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The quantification of dispersity is an indispensable part of characterizing polymers. In this work, general dispersity equations for “living” polymers obtained by nitroxide-mediated polymerization ...

In this work, the effect of non-drag forces (lift force, turbulent dispersion force, wall lubrication force and virtual mass force) and bubble induced turbulence (BIT) on the CFD-PBM simulation of ...

The kinetics of the ultraviolet light-induced solution atom transfer radical polymerization (ATRP) of methyl acrylate using titanium oxide (TiO2) was investigated through experiments and modeling b...

A well-controlled atom transfer radicfal polymerization of methyl acrylate (MA) was realized by mechanical mediation (mechanoATRP) in dimethyl sulfoxide (DMSO, 50% v/v). High conversions of typically over 90% were achieved. The resulting polymers had well-controlled molecular weights and very low dispersities (Đ = 1.03–1.09). No polymerization of MA was observed under various conditions from bulk up to 33.3% DMSO (v/v) solution. It was found that adding an equivalent volume of DMSO with respect to MA activated the polymerization. This finding suggested that DMSO played a crucial role in the mechanoATRP of MA. DMSO not only improved the solubility of CuBr2 complex but also facilitated an electron transfer process in the mechanical reduction of CuBr2. For a proof of the concept, a DMSO analogue acrylate, 2-(methylsulfinyl)ethyl acrylate (MSEA), was also polymerized. In addition, the high chain-end functionality of the polymers collected at ∼95% conversion was confirmed by 1H NMR, MALDI-ToF-MS, and in-situ c...

Metal-free atom transfer radical polymerization (ATRP) was successfully achieved in aqueous media for the first time. Polymerization of poly(ethylene oxide) methyl ether acrylate (PEGA480) was well controlled (Đ < 1.40) under visible light irradiation using tetrabromofluorescein (Eosin Y) as catalyst and pentamethyldiethylenetriamine (PMDETA) as electron donor. A validated kinetic model was developed to investigate the process of photoredox catalytic cycle via reductive quenching pathway. Experimental and simulation results showed that electron donor not only had an important influence on the ATRP activation, but also participated in the ATRP deactivation. Furthermore, the effects of water content, catalyst concentration, and degree of polymerization on the polymerization were studied thoroughly by a series of experiments. Good controllability of the polymerization regulated by light on and off confirmed the high degree of temporal control. The livingness of the chains was proved by a successful chain ext...

Thermoresponsive random copolymers consisting of poly(N-isopropylacrylamide) (PNIPAM) and polymerized ionic liquid (IL) poly(1,1,3,3-tetramethylguanidine acrylate) (PTMGA) were synthesized via reversible addition–fragmentation chain transfer radical polymerization (RAFT). The reactivity ratios of NIPAM (rNIPAM = 2.11) and TMGA (rTMGA = 0.56) were determined by the extended Kelen–Todus method. Glass transition temperatures (Tg) of the copolymers were analyzed, which followed the Fox equation very well. The phase transition behaviors of the copolymers in aqueous solution were studied through UV–vis transmission measurements. Their lower critical solution temperature (LCST) ranged from 30.5 to 73.2 °C, depending on the hydrophilic IL content. The apparent pKa related to LCST was determined, and thus the protonation degree was calculated. The hydrophilicity of the copolymers could be regulated by gas treatments. Bubbling CO2 led to lowering the transition temperature while bubbling N2 resulted in its recovery...

A developed three-fluid computational fluid dynamics model was used to investigate the three-phase system in a polyethylene industrial fluidized bed in condensed mode. This model was incorporated with a liquid vaporization modeling scheme comprising heat transfer model, droplet vaporization model, and population balance model to describe liquid evaporation. Numerical results demonstrate that liquid vaporization affects gas velocity distribution, thereby influencing the flow structure. With increasing condensed-liquid contents, the bed temperature gradient at the bed bottom increases and the overall bed temperature decreases. The vaporization rate increases with increasing droplet Sauter mean diameter. Hence, the influence of liquid vaporization is sensitive to droplet diameter.

A low-ppm-level iron (Fe)-based photoinduced atom-transfer-radical polymerization (ATRP) under visible-light irradiation was developed. Various ligands, tris(4-methoxyphenyl)phosphine (TMPP), 4,4′-dinonyl-2,2′-dipyridyl (dNbpy), and tris[2-(dimethylamino)ethyl]amine (Me6TREN), were used to enhance the catalytic activity of Fe complexes. Activator FeII complexes were formed by the reduction of FeIII complexes with a monomer under visible-light irradiation. Linear semilogarithmic plots and low polydispersities (Mw/Mn dNbpy > Me6TREN. Additionally, this polymerization could be ceased and restarted, responding to light off and light on. Retention of the chain-end functionality was anal...

Partially water-soluble monomers achieve phase equilibrium between aqueous and dispersed phases, and the interphase mass transfer plays a significant role in suspension polymerization. This work developed a computational fluid dynamics model to simulate the liquid–liquid suspension polymerization process. Complex multiphase flow behaviors and multiscale polymer properties were simultaneously simulated using the combination of an Eulerian–Eulerian two-phase flow model, an atom transfer radical polymerization kinetics model, a population balance model (PBM), and an interphase transfer model. The simulation results for monomer conversion, molecular weight (Mn), polydispersity index (PDI), and Sauter mean diameter (d32) agreed well with the experimental data, thereby validating the soundness of the multiscale model. The proposed model was then employed to predict key variables of the polymerization system. The coupled model can benefit the optimization and scale-up of suspension polymerization reactors with s...

A reactor model has been first developed with the objective to fundamentally comprehend the qualitative influence of the solid polydispersity on the features of a methanol-to-olefins (MTO) fluidized bed reactor. Since coke deposition on the MTO catalyst significantly affects the reaction rate, with its formation usually taking dozens of minutes to achieve the desired coke content, the optimum average coke content was first obtained based on a filtered computational fluid dynamic (CFD) model. Furthermore, comparison of predictions through a CFD method and a reaction engineering approach was conducted. Predictions basically match the experimental data. Subsequently, the influence of the solid particle size distribution on reactor characteristics was comprehensively explored through a filtered CFD method coupled with the population balance model. Results suggested that the particle breakage performed a significant function in MTO fluidized bed reactors, causing particle size to evidently decrease.

A reactor model for a methanol-to-olefin (MTO) reaction system was constructed by incorporating a filtered drag model, a filtered gas–solid heat-transfer model, and an MTO kinetic model to probe large-scale reactor behavior and explore optimization. First, the efficiency of several typical gas–solid heat-transfer models and kinetic models was evaluated by comparing predicted results with experimental data. Second, the effect of two significant operation parameters, namely, reaction temperature and water-to-methanol ratio, were studied based on the above-mentioned model. Predictions suggested an optimum catalyst residence time (∼33 min) and an average coke content (∼6.74%) of this MTO system. In addition, relatively high temperature maximized ethylene production, and the water introduced into the feed significantly attenuated coke deposition. This work is the first to conduct coarse-grid simulations by using the developed effective filtered-CFD coupled model to probe the reaction flow and explore optimizat...

In this work, a photoinduced iron(III)-based atom transfer radical polymerization (ATRP) without any reducing agents and additional initiators was suggested. In addition, detailed kinetic studies, including the effects of ligand and catalyst concentrations on polymerization kinetics, and the polymerization behaviors using various solvents and monomer types were evaluated for this new polymerization technique. Results showed that photoinduced iron(III)-mediated ATRP using 5000 ppm catalyst loading with 1 equiv of ligand in N,N-dimethylformamide (DMF) produced poly(methyl methacrylate) with low molecular weight distribution (Mw/Mn < 1.45) and that the evolution of molecular weight (Mn) was linearly related to monomer conversion. 1H NMR analysis confirmed that the resulting polymer prepared through photoinduced ATRP in the present work was initiated by methyl 2,3-dichloroisobutyrate. Facile temporal control and the successful chain extension highlighted the good chain-end functionality of the resulting polym...

An iron- and methyl methacrylate (MMA)-based electrochemically mediated atom transfer radical polymerization (eATRP) system was developed for the first time. Kinetic behaviors, including the effect of applied potential and catalyst loading, were systematically investigated. Results indicated that with more negative electrode potential, the polymerization rate increased until the mass transport limitation was reached. However, reduction of the catalyst loading had adverse effects on polymerization behaviors, such as decreased polymerization rate and increased molecular weight distributions (Mw/Mn). In addition, a kinetic model based on the method of moments was also constructed to explain the mismatch in Mn and Mn,theo. Simulation results showed that slow initiation significantly influenced on the kinetic behaviors in this system. Iron(II) bromide-catalyzed normal ATRP, iron(III) bromide-catalyzed eATRP, and copper(II) bromide-catalyzed eATRP were conducted to compare and elucidate their respective polymer...

Wastewater contaminated with oil or organic compounds poses threats to the environment and humans. Efficient separation of oil and water are highly desired yet still challenging. This paper reports the fabrication of a smart fiber membrane by depositing pH-responsive copolymer fibers on a stainless steel mesh through electrospinning. The cost-effective precursor material poly(methyl methacrylate)-block-poly(4-vinylpyridine) (PMMA-b-P4VP) was synthesized using copper(0)-mediated reversible-deactivation radical polymerization. The pH-responsive P4VP and the underwater oleophilic/hydrophilic PMMA confer the as-prepared membrane with switchable surface wettability toward water and oil. The three-dimensional network structure of the fibers considerably strengthens the oil/water wetting property of the membrane, which is highly desirable in the separation of oil and water mixtures. The as-prepared fiber membrane accomplishes gravity-driven pH-controllable oil/water separations. Oil selectively passes through the membrane, whereas water remains at the initial state; after the membrane is wetted with acidic water (pH 3), a reverse separation is realized. Both separations are highly efficient, and the membrane also exhibits switchable wettability after numerous cycles of the separation process. This cost-effective and easily mass-produced smart fiber membrane with excellent oil-fouling repellency has significant potential in practical applications, such as water purification and oil recovery.

To search for robust CO2 capture materials, two types of ionic liquids, namely, (p-vinylbenzyl)trimethylammonium tetrafluoroborate ([VBTMA][BF4]) and (p-vinylbenzyl)trimethylammonium hexafluorophosphate ([VBTMA][PF6]), were synthesized and immobilized onto a mesoporous silica (meso-silica) support by the surface-initiated atom-transfer radical polymerization (SI-ATRP) method. The prepared sorbents meso-SiO2–P[VBTMA][BF4] and meso-SiO2–P[VBTMA][PF6] were well-characterized. Their adsorption behaviors toward CO2 from simulated flue gases at different pressures were investigated using an adsorption column. Based on a simulated flue gas containing 10 vol % CO2 at 30 °C, the highest CO2 adsorption capacity of meso-SiO2–P[VBTMA][BF4] was 0.4025 mmol g–1, whereas the corresponding value for meso-SiO2–P[VBTMA][PF6] was 0.3793 mmol g–1. Compared with pure poly(ionic liquid)s, the existence of a meso-silica core improves the CO2 capture capacity. Furthermore, the presence of vapor can improve the CO2 capture capaci...

A series of thermal-responsive block copolymers, i.e., poly(methyl methacrylate)-block-poly(N-isopropylacrylamide) (PMMA-b-PNIPAAm), were successfully synthesized via successive copper(0)-mediated reversible-deactivation radical polymerization technology. Thermal properties of block copolymers with different PNIPAAm chain lengths were investigated by differential scanning calorimetery (DSC) and thermogravimetric analysis (TGA). The well-separated glass transition temperature values shown in DSC results indicate that two chemically different blocks, PNIPAAm and PMMA, are incompatible and phase-segregated. The thermal degradation results show that the thermal stability of these copolymers was improved through incorporating the PNIPAAm segments. The PMMA120-b-PNIPAAm86 and PMMA120-b-PNIPAAm130 maintain stability and undergo one-stage degradation when the temperature increases above 360 °C. Because of the synergistic effect of copolymer composition and copolymer film roughness, the obtained reversible thermal...

A comprehensive kinetic model based on the mechanism of supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) was developed to better understand the kinetics of copper(0)-mediated reversible-deactivation radical polymerization [Cu(0)-mediated RDRP]. Simulation results show that diffusional limitation on termination significantly affects on polymerization. A comprehensive description of the variation trend of soluble species and reaction rates during polymerization was illustrated by simulation. The effects on kinetics of four key rate constants (i.e., ka0, kdisp, ka1, kcomp) involved in Cu(0)-mediated RDRP were investigated in detail, which contributed to greater insight into the differences between the SET-LRP and SARA ATRP mechanisms. Finally, Cu(0)-mediated RDRPs of methyl methacrylate (MMA) and butyl methacrylate (BMA) were conducted to study the polymerization kinetics at 25 °C. Results of simulations and experiments performed under polymerization conditions show ...

A kinetic model was developed for the atom transfer radical copolymerization (ATRcoP) of methyl methacrylate (MMA) and 2-(trimethylsilyl) ethyl methacrylate (HEMA-TMS) in tank reactors under three typical feeding modes, namely, batch, semibatch, and continuous feeding. The kinetic parameters for ATRcoP equilibrium were estimated from the model using the experiment data obtained under the batch mode. The simulation results were validated using the experimental data for the semibatch process. An excellent agreement between experiment and simulation data suggests that the model is suitable for simulating the copolymerization. The effects of different operating modes on the ATRcoP characteristics were investigated. The results demonstrated that each reactor possesses its own advantages and disadvantages. Furthermore, this study offers thorough polymerization characteristics comparison with the use of a constant ATRcoP system, and the results show a promising design in determining the optimal operating conditi...

National Natural Science Foundation of China [21276213]; State-Key Laboratory of Chemical Engineering of Tsinghua University [SKL-ChE-13A05]; Key Laboratory of Advanced Control and Optimization for Chemical Processes of the National Ministry of Education of China [2012ACOCP03]

National Ministry of Science and Technology of China [2012CB21500402]; National Natural Science Foundation of China [21276213, 21076171]; State-Key Laboratory of Chemical Engineering of Tsinghua University [SKL-ChE-13A05]

National Natural Science Foundation of China [21276213]; National Ministry of Science and Technology of China [2012CB21500402]; State-Key Laboratory of Chemical Engineering of Tsinghua University [SKL-ChE-13A05]

National Natural Science Foundation of China [21076171]; National Ministry of Science and Technology of China [2012CB21500402]; State Key Laboratory of Chemical Engineering of Tsinghua University [SKL-ChE-10A03]

China National Petroleum Corporation ; China Lanzhou Petrochemical Company ; Fujian Petrochemical Company of SINOPEC ; National Natural Science Foundation of China [21076171]

National Natural Science Foundation of China [National Natural Science Foundation of China (Grant 20406016]; China National Petroleum Corp.

In the present study, a reactor design for the direct preparation of dichloropropanol (DCP) from glycerol (GLY) is presented. As an optimum design, a reactive distillation (RD) column in which the second chlorination of GLY occurs during the direct preparation of DCP from GLY has been introduced. Using a simple equilibrium mathematical model of RD, a pilot plant scale column is designed. Furthermore, the whole preparation process of DCP from GLY used the optimum RD column as the central unit is simulated by using an advanced software tool, namely ASPEN PLUS. The pilot plant realization of the whole preparation process is presented and its results are compared with the theoretical prediction. On the basis of the pilot plant data and simulated results, a new technology of DCP production has been designed.

Direct preparation of 1,3-dichloro-2-propanol from glycerol is carried out in a batch reactor using acetic acid catalyst at 363−393 K. The analytical technique, gas chromatography, is employed in order to follow the time evolution of the reagents. The kinetic model of the process is developed. Furthermore, the model parameters of the process are also determined by data fitting. The results show that direct preparation follows the SN2 mechanism. A kinetic model corresponding to the mechanism is proposed in this work. The experimental results show that the kinetic model agrees well with the experiments.