Ethanol perm‐selective B‐ZSM‐5 zeolite membranes from dilute solutions

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     

Selective Catalytic Reduction of NO by Ammonia over Raney‐Ni Supported Cu‐ZSM–5 I. Catalyst Activity and Stability

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.     

A green process for recovery of H2SO4 and Fe2O3 from FeSO4·7H2O by modeling phase equilibrium of the Fe(П)– –H+–Cl– system

Ferrous sulfate heptahydrate FeSO₄·7H₂O is a major waste produced in titanium dioxide industry by the sulfate process and has caused heavy environmental problem. A new green process for the treatment of FeSO₄·7H₂O was proposed to make use of iron source and recycle sulfate source as H₂SO₄. It was found that by adding concentrated HCl to the FeSO₄ solution, FeCl₂·4H₂O was crystallized out, which was subsequently calcined to produce Fe₂O₃ and HCl. Concentrated H₂SO₄ solution (about 65 wt %) was obtained by evaporating the FeCl₂·4H₂O‐saturated filtrate. To facilitate the process development and design, the solubilities of FeCl₂·4H₂O in HCl, H₂SO₄, and HCl + H₂SO₄ solutions were measured and the experimental data were regressed with both the mixed‐solvent electrolyte model and the electrolyte NRTL model. On the basis of the prediction of the optimum conditions for the crystallization of FeCl₂·4H₂O, material balance of the new process was calculated. FeCl₂·4H₂O and Fe₂O₃ were obtained from a laboratory‐scale test with about 70% recovery of ferrous source for a single cycle, indicating the feasibility of the process. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4549–4563, 2017     

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H2O pervaporation process

Using Na⁺ form of perfluorosulfonic acid (PFSA) and poly(vinyl alcohol) (PVA) as coating materials, polysulfone (PSf) hollow fiber ultrafiltration membrane as a substrate membrane, PFSA‐PVA/PSf hollow fiber composite membrane was fabricated by dip‐coating method. The membranes were post‐treated by two methods of heat treatment and by both heat treatment and chemical crosslinking. Maleic anhydride (MAC) aqueous solution was used as chemical crosslinking agent using 0.5 wt % H₂SO₄ as a catalyst. PFSA‐PVA/PSf hollow fiber composite membranes were used for the pervaporation (PV) separation of isopropanol (IPA)/H₂O mixture. Based on the experimental results, PFSA‐PVA/PSf hollow fiber composite membrane is suitable for the PV dehydration of IPA/H₂O solution. With the increment of heat treatment temperature, the separation factor increased and the total permeation flux decreased. The addition of PVA in PFSA‐PVA coating solution was favorable for the improvement of the separation factor of the composite membranes post‐treated by heat treatment. Compared with the membranes by heat treatment, the separation factors of the composite membranes post‐treated by both heat treatment and chemical crosslinking were evidently improved and reached to be about 520 for 95/5 IPA/water. The membranes post‐treated by heat had some cracks which disappeared after chemical crosslinking for a proper time. Effects of feed temperature on PV performance had some differences for the membranes with different composition of coating layer. The composite membranes with the higher mass fraction of PVA in PFSA‐PVA coating solution were more sensitive to temperature. It was concluded that the proper preparation conditions for the composite membranes were as follows: firstly, heated at 160°C for 1 h, then chemical crosslinking at 40°C for 3 h in 4% MAC aqueous solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Experimental study on the solvent regeneration of a CO2‐loaded MEA solution using single and hybrid solid acid catalysts

The performance of a hybrid solid acid catalyst consisting of a physical mixture of γ‐Al₂O₃ and H‐ZSM‐5 in terms of the rate and heat duty for solvent regeneration (i.e., CO₂ stripping) of a CO₂‐rich MEA solution was compared with the individual performance of γ‐Al₂O₃, H‐ZSM‐5, and H‐Y solid acid catalysts using MEA (2–7 mol/L), with initial CO₂ loading of 0.5 mol CO₂/mol MEA at 378 K. It was observed that any catalyst significantly decreased the energy required for CO₂ regeneration. The performance of the catalysts investigated ranked as follows: γ‐Al₂O₃/H‐ZSM‐5 = 2/1 > γ‐Al₂O₃ > H‐ZSM‐5 > H‐Y if the process is in the lean CO₂ loading region whereas it was H‐ZSM‐5 > γ‐Al₂O₃/H‐ZSM‐5 = 2/1 > γ‐Al₂O₃ > H‐Y if the process is in the rich CO₂ loading region. These results highlight the joint dependence on Brønsted/Lewis acidity and mesopore surface area of heat duty for solvent regeneration. © 2015 American Institute of Chemical Engineers AIChE J, 62: 753–765, 2016     

Preparation and properties of a form‐stable phase‐change hydrogel for thermal energy storage

In this study, we aimed to fabricate a form‐stable phase‐change hydrogel (PCH) with excellent mechanical properties and heat‐storage properties. Sodium alginate (SA) and polyacrylamide (PAAm) composite hydrogels were prepared with ionically crosslinked SA in a PAAm hydrogel network. Glauber's salt [i.e., sodium sulfate decahydrate (Na₂SO₄·10H₂O)] was incorporated within the hydrogel network as a phase‐change material. Scanning electron microscopy micrographs revealed that Na₂SO₄·10H₂O was confined in the micropores of the hydrogel inner spaces, and differential scanning calorimetry curves showed that the composite hydrogel possessed a considerable storage potential. Mechanical properties tests, such as tensile and compressive measurements, presented a decreasing trend with increasing Na₂SO₄·10H₂O dosage. We concluded that the prepared composite PCH could be used to design hydrogel materials with thermal‐energy‐storage applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43836.     

A practical approach to produce Mg‐Al spinel based on the modeling of phase equilibria for NH4Cl‐MgCl2‐AlCl3‐H2O system

Based on chemical modeling of phase equilibria for the NH₄Cl‐MgCl₂‐AlCl₃‐H₂O system, a practical approach to produce Mg‐Al spinel (MgAl₂O₄) (widely used as refractory brick, supports in catalysts, and inert material for oxygen carriers) is proposed and proven feasible. This novel process includes coprecipitation of Mg₄Al₂(OH)₁₄·3H₂O from the NH₃‐MgCl₂‐AlCl₃‐H₂O system; calcination of Mg₄Al₂(OH)₁₄·3H₂O to obtain Mg‐Al spinel and recovery of NH₄Cl from NH₄Cl‐rich solutions by feeding MgCl₂‐AlCl₃. A MSMPR reactor was applied to investigate the effect of temperature, feed concentration, and NH₄Cl addition on coprecipitation of precursor Mg₄Al₂(OH)₁₄·3H₂O from MgCl₂‐AlCl₃ solutions with Mg/Al ratio = 2 through gradual addition of NH₄OH. The phase equilibria of the NH₄Cl‐MgCl₂‐AlCl₃‐H₂O system were determined over the temperature range 283.2 to 363.2 K using dynamic method. The experimental solubilities were regressed to obtain new Bromley‐Zemaitis model parameters. These newly obtained parameters were verified by predicting the quaternary system. A chemical model for the NH₄Cl‐MgCl₂‐AlCl₃‐H₂O system has been established with the OLI platform. All the results generated from this study will provide the theoretical basis for Mg‐Al spinel production. The high quality Mg‐Al spinel was prepared by calcination of precursor from 773.2 to 1273.2 K, and the NH₄Cl was successfully recovered through the common ion effect of MgCl₂‐AlCl₃ addition. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1855–1867, 2013     

Effects of water vapor on gas permeation and separation properties of MFI zeolite membranes at high temperatures

Understanding the effects of water vapor on gas permeation and separation properties of MFI zeolite membranes, especially at high temperatures, is important to the applications of these zeolite membranes for chemical reactions and separation involving water vapor. The effects of water vapor on H₂ and CO₂ permeation and separation properties of ZSM‐5 (Si/Al ～ 80) zeolite and aluminum‐free silicalite membranes were studied by comparing permeation properties of H₂ and CO₂ with the feed of equimolar H₂/CO₂ binary and H₂/CO₂/H₂O ternary mixtures in 300–550°C. For both membranes, the presence of water vapor lowers H₂ and CO₂ permeance to the same extent, resulting in negligible effect on the H₂/CO₂ separation factor. The suppression effect of water vapor on H₂ and CO₂ permeation is larger for the less hydrophobic ZSM‐5 zeolite membrane than for the hydrophobic silicalite membrane, and, for both membranes, is stronger at lower temperatures and higher water vapor partial pressures. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

High‐Selectivity Y2O3‐Doped SiO2 Nanocomposite Membranes for Gas Separation in Steam at High Temperatures

Asymmetric structures were fabricated by depositing Y₂O₃‐doped SiO₂ (Si/Y) membranes onto γ‐Al₂O₃ supported by tubular α‐Al₂O₃. The thickness of the Y₂O₃‐doped SiO₂ deposits was approximately 100 nm. The deposits/membranes have micropores with a pore diameter ~ <0.40–0.55 nm. Pore size distribution measurements were conducted directly on the membranes before and after hydrothermal treatment with a nano‐permporometer. The gas permeance properties of the membranes were measured in the temperature range 100°C–500°C. The Y‐doped SiO₂ membrane (Si/Y = 3/1) was found to exhibit asymptotically stable permeances of 2.39 × 10^?7 mol/m²/s/Pa for He and 6.19 × 10^?10 mol/m²/s/Pa for CO₂, with a high selectivity of 386 (He/CO₂) at 500°C for 20 h in the presence of steam. The Y‐doped silica membranes exhibit very high gas permeances for molecules with smaller kinetic diameters. The apparent activation energies of the H₂ permeance at 400°C were 24.2 ± 0.2 and 21.3 ± 0.7 kJ/mol for SiO₂ and Si/Y, respectively.     

Self‐Assembled 3D Hierarchically Structured Gamma Alumina by Hydrothermal Method

Self‐assembled γ‐Al₂O₃ with hierarchical structure was successfully obtained via thermolysis of γ‐boehmite (γ‐AlOOH) particles, which was hydrothermally derived from aluminum ammonium sulfate hydrate (NH₄Al(SO₄)₂·12H₂O), urea, poly‐glycol (PEG)‐2000, and deionized water. SEM observations indicate that the as‐synthesized γ‐AlOOH has hierarchical flower‐like structure, composing of needle‐like building blocks. After calcinations at 800°C, it converts to cubic γ‐Al₂O₃ with hierarchical structure retained by a topotactical process. N₂ adsorption and desorption reveal that the obtained γ‐Al₂O₃ has a BET surface area of 101 m²/g with a narrow mesoporous size of about 13 nm and a broad macroporous‐size distributions of 200–500 nm, respectively. The as‐generated γ‐Al₂O₃ with hierarchical structure shows good capacities for removing Congo red from wastewater, indicating that 3D hierarchical structure has excellent adsorption ability.     

Synthesis of ZSM‐5 by hydrothermal method with pre‐mixing in a stirred‐tank reactor

This work proposed a synthesis route of ZSM‐5 via the hydrothermal method with premixing in a stirred tank reactor (STR). Effects of various operating conditions, including pre‐mixing time, molar ratio of SiO₂/Al₂O₃, TPAOH (organic template agents) concentration, NaCl (alkali metal cations) concentration, crystallization temperature, and crystallization reaction time, on the average particle size (PS) and particle size distribution (PSD) were investigated. It was found that the pre‐mixing time in the STR significantly affect the formation of proto‐nuclei in premixing process and crystal growth in hydrothermal reaction process, and consequently influence the PS and PSD of the prepared ZSM‐5. ZSM‐5 with good thermal stability, a PS of 380 nm, PSD of 0.17–0.9 µm, pore diameter of 2.31 nm, pore volume of 0.19 cm³ · g^?1 and specific surface area of 337.25 m² · g^?1 were obtained under the optimal conditions of a crystallization reaction time of 24 h, a crystallization temperature of 130 °C, a molar ratio of SiO₂/Al₂O₃ of 200, a TPAOH concentration of 3.5 mol · L^?1, NaCl concentration of 0.3 mol · L^?1, and a pre‐mixing time of 5 h. This work indicated that the operating conditions including premixing time have a significant effect on its PS and PSD.     

Composition,structure, and morphology of nanostructured aluminosilicates

The data on synthesizing nanosized potassium aluminosilicates (PAS) with a ratio of Si/Al of 1–5 obtained in the KOH–Al₂(SO₄)₃ · 18H₂O–SiO₂ · nH₂O–H₂O multicomponent system have been presented. Their composition, morphology, and IR and NMR spectra have been studied.     

Study of the Composition,Structure, and Sorption Properties of Nanostructured Aluminosilicates

Sorption properties of synthetic nanostructured potassium aluminosilicates with Si/Al ratios from 1 to 5 fabricated in a multicomponent system KOH–Al₂(SO₄)₃·18H₂O–SiO₂·nH₂O–H₂O under static sorption conditions at various temperatures and nitrate salt background have been investigated; the activation energy of cesium ions sorption has been evaluated.     

Fluorine‐Free Synthesis of Well‐Dispersed Hollow TiO2 Spheres via Ostwald Ripening: Process,Mechanism, and Photocatalytic Performance

Well‐dispersed hollow TiO₂ spheres were synthesized via Ostwald ripening through a fluorine‐free solvothermal process in a n‐PrOH/H₂O mixed solvent. Several commonly used acids, such as HNO₃, HCl, and H₂SO₄, were found to be effective as the ripening‐directing agent to replace the highly corrosive HF, and the hollow TiO₂ sphere size could be modulated by varying the reactant concentrations. The effects of the solvents and reactants were explored in details, which demonstrated that four important criteria existed in this fluorine‐free process to create well‐dispersed hollow TiO₂ spheres, including the utilization of n‐PrOH/H₂O mixed solvent, certain degree of acidity, coexistence of different acids, and the existence of SO₄^2? in the reaction solution. After calcination for a better crystallization, these hollow TiO₂ spheres were composed of pure anatase phase, and had a good photocatalytic degradation performance on RhB under UV illumination.     

Structural evolution of hierarchical porous NiO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites and their application for removal of dyes by adsorption

Hierarchical porous NiO/Al₂O₃ composites were successfully prepared by two-steps. First, the core-shell structured Al₂O₃ microspheres were prepared via a template-free hydrothermal route using KAl(SO₄)₂·12H₂O and Al₂(SO₄)₃·18H₂O as aluminum source. Then, the NiO/Al₂O₃ composites with micro- and nano-hierarchical structures were prepared by a hydrothermal method combining the subsequent calcination process. The obtained characterization result presented that the morphology of hierarchical Al₂O₃ microsphere tuned to irregular platelets by simply varying Ni/Al ratios. The BET analysis showed that the special surface area from 52.12m² g^?1 to 214.8m² g^?1 after two hydrothermal complex process. Effects of Ni/Al ratio, adsorbent dosage, Congo red (CR) concentration, coexisting ions, adsorption time and temperature were investigated. The obtained results indicated that NiO/Al₂O₃ composite had the high adsorption efficiency (99.6%) and great adsorption capacity (186.9mg g^?1) under the optimum conditions. The adsorption isotherm and kinetics data were found to be well fitted and in good agreement with the Langmuir isotherm model and pseudo-second order model, respectively. The hierarchical porous NiO/Al₂O₃ composites presented remarkably higher adsorption efficiency during five recycling, which showed their potential as the highly efficient adsorbent for removal of CR in wastewater.     

Synthesis and characterization of polybenzimidazole/α‐zirconium phosphate composites as proton exchange membrane

To improve the high‐temperature performance of proton exchange membranes, the polybenzimidazole (PBI)/α‐zirconium phosphate (α‐Zr(HPO₄)₂·nH₂O, α‐ZrP) proton exchange composite membranes were prepared in this study. PBI polymer containing a large amount of ether units has been synthesized from 3,3′‐ diaminobenzidine (DAB) and 4,4′‐oxybis (benzoic acid) by a direct polycondensation in polyphosphoric acid. The polymer exhibited a good solubility in most polar solvents. Inorganic proton conductor α‐ZrP nanoparticles have been obtained using a synthesis route involving separate nucleation and aging steps (SNAS). The effects of α‐ZrP doping content on the composite membrane performance were investigated. It was found that the introduction of ZrP improved the thermal stability of the composite membranes. The PBI/ZrP composite membranes exhibited excellent mechanical strength. The composite membrane with 10 wt% ZrP showed the highest proton conductivity of 0.192 S cm^?1 at 160°C under anhydrous condition. The proton conducting mechanism of the PBI/ZrP composite membranes was proposed to explain the proton transport phenomena. The experimental results suggested that the PBI/ZrP composite membranes may be a promising polymer electrolyte used in high temperature proton exchange membrane fuel cells (HT‐PEMFCs) under anhydrous condition. POLYM. ENG. SCI., 56:622–628, 2016. © 2016 Society of Plastics Engineers     

Barium aluminate hydrates: Part V. 2BaO·Al2O3·2H2O and 2BaO·Al2O3

A new compound of formula 2BaO·Al₂O₃·2H₂O has been synthesised and studied by infra-red, X-ray and thermal analytical techniques. This hydrate yielded another crystalline product, 2BaO·Al₂O₃, during dehydration.     

Gas permeation and separation properties of polyimide/ZSM‐5 zeolite composite membranes containing liquid sulfolane

The preparation, characterization, and gas permeation properties of novel composite membranes containing polyimide (PI), liquid sulfolane (SF), and zeolite (ZSM‐5) were investigated to address the interface defects between the PI and the zeolite. The free‐standing composite membranes were prepared by the solvent casting method. The gas permeability of the PI+ZSM‐5 membrane was higher than that of PI, whereas its gas selectivity was significantly reduced, suggesting that these results are attributed to the interface defects. The CO₂ selectivity of PI+ZSM‐5+SF was higher than those of the PI+ZSM‐5 membranes because of the introduction of liquid SF into the interface defects. Furthermore, liquid SF enhanced the CO₂/H₂ selectivity near the recent upper bound. Therefore, the use of liquid SF could be an effective approach to preventing interface defects and increasing the CO₂ selectivity, particularly for CO₂/H₂. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Performance study of modified ZSM‐5 as support for bimetallic chromium–copper catalysts for VOC combustion

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     

Poly(vinyl alcohol)/ZIF‐8‐NH2 mixed matrix membranes for ethanol dehydration via pervaporation

Ethanediamine‐modified zeolitic imidazolate framework (ZIF)‐8 particles (ZIF‐8‐NH₂) is synthesized and incorporated in the poly(vinyl alcohol) (PVA) matrix to fabricate novel PVA/ZIF‐8‐NH₂ mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. The PVA/ZIF‐8‐NH₂ MMMs exhibit enhanced membrane homogeneity and separation performance because of the higher hydrophilicity and restricted agglomeration of the particles, as compared to corresponding MMMs loaded with unmodified particles. The effect of ZIF‐8‐NH₂ loading in the MMMs is studied and the MMM with a 7.5 wt % ZIF‐8‐NH₂ loading shows the best pervaporation performance for ethanol dehydration at 40°C. Various characterization techniques (Fourier transform infrared, scanning electron microscope, contact angle, sorption test, etc.) are used to investigate the MMMs loaded with ZIF‐8 and ZIF‐8‐NH₂ particles. The impact of operation conditions on pervaporation performance is also performed. The performance benchmarking shows that the MMMs have superior separation factors and comparable flux to most other PVA hybrid membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1728–1739, 2016