分散体系形成中表面活性剂使用量的判据

通过对甲苯等有机溶剂/水/表面活性剂体系的水基化分散,利用MalvernMicroplus型激光粒度仪对乳化后的分散相粒子大小及其分布进行研究.结果表明,表面活性剂的使用量对分散结果的影响具有局限性,对于具体体系,表面活性剂的临界胶束浓度[CMC(CMC_O+CMC_W)是这种局限性的量化标志,超出CMC的表面活性剂是多余的,对最终的分散结果无作用,同时也会影响分散体系的稳定性.     

The use of permeation tube device and the development of empirical formula for accurate permeation rate

A series of laboratory experiments were conducted to assess the accuracy of permeation tube (PT) devices using a calibration gas generator system to measure permeation rate (PR) of volatile organic compounds (VOCs). Calibration gas standards of benzene, toluene, and m-xylene (BTX) were produced from PTs at varying flow rates (FR) of 20-1200 mL min(-1) and constant temperature (30°C). Results indicate that changes in flow rate greatly affected the permeation rate of each VOC at this temperature. This paper presents experimental approaches to accurately measure actual permeation rate (APR) and the derivation of empirical equations for predicted permeation rate (PPR). If the magnitude of bias is defined as the difference between PPR and the manufacturer's permeation rate (MPR), the bias was typically 19-40% for toluene (T) and 31-54% for m-xylene (X). Benzene (B) exhibited the least bias of 1.4-18.8%, nevertheless our PPR values for benzene were more reliable at lower flow rates (0.75-1.20%). This study highlights the importance of flow rate and associated pressure changes as a key to accurate permeation rate estimation from permeation tube devices.     

Synthesized high-silica hierarchical porous ZSM-5 and optimization of its reaction conditions in benzene alkylation with methanol

41.4% yield of xylene was obtained over high-silica hierarchical ZSM-5 catalyst by optimizing reaction conditions of benzene alkylation with methanol.     

高稳定性金属有机配位聚合物膜的制备及二甲苯分离性能

以常见的多孔二氧化硅为载体, 采用晶种-二次生长法在溶剂热条件下制备了高稳定性的金属有机配位聚合物膜材料. 通过X射线衍射、 扫描电子显微镜、 单组分气体透过率和二甲苯同分异构体分离等测试手段对材料的结构、 形貌和性质等进行了表征. 二甲苯同分异构体的渗透汽化分离结果表明, 这种多孔膜材料对二甲苯混合物具有选择性吸附分离的性质. 进一步通过热处理、 超声处理和性能的重复表征, 证明了该膜材料具有优良的热稳定性和机械稳定性, 适于实际应用.     

LiFe0.98 Pt0.02 PO4薄膜的光学及气敏性研究

为提高LiFePO_4敏感薄膜元件的灵敏度,以铂(Pt)作为掺杂元素,用水热法一步合成出LiFe_(0.98)Pt_(0.02)PO_4粉末;利用旋涂法将其固定在锡掺杂玻璃光波导表面,制备了LiFe_(0.98)Pt_(0.02)PO_4薄膜/锡掺杂玻璃光波导元件。将敏感薄膜在不同温度下热处理,通过比较各个敏感薄膜元件对苯类挥发性有机气体的响应讨论薄膜处理温度对LiFe_(0.98)Pt_(0.02)PO_4薄膜元件光学特性及气敏性的影响。结果显示,在450℃下处理的薄膜因具有光学透明性好、折射率高、光传播损失小等特点对苯类气体显出较大的响应,能够检测出浓度为1×10~(-7)~1×10~(-3)V/V_0的二甲苯气体。当气体浓度小于1×10~(-6)V/V_0时,其他苯类气体不会对二甲苯的检测产生影响。     

Fast Analytical Temperature Rising Elution Fractionation (TREF) of Polypropylenes

Analytical temperature rising elution fractionation (TREF) is a complementary technique of gel permeation chromatography (GPC) for the analysis of polyolefin structure. By connecting a high-temperature GPC with a gas chromatograph (GC) oven it is possible to build a fast analytical TREF, which permits a dramatic reduction in analysis time by directly injecting the polymer solution onto the cold column, as compared with the traditional TREF in which the slow cooling step usually takes more than 40 h. The method was successfully applied on six commercial random and homo polypropylenes for which similar thermograms were obtained for fast- and slow-cooling TREF. The obtained results show subtle differences in the behavior of polypropylene melting in solution as compared with previously analyzed polyethylene. The most important is the difference of 12.6°C between the melting temperatures in the presence of trichlorobenzene and xylene, which is much higher for polypropylene than the 3.7°C measured for polyethylene.     

多级孔ZSM-5分子筛: 丰富的外表面酸中心和良好的二甲苯异构化催化性能

多级孔沸石分子筛的结构性质及其催化性能是近年来分子筛研究的热点.本文采用蒸汽辅助晶化的方法制备了多级孔ZSM-5沸石分子筛,采用NH₃程序升温脱附和原位吸附红外光谱等方法研究了其表面酸性质,用邻二甲苯异构化反应考察了其催化性能.结果表明,多级孔结构分子筛的结晶度和总酸量有所下降,但Lewis酸中心却有所增加.进一步研究发现,多级孔结构分子筛的外表面酸中心数量远高于常规分子筛,从而证实了多级孔结构可以将更多的酸中心暴露到外表面;而外表面酸中心数量的增多和扩散传质的改善是多级孔ZSM-5分子筛在邻二甲苯异构化反应中具有更高催化活性和对二甲苯产率的重要原因.     

二甲苯、卤代苯在硝酸银溶液中的溶解平衡

具有C＝C双键的许多有机化合物可与银离子形成络合物。L.J.Andrews和R.M.Kcefcr等用在含Ag⁺的芳烃溶液中测定溶解度的方法,计算了某些芳烃与Ag⁺络合物的形成常数^[1]。     

MFI型分子筛膜的两段变温合成及对二甲苯异构体的分离性能

分别采用恒温和变温两种方法在氧化铝支撑体上原位制备了MFI型分子筛膜. 恒温法合成的MFI型分子筛膜晶体颗粒较大, 在高温脱除模板剂时会形成较大的缺陷, 没有对二甲苯/邻二甲苯(PX/OX)分离性能. 变温法合成的MFI型分子筛膜晶体在a, b方向尺寸较小, 在高温脱除模板时不会形成较大缺陷, 对PX/OX有良好的分离性能, 在300 ℃下, PX/OX分离因子高达42, PX的渗透性为9.57×10^-9 mol·m^-2·s^-1·Pa^-1. 采用低温臭氧脱除模板剂能够有效减小分子筛晶体热收缩产生的应力, 提高MFI型分子筛膜的分离性能. 两种方法合成的分子筛膜在低温臭氧的条件下脱除模板剂后, 都具有PX/OX分离性能, 其中变温法合成的分子筛膜PX/OX分离因子高达76, PX的渗透性为1.02×10^-8 mol·m^-2·s^-1·Pa^-1.     

Compounds N,N′-bis(9-cyclohexyl-9-xanthenyl)ethylenediamine and its thio derivative,N,N′-bis(9-cyclohexyl-9-thioxanthenyl)ethylenediamine,as potential hosts in the presence of xylenes and ethylbenzene: Conformational analyses and molecular modelling considerations

Two novel crystalline compounds, N,N′-bis(9-cyclohexyl-9-xanthenyl)ethylenediamine (OED) and its thio derivative, N,N′-bis(9-cyclohexyl-9-thioxanthenyl)ethylenediamine (SED), were designed and synthesized in our laboratories, and assessed for their potential as host compounds for the four C8 aromatic compounds, namely o-, m- and p-xylene (o-Xy, m-Xy, p-Xy), and ethylbenzene (EB). Despite the only difference between the two compounds being the heteroatoms in their B rings, immense behaviour differences were noted: only OED displayed host behaviour in these conditions, clathrating all but m-Xy, while SED failed to form complexes with any of the four organic solvents. These observations prompted an investigation into the conformations of OED and SED through single crystal diffraction (SCXRD) analyses as well as computational studies with surprising results. SCXRD was also employed to analyse the three complexes that successfully formed with OED, and thermal analyses (TA) assisted in understanding the selectivity behaviour of OED when presented with mixed guests.