Boosting kinetic separation of ethylene and ethane on microporous materials via crystal size control

The adsorptive separation of C_(2)H_(4)and C_(2)H_(6),as an alternative to distillation units consuming high energy,is a promising yet challenging research.The great similarity in the molecular size of C_(2)H_(4)and C_(2)H_(6)brings challenges to the regulation of adsorbents to realize efficient dynamic separation.Herein,we reported the enhancement of the kinetic separation of C_(2)H_(4)/C_(2)H_(6)by controlling the crystal size of ZnAtzPO_(4)(Atz=3-amino-1,2,4-triazole)to amplify the diffusion difference of C_(2)H_(4)and C_(2)H_(6).Through adjusting the synthesis temperature,reactant concentration,and ligands/metal ions molar ratio,ZnAtzPO4 crystals with different sizes were obtained.Both single-component kinetic adsorption tests and binary-component dynamic breakthrough experiments confirmed the enhancement of the dynamic separation of C_(2)H_(4)/C_(2)H_(6)with the increase in the crystal size of ZnAtzPO_(4).The separation selectivity of C_(2)H_(4)/C_(2)H_(6)increased from 1.3 to 98.5 with the increase in the crystal size of ZnAtzPO_(4).This work demonstrated the role of morphology and size control of adsorbent crystals in the improvement of the C_(2)H_(4)/C_(2)H_(6)kinetic separation performance.

Mixing of miscible shear-thinning fluids in a lid-driven cavity

The concentration and velocity fields of two refractive index matched miscible shear-thinning fluids in a lid-driven cavity were investigated by using planar laser-induced fluorescence and particle image velocimetry,as well by computational fluid dynamics.Quantitative analyses show that the results obtained by flow simulations with the species transport model are in good agreement with the experimental results.The effects of different parameters were studied by using the intensity of segregation.For two fluids with the same rheological parameters,the relative amounts of liquids H_(1)/H and the power-law index n dominate the mixing process while the Reynolds number Re plays a marginal role.As for two fluids with density difference,buoyancy has significant influence on the mixing process.The dimensionless group Ar/Re(redefined such as to include shear thinning behavior)is proposed for assessing the effect of buoyancy and rheological properties on the mixing of miscible shear-thinning fluids.

Experimental results for the vapor-liquid equilibria of 0(formaldehyde+1,3,5-trioxane+methanol+salt+water)systems and comparison with predictions

The salt effect on the vaporliquid phase equilibrium(VLE)of solvent mixtures is of significant interest in the industrial production of 1,3,5trioxane.Experimental data for the VLE of quinary systems(formaldehyde+1,3,5trioxane+methanol+salt+water)and their ternary subsystems(formaldehyde+salt+water),(1,3,5trioxane+salt+water),and(methanol+salt+water)were systematic measured under atmospheric pressure.The salts considered included KBr,NaNO_(3),and CaCl_(2).The extended UNIFAC model was used to describe the VLE of the saltcontaining reactive mixtures.The model parameters were determined from the experimental VLE data of ternary systems or obtained from the literature,and then were used to predict the VLE of systems(1,3,5trioxane+KBr+water),(methanol+KBr+water),(formaldehyde+KBr+water),and(formaldehyde+1,3,5trioxane+methanol+salt+water)with salt=KBr,NaNO_(3),and CaCl_(2).The predicted results showed good agreements with the measured results.Furthermore,the model was used to uncover the salt effect on the VLE of these multisolvent reactive systems.

Effects of internals on phase holdup and backmixing in a slightly-expanded-bed reactor with gas–liquid concurrent upflow

Five different internals were designed,and their effects on phase holdup and backmixing were investigated in a gas–liquid concurrent upflow reactor where the spherical alumina packing particles of three diameters(3.0,4.5 and6.0 mm)were slightly expanded under the conditions of varied superficial gas velocities(6.77×10-2-3.61×10-1 m·s-1)and superficial liquid velocities(9.47×10-4-2.17×10-3 m·s-1).The experimental results show that the gas holdup increases with the superficial gas velocity and particle size,opposite to the variational trend of liquid holdup.When an internal component is installed amid the upflow reactor,a higher gas holdup,a less liquid holdup and a larger Peclet number characterizing the weaker backmixing are obtained compared to those in the bed without internals under the same operating conditions.Additionally,the minimal backmixing is observed in the reactor equipped with the internals with a novel multi-step design.Finally,empirical correlations were proposed for estimating gas holdup,liquid holdup and Peclet number with the relative deviations within 11%,12%and 25%,respectively.

Catalyst design strategy toward the efficient heterogeneously-catalyzed selective oxidation of 5-hydroxymethylfurfural

The selective oxidation of 5-hydroxymethylfurfural(HMF),a versatile bio-based platform molecule,leads to the formation of several intriguing and useful downstream chemicals,such as 2,5-diformylfuran(DFF),5-hydroxymethyl-2-furancarboxylic acid(HMFCA),formyl 2-furancarboxylic acid(FFCA),2,5-furandicarboxylic acid(FDCA) and furan-2,5-dimethylcarboxylate(FDMC).These products have been extensively employed to fabricate novel polymers,pharmaceuticals,sustainable dyes and many other value-added fine chemicals.The heart of the developed HMF oxidation processes is always the catalyst.In this regard,this review comprehensively summarized the established heterogeneous catalyst design strategy for the selective oxidation of HMF via thermo-catalysis.Particular attention has been focused on the reaction mechanism of HMF oxidation over different catalysts as well as enhancing the catalytic performance of the catalyst through manipulating the properties of the support and fabricating of multi-component metal nano-particles and oxides.The current challenges and possible research directions for the catalytic oxidation of HMF in the future are also discussed.

Metal vacancy-enriched layered double hydroxide for biomass molecule electrooxidation coupled with hydrogen production

The electrochemical oxidation of biomass molecules coupling with hydrogen production is a promising strategy to obtain both green energy and value-added chemicals;however,this strategy is limited by the competing oxygen evolution reactions and high energy consumption.Herein,we report a hierarchical CoNi layered double hydroxides(LDHs)electrocatalyst with abundant Ni vacancies for the efficient anodic oxidation of 5-hydroxymethylfurfural(HMF)and cathodic hydrogen evolution.The unique hierarchical nanosheet structure and Ni vacancies provide outstanding activity and selectivity toward several biomass molecules because of the finely regulated electronic structure and highly-exposed active sites.In particular,a high faradaic efficiency(FE)at a high current density(99%at 100 mA cm^(-2))is achieved for HMF oxidation,and a two-electrode electrolyzer is assembled based on the Ni vacancies-enriched LDH,which realized a continuous synthesis of highly-pure 2,5-furandicarboxylic acid products with high yields(95%)and FE(90%).

Mechanism study on direct synthesis of glycerol carbonate from CO_(2)and glycerol over shaped CeO_(2)model catalysts

Direct synthesis of glycerol carbonate(GC)from CO_(2)and glycerol(a byproduct of biodiesel production)is a route to obtain a high-value chemical from waste and low-cost byproducts but has not yet industrialized due to the lack of efficient catalysts.Ceria(CeO_(2))exhibits the highest catalytic activity and GC selectivity among the heterogeneous catalysts studied so far.However,the mechanism of this reaction over CeO_(2)catalysts has not been studied in detail.Herein,we synthesized CeO_(2)nanocrystals with different morphologies as model catalysts that can predominantly expose(111),(110),and(100)facets,and their surface acid-base properties were characterized using high-sensitivity temperature-programmed desorption of NH3 and CO_(2)with quadrupole mass spectrometry as detector(NH3-TPD-QMS and CO_(2)-TPD-QMS).We found that the catalytic performance(GC formation rate)is strictly linearly dependent on the density of basic sites,which is relevant to the adsorption and activation of CO_(2).In addition,to illustrate a more microscopic reaction mechanisms underlying the formation of GC from CO_(2)and glycerol on all three low-index surfaces(111),(110)and(100),we also performed comprehensive first principles calculations.A three-step Langmuir-Hinshelwood(LH)mechanism was identified in which the annulation reaction is the rate-limiting step.The CeO_(2)(11)surface exhibits the lowest overall activation energy,which agrees well with the catalytic performance that the CeO_(2)nano-octahedra,predominantly exposing(111)facets,have the highest GC formation rate.This work is the first to combine experiments on shaped CeO_(2)model catalysts with first-principles calculations to gain insight into the mechanism of direct synthesis of GC from CO_(2)and glycerol,and will aid in the development of catalysts with improved performance.

Phase Morphology, Crystallization Behavior and Mechanical Properties of Poly(L-lactide) Toughened with Biodegradable Polyurethane: Effect of Composition and Hard Segment Ratio

Polyester-based biodegradable polyurethane(PU) with different hard segment ratios was selected to modify the impact toughness of poly(L-lactide)(PLLA). The influence of blending composition and hard segment ratio of PU on the phase morphology, crystallization behavior and mechanical properties of PLLA/PU blends has been investigated systematically. The results showed that the PU particles were uniformly dispersed in PLLA matrix at a scale from submicrons to several microns. The glass transition temperature of PU within these blends decreased compared to that of neat PU, but rose slightly with its content and hard segment ratio. The presence of PU retarded the crystallization ability of PLLA, whereas enhanced its elongation at break and impact resistance effectively. As the PU content reaches up to 30 wt%, the phenomenon of brittle-ductile transition occurred, resulting in a rougher fracture surface with the formation of fibril-like structure. Moreover, under the same concentrations, the elongation at break and impact strength of PLLA blends decreased slightly with the increase of hard segment ratio of PU.

Comparative Investigation on Step-cycle Tensile Behaviors of Two Bimodal Pipe-grade Polyethylene with Different Slow Crack Growth Resistance

In this work,step-cycle tensile behavior of two bimodal polyethylene(PE)materials,a PEI 00 grade pipe material,XS10,and a PEI 00-RC(Resistant Crack)grade pipe material,XSC50,was comparatively investigated.By decomposing the strain into a recoverable part and an unrecoverable part,it was found that the deformation recovery capability of XSC50 during stretching was larger than that of XS10.Structural evolution characterized by in situ synchrotron small angle X-ray scattering indicated that the fragmentation of initial crystals in XSC50 occurred at lower strain than in XS10.Considering that XSC50 had relatively small lamellar thickness and similar crystallinity to XS10,we speculated that the larger deformation recovery capability of XSC50 during stretching probably derived from stronger entangled amorphous region caused by larger density of tie molecules and entanglements,which were usually regarded to have a significant influence on the slow crack growth(SCG)resistance of PE materials.As expected,the experimental result of strain hardening modulus test suggested that the deformation recovery capability during stretching was positively correlated with the SCG resistance for XS10 and XSC50 used in this work.The step-cycle tensile test had the potential to be developed into a supplement for comparison of SCG resistance of PE materials.

Nickel-catalyzed C-N crossing coupling reaction: The synthetic method for N-aryl substituted indenoindole

A nickel-based catalyst was employed for the first time in the crossing-coupling of indenoindoles with bromo-/iodoarenes. A simple and practical method was provided for the synthesis of N-aryl substituted indenoindole and the mechanism of this reaction was discussed.

Crystal phase engineering of electrocatalysts for energy conversions

Crystal phase is an intrinsic structural parameter to determine the physicochemical properties and functionalities of materials.The unconventional phases of materials with distinct atomic arrangements from their thermodynamically stable phases have attracted enormous attention.Phase engineering has recently made fruitful achievements in electrocatalysis field to optimize the performance of various electrochemical reactions.In this review,theoretical and experimental advances made in phase engineering of electrocatalysts are summarized.First,we introduce basic understanding on crystal phases of catalysts to show the dialectical relationship between bulk phase and surface catalytic layer,and highlight the multiple functions of phase engineering in catalysis studies.We then describe phase-controlled synthesis of materials through various experimental methods such as wet-chemical method,phase transition,and template growth.As a focus,we discuss the wide usage of phase engineering strategy in different kinds of electrocatalytic materials,and particular emphasis is given to establishment of reasonable crystal phase-activity relationship.Finally,we propose several future directions for developing more desirable electrocatalysts by rational crystal phase design.

Investigating the Nucleation Effect of DMDBS on Syndiotactic Polypropylene from the Perspective of Chain Conformation

The mechanism of nucleating agents(NAs)accelerating the crystallization of semi-crystlline polymers has received continuous attention due to the extreme importance in academic research and industry application.In this work,the nucleation effect and probable mechanism of 1,3.2,4 bis(3,4-dimethylbenzylidene)sorbitol(DMDBS)on promoting the crystallization of syndiotactic polypropylene(sPP)was systematically investigated.Our results showed that DMDBS could significantly accelerate the crystallization process and did not change the crystalline form of sPP.The in situ infrred spectra recorded in the crystallization process showed that in pristine sPP the tttt conformers decreased and the tgg conformers increased subsequently.In sPP/DMDBS system,DMDBS could promote the increase of tgg conformers rather than the decrease of tttt conformers.The further analysis by 2D-IR spectra revealed that ttgg conformers increased prior to the decrease of tttt conformers in the sPP/DMDBS system comparing with pristine sPP.Considering that ttgg conformers were basic elements of helical conformation of Form I crystal for sPP,we proposed a probable nucleation mechanism of DMDBS for sPP:DMDBS could stabilize the ttgg conformers which induced these ttgg conformers to pre-orientate and aggregate into helical conformation sequences as initial nuclei quickly and early to promote the sPP crystallization.Our work provides some new insights into the nucleation mechanism of NAs for sPP.

Novel Designed PEG-Dicationic Imidazolium-Based Ionic Liquids as Effective Plasticizers for Sustainable Polylactide

A series of novel polyethylene glycol-dicationic imidazolium-based ionic liquids(mPEG-ILs)were synthesized by facile quaternization reaction from various elaborately designed di-imidazoles and PEG,which were then studied as green plasticizers for sustainable polylactide(PLA)material.

Intrinsic emission and tunable phosphorescence of perfluorosulfonate ionomers with evolved ionic clusters

Intrinsic emission from unorthodox luminogens without traditional conjugated building blocks is drawing increasing attention.However,the emission mechanism is still controversial.Herein,we demonstrate the intriguing emission from perfluorosulfonate ionomers(PFSIs),which can be explained by the clustering triggered emission(CTE)mechanism.Despite being free of any conventional chromophores,PFSIs exhibit bright emission and multi-color phosphorescence(77 K)in concentrated solutions,powders and membranes with obvious aggregation-induced emission(AIE)characteristics.Clustered sulfonic acids are responsible for the light emission,and their connection and evolution are deeply explored via X-ray diffraction(XRD)and small angel X-ray scattering(SAXS),in which the electron overlap determined by the clustered status results in the extended conjugation and simultaneously rigidified conformations.These results demonstrate that it is feasible to use fluorescence analysis to explore the ionic cluster structure and evolution of PFSI,and it can be applied in the pure organic luminescent field as well.

吩嗪类衍生物用于快速充放电和长寿命的水系钾离子全电池负极

有机电极材料因具有结构多样性和可持续性,在水系钾离子电池研究领域展示出广阔的前景,但它们大多数存在导电性差、易溶于电解液的问题,导致电极活性物质利用率低、循环稳定性差.本文通过含氮苯环的共轭延申、引入氰基活性中心,获得了3CN-HATN.与经#吩嗪负极相比,3CN-HATN的最低未占据分子轨道能级更低,更容易被还原,且其能带隙较窄,改善了导电性,其共轭结构可有效抑制循环过程中3CN-HATN的溶解.3CN-HATN负极在80 C(1 C=350 mA g^(-1))下比容量高达233.8 mA h g^(-1),将其与Ni(OH)_(2)正极匹配,构建的水系钾离子全电池具备优异的循环稳定性和快充性能,30 C下循环10,000圈后容量保持率达81.5%.