Feed Molar Ratio Research Articles

Improving humidity sensing properties of copolymer-based polyelectrolytes by modifying the chemical structure and content of the comonomers

Three kinds of copolymer based polyelectrolytes, including hydrolyzed and sulfonated poly(styrene-alt-maleic anhydride) (HSPSMA), hydrolyzed poly(sodium p-styrenesulfonate-co-maleic anhydride) (HPSSMA), and poly(sodium p-styrenesulfonate-co-itaconic acid) (PSSIA), have been synthesized by the radical copolymerization and functionalized via sulfonation and hydrolyzation. The polyelectrolytes were characterized by FT-IR, 1H-NMR and 13C-NMR, scanning electron microscopy and static water contact angle measurements, and their humidity sensing properties have been investigated at room temperature. The chemical structure and content of the comonomers have great effect on the humidity sensing behaviors of corresponding polyelectrolytes, such as response time, hysteresis and response magnitude, which is ascribed to the distinct interactions of the sensing materials with water molecules. Under optimal conditions, the composite of crosslinked PSSIA (molar feed ratio of SS/IA = 1/4) with polyaniline displayed good response magnitude (impedance variation of two orders of magnitude between 10%RH and 90%RH), small hysteresis (˜4.5%RH) and fast response (t90% of 9 s and 17 s for adsorption and desorption process). The work provides a new approach for the construction of high performance polyelectrolyte based humidity sensors.

Cu-K/Al2O3 based catalysts for conversion of carbon dioxide to methane and carbon monoxide

A series of Cu-K/Al2O3 catalysts were synthesized by wet impregnation technique. The reduced catalysts were further used for conversion of carbon dioxide to methane and carbon monoxide. Moreover, the fresh and used catalysts were characterized to investigate the changes in the surface morphology, metal dispersion, surface area, crystalline phases, and functional groups of studied catalysts. The SEM analysis of fresh and spent catalysts showed no remarkable difference in surface morphology with irregular shaped agglomerated particles. Furthermore, TEM micrographs presented the well distribution of metal catalyst over alumina support. The decrease in surface area from 115 to 77 m2/g for Cu1.62-K0.5/Al2O3 after reaction was related to sintering and oxidation of catalyst during reaction. XRD revealed the disappearance of some minor peaks which can be associated with the sintering of spent catalyst. FTIR also presented some new peak for spent catalyst which can be linked with metal oxides. Moreover, various reaction conditions of temperature (230, 400, and 600 °C), pressure (1 and 7 bar), and feed molar ratio of H2/CO2 (2:1 and 4:1) were investigated using different Cu loading (0, 1, 1.25, 1.62, and 4 weight percent). A maximum CO2 conversion of 63% with 39% CH4 selectivity was achieved by using Cu1.62-K0.5/Al2O3 at 600 °C, molar ratio of H2/CO2 4 under 7 bar. The presence of K on the surface of synthesized catalyst increased the CO2 conversion from 48% (Cu1/Al2O3) to 55% (Cu1-K0.5/Al2O3) at above mentioned reaction conditions which suggested the promoter effect of K during conversion of carbon dioxide.

A facile synthesis of Mn doped CsPbCl3 perovskite with high photoluminescence properties

Manganese (Mn)-doped CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) has attracted tremendous interests recently, since the partial replacement of Pb with Mn can significantly enhance the photoluminescence quantum yields (PL QYs) of the QDs and achieve bright yellow light for advanced display applications. The present paper develops a halide-rich method to synthesize Mn-doped CsPbCl3 QDs by using MnO2 instead of MnCl2. X-ray photoelectron spectroscopy (XPS) measurements confirm that Mn2+ was located in the CsPbCl3 QDs lattice. The PL tests demonstrate a PL QY value up to 66% when the molar feed ratio of Pb/Mn/Cl is 1:1:8.

Synthesis and characterization of hydrophilicity-controlled poly(arylene ether sulfone) copolymers with phenolphthalein-based carboxylic acid groups for separation membrane applications

Hydrophilicity-controlled poly(arylene ether sulfone) copolymers with phenolphthalein-based carboxylic acid groups (PES-COOH-X) were synthesized via direct copolymerization by adjusting the feed molar ratio. The chemical structures of the obtained copolymers were confirmed by 1H nuclear magnetic resonance (NMR) spectroscopy. The copolymers showed good solubility in common aprotic solvents and exhibited excellent mechanical properties. The water contact angles of the obtained copolymers could be reduced by approximately 52% from 92.1° to 44.2° with increasing content of phenolphthalein-derived monomer, 2-[bis(4-hydroxyphenyl)methyl] benzoic acid (PPH-COOH), in the feed molar ratio. A series of PES-COOH-X membranes was prepared via a conventional immersion precipitation phase inversion method. The effects of the monomer feed molar ratio on the morphology, hydrophilicity, pure water flux, and water uptake of the prepared membranes were investigated. The results showed that the pure water flux of the PES-COOH-X membranes was significantly enhanced by almost a factor of two as compared to the pristine PES membrane. From the water contact angle data, it was identified that the hydrophilicity of the membranes was increased rapidly with increasing PPH-COOH content in the membranes. These hydrophilicity-controlled poly(arylene ether sulfone) copolymers may be considered as good candidates for separation membrane materials.

RAFT synthesis, properties and morphologies via thermal annealing of new azo-based ABA triblock copolymers bearing rigid and soft segments

In this study, a series of novel ABA-type triblock azo-copolymers (TBCs) consisting of PEG and PCAEMA segments were synthesized by RAFT polymerization. The TBCs were characterized by 1H-NMR, GPC, DSC, OPM, AFM, GISAXS, and UV-vis. Number-average molecular weight (≤34,200 g/mol) and molecular weight distribution (≤1.44) were slightly increased with increasing the feed molar ratio of monomer to macroinitiator. This indicates a controlled/living polymerization with good distribution. All TBCs displayed transitions attributed to smectic-to-nematic and nematic-to-smectic phases at 108 °C and 104 °C, respectively. TBC with 34 wt% azobenzene displayed fan-shaped focal conic texture, while TBCs containing 46, 53, 58, 63, and 71 wt% azobenzene revealed batonnet textures. TBC-3 and TBC-4 having 53 and 58 wt% azo contents produced lamellar and a mixture of cylinder and lamellar nanostructures compared to other TBCs, which formed hexagonal cylindrical nanostructures. Every TBCs exhibited photoresponsive behavior under UV irradiation and thermal relaxation.

Normal and reverse AOT micelles assisted interfacial polymerization for polyaniline nanostructures

We report here the synthesis of polyaniline (PANI) nanomaterials using sodium bis (2-ethylhexyl) sulfosuccinate (AOT) micelles assisted chemical oxidative interfacial polymerization. We have employed two interfaces (chloroform-water and hexane-water) and two oxidizing agents (ammonium persulfate and ferric chloride). The anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) forms normal micelles in aqueous solution and reverse micelles in hydrophobic solvents like hexane or chloroform. The factors influencing the properties and morphologies of polyaniline nanomaterials such as monomer: surfactant ratio, monomer: oxidant ratio, types of interfaces and oxidants used have been studied. Powder X-ray diffraction of the polyaniline nanomaterials have revealed that polyaniline samples were semi-crystalline in nature. Morphology of polyaniline samples studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have revealed that most of the polyaniline nanomaterials synthesized using ferric chloride possess spherical nature, whereas polyaniline samples synthesized using ammonium persulfate (APS) possess short nanofibers especially at lower aniline/AOT mole ratio in feed (12.5–6.5). The four probe electrical conductivity of the samples were found to be of the order of 1.8 × 10−1 to 8.6 × 10−1 S/cm. Thermal stability of the polyaniline samples recorded by thermogravimetric analysis (TGA) have revealed that polyaniline samples were thermally stable up to 275 °C for 10% weight loss. Interfacial polymerization of aniline monomer using reverse micelles of AOT in hexane phase and ammonium persulfate as oxidizing agent in aqueous phase have been proved to be efficient method for the synthesis of short polyaniline nanofibers.

Theoretical evaluation of various configurations of silica membrane reactor in methanol steam reforming using CFD method

The main purposes of this work was to evaluate from a theoretical point of view the performance of silica membrane reactors (MRs) in various configurations for generating hydrogen via methanol steam reforming (MSR) reaction using a two dimensional computational fluid dynamic (CFD) method, presenting details about molar fractions of gas species, velocity and pressure distributions at the simulated conditions. The CFD model was firstly validated and, then, used for the simulations, achieving an acceptable agreement between numerical outcomes and experimental data. The simulations were realized for MSR reaction carried out in three types of silica MRs, namely: 1) silica MR with cocurrent flow pattern (MR1); 2) silica MR with countercurrent flow pattern (MR2); 3) silica MR with countercurrent flow pattern including a water gas shift (WGS) reaction stage in the permeate side (MR3), meanwhile comparing the results with a traditional reactor (TR). The influence of several operating parameters (reaction temperature and pressure, and feed flow rate) on the performance of the aforementioned silica MRs in terms of methanol conversion, hydrogen yield and CO-selectivity was evaluated and the results compared with an equivalent TR. The simulations via CFD method indicated the MR3 results to be the best solution over the other MR proposed configurations and the TR as well, presenting the best simulation results at 10 bar of transmembrane pressure, 513 K, SF = 6, GHSV = 6000 h−1 and feed molar ratio = 3/1 with CO selectivity ≤0.04%, methanol conversion and hydrogen yield >90%.

Ozonation and ozone-enhanced photocatalysis for VOC removal from air streams: Process optimization, synergy and mechanism assessment

The present work evaluates ozone driven processes (O3, O3/UVC, O3/TiO2/UVA) in the NETmix mili-photoreactor, as a cost-effective alternative for the removal of volatile organic compounds (VOCs) from air streams, using n-decane as a model pollutant. The network of channels and chambers of the mili-photoreactor was coated with a TiO2-P25 thin film, resulting in a catalyst coated surface per reactor volume of 990 m2 m−3. Ozone and n-decane streams were fed to alternate chambers of the mili-photoreactor, promoting a good contact between O3/n-decane/catalyst. Initially, direct reaction between n-decane and ozone (ozonation) was assessed for different O3/n-decane (O3/dec) feed molar ratios and total feed flow rates. Under the best conditions, ozonation process achieved total n-decane conversion (below the limit of detection), yielding a reaction rate (rdec) of 6.8 μmol min−1 or 6.7 mmol m−3reactor s−1. However, the low reactivity of ozone with the degradation by-products resulted in a quite poor mineralization (~10%). For the O3/UVC system, an increase on relative humidity from 7 to 40% slight improved the n-decane oxidation rate, mainly associated with the generation of HO from the reaction of active oxygen radicals (O) and water molecules. A strong synergistic effect was observed when coupling TiO2/UVA photocatalysis with ozonation (O3/TiO2/UVA), enhancing substantially the mineralization of n-decane molecules up to 100% under O3/dec feed molar ratio of 15, photonic flux of 2.67 ± 0.03 J s−1 and a residence time of 2.0 s. Different reaction intermediates were detected for O3, TiO2/UVA and O3/TiO2/UVA oxidative systems, indicating the participation of different oxidant species (O3, HO, O, etc.).

CO2 reduction by C3N4-TiO2 Nafion photocatalytic membrane reactor as a promising environmental pathway to solar fuels

We investigated CO2 photocatalytic reduction coupling, for the first time in literature, the assets offered by the continuous operating mode using C3N4-TiO2 photo-catalyst embedded in a dense Nafion matrix. The reactor performance was analyzed under UV–vis light in terms of productivity, selectivity and converted carbon. Reaction pressure was specifically investigated for its effect as a “driver” in determining reactor performance, modulating products removal from the reaction volume. In addition, the membrane reactor performance was explored as a function of H2O/CO2 feed molar ratio and contact time. The higher feed pressure (5 bar) led to a lesser MeOH production and a greater amount of HCHO, owing to a hindered desorption, which promoted partial oxidation reactions. Total converted carbon instead did not vary significantly with reaction pressure. Membrane reactor with C3N4-TiO2 photocatalyst resulted more performant than other photocatalytic membrane reactors in terms of carbon converted (61 μmol gcatalyst−1 h−1).

Steam reforming of acetone over NiCoMgAl mixed oxide catalysts obtained from hydrotalcite precursors

Layered double hydroxides obtained via co-precipitation method possess a kind of hydrotalcite structure comprising Ni2+/Co2+/Mg2+/Al3+cations in various amounts. Upon calcination of the hydrotalcite precursor, NiCoMgAl mixed oxides catalysts of varying Ni:Co ratio (0.3, 1.0 and 3.0) were obtained. These catalysts were tested for steam reforming of acetone at temperatures between 450 and 550 °C, with a molar feed (water/acetone) ratio of 4–10 and in the space-time range of 10–24 kg cat h/kmol acetone. Around 99% conversion of acetone was obtained over all the mixed oxide catalysts. However, a maximum hydrogen selectivity of ∼80% was obtained over NiCoMgAl(0.33). The time-on-stream behaviour was studied for 4 h at 500 °C and water/acetone molar ratio of 6. The catalyst showed good stability at the reforming conditions. Both homogeneous and heterogeneous kinetic models were developed for the complex reforming reaction systems.

A rate-based method for dynamic analysis and optimal design of reactive extraction: n-Hexyl acetate esterification as an example

Abstract The dynamic analysis and optimal design of reactive extraction are challenging due to high nonlinearity of model equations and tough decision of judging criteria. In this work, a dynamic rate-based method is developed on gPROMS platform to get easy access to the solutions of reactive extraction with phase splitting. Based on rigorous criteria, dynamic analysis from initial state to final equilibrium (e.g., evolution of phase composition, mass transfer rate and reaction rate) and optimal design of operating conditions (e.g., extractant dosage and feed molar ratio) are achieved. To illustrate the method, the esterification of n-hexyl acetate is taken as an example. The approach proves to be reliable in the analysis and optimization of the exemplified system, which provides instructive reference for further process design and simulation of reactive extraction.

Application of aspen plus to renewable hydrogen production from glycerol by steam reforming

Steam reforming is the most favored method for the production of hydrogen. Hydrogen is mostly manufactured by using steam reforming of natural gas. Due to the negative environmental impact and energy politics, alternative hydrogen production methods are being explored. Glycerol is one of the bio-based alternative feedstock for hydrogen production. This study is aimed to simulate hydrogen production from glycerol by using Aspen Plus. First of all, the convenient reactor type was determined. RPlug reactor exhibited the highest performance for the hydrogen production. A thermodynamic model was determined according to the formation of byproduct. The reaction temperature, water/glycerol molar feed ratio as reaction parameters and reactor pressure were investigated on the conversion of glycerol and yield of hydrogen. Optimum reaction parameters are determined as 500 °C of reaction temperature, 9:1 of water to glycerol ratio and 1 atm of pressure. Reactor design was also examined. Optimum reactor diameter and reactor length values were determined as 5 m and 50 m, respectively. Hydrogen purification was studied and 99.9% purity of H2was obtained at 25 bar and 40 °C. The obtained results were shown that Aspen Plus has been successfully applied to investigate the effects of reaction parameters and reactor sizing for hydrogen production from glycerol steam reforming.

Effect of ionic liquid in Ni/ZrO2 catalysts applied to syngas production by methane tri-reforming

This study investigates the influence of ionic liquid in morphology, acid-base properties, metal dispersion and performance of 5%Ni/ZrO2 catalysts in the methane tri-reforming reaction. Zirconia was prepared by precipitation and the catalysts by wet impregnation. The ionic liquid modified the acid and basic character of the catalysts and positively influenced the methane tri-reforming reaction efficiency. The reaction was evaluated with synthetic biogas and with stoichiometric feed molar ratio (CH4: CO2: H2O: O2 = 1:0.5:0.5:0.1 and CH4: CO2: H2O: O2 = 1:0.33:0.33:0.16). The Ni/ZrO2 prepared with ionic liquid exhibits promising catalytic activity and stability in methane tri-reforming at 800 °C in 4 h run, without coke formation. An increase in the reaction temperature results in an increase of hydrogen yield and the methane conversion, reaching ∼85% at 850 °C. The presented results demonstrate that the tri-reforming reaction could be used for production of syngas with H2/CO ratio appropriate for methanol synthesis.

A conceptual investigation for the simultaneous production of gasoline and ammonia in thermally coupled reactors

In recent years, there have been many efforts to improve the catalytic naphtha reforming, due to the importance of this process in the industry. In this research, simultaneous production of gasoline and ammonia in the thermally coupled reactor is studied theoretically. It is considered that the naphtha reforming process as the endothermic reaction takes place in the shell side of the reactor and ammonia synthesis process as the exothermic reaction takes place in the tube side of the reactor. This configuration leads to an increase in thermal efficiency and reduces operational costs due to the elimination of interstage heaters for catalytic naphtha reforming and reducing of thermal load of condensers for ammonia synthesis unit. In the current research, the results of this new configuration have been compared with results of the conventional naphtha reactors. Obtained results of simulation show an acceptable increase in production yield of the aromatics in reformate compared to the conventional naphtha reforming reactors. On the other hand, the conversion of nitrogen is reduced compared to the conventional ammonia synthesis process slightly. The effect of parameters such as the inlet temperature of the endothermic side, the inlet molar flow rate of the exothermic side, number of tubes and hydrogen to hydrocarbon molar ratio in the naphtha feed on the system performance have been investigated. As well as, some adjustable parameters have been optimized with genetic algorithm method to determine the best solution for this suggested system.

Tannin‐Tethered Gelatin Hydrogels with Considerable Self‐Healing and Adhesive Performances

AbstractHydrogels, especially the ones with self‐recovery and adhesive performances, have attracted more and more attention owing to their wide practical potential in the biomedical field involving cell delivery, wound filling, and tissue engineering. Tannic acid (TA), a nature‐derived gallol‐rich polyphenol, exhibits not only unique chelating properties with transition metal cations but also desirable anti‐oxidation properties and strong bonding capability to proteins and gelatin. Thus, taking advantage of the versatility of TA, a one‐pot method is proposed herein to produce TA‐modified gelatin hydrogels with the aid of NaIO4 under basic conditions. By changing the amount of NaIO4 used, the obtained hydrogels are covalently cross‐linked to different degrees and consequently exhibit diversity in their self‐healing and adhesive properties. The gelling time, viscoelasticity, and morphology of hydrogels are investigated, and when the feed molar ratio of NaIO4 to TA is adjusted to 15:1, the fabricated hydrogel shows optimum self‐healing efficiency of 73% and adhesive strength of 36 kPa. Additionally, considering the completely natural origin of TA and gelatin, this study offers an original way for the fabrication of biocompatible self‐healing and adhesive materials.

Separation process study of liquid phase catalytic exchange reaction based on the Pt/C/PTFE catalysts

Abstract The liquid phase catalytic exchange (LPCE) reaction is an effective process for heavy water detritiation and production of deuterium-depleted potable water. In the current study, hydrophobic carbon-supported platinum catalysts (Pt/C/PTFE) with high efficiency as reported previously for LPCE were prepared and comprehensive performance evaluation method is applied to evaluate the separation behaviors of LPCE systematically. Experimental results indicate that the optimum reaction temperature of 60–80 °C and the molar feed ratio G/L of 1.5–2.5 would lead to higher separation efficiencies. As to the packing method, a random packing mode with a packing ratio of hydrophobic catalysts 0.25 is recommended. In addition, thermodynamic analysis corresponds well with experimental results under lower temperature and G/L, while the suppression of kinetic factors should not be neglected when T > 80 °C and G/L > 1.5.

Synthesis and Evaluation of Multifunctional Anionic Initiators Based on n‐BuLi and Meta‐Diisopropenyl Benzene

Multifunctional anionic initiators based on n‐BuLi and the diolefin m‐DIB (meta‐diisopropenylbenzene) were synthesized and stored at different temperatures, using different polar modifier contents and solvents. Solution styrene polymerizations were then used to evaluate the performances of the produced initiators. Based on the obtained results, it is shown that the best initiators were the ones prepared at 40 °C, using the DTHFP/BuLi molar feed ratio of 0.1 in cyclohexane. At these preparation conditions, the produced initiator has higher contents of multifunctional species and presents higher stability. The DTHFP/n‐BuLi ratio of 0.1 was shown to be the most appropriate because it minimizes the formation of oligomers and allows for suitable initiation of styrene polymerizations.

Poly(ethylene oxide)-based composite polymer electrolytes embedding with ionic bond modified nanoparticles for all-solid-state lithium-ion battery

Flexible composite polymer electrolytes (CPEs) are fabricated by reversible addition-fragmentation chain transfer (RAFT) polymerization of poly(ethylene glycol) methacrylate (PEGMA) and poly(ethylene glycol) diacrylate (PEGDA), followed by physical doping with ionic bond modified nanoparticles (IBNs) based on nanoscale silica. In reference to PEGMA-PEGDA cross-linked framework prepared by ultraviolet light irradiation directly, RAFT polymerization endows the electrolyte membranes with excellent flexibility, and further increase in yield stress and tensile modulus achieved with IBNs adding in the system. CPEs obey Arrhenius law and its ionic conductivity is found to be maximum of 6.77 × 10−5 S cm−1 at 30 °C, but that of the electrolytes consisted of the same molar feeding ratio of PEGMA/PEGDA without IBNs blending is 3.76 × 10−5 S cm−1 at 30 °C, indicating that the loading of IBNs improves the ionic conductivity, due to the elevated chain mobility. Besides, the electrochemical stability of CPEs is promoted in comparison with the traditional linear poly(ethylene oxide) (PEO) based electrolytes. Moreover, the electrolyte membrane exhibits good cycling performance with lithium iron phosphate and retained 94.3% of capacity after 40 charge-discharge cycles, demonstrating the great potential of this kind of CPEs prepared in this study as electrolyte materials for battery systems.

Free radical copolymerization of trifluoroethyl methacrylate with perfluoroalkyl ethyl acrylates for superhydrophobic coating application

The chemical constitution is a critical factor to the surface properties and the applications of polymers. In this paper, the random copolymers of trifluoroethyl methacrylate (FMA) and perfluoroalkyl ethyl acrylate (TEAc-8) with different feed molar ratios were synthesized by radical solution polymerization. The chemical structures of copolymers [poly(FMA-co-TEAc-8)] were characterized by FTIR, 1H NMR and 19F NMR. Thermogravimetric analysis and differential scanning calorimetry were performed to analyze thermal properties of copolymer. These copolymers demonstrated good thermal stability and lower glass transition temperature (Tg) by introducing the flexible perfluoroalkyl ethyl acrylate with long side chain. At the same time, the surface hydrophobicity of the prepared copolymer coatings was significantly improved, and the water contact angles could be raised to 117° when the molar ratios of TEAc-8 increased to 80%. Furthermore, superhydrophobic coatings were fabricated simply based on organic/inorganic hybrid. The water contact angle and the contact angle hysteresis of the composite coatings higher than 150° and lower than 5°, respectively, were achieved with blending of 2 wt% nano-silica. These superhydrophobic hybrid coatings have superb potential for large-scale and practical applications in self-cleaning and corrosion prevention owing to their simplicity in preparation.

A thermothickening polymer as a novel flocculant for oily wastewater treatment

ABSTRACT In this work, the effectiveness of poly(acrylamide-co-N,N-diethylacrylamide-co-n-butylstyrene), designated as TTF which exhibits a thermothickening behavior, was examined as a novel flocculant for oily wastewater treatment. The effects of flocculant concentration, temperature, and electrolyte on TTF flocculation performance were examined in comparison with cationic polyacrylamide (CPAM). TTF exhibited a lower critical solution temperature (LCST) of 53°C when the monomer feed molar ratio of acrylamide/N,N′-diethyl acrylamide/n-butylstyrene: 73/26/1 was used. Moreover, increasing the concentration of NaCl and CaCl2 adversely reduced the LCST of TTF. Furthermore, treatment with TTF proved excellent performance in removing oil and suspended solid than CPAM in all conditions investigated.