PHOTOCHEMISTRY AND PHOTOBIOLOGY
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2022
·
IF 3.521
Ziwei Chen,Xueli Wang,Menghui Jia,Xiaoxiao He,Haifeng Pan,Jinquan Chen
5-Azacytosine (5-AC) is one of the best interesting noncanonical nucleobases due to its functionalization and structural imitation of natural bases. 5-AC can be used as the scaffold of two important chemotherapeutic medicines, 5-azacytidine and 2′-deoxy-5-azacytidine. Furthermore, increased sensitivity to UV leads to the photochemical effects of 5-AC also attracted attention. Yet, no study has been reported to explore the effect of glycosyl groups on the photophysical and photochemical properties of 5-AC, which can help to reveal the photostability of related actual clinic drugs. In this study, the excited-state dynamics of 5-azacytidine and 2′-deoxy-5-azacytidine are studied by femtosecond transient absorption and quantum-chemical calculations while revisiting that of 5-AC with a wider probe spectral range. It is shown that glycosyl substitution on the N1 position leads to ultrafast excited-state relaxation within several picoseconds in both nucleosides, which is distinct compared with the 17 ps lifetime seen in 5-AC. It is proposed that these changes are due to altering the energy level of the dark nπ* state. Moreover, our results suggest that it should be cautioned to simply replace sugar groups with methyl groups when doing a theoretical calculation study on nucleobases and their derivatives.
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高影响因子
Catalysis Science & Technology
·
2022
·Vol. 12
·期 24
·7281-7292
·
IF 6.177
Hui Chen,Wei Li,Mingchao Zhang,Wangyang Wang,Xian-Hua Zhang,Fa Lu,Kang Cheng,Qinghong Zhang,Ye Wang
Propane dehydroaromatization (PDA) to high value-added aromatic hydrocarbons, such as benzene, toluene, and xylene (BTX), is an attractive but challenging process. The traditional Zn/H-ZSM-5 or Ga/H-ZSM-5 catalysts can offer considerable PDA performances but still suffer from low activity and poor stability because of harsh reaction conditions. Here, we report a multifunctional Pt–Zn@H-ZSM-5 catalyst that exhibits a significantly improved performance in the PDA reaction at 550 °C, with a single-pass propane conversion of 74%, aromatics selectivity of 56%, and CH4 selectivity of only 4.7%. The yield of aromatics is twice as much as those of Zn/H-ZSM-5 and Ga/H-ZSM-5 catalysts. We have demonstrated that the Pt–Zn alloy nanoparticles with an average size of 2.4 nm are uniformly confined within H-ZSM-5 crystals, providing atomic-scale proximity between metal and zeolite acid sites. This unique structure enhances not only the dehydrogenation of the propane feedstock in the initial reaction stage but also the dehydrogenation of cyclic C6+ hydrocarbons by the recombinative desorption of surface hydrogen species in the last stage while suppressing the side hydrogenolysis and hydrogen-transfer reactions. Furthermore, the Si/Al ratio of H-ZSM-5, the synergistic effect between platinum and zinc, and the location of Pt–Zn nanoparticles over composite catalysts have also been discussed. These findings suggest that via bimetallic alloying and rational arrangements of functional sites at the nanoscale, the multistep PDA reaction can be greatly intensified.
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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
·
2022
·
IF 7.139
Huimin Li,Tiantong Zhang,Mao Peng,Qianqian Zhang,Jing Liu,Jinli Zhang,Yan Fu,Wei Li
Electrochemical reactions are important method for reducing the carbon footprint of large-scale chemical processes. Highly selective conversion of 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethylfuran (DHMF) is achieved under mild conditions through electrocatalytic hydrogenation (ECH) over AgCu nanoalloys supported by the pyrolyzed biomass alginic acid sodium (PA), with the advantage of utilizing the active hydrogen intermediates in the process. The Ag 1 Cu 1 /PA exhibits outstanding performance in ECH of HMF with a selectivity of 94% toward DHMF at a conversion of 93.2% and the Faraday efficiency (FE) of 61.8%, which are significantly superior to those over Ag/PA (selectivity of 53.89%, conversion of 90.6%, and FE 25.79%). The incorporation of Cu into Ag nanoparticles boosts the charge transferability and lowers the onset potential of ECH. Density functional theory calculations reveal that AgCu alloy provides more electron transfer to HMF and lowers the energy barrier for HMF hydrogenation.
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高影响因子
FUEL
·
2022
·
IF 8.035
Zhongqiang Tang,Siyuan Zhao,Xiao Zhao,Runze Jin,Jiaofei Wang,Zhuangzhuang Zhang,Haobin Hu,Xinwen Guo,Chengyi Dai,Xiaoxun Ma
The conversion of naphthalene into high value-added intermediate, 2,6-dimethylnaphthalene (2,6-DMN), using methanol as an alkylating agent has been widely studied. However, the low conversion of naphthalene and the easy deactivation of catalysts due to carbon deposition still pose challenges for industrialization. This is attributed mainly to the huge difference in the conversion kinetics of naphthalene and methanol. Herein, we report the first one-step process for the synthesis of 2,6-DMN from naphthalene by direct alkylation with syngas over “ZnAlCrOx&HZSM-5″ bifunctional catalyst. Compared to the traditional alkylation process of naphthalene with methanol, the direct alkylation of naphthalene with syngas not only shortened the process route and improved the reaction balance of syngas to methanol, but also improved the effective utilization rate of CO (29.87 %), naphthalene conversion, and catalyst stability. Results indicated that the alkylation of naphthalene could be improved by appropriately narrowing the spacing between the ZnAlCrOx oxide and HZSM-5. The acid strength and acidity on the external surface of HZSM-5 were modified by P or Si to improve the initial conversion of naphthalene and the selectivity for 2,6-DMN. The difficulty in determining the deactivation point of catalysts with multiple active sites under complex catalytic systems was solved by adopting a strategy of ”improve shortcomings“. The decline of metal activity in this reaction was found to be the main reason for catalyst deactivation. Doping of Ce into ZnAlCrOx helped to improve the stability of the catalyst from 80 h to 120 h.
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高影响因子
ENVIRONMENTAL POLLUTION
·
2022
·
IF 9.988
Xiao-Yan Cao,Yuan-Zhe Ni,Jing Li,Ling Li,Yi-Lin Zhao,Gui-Peng Yang
In this paper, the kinetics and thermodynamics of Adenosine 5′-monophosphate (AMP) sorption on the sediments obtained from the Yangtze River Estuary and adjacent areas were studied, in combination with the effects of the sediments' properties and media conditions. The kinetics curves could be described by a two-compartment first-order equation, and the equilibrium isotherms fitted well with the modified Langmuir and Freundlich models. The analysis of organic phosphorus (OP) fractions changes after sorption indicated that the contents of exchangeable or loosely sorbed P O increased most significantly. Higher organic matter (OM) of the sediments were favorable for the sorption ability. It was also found that the content of OP and OM in the sediments showed an obvious positive correlation, indicating that organic matter rather than Fe/Al oxides played an important role in the migration of OP in the Yangtze River estuary and its adjacent area. Temperature, salinity and pH of the media influenced the sorption of AMP significantly. Increase of temperature was of benefit to the sorption of AMP, which was a spontaneous and exothermic process according to the calculations of the thermodynamic parameters. The sorption capacity was higher at a moderate salinity in the range of our study. With the pH changing from 3 to 10, the sorption capacity exhibited as a “U-trend” curve.
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高影响因子
Journal of Environmental Chemical Engineering
·
2021
·
IF 5.909
Shahi Mulk,Muhammad Sajid,Lei Wang,Feng Liu,Gang Pan
5-Hydroxymethylfurfural (HMF) is one of the promising chemicals, which can serve as a platform chemical to produce various energy chemicals. HMF can be produced from different lignocellulosic biomass derived sugars employing different catalytic processes. In this study, the synthesis of HMF was investigated from excessively available sucrose using environment friendly and cost-effective technology . Among the various solvents applied, dimethyl sulfoxide (DMSO) was found as an efficient organic solvent medium. The results elucidated the combination of p -toluenesulfonic acid ( p TSA) and chromium chloride (CrCl 3 .6H 2 O) as the best dehydrating catalyst. A relatively higher HMF yield of 55% was achieved at a lower temperature (120 ℃) while at 150 ℃ (higher temperature) oxalic acid with higher concentration of CrCl 3 .6H 2 O gave a maximum yield of 59.21%. The time, temperature, and concentrations affected the yields. The positive impact was found with a rise in temperature from 100 to 120 ℃ in p TSA while oxalic acid affected the yield until 150 ℃. HMF yields were reported in descending order as p TSA > oxalic acid > maleic acid > malonic acid > succinic acid > blank at 120 ℃. It was observed that the isomerization of glucose to fructose is the major barrier to achieve the high process yield. Therefore, more efforts should be made to achieve the high rate of isomerization of glucose (part of sucrose disaccharide) in order to improve the HMF selectivity by depressing the humin formation.
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高影响因子
Crystals
·
2021
·Vol. 11
·期 10
·1247
·
IF 2.589
Changsheng Zhang,Kai Fan,Ge Ma,Chi Lei,Wei Xu,Jie Jiang,Bing Sun,Hongxing Zhang,Yunfeng Zhu,Song Wen
Hierarchical zeolites attract people’s attention due to their enhanced mass transfer properties in catalytic reactions. The research over obtaining these zeolites in green and efficient methods is of great significance for the current post-treatments and templating strategies tend to be costly for hierarchical zeolite synthesis. In this research, nanosized mesoporous ZSM-5 (SN-ZSM-5) zeolites have been synthesized without the addition of mesoscale templates under highly concentrated conditions. The physicochemical characteristics were systematically investigated by XRD, SEM, N2 sorption, TEM, and NMR. The SEM images showed ZSM-5 crystals with sizes between 50–110 nm were obtained. N2sorption and high-resolution TEM images gave direct evidence for the hierarchical structure of SN-ZSM-5. The forming mechanism for the hierarchical structure was proposed that the etching effect of the highly alkaline environment for the starting gels played a critical role in the formation of hierarchical structure. Catalytic tests in methanol-to-olefins (MTO) showed the SN-ZSM-5 performed a longer catalyst lifetime and higher propylene selectivity than the conventional ZSM-5 zeolites (C-ZSM-5) obtained from a traditional hydrothermal method. The features of hierarchical structure in the SN-ZSM-5 crystals and the sustainability for synthesis method could show a promising choice for wide applications of these SN-ZSM-5 zeolites in the future.Keywords:ZSM-5 zeolite;efficient synthesis;hierarchical;nano crystals
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高影响因子
Biomedical Materials
·
2021
·Vol. 16
·期 6
·065014
·
IF 3.715
Caini Yuan,Xinyun Long,Jinghua Li,Qing Cai
As a biocompatible and biodegradable polymer, poly(lactide-co-glycolide) (PLGA) has been widely used as a carrier to achieve controlled drug delivery in various forms. Focusing on skin tumor treatment, herein 5-fluorouracil (5-FU) was embedded into the core of coaxially electrospun PLGA fibers to get a drug-loaded core–shell fibrous membrane. In the coaxial electrospinning, poly(vinylpyrrolidone) was applied in the inner flow to facilitate the formation of the core–shell structured fibers. The morphology and micro-structure of the fibers were characterized by scanning electron microscope and transmission electron microscope. The influences of the molecular weights and chemical compositions of PLGA copolymers on the release behaviors were studied. The cytotoxicity of the fibers was characterized by cell proliferation and living-dead cell staining experiments. The results showed that faster release rates would be obtained if the copolymers were of lower molecular weights and higher fraction of glycidyl unit. All the prepared 5-FU loaded fibrous membranes were non-cytotoxic, suggesting their potential applications in skin tumor treatment.
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高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2021
·
IF 5.455
Yanliang Zhai,Yunshan Shang,Luoming Zhang,Xiaoling Meng,Yanjun Gong,Lirong Zheng,Jing Zhang,Ping Liu
Hydrothermally modified nanosheet ZSM-5 zeolite by directly using MnO x nanoparticles was carried out and this substantially offered a high performance catalyst for methanol to propylene (MTP) reaction. The properties of as synthesized ZSM-5 nanosheets with different MnO x amounts (NS-x) were compared with ZSM-5 nanosheets modified by impregnation method (IM-0.5) and physically mixed method (PM-0.5), respectively. The initial state of MnO x nanoparticles was close to Mn 2 O 3 with 20 nm in size. XRD , H 2 -TPR and XAFS results confirmed under high temperature hydrothermal condition, the Mn 2 O 3 nanoparticles disaggregated into Mn 2 O 3 clusters and entered the framework defects of nanosheet zeolite with high dispersion. Infrared spectra of hydroxyl groups (OH-IR) showed that the Mn 2 O 3 clusters were bonded with silanol defects both on the surface and inside zeolite, which substantially increased the stability of Mn 2 O 3 clusters and healed the framework defects. In contrast, the Mn species in the impregnated sample was close to the co-existence of Mn 2+ ions and MnO 2 nanoparticles with 2–3 nm, no interaction between Mn species and Si–OH group was determined. Notably, the typical sample (NS-0.5) with MnO x cluster modification performed much higher propylene selectivity and catalytic stability (~52%, 240 h, WHSV = 3 h −1 ), while the conventional IM-0.5 and PM-0.5 showed poor propylene selectivity (48%, 46%) and catalytic stability (166 h, 133 h) in MTP reaction. The excellent result should be attributed to the subtle control of external strong acid and the less structural defects, due to specific existence of bonded Mn 2 O 3 clusters.
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ChemSusChem
·
2021
·Vol. 14
·期 23
·5311-5319
·
IF 8.928
Jianwang Xu,Xinge Miao,Lei Liu,Yantao Wang,Weiran Yang
Graphical Transfer hydrogenation : 5-Methylfurfural (5-MF), a promising C 6 platform molecule, is directly produced from biomass-derived carbohydrates by iodide-mediated transfer hydrogenation. Under the optimized conditions, 30–50 % of 5-MF is yielded from low-cost sugars and starch with 5-MF productivity as high as 103 mmol g cat −1 h −1 . The catalytic system is simple, robust, recyclable, and preferable to other approaches for the production of 5-MF. Herein, a robust catalytic system was developed for the green synthesis of 5-methylfurfural (5-MF) by iodide-mediated transfer hydrogenation. Around 50 % of 5-MF was yielded from d -fructose within 7.5 min using NaI as the catalyst and formic acid as both the hydrogen source and co-catalyst. The catalytic system was used for six consecutive cycles without any decrease in the yield. Various starch and raw biomass could be used as promising starting materials for 5-MF synthesis with moderate yields, and the productivity of 5-MF from corn starch reached 103 mmol g cat −1 h −1 , which is comparable with the best result from l -rhamnose. Moreover, the co-production of 5-MF and furfural from raw biomass makes this methodology more competitive than other routes.
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高影响因子
CATALYSIS LETTERS
·
2021
·Vol. 152
·期 4
·954-961
·
IF 3.186
Shi Shengbin,Wu Yuanfeng,Liu Panli,Zhang Mengting,Zhang Zongqi,Gao Lijing,Xiao Guomin
Synthesis of 5-hydroxymethylfurfural (HMF) from carbohydrates was achieved over the homogeneous catalyst acid poly(4-styrenesulfonic acid) (PSS). The various reaction conditions like reaction temperature, reaction time, various solvent, solvent volume, and catalyst dosages were explored. The results showed that the PSS catalyst resulted in 86.8% HMF yield from fructose and 48.5% HMF yield from glucose in solvent 1-methyl-2-pyrrolidone and dimethyl sulfoxide, respectively. The catalyst has reused five cycles without obviously reduced on HMF yield, suggesting that PSS showed high catalytic activity at recycle experiment. Thus, PSS was a potential candidate for homogeneous catalyst acids and can convert carbohydrate compound into HMF conveniently. Graphical Abstract
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高影响因子
JOURNAL OF MEMBRANE SCIENCE
·
2021
·
IF 8.742
Shuang Wang,Liangqing Li,Jiajia Li,Jiaxuan Wang,Enze Pan,Jinming Lu,Yan Zhang,Jianhua Yang
High-performance zeolite socony mobil five (ZSM-5) membranes were successfully prepared on a cheap, tubular α-Al 2 O 3 support via a proposed wet gel conversion (WGC), aiming at avoiding the competitive zeolite crystals growth in the solution and ensuring the formation of polycrystalline zeolite layer onto the support surface. A small amount of gel was loaded on seeded tubes via dip-coating and then converted to ZSM-5 membranes via direct crystallization without using any additional synthesis solution for membrane growth. By using this method, the amount of synthetic gel was largely reduced as compared with the traditional hydrothermal synthesis . The effects of crystallization temperature, crystallization duration, and synthetic gel silica source dissolution duration on the morphologies, microstructures, and pervaporation performances of ZSM-5 membranes were investigated. Under optimized synthesis conditions, the as-synthesized ZSM-5 membrane showed high separation performance and stability in isopropanol dehydration. During the 104-h pervaporation test, the permeation flux was stable at 2.96 kg m −2 h −1 with a separation coefficient exceeding 10,000. The synthetic route exhibited excellent reproducibility for the fabrication of highly water-selective ZSM-5 membrane. This work provides a novel, feasible method for the preparation of zeolite membranes with high performance, high atom economy, low cost, and reduced waste solution.
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