氯化铝高效催化合成1-(N-氨甲酸酯基)烷基-2-萘酚

无溶剂条件下,氯化铝可有效催化2-萘酚、醛和氨基甲酸酯三组分"一锅法"合成1-(N-氨甲酸酯基)烷基-2-萘酚。确定了较佳反应条件,产品经熔点、IR、1H NMR、元素分析进行表征。提出了可能的催化作用机理。     

三臂PPO-PDLA-PLLA 嵌段共聚物的制备与结构及其立构复合体的结晶行为

以环氧丙烷聚醚三元醇(PPO)为起始剂, 开环聚合D 型丙交酯(DLA), 合成三臂环氧丙烷聚醚三元醇-聚右旋乳酸(PPO-PDLA)嵌段预聚体. 采用端基活化技术对预聚体进行端羟基活化, 再与L 型丙交酯(LLA)进行逐步开环聚合,合成了不同分子量的三臂环氧丙烷聚醚三元醇-聚右旋乳酸-聚左旋乳酸(PPO-PDLA-PLLA)嵌段共聚物. 采用红外(FTIR)、核磁(NMR)和凝胶渗透色谱(GPC)等对三臂PPO-PDLA-PLLA 嵌段共聚物的测试表明, 合成的嵌段共聚物分子链具有很高的立构规整度; 通过调节LLA 单体与PPO-PDLA 预聚体的投料比, 不仅可控制产物的分子序列结构, 而且样品的数均分子量可大于100 kDa. 差示扫描量热仪(DSC)和广角X 射线衍射(WAXD)结果显示, 三臂PPO-PDLAPLLA嵌段共聚物的异构体链段分子间生成立构复合晶体, 其熔点约为200 ℃, 且没有PLLA 均聚物链段结晶现象. 实验结果表明, 这是一类具有实际应用价值的新型耐热聚乳酸(PLA)材料.     

GC—MS-相转移衍生化法分析水相中亚硝酸根离子

采用相转移催化剂四辛基溴化铵及五氟苄基溴将水相(血、尿)中亚硝酸根离子衍生化生成可挥发性化合物,然后用GC-MS法进行测定.亚硝酸根离子含量在0.2～10 μg/ mL范围内与离子峰面积呈良好的线性关系,相关系数r=0.9998,检出限为0.1 μg / mL.用该方法对水、尿、血中亚硝酸根离子进行测定,测定结果的相对标准偏差为1.44%～4.17%(n=6),回收率为82%～84%.     

高分子量立构复合结晶的三枝化PPO-PDLA-PLLA嵌段共聚物

以三枝化低不饱和度聚环氧丙烷(PPO)引发D-丙交酯(D-LA)逐步开环聚合, 合成了三枝化聚环氧丙烷-聚右旋乳酸(PPO-PDLA)共聚物. 用辛酸亚锡Sn(Oct)₂与PPO-PDLA端羟基反应进行Sn(Oct)封端, 制备了三枝化PPO-PDLA-Sn(Oct)预聚物. 再于130 ℃下, 以其作为大分子引发剂与L-丙交酯(L-LA)开环聚合, 合成了分子量>10⁵的三枝化PPO-PDLA-PLLA嵌段共聚物. 活性端基的引入, 降低了聚合反应温度, 从而降低了聚合中的酯交换或热降解反应发生的概率. 实现了高分子量PPO-PDLA-PLLA嵌段共聚物的合成. 结构测试结果表明, 合成的嵌段共聚物具有分子结构易控及立构规整度高等特点. 在结晶-熔融-再结晶重复热处理下, 三枝化PPO-PDLA-PLLA嵌段共聚物仅发生立构复合聚乳酸结晶, 且结晶能力稳定.     

SURFACE ACIDITY OF ZEOLITE ZSM-5 AND ITS CATALYTIC PROPERTIES IN ESTERIFICATION OF ACETIC ACID WITH ALCOHOLS

IntroductionTheuseoflarge-PorezeolitessuchasXandYforcarelyzingtheesterificationhasbeenearlysuggestedbyBergklllandnorelationshipbetweentheactivityandsubdueaciditywasobserved.ItalianPatent[2]reportedthatdecationizedYzeolitesareveryactiveandselectivecatalyst…     

STUDIES ON THE ISOMORPHOUS SUBSTITUTION OFFe(III) AND Cr(III) IN MCM-41 MOLECULAR SIEVES

IntroductionRecently.therehasbeengreatillterestinthediscoveryofthemesoporouscrystallinematerialMCM-4ill,2].MCM-41isthecollectivenameforafamilyofsolidswithporesizebetween16and100A,whichpossessesahexagonalarrayofuniformmesopores.Ithasbeenfoundthatmetalatoms…     

中孔分子筛MCM-41形成机理的考察

MCM－41分子筛是九十年代初期美国Mobil公司开发的一种新型中孔（mesoporous）材料[1]．它以C8－C16季俊碱表面活性剂作为模板剂水热法合成，具有2－10nm的孔径，孔道六方有序排列，高比表面和高吸附容量，中等酸性和稳定性，是一种有潜在应用前景的吸附和催化材料．目前，关于     

离子交换固相萃取-超高效液相色谱-串联质谱法同时测定水产品中泰妙菌素和沃尼妙林残留量

建立了一种强阳离子固相萃取结合超高效液相色谱-串联质谱法同时测定水产品中泰妙菌素和沃尼妙林残留量的分析方法。样品经乙腈提取和Oasis MCX 固相萃取柱净化后,以乙腈-0.05 %甲酸5 mmoL·L^-1乙酸铵水溶液为流动相,经Waters ACQUITY UPLC BEH C₁₈色谱柱梯度洗脱分离,在电喷雾正离子多反应监测模式下,用内标法分析泰妙菌素,用外标法分析沃尼妙林。结果显示,泰妙菌素和沃尼妙林在0.1～10.0 ng·mL^-1内具有良好的线性关系,相关系数r均大于0.999 9,检出限和定量限分别为0.03 和0.1 μg·kg^-1。在0.1,1.0,5.0和10.0 μg·kg^-1 4种添加水平下,加标回收率在87 %～114 %,相对标准偏差在0.87 %～6.50 %。对50条鲫鱼进行实际样品验证,发现在鲫鱼的各个组织中均有泰妙菌素和沃尼妙林残留,其中肾脏残留总量最高,为453.81 μg·kg^-1,肝脏次之,为236.97 μg·kg^-1。结果表明,所建方法能够满足对水产品中泰妙菌素和沃尼妙林残留量的分析要求。     

Impact of mixed low-molecular-weight organic acids on uranium accumulation and distribution in a variant of mustard (Brassica juncea var. tumida)

The impact of a mixture of low-molecular-weight organic acids (LMWOAs) composed of CA/MA/OA/LA with a molar ratio of 2.5:2.31:1.15:0.044 on uranium (U) accumulation and distribution in mustard (Brassica juncea var. tumida) was studied in this paper in order to understand the mechanism of rhizosphere-exudation assisted phytoremediation by hydroponic and pot culture experiments. The impact of the mixture of LWMOAs (Mix) on U accumulation showed that in hydroponic conditions Mix could enhance U translocation from root-to-shoot in mustard, but inhibit U uptake in root. In pot experiments, Mix enhanced both root and shoot U accumulation in mustard. The time-dependent kinetics of U uptake in mustard on Mix treatment showed that U content in plant shoots and roots increased with time increasing, and the steady state conditions were obtained at the 8th and 5th day with the U content of 1,528 and 2,300 mg/kg, respectively. Transmission electron microscope and energy dispersive X-ray spectrometry analysis for mustard roots showed that U was mainly observed on cell membrane of mustard roots on Mix treatment. This study would provide new insights for the mixture of LWMOAs-assisted phytoremediation of U-contaminated soil.     

Thermal broadband tunable Terahertz metamaterials

A thermally tunable metamaterial comprising a periodic array of metallic split-ring resonators with an embedded semiconductor has been proposed. The resonance frequencies of the metamaterial are demonstrated to be continuously tuned in the terahertz regime by increasing the temperature. The tunability is attributed to the temperature-dependent permittivity of the embedded semiconductor and well analyzed by an equivalent capacitor-inductor model. The proposed designs ensure broadband thermally tunable terahertz devices.