期刊文献+
共找到6,413篇文章
< 1 2 250 >
每页显示 20 50 100
Transition-metal-catalyzed remote meta-C-H alkylation and alkynylation of aryl sulfonic acids enabled by an indolyl template
1
作者 Pengfei Zhang Qingxue Ma +2 位作者 Zhiwei Jiang Xiaohua Xu Zhong Jin 《Chinese Chemical Letters》 SCIE CAS CSCD 2024年第8期254-259,共6页
Transition-metal-catalyzed remote sp^(2)C-H functionalization of aryl sulfonic acids was hardly ever real-ized owing to competitive ortho-C-H functionalization of aryl sulfonates and electron-deficient nature of pheny... Transition-metal-catalyzed remote sp^(2)C-H functionalization of aryl sulfonic acids was hardly ever real-ized owing to competitive ortho-C-H functionalization of aryl sulfonates and electron-deficient nature of phenyl ring.Herein,with the assistance of a practical biaryl indolyl directing template,palladium-catalyzed remote sp^(2)C-H alkylation of aryl sulfonic acids have been achieved in moderate to good yields with exclusive meta selectivity.Moreover,remote meta-selective C-H alkynylation of aryl sulfonic acids was also accomplished with a rhodium catalyst.These meta-C-H functionalized products proved to be the superior synthetic precursors,which are difficult to access using the conventional strategy. 展开更多
关键词 c-h functionalization Aryl sulfonic acid SITE-SELECTIVITY Transition-metal catalysis alkylation ALKYNYLATION
原文传递
Small molecule deoxynyboquinone triggers alkylation and ubiquitination of Keap1 at Cys489 on Kelch domain for Nrf2 activation and inflammatory therapy 被引量:1
2
作者 Ke-Gang Linghu Tian Zhang +10 位作者 Guang-Tao Zhang Peng Lv Wen-Jun Zhang Guan-Ding Zhao Shi-Hang Xiong Qiu-Shuo Ma Ming-Ming Zhao Meiwan Chen Yuan-Jia Hu Chang-Sheng Zhang Hua Yu 《Journal of Pharmaceutical Analysis》 SCIE CAS CSCD 2024年第3期401-415,共15页
Activation of nuclear factor erythroid 2-related factor 2(Nrf2)by Kelch-like ECH-associated protein 1(Keap1)alkylation plays a central role in anti-inflammatory therapy.However,activators of Nrf2 through alkylation of... Activation of nuclear factor erythroid 2-related factor 2(Nrf2)by Kelch-like ECH-associated protein 1(Keap1)alkylation plays a central role in anti-inflammatory therapy.However,activators of Nrf2 through alkylation of Keap1-Kelch domain have not been identified.Deoxynyboquinone(DNQ)is a natural small molecule discovered from marine actinomycetes.The current study was designed to investigate the anti-inflammatory effects and molecular mechanisms of DNQ via alkylation of Keap1.DNQ exhibited significant anti-inflammatory properties both in vitro and in vivo.The pharmacophore responsible for the anti-inflammatory properties of DNQ was determined to be theα,β-unsaturated amides moieties by a chemical reaction between DNQ and N-acetylcysteine.DNQ exerted anti-inflammatory effects through activation of Nrf2/ARE pathway.Keap1 was demonstrated to be the direct target of DNQ and bound with DNQ through conjugate addition reaction involving alkylation.The specific alkylation site of DNQ on Keap1 for Nrf2 activation was elucidated with a synthesized probe in conjunction with liquid chromatography-tandem mass spectrometry.DNQ triggered the ubiquitination and subsequent degradation of Keap1 by alkylation of the cysteine residue 489(Cys489)on Keap1-Kelch domain,ultimately enabling the activation of Nrf2.Our findings revealed that DNQ exhibited potent anti-inflammatory capacity throughα,β-unsaturated amides moieties active group which specifically activated Nrf2 signal pathway via alkylation/ubiquitination of Keap1-Kelch domain,suggesting the potential values of targeting Cys489 on Keap1-Kelch domain by DNQ-like small molecules in inflammatory therapies. 展开更多
关键词 Deoxynyboquinone ANTI-INFLAMMATION Target Keap1/Nrf2 alkylation UBIQUITINATION
下载PDF
Synthesis of spherical nano-ZSM-5 zeolite with intergranular mesoporous for alkylation of ethylbenzene with ethanol to produce m-diethylbenzene
3
作者 Siyue Wang Jinhong Li +5 位作者 Qingxin Xu Shengjie Song Yu'ni Jiang Lidong Chen Xin Shi Weiguo Cheng 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第3期298-309,共12页
Catalytic synthesis of m-diethylbenzene(m-DEB)through alkylation of ethylbenzene(EB)may be a promising alternative route in comparison with traditional rectification of mixed DEB,for which the top priority is to devel... Catalytic synthesis of m-diethylbenzene(m-DEB)through alkylation of ethylbenzene(EB)may be a promising alternative route in comparison with traditional rectification of mixed DEB,for which the top priority is to develop efficient and stable heterogeneous catalysts.Here,the spherical nano-ZSM-5 zeolite with abundant intergranular mesoporous is synthesized by the seed-mediated growth method for alkylation of EB with ethanol to produce m-DEB.The results show that the spherical nano-ZSM-5 zeolite exhibits better stability and higher alkylation activity at a lower temperature than those of commercial micropore ZSM-5.And then,the spherical nano-ZSM-5 is further modified by La_(2)O_(3) through acid treatment followed by immersion method.The acid treatment causes nano-ZSM-5 to exhibit the increased pore size but decreased the acid sites,and subsequent La_(2)O_(3) loading reintroduces the weak acid sites.As a result,the HNO_(3)-La_(2)O_(3)-modified catalyst exhibits a slight increase in EB conversion and DEB yield in comparison with unmodified one,and meanwhile,it still maintains high m-DEB selectivity.The catalyst after acid treatment achieves higher catalytic stability besides maintaining the high alkylation activity of EB with ethanol.The present study on the spherical nano-HZSM-5 zeolite and its modification catalyst with excellent alkylation ability provides new insights into the production of mDEB. 展开更多
关键词 Zeolite Modification alkylation reaction m-diethylbenzene Catalyst FIXED-BED
下载PDF
Tandem hydroalkylation and deoxygenation of lignin-derived phenolics to synthesize high-density fuels
4
作者 Rui Yu Zhensheng Shen +6 位作者 Yanan Liu Chengxiang Shi Juncong Qu Lun Pan Zhenfeng Huang Xiangwen Zhan g Ji-Jun Zou 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第2期104-109,共6页
Lignin is the most abundant naturally phenolic biomass,and the synthesis of high-performance renewable fuel from lignin has attracted significant attention.We propose the efficient synthesis of high-density fuels usin... Lignin is the most abundant naturally phenolic biomass,and the synthesis of high-performance renewable fuel from lignin has attracted significant attention.We propose the efficient synthesis of high-density fuels using simulated lignin cracked oil in tandem with hydroalkylation and deoxygenation reactions.First,we investigated the reaction pathway for the hydroalkylation of phenol,which competes with the hydrodeoxygenation form cyclohexane.And then,we investigated the effects of metal catalyst types,the loading amount of metallic,acid dosage,and reactant ratio on the reaction results.The phenol hydroalkylation and hydrodeoxygenation were balanced when 180℃ and 5 MPa H_(2)with the alkanes yield of 95%.By extending the substrate to other lignin-derived phenolics and simulated lignin cracked oil,we obtained the polycyclic alkane fuel with high density of 0.918 g·ml^(-1)and calorific value of41.2 MJ·L^(-1).Besides,the fuel has good low-temperature properties(viscosity of 9.3 mm^(2)·s^(-1)at 20℃ and freezing point below-55℃),which is expected to be used as jet fuel.This work provides a promising way for the easy and green production of high-density fuel directly from real lignin oil. 展开更多
关键词 High-density fuel BIOFUEL Hydrogenation alkylation Lignin Phenolics
下载PDF
Pilot Test of Preparing 2-Alkylanthraquinone Using Alkylation-Oxidation Technology
5
作者 Zheng Bo Qian Jianguo +6 位作者 Shi Peng Pan Zhiyong Qie Siyuan Zhang Yueqin Fei Jianqi Qiao Liang Zong Baoning 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS CSCD 2024年第1期88-97,共10页
To expedite the development of industrial technology for producing 2-alkylanthraquinone,a novel pilot test of alkylation-oxidation technology was conducted.The process mainly included anthracene alkylation,separation ... To expedite the development of industrial technology for producing 2-alkylanthraquinone,a novel pilot test of alkylation-oxidation technology was conducted.The process mainly included anthracene alkylation,separation of anthracene and 2-alkylanthracene,oxidation of 2-alkylanthracene,and product purification.Optimal alkylation conditions yielded a 91.1%conversion of anthracene and a 71.73%selectivity for 2-alkylanthracene.To address the separation problem of anthracene and 2-alkylanthracene,solvent-assisted distillation technology was developed,resulting in a 98.9%purity of 2-alkylanthracene and a 91.82%separation yield.When the molar ratio of H2O_(2) to 2-alkylanthracene was 7:1,a 98.96%conversion of 2-alkylanthracene and a 99.94%selectivity for 2-alkylanthraquinone were achieved.A novel composition of 2-alkylanthraquinone,including 2-tert-butylanthraquinone,2-tert-amylanthraquinone,and 2-hexylanthraquinone,was developed.This composition could be effectively separated and purified through a combination of crystallization and washing processes.The elemental composition of the product met the existing standards,and its hydrogenation performance closely matched that of commercially available 2-tert-amylanthraquinone products. 展开更多
关键词 anthracene 2-alkylanthracene 2-alkylanthraquinone alkylation OXIDATION hydrogen peroxide
下载PDF
Regulating^(*)COOH intermediate via amino alkylation engineering for exceptionally effective photocatalytic CO_(2) reduction
6
作者 Chengcheng Chen Qiaoyu Zhang +3 位作者 Fangting Liu Zhengguo Zhang Qiong Liu Xiaoming Fang 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第5期282-291,共10页
Photocatalytic reduction of CO_(2) into fuel represents a promising approach for achieving carbon neutrality,while realizing high selectivity in this process is challenging due to uncontrollable reaction intermediate ... Photocatalytic reduction of CO_(2) into fuel represents a promising approach for achieving carbon neutrality,while realizing high selectivity in this process is challenging due to uncontrollable reaction intermediate and retarded desorption of target products.Engineering the interface microenvironment of catalysts has been proposed as a strategy to exert a significant influence on reaction outcomes,yet it remains a significant challenge.In this study,amino alkylation was successfully integrated into the melem unit of polymeric carbon nitrides(PCN),which could efficiently drive the photocatalytic CO_(2) reduction.Experimental characterization and theoretical calculations revealed that the introduction of amino alkylation lowers the energy barrier for CO_(2) reduction into^(*)COOH intermediate,transforming the adsorption of^(*)COOH intermediate from the endothermic to an exothermic process.Notably,the as-prepared materials demonstrated outstanding performance in photocatalytic CO_(2) reduction,yielding CO_(2)at a rate of 152.8μmol h^(-1) with a high selectivity of 95.4%and a quantum efficiency of 6.6%. 展开更多
关键词 Polymeric carbonnitride Regulate intermediate Photocatalytic CO_(2)reduction Amino alkylation ^(*)COOH adsorption
下载PDF
External photocatalyst-free C-H alkylation of N-sulfonyl ketimines with alkanes under visible light 被引量:1
7
作者 Hai-Yang Song Fang Xiao +5 位作者 Jun Jiang Chao Wu Hong-Tao Ji Yu-Han Lu Ke-Li Wang Wei-Min He 《Chinese Chemical Letters》 SCIE CAS CSCD 2023年第9期134-137,共4页
A simple,practical and eco-friendly visible light-induced alkylation of N-sulfonyl ketamine under metal-,additive-,external photocatalyst-free conditions was developed.This photocatalytic method utilized low cost and ... A simple,practical and eco-friendly visible light-induced alkylation of N-sulfonyl ketamine under metal-,additive-,external photocatalyst-free conditions was developed.This photocatalytic method utilized low cost and abundant alkanes as the atom economy alkyl sources with H2O2as the environmentally beneficial oxidant,allowing for the efficient construction of diverse valuable 4-alkylated sulfonyl ketamines.The N-sulfonyl ketamine played a dual role of reactant and photocatalyst,thus simplifying the reaction system. 展开更多
关键词 Green chemistry External photocatalyst-free N-Sulfonyl ketimines ALKANES alkylation
原文传递
Preparation and Alkylation of Carbon Nanofibers from Polymethyl Methacrylate
8
作者 Stephen Mukhebi Situma Geoffrey Otieno +2 位作者 Austin O. Aluoch Dickson M. Andala James Owour 《Journal of Materials Science and Chemical Engineering》 2024年第9期55-68,共14页
Carbon nanofibers have revolutionized nanotechnology due to their potential applications in emerging frontiers of research and industrial sectors. This can be attributed to their superior properties such as higher mec... Carbon nanofibers have revolutionized nanotechnology due to their potential applications in emerging frontiers of research and industrial sectors. This can be attributed to their superior properties such as higher mechanical strength, unique surface characteristics, and improved adherence that is transmitted into the polymer matrix to form a nanocomposite with improved properties. Polymethyl methacrylate is a common carbon source for the synthesis of carbon nanofibres of its high mechanical strength, thermal stability, and low moisture and water absorbing capacity that allows its products to have several applications. In this work, we report the successful electrospinning of carbon nanofibres from Poly methyl methacrylate and functionalizing the resulting carbon nanofibres. The functionalized carbon nanofibres were analyzed to determine their solubility/dispersion in selected organic solvents, then characterized using Fourier transform infra-red spectroscopy, Raman spectroscopy, scanning electron microscopy combined with Energy dispersive spectroscopy and Thermalgravimetric analysis. 展开更多
关键词 Polymethyl Methacrylate Electrospinning Carbon Nanofibres alkylation
下载PDF
Visible Light Promoted β-C-H Alkylation of β-Ketocarbonyls via a β-Enaminyl Radical Intermediate 被引量:4
9
作者 Dehong Wang Long Zhang Sanzhong Luo 《Chinese Journal of Chemistry》 SCIE CAS CSCD 2018年第4期311-320,共10页
A 5πe carbonyl activation mode is reported on the basis of photo-induced single-electron-transfer (SET) oxidation of a secondary enamine. The resultant β-enaminyl radical intermediate was trapped by a wide range o... A 5πe carbonyl activation mode is reported on the basis of photo-induced single-electron-transfer (SET) oxidation of a secondary enamine. The resultant β-enaminyl radical intermediate was trapped by a wide range of Michael acceptors, producing β-alkylation products of β-ketocarbonyls in a highly efficient manner, 展开更多
关键词 secondary enamine β-enaminyl radical c-h alkylation photoredox catalysis β-ketocarbonyls
原文传递
Elucidating the effect of oxides on the zeolite catalyzed alkylation of benzene with 1-dodecene
10
作者 Shiyong Xing Yan Cui +2 位作者 Tiefeng Wang Jinwei He Minghan Han 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2023年第4期126-135,共10页
In the present work, the effect of oxides on the alkylation of benzene with 1-dodecene was comprehensively investigated over MCM-49 n-heptanol, n-heptaldehyde and n-heptanoic acid were selected as the model oxides her... In the present work, the effect of oxides on the alkylation of benzene with 1-dodecene was comprehensively investigated over MCM-49 n-heptanol, n-heptaldehyde and n-heptanoic acid were selected as the model oxides herein, and obvious decrease of lifetime could be caused by only trace amount of oxides added in the feedstocks. However, the deactivated catalysts were difficult to be regenerated by extraction with hot benzene. Additionally, coke-burning was also proved to be incapable to regenerate the deactivated catalysts mainly for the dealumination during calcination. Further characterizations complementary with DFT calculations were conducted to demonstrate that the deactivation was mainly due to the firm adsorption of oxides on the acid sites. 展开更多
关键词 ZEOLITE 1-DODECENE alkylation OXIDES DEACTIVATION
下载PDF
Synthesis of Fluorene Derivatives Via TfOH-catalyzed Intramolecular Friedel-Crafts Alkylation Reactions
11
作者 ZHOU Ziyang YI Ying +3 位作者 ZHANG Fanglin XU Wengang LU Zhi LUO Tian 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS CSCD 2023年第5期1184-1189,共6页
We devoloped an efficient and simple method to synthesize fluorene derivatives via intramolecular Friedel-Crafts alkylation of chalcones.The transform is catalyzed by TfOH in CH_(3)NO_(2)at 80℃and the yield is up to ... We devoloped an efficient and simple method to synthesize fluorene derivatives via intramolecular Friedel-Crafts alkylation of chalcones.The transform is catalyzed by TfOH in CH_(3)NO_(2)at 80℃and the yield is up to 99%. 展开更多
关键词 FLUORENE intramolecular alkylation TfOH
下载PDF
Platinum-Catalyzed Allylic C-H Alkylation with Malononitriles 被引量:2
12
作者 Lian-Feng Fan Pei-Pei Xie +2 位作者 Pu-Sheng Wang Xin Hong Liu-Zhu Gong 《CCS Chemistry》 CAS 2022年第4期1366-1375,共10页
The direct functionalization of allylic C-H bonds is distinguished by enabling rapid assembly of structural complexity from simple molecules.Although Pd-catalyzed allylic C-H functionalization has been extensively stu... The direct functionalization of allylic C-H bonds is distinguished by enabling rapid assembly of structural complexity from simple molecules.Although Pd-catalyzed allylic C-H functionalization has been extensively studied,the discovery of new catalytic systems remains fairly underdeveloped.Here,we disclose a Pt-catalyzed allylic C-H alkylation of a wide range of α-alkenes by using phosphoramidites as ligands and malononitriles as alkylating reagents.Notably,the combination of chiral ureacatalyzed Michael addition and Pt-catalyzed allylic C-H alkylation can serve as an efficient protocol to access chiral tetrahydropyran with high levels of diastereo-and enantioselectivity.Mechanistic studies suggest that the Pt-catalyzed allylic C-H activation proceeds through a concerted proton and two-electron transfer process,which is analogous to transition state geometries of Pd catalysis. 展开更多
关键词 platinum catalysis PHOSPHORAMIDITE c-h activation allylic alkylation concerted proton and two-electron transfer
原文传递
Understanding the interfacial behaviors of benzene alkylation with butene using chloroaluminate ionic liquid catalyst: A molecular dynamics simulation
13
作者 Jialei Sha Chenyi Liu +3 位作者 Zhihong Ma Weizhong Zheng Weizhen Sun Ling Zhao 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2023年第2期44-52,共9页
To better understand the benzene alkylation with chloroaluminate ionic liquids(ILs) as catalyst, the interfacial properties between the benzene/butene binary reactants and chloroaluminate ILs with varying cation alkyl... To better understand the benzene alkylation with chloroaluminate ionic liquids(ILs) as catalyst, the interfacial properties between the benzene/butene binary reactants and chloroaluminate ILs with varying cation alkyl chain length and different anions were investigated using molecular dynamics(MD) simulations. The results indicate that ILs can obviously improve the interfacial width, solubility and diffusion of reactants compared to H_(2)SO_(4). The longer alkyl chains of cations present a density enrichment at the interface and protrude into the binary reactants phase. Furthermore, the ILs consisting of 1-octyl-3-methylimidazolium cations([Omim]^(+)) and the stronger acidity heptachlorodialuminate anions([Al_(2)Cl_(7)]^(-)) are more beneficial to promote the interfacial width and facilitate the dissolution and diffusion of benzene in both the IL bulk and the interfacial region in comparison to the ones with shorter alkyl chains cations and weaker acidity anions. The information gives us a better guideline for the design of ILs for benzene alkylation. 展开更多
关键词 Benzene alkylation Interfacial behaviors Ionic liquids Molecular dynamics simulation
下载PDF
非血红素铁酶中动态配位变化对C-H键选择性胺化反应的调控机制
14
作者 张璇 刘佳 +2 位作者 廖浪星 王子宽 王斌举 《Chinese Journal of Catalysis》 SCIE CAS CSCD 2024年第7期131-144,共14页
氮杂环丙烷结构广泛存在于天然生物碱中,具有杀菌、抗癌等作用.然而,目前关于生物体系在合成氮杂环丙烷结构过程中如何克服氮杂环丙烷高环张力带来的热力学不利因素,以及如何避免形成热力学更稳定的羟基化副产物的报道较少.TqaL_(NC)酶... 氮杂环丙烷结构广泛存在于天然生物碱中,具有杀菌、抗癌等作用.然而,目前关于生物体系在合成氮杂环丙烷结构过程中如何克服氮杂环丙烷高环张力带来的热力学不利因素,以及如何避免形成热力学更稳定的羟基化副产物的报道较少.TqaL_(NC)酶是目前非血红素酶家族中唯一一种能够依赖α-酮戊二酸活化C-H键,进而生成氮杂环丙烷结构的酶.深入探究TqaL_(NC)酶选择性生成氮杂环丙烷结构并避免羟基化副产物的机制,有助于深入理解非血红素铁酶家族在C-H键活化及官能化过程中的选择性调控机理.本文以TqaL_(NC)酶的晶体结构为基础,采用分子动力学(MD)模拟以及量子力学-分子力学(QM/MM)等多尺度模拟方法对TqaL_(NC)酶与L-缬氨酸(L-Val)、TqaL_(NC)酶与L-异亮氨酸(L-Ile)和F345A-TqaL_(NC)酶与L-异亮氨酸(L-Ile)三个反应过程进行了详细的机理研究.结果表明,TqaL_(NC)酶在反应过程中生成的直立式构象的Fe(Ⅳ)=O物种会通过构象异构化获得赤道面式构象,为底物(L-Val、L-Ile、L-homoalaine)上NH_(3)^(+)与Fe的配位提供结构基础.在水和关键酸性残基的介导下,底物NH_(3)^(+)两次脱去质子与Fe(Ⅳ)=O物种配位,生成HN-Fe(Ⅳ)=O结构.随后,Fe(Ⅳ)=O物种攫取底物H原子,生成HN-Fe(Ⅲ)-OH中间体.此时NH回弹反应比传统的OH回弹反应在动力学上更有优势,因此选择性地生成了氮杂环丙烷产物.在反应过程中,底物侧链与周围氨基酸的位阻效应是影响NH回弹反应能垒的重要因素.通过改变底物侧链大小(L-Val→L-Ile)以及附近氨基酸的突变(F345A)实验,证实了该结论.本文还通过理论计算预测了TqaL_(NC)酶与L-高丙氨酸的反应产物为羟基化产物,并通过新的实验证据进一步支持了理论预测的机理.此外,在HN-Fe(Ⅲ)-OH结构中,通过前线轨道理论分析发现,dπ*Fe-N,dπ*Fe-OH轨道的能量差是影响NH/OH回弹反应能垒的另一重要因素.当底物NH与Fe配位时,其配位作用能够使得dπ*Fe-N以及dπ*Fe-OH轨道有效分裂,这种分裂进而影响了反应路径的选择性,确保氮杂环丙烷产物的生成.综上,本文提出了依赖α-酮戊二酸酶催化合成氮杂环丙烷结构的新机理.研究发现,Fe中心的动态配位效应在实现C-H键选择性胺化反应并避免C-H键羟基化反应中起到了关键作用.该理论为非血红素Fe酶催化的非羟基化反应提供了新的见解,并为探索包括C-N/C-S/C-O等重要生物合成反应新机理的探究提供了新思路. 展开更多
关键词 联合量子力学-分子力学方法 c-h键活化 非血红素酶 胺化反应 羟基化反应
下载PDF
Production of linear alkylbenzene over Ce containing Beta zeolites
15
作者 Shiqi Zhang Shengzhi Gan +1 位作者 Baoyu Liu Jinxiang Dong 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第3期220-227,共8页
Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species dur... Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene. 展开更多
关键词 Beta zeolites CATALYSIS alkylation Long-chain olefins
下载PDF
Alkylene-functionality in bridged and fused nitrogen-rich poly-cyclic energetic materials:Synthesis,structural diversity and energetic properties
16
作者 Man Xu Nanxi Xiang +2 位作者 Ping Yin Qi Lai Siping Pang 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第5期18-46,共29页
From the standpoint of chemical structures,the organic backbones of energetic materials can be classified into aromatic rings,nonaromatic rings,and open chains.Although the category of aromatic energetic compounds exh... From the standpoint of chemical structures,the organic backbones of energetic materials can be classified into aromatic rings,nonaromatic rings,and open chains.Although the category of aromatic energetic compounds exhibits several advantages in the regulation of energetic properties,the nonaromatic heterocycles,assembling nitramino explosophores with simple alkyl bridges,still have prevailed in benchmark materials.The methylene bridge plays a pivotal role in the constructions of the classic nonaromatic heterocycle-based energetic compounds,e.g.,hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX)and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine(HMX),whereas ethylene bridge is the core moiety of state-of-the-art explosive 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(CL-20).In this context,it is of great interest to employ simple and practical bridges to assemble aromatic and nonaromatic nitrogen-rich heterocycles,thereby expanding the structural diversity of energetic materials,e.g.,bridged and fused nitrogen-rich poly-heterocycles.Furthermore,alkyl-bridged poly-heterocycles highlight the potential for the open chain type of energetic materials.In this review,the development of alkyl bridges in linking nitrogen-rich heterocycles is presented,and the perspective of the newly constructed energetic backbones is summarized for the future design of advanced energetic materials. 展开更多
关键词 Energetic materials alkyl bridge strategy Nitrogen-rich azoles Fused heterocycles AZOLES
下载PDF
C-H bond activation of propane on Ga_(2)O_(2)^(2+) in Ga/H-ZSM-5 and its mechanistic implications
17
作者 Zhaoqi Zhao Yunzhu Zhong +1 位作者 Xiaoxia Chang Bingjun Xu 《Chinese Journal of Catalysis》 SCIE CAS CSCD 2024年第9期32-43,共12页
Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified ... Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work.Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga_(2)O_(2)^(2+) species corresponding to the infrared GaH band of higher wavenumber(GaHHW)in reduced Ga/H-ZSM-5,instead of the overall Ga_(2)O_(2)^(2+) species,by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio.This disparity in Ga_(2)O_(2)^(2+) species stems from their differing capacity in completing the catalytic cycle.Spectroscopic results suggest that PDH proceeds via a two-step mechanism:(1)C-H bond activation of propane on H-Ga_(2)O_(2)^(2+) species(rate determining step);(2)β-hydride elimination of adsorbed propyl group,which only occurs on active Ga_(2)O_(2)^(2+) species corresponding to GaHHW. 展开更多
关键词 Propane dehydrogenation Ga_(2)O_(2)^(2+) Activation of c-h bond Ga species
下载PDF
Alkylation of toluene with tert-butyl alcohol over HPW-modified Hβ zeolite 被引量:8
18
作者 王园园 宋华 孙兴龙 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2016年第12期2134-2141,共8页
An Hβ-supported heteropoly acid (H3PW12O40 (HPW)/Hβ) catalyst was successfully prepared by wetness impregnation, and investigated in the alkylation of toluene with tert-butyl alcohol for the synthesis of 4-tert-... An Hβ-supported heteropoly acid (H3PW12O40 (HPW)/Hβ) catalyst was successfully prepared by wetness impregnation, and investigated in the alkylation of toluene with tert-butyl alcohol for the synthesis of 4-tert-butyltoluene (PTBT). X-ray diffraction, scanning electron microscopy, transmis- sion electron microscopy, fourier-transform infrared spectroscopy, inductively coupled plas- ma-optical emission spectrometry, the brunauer emmett teller (BET) method, tempera- ture-programmed NH3 desorption, and pyridine adsorption infrared spectroscopy were used to characterize the catalyst. The results showed that loading HPW on Hβ effectively increased the B acidity and decreased the pore size of Hβ. The B acidity of HPW/Hβ was 142.97 μmol/g, which is 69.74% higher than that of Hβ (84.23 μmol/g). The catalytic activity of the HPW/Hβ catalyst was much better than that of the parent Hβ zeolite because of its high B acidity. The toluene conversion over HPW/Hβ reached 73.1%, which is much higher than that achieved with Hβ (54.0%). When HPW was loaded on Hβ, the BET surface area of Hβ decreased from 492.5 to 379.6 m2/g, accompa- nied by a significant decrease in the pore size from 3.90 to 3.17 nm. Shape selectivity can therefore play an important role and increase the product selectivity of the HPW/Hβ catalyst compared with that of the parent Hβ. PTBT (kinetic diameter 0.58 nm) can easily diffuse through the narrowed pores of HPW/Hβ, but 3-tert-butyltoluene (kinetic diameter 0.65 nm) diffusion is restricted because of steric hindrance in these narrow pores. This results in high PTBT selectivity over HPW/Hβ (around 81%). The HPW/Hβ catalyst gave a stable catalytic performance in reusability tests. 展开更多
关键词 alkylation Toluenetert-Butyl alcohol H3PW12O40 B acidity zeolite
下载PDF
Effect of ZSM-5 zeolite morphology on the catalytic performance of the alkylation of toluene with methanol 被引量:9
19
作者 Hongyu Wu Min Liu +4 位作者 Wei Tan Keke Hou Anfeng Zhang Yiren Wang Xinwen Guo 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2014年第4期491-497,共7页
A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the... A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the addition of NaC1 and crystal seed. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF) and temperature-programmed desorption of ammonia (NH3-TPD) were used to characterize these samples. The samples were tested with toluene methylation reaction. The modified sample composed of spherical particles with 3 μm crystal particles on the surface had a para-xylene selectivity of 95% and maintained 79% of the initial conversion after running the reaction for 50 h. This modified samole showed the best stability amonz the tested three modified samoles. 展开更多
关键词 alkylation TOLUENE METHANOL MORPHOLOGY ZSM-5
下载PDF
Benzene alkylation with methanol over phosphate modified hierarchical porous ZSM-5 with tailored acidity 被引量:15
20
作者 Jinghui Lyu Hualei Hu +7 位作者 Carolyn Tait Jiayao Rui Caiyi Lou Qingtao Wang Wenwen Han Qunfeng Zhang Zhiyan Pan Xiaonian Li 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2017年第9期1187-1194,共8页
The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with t... The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus. Meanwhile, side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta-xylene were suppressed efficiently. The acid strength and sites amount of Br?nsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene, whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers. 展开更多
关键词 Hierarchical porous ZSM-5 Phosphate modification Benzene alkylation with methanol XYLENE
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部