Chemical Engineering

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An elegant, simple, and exact analytical solution (AS) was obtained for a large range of elementary steps with practical importance in free radical polymerization. The AS matches excellently with the numerical solution for the four cases of monomer-polymer systems studied ranging from the slowest to the fastest. It works equally well for different initiators, different initiator and monomer concentrations, presence or absence of solvent, various solvent volume fractions, and different temperatures. It also matches quite well with experimental data reported in the literature. This AS is not only in line with previous published solutions but also extends their applicability in a natural way. Overall, the conceptual correctness as well as predictive capabilities of the derived AS are established beyond doubt. This AS has the potential to be used in various practical applications such as model based process control, CFD simulations, and so forth. © 2014 American Chemical Society.

(SoE) School of Engineering

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Macromolecules

Analytical solution of free radical polymerization: Derivation and validation

Linear and branched polymers of 2-(dimethylamino)ethyl methacrylate (PDMAEMA) were synthesized in flow by atom transfer radical polymerization (ATRP) and self-condensing vinyl copolymerization adapted to ATRP, respectively, in capillary type stainless steel coiled tube (CT) microreactors. Coil flow inversion (CFI) was introduced to achieve better mixing and narrower residence time distributions during polymerization. This strategy was adopted to improve control over macromolecular characteristics and polymer architecture. Polydispersity index (PDI), as an overall indicator of control over polymerization, was significantly lower for CFI in the case of linear PDMAEMA, 1.39 compared to 1.53 for CT. For branched polymers containing up to 10 mol % of inimer, a reduced PDI was also obtained for CFI microreactor. As for the branching efficiency, it was found to follow the following trend CFI > CT > batch reactor. © 2014 American Chemical Society.

Coil flow inversion as a route to control polymerization in microreactors

Analytical solution (AS), as derived in our previous works for isothermal free radical polymerization (FRP), has been extended to nonisothermal conditions in this work. Only one differential equation, i.e., the energy balance equation, was required to calculate temperature profile by stiff solver using AS as input values. The results were compared against numerical solution (NS) of the complete set of ordinary differential equations (ODE) of FRP, 11 ODE for full set of equations (FRP-Full), and 8 ODE for quasi steady state approximation (FRP-QSSA). Two different models, namely Chiu, Carratt, and Soong (CCS) and Achilias and Kiparissides (AK), for implementing the gel/glass/cage effect, were also considered. The results were validated against published results and were found to be in excellent agreement, as well as with NS for all conditions taken. This work proved the versatility, flexibility, and adaptability of AS under all conditions (except for low temperatures) and with various models to simulate gel/glass/cage effect along with nonisothermal conditions. © 2014 American Chemical Society.

Analytical solution of free radical polymerization: Applications-implementing nonisothermal effect

We report on the synthesis of 2-(dimethylamino)ethyl methacrylate by atom transfer radical polymerization (ATRP) in tubular microreactors. Different process parameters, temperature, pressure, and shear rate, were considered to accelerate the reaction. Increase in temperature induced a faster reaction, but controlled nature of ATRP decreased past a threshold value that can be increased up to 95 °C by reducing the residence time. Positive effect of pressure was observed since significant increases in monomer conversion (+12.5 %) and molecular weight (+5,000 g/mol) were obtained. Moreover, polydispersity index was found to decrease from 1.52 at normal pressure to 1.44 at 100 bars. Benefit of pressure was more visible in smaller reaction space (smaller tube diameter). Finally, shear rate has quite an influence on the early stage of the polymerization and is expressed by an increase in the reaction rate. However, the effect was dimed for long residence times. © 2013 Akadémiai Kiadó.

Journal of Flow Chemistry

Atom transfer radical polymerization in continuous microflow: Effect of process parameters

In this work, gel/glass/cage effects using the Achillias and Kiparissides (AK) model has been incorporated in the analytical solution (AS) obtained in our previous work. The AK model is based on the Chiu, Carratt, and Soong (CCS) model and free volume theory. The results of AS matched quite well with the numerical solutions as well as with the experimental data for methyl methacrylate (MMA). Various variables like termination kinetic coefficient, initiator efficiency, macroradicals concentration profile matched with the established published results. The work clearly demonstrates that AS is sufficiently flexible to accommodate gel/glass/cage effects explicitly although it was not primarily derived for these conditions. This extends the practical usage of AS for the whole range of conversion under isothermal conditions. © 2014 American Chemical Society.

Analytical solution of free radical polymerization: Applications- implementing gel effect using AK model

In the present study, photocatalytic oxidation of dye bearing wastewater has been done using iron doped zinc oxide (Fe/ZnO) photocatalyst. Various photocatalysts were synthesized by solution combustion synthesis method, and their structural, morphological, and optical properties were studied using N2 adsorption-desorption, Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analysis, field emission scanning electron microscope, transition electron microscope, and UV-visible diffuse reflectance spectra. Effect of various parameters such as the amount of iron doped, calcination temperature, calcination time, pH of the dye solution, catalyst dose, hydrogen peroxide dose, reaction temperature, and initial concentration of the dye solution were optimized. At optimum conditions, more that 71% color removal, 94% dye degradation, and 41% total organic carbon removal was observed for acid red 1 dye solution having an initial concentration of 50 mg/L and initial color of 2730 Pt:Co units. © 2013 American Chemical Society.

Industrial and Engineering Chemistry Research

Photocatalytic oxidation of dye bearing wastewater by iron doped zinc oxide

Chemically functionalized maleic anhydride (MAH)-grafted polypropylene matrix has been used (in place of polypropylene as matrix with compatibilizer) to process banana fiber/chemically functionalized polypropylene (BF/CFPP) composites, without using any compatibilizer and without any fiber modification by Palsule process. Fiber/matrix interfacial adhesion generated, in-situ, due to interactions between BF and the MAH of the CFPP matrix has been established by Fourier transform infrared spectroscopy and scanning electron microscopy. Mechanical properties of the BF/CFPP composites developed by Palsule process with in-situ fiber/matrix interfacial adhesion in this study have been found to be higher than those of the matrix and it increases with increasing amounts of fibers in composites, and are better than properties of literature reported BF/polypropylene composites processed with compatibilizers. Measured modulus of BF/CFPP composites compares well with values predicted by rule of mixtures, Hrisch model, Halpin-Tsai equations and its modified Nielsen version, and with Palsule equation. The feasibility of developing natural fiber/MAH grafted polyolefin composites by Palsule process without using any compatibilizer and without any fiber treatment is demonstrated. © 2013 Taylor and Francis Group, LLC.

Composite Interfaces

Banana fiber/chemically functionalized polypropylene composites with in-situ fiber/matrix interfacial adhesion by Palsule process

Size-tunable polymeric nanoparticles have been successfully produced by a microfluidic-assisted nanoprecipitation process. A multilamination micromixer has been chosen to fabricate continuously nanoparticles of methacrylic polymers. Various operating conditions, such as the polymer concentration, the amount of non-solvent and the characteristics of the raw polymer (molecular weight and architecture: linear vs. branched) have been investigated. Their influences on the final particle size, ranging from 76 to 217 nm, have been correlated to the mechanisms leading to the formation of nanoparticles. In this type of microfluidic device, mixing mainly operates by diffusion mass transfer, helped by hydrodynamic focusing. The effect of micromixing on the size of particles has also been shown experimentally and supported by a computational fluid dynamics (CFD) study. A mixing criterion has been defined and numerically calculated to corroborate the effect of the flow rate of polymer solution on the particles size. An increase in the polymer solution flow rate increases the value of this mixing criterion, resulting in smaller nanoparticles. © 2012 Elsevier Ltd. All rights reserved.

Fulltext

Polymer

Improved size-tunable preparation of polymeric nanoparticles by microfluidic nanoprecipitation

Process Safety and Environmental Protection

Trevor Kletz - Common sense safety star

The present study attempts to screen a number of ionic liquids (ILs) for CO 2 capture and its separation from flue gas mixture based on Hildebrand solubility parameter (δ). Solubility parameters of various ILs have been computed through molecular dynamic simulations in Material Studio. Initially the density and solubility parameters of seven ILs have been validated with experimental values available in the literature and are found to be in close correspondence. A group contribution correlation for δ of IL is developed and expressed as the weighted sum of attractions and repulsions of cation and anion as: δIL2=0.6 δcaδan-0. 2δca2-0.2δan2. This correlation was used to find out the δ values of cation and anion. The solubility parameters of 21 cations and 10 anions have successfully been determined by using δ values of 31 ILs and the correlation. Furthermore, using δ values of 21 cations and 10 anions and the group contribution correlation, the δ values of 210 ILs have been predicted. The δ values obtained by correlation match well with the δ values obtained by direct molecular simulations for twenty seven ILs, suggesting that correlation equation is reliable to predict the δ values of several ILs. Furthermore, comparison of the literature solubility data of different gases in ILs with that of solubility parameters in the present study reveals that the δ values are able to successfully explain the experimental solubility trends. Of all ILs studied, δ values of phosphonium cation based ILs (δ = 20.7-18.3 MPa 0.5) and ILs containing tris(nonafluorobutyl)trifluorophosphate ([bFAP] -) anion (δ = 20.5-18.3 MPa 0.5) are observed to be closer to that of CO 2 (δ = 17.85 MPa 0.5) and are significantly far from that of other flue gases like CH 4, N 2, H 2 and H 2O. Thus, by using the fluorinated anion and phosphonium cation based ILs, CO 2 can be more selectively separated from the major flue gases. © 2012 Elsevier B.V. All rights reserved.