萃取精馏过程中萃取剂选择及萃取条件研究

采用改进的UNIFAC模型,借助于MATLAB计算软件,编制了相应的计算程序,用于萃取精馏过程中萃取剂的选择、萃取性能的考察以及萃取条件的影响研究。通过对甲醇-乙酸甲酯共沸体系在不同萃取剂和不同萃取条件下相对挥发度的计算,选择出适宜的萃取剂,并讨论了温度和溶剂比对相对挥发度的影响。     

动态法筛选萃取精馏分离乙酸丁酯-丁醇-水共沸物的溶剂

采用基于改进UNIFAC模型的动态法对萃取精馏法分离乙酸丁酯-丁醇-水共沸物的萃取剂进行了计算机高通量筛选,根据适宜萃取剂选取原则和计算结果,经综合考虑选出较好的萃取剂为甲醇、乙醇、环氧乙烷。选取乙醇进行实验验证,测定了乙酸丁酯-丁醇-水-乙醇体系的部分汽液平衡实验数据;泡点温度tb、加入溶剂后平衡汽相组成的计算值与实验值吻合良好;以乙醇作为萃取剂具有热负荷小、毒性低和热稳定性好的优点。结果表明,采用基于改进UNIFAC模型的动态法筛选萃取精馏法的溶剂具有良好的可靠性和适用性,可以极大地节省人力、物力和财力。     

萃取精馏及进展

萃取精馏是一种特殊精馏方法 ,适用于近沸点物系和共沸物的分离。萃取精馏按操作方式可分为连续萃取精馏和间歇萃取精馏 ,间歇萃取精馏是近年发展起来的新的萃取精馏方法。萃取精馏的关键是溶剂的选择 ,以往萃取精馏采用的溶剂是单一溶剂 ,近年来人们开始研究使用混合溶剂 ,取得了良好效果     

改进的UNIFAC模型在萃取精馏溶剂选择的应用

针对基团贡献法在萃取精馏溶剂选择的运用，首先测定了乙醇一水等七个共沸体系在相应的萃取剂体系中的汽液平衡数据，然后对溶剂的选择性进行了分析并考察了溶剂比(质量比)对轻重组分之间相对挥发度的影响；利用修正的UNFIAC模型对实验数据进行了关联和比较，计算值和实验值的相对误差均在5．0％以内；与萃取精馏溶剂选择的其它方法相比，利用改进的UNIFAC模型预测和实验相结合的方法在实际运用中更具有高效性。     

分子模拟评价萃取精馏萃取剂的新方法

萃取精馏是强化分离的有效方法,选用不同的萃取剂对萃取精馏过程的可行性和经济性有很大影响。探索性地使用分子模拟软件Material Studio 计算二元物系的混合能来作为萃取剂优劣的判据。以苯和环己烷为待分离物系,选择多种溶剂作为萃取剂,计算萃取剂分子与苯分子之间的混合能以及萃取剂分子与环己烷分子之间的混合能,并计算2个混合能的差值。以文献报导的选择性和以热力学NRTL方程计算无限稀释活度系数得到的选择性为标准来验证使用混合能差值评价萃取剂优劣的合理性。验证结果表明混合能差值基本随选择性的增加而增大,这一结论为进一步深入理论研究和新的萃取剂选择方法的开发打下了基础。     

萃取精馏分离乙腈-正丙醇的研究

采用萃取精馏的方法分离乙腈-正丙醇的共沸物系。首先利用溶剂选择原理和UNIFAC基团贡献法选出N-甲基吡咯烷酮作为萃取精馏的萃取剂,同时采用NRTL模型对常压下乙腈-正丙醇物系和加入萃取剂N-甲基吡咯烷酮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。然后通过间歇萃取精馏实验进一步考察所选萃取剂的分离效果。结果表明,N-甲基吡咯烷酮能够打破共沸,有效分离乙腈-正丙醇共沸物系。采用有28块理论板的填料塔,萃取剂进料位置为第4块板,溶剂比为1.0,回流比为3,可以从塔顶得到质量分数为98.6%的乙腈产品。最后,用Aspen Plus软件对乙腈-正丙醇物系的连续萃取精馏流程进行了模拟,得出的参数为进一步的工业应用奠定基础。     

从溶剂油中提纯连三甲苯的萃取精馏溶剂选择

为了快速准确地选择萃取精馏溶剂,由190#溶剂油萃取精馏获取高纯度连三甲苯,运用UNIFAC模型,计算了质量比为4∶1的连三甲苯-茚满体系在苯乙酮、乙二醇、邻苯二甲酸二辛酯、二甲基亚砜和环丁砜5种溶剂中在17.47 kPa下的相对挥发度。同时测定了对应5个体系的汽液平衡数据,计算值和实验值的相对平均偏差均小于6％,两者吻合良好。结果表明：环丁砜较适宜作为萃取剂。与其它萃取剂选择方法比较,这种UNIFAC模型预测和实验验证相结合的方法具有快速准确的优点。     

乙醇浓缩和回收的萃取剂及萃取精馏工艺

用G102色谱仪筛选乙醇和水萃取精馏分离的萃取溶剂;提出乙醇和水萃取精馏分离的新工艺,用徽机模拟该工艺的分离结果,比较该工艺与其它工艺之间的能耗差别。     

萃取精馏分离丙醇-水-乙酸丙酯混合物

为挑选萃取精馏分离丙醇-水-乙酸丙酯混合物较好的溶剂,采用基于UNIFAC模型的动态法对待选溶剂进行了计算机高通量筛选。根据加入溶剂后体系互溶性和相对挥发度大小的预测结果,经综合考虑选出较好的萃取剂为丁醇和甲醇。选取丁醇为溶剂做实验验证,测定了丙醇-水-乙酸丙酯-丁醇体系的部分汽液平衡实验数据;泡点温度tb、加入溶剂后的相对挥发度α和平衡气相组成yi的计算值与实验值吻合良好,这表明采用基于UNIFAC模型的动态法筛选萃取精馏的溶剂具有良好的可靠性和适用性。     

间歇萃取精馏分离乙腈-甲苯共沸体系

应用UNIFAC基团贡献法推导出的萃取剂选择模型,选出异丙苯、对叔丁基甲苯、对二乙基苯为乙腈-甲苯体系的萃取剂,通过气液平衡试验测定了乙腈-甲苯体系和乙腈-甲苯在萃取剂存在下的气液平衡关系,并应用UNIFAC活度系数模型进行气液平衡计算。通过间歇萃取精馏试验考察了不同萃取剂的效果,结果表明,对二乙基苯是最佳的萃取剂,同时研究了回流比、溶剂比对间歇萃取精馏的影响。     

焦油一次汽化温度计算方法的探讨

利用相平衡原理得出的焦油蒸馏时一次汽化温度的计算方法,其结果与按经验公式的计算结果进行了比较,同时讨论了一次汽化温度与焦油馏分产率及二段蒸发器过热蒸汽用量的关系。     

Techniques for screening adhesives for structural applications

—Due to its chemistry, no structural adhesive system (epoxies, acrylics, etc.) is likely to offer an ideal combination of toughness, strength, moisture resistance, and ambient-temperature curing. Therefore, for effective use of adhesives in primary structures, an engineer must be able to identify adhesives that represent an optimum compromise among the different properties. In this paper, we present techniques for screening high-strength, ambient-temperature-curing adhesives for (1) moisture resistance under sustained loading and (2) fracture resistance in a way that is directly related to joint performance.     

Efficacy for Whitlockite for Augmenting Spinal Fusion

Whitlockite (WH) is the second most abundant inorganic component of human bone, accounting for approximately 25% of bone tissue. This study investigated the role of WH in bone remodeling and formation in a mouse spinal fusion model. Specifically, morphology and composition analysis, tests of porosity and surface area, thermogravimetric analysis, an ion-release test, and a cell viability test were conducted to analyze the properties of bone substitutes. The MagOss group received WH, Group A received 100% beta-tricalcium phosphate (β-TCP), Group B received 100% hydroxyapatite (HAp), Group C received 30% HAp/70% β-TCP, and Group D received 60% HAp/40% β-TCP (n = 10 each). All mice were sacrificed 6 weeks after implantation, and micro-CT, hematoxylin and eosin (HE) staining, and Masson trichome (MT) staining and immunohistochemistry were performed. The MagOss group showed more homogeneous and smaller grains, and nanopores (<500 nm) were found in only the MagOss group. On micro-CT, the MagOss group showed larger fusion mass and better graft incorporation into the decorticate mouse spine than other groups. In the in vivo experiment with HE staining, the MagOss group showed the highest new bone area (mean: decortication group, 9.50%; A, 15.08%; B, 15.70%; C, 14.76%; D, 14.70%; MagOss, 22.69%; p < 0.0001). In MT staining, the MagOss group demonstrated the highest new bone area (mean: decortication group, 15.62%; A, 21.41%; B, 22.86%; C, 23.07%; D, 22.47%; MagOss, 26.29%; p < 0.0001). In an immunohistochemical analysis for osteocalcin, osteopontin, and CD31, the MagOss group showed a higher positive area than other groups. WH showed comparable bone conductivity to HAp and β-TCP and increased new bone formation. WH is likely to be used as an improved bone substitute with better bone conductivity than HAp and β-TCP.     

Demand Increases for New Fungicides for Rice

<正> After June this year China's regions growingmiddle and late rice had widespread blastand sheath/culm blight.Such diseasesplagued 19.2 million hectares.Starting fromJuly the market for new fungicides that cancontrol blast and sheath/culm blight for ricewas more and more active.Makers of traditional pesticides for thecontrol of blast have to contend with fiercecompetition from new pesticides in marketthis year.Kitazine,iprobenfos,isoprothiolane and tricyclazole,oftenused by farmers in the past,are graduallybeing replaced by new varieties with high