Molecular Catalysis
·
2023
·
IF 4.6
Wujian Zhang,Weijian Ge,Yiping Jin,Mingming Dang,Panpan Zhang,Wenfeng Han,Ying Li,Zongjian Liu,Haodong Tang
Loaded noble metal redispersion is an important way to solve catalyst sintering. However, how to redisperse at low temperatures or carbon-based noble catalysts is a difficult problem. In this paper, we report this phenomenon occurring on PdCu alloy catalysts, where small-sized PdCu alloys can be realized from sintered large-sized PdCu alloys on carbon supports in a CO/O 2 atmosphere. The mechanism of redispersion is elucidated by XPS, TEM and DFT calculations. The main reason for the redispersion is the formation of the PdCuOx intermediate, which can easily migrate to the nearby catalyst surface and then be reduced to smaller PdCu alloy nanoparticles. This work provides a deeper understanding of the redispersion phenomenon and provides certain applications in industry.
研究领域:
催化
·
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
CHINESE JOURNAL OF CHEMICAL ENGINEERING
·
2020
·
IF 2.627
Yexun Shi,Chang Li,Liming Shen,Ningzhong Bao
The graphene oxide powder (GOP) obtained from the spray drying process often exhibits poor re-dispersibility which is considered due to the partial reduction of GO sheets. The reduction of drying temperature can effectively increase the re-dispersibility of GOP, but result in a decreased drying efficiency. Herein, we found that the re-dispersibility of GOP is strongly affected by its microstructure, which is determined by the feed concentration. With the increase of feed concentration, the GO nanosheet assembly varies from the disordered stacking to relatively oriented assembly, making the morphology of the GOP transform from ball-like (the most crumpled one) to flake-like (the least crumpled one), and the 0.8 mg·ml −1 is the threshold concentration for the morphology, structure, and re-dispersibility change. Once the feed concentration reaches 0.8 mg·ml −1 , the appearance of the nematic phase in droplet ensures the relatively oriented assembly of GO sheets to form the layered structure with a low crumpling degree, which greatly improves the polar parts surface tension of the solid GOP, making the GOP easier to form hydrogen bonding with water during the redispersion process, thus stabilizing dispersion. This work provides useful information for understanding the relationships between the morphology, microstructure, and final re-dispersibility of GOPs.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Processes
·
2021
·Vol. 9
·期 7
·1116
·
IF 2.847
Xingxing Ye,Yexun Shi,Liming Shen,Peng Su,Ningzhong Bao
The “Drying-redissolution” method is promising for the industrial production of high-concentration well-dispersed graphene oxide slurry (GOS). As the potential key step in this method, the spray drying process requires a statistical investigation which guides the large-scale preparation of graphene oxide powder (GOP). This work systematically studies the effects of operating parameters, including nozzle airflow rate (439–895 L·h−1), atomization pressure (0.5–0.7 MPa), and liquid feed rate (3.0–9.0 mL·min−1), by using the response surface methodology integrated Box–Behnken design (RSM–BBD), aiming to produce GOP with high yield and easy re-dispersion. The optimized spray drying condition is predicted to be 439 L·h−1, 0.59 MPa, and 9.0 mL·min−1, at which a powder yield of 70.45% can be achieved. The experimentally obtained GOP has an average particle size of 11.65 μm and the low crumpling degree of the particle morphology results in the good re-dispersibility (97.95%) and excellent adsorption performance (244.1 mg·g−1) of GOP. The GOS prepared by the spray-dried GOP possess low viscosity and high exfoliation efficiency with a single-layer fraction up to 90.8%, exhibiting good prospects for application. This work first applied the RSM–BBD model on the spray drying process of GO, and evidenced the possibility of producing high-quality GO slurry with the “drying-redissolution” method.Keywords:graphene oxide;spray drying;response surface methodology;drying and redissolution
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
CHINESE JOURNAL OF CATALYSIS
·
2016
·
IF 2.628
Xinping Duan,Yan Yin,Xuelin Tian,Jinhuo Ke,Zhaojun Wen,Jianwei Zheng,Menglin Hu,Linmin Ye,Youzhu Yuan
Disintegration or redispersion of supported sintered gold nanoparticles (Au NPs) in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl halides, temperature and size distributions were investigated to elucidate the redispersion of Au NPs during halide-induced decomposition. This study proved that the alkyl halide induced the redispersion of sintered Au NPs which depended on the R–X (X = I, Br, Cl) bond dissociation energy (BDE) and thus provided a simple descriptor for the regeneration of inactive supported Au catalysts. A correlation between the BDE of R–X and dispersion efficiency was established. The tendency for disintegration and redispersion followed the R–X BDE of the alkyl halide. Compared to alkyl chlorides and bromides, iodides were more efficient for redispersing sintered Au NPs. As a descriptor, the BDE of R–I played a crucial role in particle redispersion. These findings provided insights into the mechanism of organic halide-induced Au NP disintegration and the effect of the halide type on the redispersion of sintered catalysts.
研究领域:
化学
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
·
2018
·
IF 3.046
Fang-Hao Niu,Zhi-De Hu,Hua Yan,Jian-Jian Yang,Han-Song Zhang
This work reports an investigation into the redispersibility of magnetorheological suspensions (MR suspensions) by testing the rheological properties of suspension sediment. By using a new freeze-sampling method, slices of sediment were taken from the bottom of the container with little changes on shear history which makes it possible to employ rheological measurement. Size distribution of particles contained in sediment was studied by a laser scattering method. Oscillatory and steady shear was employed to studying the rheological viscoelastic and flow behavior. Also, thixotropy and recovery behavior was also studied. The results obtained proved that redispersibility is a multifactor-dependent property which can be reflected from rheological responses of MR suspensions’ sediment. Hydrodynamic force and particle interaction which have significant influence on those properties were analyzed in this study. In addition, indexes correspond to different rheological properties were put forward to make a comparison quantitatively between traditional MR suspensions.
研究领域:
材料科学
·
流变学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED SURFACE SCIENCE
·
2020
·
IF 6.182
He Chen,Chunhong Qi,Luyan Shen,Qiang Fu,Zhiqiang Wang,Zhiyuan Xiong,Youyi Sun,Yaqing Liu
The reduced graphene oxide (rGO) nanosheets were modified by using polymeric nanospheres to adjust the d-spacings between dry rGO nanosheets. The experimental and computational studies show that the incorporation of polymeric nanospheres can effectively increase the d-spacing between dry rGO nanosheets, and meanwhile provide good compatibility of rGO with organic solvents. Specifically, when the d-spacing between nanosheets is greater than 14.0 nm, the dried rGO nanosheets can be well redispersed and stabilized in various organic solvents. This study thus provides a new technology that can produce dry rGO nanosheets with good re-dispersibility and stability in various organic solvents on a large-scale in a more environmental friendly manner.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2024
·
IF 7.7
Chen Cai,Guanghui Wang,Dongfei Xu,Cuiqiang Yan
This study aims to explore the redispersibility of dehydrated nanocellulose with p -toluenesulfonic acid ( p -TsOH) fractionated lignin as an eco-friendly and cost-effective capping agent, to cope with the challenge of irreversible agglomeration and thus loss of nanoscale of nanocellulose upon dehydration. The intermixing of nanocellulose and p -TsOH fractionated lignin was achieved using an aqueous ethanol solution as the medium and films of lignin-blending cellulose nanofibers (L + CNF) with excellent redispersing properties were obtained after facile air-drying. With 0.02 % ammonia as the dispersing solution, the dehydrated L + CNF film was able to achieve nearly 100 % redispersion yield after 30 min of mechanical agitation. If necessary, lignin in redispersed L + CNF can be removed by simple ethanol washing and centrifugation. In addition, redispersed L + CNF can be hybridized with poly(vinyl alcohol) (PVA) in a simple process to prepare PVA nanocomposite films with excellent hydrophobic, thermally stable, antibacterial, and mechanical properties. This study provided a sustainable and cost-effective solution to the dehydration/redispersion challenges of nanocellulose.
研究领域:
材料科学
·
生物质工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Smart Materials and Structures
·
2018
·Vol. 27
·期 9
·095011
·
IF 2.963
Fang-Hao Niu,Zhi-De Hu,Hua Yan,Han-Song Zhang,Jian-Jian Yang
This work reports an investigation into the sedimentation stability and redispersibility of magnetorheological suspensions (MR suspensions). By applying a freeze sectioning method, slices of suspension layer were taken from a suspension column with minimum changes to shear history. The descent of the mudline was tracked, and the size distribution of particles contained in the suspension layer was studied using a laser scattering method. Oscillatory and steady shear was employed in studying the rheological flow behavior and viscoelasticity. Hydrodynamic force and particle interactions which have significant influence on those properties were analyzed in this study. In addition, indexes corresponding to sedimentation stability and redispersibility were put forward to make a quantitative comparison between three kinds of traditional MR suspension. The result shows that oleic acid could improve the sedimentation stability to a certain extent and hinder the formation of 'stiff cake', while nano-silica could significantly lower the sedimentation ratio but require considerable energy consumption to redisperse the suspension.
研究领域:
材料科学
·
胶体化学
✓ 已验证
产品关联
DOI
高影响因子
WOOD SCIENCE AND TECHNOLOGY
·
2022
·Vol. 56
·期 6
·1761-1781
·
IF 2.898
Xu Yang,Xu Yongjian,Chen Hao,Xiong Jianhua,Gao Minlan
Cellulose nanocrystals (CNCs) are difficult to redisperse after drying unless chemical modification or adding additives has been adopted. The production, transportation and application of CNCs in large-scale are restricted owing to the poor redispersion ability. To this end, CNCs with redispersion ability were successfully extracted by nickel chloride hydrate enhanced deep eutectic solvent (Ni-DES), which is composed of choline chloride and oxalic acid dihydrate, from microcrystalline cellulose. C 2 O 4 2− and Ni 2+ are integrated with each other owing to the incorporation of deionized water at the end of Ni-DES extraction. As a result, the particles of NiC 2 O 4 ·2H 2 O are found on the surface of obtained CNCs. The NiC 2 O 4 ·2H 2 O particles, which can be removed by acid-washing, are beneficial to the redispersion of dried CNCs because they can prevent the formation of hydrogen bond during CNCs drying, as demonstrated by the results of SEM, XRD and size distribution. In addition, the results of FTIR, XRD, SEM, and TEM reveal that the crystalline structure, chemical structure, and microstructure morphology of CNCs are scarcely varied during the drying and redispersion. Nevertheless, the slight flocculation of CNCs is unavoidable during the drying and redispersion, which is responsible for the insignificant depravation in the size and size distribution of redispersed CNCs. Fortunately, the satisfied redispersion ability of CNCs is obtained by Ni-DES extraction. It is obvious that using Ni-DES for the extraction of redispersible CNCs can provide a potential strategy for improving the economic and environmental viability of CNC industrial production and application.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
REVIEW OF SCIENTIFIC INSTRUMENTS
·
2023
·Vol. 94
·期 1
·
IF 1.6
Lv Jingcheng,Wang Shiwei,Li Yao,Wu Mingyu,He Junxiang,Zhao Tong,Wei Yintao
Magnetorheological fluid (MRF) is a widely used smart material that suffers from sedimentation. Since sedimentation is unavoidable, it is crucial to study and improve the redispersibility of MRFs. However, previous redispersibility testing methods have problems, such as complicated operation and low precision. Simultaneously, a simple and effective method is urgently needed for high-precision modeling of MRF sedimentation to test the rheological properties of settled MRFs at different depths. After systematically analyzing the redispersion problem, this paper proposes decoupling the energy required for redispersing settled MRFs into two parts, which are related to different factors. These two parts are the energy required to separate the agglomerated particles (related to the MRF formula) and that to redisperse the settled MRF uniformly vertically against gravity (related to the solid concentration and packing limit). The energy that separates the agglomerated particles is proportional to the shear stress of slowly shearing the corresponding agglomerated samples, i.e., the yield stress. Thus, this paper proposes a simple microdamage quasi-static indentation method to measure the yield stresses of settled MRFs at different depths to characterize the redispersibility of the corresponding MRFs. Herein, this method is applied to study the mechanisms of the influences of surfactants, thixotropic agents, and their networks on the redispersibility of MRFs. The results indicate that a well-dispersed plate-like thixotropic agent network can effectively improve redispersibility, while surfactants with poor compatibility degrade redispersibility. In summary, this redispersibility test method will greatly facilitate studies of MRFs, such as optimizing the formulas and establishing sedimentation models.
研究领域:
材料科学
·
流变学
·
机械工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Yun-Yun Zeng,Lu-Yang Qiao,Shan-Shan Zong,Rong Guo,Jian-Kai Cheng,Xin-Yi Cao,Zhang-Feng Zhou,Mao-Hong Fan,Yuan-Gen Yao
Sintering caused catalyst deactivation resulting from the agglomeration of active metal sites. CH 3 I/CO based approaches are attractive owing to their effectiveness and mildness in rejuvenating sintered catalysts. However, few investigations have been reported for their application in oxides-supported catalysts. Herein, a landscape of reversible structural transformation of Pd/γ-Al 2 O 3 catalyst is depicted. The scenario of Pd redispersion in γ-Al 2 O 3 is significantly different from previously reported activated carbon-supported metal catalysts. Time-controlled CH 3 I/CO treatment facilitates the rapid redispersion of aggregated Pd particles on γ-Al 2 O 3 surface. The redispersion of Pd promotes the reactivity of Pd/γ-Al 2 O 3 catalyst. For dimethyl carbonate synthesis, the space-time yield increases from 556.9 g DMC ·kg cat. −1 ·h −1 to 1008.9 g DMC ·kg cat. −1 ·h −1 . For CO purification, 100% conversion of H 2 impurities and the rise of 27.4% in selectivity are achieved. The intrinsic oxidation rate is elevated from 607.8 mmol H2 ·g Pd −1 ·h −1 to 1166.5 mmol H2 ·g Pd −1 ·h −1 . However, complete oxidation and atomic dispersion of Pd cannot be achieved through further treatments. Combined characterizations verify the particle reconstruction of Pd and the evolution of anchoring sites on γ-Al 2 O 3 via strong metal-iodine binding. It reveals a double-edged-sword character of CH 3 I for Pd redispersion, wherein the excessive treatment results in re-aggregated Pd particles and inferior reactivity.
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
LANGMUIR
·
2012
·
IF 4.186
Qi Zhang,Guoqiang Yu,Wen-Jun Wang,Haomiao Yuan,Bo-Geng Li,Shiping Zhu
This work reports the development of a reversibly coagulatable and redispersible polystyrene latex system that can be triggered by N2/CO2. The coagulatability and redispersibility of the latexes were achieved by employing 0.9–5.6 wt % (N-amidino)dodecyl acrylamide (DAm), a reactive switchable surfactant, in an emulsion polymerization of styrene under CO2 atmosphere. The resulted latex particles were readily coagulated by N2 bubbling at 60 °C and redispersed by CO2 bubbling and ultrasonication, which switched amidine moieties between neutral and ionic states. The coagulation/redispersion processes were repeatable. The prepared latexes showed good stabilities against electrolytes, especially with higher charges.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）