有机硅单体分离流程的模拟与优化

有机硅单体是一种多组分混合物,其组分沸点相近,产品纯度要求高,因此其分离纯化相当困难。目前工业上主要有5种有机硅单体分离系统的工艺流程,文中采用流程模拟软件对5种工艺流程进行严格模拟计算,将模拟结果带入相关的费用计算模型,计算不同工艺流程的设备费用与操作费用,并计算比较各工艺流程的年度总费用(TAC)。中切流程在5种工艺流程中的年度总费用最低。以中切流程为初始序列,利用调优法进行调优并找出4组相邻分离序列。采用流程模拟软件对4组分离序列进行精确模拟计算,计算并比较4组序列的年度总费用。结果表明:调优序列3的年度总费用最低,较初始中切流程总费用降低了1.74%,因此选定调优序列3为分离有机硅单体的最优序列。     

双效精馏分离一甲基三氯硅烷-二甲基二氯硅烷体系的模拟计算

应用Aspen Plus软件模拟计算一甲基三氯硅烷和二甲基二氯硅烷体系分离过程,考察了单塔精馏和三种双效精馏流程。在相同进料条件下,对比了不同流程的能耗与年度总费用。结果显示,对于所研究的一甲基三氯硅烷和二甲基二氯硅烷体系,双效并流流程是最佳精馏流程,年度总费用比单塔精馏降低了40.08%。     

苯系有机硅单体精馏塔系与换热网络的模拟优化

根据直接法合成苯基氯硅烷粗单体的特点,在原有分离序列的基础上,采用易分离度系数法,设计出了新的苯基氯硅烷粗单体分离序列,采用Aspen Plus模拟软件,选择NRTL物性方法,应用系统中的DSTWU及Rad Frac精馏模块对流程进行模拟优化,通过灵敏度分析,得到该新流程最优的工艺操作条件。对其精馏塔塔顶、塔釜物流进行夹点分析,利用Aspen Energy Analyzer进行了换热网络的设计,公用工程节能45.9%,为实际生产中的节能改造提供了理论依据。     

苯基氯硅烷色谱固定相的优选及分析

本文以一般实验室常见的七种色谱固定相对苯基氯硅烷单体进行了优选。一苯基三氯硅烷与其杂质容易分离。二苯基二氯硅烷与其杂质以0V—25、OV—1和E_(301)作固定相分离较好。以E_(301)为最佳。本文提出以E_(301)为色谱固定相,以3米和1米柱分别进行一苯基三氯硅烷和二苯基二氯硅烷的定量测定,最佳温度分别为1.30℃和190℃左右。文中介绍了主要组份相对重量校正因子的测定。由于使用温度较低,柱效可长期保持最佳状态。本方法的绝对偏差小于1%,相对标准偏差小于2%。     

考虑生产排序的间歇过程换热网络综合与优化

间歇过程换热网络综合是化工系统工程研究的重要部分,设计时需要考虑时间、设备、生产排序等多方面因素,具有一定的复杂性。本文围绕多批次间歇过程的直接换热问题,考虑生产排序的影响,采用覆盖操作和非覆盖操作,通过调整批间隔增加流股直接换热的可能性,减少设备闲置,得到3种不同的生产方案;针对每一个生产方案,采用启发式方法综合得到初始换热网络,并对该网络进行结构调优,提出渐进调优规则,在公用工程费用和设备费用间作权衡,减少换热器个数和流股分流,得到年度总费用最低且换热设备个数较少的换热网络,使其更符合实际应用;将3种生产方案对比,可以发现生产排序对换热网络的影响。最后将所提方法应用于实际算例,验证所提方法的可行性。     

双效热泵精馏分离乙醇-异丙醇近沸体系的模拟研究

以乙醇-异丙醇体系为研究对象,分别采用常规精馏、双效精馏、双效热泵精馏进行分离,使用Aspen Plus流程模拟软件进行模拟计算,以年总费用最低为目标函数,得到了相关的工艺参数,结果表明,双效热泵精馏的年综合费用比双效精馏节约了59.5%,比常规精馏节约了77.5%。     

从废酯液中回收醋酸乙酯的分离技术

介绍了以废酯液为原料分离生产醋酸乙酯的工艺过程。利用废酯液中各组分在水中溶解特性的不同,水洗沉降对酸性物质与酯进行初步分离。依据精馏理论,确定分离初始方案。选择合适的热力学方程,利用模拟软件模拟分离过程;根据总费用最小,优化操作条件和塔设备参数,确定最优分离条件。模拟计算结果表明:采用2个塔流程可有效分离生产出合格品醋酸乙酯,年收益达500.1万元。     

三种萃取精馏法生产1,3-丁二烯的经济评价

利用化工流程模拟软件Aspen Plus对国内常用的ACN法、DMF法、NMP法三种1,3-丁二烯萃取精馏工艺进行了全流程模拟优化和热集成分析。模拟结果表明,三种工艺的1,3-丁二烯产品质量均满足设计要求,且相关参数与实际生产操作数据吻合较好。在此基础上,以年度总费用(TAC)最小为目标函数,利用最新经济数据评价了三种工艺的经济技术水平。结果表明,三种工艺的年度总费用以NMP法最低,DMF法最高,NMP法具有明显的经济优势。     

甲醇和三甲氧基硅烷共沸物分离过程模拟和优化

三甲氧基硅烷（trimethoxysilane）是合成功能性有机硅化合物的重要中间体。在以甲醇和硅为原料合成三甲氧基硅烷的工业化生产过程中,过量的甲醇和产物三甲氧基硅烷会形成最高共沸物。本文探究了变压精馏、萃取精馏和隔壁塔萃取精馏三种分离提纯甲醇和三甲氧基硅烷的工艺,以最小年度总费用（TAC）为目标函数,运用混合整数非线性规划（MINLP）对三种流程进行了优化,比较了三种流程的效率和二氧化碳排放量。结果表明,与变压精馏相比,通过隔壁塔萃取精馏分离甲醇与三甲氧基硅烷共沸物具有明显的优势。分离100kmol/h甲醇（摩尔分数50.00%）和三甲氧基硅烷的TAC从198.84万美元/年降低到98.93万美元/年,降幅高达50.25%,效率从8.17%提高到13.82%,二氧化碳排放量从1217.53kg/h减少到684.22kg/h,减少了43.80%。     

C3选择性加氢热耦合催化精馏流程模拟

针对C₃ 选择性加氢过程中冷剂费用过高问题提出将选择性加氢催化反应器设置在脱乙烷精馏塔的提馏段,并通过原流程的3 个精馏塔的不同热耦合方式所构成的3 种热耦合催化精馏结构;对三热耦合催化精馏结构分别进行严格模拟和评价,表明通过分离和加氢反应的结合增加了加氢反应的转化率,并通过热耦合降低了分离能耗,年度总费用降低显著。模拟结果表明,3 种方案的年度总费用节约效果分别为4.107%、6.420%和10.337%。     

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.     

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.     

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.     

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.