF 8.355
Han Jiang,Bin Guan,Xuesong Peng,Reggie Zhan,He Lin,Zhen Huang
This study focuses on investigating the influence of ion-exchange method (ION-F and ION-A) and one-pot method (ONE-F and ONE-A) on catalytic properties and hydrothermal stability of Cu/SSZ-13. It was found that ONE-F catalyst showed better SCR activity, especially at low temperature range below 400 °C. After hydrothermal aging, ION-A exhibited higher low temperature efficiency than ONE-A. The effect of synthesis method on the physicochemical structure, acidity intensity, and Cu species migration or transformation of the fresh and aged Cu/SSZ-13 catalysts were comprehensively characterized by NH 3 -TPO, H 2 -TPR, NH 3 -TPD, ICP, XRF, BET, XRD, SEM, and TEM. ONE-F has more isolated Cu 2+ sites, higher ratio of active sites Cu 2+ -2Z/[Cu(OH)] + -Z, more Lewis acid sites, and smaller particle size than ION-F. However, hydrothermal aging had severe effect on Cu/SSZ-13 prepared by one-pot method, leading to particle aggregation and decrease of active copper sites. According to NH 3 -SCR kinetic studies, smaller particle size and more uniformly distributed active sites over ONE-F resulted in less effect of pore diffusion limitation. Furthermore, in situ DRIFTS results indicated that more monodentate nitrates adsorbed sites and Lewis acid sites existed in ONE-F. On the other hand, monodentate nitrates were identified to be the most active nitrate species, and Lewis acid sites were ascertained to be more active than Brønsted acid sites. Therefore, ONE-F showed more excellent SCR performance than ION-F. However, hydrothermal aging resulted in loss of majority of nitrate adsorbed sites and acid sites over catalyst prepared by one-pot method, leading to lower SCR performance. In conclusion, Cu/SSZ-13 prepared by ion-exchange method has higher hydrothermal stability, however, fresh Cu/SSZ-13 prepared by one-pot method has excellent catalytic properties.
研究领域:
催化材料
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2019
·
IF 2.846
Lei Chen,Ding Wang,Jiadao Wang,Duan Weng,Li Cao
The CeO 2 -TiO 2 (CeTi) and CeO 2 /WO 3 -TiO 2 (CeWTi) catalysts were prepared by sol-gel method. The as-prepared catalysts were hydrothermally treated at 760 °C for 48 h in air containing 10 vol% H 2 O to obtain the hydrothermal aged catalysts. The sulfur aged catalysts were treated at 400 °C with 100 ppm SO 2 , 10% water vapor, air balance for 48 h and catalysts. The powder X-ray diffraction (XRD) and Raman results indicate that the crystallization of hydrothermal aged catalysts is more serious than sulfur aged catalysts. In addition, tungsten species can stabilize the CeTi catalyst from grain growth. According to the results of in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), temperature-programmed desorption of ammonia (NH 3 -TPD), H 2 temperature-programmed reduction (H 2 -TPR) and ammonia oxidation , the aging process leads to loss of surface area, redox properties, surface acidities and surface ceria concentration, especially for the hydrothermal aging. The NH 3 -NO/NO 2 SCR performances of sulfur aged catalysts are better than that of hydrothermal aged catalysts. Compared with CeTi catalyst, the addition of tungsten inhibits the crystallization of catalyst. So that more acid sites and active sites are retained. This is also the reason why tungsten addition improves the NH 3 -NO/NO 2 SCR performance of CeTi catalyst.
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
Polymers
·
2025
·Vol. 17
·期 9
·1229
·
IF 4.9
Mengke Jing,Shujie Zhang,Sichang Zhang,Mingzhou Li,Fan Chen,Yuchen Ma,Bo Sun
This work focuses on the hydrothermal aging of two-dimensional layered Ti3C2Tx(MXene)/epoxy (EP) nanocomposites. MXene/EP composites were successfully prepared by homogeneously dispersing multilayer MXene (m-MXene) and few-layer MXene (f-MXene) into the curing agent, methyl nadic anhydride (MNA). Considering the application, the MXene loading was designed to be 0.1 wt.%. Characterization included the characteristics of MXene, the water absorption behavior of the resin and composite samples, the glass transition temperatures (Tg) in various states, and the tensile strength evolution during aging. The curing behavior of the MXene composites was also discussed to facilitate an understanding of the processability. The results showed that MNA can chemically bond with MXene to obtain a stable suspension. The addition of MXene increased the curing characteristic temperature of the system, but the change in the activation energy of the curing reaction was minimal. The addition of MXene decreased the crosslink density of the epoxy resin, leading to a decrease in theTgvalue of the initial samples. After hydrothermal aging, theTgof pure EP decreased by 46.9 °C, and re-drying the samples did not fully restore theTg. However, theTgof the MXene/EP system decreased by only 8.9 °C (m-MXene) and 9.5 °C (f-MXene), respectively, and theTgvalues of the samples were fully restored to their pre-aging levels via re-drying. Experiments with immersion at 25 °C and 100 °C showed that the difference in water absorption behavior between the MXene/EP and pure EP systems was minimal. Tensile tests showed that the addition of MXene increased the initial strength of the resin system by 14.7% (m-MXene) and 20.9% (f-MXene). After 400 h of hydrothermal aging, the tensile strength retention of the pure EP samples was 69.1%, while the strength retention of the MXene/EP samples was 85.3% (m-MXene) and 83.0% (f-MXene). The combined results demonstrate that the addition of MXene with a low loading of only 0.1% can effectively improve the hydrothermal resistance of epoxy resins.
研究领域:
材料科学
·
复合材料
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Rui Li,Xiangqiong Jiang,Jiecheng Lin,Zhiping Zhang,Qintong Huang,Guangying Fu,Yujun Zhu,Jiuxing Jiang
SSZ-16 zeolite with AFX topology was synthesized by hydrothermal method using 1,4-diazabicyclo[2.2.2]-octane-C4-diquat dibromide as organic structure directing agent. Cu x -SSZ-16 catalysts were prepared by exchanging SSZ-16 zeolite with Cu and applied for selective catalytic reduction (SCR) of NO x with ammonia. Among these catalysts, Cu 2.2 -SSZ-16 performs the best SCR denitration (deNO x ) performance that above 90% NO x conversion can be achieved at 175–600 °C. Especially, the influences of the hydrothermal aging at various temperatures (650, 750 and 850 °C) on active species and AFX framework of the Cu 2.2 -SSZ-16 catalyst are investigated in detail by various characterization methods including XRD, SEM , H 2 -TPR, NMR, UV–vis-DRS, EPR, NH 3 -TPD and in situ DRIFTS . Cu 2.2 -SSZ-16 still shows good NH 3 -SCR activity after hydrothermal aging at 650 and 750 °C due to more Cu 2+ -2Z species in the sample. Still, obvious deactivation can be observed after hydrothermal aging at 850 °C because of the collapse of AFX skeleton and the weak interaction between active Cu species and the skeleton. Nevertheless, Cu 2.2 -SSZ-16 is a competitive candidate for NH 3 -SCR deNO x reaction in practical applications.
研究领域:
催化化学
·
环境科学
✓ 已验证
DOI
高影响因子
JOURNAL OF CATALYSIS
·
2021
·
IF 7.92
Yue Ma,Songqi Cheng,Xiaodong Wu,Tongxi Ma,Liping Liu,Baofang Jin,Minghan Liu,Jianbo Liu,Rui Ran,Zhichun Si,Duan Weng
To improve the hydrothermal durability of Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, a thin Al 2 O 3 modification layer was coated on the external surface of Cu-SSZ-13 by a chemical liquid deposition (CLD) method. The high-temperature SCR activity of the Al-modified Cu-SSZ-13 can be maintained upon 750–800 °C hydrothermal aging, and over-oxidation of NH 3 is largely inhibited. Based on H 2 -TPR and EPR results, it is revealed that CuAl 2 O 4 -like species forms upon Al modification and converts further to CuAlO 2 -like species during aging, while the accumulation of CuO-like species is inhibited. The high affinity of Al-containing species ( i.e. , Al 2 O 3 and CuAl 2 O 4 -like species) with Cu(OH) 2 is suggested by DFT calculations, indicating that Cu(OH) 2 detached from ion-exchange sites are captured by Al to form CuAlO 2 -like species instead of CuO-like species. The passivation of detached Cu species by coated Al leads to somewhat weakened low-temperature SCR activity, but successfully preserves the high-temperature SCR performance upon aging, which can be applied to high-temperature SCR scenarios.
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Environmental Chemical Engineering
·
2024
·
IF 7.4
Yang Yu,Ye Liu,Liting Hao,Bingxing Zhu,Xi Yang,Shifu Ge
Microplastics, while widely recognized as an environmental hazard, are particularly prevalent in sludge from wastewater treatment plants. This study addresses the gap in knowledge regarding the impact of hydrothermal treatment on the fate and behavior of microplastics in such settings. We explored the adsorptive interactions of polylactic acid (PLA-MPs) with volatile organic compounds (VOCs) post-hydrothermal aging and assessed the implications on cytotoxicity. Upon hydrothermal treatment, PLA-MPs exhibited a porous, honeycomb-like structure and a significant reduction in crystallinity, suggesting altered physical properties. Hydrothermal aging was shown to increase the hydrophilicity of PLA-MPs, which, coupled with structural changes, facilitated enhanced adsorption of VOCs, notably at elevated temperatures. We hypothesize that the observed increase in VOC adsorption is partly due to the exposure of more amorphous regions, thereby providing additional adsorption sites. The rise in hydrophilicity may also suggest a higher affinity for polar VOCs, potentially via hydrogen bonding with functional groups on the microplastic surface. Our results demonstrated that PLA-MPs aged at 140 °C had a toluene adsorption capacity of 62.17 ± 0.85 mg/g, a significant increase compared to unaged PLA-MPs, which adsorbed 22.25 ± 1.35 mg/g. In cytotoxicity assays, these aged microplastics significantly diminished cell viability at high doses, underscoring the enhanced potential for cytotoxic effects post-aging. Our research underlines the necessity for a deeper understanding of the interactions between aged microplastics and VOCs, paving the way for future studies to mitigate the environmental impact of microplastics from sludge sources.
研究领域:
环境科学
·
毒理学
✓ 已验证
产品关联
DOI
高影响因子
CATALYSIS TODAY
·
2018
·
IF 4.667
Xianghui Li,Yingnan Zhao,Huawang Zhao,Mengke Liu,Yuhan Ma,Xin Yong,Hong Chen,Yongdan Li
Two kinds of Cu-SAPO-34 catalysts, prepared with a one-pot technique using Cu- tetraethylenepentamine as co-template and an ion-exchange method, were hydrothermally treated at 750 °C for at least 16 h. The migration of Cu species during hydrothermal treatment and the corresponding effect on the selective catalytic reduction (SCR) of NO x were examined and characterized. A certain amount of CuO exists outside and inner the crystallites in the as prepared ion-exchanged sample, whereas copper is mainly atomically dispersed in the one-pot sample existing as isolated Cu 2+ . After hydrothermal treatment for 16 h, the amount of the inner nanosized CuO in the ion-exchanged sample reduced and the copper disperses to form more isolated Cu 2+ . However, surface CuO particles increase at the sacrifice of isolated Cu 2+ with extending the hydrothermal treatment to 24 h. Aggregation of Cu 2+ species also happens during the aging treatment over the one-pot prepared sample where the initial Cu is atomically dispersed as isolated Cu 2+ . The increase of the amount of the isolated Cu 2+ enhances the low-temperature (< 350 °C) performance. However, the increase of the amount of surface CuO particles in the aged samples promotes the nonselective NH 3 oxidation reaction in the high temperature range and results in the lowering of the SCR activity by limiting NH 3 supply.
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Physical Chemistry C
·
2024
·
IF 3.3
Fumei Wang,Qi Cai,Xinhua He,Boxiong Shen,Leila Negahdar,Shuo Feng,Andrew M. Beale
Cu/SAPO-34 catalysts have been widely used for the reduction of NOx from diesel exhaust by ammonia-selective catalytic reduction (SCR). Sulfur poisoning remains a challenge for Cu/SAPO-34 catalysts in NH3–SCR, restricting its application. In this study, Cu/SAPO-34 samples containing a mixture of Cu species comprising isolated Cu2+ located in the 6MR, Cu(OH)+ in 8MR, CuO clusters/nanoparticles, and Cu+ species were prepared. The Cu speciation during SO2 and hydrothermal aging of Cu/SAPO-34 SCR catalysts was subsequently studied. While hydrothermal aging had little effect on catalytic activity, the sulfur-aged sample exhibited deterioration in NH3–SCR activity over the temperature range of 100–575 °C. The breakage and collapse of the zeotype framework and chemical deactivation of the Cu/SAPO-34 catalyst after exposure to SO2 and H2O took place. A combination of X-ray photoelectron spectroscopy (XPS) and TGA-DT-DSC revealed the presence of ammonium bisulfate, copper bisulfate/sulfate, aluminum sulfate, and sulfuric acid after SO2 and H2O copoisoning under SCR conditions. Furthermore, Cu(OH)+ tended to migrate to form isolated Cu2+ and Cu+, as well as agglomerate to form CuO particles. Density functional theory (DFT) calculations revealed that SO2 and O2 could readily be absorbed by CuO particles to form stable copper bisulfate/sulfate species with the following order of preference: CuO > Cu+ > Cu2+ > Cu(OH)+. In contrast, Cu(OH)+ was less prone to be poisoned by easily releasing SO3 than other Cu species sites.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）