CARBOHYDRATE POLYMERS
·
2022
·
IF 10.723
Shaohuang Chen,Ning Yue,Mei Cui,Anastasia Penkova,Renliang Huang,Wei Qi,Zhimin He,Rongxin Su
TEMPO-oxidized cellulose nanofibrils (CNFs) possess lots of attractive properties. However, recycling of TEMPO is desirable because of ecological and economic demands. In this study, a novel strategy integrating direct reuse and extraction recovery of TEMPO was developed. 50 % of filtrates after TEMPO oxidation were directly reused and half of the fresh TEMPO was added to maintain a constant dosage, the obtained CNFs within 2 cycles shared similar carboxylate contents, crystallinity , and homogeneous width compared to the original ones. Furthermore, TEMPO in another 50 % of filtrates was extracted by ethyl acetate followed by distillation. The CNFs produced using the extracted TEMPO had almost the same properties compared to those of original ones, suggesting a negligible loss of activity of the recovered catalyst. Compared to the traditional route, the combined strategy exhibited a 31.3 % reduction in production costs, which enables clean and cost-effective production of CNFs and shows a promising industrial feasibility.
研究领域:
材料科学
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环境科学
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产品关联
DOI
PubMed
高影响因子
CARBOHYDRATE POLYMERS
·
2018
·
IF 5.158
Shaojie Liu,Huazhe Liang,Tingting Sun,Desheng Yang,Meng Cao
Polyamidoamine (PAMAM) dendrimers of G1.0 and 2.0 were synthesized by the repeated Michael addition and ester aminolysis of ethylenediamine and methyl acrylate. Through the reductive amination reaction of primary amines in PAMAM and carbonyl groups in 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl (4-oxo-TEMPO), the water-soluble PAMAM immobilized TEMPO (PAMAM-TEMPO) was successfully prepared. The obtained PAMAM-TEMPO was characterized by Fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectrophotometer (UV–vis). PAMAM-TEMPO was used as catalyst instead of free TEMPO for selective catalytic oxidation of primary hydroxyl groups in cellulose with water as reaction medium. The results showed that the catalytic performance of G1.0 PAMAM-TEMPO with 28.8% TEMPO loading was equivalent to free TEMPO. After salting out the supernatant of oxidation mixture, PAMAM-TEMPO was recovered by extraction with N ,N- dimethylformamide and reused for further oxidation cycles. No significant reduction in catalytic performance was found after 4 oxidation cycles. The recovery of PAMAM-TEMPO after each cycle was about 90%. By sonication of oxidized cellulose obtained with G1.0 PAMAM-TEMPO as catalyst, the individualized cellulose nanofibers with approximately 10 nm in diameter were successfully prepared. This is the first report on the use of immobilized TEMPO catalysts comparable to the performance of free TEMPO to oxidize cellulose in water.
研究领域:
化学工程
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材料科学
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绿色化学
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产品关联
DOI
PubMed
高影响因子
CATALYSIS LETTERS
·
2018
·Vol. 148
·期 9
·2709-2718
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IF 2.911
Liu Zhenzhen,Shen Zhongquan,Zhang Ning,Zhong Wei,Liu Xiaoming
Abstract Homogeneous Cu(I)/NMI/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) has been investigated for its catalysis on the aerobic oxidation of 1-octanol and other alcohols into aldehydes under room temperature. The catalytic species was found to be a Cu(I) centre coordinated by two NMI molecules and other two weakly bound solvent molecules, [Cu(NMI) 2 (Sol) 2 ] + (Sol = solvent). When CuI was used, this species could be [Cu(NMI)I(Sol) 2 ]. Not like being speculated previously, NMI in this system acts solely as a ligand and its role coordinated to the copper centre enhanced the electron density on the metal centre which promoted the O 2 binding in the catalysis. The labile solvent binding to the Cu(I) centre is essential to ensure both oxygen and substrate binding. The catalyst system is suitable for the oxidation of various alcohols using a simple reaction setup and workup. In particular, the system possesses strong oxidizing capability in quantitative conversion of benzylic alcohols regardless of the substituents on the phenyl ring and allylic alcohols into aldehydes. A plausible mechanism was also proposed for the catalysis. Graphical Abstract The aerobic oxidation of primary alcohols at room temperature to corresponding aldehydes was achieved by the catalyst composed by Cu(I) and methyl imidazole (NMI) mediated by TEMPO in acetonitrile. The catalytic species is proposed to be such a Cu(I) complex that two of its four coordinating sites are occupied by a strong ligand(s) and the rest two are weakly bound by solvent molecules.
研究领域:
催化化学
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有机合成
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DOI
高影响因子
COMPOSITES SCIENCE AND TECHNOLOGY
·
2019
·
IF 6.309
Jinyuan Wang,Jian Wu,Yuqing Luo,Yong Zhang,Sharon Guo,Sanshui Pan
Peroxide curing can provide rubber products with good thermal aging resistance, low compression set and light color. But butyl rubber (IIR) and bromobutyl rubber (BIIR) will incur severe main chain degradation when using a peroxide as a curing agent . The presence of 2,2,6,6-tetramethylpiperidinyl- N -oxyl (TEMPO) and in situ formed zinc disorbate (ZDS) in dicumyl peroxide cured BIIR system can inhibit the degradation of BIIR without compromising the curing extent of BIIR vulcanizates. ZDS is grafted on BIIR, while TEMPO functions as a free radical scavenger and nitroxide mediator for the grafting reaction. The in situ formation and grafting reaction of ZDS in BIIR are characterized by FTIR, XRD and NMR spectroscopy. In the presence of TEMPO and ZDS, BIIR does not suffer degradation but exhibits a continuous increase in torque and crosslink density with time during the post-cure period. The presence of TEMPO could effectively improve the thermal stability and aging resistance of BIIR vulcanizates. The study provides an effective route to avoid the degradation and promote the crosslinking of BIIR that can easily incur β -scission when reacting with peroxides.
研究领域:
材料科学
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高分子化学
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产品关联
DOI
高影响因子
CARBOHYDRATE RESEARCH
·
2022
·
IF 2.975
Fangxia Wu,Na Yan,Yan Guo,Xiaoxiao Yu,Lin Yi,Yilan Ouyang,Xin Wang,Zhenqing Zhang
The TEMPO/NaBr/NaClO system was used to modify konjac glucomannan and prepare β-1,4-linked D-mannuronic/glucuronic acid oligosaccharides . The impact of oxidant amount on the degree of oxidation , molecular weight , terminal structure and the ratio of sugar units were systematically investigated. Mannoses were transformed to mannuronic acids quantitatively, while some glucose were transformed to glucuronic acids, some degraded. The unspecific oxidation causes strong degradation of konjac glucomannan sugar chains. Multiple terminal structures were observed in the oxidized KGM products. According to those observations, the oxidation pattern of konjac glucomannan with the TEMPO/NaBr/NaClO system was speculated. It is suggested that the axial hydroxyl group at position 2 in mannose might form a hydrogen bond with the oxygen on the sugar ring. It would against the unspecific oxidation. While, both specific and unspecific oxidations were observed at glucose units with an equatorial hydroxyl group at position 2, and the degradation occurs mostly on glucose during the oxidation.
研究领域:
生物化学
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食品科学
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产品关联
DOI
PubMed
高影响因子
CELLULOSE
·
2018
·Vol. 25
·期 10
·5687-5696
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IF 3.809
Liu Shaojie,Sun Tingting,Yang Desheng,Cao Meng,Liang Huazhe
Abstract Water-soluble polyacrylic acid was prepared by solution polymerization, and then partially acylated by SOCl 2 to give a random copolymer of poly(acrylic acid- co -acryloyl chloride) (P(AA- co -AC)). Through the reaction of acyl chloride groups in P(AA- co -AC) with hydroxyl groups in 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy (4-OH-TEMPO), the water-soluble TEMPO immobilized copolymer of poly(acrylic acid- co -2,2,6,6-tetramethylpiperidinyloxy-4-yl-acrylate) (P(AA- co -TA)) with different TEMPO loadings were prepared and characterized by Fourier transform infrared spectroscopy and conductometric titration. P(AA- co -TA) was used as a recoverable catalyst instead of free TEMPO for selective catalytic oxidation of cellulose in water. The carboxyl content of oxidized cellulose with P(AA- co -TA) as catalyst was up to 60% of the free TEMPO level. Furthermore, P(AA- co -TA) was easy to recycle by its pH-sensitivity and the activity did not decrease after 4 cycles. Graphical abstract
研究领域:
化学工程
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材料科学
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催化化学
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产品关联
DOI
高影响因子
CHINESE JOURNAL OF CATALYSIS
·
2023
·
IF 16.5
Hongfang Wang,Leitao Xu,Jingcheng Wu,Peng Zhou,Shasha Tao,Yuxuan Lu,Xianwen Wu,Shuangyin Wang,Yuqin Zou
5-Hydroxymethylfurfural (HMF) electrooxidation in neutral conditions is a promising strategy to suppress the formation of humins and corrosive effects on electrochemical devices. However, scarce studies have been reported in neutral media due to the deficiency in electrophilic oxygen (eg OH – ) required for the activation of HMF. Herein, 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO)/Co 3 O 4 was utilized to co-catalyze HMF in neutral media, successfully achieving 2,5-furandicarboxylic acid (FDCA) with yield > 99%. It was found that TEMPO could promote HMF dehydrogenation to 2,5-diformylfuran (DFF) and simultaneously activated water via hydrogen-bonding interactions. As a result, the formation of OH* in neutral electrolytes was favored, which was absorbed by electrogenerated active Co species to facilitate subsequent conversion of formyl-group-involved intermediates to FDCA. This work provides a current understanding of the catalytic mechanism for HMFOR in neutral media and guides the design of highly efficient electrocatalysts for biomass upgrading.
研究领域:
化学工程
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催化科学
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生物质转化
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产品关联
DOI
高影响因子
FIBERS AND POLYMERS
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2016
·Vol. 17
·期 9
·1330-1335
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IF 1.022
Zhang Dezhi,Liu Mengru,Liu Yingying,Li Hailong
There is a challenge to find an effective and eco-friendly method to achieve the modification of fibers. The effect of laccase-TEMPO system on the properties of the bleached eucalyptus kraft pulp was investigated in this work. The results were demonstrated by the decreases in curl values and kink index. In addition, carboxyl and aldehyde groups were introduced in this reaction system. Compared with initial pulp, the contents of aldehyde and carboxyl groups of the treated pulp were increased from 42.6 μmol/g, 8.4 μmol/g to 125.4 μmol/g, 26.3 μmol/g respectively. However, the treatment had a detrimental effect on the thermal stability of pulp fibers. Moreover, the crystallinity index was slightly increased (from 82.1 % to 83.8 %) after the TEMPO-mediated oxidation, but the native crystalline structure was nearly unchanged. Furthermore, after the oxidation treatment, the relatively smooth film surface became textured, the carbon and oxygen bonds were changed, which were investigated by scanning electron microscope and X-ray photoelectron spectroscopy.
研究领域:
生物化学
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材料科学
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产品关联
DOI
高影响因子
RSC Advances
·
2015
·Vol. 5
·期 78
·63655-63661
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IF 3.84
Hui Yu,Linying Cao,Feifei Li,Qingfeng Wu,Qiang Li,Shuai Wang,Yong Guo
A rhodamine-nitroxide probe (R-NO˙), combining rhodamine fluorophore with a 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) receptor unit was introduced to probe glutathionyl radicals (GS˙) with high sensitivity and selectivity. The R-NO˙ probe could effectively scavenge GS˙ radicals with fluorescence enhancement since the nitroxide group restored the fluorescence properties. In this work, horseradish peroxidase (HRP)-catalyzed and metal-catalyzed oxidation systems were selected as the model of simulating the generation of GS˙, and we found that the metal-catalyzed system had the same experimental results with the HRP-catalyzed system, which provided a new approach to demonstrate the strong oxidant ability of the hydroxyl radical (˙OH) to initiate toxic GS˙. Furthermore, we confirmed that the production of GS˙ abided by a radical-initiated peroxidation mechanism of GSH with the mass spectrometry (MS) analysis and fluorescence spectroscopy. By using combined high-performance liquid chromatography (HPLC) detection and MS analysis, we also demonstrated that the R-NO˙ was converted into fluorescent secondary amine derivative (R-NH). The application of the probe in biological system was explored to monitor GS˙ in HL-60 cells and secondary amine fluorescence was observed upon stimulation by hydrogen peroxide and phenol. Development of fluorescence was prevented via preincubation with the thiol-blocking reagent N-ethylmaleimide (NEM).
研究领域:
生物化学
·
医学研究
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产品关联
DOI
高影响因子
Artificial Cells Nanomedicine and Biotechnology
·
2014
·
IF 0
Xiulan Su,Song Guo,Xiaoxia Huang,Xiang Wang,Donglai Qi,Chengmin Yang
Oxidative reactions of hemoglobin (Hb) are still a serious problem for Hb-based blood substitute development. Although varieties of antioxidant strategies have been suggested, this in vitro study examined the ability of the ascorbate, N-Acetyl-L-Cysteine (NAC), 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine-1-oxygen free radicals (TEMPO) and their reductant system in preventing Hb oxidation. The content of ferric Hb is monitored in the process of vitamin C (Vc), NAC, TEMPO and their reductant system. The results suggest that ascorbate is effective in reducing ferryl Hb, and TEMPO with Vc/NAC could obviously shorten the reaction time, but it does not play the role of Met-Hb reductases. It demonstrates that TEMPO did little to recover Hb under oxidative stress.
研究领域:
生物化学
·
医学工程
✓ 已验证
产品关联
DOI
PubMed
RENEWABLE ENERGY
·
2019
·
IF 5.439
Jiao Sun,Xin-an Xie,Di Fan,Xin Wang,Weiting Liao
Cellulose liquefaction in supercritical ethanol with 2,2,6,6-Tetramethylpiperidinooxy (TEMPO) was carried out in a stainless autoclave. The influence of process parameters on bio-oil (BO) and platform chemicals, mainly including the dosage of TEMPO, reaction temperature and reaction time, were investigated. Characterization of liquefaction products was explored by fourier transform infrared (FTIR) and gas chromatography-mass spectrometry analysis (GC-MS). The maximum yield of BO (57.98%) was obtained from cellulose liquefaction at 320 °C, 4 g TEMPO and moderate time of 60 min. It showed that the conversion rate and yield of BO was significantly improved by 46.14% and 31.87% due to temperature and TEMPO respectively. The relative contents of dominant platform chemicals in bio-oil were as follows approximately: ketones > esters > alkanes > alcohols > acids. The total yields of ketones enhanced markedly (from 20.00 to 41.83%) with the increasing of TEMPO. The results showed that TEMPO catalyst under appropriate reaction conditions improved the selectivity of platform chemicals with carbonyl, which had an obvious contribution on the converting of ketones.
研究领域:
化学工程
·
可再生资源
·
能源科学
✓ 已验证
DOI
高影响因子
CARBOHYDRATE POLYMERS
·
2020
·
IF 7.182
He Xiao,Yiwei Shan,Wenyao Zhang,Liulian Huang,Lihui Chen,Yonghao Ni,Bruno Boury,Hui Wu
Ultrafine C-doped ZnO/carbon nanocomposites with different photocatalytic activities have been prepared using TEMPO-oxidized cellulose as a template but also as the source of carbon. The result is an enhancement of the photocatalytic activity ascribed to different phenomena: a high mesoporosity beneficial to mass transport, a thin carbon layer onto ZnO increasing the charge transfer and hydrophobicity of ZnO, a narrowing of ZnO band gap and an increase of the zinc (V Zn ) and oxygen (V o ) vacancies effectively suppressing of the charge recombination. These are evidenced by photocatalytic test of photodegradation of methyl orange (MO) achieved to assess and compared the different photocatalysts. The highest rate constant value of photodegradation of MO is 0.0254 min −1 , three times higher than that of ZnO prepared without templates (0.0087 min −1 ). The present results introduce a new vision of the use of template with multiple roles in the preparation of inorganic materials and specially photocatalysts.
研究领域:
材料科学
·
环境科学
✓ 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）