具有最低共沸点难分离物系变压精馏分离

变压精馏是根据物系压力改变引起液体混合物共沸点组成变化,进而使共沸物系得以分离的一种有效分离方法。具有最低共沸点的液体混合物分离是化工过程中常见的分离难题。本文在热力学分析基础上研究了四氢呋喃与乙醇、环己烷与苯混合物这类典型的最低共沸液体混合物的变压精馏可行性,提出变压精馏分离四氢呋喃-乙醇液体混合物工艺流程,以NRTL-RK为物性计算方法,利用Aspen Plus模拟软件对变压精馏分离工艺过程进行分析及模拟,并对工艺参数进行优化。结果表明:在常压塔和8atm高压塔组成的双塔流程中变压精馏能将四氢呋喃-乙醇最低共沸混合物进行较好的分离,指出本文提出的研究方法可为具有最低共沸点液体混合物分离工艺的建立提供更加有效的指导。     

热集成变压精馏分离乙醇-乙腈混合物

以乙醇-乙腈混合物为对象,研究了该体系在实验压力范围内的共沸组成,分析了采用变压精馏工艺分离精制乙醇和乙腈的可行性。通过比较实验压力范围内（101~500 kPa）体系的共沸组成与Aspen Plus模拟软件中计算的体系共沸组成,选择了适合的物性方法。在实验装置上进行了变压精馏法分离精制乙醇、乙腈混合物的实验,重点考察了不同回流比对分离效果的影响,得到了质量分数大于99.5%的乙醇和乙腈产品。 应用Aspen Plus模拟软件对乙醇-乙腈体系的热集成变压精馏过程进行了模拟计算,对比了热集成变压精馏与传统变压精馏的能耗,发现热集成变压精馏节能达35%。     

变压精馏分离异丙醇-二异丙醚工艺模拟

在分析异丙醇-二异丙醚二元物系性质的基础上,提出了,采用变压精馏分离该二元混合物系的工艺。利用ASPENPLUS模拟软件．选择NRTL物性模型对该物系的分离工艺进行模拟与参数优化,得到了分离该二元物系的最佳工艺参数。研究表明,采用变压精馏的工艺完全能够达到分离该共沸物的要求,变压精馏是分离提纯该二元共沸物的一种可行方法...     

变压精馏和萃取精馏分离四氢呋喃-水模拟及节能

基于四氢呋喃/水共沸体系的特性,研究了变压精馏和萃取精馏2种工艺分离四氢呋喃和水的方法,进一步考察了2种工艺的可行性及节能情况。物性计算方法采用NRTL活度系数方程,其二元相互作用参数通过汽液相平衡实验数据回归获得,采用Aspen Plus对上述2种工艺进行模拟及优化,获得了2种工艺较优的工艺参数,并对比能耗。结果表明:采用双塔热集成变压精馏工艺或双塔萃取精馏工艺均可有效地分离四氢呋喃-水二元共沸体系,四氢呋喃产品符合《GB/T 24772—2009工业用四氢呋喃》优等品规格,但热集成变压精馏工艺更为节能,节省循环水11. 0%、节省蒸汽20. 3%,且不引入第三组分,更适合四氢呋喃-水体系的分离,为该共沸体系分离的设计与节能提供依据。     

乙醇-乙腈共沸物系分离方法的研究

本文应用化工过程模拟软件Aspen Plus对乙醇-乙腈共沸物系的物性方法和分离方法的选择进行了研究。根据误差分析筛选出最优的热力学模型。通过相对挥发度数据和不同压力下共沸组成的分析,论证萃取精馏和变压精馏的可行性。     

萃取精馏分离丙酮-四氢呋喃的研究

为了分离丙酮-四氢呋喃共沸混合物,研究了萃取精馏在丙酮-四氢呋喃物系中的应用。通过溶剂选择原理初选出乙苯作为萃取精馏分离此共沸物系的溶剂,同时采用NRTL模型对常压下丙酮-四氢呋喃物系和加入溶剂乙苯后的汽液平衡进行模拟和实验验证,模拟结果与实验数据吻合较好。然后进行了间歇萃取精馏分离此共沸物的实验研究来进一步考察所选萃取剂的效果。结果表明:乙苯能够消除丙酮-四氢呋喃共沸物系的共沸点,采用有40块理论板的填料塔,回流比为5,溶剂摩尔比为2.5∶1时塔顶可以得到质量分数为99.34%的丙酮产品,说明采用乙苯作萃取剂分离丙酮-四氢呋喃共沸物是可行的。最后又对连续和间歇萃取精馏分离丙酮-四氢呋喃共沸物的流程进行了模拟,得到的工艺参数将为进一步的工业应用提供了理论依据。     

热集成变压精馏分离甲苯-异丙醇的模拟

甲苯-异丙醇混合物的共沸组成对压力较为敏感,为此提出了热集成变压精馏工艺分离该共沸物.利用ASPEN PLUS化工模拟软件,以修正的WILSON活度系数方程作为物性计算模型,以甲苯和异丙醇的纯度作为约束变量,以分离过程能耗最低为目标函数,对主要工艺参数进行了模拟优化,得到了热集成变压精馏分离甲苯-异丙醇体系的最佳工艺操...     

变压精馏乙醇苯混合物分离工艺模拟计算

乙醇苯混合物是一种二元最低共沸液体混合物。研究了变压精馏分离乙醇苯工艺流程,以W ilson活度系数方程作为物性计算方法,使用过程模拟软件Aspen P lus对整个分离流程进行模拟计算,以系统能耗最低为目标,对重要的工艺参数进行了优化,提出的工艺方案可为工艺装置设计提供理论参考。     

乙二醇萃取精馏分离乙醇-四氢呋喃的最优工艺

对乙二醇萃取精馏分离乙醇-四氢呋喃共沸体系的工艺基于年度总费用最小进行了优化设计。采用设计规定与序贯迭代优化程序考察了双塔萃取精馏工艺与三塔萃取精馏工艺的经济性。结果表明,最优方案与原料组成有关,当四氢呋喃摩尔分数小于37%时,采用三塔萃取精馏工艺最优;当四氢呋喃摩尔分数大于37%时,采用双塔萃取精馏工艺最优。     

基于剩余曲线分析和变压精馏分离氯仿-乙腈-乙醇三元体系

利用剩余曲线初步分析氯仿、乙腈和乙醇三元混合物的分离过程。在分离过程中,选择氯仿作为初步分离的共沸剂,根据剩余曲线分析计算得到额外加入氯仿与原料液的最佳质量比为0.64,在此条件下混合物的初步分离过程中,塔顶产物为氯仿-乙醇共沸物,塔底产物为乙腈。再利用变压精馏分离氯仿和乙醇共沸物,高压塔和低压塔压强分别为600 kPa和101.325 k Pa。最后利用Aspen Plus对工艺进行模拟和优化,得到最佳操作条件。结果表明,氯仿、乙腈和乙醇的质量含量均大于99%,符合设计要求。     

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.     

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.     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.