沸石分子筛的表面改性技术进展

沸石分子筛的改性技术与这类材料的合成及应用一样相当大地推动了沸石化学的发展。本篇文章引用了至少90篇文献概括地介绍了最近发展起来的三种沸石表面改性方法:沸石内配位化学、化学蒸汽沉积和沸石的表面有机金属化学。     

一种新型共生沸石(T-L)的合成与表征

在Na₂O-K₂O-Al₂O₃-SiO₂-H₂O体系中水热合成了一种新型的共生沸石, 它由L型沸石生长在T型沸石的一端而形成, 称之为T-L型沸石. 通过XRD, SEM, TEM, EDX, IR等手段对其进行了初步的表征. SEM相片表明这种沸石具有特殊的铆钉状外形; 在TEM相片上可以清楚地看到L型沸石的大孔道, 此孔道与L型沸石的表面垂直. 通过EDX的数据计算发现共生沸石的两相有不同的骨架硅铝比: T型沸石部分Si/Al＝3.71, L型沸石部分Si/Al＝3.41. 在该样品中B酸大于L酸.     

用沸石吸收微波性能表征沸石特性的研究

研究了开放体系下微波加热沸石的规律,发现脱水的沸石能有效吸收微波,自身升温很快,如脱水NaA沸石400W功率下在100s内被加热到1473K.讨论了沸石晶体结构、硅铝比、可交换离子种类对沸石吸收微波的影响.不同类型的沸石,或同一类型但硅铝比不同的沸石,或不同离子交换的同一种沸石在同一功率下具有不同的升温速率,所能达到的最高温度也不尽相同,从而表明沸石吸收微波的性能有可能用来表征沸石的微观特性.沸石在不同功率下吸收微波性能不同,功率越大,升温越快.     

不同孔结构两亲性沸石的制备及其对相界面反应的催化性能

 通过三甲基氯硅烷(TMS)对沸石表面进行修饰,制得了两亲性沸石样品TMS-Hβ, TMS-HY和TMS-HZSM-5,并采用X射线衍射、红外光谱、水饱和吸附量测定和酸碱滴定等手段对改性样品进行了表征. TMS对这三种母体沸石的改性结果有所不同: 对于HZSM-5沸石, TMS仅在外表面修饰; 对于Hβ沸石,少量TMS进入沸石孔道; 而对于HY沸石, TMS则导致沸石结构部分坍塌. 两亲性TMS-HZSM-5和TMS-Hβ沸石在乙酸异戊酯相界面水解反应中表现出明显优于各自母体沸石的催化性能. 两亲性沸石表面硅烷基的稳定性对其催化性能有一定的影响. 相对于TMS-HZSM-5沸石, TMS-Hβ沸石表面硅烷基的稳定性较强; 在较高的相界面反应温度下, TMS-Hβ样品仍能维持两亲性能,表现出较高的催化活性.     

二氧化锡纳米粒子在高硅TON，MFI和FAU型沸石外表面的形成和聚集

将高硅TON, MFI和FAU沸石分别浸渍于SnCl₂溶液，再于873 K温度下焙烧，在高硅TON,MFI和FAU沸石外表面制备出二氧化锡纳米粒子。用XRD和SAED表征生成物的物相，TEM表征形成二氧化锡纳米粒子的形貌、尺寸和聚集状态。结果显示：在TON, MFI和FAU沸石外表面形成二氧化锡纳米粒子的尺寸分别在8 nm, 10-80 nm和6 nm。在室温下用40%的氢氟酸分解SnO₂-TON和SnO₂-MFI分别得到二氧化锡微胶囊和网状的二氧化锡纳米结构。同在NaY沸石表面形成的纳米二氧化锡比较，在具有一维孔道体系的TON沸石和二维孔道体系的MFI沸石外表面形成的纳米二氧化锡的形貌与聚集状态都不相同，这表明沸石的骨架类型、表面结构与特性在沸石外表面形成二氧化锡纳米结构时起重要作用。     

高硅沸石计算晶格能与骨架拓扑结构相关

应用晶格能极小化技术计算了十九种骨架拓扑结构的高硅沸石的全硅骨架晶格能。采用一元线性回归分析、多元线性回归分析和人工神经网络误差反传算法（ＢＰ），将这十九种拓扑结构高硅沸石的全硅骨架晶格能计算值与它们的骨架拓扑结构参数相关。预测结果与计算各能符合良好，表明晶格能与配位序（Ｎ↑－２￣Ｎ↑－４）具有优良的多元线性关系。利用多元线性回归方程对七种结构的高硅沸石的全硅骨架晶格能进行了预测。     

微乳液法合成沸石/介孔二氧化硅复合微球

利用简单微乳液自组装体系, 制备了介孔二氧化硅与Y型或Ti-MWW沸石晶体复合形成的沸石/介孔二氧化硅微球(ZMMS). 硅源正硅酸四丁酯与阳离子型季铵盐表面活性剂形成稳定的O/W微乳液形成大颗粒, 沸石颗粒由于疏水作用而进入油相, 同时, 季铵盐表面活性剂和正硅酸四丁酯组装形成介孔材料. 优化合成条件可以有效控制复合微球的沸石/介孔二氧化硅质量比(0～2.3)和直径(186～965 μm). 两种沸石/介孔二氧化硅复合微球材料的介孔孔径分别为3.98 nm(Y型沸石)和3.75 nm (Ti-MWW型沸石). Ti-MWW沸石/介孔二氧化硅复合微球在液相催化环氧化反应中表现出良好的机械强度, 并且能够达到与Ti-MWW沸石原粉相当的催化活性.     

沸石催化剂的蒸汽热裂过程

本文利用蒸汽热裂装置考察了Ｍ、Ｌ、β和ＺＳＭ－５型沸石及其改性沸石催化剂的蒸汽热裂过程的催化性能，并用ＴＰＤ、ＴＰＲ等法测定其酸碱和氧化还原性能。发现碱性沸石本身的碱性太弱，活性不高，沸石在负载碱或碱土金属氧化物后活性有所增长，由于碱或碱土金属氧化物遇水后易生成氢氧化物，致使其活性降低，甚至丧失；且该催化剂易被Ｈ２及ＣＯ２中毒。沸石负载过渡金属氧化物后，它可与水相互作用发生氧化还原循环反应，具有类     

离子选择电极法测定洗涤剂用沸石的钙离子交换性能

1 引言采用EDTA滴定、ICP和AA法测定洗涤剂用沸石的钙离子交换量时.需要将溶液与沸石分离后进行,因而不易测定交换过程中沸石的钙离子交换速率.而采用ISE法,可以在沸石与钙离子交换时,实时测定溶液中钙离子浓度随交换时间的变化,求得钙离子交换速率.本文采用ISE法测定洗涤剂用沸石的钙离子交换速率及交换量.2 实验部分2.1 仪器与试剂 pXS-215型离子活度计(上海雷磁仪器厂);钙离子选择电极(ISE)和甘汞电极(上海雷磁仪器厂);记录仪(上海大华仪器厂).洗涤剂用4A沸石(山东铝厂),0.1mol/L标准CaCl_2溶液,0.5mol/L NaOH溶液.     

HL/HW复合沸石对烃类催化裂化催化剂性能的影响

将不同HW沸石含量(以W及L沸石的XRD特定峰强度Iw/IL值表示HW沸石在HL/HW复合沸石中的含量)的HL/HW复合沸石与REUSY沸石按相同比例复配后作为烃类催化裂化催化剂的活性组分,采用标准轻油微反方法对催化剂进行了活性评价(MAT),考察了不同HW含量的HL/HW复合沸石对催化剂活性、反应产物分布、汽油产品辛烷值及催化剂上积炭的影响.结果表明,当,Iw/IL值在0～0.12变化时,MAT指数和汽油收率逐渐上升,比积炭逐渐减少,气体收率先减后增;当Iw/IL值大于0.12时,MAT指数、气体收率和汽油收率均下降,比积炭总体呈增加趋势;当Iw/IL值为0.12时,评价的综合指标达到最佳,与不加HL及HW沸石的参比样品相比,汽油产品的芳烃含量和辛烷值分别提高了9.85%和3.01%,烯烃含量下降了1.30%.     

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%.     

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.     

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.     

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.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.