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1.
High‐performance ZSM‐5 membranes with a low Si/Al ratio of 10.3 were prepared on cheap coarse macroporous α‐Al2O3 tubes by fluoride route without organic template. The effects of crystallization time and aluminum source on the growth, morphology and pervaporation (PV) performances of the as‐synthesized membranes were investigated. The feasibility of preparing ZSM‐5 membranes with different Si/Al ratio which was implemented by using different Al2(SO4)3·18H2O content in synthesis gel were discussed. It was found that the aluminum source had significant effect on the synthesis of membranes. The ZSM‐5 membranes prepared by using Al2(SO4)3·18H2O as an aluminum source from synthetic gel with composition of 1SiO2/0.05Al2O3/0.17Na2O/0.9NaF/45H2O showed high reproducibility and high PV performance with flux of 3.85 kg/(m2·h) and separation factor of higher than 10,000 in dehydration of 90 wt % i‐PrOH/H2O at 348 K. Moreover, the ZSM‐5 membranes exhibited high water perm‐selectivity performance for dehydration of 90 wt % n‐PrOH/H2O, n‐BtOH/H2O, and i‐BtOH/H2O mixtures, respectively. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2813–2824, 2016  相似文献   

2.
In this work, we are reporting for the first time the synthesis of hierarchical micro‐ and mesoporous zeolite using silica–carbon (SiO2/C) composites prepared by pyrolysis of carbonaceous gases in the presence of silica gel. The pyrolysis effectively yielded carbon deposited onto the raw silica material. The obtained SiO2/C composites were utilised as a bifunctional material, mesoporous template and silica source, for the zeolite synthesis. Tetrapropylammonium hydroxide (TPAOH) was used as a microporous template. The combination of the obtained composites and the TPAOH for the hydrothermal synthesis resulted in the formation of hierarchical micro‐ and mesoporous ZSM‐5. The results from the SEM, TEM, and N2 adsorption/desorption isotherms, and 27Al MAS NMR characterisations of the synthesised samples obtained after the removal of the templates confirmed the successful formation of the micro‐ and mesoporous zeolites. The mesoporosity of the zeolites could be controlled by adjusting the carbon content in the SiO2/C composites while the carbon content could be controlled by varying the deposition time and the concentration of the carbonaceous gases used. This controllable and efficient synthesis method is considered to be a promising method for creating hierarchical micro‐ and mesoporous zeolites. © 2011 Canadian Society for Chemical Engineering  相似文献   

3.
Boron‐substituted MFI (B‐ZSM‐5) zeolite membranes with high pervaporation (PV) performance were prepared onto seeded inexpensive macroporous α‐Al2O3 supports from dilute solution and explored for the separation of ethanol/water mixtures by PV. The effects of several parameters on microstructures and PV performance of the B‐ZSM‐5 membranes were examined systematically, including the seed size, synthesis temperature, crystallization time, B/Si ratio, H2O/SiO2 ratio and silica source. A continuous and compact B‐ZSM‐5 membrane was fabricated from solution containing 1 tetraethyl orthosilicate/0.2 tetrapropylammonium hydroxide/0.06 boric acid/600 H2O at 448 K for 24 h, showing a separation factor of 55 and a flux of 2.6 kg/m2 h along with high reproducibility for a 5 wt % ethanol/water mixture at 333 K. It was demonstrated that the incorporation of boron into mobile five (MFI) structure could increase the hydrophobicity of B‐ZSM‐5 membrane evidenced by the improved contact angle and amount of the adsorbed ethanol, and thus enhance the PV property for ethanol/water mixtures. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2447–2458, 2016  相似文献   

4.
A novel chelating resin with functional group containing S and N atoms was prepared using chloromethylated polystyrene and 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT) as materials. Its structure was characterized by infrared spectra and elementary analysis. The results showed that the content of the functional group was 2.07 mmol BMT g?1 resin, 47% of which were in the form of monosubstitution (PS‐BMT‐1) and 53% in the form of double substitution (PS‐BMT‐2). The adsorption for mercury ion was investigated. The adsorption dynamics showed that the adsorption was controlled by liquid film diffusion. Increasing the temperature was beneficial to adsorption. The Langmuir model was much better than the Freundlich model to describe the isothermal process. The adsorption activation energy (Ea), ΔG, ΔH, and ΔS values calculated were 18.56 kJ·mol?1, ‐5.99 kJ·mol?1, 16.38 kJ·mol?1, and 37.36, J·mol?1·K?1, respectively. The chelating resin could be easily regenerated by 2% thiourea in 0.1 mol·L?1 HCl with higher effectiveness. Five adsorption–desorption cycles demonstrated that this resin was suitable for repeated use without considerable change in adsorption capacity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1646–1652, 2004  相似文献   

5.
Rare‐earth (RE) monosilicates are promising candidates as environmental barrier coating (EBC) materials for ceramic matrix composites for aerospace applications. Five rare‐earth monosilicate materials have been investigated: Y2SiO5, Gd2SiO5, Er2SiO5, Yb2SiO5, and Lu2SiO5 produced from RE oxides and silica starting materials pressed and sintered at 1580°C under flowing air. Relative densities above 94% were obtained for all samples and ceramics were made containing 85–100 wt% of the RE monosilicate according to X‐ray diffraction (XRD) with RE disilicates as the second phase in the Gd, Yb, and Lu silicate systems. Microstructures were characterized using scanning electron microscopy and XRD, and thermal properties measured including specific heat, thermal expansion, and thermal diffusivity. For the first time, specific heat capacity values are reported for the monosilicates [0.45–0.69 J·(g·K)?1]. Thermal expansion coefficients (TECs) of the dense samples ranged between 5.9 and 10.3 × 10?6 K?1 measured for 473 to 1473 K. All EBCs have low thermal conductivities [1.8 W·(m·K)?1 or less] making them excellent EBC insulators.  相似文献   

6.
The catalytic performance of bimetallic chromium–copper supported over untreated ZSM‐5 (Cr? Cu/Z), ZSM‐5 treated with silicon tetrachloride (Cr–Cu/SiCl4‐Z) and ZSM‐5 treated with steam (Cr–Cu/H2O‐Z) is reported. The activity is based on the combustion of ethyl ethanoate and benzene at a feed concentration of 2000 ppm and a gas hourly space velocity (GHSV) of 32 000 h?1. Due to higher reactivity and larger molecular size compared with that of water molecules, SiCl4 reacted at the external surface of ZSM‐5 crystals. Cr–Cu/SiCl4‐Z and Cr–Cu/H2O‐Z both gave slightly lower conversion and carbon dioxide yield compared with Cr–Cu/Z. This was attributed to larger active metal crystallites formed in the mesopores and narrowing pore mouth and pore intersection by extraframework species. Cr–Cu/SiCl4‐Z and Cr–Cu/H2O‐Z both had reduced concentration and strength of acid sites, thus making them less susceptible to deactivation by coking. The coke accumulated by these two catalysts was relatively softer and more easily decomposed in oxygen during catalyst regeneration. Copyright © 2004 Society of Chemical Industry  相似文献   

7.
Tomography, an efficient nonintrusive technique, was employed to visualize the flow in continuous‐flow mixing and to measure the cavern volume (Vc) in batch mixing. This study has demonstrated an efficient method for flow visualization in the continuous‐flow mixing of opaque fluids using two‐dimensional (2‐D) and 3‐D tomograms. The main objective of this study was to explore the effects of four inlet‐outlet configurations, fluid rheology (0.5–1.5% xanthan gum concentration), high‐velocity jet (0.317–1.660 m s?1), and feed flow rate (5.3 × 10?5?2.36 × 10?4 m3 s?1) on the deformation of the cavern. Dynamic tests were also performed to estimate the fully mixed volume (Vfully mixed) for the RT, A310, and 3AM impellers in a continuous‐flow mixing system, and it was found that Vfully mixed was greater than Vc. Incorporating the findings of this study into the design criteria will minimize the extent of nonideal flows in the continuous‐flow mixing of complex fluids and eventually improve the quality of end‐products. © 2013 American Institute of Chemical Engineers AIChE J, 60: 315–331, 2014  相似文献   

8.
In this study, various polypropylene (PP) nanocomposites were prepared by melt blending method. The effects of different spherical nanofillers, such as 50 nm CaCO3 and 20 nm SiO2, on the linear viscoelastic property, crystallization behavior, morphology and mechanical property of the resulting PP nanocomposites were examined. Rheological study indicated that coincorporation of nano‐SiO2 and nano‐CaCO3 favored the uniform dispersion of nanoparticles in the PP matrix. Differential scanning calorimeter (DSC) and polarizing optical microscopy (POM) studies revealed that the coincorporation of SiO2 and CaCO3 nanoparticles could effectively improve PP crystallizability, which gave rise to a lower supercooling temperature (ΔT), a shorter crystallization half‐life (t1/2) and a smaller spherulite size in comparison with those nanocomposites incorporating only one type of CaCO3 or SiO2 nanoparticles. The mechanical analysis results also showed that addition of two types of nanoparticles into PP matrix gave rise to enhanced performance than the nanocomposites containing CaCO3 or SiO2 individually. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

9.
In this article, preparation of novel MgCl2‐adduct supported spherical Ziegler–Natta catalyst for α‐olefin polymerization is reported. The factors affecting the particle size (PS) and particle size distribution (PSD) of the prepared support were investigated. In this method, the internal donor added while preparing MgCl2‐adduct support was supposed to act as a crosslinking agent. Therefore it provided a reasonable way to enhance the morphology and control the PS of the resultant polymer particles. The possible mechanism is discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 945–948, 2006  相似文献   

10.
Polyimides (PIs) as high‐performance organic matrices are used in the preparation of PI composites because of their excellent mechanical, thermal and dielectric properties. The sol–gel method is a promising technique for preparing these PI composites due to the mild reaction conditions and the process being controllable. Although sulfonated polyimide (SPI) proton‐exchange membranes have attracted much attention recently, studies on preparing SPI‐based hybrid proton‐exchange membranes for fuel cells have been rare. A series of SPI? SiO2 hybrid proton‐exchange membranes were prepared from amino‐terminated SPI pre‐polymers, 3‐glycidoxypropyltrimethoxysilane (KH‐560) and tetraethylorthosilicate through a co‐hydrolysis and condensation process using an in situ sol–gel method. The reactive silane KH‐560 was used to react with amino‐terminated SPI to form silane‐capped SPI in order to improve the compatibility between the polymer matrix and the inorganic SiO2 phase. The microstructure and mechanical, thermal and proton conduction properties were studied in detail. The hybrid membranes were highly uniform without phase separation up to 30 wt% SiO2. The storage modulus and tensile strength of the hybrid membranes increased with increasing SiO2 content. The introduction of SiO2 improved the methanol resistance while retaining good proton conductivity. The hybrid membrane with 30 wt% SiO2 exhibited a proton conductivity of 10.57 mS cm?1 at 80 °C and methanol permeability of 2.3 × 10?6 cm2 s?1 possibly because the crosslinking structure and SiO2 phases formed in the hybrids could retain water and were helpful to proton transport. Copyright © 2010 Society of Chemical Industry  相似文献   

11.
A new chitosan molecular imprinted adsorbent obtained by immobilization of nano‐TiO2 on the adsorbent surface (surface‐imprinted adsorbent with nano‐TiO2) was prepared. Based on photocatalytic reaction and the surface molecular imprinting technology, this new kind of surface‐imprinted adsorbent with immobilization of nano‐TiO2 can not only adsorb template metal ions but can also degrade organic pollutants. The results showed that, after the nano‐TiO2 was immobilized on the adsorbent surface, the adsorption ability for the imprinted ion (Ni2+) of this new imprinted adsorbent immobilized with nano‐TiO2 was not affected, but the degradation ability for p‐nitrophenol (PNP) of the surface‐imprinted adsorbent with nano‐TiO2 increased three‐fold compared with that of the surface‐imprinted adsorbent without nano‐TiO2, from 23.8 to 76.1% (at an initial PNP concentration of 20 mg·dm?3). The optimal TiO2 concentration in the adsorbent preparation was 0.025 g·TiO2 g?1 adsorbent. The removal capacity for PNP reached 60.25 mg·g?1 (at 400 mg·dm?3 initial PNP concentration) under UV irradiation. The surface‐imprinted adsorbent with nano‐TiO2 can be reused for at least five cycles without decreasing the removal ability for PNP and the imprinted ion (Ni2+). Copyright © 2006 Society of Chemical Industry  相似文献   

12.
The effect of the reaction conditions on the grafting parameters during grafting of 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid onto sodium carboxymethylcellulose using H2O2/Fe+2 redox pair are studied at 30°C. The grafting ratio, add on, and conversion initially increase with the H2O2 concentration in the range of (10.0–15.0) × 10?2 mol dm?3. Thereafter, these parameters decrease with the H2O2 concentration. The grafting ratio, add on, and conversion increase when increasing the ferrous ion concentration from (0.5 to 4.0) × 10?2 mol dm?3 and decrease with a further increase in the concentration. It is observed that the grafting ratio and add on increase with the monomer concentration, whereas the conversion decrease. The hydrogen ions seem to be facilitating the grafting reaction up to a certain concentration and after this concentration seem to be retarding the process. The grafting ratio, add on, and conversion decrease with the sodium carboxymethylcellulose concentration. When increasing the time period from 60 to 90 min, the grafting parameters increase but decrease thereafter. Similarly, when increasing the temperature from 25 to 30°C, the grafting parameters increase and decrease thereafter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4819–4825, 2006  相似文献   

13.
Glass‐ceramics (GC) generally possess enhanced mechanical properties compared to their parent glasses. The knowledge of how crystallization evolves and affects the mechanical properties with increasing temperature is essential to optimize the design of the crystallization cycle. In this study, we crystallized a glass of the MgO–Al2O3–SiO2 system with nucleating agents TiO2 and ZrO2. The crystallization cycle comprised a 48 hour nucleation treatment at the glass‐transition temperature followed by a 10 hour growth step at a higher temperature. During this cycle, the evolution of crystalline phases was followed by high‐temperature X‐ray diffraction (HTXRD), which revealed the presence of karooite (MgO·2TiO2), spinel (MgO·Al2O3), rutile (TiO2), sillimanite (Al2O3·SiO2), and sapphirine (4MgO·5Al2O3·2SiO2). The same heat treatment was applied for in situ measurement of elastic properties: elastic modulus, E, shear modulus, G, and Poisson's ratio, ν. The evolution of these parameters during the heating path from room temperature to the final crystallization temperature and during the nucleation and the crystallization plateaus is discussed. E and G evolve significantly in the first two hours of the growth step. At the end of the crystallization process, the elastic and shear moduli of the GC were approximately 20% larger than those of the parent glass.  相似文献   

14.
Glasses from the system BaO–SrO–ZnO–SiO2 with different Ba/Sr ratios were characterized regarding crystallization behavior as well as the thermal expansion of almost fully crystallized glasses. Depending on the SrO concentration, different crystalline phases precipitate from the glasses. Those with low SrO concentrations precipitate crystals with the structure of low‐temperature BaZn2Si2O7 as one of the major phases. Higher SrO concentrations cause the formation of Ba1?xSrxZn2Si2O7 solid solutions with the structure of high‐temperature BaZn2Si2O7. Both, the low‐ as well as the high‐temperature phase exhibit very different thermal expansion behaviors ranging from a very high coefficient of thermal expansion in the case of the low‐temperature phase to a very low coefficient of thermal expansion in the case of the high‐temperature phase. The glass‐ceramics with the highest and that with the lowest coefficient of thermal expansion measured between 100°C and 800°C show a difference of 7.9 × 10?6 K?1, which is caused solely by a substitution of BaO with SrO. In contrast, the maximum variation in the thermal expansion of the glasses was only 1.5 × 10?6 K?1. The microstructure of sintered and afterward crystallized glass powders was analyzed via scanning electron microscopy and showed crack‐free samples with low porosity.  相似文献   

15.
Free‐radical crosslinking polymerization and crystallization of acrylic acid (AAc) were investigated by shear storage modulus (G′) measurements in pH 2, as well as in pH 6 and pH 10, by varying the molar ratio of crosslinking agent (N,N′‐methylene bis‐acrylamide; MBAAm) to AAc (0.583 × 10?3, 1.169 × 10?3, 1.753 × 10?3, and 2.338 × 10?3). Our results showed that the pre‐gelation time was the same at pH 2, regardless of the concentration of MBAAm. The propagation time was determined by the initial feed concentration of AAc, and the length of the linear curve in the propagation was proportional to the concentration of MBAAm. The Avrami exponent (n), as an indicative of growing pattern of an infinite molecule, in the crystallization was increased in proportional to the concentration of MBAAm, and generally low at pH 2. In the deceleration phase, n was observed near 1.0 throughout the all specimens. These results indicated that (1) the length of the pre‐gelation period was determined by the ionization of AAc (or pH), (2) the polymerization rate of AAc was not affected by the concentration of MBAAm, and (3) the inhomogeneity of hydrogel was determined by the growing pattern of infinite molecule in propagation phase. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42195.  相似文献   

16.
Composite materials containing Raney Ni and Cu‐ZSM‐5 are highly active catalysts for the selective catalytic reduction (SCR) of NO by NH3. Their catalytic properties were studied with particular attention to the influence of moisture and SO2 in the feed, and to effects of catalyst shaping operations. Composite materials (16–20 wt‐% zeolite) were prepared by mixing the components, with different degree of segregation in the resulting pressed particles, or by growing ZSM‐5 crystallites on the surface of leached Raney Ni, which were then exchanged with Cu ions. Catalytic tests were performed with 1000 ppm NO, 1000 ppm NH3, 2 % O2 in He, at 3–6.5 · 105 h–1 (related to zeolite component). With physical mixtures, the catalytic behaviour strongly depended on the mixing strategy, particles containing both Ni and zeolite being inferior to mixed Ni‐only and zeolite‐only particles. The SCR activity was promoted by 2 % H2O in the feed, SO2 (200 ppm) was a moderate poison at low temperatures, but indifferent or slightly promoting at high temperatures. A catalyst prepared from ZSM‐5 grown on Raney Ni, which was ranked intermediate in dry feed, was promoted to excellent performance in H2O and SO2 containing feed at T > 700 K and was stable for 38 h at 845 K. The results suggest that SCR catalysts containing highly active zeolites should be produced avoiding shaping operations e.g. by use of zeolite crystallites grown on wire packings.  相似文献   

17.
To improve the electrochemical properties and enhance the mechanical strength of solid polymer electrolytes, series of composite polymer electrolytes (CPEs) were fabricated with hybrids of thermoplastic polyurethane (TPU) electrospun membrane, polyethylene oxide (PEO), SiO2 nanoparticles and lithium bis(trifluoromethane)sulfonamide (LiTFSI). The structure and properties of the CPEs were confirmed by SEM, XRD, DSC, TGA, electrochemical impedance spectroscopy and linear sweep voltammetry. The TPU electrospun membrane as the skeleton can improve the mechanical properties of the CPEs. In addition, SiO2 particles can suppress the crystallization of PEO. The results show that the TPU‐electrospun‐membrane‐supported PEO electrolyte with 5 wt% SiO2 and 20 wt% LiTFSI (TPU/PEO‐5%SiO2‐20%Li) presents an ionic conductivity of 6.1 × 10?4 S cm?1 at 60 °C with a high tensile strength of 25.6 MPa. The battery using TPU/PEO‐5%SiO2‐20%Li as solid electrolyte and LiFePO4 as cathode shows an attractive discharge capacity of 152, 150, 121, 75, 55 and 26 mA h g?1 at C‐rates of 0.2C, 0.5C, 1C, 2C, 3C and 5C, respectively. The discharge capacity of the cell remains 110 mA h g?1 after 100 cycles at 1C at 60 °C (with a capacity retention of 91%). All the results indicate that this CPE can be applied to all‐solid‐state rechargeable lithium batteries. © 2018 Society of Chemical Industry  相似文献   

18.
BACKGROUND: The increasing industrial demand for carotenoids has aroused interest in their bio‐production, and the need to reduce production costs has encouraged the use of low cost industrial substrates, such as agro‐industrial residues. Thus the objective of this research was the bio‐production of carotenoids by Sporidiobolus salmonicolor using agro‐industrial substrates (corn steep liquor and sugarcane molasses), pre‐treated with acids (sulphuric and phosphoric). RESULTS: Bio‐production was carried out in an orbital shaker using a 10% (v/v) inoculum, incubation at 25 °C, and agitation at 180 rpm for 120 h in a non‐illuminated environment. The carotenoids were recovered using liquid N2 combined with dimethylsulphoxide for cell rupture, and an acetone/methanol mixture (7:3 v/v) for extraction. CONCLUSION: The complete second‐order design allowed for optimisation of the carotenoid concentration obtained from industrial substrates pre‐treated with acids (sulphuric and phosphoric), obtaining a total carotenoid content of 541.5 µg L?1 using 10 g L?1 sugarcane molasses, 5 g L?1 corn steep liquor and 5 g L?1 yeast hydrolysate at 25 °C, with agitation at 180 rpm and an initial pH of 4.0. Copyright © 2008 Society of Chemical Industry  相似文献   

19.
Chelation efficiency of stimuli‐responsive poly(N‐iospropylacrylamide‐co‐methyacrylic acid) (PNIPAAm‐MAA) nanoparticles with Cu2+ ions from CuSO4·5H2O solution and from wood treated with copper‐based preservatives was studied. It was shown that particle size played a very important role in the adsorption process. The nano‐scale particles showed much improved Cu ion adsorption efficiency, compared with the micro hydrogels. The amount of Cu ion adsorption increased with increase of MAA ratio in copolymers and adsorption efficiency decreased with increased particle size. Furthermore, the adsorption amount varied with adsorption temperature at temperatures both below and above the corresponding low critical solution temperature (LCST). The high adsorption efficiency of Cu ions by PNIPAAm‐MAA polymer particles provides an effective technique for recovering metal ions (e.g., Cu2+) from wood treated with metal‐based preservatives. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

20.
Single‐walled carbon nanotubes (SWCNTs) dispersed in N‐methylpyrrolidone (NMP) were functionalized by addition of polystyryl radicals from 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐ended polystyrene (SWCNT‐g‐PS). The amount of polystyrene grafted to the nanotubes was in the range 20‐25 wt% irrespective of polystyrene number‐average molecular weight ranging from 2270 to 49 500 g mol?1. In Raman spectra the ratios of D‐band to G‐band intensity were similar for all of the polystyrene‐grafted samples and for the starting SWCNTs. Numerous near‐infrared electronic transitions of the SWCNTs were retained after polymer grafting. Transmission electron microscopy images showed bundles of SWCNT‐g‐PS of various diameters with some of the polystyrene clumped on the bundle surfaces. Composites of SWCNT‐g‐PS in a commercial‐grade polystyrene were prepared by precipitation of mixtures of the components from NMP into water, i.e. the coagulation method of preparation. Electrical conductivities of the composites were about 10?15 S cm?1 and showed no percolation threshold with increasing SWCNT content. The glass transition temperature (Tg) of the composites increased at low filler loadings and remained constant with further nanotube addition irrespective of the length and number of grafted polystyrene chains. The change of heat capacity (ΔCp) at Tg decreased with increasing amount of SWCNT‐g‐PS of 2850 g mol?1, but ΔCp changed very little with the amount of SWCNT‐g‐PS of higher molecular weight. The expected monotonic decrease in ΔCp coupled with the plateau behavior of Tg suggests there is a limit to the amount that Tg of the matrix polymer can increase with increasing amount of nanotube filler. Copyright © 2012 Society of Chemical Industry  相似文献   

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