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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 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...