不同环大小分子筛对钼基分子筛催化剂上甲烷无氧芳构化反应的影响

 钼基分子筛催化剂，由于不同分子筛的孔道大小及孔道形状不同\r\n，对甲烷芳构化反应表现出不同的催化性能．具有8元环孔道结构的小\r\n孔ERS－7分子筛没有催化活性，说明甲烷的芳构化反应离不开分子筛孔\r\n道的择形作用，较小的孔道中不能生成苯等芳烃．具有10元环孔道结构\r\n的ZSM－5，ZSM－11和ZRP－1三种分子筛具有较好的催化性能，但由于\r\n其孔道大小及孔道形状的差别在催化行为上表现出一定的差异．具有1\r\n0元环和12元环孔道结构的MCM－22分子筛，尤其对苯等轻芳烃而言，催\r\n化性能最佳．具有12元环孔道结构的JQX－1以及中孔分子筛SBA－15，\r\n虽然具有一定的催化性能，但活性较低．研究结果表明，孔道大小与苯\r\n分子动态直径相近或孔道稍大的分子筛是催化甲烷芳构化反应的良好载\r\n体，孔道过大或过小都不利于苯和萘等芳烃的生成．     

聚N—异丙基丙烯酰胺溶液的温度依赖关系

用自由基聚合法合成了聚Ｎ－异丙基丙烯酰胺（ＰＮＩＰＡＡＭ）样品，用乌氏粘度计考查了该聚合物的四氢呋喃（ＴＨＦ）溶液和水溶液的粘度与温度的依赖关系。发现ＰＮＩＰＡＡＭ－ＴＨＦ体系的特性粘数随温度升高而增大，ＰＮＩＰＡＡＭ－Ｈ２Ｏ体系的特性粘数－温度曲线表现出较为复杂的变化规律。并用实验确定的特性粘数对合成样品的分子量进行了表征Ｍｎ＝８．４４×１０＾５ｇ·ｍｏｌ＾－１。     

柑桔果皮中多甲氧基黄酮的LC-APCI-MS定性分析

黄酮化合物是具有多种生物活性的物质,广泛存在于自然界中。单纯为甲氧基取代的多甲氧基黄酮PMF是芸香科多种桔类所特有的,特别是在其果皮中有较高的含量。近年来有关桔皮PMF抗癌的研究取得了很大进展。PMF作为桔皮中的抗癌活性成分,对多种癌细胞有较强的抑制作用,受到国内外的广泛关注。由于桔皮中PMF的主要成分随柑桔种类和产地的不同而有较大差异,所以,筛选含有较强抗癌活性的PMF成分的桔皮种类,是一项非常有意义的工作。文献报道的PMF的分析检测方法主要有液相色谱法、气相色谱-质谱法等。本文利用液相色谱-大气压化学电离化质谱联用技术定性分析了3种柑桔果皮中PMF的主要成分,并结合紫外吸收光谱进一步确证。     

聚苯乙烯免疫检测球珠的表层改性及其性能

<正> 随着免疫检测在生物医学研究及临床诊断中的发展和应用,七十年代后期由高聚物制成的乳胶或球珠作为免疫载体亦得到较快的发展;八十年代以来有多种产品问世,其中聚苯乙烯球珠及检测板、盒国外已有专厂生产。 由于聚苯乙烯球珠对免疫体、酶等的固定系物理吸附,在制备及检测过程中,这些蛋     

分散固相萃取结合气相色谱-高分辨质谱快速筛查酱油中多种氯丙醇

建立了酱油中1，3-二氯-2-丙醇、2，3-二氯-1-丙醇、3-氯-1，2-丙二醇和2-氯-1，3-丙二醇的分散固相萃取-气相色谱-高分辨质谱快速筛查检测方法。样品采用乙酸乙酯提取，提取液浓缩后经N-丙基乙二胺净化，气相色谱-高分辨质谱测定，内标法定量。结果表明，该方法对于酱油中4种氯丙醇的定量限为0.5~10 μg/kg。在3个浓度水平下的加标回收率为78%~103%；相对标准偏差均不大于8.8%。该方法快速、简便、准确、灵敏，可作为酱油中4种氯丙醇的有效检测方法。     

Clustering of chemical databases by means of the projection of maximum overlapping sets similarity measurements onto multidimensional spaces

In this paper, we propose a new method for clustering of chemical databases based on the representation of measurements of structural similarity onto multidimensional spaces. The proposed method permits the tuning of the clustering process through the selection of the dimension of the projection space, the normal vectors and the sensibility of the projection process. The structural similarity of each element regarding to the database elements is projected onto the defined spaces generating clusters that represent the characteristics and diversity of the database and whose size and characteristics can be easily adjusted.     

New aspects of the electroadsorption of ethyl xanthate on copper electrodes

The interaction of the ethyl xanthate (EX) anion with a copper electrode in a borate buffer solution, pH 9.2, has been investigated by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), electrochemical impedance spectroscopy (EIS), and measurements of contact angle (CA) under controlled potential. The results obtained allow establishing that, in the potential range from -0.80 and -0.60 V, two parallel reactions were characterized. These reactions were the ethyl xanthate electroadsorption and the hydrogen evolution reaction (HER). This last reaction has not been described by previous authors. Besides, the EIS measurements show that the mechanism of the HER on copper electrodes is not affected by the presence of a ethyl xanthate species. The EQCM study shows that in the electrodesorption process the departure of each ethyl xanthate species from the copper electrode is accompanied with the simultaneous entry of four to five water molecules. This fact is in accordance with the number of copper atoms involved in the adsorption of one ethyl xanthate species.     

Hexaruthenium carbonyl cluster complexes with basal edge-bridged square pyramidal metallic skeleton: efficient synthesis of 2-imidopyridine derivatives and determination of their reactive sites in carbonyl substitution reactions

The reactions of [Ru(3)(CO)(12)] with half equivalent of 2-amino-6-methylpyridine (H(2)ampy) or 2-aminopyridine (H(2)apy) in refluxing xylene give the hexanuclear products [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-L)(mu-CO)(2)(CO)(14)] (L = ampy, 1; apy, 2). These reactions represent the first high-yield syntheses of hexanuclear complexes with a basal edge-bridged square pyramidal metallic skeleton. Five metal atoms of these complexes are bridged by the N-donor ligand in such a way that the edge-bridging metal atom is attached to the pyridine nitrogen, while the basal atoms of the square pyramid are capped by an imido fragment that arises from the activation of both N-H bonds of the NH(2) group. The reactive sites of these complexes in CO substitution reactions have been determined by studying the reactivity of 1 with triphenylphosphine. Two kinetically controlled monosubstitutions take place on the edge-bridging metal atom in positions cis to the pyridine nitrogen, leading to a mixture of two isomers of formula [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(13)(PPh(3))] (3 and 4). On heating at 80 degrees C, these monosubstituted isomers are transformed, via a dissociative pathway, into the product of thermodynamic control (5), which has the PPh(3) ligand on the apical Ru atom. The di- and trisubstituted derivatives [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(12)(PPh(3))(2)] (6) and [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(11)(PPh(3))(3)] (7) are stepwise formed from 3-5 and PPh(3). Compound 6 has the PPh(3) ligands on the edge-bridging and apical Ru atoms, and compound 7 has an additional PPh(3) ligand on an unbridged basal Ru atom. The compound [Ru(6)(mu(3)-H)(2)(mu(5)-eta(2)-ampy)(mu-CO)(2)(CO)(12)(mu-dppm)] (8), in which a basal and the apical Ru atoms are spanned by the dppm ligand, has been isolated from the reaction of 1 with bis(diphenylphosphino)methane.     

Über die Strukturaufklärung von (Hydroxy-oxo-cyclopentenyl)alkansäuren,den Aldolkondensationsprodukten von Dioxoencarbonsäuren aus Rinderleber

Structure Elucidation of (Hydroxy-oxo-cyclopentenyl)alkanoic Acids, the Aldol-Condensation Products of Dioxoene Acids from Cattle Liver During homogenization of cattle liver the highly instable dioxoene acids 13a , 13b , and 13c are formed. These acids cyclize in alkaline solution to yield pairs of stable (hydroxy-oxo-cyclopentenyl)alkanoic acids, which were isolated as methyl esters 4a / 5a , 4b / 5b , and 4c / 5c . The structures of these compounds were deduced from an enriched 3-mg mixture sample by microchemical reactions combined with a GC/MS analysis of the reaction products. Compound 13a was obtained as methyl ester by oxidation of the methyl ester of the corresponding F-acid with NaOCl. It was not possible to isolate 13a in pure form due to its high sensitivity. Instead of the methyl ester of 13a , 4a and 5a were isolated, of which the structures were established.     

WxC-MCM-48催化剂的合成、表征及加氢脱硫催化性能

以正硅酸乙酯(TEOS)为硅源，十六烷基三甲基溴化铵(CTAB)为表面活性剂，仲钨酸铵为钨源，采用水热晶化法一步合成了不同钨含量(以Si、W物质的量比n_Si/n_W表示)的WO₃-MCM-48，然后经甲烷/氢气(V/V=1/4)混和气体程序升温还原碳化(TPC)，制备出了W_xC-MCM-48(x=1、2)催化剂，采用XRD、N₂吸附-脱附和NH₃-TPD对样品的结构进行了表征，用噻吩作为模型化合物，对W_xC-MCM-48催化剂的加氢脱硫催化活性进行了评价。结果表明，在一定钨含量的条件下，WO₃-MCM-48和W_xC-MCM-48样品仍然保持MCM-48的三维立方有序介孔结构，n_Si/n_W=30～15时，碳化钨的物相为W₂C；n_Si/n_W=7.5时，碳化钨为W₂C和WC物相，W_xC-MCM-48催化剂表现出了良好的加氢脱硫催化性能。