Temperature-dependent solubility of Rebaudioside A in methanol/ethanol and ethyl acetate mixtures:Experimental measurements and thermodynamic modeling

The equilibrium solubility of Rebaudioside A(Reb A)FormⅡin binary mixtures of methanol/ethanol and ethyl acetate was quantitatively determined within the temperature range of 283.15—328.15 K at ambient pressure.The experimental findings indicate a positive correlation between the solubility of Reb A(FormⅡ)and both the temperature and the methanol/ethanol content in the solvent system.To describe the solubility data,six distinct models were employed:the modified Apelblat equation,theλh model,the combined nearly ideal binary solvent/Redlich—Kister(CNIBS/R—K)model,the van't HoffJouyban-Acree(VJA)model,the Apelblat-Jouyban-Acree(AJA)model,and the non-random two-liquid(NRTL)model.The combined nearly ideal binary solvent/Redlich—Kister model exhibited the most precise fit for solubility in methanol+ethyl acetate mixtures,reflected by an average relative deviation(ARD)of 0.0011 and a root mean square deviation(RMSD)of 12×10^(-7).Conversely,for ethanol+ethyl acetate mixtures,the modified Apelblat equation provided a superior correlation(ARD=0.0014,RMSD=4×10^(-7)).Furthermore,thermodynamic parameters associated with the dissolution of Reb A(FormⅡ),including enthalpy,entropy,and the Gibbs energy change,were inferred from the data.The findings underscore that the dissolution process is predominantly endothermic across the solvent systems examined.Notably,the entropy changes appear to have a significant influence on the Gibbs free energy associated with the dissolution of Reb A(FormⅡ),suggesting that entropic factors may play a pivotal role in the studied systems.

Hybridization of metal–organic framework and monodisperse spherical silica for chromatographic separation of xylene isomers

Metal–organic frameworks(MOFs) packed in the column have been a promising candidate as the stationary phase for high performance liquid chromatography(HPLC). However, the direct packing of irregular MOF powder could raise some problems like high back pressure and low column efficiency in the HPLC separation. In this work, UiO-66 capable of separating xylenes was supported effectively on the surface of the monodisperse spherical silica microspheres by one-pot method. The hybridization of Ui O-66 and silica microspheres(termed UiO-66@SiO2 shell–core composite) was prepared by stirring the suspension of the precursors of Ui O-66 and\\COOH terminated silica in the N,N-dimethylformamide with heating. The shell–core composite material UiO66@SiO2 was characterized by SEM, TEM, PXRD and FTIR. Then, it was used as a packing material for the chromatographic separation of xylene isomers. Xylene isomers including o-xylene, m-xylene and p-xylene were efficiently separated on the column with high resolution and good reproducibility. Moreover, the Ui O-66@SiO2 shell–core composites packed column still remained reverse shape selectivity as Ui O-66 possessed, and the retention of xylenes was probably ascribed to the hydrophobic effect between analytes and the aromatic rings of the Ui O-66 shell. The Ui O-66@SiO2 shell–core composites obtained in this study have some potential for the separation of structural isomers in HPLC.

Boosting xenon adsorption with record capacity in microporous carbon molecular sieves

Xenon/krypton(Xe/Kr)separation is an important task in industry,yet it remains challenging to develop adsorbents with high Xe/Kr selectivity and adsorption capacity of Xe,especially at low partial pressures.Herein,we report a series of microporous carbon molecular sieves(CMSs)for Xe/Kr separation.Those materials have ideal bimodal pore size distributions that not only provide substantial space for the accommodation of gas molecules,but also allow selective diffusion of gas molecules.Additionally,the carbon frameworks decorated with polar oxygen-containing functional groups afford higher affinity for Xe than Kr,which is proven by density functional theory(DFT)calculations and charge density difference analysis.The optimal CPVDC-700 exhibits a high selectivity of Xe/Kr and,more importantly,a record-high uptake of Xe(2.93 mmol g^(-1))at 0.2 bar and298 K,which is the highest among all the reported carbon adsorbents.Breakthrough experiments confirm the excellent performance of such CMSs for Xe/Kr separation,and the dynamic adsorption uptake of Xe and productivity of high-purity Kr are calculated to be 2.91 mmol g^(-1)and 208 m L g^(-1)(9.29 mmol g^(-1)),respectively,which also set up a new benchmark for Xe/Kr separation of carbon adsorbents.

Screening,preparation,and prototyping of metal–organic frameworks for adsorptive carbon capture under humid conditions

Adsorption-based carbon capture has been recognized as an attractive method for mitigating global warming.Metal–organic frameworks(MOFs)are promising candidate adsorbents for this purpose due to their high adsorption uptake and selectivity for carbon dioxide.However,in real-world applications,such as direct air capture,the presence of moisture in the feed gas may pose a grand challenge for CO_(2)adsorption in MOFs.This paper aims to address the issue of water–CO_(2)co-adsorption in MOFs and present screening criteria for selecting MOFs that preferentially adsorb CO_(2)under humid conditions.First,we uncover a comprehensive overview of CO_(2)–water co-adsorption characteristics of various MOFs.Then,the high-throughput screening methods are summarized.Both computational and experimental efforts have been dedicated to identify the promising MOFs for humid CO_(2)capture.According to the screening results and adsorption mechanism,the optimal preparation strategies are proposed tomodulate the effect of water on CO_(2)uptake in MOFs.Finally,current MOF-based CO_(2)capture prototypes are presented to evaluate their practical feasibility and performance.This work could offer valuable guidance for the development and application of MOFs for CO_(2)capture in the presence of water and inspire further research in this field.

离子液体萃取分离汽油富苯C6馏分中的苯和非苯组分

随着健康和环保越来越受到重视,各国家和地区对车用汽油中致癌物质苯的含量限制日益严格.催化裂化汽油是我国车用汽油的主要调和成分,也是其中苯的主要来源.催化裂化粗汽油总量大、苯含量低、烯烃含量高,直接脱苯难度较大;其C6馏分中苯含量提高且组成更简单,以此为原料进行脱苯有利于提高脱苯效率和经济性.本文以催化裂化汽油C6馏分降苯为目标,考察了离子液体结构(阳离子母核和取代基、阴离子)和温度对模型体系单级萃取脱苯效果的影响规律.在此基础上,比较了以1-乙基-3-甲基咪唑硫氰酸盐([EMIM][SCN])和环丁砜为萃取剂、多级逆流萃取中不同萃取剂/原料液流比和理论塔板数时模型体系脱苯的性能,结果表明离子液体具有替代常规有机溶剂进行催化裂化汽油脱苯的潜力.

羧酸功能化离子液体吸收分离丙炔/丙二烯/丙烯

丙炔/丙二烯/丙烯等C_(3)气体的分离是丙烯纯化过程中的关键环节.以离子液体为分离介质的吸收分离技术能够克服传统有机溶剂的缺点,有望应用于C_(3)气体的分离.本工作测定了C_(3)气体在强氢键碱性羧酸功能化离子液体中的溶解度,结果表明这类离子液体兼具高的丙炔、丙二烯吸收容量和丙炔/丙烯、丙二烯/丙烯选择性,其中[P_(4442)][C_(5)COO]在313.1 K下对丙炔摩尔吸收容量达到0.3 mol/mol,是目前已报道的最高值,同时丙二烯容量也达到0.14 mol/mol,明显高于丙烯吸收容量.不同长度阴离子和不同温度下的溶解度表明,阴离子碳链较短和温度较低时这类离子液体具有更好的丙炔/丙二烯/丙烯分离性能.吸收-解吸循环实验证明所使用的离子液体具备良好的循环再生性能.

Pd-Ni nanoparticles supported on titanium oxide as effective catalysts for Suzuki-Miyaura coupling reactions

We have successfully prepared a series of Pd- Ni/TiO2 catalysts by a one-step impregnation-reduction method. Among these catalysts with different compositions of Ni and Pd, the one with the Ni：Pd ratio of 2.95 showed the best activity. Small monodispersed Pd-Ni bimetallic nanoparticles were loaded on the surface of titanium oxide nanopowder as confirmed with TEM and EDS mapping. The XPS analysis demonstrated that Pd exists as 31% Pd（II） species and 69% Pd（0） species and all nickel is Ni（II）. The prepared Pd-Ni/TiO2 exhibited enhanced catalytic activity compared to an equal amount of Pd/TiO2 for Suzuki-Miyaura reactions together with excellent applicability and reusability.

Utilization of cationic microporous metal-organic framework for efficient Xe/Kr separation

The separation of xenon/krypton(Xe/Kr)mixtures plays a vital role in the industrial process of manufacturing high-purity xenon.Compared with energy-intensive cryogenic distillation,porous materials based on physical adsorption are very promising in the low-cost and energy-saving separation processes.Herein,we show that a cationic metal-organic framework(named as FJU-55)exhibits highly efficient Xe/Kr separation performance,which can be attributable to its uniform three-dimensional(3D)interconnection channels and the electro-positive features as the host framework.Moreover,FJU-55 demonstrates good Xe adsorption capacity of 1.41 mmol/g and excellent Xe/Kr selectivity of 10(298 K and 100 kPa),together with a high Qst value of 39.4 kJ/mol at low coverage area.The superior Xe/Kr separation performance of FJU-55 was further confirmed by the dynamic breakthrough experiments.Results obtained via molecular modeling studies have revealed that the suitable pore size and abundant accessible aromatic ligands in FJU-55 could offer strong multiple C–H∙∙∙Xe interactions,which play a collaborative role in this challenging gas separation task.

Room-temperature hydrogenation of halogenated nitrobenzenes over metal-organic-framework-derived ultra-dispersed Ni stabilized by N-doped carbon nanoneedles

Ultra-dispersed Ni nanoparticles(7.5 nm)on nitrogen-doped carbon nanoneedles(Ni@NCNs)were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines.Two different crystallization methods(stirring and static)were compared and the optimal pyrolysis temperature was explored.Ni@NCNs were systematically characterized by wide analytical techniques.In the hydrogenation of p-chloronitrobenzene,Ni@NCNs-600(pyrolyzed at 600°C)exhibited extraordinarily high performance with 77.9 h^(–1)catalytic productivity and>99%p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions(90°C,1.5 MPa H2),showing obvious superiority compared with reported Ni-based catalysts.Notably,the reaction smoothly proceeded at room temperature with full conversion and>99%selectivity.Moreover,Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups(halogen,nitrile,keto,carboxylic,etc.),and could be easily recycled by magnetic separation and reused for 5 times without deactivation.The adsorption tests showed that the preferential adsorption of–NO2 on the catalyst can restrain the dehalogenation of p-chloronitrobenzene,thus achieving high p-chloroaniline selectivity.While the high activity can be attributed to high Ni dispersion,special morphology,and rich pore structure of the catalyst.

Highly efficient and anti-poisoning single-atom cobalt catalyst for selective hydrogenation of nitroarenes

Developing non-precious metal catalysts to selectively reduce functionalized nitroarenes with high efficiency is urgently desirable for the production of value-added amines.Herein,we report a novel,efficient,anti-poisoning single-atom cobalt catalyst(Co-NAC)for the highly selective hydrogenation of the nitro to amino group for nitroarenes baring various functional groups,including vinyl,cyano,and halogen.Using a combination of structure characterization techniques,we have confirmed that the cobalt species are predominantly present in the form of four-coordinated Co single sites anchored on nitrogen-assembly carbon(NAC)as the ordered mesoporous support.Co-NAC catalysts enable the full conversion and>99%selectivity with molecular H2 as a green reductant under mild conditions(80℃,2 MPa H2).As for the selective hydrogenation of 3-nitrostyrene,Co-NAC catalyst affords high catalytic productivity(19.7 h-1),which is superior to the cobalt nanoparticles(NPs)catalysts and most of the recently reported Co-based catalysts.This is attributed to the highly accessible atomically-dispersed Co active sites,the high surface area with ordered-mesoporous morphology and the prominent high content of nitrogen dopants.Notably,Co-NAC catalyst displays resistance towards sulfur-containing poisons(20 equivalents)and strong non-oxidizing acid(8 M),showing great potential for continuous application in the chemical industry.

A robust ethane-trapping metal-organic framework for efficient purification of ethylene

Owing to the similar physicochemical properties between ethane(C_(2)H_(6))and ethylene(C_(2)H_(4)),obtaining polymerization-grade C_(2)H_(4)(≥99.95%pure)is still a tricky problem in the petrochemical industry.Here,we report a robust scandium-based metalorganic framework(Sc BPDC),which is connected by oxygen-rich phenyl ligand with exceptionally high thermal stability(up to873 K)and capacity of C_(2)H_(6)(4.94 mmol/g at 100 k Pa and 283 K),exhibiting superior separation performance of C_(2)H_(6)/C_(2)H_(4) mixture(the IAST selectivity is up to 1.7 at 283 K).Importantly,Sc BPDC can produce 8.96 L/kg C_(2)H_(4) with≥99.99%purity while the C_(2)H_(4)/C_(2)H_(6)(50:50,v/v)as the mixture injection and the low isosteric heat of Sc BPDC(16.4 k J/mol for C_(2)H_(6))validates the facility of adsorbent regeneration.Furthermore,theoretical calculations demonstrate the C_(2)H_(6) molecules are trapped in the nonpolar pore surface via C–H···πand C–H···O interactions between multiple hydrogen atoms of C_(2)H_(6) and the host framework.

Porous Hydrogen-Bonded Frameworks Assembled from Metal-Nucleobase Entities for Xe/Kr Separation

It is challenging to obtain high-purity xenon(Xe)and krypton(Kr)from the by-products of the air separation process due to their similar atom size and physical properties.Adsorption using porous materials such as metal–organic frameworks(MOFs)has been considered a promising technology to separate Xe/Kr.Herein,we report two novel isostructural ionic supramolecular MOFs(SMOFs;SMOF-PFSIX-1 and SMOF-AsFSIX-1),in which inorganic anions(PF_(6)^(−)or AsF_(6)^(−))and cationic metal–organic entities have self-assembled through hydrogen bonds to give three-dimensional pore channels.The two kinds of SMOFs can efficiently separate Xe/Kr with ideal adsorbed solution theory(IAST)selectivity values of 6.9 and 6.7 under 298 K and 1.0 bar,respectively.The breakthrough experiments further confirm their industrial application potential.The grand canonical Monte Carlo(GCMC)and density functional theory(DFT)calculations revealed that there are multiple adsorptive sites to capture the Xe atom,and the affinity between Xe and frameworks can be attributed to the inorganic anions and amino groups on the ligands.To the best of our knowledge,this was the first report of using SMOFs for Xe/Kr separation,and we proposed a new strategy for Xe/Kr separation based on the synergistic effect of amino and inorganic anions.

Hydrogen-bonded metal-nucleobase frameworks for highly selective capture of ethane/propane from methane and methane/nitrogen separation

The separation of light hydrocarbons,including C_(2)H_(6)and C_(3)H_(8),is essential to natural gas upgrading.Meanwhile,N_(2)removal from CH_(4)is also crucial to concentrating low-quality coalbed methane,but the adsorption process is challenging because of the close kinetic diameter.This work reports two hydrogen-bonded metal-nucleobase frameworks(HOF-ZJU-201 and HOF-ZJU202)capable of efficiently separating C_(3)H_(8)/CH_(4),C_(2)H_(6)/CH_(4),and CH_(4)/N_(2).Due to strong affinity for C_(3)H_(8)and C_(2)H_(6),the lowpressure capacity for C_(3)H_(8)(5 kPa)and C_(2)H_(6)(10 kPa)of HOF-ZJU-201a exceeds most adsorbents.The ideal adsorbed solution theory(IAST)selectivity of C_(3)H_(8)/CH_(4)and C_(2)H_(6)/CH_(4)is 119 and 45 at ambient conditions.According to density functional theory calculations,surface polarization environments formed by electron-rich anions and electron-deficient purine heterocyclic rings contribute to the selective capture of C_(3)H_(8)and C_(2)H_(6)with greater polarizability.Furthermore,the high CH_(4)adsorption capacity(1.73 mmol/g for HOF-ZJU-201a and 1.50 mmol/g for HOF-ZJU-202a at 298 K and 1.0 bar)and excellent CH_(4)/N_(2)selectivity(6.0 for HOF-ZJU-201 at 298 K),as well as dynamic breakthrough experiments of binary CH_(4)/N_(2)gas mixture implied their efficacy in the concentration of low-quality coalbed methane.