固定床吸附柱放大效应考察─—理论板当量高度分析

从色谱塔板理论公式出发，推导出实测理论板公式及理论极当量高度和吸附热力学、吸附动力学参数之间的关系，并对模型的选择、优化操作线速的选取作了讨论。实验测定了ｄ＿ｐ／ｄ＿ｔ＝４．０／２０．０时，吸附柱内的轴向扩散系数及流体传质系数，并加以关联。对不同压力、流量下的理论板当量高度也进行了检验。     

固定床吸附柱放大效应考察─—理论板当量高度分析

从色谱塔板理论公式出发，推导出实测理论板公式及理论极当量高度和吸附热力学、吸附动力学参数之间的关系，并对模型的选择、优化操作线速的选取作了讨论。实验测定了ｄ＿ｐ／ｄ＿ｔ＝４．０／２０．０时，吸附柱内的轴向扩散系数及流体传质系数，并加以关联。对不同压力、流量下的理论板当量高度也进行了检验。     

组合导向浮阀塔板的CFD模拟及反向流分析

精馏塔板上的气液两相流动对传质效率有重要影响。根据实验数据拟合得到平均气含率关联式,将其加入动量源项,采用Fluent软件对1.2 m直径的组合导向浮阀塔板上的气液两相流动进行CFD模拟,考察了塔板上的气液两相流动状况。清液层高度的模拟结果与实验数据关联式相吻合,验证了模拟的正确性。对塔板上液相的非理想流动进行了分析,通过对反向流进行量化和统计计算出反向流体积分数(即反向流体积占塔板总体积的百分比)。3块不同浮阀排布塔板的反向流体积分数时均值的计算结果表明,梯形浮阀和矩形浮阀的排布方式对反向流影响很大,通过合理排布能够使工业塔板的反向流体积分数时均值从22.0%下降到19.4%,降幅达到11.8%。本研究结果可望对塔板的设计和优化提供指导。     

组合导向浮阀塔板的CFD模拟及反向流分析

精馏塔板上的气液两相流动对传质效率有重要影响。根据实验数据拟合得到平均气含率关联式,将其加入动量源项,采用Fluent软件对1.2 m直径的组合导向浮阀塔板上的气液两相流动进行CFD模拟,考察了塔板上的气液两相流动状况。清液层高度的模拟结果与实验数据关联式相吻合,验证了模拟的正确性。对塔板上液相的非理想流动进行了分析,通过对反向流进行量化和统计计算出反向流体积分数(即反向流体积占塔板总体积的百分比)。3块不同浮阀排布塔板的反向流体积分数时均值的计算结果表明,梯形浮阀和矩形浮阀的排布方式对反向流影响很大,通过合理排布能够使工业塔板的反向流体积分数时均值从22.0%下降到19.4%,降幅达到11.8%。本研究结果可望对塔板的设计和优化提供指导。     

电渗强化多孔介质孔内流动及传质

建立了电场中多孔介质孔内流动模型 ,通过计算比较了Poiseuille流和电渗流对孔内流动的贡献 ;提出“有效扩散系数”来定量描述电渗对多孔介质孔内传质过程的强化作用 ;建立了电色谱理论塔板高度模型 ,比较了Poiseuille流和电渗流对色谱理论塔板高度的影响 .计算结果表明采用Poiseuille流强化孔内传质的方法仅适用于孔径大于 5 0 0nm的大孔颗粒 ;而电渗流则可提高不同孔径的介质孔内的传质 ,降低色谱分离理论塔板高度 ;依据Yoshida模型计算了不同的有效扩散系数下的吸附穿透曲线以揭示电场强度对电色谱吸附行为的影响 ,理论预期与实验结果一致     

推荐一个表示体积排斥色谱柱性能的新参数

一、引言目前国内液相色谱法,不管什么分离机理(吸附、分离、离子交换、体积排斥),其色谱柱的性能一般习惯于用理论塔板数(N)、塔板高度(H)、在混合物分离时用柱的分辨率(Rs)等参数表示。这些柱性能参数的表示式为:     

亲水反相C18键合固定相的制备及分离性能

针对常规C18反相色谱柱无法满足在高水相及纯水流动相条件下的液相色谱分析,采用混合键合的方式得到一种新型亲水反相色谱固定相,通过元素分析及红外分析对固定相进行了物理表征;以尿苷为试样、纯水为流动相进行色谱分析,并按照2010版中国药典中对头孢他啶进行分析。结果表明,此种新型固定相在亲水条件下分离度和理论塔板数方面明显优于常规反相色谱柱。     

不同隙径比环形脉冲萃取柱的传质性能

以30%TBP(煤油)-HNO_3-H_2O为实验体系,在外柱内径为100mm的环形脉冲萃取柱中以4种不同隙径比进行了传质性能研究.实验测定了环形柱的稳态浓度剖面,以扩散模型为基础拟合求取了传质模型参数,建立了相应的关联式.研究结果表明,4种不同隙径比环形柱的“真实”传质单元高度H_(ox)值可以用相同关联式表述;分散单元高度H_(oxd)值则与隙径比的0.16次方成正比.与外柱内径为50mm的环形柱相比较,其H_(ox)值可采用相同关联式描述;其H_(oxd)值与环形柱外柱内径有关.这反映了外柱径对环形柱轴向混合的影响.     

旋流塔板上的气流运动

在Φ300 mm塔内,用二维激光多普勒测速仪对A-25塔板上的气流测得不同流量下的三维时均速度场,得到切向、轴向速度与半径的关联式。得知主要气液接触区的气流场可描述为双层旋转流动结构。对流场特点及其对湿板操作的影响进行了讨论。     

杀螟松的反相液相色谱分析

高效液相色谱通常调节流动相的组成和柱温来改变色谱分离情况。本文对于反相键合相液相色谱,详细测定了流动相组成、柱温分别对农药杀螟松及其杂质的容量因子、分离因子、理论塔板数和分离度等全面的影响,并测定了有关的热力学参数,为选择色谱操作条件提供实验根据。一、实验 (一)仪器及实验条件仪器:美国Varian公司生产的VISTA56型液相色谱仪     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.