CELLULOSE
·
2017
·Vol. 24
·期 6
·2415-2425
·
IF 3.417
Sang Xiankui,Qin Chengrong,Tong Zhangfa,Kong Song,Jia Zhuan,Wan Guangcong,Liu Xinliang
2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO) can selectively oxidize primary hydroxyl groups of cellulose to carboxyl groups. However, the depolymerization also occurs during the process. The kinetics and mechanism of carboxyl group formation on the surface of cellulose fiber oxidized by TEMPO/NaClO 2 /NaClO were discussed. The oxidization and depolymerization of cellulose occurred simultaneously, according to analysis of FTIR and 13 C CP/MAS NMR. The glucuronic acid and some small molecular fragments, formed by hydrolysis or β-elimination during the oxidation, are also discussed. The crystallization index increased and crystal size decreased, as shown by X-ray analysis. The degradation steps in the TEMPO/NaClO 2 /NaClO system was discussed, according to carbon conversion analyzed by 13 C CP/MAS NMR. The oxidation of cellulose can be described well by the kinetics model established based on the degradation of cellulose. It was found that temperature is one of the key parameters for controlling the oxdation and degradation level. The possible mechanism for oxidation of cellulose was composed.
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ACS Applied Materials & Interfaces
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2024
·
IF 8.3
Badusha Mohamad Ali,Ziqi Yu,Zhengyuan Tao,Tangxin Zhang,Lei Wang,Chenbing He,Hao Zhang,Jianli Wang
The novel 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) groups immobilized on functional polymers or nanoparticles emerged as potential Pickering interfacial catalysts (PICs) for effective catalysis in biphasic systems. In this study, a snowman-shaped Janus-structured polymer with TEMPO-anchored nanohybrid particles (SM-JPP-TEMPO) was prepared and employed as a potential PIC in the Anelli–Montanari system for the selective oxidation of alcohol. The amphiphilic character of SM-JPP-TEMPO particles plays a dual role as an emulsifier and catalyst in the Pickering emulsion. As a result, it enables smaller droplets (102 μm) at the water-in-oil (W/O) interface and reduces the interfacial tension from 26.58 to 17.38 mN/m, which improves the stability of the Pickering emulsion system. This constructed Pickering emulsion microreactor offers a larger interface contact area and shortens the mass transfer distance of the substrate of cinnamyl alcohol, which significantly enhances the catalytic conversion at the Anelli–Montanari oxidation system, thus achieving remarkable conversion efficiency of (92.3%) with excellent selectivity (99%) in static (stirring-free) condition. It was found that the Janus nanohybrid catalyst (SM-JPP-TEMPO) enhanced 1.29-fold catalytic efficiency compared to the TEMPO grafted spherical polystyrene nanoparticle (PS-NPs-TEMPO) catalyst (72%). Moreover, after seven consecutive cycles, the Janus nanocatalyst (SM-JPP-TEMPO) maintained the conversion significantly. Hence, these results collectively highlight that the amphiphilic SM-JPP-TEMPO catalyst provides an efficient and eco-friendly strategy for the intensification of liquid–liquid biphasic reaction systems for potential applications in industries.
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INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
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2024
·
IF 7.7
Yaowei Wu,Zuming Jiang,Yuhao Wang,Xiancai Jiang,Jian Hou,Bei Wei
Poly(acrylamide) (PAM) has excellent thickening ability as a conventional flooding agent. However, PAM confronts the problems of high injection pressure and high shear loss in the process of oil extraction, which have limited its application in this field. In this work, 2, 2, 6, 6-Tetramethylpiperidinooxy oxidized cellulose nanofibers (TOCNFs) enhanced sodium alginate (SA) shell was used to encapsulate PAM to form microcapsule. The composition, morphology, structure and the releasing behaviours of TOCNFs enhanced microcapsules was tested. Mechanical stirring was used to simulate the state of polymer subjected to shear during stratigraphic transport. The release performance of the microcapsules was characterized by measuring the change of viscosity with time. The ratio of the shell material with the best performance was explored, and the enhancement mechanism of the SA shell by TOCNFs was discussed. The experiments showed that the release time of PAM from the microcapsules was significantly prolonged with the addition of TOCNFs. The longest release time was observed when the ratio of SA and TOCNFs was 5: 1, with the release time of the microcapsules from the original 8 h to 16 h. The enhanced shear resistance of the microcapsules was attributed to the semi-interpenetrating network structure of SA and TOCNFs via Ca 2+ cross-linking as well as hydrogen bonding. The prepared microcapsules have promising applications in enhancing oil recovery.
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Food Packaging and Shelf Life
·
2021
·
IF 6.429
Yanyi Wen,Jia Liu,Lei Jiang,Zhongjie Zhu,Suirui He,Shu He,Wei Shao
An intelligent and active film was developed based on 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized bacterial cellulose (TOBC) containing thymol (THY) and anthocyanin-rich purple potato extract (ANT). The microstructure, thermal stability, water vapor permeability, mechanical property and UV protection performance of TOBC-based films were evaluated. Scanning Electron Microscopy (SEM) and Atomic Force Microscope (AFM) results show the additions of THY and ANT bring about the uneven distribution of TOBC fibers with slightly increased surface roughness . Meanwhile, the introduction of THY and ANT could increase the thermal stability, UV protection and water vapor barrier property of TOBC with slightly decreased tensile strength . The prepared ANT exhibits a pH-sensitive activity, and it endows the fabricated TOBC/THY/ANT film with colorimetric response ability to volatile ammonia. TOBC/THY/ANT film also exhibits good antibacterial and antioxidant activities . Particular finding is that TOBC/THY/ANT film possesses simultaneously freshness real-time monitoring and good shrimp preservation abilities. The antioxidant, antibacterial and color response performances of TOBC/THY/ANT film were measured for three cycles in order to prove its recycling ability. These unique features of TOBC/THY/ANT film demonstrate the potential in commercial shrimp packaging with freshness real-time monitoring.
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Journal of Environmental Chemical Engineering
·
2026
·
IF 7.2
Wenwen Qiu,Chengwei Lin,Wanjie Zhang,Chaolun Zheng,Jianquan Wang
Heavy metals pollution is a problem of concern, and their recycling from waste water is a challenging work. In this study, epichlorohydrin crosslinked TEMPO-oxidized cellulose nanofibers/polyethyleneimine (TOCNFs/PEI, CP) gel was used as a matrix to in-situ plant Zeolitic Imidazolate Framework-67 (ZIF-67), fabricating a nanocomposite gel (CPZ) with abundant active sites to adsorb Cu 2+ ions by mechanism of spontaneous adsorption on heterogeneous surfaces. Then two-step successive calcinations in N 2 and subsequent air were exerted for a Cu 2+ -loading gel (CPZ/Cu) and a virgin CPZ as a control, obtaining corresponding N-doped carbon composites containing metal oxides, i.e., CPZ/Cu-N 2 -Air and CPZ-N 2 -Air; and their application as supercapacitor electrodes was further investigated. The former demonstrates denser porous structure as well as lower surface area and pore volume than the latter owing to the generation of copper oxides, but better electrochemical properties are endowed, reasoned by the enhanced pseudo-capacitance from the synergism of Cu/Co oxides. The sample CPZ/Cu-N 2 -Air demonstrates a promising potential as an energy storage material. This study provides an effective recycling method of Cu 2+ ions from polluted water and develops an efficient solution for further utilization of the used polymer adsorbents containing heavy metals. This strategy achieves a closed-loop recycle from waste resources to advanced energy materials in a “trash to treasure” way, in line with the concept of environmental sustainability.
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INDUSTRIAL CROPS AND PRODUCTS
·
2023
·
IF 5.9
Zijun Zhang,Qimeng Jiang,Guihua Yang,Xv Zhang,Xingmao Jiang,Bo He,Jiachuan Chen
Film preservative packaging is one of common techniques to solve rot problem of fruits and vegetables in transit, storage and sale process. But traditional petroleum-based films have no long-lasting antibacterial properties and they are difficult to biodegrade. Herein, TEMPO-oxidized nanocellulose (TCNF) was used as green reducer and stabilizer to synthesize and immobilize silver nanoparticles (AgNPs) in one-pot method. Next the TCNF immobilized AgNPs was combined with chitosan to form antibacterial preservative composite film (CS/TCNF@AgNPs). The results show that CS/TCNF@AgNPs exhibited satisfied preservative effects for cherry tomatoes and strawberries . Notably, the composite film showed excellent antibacterial properties against E. coli and S. aureus and the accumulated release amount of AgNPs was only about 2.05% after 264 h. Furthermore, the composite film degraded almost completely in soil within 25 days. The cytotoxicity assay also exhibited favorable biocompatibility. Therefore, the composite film has potential application as a packaging material for fruit and vegetable antibacterial preservation.
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Molecular Catalysis
·
2022
·
IF 5.089
Pan Pan,Mingming Li,Yuxin Liu,Yisi Feng,Xinglong Li
2,5-diformylfuran (DFF) is a multifunctional intermediate, which can be used in drugs, functional polymers, fluorescent materials and surfactants. In this paper, a TEMPO-assisted magnetic Fe 3 O 4 @SiO 2 @mSiO 2 -NH 2 -Cu(II) catalytic system was developed for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran. The structure of Fe 3 O 4 @SiO 2 @mSiO 2 -NH 2 -Cu(II) was double-layer shell-core spherical structure with uniform ordered mesoporous on the surface, amino groups and Cu were evenly distributed in the outer mesoporous. The catalyst was characterized by FT-IR, TEM, EDS, SEM, XRD, BET and VSM. The effects of reaction conditions were investigated in detail. The conversion of HMF was 98.9% and the highest DFF yield was 92.4% under atmospheric oxygen in toluene solvent. The catalytic activity did not decrease significantly after 5 cycles. The catalytic system had good substrate adaptability for benzyl alcohols and aromatic alcohols with satisfactory yield of corresponding aldehydes (91.3–100%). A possible reaction mechanism was also proposed and found that bis(μ-hydroxy) double copper (II) may be the active reactant in oxidation reaction. The system provides a promising industrialized preparation method for DFF.
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INTERNATIONAL JOURNAL OF PHARMACEUTICS
·
2021
·
IF 5.875
Junjun Li,Rong Du,Qiong Bian,Danping Zhang,Siqian Gao,Anran Yuan,Xiaoying Ying,Youqing Shen,Jianqing Gao
During the occurring of cutaneous trauma, increasing oxidative stress response in wound site retards the progress of proliferation phase, impeding sequent efficient wound repair. At the same time, high-quality healing also requires adequate new blood vessels in order to furnish the wound site with a nutrient and oxygen-sufficient environment. Here we synthesized a novel hyaluronic acid (HA) material modified with a peroxidation inhibitor 2,2,6,6-tetramethylpiperidinyloxy (ATEMPO) for prevention of excessive reactive oxygen species (ROS) and promotion of angiogenesis after full-thickness skin excision in rats. Amines in ATEMPO attaching with carbonyls in HA chains was fabricated through N-acylation. The HA-g-TEMPO exerted a ROS-scavenging and angiogenesis-promoting function in vitro . In acute wound rat model, the wound closure efficacy was significantly improved to almost 55% at day 6 in comparison to 49% of HA, and wound sites in initial wound phase was also narrowed down sharply. Moreover, initially formed blood vessels were found in wound sites, further proved the angiogenesis-promoting function of HA-g-TEMPO. More interestingly, wound sites demonstrated an exciting regenerative healing effect which was characterized by marked skin appendages as well as reduced scarring. Therefore, this strategy showed a promising future that could be considered as a reliable and effective method to cutaneous wound healing.
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E-POLYMERS
·
2014
·Vol. 15
·期 1
·39-44
·
IF 0.33
Danjie Li,Xianbo Shen,Liang Chen,Huanchang Jiang,Jianli Wang
Covalently immobilizing the active sites or ligands on a polymer surface is an efficient strategy to achieve a full use of expensive organic parts. In this work, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was anchored onto polystyrene beads through an ether bond or an ionic liquid bridge. We quantitatively compared their thermal stabilities at nitrogen atmosphere and their chemical stabilities in a biphasic oxidation surrounding. It was found that the ionic liquid-bridged TEMPO exhibited an additional advantage of stability and could be reused for 30 consecutive recycles with a conversion ratio above 90% without any significant loss under the condition of the Montanari oxidation system (NaClO/NaBr, CH 2 Cl 2 /water), and the overall reaction time exceeded 2700 min.
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RSC Advances
·
2024
·Vol. 14
·期 28
·20199-20209
·
IF 3.9
Yaping She,Xinyu Chen,Mengya Wang,Anqiu Liu,Xiaochen Wang,Daming Gao,Kunhong Hu,Miao Hu
Heterogeneous solvent-metal-free aerobic oxidation of alcohols under ambient conditions is interesting but remains a significant challenge. Herein, a series of porous TEMPO-functionalized poly(ionic liquid)s (TEMPO-PILs) featuring a pure polycationic framework were successfully developed through the free radical polymerization of the ionic liquid 3-(2-chloroacetic acid-2,2,6,6-tetramethyl-1-oxo-4-piperidyl)-1-vinylimidazolium chloride and bis-vinylimidazolium bromide salt. Characterizations revealed that the obtained TEMPO-PILs possessed a high TEMPO density, abundant bromide ions, and a tunable porous structure, which enabled them to serve as solvent-free heterogeneous organocatalysts for the metal-free aerobic oxidation of benzyl alcohol under ambient conditions, exhibiting high catalytic activity and stable recyclability. A high yield of 99% coupled with a turnover frequency (TOF) of 13.3 h−1 was obtainable, which is higher than most of the reported TEMPO-based heterogeneous catalysts, even superior to homogeneous TEMPO-functionalized ionic liquids. Furthermore, a broad range of alcohols were effectively converted into their corresponding ketones and aldehydes. A possible reaction mechanism is proposed for understanding the catalytic oxidation behavior, indicative of the synergistic effect of TEMPO moieties and bromide ions.
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ACS Sustainable Chemistry & Engineering
·
2025
·
IF 7.3
Xiang Chen,Hao Li,Yichao Lu,Zhichun Liu,Zhongsen Ma,Yajie Zhang
2,5-Furandicarboxylic acid (FDCA) has been extensively verified as a biobased aromatic ring platform compound. The development of mild and efficient novel oxidation technologies is important for FDCA preparation technologies. In this study, the efficient oxidation of 5-hydroxymethylfurfural (HMF) to produce FDCA by the TEMPO/NaClO/KBr single-phase aqueous catalytic oxidation system was systematically investigated, and the mechanism was analyzed in detail. Under the optimal reaction conditions, TEMPO as the main catalyst directly catalyzed the oxidation of HMF to FDCA, and the HMF conversion and FDCA yield both reached 100%. The oxidant NaClO could achieve a quantitative reaction (NaClO/HMF = 3:1(mol)). In addition, the reaction was conducted at mild room temperature and innovatively utilized a single aqueous system as the reaction solvent. This establishes a new method for the oxidative preparation of FDCA with the potential for technical scale-up.
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POLYMER BULLETIN
·
2021
·Vol. 79
·期 11
·9397-9406
·
IF 2.87
Cai Yifeng,Wang Zuohua,Zhang Jian,Li Qingfang,Zhang Qiuhong
High molecular weight partial hydrolysis polyacrylamide (HPAM) is widely used in the oil recovery, and however, these high molecular weight HPAM will experience a rapid degradation when Fe 2+ was existed in the system. Some studies have implied it was a radical assisted decomposition process. However, no direct evidence had been provided in the reported works. Here, we investigated the effect of different metal ions, and the addition of (2,2,6,6-tetramethylpiperidinooxy) TEMPO to know the polymer degradations of the system. Further, by conducting electron paramagnetic resonance (EPR) on the Fe 2+ /HPAM system, we firstly provide a solid proof of the radical assist degradation process for the HPAM in the presence of Fe 2+ and oxygen. The mechanism has also been provided based on the observations. Graphical abstract The degradation mechanism is first revealed by EPR measurements for a Fe 2+ containing HPAM solution. A solid proof of the radical assists degradation process for the HPAM in the presence of Fe 2+ and oxygen.
研究领域:
聚合物科学
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环境化学
·
石油回收
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