碳桥限制构型催化剂催化乙烯1-己烯共聚和共聚物结构表征

为了碳桥限制构型催化剂(CpCN-CGC)的工业应用,为模试提供工艺参数,我们考察了用这种催化剂,以正庚烷为溶剂,甲基铝氧烷(MAO)为助催化剂的乙烯与1-己烯共聚,考察因素包括聚合温度、乙烯压力、铝锆比、氢气压力和1-己烯浓度.研究发现聚合温度从100升高到140℃,共聚活性先升高再降低,聚合物分子量持续降低;氢气分压从0.1增加到0.8 MPa,共聚活性仍呈先升高再降低,聚合物分子量持续降低的趋势;乙烯压力从0.4升高到1.8 MPa,共聚活性先升高再降低,但聚合物分子量逐步增大;Al/Zr从500升高到1 000,共聚活性逐步增大,但聚合物分子量趋向减小.优化工艺条件为:催化剂用量为10μmol,Al/Zr=700,聚合温度为110~120℃,乙烯压力为1.2~1.4 MPa,1-己烯加入量为20 mL,聚合时间为30 min.此时共聚活性最高达到106g/(mol-Zr·h),共聚物中1-己烯插入率达到了8.34%;用13C-NMR、GPC、DSC表征了聚合产物,计算了二单元组和三段组序列分布,并发现有交替共聚片段HEHE存在.最后还讨论了在聚合物中发现的多种支链的形成机理.     

“受阻Lewis酸碱对”化学的研究进展

受阻Lewis酸碱对(Frustrated Lewis Pairs,FLPs)是一类具有特殊反应活性的Lewis酸碱对。自发现以来,FLPs受到了广泛关注并在许多领域崭露头角。本文对FLPs在不对称氢化、高分子聚合、CO_2催化还原等应用领域取得的突破进行了介绍;同时对过渡金属FLPs和FLPs配位的过渡金属催化体系进行了综述;最后对FLPs领域未来的发展前景进行了展望。     

凝胶渗透色谱和气相色谱-质谱法测定动物食品中27种有机氯和15种拟除虫菊酯类农药残留量

有机氯农药虽已被世界各国禁止使用,但由于其化学性质稳定和难以降解,在环境中仍然存在有机氯农药残留,并通过食物链的富集作用,造成对食物的污染.     

2010 Pittcon会议(Ⅲ)

电分析化学学会组织的特邀报告(电化学与材料)组有:(1)A Bralter-Toth等,微电极的傅里叶转换伏安法——原理与应用;(2)N Kim,单壁碳纳米管的扫描电化学显微术;(3)P J Kalesza等,高效率生物电催化集成系统的研发与特性鉴定;(4)B J Marguis等,暴露在可变物理性能的贵金属纳米材料下,进行塔电池的改变的衰减功函数的电化学分析;(5)A Karomerich等,可能应用于神经刺激与传感的、导电聚合物改性的电极;(6)Y SSingh等,活体伏安法的长期稳定性与准确性的因素——碳纤维微电极涂层;(7)J G Roberts等,碳纤维微电极电化学预处理引起的表面改变的研究;(8)A Polpke等,碳纳米管阵列的提高功能化的处理。     

超高效液相色谱-串联质谱法测定食品中9种抗凝血灭鼠剂的残留量

食品样品用乙腈提取,经弗洛里小柱净化后,用超高效液相色谱-串联质谱法测定其中9种抗凝血灭鼠剂的含量。色谱分离用甲醇和10mmol.L-1乙酸铵溶液以不同体积比混合为流动相梯度洗脱,采用负离子模式电喷雾离子源在多反应监测模式下进行检测。噻鼠酮的检出限(3S/N)为0.38μg.kg-1,其余8种灭鼠剂的检出限(3S/N)均为0.08μg.kg-1。以空白食品样品为基体,加入3种浓度水平的灭鼠剂标准做回收试验,测得回收率在55.3%～118.1%之间,相对标准偏差(n=6)在2.2%～14.8%之间。     

3β-羟基-16α,17α,21－三甲基孕甾-5-烯-20-酮的合成

皮质激素;;甲基化;共轭加成;瑞美松龙;3β-羟基-16α;17α;21－三甲基孕甾-5-烯-20-酮的合成     

Dynamic properties of soy globulin adsorbed films at the air-water interface

In this paper we present surface dilatational properties of soy globulins (beta-conglycinin, glycinin, and reduced glycinin with 10 mM of dithiothreitol (DTT)) adsorbed onto the air-water interface, as a function of adsorption time. The experiments were performed at constant temperature (20 degrees C), pH (8.0), and ionic strength (0.05 M). The surface rheological parameters were measured as a function of protein concentration (ranging from 1 to 1x10(-3)% wt/wt). We found that the surface dilatational modulus, E, increases, and the phase angle, phi, decreases with time, theta, which may be associated with protein adsorption. These phenomena have been related to protein adsorption, unfolding, and/or protein-protein interactions (at long-term adsorption) as a function of protein concentration in solution. From a rheological point of view, the surface viscoelastic characteristics of soy globulin films adsorbed at the air-water interface are practically elastic. The main conclusion is that the dilatational properties of the adsorbed films depend on the molecular structure of the protein.     

非负载镍催化剂的2-乙基蒽醌加氢活性及其氢吸脱附性质

 分别制备了金属镍粉、兰尼镍、Ni-B非晶态合金及镧掺杂的Ni-B非晶态合金(Ni-B-La)催化剂,研究了催化剂的氢吸附和脱附性质以及对2-乙基蒽醌加氢反应的催化性能. 结果表明,金属镍粉、兰尼镍和Ni-B催化剂表面均具有两种氢吸附位: 弱吸附位和强吸附位. Ni-B-La催化剂表面只有氢的强吸附位,其强吸附氢量与兰尼镍相当. 推测只有氢的强吸附位是2-乙基蒽醌加氢反应的活性中心,并且Ni-B-La催化剂上的强吸附氢较兰尼镍上的更活泼,因而Ni-B-La非晶态合金催化剂对加氢反应的催化活性高于兰尼镍.     

分子信标用于不对称PCR检测乙型肝炎病毒

为了缓解竞争杂交对分子信标检测的影响，将分子信标与不对称聚合酶链式反应(PCR)联用进行血清中乙型肝炎病毒(HBV)的检测。并采用更为直接的荧光方法，将不对称PCR扩增中的引物浓度比确定为5：1，该结果与电泳方法得到的结果有所不同。文中结合对称及不对称PCR过程中荧光强度的变化情况，对其原因进行了详细的探讨。分子信标与不对称PCR联用，可以专一地检测出血清中HBV的存在，与分子信标／对称PCR相比．其检测效果明显增强。     

碳包覆LiFePO4的一步固相法制备及高温电化学性能

Carbon coated LiFePO₄ cathode material was synthesized by one-step solid-state reaction and characterized by X-ray diffraction (XRD), field-emission-scanning electron microscope (FESEM). Electrochemical performances of the material as cathode in lithium-ion battery were investigated at medium and elevated temperature (30 and 55 ℃) by galvanostatic charge-discharge and A.C. impedance tests. The results show that carbon coated LiFePO₄ powder exhibits a well-crystallized olivine structure and spherical morphology with an average particle size of about 500 nm. Galvanostatic charge-discharge tests show that the reversible discharge capacity at 1 C and 1.5 C rates was improved from 121 and 105 mAh·g^-1 at 30 ℃ to 136 and 123 mAh·g^-1 at 55℃, respectively, while the enhancement of high temperature on electrochemical performance is less obvious at a rate lower than 0.5 C. Impedance spectra analyses indicate that the cathode material has a remarkably higher lithium-ion diffusivity at 55 ℃ than that at 30 ℃, which improves the electrochemical performance at high temperature.