超稳丫沸石制备技术对沸石铝分布的影响 Ⅰ.两种典型超稳Y沸石表面-体相组成的XPS研究

用XPS考察了USY和FSY超稳Y型沸石及其起始原料NH_4Y沸石的表面组成,并结合Ar~+刻蚀技术与其体相组成进行了比较。结果表明,NH_4Y沸石的铝分布基本均匀一致,经超稳化处理后,沸石表面组成发生了很大的变化。用(NH_4)_2SiF_6液相脱铝补硅法制备的FSY表面呈缺铝特征,其表面铝原子浓度比体相低8～10％;而用传统水热法制备的USY具有典型的富铝表面,其表面铝原子浓度比体相高30％左右。USY表面富铝主要是由于USY“次表面”(Subsurface)附近的非骨架铝类迁移到表面所致。内层的非骨架铝类在常规水热超稳处理条件下一般则很难迁移,仍然留有在USY晶体内部。     

添加β沸石的烃类裂化催化剂性能研究

采用固体硅源、铝源和四乙基氢氧化铵（TEAOH）在极浓体系中成功合成了硅铝摩尔比（SiO₂/Al₂O₃）分别为30和150的β沸石。同时用硅铝摩尔比为30的β沸石为原料,在70℃下采用草酸脱铝制备了硅铝摩尔比接近150的样品。直接合成或经脱铝改性的β沸石采用XRD、SEM、吡啶吸附红外光谱和N2吸附对其晶相、酸性、比表面积和孔体积进行了表征。将三种β沸石分别作为烃类裂化催化剂的活性组分添加剂,对其催化剂的性能进行了评价。结果表明,三种β沸石的引入都可以提高裂化催化剂的活性和改善产品分布,低硅β沸石催化剂能改善催化剂的异构化反应性能和提高乙烯、丙烯的选择性,高硅β沸石或脱铝β沸石催化剂有利于裂化汽油中烯烃的芳构化和C4烯烃产率的提高,并可减少结焦。     

改性丝光沸石催化二甲醚气相羰化的反应性能

对比研究了铜/钾改性丝光沸石、铜改性丝光沸石、H型丝光沸石上二甲醚气相羰化制醋酸甲酯的反应行为,并通过XRD、NH3-TPD、SEM、TEM及FT-IR等对反应前后催化剂进行了表征分析.丝光沸石负载Cu后,改变了反应过程中催化剂上积炭中间物种的形态,由石墨状"硬碳"转变为易于消除的"软碳"(结焦),从而提高了羰化反应的活性和稳定性;K改性的Cu/MOR沸石,由于K对沸石表面强酸位的调变,抑制了二次反应的发生,进一步提高了二甲醚气相羰化反应的稳定性.     

ZrO_2负载量对ZrO_2-脱铝沸石在生物质油催化裂化中的性能影响

用浸渍法制备了ZrO_2负载量不同的ZrO_2-脱铝沸石作为生物质油催化裂化反应催化剂,并用XRD、SEM、TPD和FT-IR等对复合氧化物的晶相结构、酸种类、酸量等进行了表征。结果表明,ZrO_2-脱铝沸石表面存在B和L酸中心,并以B酸为主,随着负载量增多,其B酸中心增加,酸强度增强,对生物质油都有催化裂化的反应活性,其中10%ZrO_2-脱铝沸石表现出较好的裂化反应活性,小分子裂化产物分布较多,较强的酸中心,能促进裂化反应和含氧有机物的脱羰、脱羧,脱氧率较好,但结焦程度亦增大。     

改性Y沸石上的氢转移反应

本文试图用环已烯和邻二甲苯两典型反应考察改性Y沸石的氢转移反应性能。发现在改性Y沸石上环已烯的氢转移, 异构化和聚合反应时发生。在反应开始时SY沸石的氢转移反应和异构化反应活性与铝含量之间的关系与沸石强酸量和铝含量的关系一致, 呈火山形曲线, 极大值在Al/(Al+Si)为0.15左右, 结焦以后反应总转化迅速下降, 且氢转移活性和异构化活性随铝含量减少而单调下降。USY沸石的氢转移活性大幅度降低。在改性Y沸石上邻二甲苯异构化和歧化反应同时进行, SY沸石的歧化反应变化规律与环乙烯氢转移反应相似。当沸石样品中有大量非质子酸位存在时, 两个反应的数据会出现予盾。     

不同硅铝比β沸石的理化性质及烃类催化裂化活性

采用润湿态固相转化方法按照投料硅铝摩尔比(n(SiO2)/n(Al2O3))分别为30、60、150、300、500和纯硅时合成了β沸石, 化学法和X射线荧光(XRF)测定产物的硅铝比和反应初始凝胶基本一致. 利用X射线衍射(XRD)、红外光谱(FT-IR)、扫描电镜(SEM)、氨程序升温脱附(NH3-TPD)和低温N2吸附对系列样品的物相、水热稳定性、晶体形貌、酸性以及表面积和孔体积做了系统的表征. 并将该系列样品作为活性组分添加剂, 以高岭土为基质分别制备烃类裂化催化剂, 对其催化裂化性能进行了评价. 结果表明, 不同硅铝比β沸石添加到裂化催化剂均可以提高其裂化活性, 改善催化剂的抗积炭性能, 硅铝比为150的β沸石催化剂在保持较高裂化活性的前提下, 汽油收率最高, 抗积炭性能也较好, 是优选的裂化催化材料.     

微波法高度分散CuCl2-β沸石上CO吸附的IR光谱研究

近年来, 人们发现含铜沸石对NO和CO等有害气体的直接分解具有较高的活性和较好的稳定性[1～3]. 催化剂的活性与其铜含量密切相关, 而由传统离子交换法制得的沸石催化剂中铜含量较低, 且受沸石骨架中铝含量的限制[4]. 直接固态离子交换法是将金属离子引入沸石中的有效途径[5～7]. 本文采用微波法制备了CuCl2高度分散的β沸石, 用XRD和29Si MAS NMR对催化剂进行了表征, 并以CO吸附IR光谱法考察了CuCl2在β沸石中的扩散机理.     

T-81型丝光沸石催化剂烧焦动力学的研究

考察烧焦动力学行为,寻找适宜的再生条件,对再生反应器的设计是十分必要的。已有大量的文章论述了关于硅铝型及Y型分子筛催化剂上的结焦和烧焦过程的模型,由于烧焦方式与焦在催化剂酸位上的生成方式有关,因此上述众多的模型都不能直接用于描述T-81型丝光沸石的烧焦过程。本文以Hashimoto等人提出的烧焦是烧碳和烧氢的复合反应为理论基础,研究了T-81型丝光沸石催化剂的烧焦动力学,为确定最佳反应条件和再生反应器的设计提     

苯甲醚在复合催化剂上的催化酰化

复合催化剂首次用于催化苯甲醚与酰化剂乙酰氯的酰化反应.发现不同沸石的单独使用仅给出很低产率的对-甲氧基苯乙酮.但是由HY沸石(硅铝比=40)或USY(超稳Y沸石)和SnO组成的复合催化剂的催化活性比单独使用沸石时高得多.增加由USY沸石和不同量的SnO组成的复合催化剂中的SnO的量,导致对-甲氧基苯乙酮产率的提高.由H型沸石(HY和H-ZSM-5沸石)和SnO组成的复合催化剂在苯甲醚与乙酰氯的酰化反应中的催化活性主要取决于所用沸石的硅铝比.     

改性氧化硅-氧化铝和丝光沸石催化剂上的二甲苯异构化

非晶质的氧化硅-氧化铝和晶质的丝光沸石催化剂的表面上都有表面OH。可用硅烷偶联剂进行表面改性。由于催比剂的孔径不同以及硅烷偶联剂分子尺寸差异,对氧化硅-氧化铝的改性是在整个内、外表面上进行;而对丝光沸石,由于偶联剂分子不能进入沸石的内孔道中,所以这种改性只能在沸石窗口及外表面上进行。另外,沸石催化剂上酸量适中,酸中心分布较为理想,所以改性的沸石催化剂的选择性,总是比硅铝催化剂有较大增高。改性用的硅烷偶联剂以二甲基二乙氧基硅烷较为适宜。改性后的非晶质硅铝催化剂的对二甲苯选择性由14.6增到34.0%,晶质丝光沸石催化剂改性后由33.3增到43.7%。增加催化剂用量可提高对二甲苯的摩尔百分数到23%,接近它的理论值。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.