APPLIED CATALYSIS A-GENERAL
·
2014
·
IF 3.674
Siyang Tang,Zhen Liu,Xiaowei Yan,Ning Li,Ruihua Cheng,Xuelian He,Boping Liu
An extensive experimental kinetic study of ethylene trimerization was carried out over the Chevron-Phillips homogeneous catalyst system [Cr(2-ethylhexanoate) 3 (Cr(2-EH) 3 )/2,5-dimethylpyrrole (DMP)/co-catalyst/halide] in terms of the effects from organic halide additives, type of co-catalysts, temperature, ethylene pressure, Cr concentration, and ligand/Cr molar ratio, etc. Ten kinds of organic halides and four kinds of organometallic co-catalysts were tested in this work. The 1,1,2,2-tetrachloroethane (TCE) and triethylaluminum (TEA) were found to be the best candidates for this catalyst system. The molar ratios of DMP/Cr, TCE/Cr and TEA/Cr showed a strong impact on the catalytic performance of ethylene trimerization. A detailed catalytic kinetic behavior and the kinetic simulation were also performed for the first time over this catalyst system. It could be extrapolated that the dependency of the trimerization reaction rate on ethylene concentration and catalyst concentration is second-order and first-order, respectively. The apparent activation energy of this reaction is 99.1 kJ/mol at the temperature range from 65 °C to 95 °C. And the apparent reaction rate equation is achieved as follows:. R = 5.23 × 10 18 exp − 99.1 R T C ca 1.12 C e 1.95 .
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SENSORS AND ACTUATORS B-CHEMICAL
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2014
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IF 3.84
Wangyao Zhang,Yang Yang,Fenfen Li,Guosheng Song,Yong Shao,Ruizhuo Ouyang,Lina Xu,Weiwei Li,Yuqing Miao
A simple one-step method was successfully developed to prepare stable nanosized Ni(OH) 2 @Cr(OH) 3 hybrid particles by just adding NaOH to a mix solution containing Ni(NO 3 ) 2 and Cr(NO 3 ) 3 at room temperature. In contrast, under the exact same conditions, flocculent Ni(OH) 2 or Cr(OH) 3 precipitate was obtained after the addition of equivalent NaOH in a solution containing same amount of Ni(NO 3 ) 2 or Cr(NO 3 ) 3 as in the mix solution. The interaction between Ni(II) and Cr(III) ions was believed to make major contribution to the formation of stable Ni(OH) 2 @Cr(OH) 3 nanohybrid without aggregation to large-size particles. The prepared Ni(OH) 2 @Cr(OH) 3 hybrid nanoparticles were well characterized by the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), X-ray diffraction (XRD), and electrochemical measurements with results showing uniform size, smooth surface, good monodispersibility, fast electron transfer rate as well as promising electrocatalytic properties toward glucose (Glu) and cysteine (Cys) oxidation. The presence of a small amount of Cr(OH) 3 in the composite not only improved the stability and monodispersibility of the Ni(OH) 2 @Cr(OH) 3 hybrid particles, decreased their size to nanoscale, but also exerted positive effect to the electrochemical properties of the obtained Ni(OH) 2 based nanomaterials like the electron transfer rate and the electrocatalytic activity. Satisfactory electrocatalytic performances of the Ni(OH) 2 @Cr(OH) 3 nanohybrid toward Glu and Cys oxidations were achieved, respectively, in certain concentration ranges with acceptable detection limits and correlation coefficients, suggesting the potential facilitation of electrocatalysis toward other small molecules by the newly prepared Ni(OH) 2 @Cr(OH) 3 nanohybrid.
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ChemCatChem
·
2017
·Vol. 9
·期 17
·3364-3373
·
IF 4.803
Qiaoqiao Sun,Ruihua Cheng,Zhen Liu,Xuelian He,Ning Zhao,Boping Liu
Graphical The fluorine effect : Fluorinated Phillips catalysts (Cr/F-SiO 2 ) exhibit an enhanced reactivity towards ethylene polymerization and copolymerization. DFT calculations show that the difference of the Gibbs free energy barriers between chain transfer and chain propagation increased after the introduction of the fluoride onto the silica surface, which is in accordance with the increased molecular weight of the polyethylene formed using the Cr/F-SiO 2 catalyst. In this work, a fluoride-modified Phillips catalyst was investigated by using combined experimental and computational methods. The addition of fluoride to the Phillips Cr/SiO 2 catalyst can increase the activity of the catalyst calcined at a low temperature and the molecular weight of the polyethylene product. DFT calculations were performed to show that the difference of the Gibbs free energy barriers between chain transfer and chain propagation increased after the introduction of the fluoride onto the silica surface, which is in accordance with the increased molecular weight of the polyethylene produced by the fluoride-modified Phillips Cr/F-SiO 2 catalyst. The computational results also reflect the increase of the activity of the ethylene/1-hexene copolymerization after the introduction of fluoride, although the modification has little effect on the regioselectivity of the produced ethylene/1-hexene copolymer. Moreover, copolymers produced by the fluoride-modified Phillips catalyst with more short-chain branches (SCBs) in the high-molecular-weight fraction and a significant enhancement of the environmental stress crack resistance can be explained from the results of the DFT calculations.
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JOURNAL OF APPLIED POLYMER SCIENCE
·
2017
·Vol. 134
·期 18
·
IF 1.86
Shizhen Zhao,Xun Song,Xiuming Bu,Chong Zhu,Gang Wang,Fang Liao,Siwei Yang,Miao Wang
Because of the great demand for fluorescent materials, fluorescent dyes, semiconductor quantum dots, and carbon-based quantum dots have been studied extensively. However, the poor photostability and potential biological toxicity need to be resolved. In this study, we demonstrated the synthesis of a new biomass quantum dot, the polydopamine dot (PDADs), via a simple hydrothermal method under an acidic environment. This new biomass quantum dot showed not only remarkable photoluminescence properties (quantum yield = 0.93) but also a high stability and low toxicity. Moreover, these PDADs could be used as a fluorescent probe for the rapid detection of Cr(VI) (response time = 0.01 s). The detection limit (1 × 10 −11 M ) is the lowest detection limit reported for Cr(VI) fluorescent probes. The mechanism efficient quenching progress could have been due to the fast redox progress between the PDADs and Cr(VI). Moreover, we also showed a practical application of PDADs for Cr(VI) detection in vitro . © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44784.
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MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
·
2024
·
IF 4.2
Z.H.A.O.-X.U.A.N. Jiang
In this investigation, UiO-66-NH 2 was effectively synthesized through a solvothermal approach, utilizing benzoic acid and hydrochloric acid (HCl) as modulating agents. This synthesis process intentionally introduced defects mediated by benzoic acid, and the degree of these defects was precisely adjusted by the concentration of HCl. Subsequently, the material underwent a covalent modification process through an amidation reaction, resulting in the attachment of tetrakis (4-carboxyphenyl) porphyrin (TCPP). The results demonstrated a significant improvement in the photocatalytic reduction of Cr(VI), showcasing a 125 % elevation in reduction efficiency as compared to the unmodified UiO-66-NH 2 material serving as the baseline. The performance enhancement is due to the synergistic effect of the defect structure and TCPP modification, which enhances the light absorption, promotes charge transfer and separation, reduces the recombination rate, and improves the adsorption capacity and light absorption efficiency of Cr(VI). This research introduces an innovative approach and a highly effective catalyst, offering a novel solution for modifying metal-organic frameworks (MOFs) and enhancing their photocatalytic performance in the reduction of Cr(VI).
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Surfaces and Interfaces
·
2024
·
IF 5.7
Jiaqi Ma,Linkun Fan,Xusheng Wang,Lan Li,Yiming Zhang,Guixia Zhao,Bo Chai,Junkuo Gao
Cr(VI) stands as a profoundly toxic chemical and photocatalysis technology has shown promising potential in photocatalytic reduction of Cr(VI) to Cr(III), where the reduced Cr(III) is less toxic and can be further precipitated in a wide pH range. Metal-organic frameworks (MOFs), as emerging class of porous coordination polymers, is expected to be ideal platform for photocatalysis. In this study, defect engineering on MOFs was applied to promote photoreduction of Cr(VI). The obtained oxygen vacancy-containing MIL-125-NH 2 samples showed modified electron structure, adjusted surface and porous properties, and enriched active sites. Among these oxygen vacancy-containing MIL-125-NH 2 samples, the 300-M (MIL-125-NH 2 heated at 300 °C for 2 h under N 2 atmosphere) displayed the most remarkable performance in terms of photocatalytic Cr(VI) reduction. The pronounced efficacy of 300-M is evident from the achieved removal rate of Cr (VI), reaching an impressive 98 % in just 20 mins (19.6 mg Cr(VI) g −1 cata min −1 ), in stark contrast to MIL-125-NH 2 , which exhibited a modest removal rate of 53 %. Remarkably, the k-value for 300-M is 5.1 times that of MIL-125-NH 2 , further underscoring the superior efficiency of 300-M. The photoreduction mechanism of 300-M was further substantiated through a battery of advanced characterization techniques including transient photocurrent, electrochemical impedance spectroscopy, fluorescence spectroscopy, the Mott-Schottky analysis, and electron spin resonance. Those results disclosed that oxygen vacancies and mesopores introduced via controlled heat treatment play a pivotal role in facilitating the photoreduction of Cr(VI) within the MIL-125-NH 2 structure. More advanced characterizations for the structures of photocatalysts and the photocatalytic mechanisms including charge transfer path need further studied. The systematic exploration of temperature-dependent effects on material properties opens avenues for future research in designing efficient and versatile MOF-based photocatalysts for environmental remediation applications.
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JOURNAL OF MEMBRANE SCIENCE
·
2025
·
IF 9
Yunqi Zhou,Ye Yuan,Xinlei Liu,Zhi Wang
Metal-organic framework (MOF) membranes with proper pore size distribution and functional groups are generally more suitable for separation. Most MOFs are characterized by a hierarchical pore structure, which possesses large cavities surrounded by small windows. Fabrication of MOF membranes only retaining microporous fragment structure is a workable method to narrow pore size distribution. In this study, well-grown NH 2 -MIL-101(Cr) fragment membranes were fabricated for CO 2 separation by adjusting acetic acid – ligand – metal ratio to balance the nucleation and growth. NH 2 -MIL-101(Cr) fragment has a similar chemical structure to NH 2 -MIL-101(Cr) as expected, but only small pores with size around 0.56 nm is retained. The NH 2 -MIL-101(Cr) fragment membranes exhibited CO 2 /N 2 selectivity of about 37 with CO 2 permeance up to 6104 GPU.
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ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
·
2018
·Vol. 25
·期 23
·22455-22463
·
IF 2.8
Wang Pingping,Dong Faqin,Liu Mingxue,He Huichao,Huo Tingting,Zhou Lei,Zhang Wei
Photoelectrochemical process is an environmentally friendly technology and has a wide application in the control of environmental pollutants. Efficient nanophotocatalysts responsive to visible light are still highly attractive. In this work, α-Fe 2 O 3 /TiO 2 were grown on fluorine doped tin oxide (FTO) substrates by hydrothermal method for photoelectrochemical reduction of Cr(VI). Compared with the separate α-Fe 2 O 3 and TiO 2 electrodes, the composite α-Fe 2 O 3 /TiO 2 electrodes show higher photocurrent density. Under visible light irradiation, 100% removal efficiency of Cr(VI) was obtained after 40 min treatment. The composite α-Fe 2 O 3 /TiO 2 electrodes showed an enhanced absorbance in visible light region and had good stability to photoelectrochemical reduction of Cr(VI). The role of hole scavengers (citric acid and oxalic acid) and pH values was systematically investigated. This novel intensification approach provides new insight on the application of photoelectrochemical reduction in environmental remediation.
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Journal of Environmental Sciences
·
2025
·
IF 6.3
Yuanyuan Wang,Shijun Jia,Shiqiang Ding,Wenyan Zhang,Rui Shu,Yingfei Hu
Using natural minerals to eliminate harmful Cr(VI) under sustainable sunshine has significant potential. Herein, Palygorskite nanorods were utilized as carriers for the in-situ synthesis of CaIn 2 S 4 photocatalysts through a simple one-pot thermal process, enabling the efficient reduction of Cr(VI). With a Palygorskite to CaIn 2 S 4 mass ratio of 5 %, the conversion rate of Cr(VI) reached 98 % after 60 minutes of visible-light exposure, with a remarkable reaction rate of 0.0633 min −1 . The effective integration of CaIn 2 S 4 with Palygorskite led to a more uniform dispersion of CaIn 2 S 4 , exposing more reactive sites. Moreover, the establishment of a heterojunction between CaIn 2 S 4 and Palygorskite facilitated the transport of photogenerated electrons from CaIn 2 S 4 , enhancing the efficiency of charge separation. These factors contribute to the improved photocatalytic performance. Additionally, the developed composite photocatalysts demonstrated excellent stability under light exposure and could be reused efficiently. Trapping tests on active substances revealed that e − played key roles in the Cr(VI) reduction. This research suggests the potential of using natural minerals to fabricate composite photocatalysts capable of effectively removing pollutants from the environment using solar energy.
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SEPARATION AND PURIFICATION TECHNOLOGY
·
2024
·
IF 8.1
Shaoan Cheng,Yangxi Li,Zhen Yu,Yuqing Su
Adsorption can be used as a pollutant removal method to solve the increasingly serious problem of synthetic dye pollution and metal organic framework (MOF) is considered as a novel adsorbent for its unique structure. However, the high cost and high toxicity during the synthesis procedure of MOFs like MIL-101(Cr) limited their potential on the large-scale production and application. In this paper, waste PET plastic was depolymerized to prepare terephthalic acid (TPA) as an organic linker to synthesize MIL-101(Cr). Besides, Hydrofluoric acid (HF) was not added during the synthesis to avoid poisonous pollution. MIL-101(Cr) was applied to the adsorption of anionic dyes reactive red 2 (RR2) and reactive blue 19 (RB19). The batch experiments exhibited kinetic data best fitted the pseudo-first-order model (PFO) with the adsorption capacity of 662.87 (RR2) and 863.67 mg g -1 (RB19). The isotherm adsorption data fitted well with the Freundlich isotherm, indicating formation of multilayer coverage over the surface of MIL-101(Cr). The highest regeneration rate of MIL-101(Cr) at the fourth cycle was 91.18 and 91.44 % after RR2 and RB19 adsorption. X-ray photoelectron spectroscopy (XPS) technique and Fourier Transform Infrared (FTIR) spectroscopy both indicated the possible adsorption mechanism of MIL-101(Cr) toward RR2 and RB19 could be attributed to electrostatic interactions, hydrogen bonding, and the π-π stacking. This work proposed a novel method using waste plastics as raw materials to synthesize eco-friendly pollutant adsorbent, which had an enlightening effect on pollutant treatment.
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Surfaces and Interfaces
·
2025
·
IF 6.3
Jun Hua,Xianwen Wu,Fangxi Xie,Mingmei Wu
Manganese-based aqueous zinc-ion batteries are considered to be one of the most promising candidates owing to its abundant resources, environmental friendliness and high safety. However, some severe problems associated with cathode are mainly plagued by Mn (III) disproportionation and Jahn-Teller distortion, leading to undesired manganese dissolution and reduced their cycle life. Herein, Cr-doped δ-MnO 2 is synthesized by a simple hydrothermal method. This study demonstrates how Cr-doping addresses these challenges by narrowing the lattice spacing between MnO 2 layers, promoting self-confinement, and mitigating Mn 2+ dissolution. As a result, Cr-doped δ-MnO 2 exhibits enhanced crystal structure stability, with superior capacity retention of 65.80 % compared to 51.53 % for pristine δ-MnO 2 after 300 cycles at 500 mA/g. Our findings provide an alternative avenue for mitigating Mn dissolution, laying the groundwork for the adoption of Zn/MnO 2 batteries.
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Nanomaterials
·
2024
·Vol. 14
·期 10
·848
·
IF 4.4
Jun Wu,Gaofeng Shao,Xiaodong Wu,Sheng Cui,Xiaodong Shen
A novel Cr-doped BaTiO3aerogel was successfully synthesized using a co-gelation technique that involves two metallic alkoxides and a supercritical drying method. This freshly prepared aerogel has a high specific surface area of over 100 m2/g and exhibits improved responsiveness to the simulated sunlight spectrum. Methyl orange (MO) was chosen as the simulated pollutant, and the results reveal that the Cr-doped BaTiO3aerogel, when modified with the noble metal silver (Ag), achieves a pollutant removal rate approximately 3.2 times higher than that of the commercially available P25, reaching up to 92% within 60 min. The excellent photocatalytic performance of the Ag-modified Cr-doped BaTiO3aerogel can be primarily attributed to its extensive specific surface area and three-dimensional porous architecture. Furthermore, the incorporation of Ag nanoparticles effectively suppresses the recombination of photo-generated electrons and holes. Stability and reusability tests have confirmed the reliability of the Ag-modified Cr-doped BaTiO3aerogel. Therefore, this material emerges as a highly promising candidate for the treatment of textile wastewater.
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