乙烯-乙烷分离用络合吸附剂的制备及吸附平衡

引言 乙烯-乙烷分离在石油化工和化学工业中占有重要地位,虽然深冷精馏分离工艺已工业应用60多年,但其操作费用很高,因此需要开展新型的烯烃-烷烃分离技术的研究其中基于π-络合原理的化学吸附分离具有良好的应用前景,受到国内外广泛关注[1-3].     

离子液体在低碳烯烃/烷烃分离中的应用研究进展

低碳烯烃/烷烃的高效分离是石油化工领域可持续发展的关键过程之一,传统的低温精馏过程选择性低、能耗大。离子液体作为一种结构可调的绿色溶剂为低碳烃的高效分离提供了新的思路。本文综述了近年来国内外离子液体在低碳烯烃/烷烃分离中的研究进展,总结了常规离子液体、功能化离子液体以及含过渡金属的离子液体在低碳烯烃/烷烃分离中的应用,阐明了离子液体中阴阳离子、功能化基团、过渡金属与低碳烯烃相互作用的机理,着重介绍了合成金属功能化离子液体、添加金属盐、添加金属纳米粒子3种向离子液体中引入过渡金属方式的特点以及过渡金属的种类、比例,有机配体的类型对离子液体烯烃/烷烃分离性能的影响,并探讨了该方向的研究和发展趋势。     

多孔炭吸附剂的乙烯-乙烷选择性反转机制

烯烃是重要的化工原料,吸附分离技术可在温和工况下实现烯烃纯化,而吸附剂的烷烃选择性是实现高效化工分离过程的关键。基于分子模拟,提出调节孔道尺寸以控制多孔炭优先吸附乙烯或乙烷的选择性反转机制;控制活化条件,实验制备出不同孔径的多孔炭材料并验证了乙烯-乙烷选择性反转规律。结果表明,多孔炭的石墨化表面优先吸附乙烷;随着孔径尺寸的增大,可出现优先吸附乙烯的孔道区间;若孔径进一步增大,多孔炭可回归到优先吸附乙烷的石墨化表面吸附特征。选择性反转机制适用于不同形状的孔道结构。因此,可利用微孔孔道的限域作用放大多孔炭表面的烷烃选择性,并得到高性能的烷烃选择性吸附剂。     

SAPO-34分子筛应用研究进展

综述了SAPO-34分子筛催化低碳物转化制低碳烯烃(甲醇、二甲醚、卤化烷烃制烯烃、乙醇脱水制乙烯)、C_4～C_8直链烯烃/烷烃裂解制低碳烯烃、烷烃氧化或直接脱氢反应制烯烃、催化烃类或H_2选择性还原NO_x、制备膜分离材料以及在发光体材料等领域中的应用。系统分析sAPO-34分子筛在各领域应用进展,有利于理解材料的物化性能对其催化性能、热稳定性及水热稳定性、选择性渗透和分子筛分离性能的影响,有利于实现对SAPO-34分子筛的认识取得突破性进展,拓展SAPO-34分子筛应用领域,并为其他催化材料的设计提供借鉴。     

轻质烯烃-烷烃分离新工艺开发进展

介绍了用于乙烯、丙烯等轻质烯烃与相应烷烃分离的化学吸收、吸附和膜分离等新工艺。评价了膜分离法具有分离因子高、能耗低、清洁、环保特点,但膜的稳定性还有待改进,膜材料的价格较昂贵;认为膜与蒸馏相结合的复合分离技术具有潜在的工业应用价值。     

乙烷脱氢催化剂研究进展

乙烯是重要的有机化工原料,随着乙烯需求量的不断增加以及石油资源的日益匮乏,乙烷脱氢已成为乙烯增产的重要途径。乙烷脱氢制乙烯受到越来越多的关注,乙烷脱氢催化剂逐步改善。本文首先介绍了近年来国内外乙烷脱氢制乙烯的研究现状,然后从催化剂制备方法、性能以及应用等方面对乙烷催化脱氢催化剂和乙烷氧化脱氢催化剂的研究进行了总结,并对其进行了系统分类。催化脱氢是低碳烷烃转化为烯烃的有效途径,烯烃选择性高,受到热力学平衡限制,能耗较高。氧化脱氢由于氧化剂的引入打破了热力学平衡限制,能够有效抑制焦炭的生成,减少能量消耗。然而,深度氧化反应难于控制,乙烯的选择性低。因此,选取合适的催化脱氢催化剂,尽可能提高乙烷单程转化率、降低能耗是乙烷脱氢的关键。     

聚乙烯合成过程中烯烃尾气膜法分离

采用卷式膜分离器对聚乙烯生产过程的排放气中烯烃进行分离与浓缩,考察膜分离器数目、原料气组成和操作温度等对分离过程的影响.结果表明使用两级膜分离器串联,乙烯浓缩约2倍,丁烯浓缩约1.6倍.     

烯烃/链烷烃分离工艺进展

当前开发的烯烃 /链烷烃分离技术有物理吸收法、化学吸收法、吸收分离法、萃取蒸馏法及膜分离法。其中最有发展前途的是利用π 配合作用的化学吸收法 ,现已有工业化装置。将蒸馏与吸附相结合的复合分离技术 ,是烯烃 /链烷烃分离技术的发展方向之一。     

金属有机框架材料分离低碳烃的研究进展

烯烃、烷烃和炔烃等结构相似物的高效分离是石油化学工业可持续发展的关键过程之一。低碳烃化合物结构和性质相近,仅在碳数和不饱和度存在微小差异,传统低温精馏过程选择性低、能耗高。金属有机框架材料/多孔配位聚合物（MOF/PCP）的结构多样性及可设计性使其可以精确识别相似物分子间的微小差异,在低碳烃分离领域取得重要进展。综述了金属有机框架材料在碳二/碳三的烯烃、炔烃和烷烃分离体系中取得的最新进展以及分离机理,探讨了金属有机框架材料在低碳烃吸附分离研究中存在的问题和发展方向。     

Cr/SSZ-13催化二氧化碳氧化乙烷脱氢反应的研究

通过脱氢反应将低碳烷烃转化为同碳数的烯烃是烷烃高值化利用和烯烃原料多元化的重要途径。烷烃氧化脱氢制烯烃的反应具有不受反应平衡限制、积炭少、反应温度低等优点,一直是研究的热点。通过利用浸渍法制备不同铬（Cr）负载量的Cr_x/SSZ-13系列催化剂,采用氮气物理吸附、氨程序升温脱附（NH₃-TPD）、二氧化碳程序升温脱附（CO₂-TPD）、氢气程序升温还原（H₂-TPR）、紫外-可见吸收光谱（UV-Vis）以及高角度环形暗场-扫描透射电镜（HAADF-STEM）与耦合能谱分析（EDX-Mapping）等方法对催化剂进行了物性表征,并用微型固定床反应器评价催化剂对乙烷氧化脱氢制乙烯的催化性能,最终建立了Cr/SSZ-13催化剂的构效关系。研究发现,当n（二氧化硅）/n（氧化铝）=10时,Cr_1.5/SSZ-13-10催化剂上含有丰富的Cr³⁺物种,其中配位不饱和Cr³⁺是优异的脱氢活性位,有利于二氧化碳氧化乙烷脱氢反应的进行。因此,Cr_1.5/SSZ-13催化剂在650 ℃时表现出优异的催化性能,即二氧化碳转化率和乙烷转化率分别达到26.41%和53.2%,乙烯产率为38.83%。     

Lösungsmittel-Auswahl bei der Flüssig/Flüssig-Extraktion unter physikalisch-chemischen Aspekten

Selection of solvents in liquid-liquid extraction according to physico-chemical aspects . Selection of appropriate solvents for liquid-liquid extraction is frequently necessary in process design. High selectivity and capacity are important, but not the only considerations in choosing suitable solvents. In comparing the various solvents, their selectivity and capacity should be examined at infinite dilution of the solute in the solvent. The required limiting activity coefficients may be estimated if no experimental data are available. A preselection of solvents may be accomplished by considering the interactions of the molecules. There are certain parameters quantifying the ability of the components to interact. Therefore, a selection based merely on dielectric constants or solubility parameters is hardly conclusive.     

一种简化的萃取溶剂分子设计方法

本研究提出一种新的萃取溶剂分子设计策略,首先以溶剂选择性为标准预选官能团,缩小分子设计的范围;再应用遗传算法对预选出的官能团进行组合,设计出符合要求的萃取溶剂分子。采用本设计的方法模拟计算了两个萃取溶剂设计实例,获得了令人满意的效果。     

有机溶剂中的酶催化反应

酶能在低水有机溶剂中起作用这一发现大大扩展了酶的应用范围。有机溶剂中的酶催化反应具有许多水中酶所没有的优势。本文强调了影响有机溶剂中酶的活性、稳定性和选择性的诸因素,概括了有机溶剂中酶的应用现状及前景。     

Solvent evaluation for desulfurization and denitrification of gas oil using performance and industrial usability indices

A new strategy for screening of solvents for sulfur, nitrogen, and aromatic compounds removal from gas oil is presented. This ranking is based on comparative assessment of solvents’ capacity, selectivity, performance, and newly defined industrial usability indices. Twenty eight solvents comprising of six most widely used industrially proven conventional solvents and 22 imidazolium‐based ionic liquids solvents were selected to illustrate the strategy. The solvents were ranked for removal of sulfur compounds namely benzothiophene, dibenzothiophene and their alkylated derivatives, and nitrogenous compounds namely quinoline, indole and carbazole from gas oil. Performance index (P_I) which combines the effect of both capacity and selectivity seems to be better index than individual capacity and selectivity indices to rank the solvents. Industrial usability index (S_IUI) of solvents which includes P_I and process complexity factor for solvent recovery section seems more practical and realistic criteria for solvent assessment. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2257–2267, 2015     

Solvent Effects on the Selectivity of Palladium-Catalyzed Suzuki-Miyaura Couplings

The use of polar solvents MeCN or dimethylformamide (DMF) was previously shown to induce a selectivity switch in the Pd/P^tBu₃-catalyzed Suzuki-Miyaura coupling of chloroaryl triflates. This phenomenon was attributed to the ability of polar solvents to stabilize anionic transition states for oxidative addition. However, we demonstrate that selectivity in this reaction does not trend with solvent dielectic constant. Unlike MeCN and DMF, water, alcohols, and several polar aprotic solvents such as MeNO₂, acetone, and propylene carbonate provide the same selectivity as nonpolar solvents. These results indicate that the role of solvent on the selectivity of Suzuki-Miyaura couplings may be more complex than previously envisioned. Furthermore, this observation has the potential for synthetic value as it greatly broadens the scope of solvents that can be used for chloride-selective cross coupling of chloroaryl triflates.     

Mechanistic insights into the selective hydrogenation of resorcinol to 1,3-cyclohexanedione over Pd/rGO catalyst through DFT calculation

In our previous work, graphene-supported Pd catalyst (Pd/rGO) exhibited higher activity and selectivity for the liquid phase selective hydrogenation of resorcinol to 1,3-cyclohexanedione compared with other catalysts. In the present study, further experimental and theoretical investigations were conducted to reveal the reaction mechanism and the catalytic mechanism of Pd/rGO for resorcinol hydrogenation. The effects of graphene nanosheet and the solvent on the reaction were investigated, and the pathway for resorcinol hydrogenation was proposed supported by density functional theory (DFT) calculations. The results showed that the excellent selectivity of Pd/rGO to 1,3-cyclohexanedione was attributed to the strong π–π and p–π interactions between the graphene nanosheet and the benzene ring as well as hydroxyl in resorcinol molecule, which was in agreement with our previous speculation. In weak polar aprotic solvents, solvation free energy had less impact to the π–π and p–π interactions mentioned above. In strong polar aprotic solvents and polar protic solvents, however, the influence of solvation free energy was much greater, which led to the decrease in the conversion of resorcinol and the selectivity to 1,3-cyclohexanedione.     

离子液体/低共熔溶剂在煤基液体分离中的应用

为了实现煤基液体各组分利用价值最大化,本文综述了离子液体和低共熔溶剂对组分组成复杂的煤基液体进行高效萃取分离的研究进展。首先介绍了离子液体和低共熔溶剂的性质及分类;其次根据分离目标的不同,将离子液体和低共熔溶剂对煤基液体典型组分的萃取分离分为四个方面进行阐述：煤基液体提酚、燃料油萃取脱硫、燃料油萃取脱氮、芳烃和脂肪烃的分离。分析表明,离子液体和低共熔溶剂对实际煤基液体的提酚效果较好,能分离出绝大多数的酚类化合物;燃料油萃取脱硫时,离子液体和低共熔溶剂对实际煤基液体的单次脱硫率均不高,需3～5次重复萃取后才能获得理想效果;燃料油中的碱性及非碱性含氮化合物很难被同一种离子液体或低共熔溶剂一次性分离出,导致实际油品的脱氮率较低;大多数离子液体和低共熔溶剂进行芳烃和脂肪烃的分离时不能获得理想的分配系数和选择性,尚无法用于实际芳烃和脂肪烃的分离。氢键、π-π、CH-π、范德华力等分子间相互作用的差异是实现离子液体或低共熔溶剂进行煤基液体典型组分分离的主要原因。依据分离对象,设计合适的离子液体和低共熔溶剂,提高实际煤基液体分离时的萃取率和选择性;分析并解决离子液体和低共熔溶剂用于实际煤基液体各组分分离时可能出现的问题,势必会推进煤基液体高值化分离的工业化进程。     

Solubility study for the purification of hydrogen from high pressure hydrocracker off-gas by an absorption-stripping process

Experiments were carried out to identify a solvent which has a high solubility and selectivity for methane relative to hydrogen at 295 K and pressures from 13.88 to 20.78 MPa. Binary solubilities with pure hydrogen and methane, and ternary solubilities with 73 mol% H₂ and 27 mol% CH₄ were measured at 295 K and for pressures from 6.99 to 20.78 MPa in various organic solvents. This gas mixture simulates hydrocracker and hydrotreater off-gases which are candidates for purification with an absorption-stripper. Of the solvents tested, 2,2,4-trimethylpentane (iso-octane), which showed very high methane solubility and a reasonable selectivity, and methylcyclohexane, which showed a very high selectivity and a reasonable solubility, are the best solvents for methane absorption. Correlations for hydrogen and methane as a function of pressure and solvent solubility parameter were developed with the experimental solubilities. Binary interaction parameters for Peng-Robinson (Peng and Robinson, 1976) and Soave-Redlich-Kwong (Soave, 1972) equations of state were calculated with experimental solubility results. Prediction of gas solubility in a ternary system was compared with experimental and found to be satisfactory when experimental binary interaction parameters were used.     

Liquid–liquid equilibrium extraction of ethanol with mixed solvent for bioethanol concentration

The extraction of ethanol with the solvents of aldehydes mixed with m-xylene was studied for the bioethanol concentration process.Furfural and benzaldehyde were selected as extraction solvents,with which the solubility of water is small,expecting large distribution coefficient of ethanol.The liquid–liquid two-phase region was the largest with m-xylene solvent,followed by benzaldehyde and furfural.The region of two liquid–liquid phase became larger with the mixed solvent of m-xylene and furfural than that with furfural solvent.The NRTL model was applied to the ethanol–water–furfural–m-xylene system,and the model could well express the liquid–liquid equilibrium of the system.For any solvent used in this study,the separation selectivity of ethanol relative to water decreased as the distribution coefficient of ethanol increased.The separation selectivity with m-xylene was the largest among the employed solvents,but the distribution coefficient was the smallest.The solvent mixture of furfural and m-xylene showed relatively high distribution coefficient of ethanol and separation selectivity,even in the higher mass fraction of m-xylene in the solvent phase.The ethanol extraction with a countercurrent multistage extractor by a continuous operation was simulated to evaluate the extraction performance.The ethanol content could be concentrated in the extract phase with relatively small number of extraction stages but low yield of ethanol was obtained.     

The use of environmentally sustainable bio-derived solvents in solvent extraction applications——A review

Replacement of volatile organic compounds (VOCs) by greener or more environmental y sustainable solvents is becoming increasingly important due to the increasing health and environmental concerns as wel as economic pressures associated with VOCs. Solvents that are derived from biomass, namely bio-derived solvents, are a type of green solvent that have attracted intensive investigations in recent years because of their advantages over con-ventional VOCs, such as low toxicity, biodegradability and renewability. This review aims to summarize the use of bio-derived solvents in solvent extraction applications, with special emphasis given to utilization of biodiesels and terpenes. Compared with the conventional VOCs, the overall performance of these bio-derived solvents is comparable in terms of extraction yields and selectivity for natural product extraction and no difference was found for metal extraction. To date most researchers have focused on laboratory scale thermodynamics studies. Future work is required to develop and test new bio-derived solvents and understand the kinetic performance as well as solvent extraction pilot plant studies.