查看更多>>摘要：The synthesis of chabazite(CHA)aluminosilicate without organic structure-directing agent(OSDA)is a green process,but producing the CHA zeolite with excess acid sites,structural instability and limited applications due to a high aluminum content.Therefore,it is meaningful to develop an effective dealumination method to partially remove the framework aluminum atoms from the OSDA-free low-silica CHA zeolite.A novel stepwise dealumination and stabilization strategy through the subsequent treatment of A12(SO4)3,H2O,HN03 and NH4F was developed,which not only increased the Si/Al ratio from 2.4 to 5.0,but also stabilized the framework structure.Simultaneously,the removal of Al atoms optimized the acidity,introduced mesopores into the CHA framework and enhanced the diffusion property.Compared with low-silica CHA,the obtained high-silica CHA zeolite displayed attractive catalytic performance in methanol-to-olefin(MTO)reaction,showing a methanol conversion above 80% for more than 360 min with a maximum selectivity of 87% for low olefins(C2-C4).
查看更多>>摘要：Two covalent organic frameworks(COFs),as the supports of transition metal catalysts,were prepared and coordinated with nickel to synthesize two precatalysts for ethylene oligomerization.The chemical structure of sub-constructing unit had a significant influence on the specific surface area and the catalytic performance of covalent organic frameworks supported nickel(II)catalysts.Two COFs were stacked in lamellae,and the specific surface area and the pore volume of COF with p-phthalaldehyde as sub-constructing unit were far larger than those of COF with butanedione as sub-constructing unit.The catalyst with a larger specific surface area had a higher catalytic activity and a higher selectivity of low carbon olefins in ethylene oligomerization because of a higher specific surface areas and larger pore structure for ethylene diffusion and mass transfer.Two catalysts can be reused at least three times without considerable loss in the catalytic activity and the selectivity toward short-chain α-olefins.
查看更多>>摘要：Two-dimensional(2D)morphology zeolites nanosheets NS-M-SAPO-34(M = K and Sr)were developed and applied for producing ethylene(C2H4)from bioethanol.Various factors,including SAPO-34 type,temperature,bioethanol concentration,and weight hourly space velocity(WHSV)on C2H4 production were evaluated.The synthesized NS-M-SAPO-34s gave a nanosheet-like morphology with a thickness of 25-50 nm,while the commercial cube-like SAPO-34(CC-SP34)exhibited a cubic-like morphology with a particle size of about 1.5 μm.The specific surface area of the NS-Sr-SAPO-34 was 644 m~2 g~(-1)which was much larger than that of CC-SP34(573 m~2 g~(-1)).The catalytic performance evaluated by bioethanol dehydration reaction showed that NS-Sr-SAPO-34 exhibited significant improvements not only in suppressed coke deposition(5.6%)and prolonged lifetime(913 min)but also in higher C2H4 yield(94.5%)compared with those(11.8%,160 min and 82.4%,respectively)of CC-SP34,which can be attributed to the shortened diffusion path length,highly accessible active centers and suitable medium-strong acidity.Elevated temperature,high bioethanol concentration and decreased WHSV tended to enhance the C2H4 yield,while decreased bioethanol concentration was propitious to suppress coking rate.An optimal C2H4 yield of 100% was obtained at 350 ℃ with a bioethanol concentration from nutrient broths(15 vol%,WHSV = 0.75 h~(-1)).
查看更多>>摘要：An in-depth study of the thermal detemplation of the MCM-41 was carried out in a designed setup running with a high catalyst loading.Mapping the temperature along the catalyst bed during detemplation provides an understanding of the heat transfer phenomena involved under(an)aerobic conditions.Comparison between the results obtained at low(TG/DTA study)and high sample loadings(fixed-bed reactor)suggest that oxygen presence modifies the detemplation mechanism and high flows increase the local temperature in the bed due to the exothermic nature of hydrocarbon oxidation.Thermal cracking products detected during calcination may be considered a benchmark to deduce the local conditions in the catalyst bed.Despite the differences in detemplation processes,both environments lead to solids with similar structural properties.The use of advanced analytical techniques,such as 2D GC,led to the proposal of a detailed reaction scheme for the detemplation step.
查看更多>>摘要：A new FG-g-AM-cl-MBA-MnO2 hydrogel has been synthesised via a free radical cross-linking reaction using fenugreek gum containing macromolecular galactomannan units,acrylamide,N,N'-methylenebisacrylamide,potassium persulfate,and MnO2 for removal of methylene blue and malachite green dyes from water.Surface morphology of synthesised hydrogel was porous and rough as determined by FESEM.The presence of functional groups and cross-linking mechanism were validated by FTIR spectroscopy.TGA revealed that FG-g-AM-cl-MBA-MnO2 hydrogel is thermally stable up to 700 ℃ and mass ratio of MnO2 was found to be 25.9%.BET technique gave surface area as 5.59 m~2/g with a pore radius of 3.654 nm.The swelling ratio of FG-g-AM-cl-MBA-MnO2 hydrogel was 1862% at 313 K.To evaluate the influence of adsorbent dose,contact time,temperature,pH,and dye concentration on adsorption behaviour of hydrogel several batch experiments were conducted.The hydrogel preferentially removes MG(98.5%)and MB(96.3%)effectively following Langmuir model with 526.31 and 483.09 mg/g adsorption capacity,respectively.The adsorption process followed pseudo-second-order kinetics and thermodynamics study revealed that process is endothermic and spontaneous.The hydrogel retained more than 85% adsorption capacity even after ten cycles of dye adsorption-desorption process and thus,serves as a proficient,reusable,and eco-friendly adsorbent for wastewater remediation.
查看更多>>摘要：Creatinine(Cre)measurement in biological fluids is an increasingly important clinical measure for evaluating renal insufficiency,thyroid dysfunction,and muscle injury.Therefore,a simple,fast,and reliable Cre analysis method is of great significance to human health.Herein,a novel ratiometric fluorescence sensor,Ag-Eu-MOF-808-EDTA,was synthesized by introducing ethylenediaminetetraacetic acid(EDTA),Ag~+,and Eu~(3+)into the framework of MOF-808 through three steps of post-synthesis modification,and was used to detect Cre in PBS buffer of pH 7.2 at 35 ℃ with a"turn-on"ratio response in the presence of various interfering ions and several biomolecules.In this strategy,the characteristic emission of Eu~(3+)at 551 nm can be turned on due to coordination between Cre and Ag~+,while emission at 613 nm is independent of Cre,which produces a significant ratio response change throughout the cycle.Experimental results showed that the ratio fluorescence sensor displayed a wide linear range for Cre from 0.5 to 350 μM with a low detection limit of 0.42 μM.Finally,a good recovery rate(96.7-102.9%)and appropriate relative standard deviation(RSD<2.39%,n = 3)were obtained during the determination of creatinine in real urine and serum.This work provides additional insights into the detection of creatinine in clinical blood samples.
查看更多>>摘要：In this article,we presented a novel and facile method for obtaining a phthalocyanine network polymer via"Thiol-Ene Click"chemistry.A series of metallophthalocyanine-based covalently cross-linked polymers(MTUPc-CCPs,M = Zn,Cu and Co)containing hydrophilic sulfur-containing flexible chain were synthesized successfully,the MTUPc-CCPs had micropores and mesopores coexistence structure and remarkable efficiency for organic dye pollutants and Cr(VI)removal from wastewater.The photocatalytic efficiency of MTUPc-CCPs was significantly improved compared with the corresponding phthalocyanine monomers.Thereinto,ZnTUPc-CCP had the most excellent photocatalytic performances for Methyl orange(MO),Rhodamine B(RhB)degradation and Cr(VI)reduction(3 h,95.4%,93.2% and 100%)under visible-light irradiation.These obtained results can be attributed to the wide spectral response,larger surface area and higher micropore ratio of ZnTUPc-CCP.ZnTUPc-CCP was reused for three consecutive cycles without significant loss of activity or structural changes.Furthermore,active species trapping experiments confirmed the crucial role of O_2~(·-),~1O_2 and OH~·/e~-during photocatalytic degradation/reduction,upon which a possible photocatalytic mechanism was proposed.Above all,ZnTUPc-CCP was a promising potential visible-light photocatalyst on the degradation of complex contaminants.
查看更多>>摘要：Recent industrial development raised a great concern for human health and environmental protection due to the generation of toxic wastewater.The present study aims to prepare a new low-cost bio-based adsorbent for the effective simultaneous removal of anionic dye and toxic metal.Porous cellulose acetate(CA)microspheres were synthesized using a double emulsion(W/0/W)-solvents evaporation technique then modified using 3-aminopropyltriethoxysilane(APTES-CA).SEM,FTIR and XRD results emphasized the successful preparation of APTES-CA microspheres with average diameter size around 380-430 urn.Porosity analysis announced the mesoporous structure of the CA microspheres and the meso-microporous structure of APTES-CA microspheres.Also,EDX elemental analysis confirmed the presence of Si and N of APTES indicating the successful modification of CA surface.Further to this,the adsorption study showed that APTES modification improved the adsorption efficacy toward RBI9 and Pb~(2+).Where,in unary solution,almost complete removal of 10 mg/L Pb~(2+)was achieved using 1.00 g/L of APTES-CA after 30 min at pH0 5.On the other hand,91% of 20 mg/L RB19 preadjusted to pH0 2 can be removed by 1.00 g/L of APTES-CA after 90 min.The kinetic study indicated that APTES-CA adsorbs RB19 and Pb~(2+)via different mechanisms,specifically,chemisorption for RBI9 and physisorption for Pb~(2+).The theoretical Langmuir monolayer saturation capacity(180 mg/g)manifested a good efficiency of APTES-CA towards Pb~(2+).In the binary solution,Pb~(2+)does not affect RB19 adsorption while RB19 retards Pb~(2+)adsorption.
NSTL