蒸汽渗透法脱除丙烯中微量水分的研究

采用涂敷法制备了CS/PS,PVA/PS,PVA-CS/PS中空纤维复合膜并用于气相丙烯中微量水分的脱除.研究了PS基膜、原料气湿含量、流速及吹扫气流速等因素对蒸汽渗透分离性能的影响.结果表明,这些复合膜均具有良好的分离性能,其中CS-PVA/PS中空纤维复合膜具有最优的蒸汽渗透性能.     

CS/PVA-GA渗透蒸发膜分离偏二甲肼/水体系的实验研究

将壳聚糖(CS)和聚乙烯醇(PVA)按一定比例共混,再以戊二醛(GA)交联,制备CS/PVA-GA共混交联膜,研究了共混交联膜的结构、力学性能以及在偏二甲肼/水体系中的渗透蒸发脱水性能。结果表明,CS与PVA共混、GA交联,形成了致密的空间网状结构,随PVA含量增加,膜的抗张强度降低,而断裂伸长率增加。料液浓度、温度、膜厚度等因素对膜的渗透蒸发性能有较大影响,当料液中偏二甲肼的质量分数为50%,温度为20℃,渗透侧压力为100 Pa,膜厚约为25μm时,CS/PVA-GA共混交联膜的分离因子达到243,渗透通量可达167 g/(m2.h)。     

微孔γ－Al2O3膜的蒸汽吸附特性

引　言蒸汽渗透 (ｖａｐｏｒｐｅｒｍｅａｔｉｏｎ)是膜分离混合蒸汽的有效技术之一 ,它采用气相进料 ,过程中的浓差极化现象较弱 ,并且在分离过程中不需提供额外的热量以维持被分离物流的温度 ,避免了渗透蒸发(ｐｅｒｖａｐｏｒａｔｉｏｎ)过程设备复杂的缺陷 .这使得蒸汽渗透过程可以很便利地与传统的蒸馏过程相耦联 .因而 ,利用蒸汽渗透膜技术分离有机溶剂 /水混合蒸汽的研究日益受到关注 .文献 [1,2 ]报道了γ -Ａｌ2 Ｏ3膜能有效地分离醇 /水、酮 /水混合蒸汽 .膜对有机蒸汽的吸附性能与蒸汽渗透的分离效果密切相关 ,同时也是膜传质机…     

改性壳聚糖渗透蒸发膜用于酯化反应过程强化

壳聚糖(chitosan, CS)作为渗透蒸发膜材料来源广泛、亲水性好,但结构致密、渗透性较低。为改善CS膜的分离性能,将CS与聚醚-聚酰胺嵌段共聚物Pebax 1657共混,涂覆在NaOH水解处理的聚丙烯腈(polyacrylonitrile,PAN)超滤膜表面制备复合膜,用于渗透蒸发醇水分离过程,并进一步用渗透蒸发方法对乳酸-乙醇酯化反应进行强化。Pebax的聚酰胺与聚醚链段分别发挥调节膜结构与促进水跨膜传递的作用,有效地提高了膜分离性能。CS与Pebax质量比为2:1时,渗透蒸发醇水分离性能及对酯化反应强化的性能达到最优:渗透通量703 g·m^-2·h^-1、分离因子308,较未改性CS膜分别提高61%、65%;反应8 h后的乳酸乙酯产率由58%提高至73%。     

聚乙烯醇与壳聚糖共混膜的研制与应用

将聚乙烯醇(PVA)和壳聚糖(CS)共混研制成渗透汽化(PVAP)复合膜,对乙醇水混合物具有较好的分离效果,膜的机械性能、耐水性等比纯聚乙烯醇膜有较大提高。用扫描电镜测定了膜的结构,讨论了共混配比、交联温度等成膜条件对膜性能的影响。     

柚皮素分子印迹膜的制备及评价

以壳聚糖(CS)为功能聚合物,聚乙烯醇(PVA)为添加剂,聚乙二醇(PEG)为致孔剂,水相共混,流延法制备了CS/PVA共混膜作为制备CS分子印迹膜的基本实验条件。实验优化了分子印迹膜的基础制备条件和工艺。在选定的膜配比下,以柚皮素(NG)为印迹分子,乙醇为洗脱剂,水相共混包埋制备了以NG为模板分子的壳聚糖分子印迹膜。结果表明,当m(NG)∶m(CS)=1/15时,印迹膜的容量最大。印迹膜较之非印迹膜,对NG有较大的透过量,NG分子的渗透量与印迹容量成正比,非印迹分子槲皮素在印迹膜上的渗透速率较低。相同浓度下,基膜组成为PVA/CS=0.6/1.4时印迹分子NG与竞争物桷皮素的分离因子为10.09,组成为PVA/CS=1.4/0.6时印迹分子NG与竞争物槲皮素的分离因子为8.40。     

柚皮素分子印迹膜的制备及评价

以壳聚糖(CS)为功能聚合物,聚乙烯醇(PVA)为添加剂,聚乙二醇(PEG)为致孔剂,水相共混,流延法制备了CS/PVA共混膜作为制备CS分子印迹膜的基本实验条件。实验优化了分子印迹膜的基础制备条件和工艺。在选定的膜配比下,以柚皮素(NG)为印迹分子,乙醇为洗脱剂,水相共混包埋制备了以NG为模板分子的壳聚糖分子印迹膜。结果表明,当m(NG)∶m(CS)=1/15时,印迹膜的容量最大。印迹膜较之非印迹膜,对NG有较大的透过量,NG分子的渗透量与印迹容量成正比,非印迹分子槲皮素在印迹膜上的渗透速率较低。相同浓度下,基膜组成为PVA/CS=0.6/1.4时印迹分子NG与竞争物桷皮素的分离因子为10.09,组成为PVA/CS=1.4/0.6时印迹分子NG与竞争物槲皮素的分离因子为8.40。     

有机物(水)混合物分离的国外膜工业现状

渗透汽化(PV)、蒸汽渗透(VP)膜分离方法,在有机物／水混合物、有机物／有机物混合物的分离中得到了广泛应用。本文基于美国专利和有关文献以及国际交往的有关资料,概要描述了国外特别是欧美等国发展的PV(VP)／膜工业现状,重点讨论了PV(VP)／膜、膜组器件及其成套膜分离装置和应用工艺的专利申请、生产商、应用领域、典型应用工程,分析了PV(VP)／膜技术的先进性、经济性和发展前景。     

丙烯膜法脱水工艺技术的研究分析

传统的丙烯脱水工艺存在能耗高、丙烯浪费大、再生氦器气用量大等缺点。蒸汽渗透技术具有能耗低、过程简单、分离因子高、操作灵活等优点，而且它的渗透通量较低，这使得它特别适用于微量可凝组分的分离。本研究以脱除丙烯中微量水分为目的，以聚乙烯醇、壳聚糖为复合膜活性层，聚砜中空纤维膜为支撑层，制备出多种中空纤维复合膜。考察制膜条件及实验操作条件对膜性能的影响。     

CS/PEO纳米纤维膜的制备及其用于圣女果保鲜的研究

以壳聚糖(CS)和聚氧化乙烯(PEO)为原料,通过静电纺丝制得CS/PEO纳米纤维膜,利用正交实验优化静电纺CS/PEO纳米纤维膜的制备工艺条件;研究了CS/PEO纳米纤维膜的结构和性能及其应用于圣女果的包装保鲜,并与CS/PEO流延膜(简称流延膜)、浸渍CS/PEO溶液的普通保鲜膜(简称涂膜)、基于普通保鲜膜的CS/PEO纳米纤维复合膜(简称复合膜)、普通保鲜膜的应用效果进行比较。结果表明:正交实验得到静电纺CS/PEO纳米纤维膜的最佳条件为CS与PEO质量比8:2,电压16 kV,接收距离10 cm,在此条件下制得的CS/PEO纳米纤维膜的拉伸强度为14.2 MPa,断裂伸长率为43.6%;CS/PEO纳米纤维膜、流延膜各组分之间存在强的相互作用并具有很好的相容性;使用最佳条件下制得的CS/PEO纳米纤维膜包裹圣女果,相对于用流延膜、涂膜、复合膜、普通保鲜膜、其他条件下制得的CS/PEO纳米纤维膜包裹圣女果,其保鲜效果最好,用其包裹圣女果12d后,圣女果失重率最小为6.3%,维生素C含量最高为289.2μg/g。     

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.     

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.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。