一段反应法制备宽/双峰聚乙烯催化剂的研究进展

阐述了采用一段反应法制备宽/双峰聚乙烯催化剂的研究开发进展,并根据催化剂的组成和结构,将催化体系归纳为复合催化剂和单组分催化剂.复合催化剂包括茂金属/Ziegler-Natta复合催化剂、不同茂金属复合催化剂、铬系/Ziegler-Natta复合催化剂、茂金属/后过渡金属复合催化剂、非茂单活性中心/茂金属复合催化剂、非茂单活性中心/Ziegler-Natta复合催化剂和不同后过渡金属复合催化剂.复合催化剂中多活性组分具有不同的链增长、链转移、链终止速率常数,从而在聚合反应中得到不同相对分子质量的聚合物,导致其相对分子质量分布加宽,因而复合催化剂可用于一段反应法制备宽/双峰聚乙烯.单组分催化剂包括单核茂金属催化剂、多核茂金属催化剂、后过渡金属催化剂及其它单组分催化剂.单组分催化剂可用于一段反应法制备宽/双峰聚乙烯,其催化机理是中心金属原子与主配体、辅配体、助催化剂、其它添加剂及载体形成了多种活性中心.     

单层分散阈值和负载型催化剂的阈值效应

自发单层分散原理认为,许多负载型催化剂的活性组分可在载体表面自发分散。活性组分在载体表面的单层分散阈值可通过XRD相定量外推法等实验方法进行测定。通过单层分散阈值的测定可获取负载型催化剂表面结构、分散状态的有益信息,并为选择最佳的催化剂制备工艺条件提供依据。许多负载型催化剂活性组分的配比都可通过考察其单层分散阈值得以优化。负载型催化剂的许多物理化学性质突变值都与其单层分散阈值相联系,催化剂的阈值效应是明显的,阈值效应的提出为催化剂的研究提供了指导。     

Cu/Al2O3催化剂的改性及其对NO选择性还原的催化性能

 以 γ-Al2O3 为载体,采用SO2-4进行改性并添加助剂La,再负载上Cu2+, 制备了改性的Cu/Al2O3催化剂(Cu/La/SO2-4/Al2O3),考察了SO2-4改性和助剂La对催化剂在富氧条件下催化丙烯选择性还原NO 反应的影响,并借助红外光谱、X射线衍射、扫描电镜、热重分析、程序升温还原和X射线光电子能谱等方法研究了改性催化剂的性能与结构的关系. 结果表明,改性催化剂的催化活性较高, NO转化率可高达83.7%. 采用SO2-4改性可促进催化剂表面的酸量增加,并促使产生B酸中心; 助剂La可提高Cu物种的分散程度,并提高催化剂的热稳定性和还原性,从而可有效提高催化剂在富氧条件下对丙烯选择性还原NO反应的催化活性和水热稳定性.     

燃料掺水燃烧研究的新进展*

本文论述了有机物水蒸气重整催化剂、水煤气反应催化剂、水裂解催化剂等制氢催化剂在掺水燃料中的应用可提高热利用率并减少尾气中的毒性气体。文章还讨论了掺水燃料的分散系统结构与燃烧焓的关系并给出了作者的有关实验方法。     

多巴胺为前驱体过渡金属与N共同掺杂的碳纳米管催化剂ORR性能研究

采用多巴胺的自氧化聚合在多壁碳纳米管表面进行聚合沉积修饰,经热处理可得到氮掺杂的碳纳米管催化剂,通过调整沉积次数可控制表面聚多巴胺C-N膜的厚度,从而调控N的掺杂量.研究沉积次数对多壁碳纳米管催化剂表面形貌、化学组成及原子结合形态的影响,并考察N掺杂的多壁碳纳米管催化剂的氧还原反应活性.在此基础上,用多巴胺配合Mn、Fe离子进行共同聚合沉积,热处理后得到Mn(Fe)、N共同掺杂的多壁碳纳米管催化剂,对催化剂进行了多种测试和电化学表征.循环伏安和线性扫描的电化学表征表明,N掺杂可有效提高催化剂的氧还原反应(ORR)活性,C-N膜的厚度会影响催化剂性能,Mn(Fe)-N@MWCNTs催化剂的氧还原活性高于只有N掺杂的催化剂,两种催化剂氧还原反应均为4电子反应路径,可直接将氧气还原成H_2O,且F e-N@MWCNTs催化剂表现出较好的抗甲醇能力.SEM照片可以看到聚多巴胺在碳纳米管表面形成C-N膜;R aman分析表明聚多巴胺沉积后提高了催化剂表面的无序性,缺陷增多;XPS表征显示过渡金属的掺杂改变了CN_x的结合状态.     

对硝基苯甲酸乙酯的合成

以硫酸氢钾为催化剂,研究了对硝基苯甲酸和乙醇反应生产对硝基苯甲酸乙酯的合成工艺.考察了催化剂用量、反应时间、醇酸物质的量之比、带水剂用量以及催化剂重复使用次数对酯化率的影响,确定了最佳反应条件.当对硝基苯甲酸的用量为0.015mol,无水乙醇为0.060mol,反应时间为2.0h,带水剂环己烷用量为15mL,催化剂硫酸氢钾的用量为0.4g,对硝基苯甲酸乙酯的酯化率可达到91.65%.在此条件下,催化剂的催化活性高,反应条件温和,该合成方法简便,产品收率优良,催化剂可重复使用,且价格低廉.     

磁性氧化铝负载Pd催化剂对硝基苯加氢催化活性的研究

采用微乳法室温下合成了γ-Al2O3/SiO2/Fe3O4磁性复合颗粒为载体负载的纳米钯催化剂.利用透射电镜、x射线光电子能谱和振动样品磁强计等手段对催化剂进行表征,评价了催化剂对硝基苯加氢制苯胺反应的催化活性.结果表明,通过调控反应条件,可在平均粒径为200nm左右的磁性载体上负载10m左右均匀分散的Pd纳米颗粒,整个催化剂呈现超顺磁性;在催化剂磁含量为8%、Pd负载量1%、反应时间40min、反应温度50℃,反应压力0.5MPa条件下,硝基苯的转化率可以达到100%,催化剂重复使用10次时仍可保持很高的催化活性,并可在外磁场作用下快速分离与回收.     

腐植酸负载Pd/Ni双金属催化剂对Heck反应催化性能的研究

制备了腐植酸负载Pd/Ni双金属催化剂, 该催化剂能够成功催化溴苯与丙烯酸、苯乙烯等乙烯基化合物的Heck反应, 产率均在85%以上; 催化剂能够不同程度地重复使用, 在催化溴苯与丙烯酸反应中, 催化剂重复使用3次后仍可得到42.9%的产率, 而在催化溴苯与苯乙烯反应中, 催化剂重复使用7次后也可得到26.7%的产率; 并且对不同取代基芳基卤与丙烯酸的反应也有很好的催化活性.     

磁性纳米颗粒负载钯催化剂对Heck反应的催化活性

采用水热法合成了碳包埋磁性纳米复合颗粒C/(Au@Fe),并以之为载体制备了纳米钯催化剂,利用透射电镜、X射线光电子能谱和振动样品磁强计等手段对催化剂进行了表征,评价了催化剂对Heck反应的催化活性.结果表明,催化剂的平均粒径约为300nm,表面覆盖着一层粒径为12nm的钯颗粒,整个催化剂呈现超顺磁性.对于碘代苯与丙烯酸之间的Heck反应,在乙酸钠或三乙胺碱性条件下反应4h,碘代苯转化率可达95%以上.催化剂重复使用10次时仍可保持很高的催化活性(碘代苯转化率88%).对于其他不同反应底物之间的Heck反应,催化剂同样显示有较高的催化活性.催化剂可稳定分散于反应体系中,并可在外磁场作用下快速与反应体系分离.     

多核钯（Ⅱ）－镍（Ⅱ）（1：1）酞菁对Heck反应的催化研究

使用多核钯（Ⅱ）－镍（Ⅱ）（１：１）酞菁作催化剂催化Ｈｅｃｋ反应，得到１２种较高产率的取代Ｅ－１，２－二苯乙烯、Ｅ－肉桂酸和Ｅ－甲基肉桂酸。催化剂的催化活性可与均相催化剂乙酸钯（Ⅱ）的催化活性相比。本文所用催化剂易制备且可重复使用１４次左右。     

Synthesis of 15‐Cyano‐12‐oxopentadecano‐15‐lactone and 15‐Cyano‐ 12‐oxopentadecano‐15‐lactam

15‐Cyano‐12‐oxopentadecano‐15‐lactone was synthesized in 59% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by reaction with trimethylsilylcyanide, hydrolysis, ring‐expansion, and Nef reaction. A two‐step, one‐pot synthesis of intermediate 2‐hydroxy‐4‐(1‐nitro‐2‐oxycyclododecyl)butanenitrile from 3‐(1‐nitro‐2‐oxocyclododecyl)propanal was developed and the conditions for the Nef reaction were studied. 15‐Cyano‐12‐oxopentadecano‐15‐lactam was synthesized in 40% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by Strecker reaction, ring‐expansion, and Nef reaction. The conditions for the Strecker and Nef reactions were studied. The structures of the target compounds, intermediates, and by‐product were characterized by IR, ¹H‐ and ¹³C‐NMR, and elemental analysis or MS.     

Hydrolysis Reaction of N-Phosphoryl-α-, β- and γ-amino Acids Studied by HPLC

The hydrolysis reactions of N-（O,O＇diisopropyl）phosphoryl-L-α-alanine （DIPP-L-α-Ala）, N-（O,O＇diisopropyl）- phosphoryl-D-α-alanine （DIPP-D-α-Ala）, N-（O,O＇-diisopropyl）phosphoryl-β-alanine （DIPP-β-Ala） and N-（O,O＇-diisopropyl）phosphoryl-γ-amino butyric acid （DIPP-γ-Aba）, were studied by HPLC and their hydrolysis reaction kinetic equations were obtained. Under acid conditions, the reaction rate of DIPP-L-α-Ala was close to that of DIPP-D-α-Ala and the same rule was true between DIPP-β-Ala and DIPP-γ-Aba. Meantime, the reaction rate of DIPP-L/D-α-Ala was as 10 times as that of DIPP-β-Ala or DIPP-γ-Aba. Under basic conditions, the hydrolysis reactions of DIPP-β-Ala and DIPP-γ-Aba almost did not take place and the reaction rate of DIPP-L/D-α-Ala was about 1/10 of that under acid conditions. Moreover, theoretical calculation further illuminated the differences of the hydrolysis rate from the view of energy. The results would provide some helpful clues to why nature chose a-amino acids but not other kinds of analogs as protein backbones.     

Novel synthesis of 3‐phenylazo‐1,5‐benzothiazepines, ‐1,5‐benzoxazepines and ‐1,5‐benzodiazepines via a one‐pot reaction

Novel polysubstituted ‐1,5‐benzothiazepine, ‐1,5‐benzoxazepine, and ‐1,5‐benzodiazepine were prepared in good yields by the reaction of hydrazono derivatives with o‐thioaminophenol, o‐aminophenol and o‐phenylenediamine via a one‐pot reaction.     

The Stereoselective Total Synthesis of (6S)‐5,6‐Dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one via Prins Cyclization

The stereoselective total synthesis of an antiproliferative and antifungal α‐pyrone natural product (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one is described. The key steps involved are the Prins cyclization, Mitsunobu reaction, and ring‐closing metathesis reaction.     

Quinolone analogues 6 [1‐5]. Synthesis of 3‐halogeno‐1‐methylpyridazino[3,4‐b]quinoxalin‐4(1H)‐ones

The reaction of the quinoxaline N‐oxides 7a,b with diethyl ethoxymethylenemalonate gave the 1‐methylpyridazino[3,4‐b]quinoxaline‐4,4‐dicarboxylates 8a,b , whose reaction with N‐bromosuccinimide or N‐chlorosuccinimide afforded the 3‐halogeno‐1‐methylpyridazino[3,4‐b]quinoxaline‐4,4‐dicarboxylates 9a‐d. The reaction of compounds 9a‐d with hydrazine hydrate resulted in hydrolysis and decarboxylation to provide the 3‐halogeno‐1‐methylpyridazino[3,4‐b]quinoxaline‐4‐carboxylates 10a‐d , whose reaction with nitrous acid effected oxidation to furnish the 3‐halogeno‐4‐hydroxy‐1‐methylpyridazino[3,4‐b]quinoxaline‐4‐carboxylates 11a‐d , respectively. The reaction of compounds 11a‐d with hydrazine hydrate afforded the 3‐halogeno‐1‐methylpyridazino[3,4‐b]quinoxalin‐4‐ols 12a‐d , whose oxidation provided the 3‐halogeno‐1‐methylpyridazino[3,4‐b]quinoxalin‐4(1H)‐ones 6a‐d , respectively. Compounds 6a‐d had antifungal activities in vitro.     

Chemoselective Synthesis of β‐Amino Ester or β‐Lactam via Sonochemical Reformatsky Reaction

A series of β‐amino esters were synthesized by the reaction of N‐tosyl aldimine or N‐hydroxy aldimine with bromoacetate by sonochemical Reformatsky reaction. The β‐N‐hydroxyamino ester was obtained and the formed sensitive hydroxylamino functionality was resistant under the reaction condition. The β‐lactam also was synthesized by the reaction of N‐p‐methoxy aldimine as reacting substrate under this sonochemical Reformatsky reaction condition.     

One‐Pot Synthesis of 4‐(2,3‐Dihydro‐2‐hydroxy‐1,3‐dioxo‐1H‐inden‐2‐yl)‐Substituted 1‐Aryl‐1H‐pyrazole‐3‐carboxylates via a Tandem Three‐Component Reaction

The hitherto unreported, highly functionalized 1H‐pyrazole‐3‐carboxylates 3 have been synthesized in good yields via a one‐pot three‐component domino reaction of phenylhydrazines, dialkyl acetylenedicarboxylates, and ninhydrin under mild conditions for the first time. No co‐catalyst or activator is required for this multicomponent reaction, and the reaction is, from an experimental point of view, simple to perform (Scheme 1). The structures of compounds 3 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization/addition reaction is proposed (Scheme 2).     

立体选择性合成2-(a-噻吩甲酰基)-3-取代苯基-4-乙氧羰基-5-甲基-反式-2,3-二氢呋喃

溴化(a-噻吩甲酰基)甲基三苯鉮1与3-取代苯甲叉基-2,4-戊二酮 2以碳酸钾为碱,在苯中55℃条件下反应,可以较好的收率、高立体选择性地生成反-2-(a-噻吩甲酰基)-3-取代苯基-4-乙氧羰基-5-甲基-2,3-二氢呋喃3。产物结构均经波谱予以确定。本文还提出了生成产物的可能机理。     

Photoinduced and thermal reactions of α‐cyano‐β‐bromomethylcinnamide with 1‐benzyl‐1,4‐dihydronicotinamide

The photoinduced reaction of a mixture of (Z)‐α‐cyano‐β‐bromomethylcinnamide (1) and (E)‐α‐cyano‐β‐bromomethylcinnamide (2) with 1‐benzyl‐1, 4‐dihydronicotinamide produces a mixture of the (E)‐ and (Z)‐ isomers of α‐cyano‐β‐methylcinnamide (3 and 4). Using spin‐trapping technique for monitoring reactive intermediate, it is shown that the reaction proceeds via electron transfer‐debromination‐H abstraction mechanism. The thermal reaction of the same substrate with BNAH at 60°C in the dark gives three products: the (E)‐ and (Z)‐isomers of α‐cyano‐β‐methylcinnamide and a dehydrodimeric product; 2, 7‐dicyano‐3, 6‐diphenylocta‐2, 4, 6‐trien‐1, 8‐dioic amide (7). Based on product analysis, scavenger experiment and cyclic voltammetry, an electron transfer‐debromination‐disproportionation mechanism is proposed.     

Heterocyclization reaction of 2‐(2‐methylaziridin‐1‐yl)‐3‐ureidopyridines under appel's conditions

The reaction of 2‐(2‐methylaziridin‐1‐yl)‐3‐ureidopyridines 12 with triphenylphosphine, carbon tetra‐chloride, and triethylamine (Appel's conditions) led to the corresponding carbodiimides 13 , which underwent intramolecular cycloaddition reaction with aziridine under the reaction conditions to give the pyridine‐fused heterocycles, 2,3‐dihydro‐1H‐imidazo[2′,3′:2,3]imidazo[4,5‐b]pyridines 16 and 12,13‐dihydro‐5H‐1,3 ‐benzodiazepino [2′,3′:2,3] imidazo[4,5‐b]pyridines 17 .