Hyperbranched polymer hollow-fiber-composite membranes for pervaporation separation of aromatic/aliphatic hydrocarbon mixtures

The separation of aromatic/aliphatic hydrocarbon mixtures is crucial in the petrochemical industry.Pervaporation is regarded as a promising approach for the separation of aromatic compounds from alkanes. Developing membrane materials with efficient separation performance is still the main task since the membrane should provide chemical stability, high permeation flux, and selectivity. In this study, the hyperbranched polymer(HBP) was deposited on the outer surface of a polyvinylidene fluoride(PVDF)hollow-fiber ultrafiltration membrane by a facile dip-coating method. The dip-coating rate, HBP concentration, and thermal cross-linking temperature were regulated to optimize the membrane structure.The obtained HBP/PVDF hollow-fiber-composite membrane had a good separation performance for aromatic/aliphatic hydrocarbon mixtures. For the 50%/50%(mass) toluene/n-heptane mixture, the permeation flux of optimized composite membranes could reach 1766 g·m^(-2)·h^(-1), with a separation factor of 4.1 at 60℃. Therefore, the HBP/PVDF hollow-fiber-composite membrane has great application prospects in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures.

Highly selective extraction of aromatics from aliphatics by using metal chloride-based ionic liquids

The separation of aromatics from aliphatics is essential for achieving maximum exploitation of oil resources in the petrochemical industry.In this study,a series of metal chloride-based ionic liquids were prepared and their performances in the separation of 1,2,3,4-tetrahydronaphthalene(tetralin)/dodecane and tetralin/decalin systems were studied.Among these ionic liquids,1-ethyl-3-methylimidazolium tetrachloroferrate([EMIM][FeCl_(4)])with the highest selectivity was used as the extractant.Density functional theory calculations showed that[EMIM][FeCl_(4)]interacted more strongly with tetralin than with dodecane and decalin.Energy decomposition analysis of[EMIM][FeCl_(4)]-tetralin indicated that electrostatics and dispersion played essential roles,and induction cannot be neglected.The van der Waals forces was a main effect in[EMIM][FeCl_(4)]-tetralin by independent gradient model analysis.The tetralin distribution coefficient and selectivity were 0.8 and 110,respectively,with 10%(mol)tetralin in the initial tetralin/dodecane system,and 0.67 and 19.5,respectively,with 10%(mol)tetralin in the initial tetralin/decalin system.The selectivity increased with decreasing alkyl chain length of the extractant.The influence of the extraction temperature,extractant dosage,and initial concentrations of the system components on the separation performance were studied.Recycling experiments showed that the regenerated[EMIM][FeCl_(4)]could be used repeatedly.

Membrane materials in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures—A review

The separation of aromatic/aliphatic hydrocarbon mixtures is a significant process in chemical industry, but challenged in some cases. Compared with conventional separation technologies, pervaporation is quite promising in terms of its economical, energy-saving, and eco-friendly advantages. However, this technique has not been used in industry for separating aromatic/aliphatic mixtures yet. One of the main reasons is that the separation performance of existed pervaporation membranes is unsatisfactory. Membrane material is an important factor that affects the separation performance. This review provides an overview on the advances in studying membrane materials for the pervaporation separation of aromatic/aliphatic mixtures over the past decade. Explored pristine polymers and their hybrid materials(as hybrid membranes) are summarized to highlight their nature and separation performance. We anticipate that this review could provide some guidance in the development of new materials for the aromatic/aliphatic pervaporation separation.

Effect of the Structure of Cations and Anions of Ionic Liquids on Separation of Aromatics from Hydrocarbon Mixtures

The effects of the structure of typical cations and anions of ionic liquids on the separation of benzene and toluene from aromatic/paraffin mixtures were studied. The .results showed that the corresponding separation factors were considerably larger than those of the traditional solvents （Benzene＋Hexane＋sulfolane）, and that the ionic liquids could be used as novel solvents for the separation of aromatics from hydrocarbon mixtures. The key parameters governing the ability of ionic liquids for separating aromatics from hydrocarbon sources were investigated. It was found that the effectiveness of the ionic liquids, based on the same anion, changed in the cation order of [BIqu]^＋〈 [BPy]^＋〈 [BMIM]^＋. The selectivity of the ionic liquid toward aromatics decreased apparently with the increasing length of the substituted alkyl chain of its cationic head ring. The separation factors, based on the same cation, changed in the anion order of [Tf2N]^-〈[PF6]^-〈[BF4]^-〈[C2H5SO4]^-. The solubilities of the aromatics were greater in the ionic liquids based on the former three anions than that in the ionic liquids involving [C2H5SO4]^-.

Preparation and characterization of biodegradable aliphatic-aromatic copolyesters/nano-SiO_2 hybrids via in situ melt polycondensation

In situ melt polycondensation was proposed to prepare biodegradable aliphatic-aromatic copolyesters/nano-SiO2 hybrids based on terephthalic acid （TPA）, poly（L-lactic acid） oligomer （OLLA）, 1,4-butanediol （BDO） and nano-SiO2. TEM and FT-IR characterizations confirmed that TPA, OLLA and BDO copolymerized to obtain biodegradable copolyesters, poly（butylene terepbthalate-co-lactate） （PBTL）, and the abundant hydroxyl groups on the surface of nano-SiO2 provided potential sites for in situ grafting with the simultaneous resulted PBTL. The nano-SiO2 particles were chemically wrapped with PBTL to form PBTL/nano- SiO2 hybrids. Due to the good dispersion and interfacial adhesion of nano-SiO2 particles with the copolyester matrix, the tensile strength and the Young＇s modulus increased from 5.4 and 5.6 MPa for neat PBTL to 16 and 390 MPa for PBTL/nano-SiO2 hybrids with 5 wt.% nano-SiO2, respectively. The mechanical properties of PBTL/nano-SiO2 hybrids were substantially improved.

BIODEGRADABLE ALIPHATIC/AROMATIC COPOLYESTERS BASED ON TEREPHTHALIC ACID AND POLY(L-LACTIC ACID):SYNTHESIS,CHARACTERIZATION AND HYDROLYTIC DEGRADATION

Biodegradable aliphatic/aromatic copolyesters, poly（butylene terephthalate-co-lactate） （PBTL） were prepared via direct melt polycondensation of terephthalic acid （TPA）, 1,4-butanediol （BDO） and poly（L-lactic acid） oligomer （OLLA）. The effects of polymerization time and temperature, as well as aliphatic/aromatic moiety ratio on the physical and thermal properties were investigated. The largest molecular weight of the copolyesters was up to 64100 with molecular weight distribution index of 2.09 when the polycondensation was carried out at 230℃ for 6 h. DSC, XRD, DMA and TGA analysis clearly indicated that the degree of crystallinity, glass-transition temperature, melting point, decomposition temperature, tensile strength, elongation and Young＇s modulus were influenced by the ratio between TPA and OLLA in the final copolyesters. Hydrolytic degradation results demonstrated that the incorporation of biodegradable lactate moieties into the aromatic polyester could efficiently improve hydrolytic degradability of the copolymer even though it still had many aromatic units in the main chains.

Study on Structure and Crystallinity of A New Biodegradable Aliphatic-Aromatic Copolyester

A series of biodegradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-butylene adipate-co- ethylene terephthalate-co-ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic acid (AA), 1,4-butanediol (BG) and ethylene glycol (EG) through direct esterification and polycondensation. The sequence structure and crystallinity of the copolyester were investigated by 1H NMR spectroscopy and the wide-angle X-ray diffractometry (WAXD). The analytical results showed that the PBATE copolyester was a random copolymer and the composition of PBATE copolyester was almost consistent with the feed molar ratios. The crystal structure of PBATE copolyester belonged to the triclinic crystalline system; The variation in melting point of the synthesized PBATE copolyester agreed well with the estimation obtained by the Flory equation and was applicable to the random copolymer.

Selective separation of pyrene from mixed polycyclic aromatic hydrocarbons by a hexahedral metal-organic cage

Polycyclic aromatic hydrocarbons(PAHs)play an important role in the industry,and the development of new materials for the selective separation of PAHs is of great significance.In this work,we report a hexahedral metal-organic cage with low symmetry by subcomponent self-assembly.In this cage,the eight ZnII centers adopt an interestin∧∧/△△△△△△or∧∧∧∧∧∧/△△configuration.This cage with a cavity volume of 520˚A3 can bind anthracene,phenanthrene,and pyrene to form 1:1 host-guest complexes,while the bigger triphenylene,chrysene,perylene,and coronene cannot be encapsulated.The binding constant Ka of pyrene is about 1.110×10^(3)(mol/L)^(−1),which is more than an order of magnitude larger than that of anthracene and phenanthrene(111(mol/L)^(−1),277(mol/L)^(−1),respectively).X-ray structure studies reveal that the pyrene is located in the cavity and stabilized by multiple C–H…πinteractions.After separation from a mixture of PAHs,pyrene with>96.1%purity can be obtained.This work provides a useful method for the first time for the selective separation of pyrene from PAHs mixture by utilizing a metal-organic cage as the material,making it a useful tool for purifying and separating specific compounds from complex mixtures.

Fast analysis of derivatives of polycyclic aromatic hydrocarbons in soil by ultra-high performance supercritical fluid chromatography after supercritical fluid extraction enrichment

An efficient and environment-friendly method for simultaneous determination of 13 typical derivatives of polycyclic aromatic hydrocarbon(PAH)in petroleum-polluted soil with nitro-,oxy-and alkylfunctional group was developed using supercritical fluid extraction(SFE)followed by ultra-high performance supercritical fluid chromatography(UHPSFC).Parameters of UHPSFC,including type of stationary phase and mobile phase modifiers,gradient elution process,backpressure,column temperature,and the flow rate of mobile phase,were systematically optimized,achieving a fast separation within4.2 min.Limits of detection(LOD)were 0.005-0.1μg mL^(-1)or 0.1-2.0 ng g^(-1),respectively,with a good repeatability(RSD<5.0%).Before UHPSFC-PDA analysis,the PAH-derivatives in soil samples were effectively enriched in 15.0 min using SFE with an online carbon nanotubes(CNTs)collection trap.The soil samples were analyzed by the proposed method and the results were verified by GC-MS.Thus,SFE equipped with an online CNTs trap followed by UHPSFC-PDA analysis,which only consumed about2.0 mL organic solvent for a whole run,has been demonstrated to be an efficient way for screening and quantitative analysis of trace-level PAH-derivatives in soil samples.

THE GAS TRANSPORT BEHAVIOR IN AROMATIC POLYESTER MEMBRANES

Six aromatic polyesters were prepared for gas separation membranes, and their permeation properties for hydrogen, oxygen, nitrogen, carbon dioxide, and methane were measured at 30 degrees C and 1 atmosphere by low pressure manometric method. The correlation between the gas transport behavior and molecular structure of aromatic polyester membrane is discussed. These data are interpreted qualitatively in terms of the calculated packing density, gas-polymer interaction, concentration of aryl bromine on backbone, and effect of silane group on main chain of polymer.

Exergy and exergoeconomic analyses for integration of aromatics separation with aromatics upgrading

Methanol to aromatics produces multiple products,resulting in a limited selectivity of xylene.Aromatics upgrading is an effective way to produce more valuable xylene product,and different feed ratios generate discrepant product distributions.This work integrates the aromatics separation with toluene disproportionation,transalkylation of toluene and trimethylbenzene,and isomerization of xylene and trimethylbenzene.Exergy and exergoeconomic analyses are conducted to give insights in the splitting ratios of benzene,toluene and heavy aromatics for aromatics upgrading.First,a detailed simulation model is developed in Aspen HYSYS.Then,300 splitting ratio sets of benzene and toluene for conversion are studied to investigate the process performances.The results indicate that there are different preferences for the splitting ratios of benzene and toluene in terms of exergy and exergoeconomic performances.The process generates lower total exergy destruction when the splitting ratio of toluene varies between 0.07 and 0.18,and that of benzene fluctuates between 0.55 and 0.6.Nevertheless,the process presents lower total product unit cost with the splitting ratio of toluene less than 0.18 and that of benzene fluctuating between 0.44 and 0.89.Besides,it is found that distillation is the biggest contributor to the total exergy destruction,accounting for 94.97%.

Computational Study for the Aromatic Nucleophilic Substitution Reaction on 1-Dimethylamino-2,4-bis(trifluoroacetyl)-naphthalene with Amines

Our previous research showed that aliphatic amines were put in order of high reactivity as “ethylamine > ammonia > t-butylamine > diethylamine” on the aromatic nucleophilic substitution of 1-dimetylamino-2,4-bis(trifluoroacetyl)-naphthalene 1 in acetonitrile. The DFT calculation study (B3LYP/6-31G* with solvation model) for the reactions of 1 with above four amines rationally explained the difference of each amines reactivity based on the energies of their Meisenheimer complexes 3 which are assumed to formed as the reaction intermediates in the course of the reaction giving the corresponding N-N exchange products 2. Intramolecular hydrogen bond between amino proton in 1-amino group and carbonyl oxygen in 2-trifluoroacetyl group stabilizes Meisenheimer complexes 3 effectively, and accelerates the substitution reaction from 1 to 2. Our calculation results also predicted that the above order of amines is also true if less polar toluene is used as a solvent instead of acetonitrile even though more enhanced conditions are required.

芳香烃/环烷烃吸附分离材料研究进展

吸附法由于其节能环保的特性有潜力替代萃取精馏成为分离同碳数芳香烃/环烷烃的新方法,目前采用的吸附分离材料已从传统的沸石分子筛发展到包括金属-有机框架材料(MOFs)、共价有机框架(COFs)和多孔分子晶体(PMCs)在内的新型多孔材料,体现出优异的选择性、优先吸附芳香烃或环烷烃的能力。本文综述了近年来MOFs、COFs和PMCs在苯/环己烷和甲苯/甲基环己烷分离中的研究进展,重点介绍了三类材料结构的设计思路、吸附分离性能及其机理,包括热力学平衡、分子排阻等两类不同的机理。在取得较大研究进展的同时,该领域也存在一些较为突出的问题,如对吸附质扩散传质规律和混合物固定床分离性能研究不足、对材料稳定性和杂质敏感性关注较少、多孔材料结构复杂、经济性有待提升等,在未来的研究中需予以重视。

生物基半芳香族共聚酰胺PA5T/56与脂肪族聚酰胺PA56的性能对比

生物基聚酰胺PA56凭借其绿色低碳的原料来源以及与商业化PA66相近的综合性能而受到关注,但受限于脂肪族的柔性主链结构,无法满足高温场景下的使用需求。为解决上述问题,引入对苯二甲酸构筑生物基半芳香族共聚酰胺PA5T/56,对PA5T/56的结构及性能进行系统研究,并与生物基脂肪族聚酰胺PA56进行对比分析。红外光谱与核磁共振氢谱的表征结果验证了PA5T/56与PA56结构上的差异;相比PA56,PA5T/56具有更高的玻璃化转变温度(t_(g)=113℃)、更优的热稳定性(t_(d,5%)=392℃,t_(dmax)=423℃),以及更佳的热机械性能,同时其在高温下具有适宜加工的熔体黏度(<10^(3)Pa·s),这些优势赋予生物基半芳香族PA5T/56广阔的应用前景。

芳香性聚氨基酸破乳剂的制备及性能评价

以芳香族氨基酸苯丙氨酸为疏水单体、脂肪族氨基酸天冬氨酸为亲水单体,通过氨基酸N-羧基环内酸酐(NCA)单体的开环聚合(ROP),制备了一系列强极性、高芳香度的聚氨基酸类高分子破乳剂聚苯丙氨酸-聚天冬氨酸苄酯(PPA-b-PBAA),并对产物进行了结构表征和相对分子质量测定。采用瓶试法评价了PPA-b-PBAA的破乳性能,结果表明PPA-b-PBAA具有优秀的低温破乳效率,室温下2 min内能高效分离pH=6.0~11.0、含油量1.0%~10.0%(质量分数)的稀释沥青乳状液。其中,PPA-b-PBAA对1.0%(质量分数)的含油乳化废水的最佳脱水效率达到了99.98%,相应脱出水中残余油含量低至8.50 mg/L。破乳机理研究表明,PPA-b-PBAA加入油水乳状液后能快速迁移到达油水界面,通过与形成油水界面膜的沥青质、胶质相互作用,促使分散油滴絮凝聚并,实现油水分离。量子化学计算和弱相互作用分析表明,破乳剂PPA-b-PBAA分子与形成油水界面膜的主要成分沥青质之间产生的强相互作用有利于加速油水界面膜破裂和分散油滴聚并,是助推PPA-b-PBAA低温高效快速破乳脱水的关键。

C_(8)芳烃中乙苯吸附分离材料的制备与性能研究

采用水热合成法制备低硅铝比X型分子筛(LSX),通过离子改性法研究了离子种类、交换次数等制备Rb-LSX的最佳条件。利用单组分和多组分吸附实验探究吸附时间、溶液浓度等对C_(8)芳烃吸附分离的影响,并对其进行吸附动力学、吸附等温线和吸附扩散性能研究。结果表明,在298 K下,单组分吸附实验中C_(8)芳烃在Rb-LSX上的吸附量大小为:乙苯(EB,162.05 mg/g)>对二甲苯(PX,141.00 mg/g)>间二甲苯(MX,128.67 mg/g)>邻二甲苯(OX,125.02 mg/g),且Rb-LSX对4种芳烃分子的吸附过程符合Langmuir等温线模型和准二级动力学模型;在多组分吸附实验中,EB/PX、EB/MX和EB/OX的选择性分别为6.94、5.41、7.20;C_(8)芳烃分子在Rb-LSX分子筛中的扩散能力大小为:EB>MX>PX>OX。

伊敏褐煤腐植酸结构特征及其分子模型构建

从褐煤中提取腐植酸对于实现褐煤的清洁高效利用具有重要的意义,而探究蒙东地区褐煤腐植酸结构并构建相应的分子模型对于该地区褐煤应用具有广泛的指导作用。采用碱溶酸析法提取蒙东伊敏褐煤的腐植酸,通过采用X射线衍射、^(13)C核磁共振以及X射线光电子能谱等方法对腐植酸的结构特征进行全面表征。结果表明:伊敏褐煤腐植酸中的芳香结构是基础,而脂肪结构主要以交联键以及侧链形式存在;褐煤腐植酸中的芳香团簇尺寸较小,芳香层间距相对较大,且呈现无序排列。根据结构表征相关参数,重构了具有代表性的中国蒙东伊敏褐煤腐植酸分子模型。所构建的伊敏褐煤腐植酸分子结构模型计算数据与实验数据大体吻合,能够充分反映伊敏褐煤腐植酸的化学结构特点。模型中芳香碳结构主要以苯、萘环的形式呈现,少量以菲环形式的存在;脂肪碳主要以较短的侧链和脂肪环形式存在,起到连接芳香基本结构单元的作用。氧元素主要以羧基和酯等O—C=O形式存在,同时还包括一定量的酮、醛、醌、酚、醇以及醚氧,其中羰基C O和醚氧具有交联作用。氮元素则主要以吡咯环的形式存在,并伴有少量的吡啶环和季氮。与西南地区云南褐煤腐植酸结构相比,伊敏褐煤中的芳香碳含量更高且吡咯含氮官能团所占比例也更大,并呈现出一定的地区差异性。

芳香羧酸配合物分离纯化轻烃的应用研究进展

轻烃的分离纯化是工业上最耗能的工艺之一,开发低能耗、环境友好型的节能材料是迫切的。芳香羧酸配合物结构中有可调控的亚纳米孔道,在分离纯化技术中是优质的候选材料。总结了芳香羧酸配合物在轻烃的分离纯化中应用研究,并且最后提出该材料未来的发展前景和挑战。

工艺条件对柴油吸附分离重芳烃轻质化反应的影响

馏分油芳烃吸附分离技术是炼厂过剩汽、煤、柴油资源高效利用的途径。分离得到的非芳烃组分可通过蒸汽裂解或催化裂解增产低碳烯烃,以单环芳烃为主的芳烃组分则可通过重芳烃轻质化技术增产苯、甲苯和二甲苯等轻质芳烃,同时副产优质乙烯裂解原料。以吸附分离重芳烃组分为原料,测定了氢气溶解量。吸附分离重芳烃油中氢气的溶解量随温度和氢压的增加而增加,达到1.0×10^(-4)~3.2×10^(-4) mol/g,比油中多环芳烃加氢成单环芳烃所需理论耗氢量低1~2个数量级。进一步采用NiMo/β轻质化催化剂在固定床反应器上考察了催化剂还原条件、反应器高径比、反应温度、氢分压、氢油比、空速等工艺参数对吸附分离重芳烃轻质化反应的影响。在低温高压(350℃、4 MPa)的还原工况下,反应器高径比为4.5、反应温度为400~410℃、氢分压为5.0~5.5 MPa、氢油体积比为800~1 000、质量空速为1~1.5 h^(-1)的条件下,吸附分离重芳烃轻质化效果最佳,C^(+)_(10)转化率≥85%,C_(6)~C_(9)芳烃收率≥50%,C_(6)~C_(9)芳烃纯度≥97.5%。柴油芳烃吸附分离和重芳烃轻质化可实现高效耦合,显著提高化工品收率,具有重大的现实意义和广阔的应用前景。

基于烃组成分离的原油催化裂解反应探究

随着炼油行业高质量发展,石油资源加工将更加追求分子利用效率和全价值链优化与管理。从烃分子结构管理角度入手,尊重原油中原生分子结构,以产品分子结构为导向,通过原油组分分离,使催化裂解原料中优势组分富集,以提高催化反应效率与过程选择性。详细研究了原油馏分油组分分离前后的催化裂解反应性能,提出原油组分分离-催化裂解技术方案。中间基科威特原油经组分优化后,低碳烯烃和轻芳烃的总产率达42%以上,实现了原油组分“宜烯则烯,宜芳则芳”,从分子角度最大化地利用了原油资源。