Semi-batch Process Research Articles

Optimal Operating Strategies for Emulsion Polymerization with Chain Transfer Agent

Batch and semibatch emulsion polymerization was investigated with a chain transfer agent (CTA) to optimize key process attributes such as monomer conversion and product properties such as molecular weight and particle size. The test monomer, styrene was polymerized in the presence of the chain transfer agent, n-dodecyl mercaptan, to control the final molecular weight. The process model used for conducting optimization incorporated the nucleation, reaction kinetics, and phase heterogeneity involving the aqueous, monomer droplet and polymer particle phases during the various stages of the reaction. The model developed was able to predict the behavior of emulsion polymerization, while describing the significant effect of CTA on molecular weight distribution (MWD) and polydispersity index (PDI) for both batch and semibatch processes. The optimal operating strategies for the process were developed using reaction temperature and monomer feed rate as process variables to obtain desired process trajectories and p...

Fatty Acid Composition and Stability of Extracted Mackerel Muscle Oil and Oil-Polyethylene Glycol Particles Formed by Gas Saturated Solution Process

Abstract The oil in mackerel muscle was extracted using an environment friendly solvent, supercritical carbon dioxide (SC-CO 2 ) at a semi-batch flow extraction process and an n -hexane. The SC-CO 2 was maintained at a temperature of 45 o C under pressures ranging from 15 to 25 MPa. The flow rate of CO 2 (27 g/min) was constant during the entire 2 h extraction period. The fatty acid composi-tion of the oil was analyzed using gas chromatography (GC). Significant concentrations of eicosapentaenoic acid (EPA) acid and docosahexaenoic acid (DHA) acid were present in the SC-CO 2 extracted oil. The oil extracted using SC-CO 2 exhibited increased stability compared with n -haxane extracted oil. Particles of mackerel oil together with the biodegradable polymer, polyethylene glycol (PEG) were formed using a gas saturated solution process (PGSS) with SC-CO 2 in a thermostatted stirred vessel. Different temperatures (45-55 o C), pressures (15-25 MPa) and a nozzle size 400 µm were used for PGSS with a 1 h reaction time. The stabil -ity of mackerel oil in the particles did not changed significantly.

Intensification of highly exothermic fast reaction by multi-injection microstructured reactor

Microstructured reactors (MSR) with characteristic dimensions below 100μm are warranted to maintain close to isothermal conditions when carrying out quasi-instantaneous highly exothermic reactions. Unfortunately, such small dimensions increase the risk of clogging, create high pressure drop and are costly to number-up. The multi-injection (MI) MSR, where one of the reactants is added stepwise along the reactor length, allows working with larger dimensions (diameter >500μm) while maintaining good temperature control. Herein presented MI-MSR is made of low temperature co-fired ceramics (LTCC) with herringbone mixing structure inside the reactor channels and is shown to mix efficiently in a large range of Reynolds numbers Re=20–130. The cyclization of pseudoionone is studied as a model of a highly exothermic fast reaction. The temperature profiles are characterized by a quantitative infrared thermography. The developed LTCC MI-MSR allows ∼ 8-fold reduction of hot spot temperature as compared to the adiabatic temperature rise. Moreover, ∼500-fold intensification is achieved as compared to the conventional semi-batch process with reduced solvent mass by a factor of 2 while attaining a yield of target product above 98%.

Particle nucleation and growth in seeded semibatch miniemulsion polymerization of hybrid CeO2/acrylic latexes

CeO2/acrylic hybrid coatings with high solids content and with nanoparticle percentages up to 5 wt% have been successfully synthesized by seeded semibatch miniemulsion polymerization process. The droplet nucleation efficiency has been assessed by Capillary Hydrodynamic Chromatography and TEM analysis. The effect of the stability of the miniemulsion, the type of initiator and the number of particles of the seed on the efficiency of the nucleation of the nanodroplets fed has been investigated. It was found that the less stable the hybrid miniemulsion, the higher the diffusion of the monomer out of the droplets and hence, the seed latex particles grew in size. However, the CeO2 nanoparticles did not diffuse out with the monomer and remained in very small droplets that eventually nucleate leading to a bimodal population. When stable miniemulsions were produced by using a polymer as hydrophobe, droplet size increased reducing the number of particles in the seed and monomer diffusion was minimized enhancing nucleation of droplets with larger sizes that produced broad PSDs. Coalescence of droplets was negligible because the size distribution of the nanoceria particles did not change from the seed particles to the final latex. The UV–Vis absorption capacity of the films prepared with increasing the amount of CeO2 increased, but scattering effects were observed at high loading of CeO2 due to the large size of the CeO2 aggregates.

Quality relevant nonlinear batch process performance monitoring using a kernel based multiway non-Gaussian latent subspace projection approach

Multiway kernel partial least squares method (MKPLS) has recently been developed for monitoring the operational performance of nonlinear batch or semi-batch processes. It has strong capability to handle batch trajectories and nonlinear process dynamics, which cannot be effectively dealt with by traditional multiway partial least squares (MPLS) technique. However, MKPLS method may not be effective in capturing significant non-Gaussian features of batch processes because only the second-order statistics instead of higher-order statistics are taken into account in the underlying model. On the other hand, multiway kernel independent component analysis (MKICA) has been proposed for nonlinear batch process monitoring and fault detection. Different from MKPLS, MKICA can extract not only nonlinear but also non-Gaussian features through maximizing the higher-order statistic of negentropy instead of second-order statistic of covariance within the high-dimensional kernel space. Nevertheless, MKICA based process monitoring approaches may not be well suited in many batch processes because only process measurement variables are utilized while quality variables are not considered in the multivariate models. In this paper, a novel multiway kernel based quality relevant non-Gaussian latent subspace projection (MKQNGLSP) approach is proposed in order to monitor the operational performance of batch processes with nonlinear and non-Gaussian dynamics by combining measurement and quality variables. First, both process measurement and quality variables are projected onto high-dimensional nonlinear kernel feature spaces, respectively. Then, the multidimensional latent directions within kernel feature subspaces corresponding to measurement and quality variables are concurrently searched for so that the maximized mutual information between the measurement and quality spaces is obtained. The I2 and SPE monitoring indices within the extracted latent subspaces are further defined to capture batch process faults resulting in abnormal product quality. The proposed MKQNGLSP method is applied to a fed-batch penicillin fermentation process and the operational performance monitoring results demonstrate the superiority of the developed method as apposed to the MKPLS based process monitoring approach.

Phase inversion in emulsions studied by low field NMR

Phase inversion phenomenon is studied using two novel low field NMR-based methods. The first method monitors the variation of the apparent spin-spin relaxation time (T2*) of the emulsions. It is based on the difference of the spin-spin relaxation time of water molecules inside a water droplet and within an aqueous bulk phase. The second method uses a diffusion measurement to distinguish between the water signal from droplets and the bulk. The relative distribution of water in droplets and in bulk can be measured. Moreover, droplet size distribution of water can be determined based on this method. Both methods were tested on the phase inversion of a model emulsion. A semi-batch process was used to perform the emulsification in situ. The information obtained through these methods is correlated to optical microscopy and conductivity measurements. When the phase inversion from w/o to o/w is induced by adding a hydrophilic surfactant to the nonionic Span® 80 the inversion seems to pass a double emulsion state before reaching the o/w state. This is an important observation to a mechanical understanding of the phase inversion.

Reactor Modeling and Recipe Optimization of Ring-Opening Polymerization: Block Copolymers

This paper addresses reactor modeling and recipe optimization of semibatch ring-opening polymerization processes for making block copolymers. Two rigorous reactor models are developed on the basis of the population balance and method of moments, respectively. The complete polymerization process model also includes vapor–liquid equilibrium equations from applying Flory–Huggins theory. The accuracies of both reactor models are validated against historical plant data by adjusting model parameters such as kinetic rate constants. The recipe optimization problem is formulated to design the optimal reactor operating policy to minimize polymerization time and incorporate additional process constraints in accordance with final product properties and process safety requirements. The resulting dynamic optimization problem is translated to a nonlinear program by using the simultaneous collocation method, and further solved by the interior point method. In the case study example, both reactor models show satisfactory matches between their predictions and the historical plant data. The recipe optimization with both models demonstrates significant process improvement and reductions in batch operating time. Moreover, the moment model shows superiority over the population balance model in terms of computational efficiency.

Modification research on the peel strength of the acrylate emulsion pressure‐sensitive adhesives

ABSTRACTPressure‐sensitive adhesives (PSAs) were produced with latexes synthesized via starved semibatch emulsion polymerization processes with butyl acrylate, three different kinds of hard monomers [styrene (St), methyl methacrylate, and 2‐phenoxy ethyl methacrylate (SR340)], acrylic acid, and 2‐hydroxy ethyl acrylate. The management of both the copolymer composition and the polymerization process allowed us to control the behavior of the PSAs. For the acrylate latexes, the types of hard monomers and their contents, the concentration of buffer [bicarbonate (NaHCO3)], and three kinds of semibatch processes were manipulated to modify the polymer properties. The performance of the PSA films cast from these latexes was evaluated by the peel strength. The results show that the PSA prepared with St exhibited the highest peel strength among the three hard monomers, and the latex synthesized by SR340 showed the largest gel content compared with the other two hard monomers. With increasing buffer, the latex particle size increased, and the peel strength initially increased to a maximum and then decreased. Nevertheless, the stability of the latexes decreased with increasing buffer concentration. In addition, the effects of the three kinds of semibatch processes on the peel strength of the PSA were also evaluated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40095.

Statistical theory for self-condensing vinyl polymerization system with any initial distribution

A generation function method is used to obtain some average polymer physical quantities in the self-condensing vinyl polymerization (SCVP) system with any initial distribution. For the system under study, the generation function is explicitly derived in terms of the corresponding differential kinetic equations. As an application, two SCVP systems with uniform and dispersed prepolymers were discussed, respectively. As a result, the number-, weight- and Z-average degrees of polymerization and polydispersity index were presented. It is shown that, on the one hand, the initial distribution plays an important role in these physical quantities, and on the other hand, the generation function method is found to be very convenient in the calculations of average polymer quantities. It is expected that the present method can be applied in more complex SCVP systems with such as semi-batch process, multi-components and unequal reactivity.

An integrated approach to active model adaptation and on-line dynamic optimisation of batch processes

In the application of on-line, dynamic process optimisation, adaptive estimation of the system states and parameters is usually needed to minimise the unavoidable model-process mismatch. This work presents an integrated approach to optimal model adaptation and dynamic optimisation, with specific focus on batch processes. An active approach is proposed whereby the input variables are designed so as to maximise the information content of the data for optimal model adaptation. Then, this active adaptation method is combined with the objective of process performance to form a multi-objective optimisation problem. This integrative approach is in contrast to the traditional adaptation method, where only the process performance is considered and adaptation is passively carried out by using the data as is. Two strategies for solving the multi-objective problem are investigated: weighted average and constrained optimisation, and the latter is recommended for the ease in determining the balance between these two objectives. The proposed methodology is demonstrated on a simulated semi-batch fermentation process.

Emulsion Semi-Batch Terpolymerization Process Using Hybrid Emulsifiers for Synthesizing New Emulsion Pressure Sensitive Adhesives (EPSAs)

In order to obtain a suitable formulation of designing direct synthesis of acrylic latexes to be used as emulsion pressure sensitive adhesives (EPSA), having high shear resistance together with high peel strength and tack, free radical emulsion polymerization of hard monomers, such as styrene (St), vinyl acetate monomer (VAM), methyl methacrylate (MMA) and butyl methacrylate (BMA), and soft monomers, butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA) along with multifunctional monomers, namely acrylic acid (AA), were carried out. The effect of the type of hard and soft acrylic monomers, the type and level of emulsifiers, and the initiator concentration on the emulsion polymer stability and final properties of the EPSA were investigated. The results obtained showed an optimized composition. This composition led to a significant increase in shear strength and peel strength to 909 kPa and 0.45 N/mm, respectively, while the synthesized PSA was still too tacky, 5.5 cm, according to adhesion performance testing. For making this successful balance of the conflicting adhesion properties of PSA, a series of anionic and nonionic emulsifiers were investigated. It was interestingly found out that the hybrid emulsifiers (anionic coupling with nonionic) with the optimized compositions could enhance the stability of the emulsion system and improve the properties of PSA compared with the mono-emulsifier. We also tried to adjust the initiator concentration with the level of the optimized hybrid emulsifier, polyoxyethylene alkyl phenyl ether (K30), dioctyl sulfosuccinate (DOSS), and sodium vinyl sulfonate (SVS) with the ratio 2:1:1, resulting in a highly preferred proportion of the 0.5 part of the initiator versus 1.25 parts of the hybrid emulsifier in terms of the total weight of the monomers.

Permeate recovery and flux maximization in semibatch reverse osmosis

Most reverse osmosis (RO) and nanofiltration (NF) processes operate as once through or plug flow (PF) systems in which permeate recovery, flux and cross-flow are coupled. Such processes are well suited for applications where permeate recovery percentages are limited and where well pretreated source waters of uniform composition are available. Some membrane filtration applications, such as ultrafiltration, operate as batch systems. Batch operations allow independent manipulation of permeate recovery, flux and cross-flow, and are therefore well suited for high recovery and/or problematic source waters. However, the application of batch operation to RO and NF has been limited because of the increase in energy requirements and reduction in permeate quality that can result. In addition, batch systems can require higher capacity components and more membrane elements and housings than comparable continuous or plug flow systems to compensate for downtime between batches. New semibatch or continuous batch processes for RO or NF applications are emerging. These processes provide high adjustable recovery rates, independently adjustable cross-flow and resistance to and even reversal of fouling and scaling. They can consume less energy and require fewer membrane elements than PF systems. High recovery operation reduces both concentrate production and source water pumping and pretreatment requirements. High cross-flow, reduced lead element flux, more even flux distribution and salinity cycling can reduce the effects of fouling and scaling and the associated chemical and cleaning requirements. These features are particularly beneficial for inland desalination, wastewater concentration and water reuse applications. This paper considers process designs and projected membrane performance of semibatch RO systems for brackish and low salinity source waters. The potential advantages of new process design features that can be employed in batch RO but are not practical for conventional RO, such as short membrane arrays and high recovery single stage designs, are evaluated. Particular focus is given to the operating conditions and performance of individual membrane elements in multi-element membrane arrays. Comparisons are made to the performance of conventional PF RO designs. The analysis will help engineers of RO and NF systems to understand the new capabilities, optimization considerations and potential new applications for this emerging process technology.

Osmotically driven membrane process for the management of urban runoff in coastal regions

An osmotic detention pond was proposed for the management of urban runoff in coastal regions. Forward osmosis was employed as a bridge to utilize natural osmotic energy from seawater for concentrating and reusing urban runoff water, and as a barrier to reject runoff-derived contaminants. The process was demonstrated by a lab scale testing using synthetic urban runoff (as the feed solution) and synthetic seawater (as the draw solution). The submerged forward osmosis process was conducted under neutral, acidic and natural organic matter fouling condition, respectively. Forward osmosis flux decline was mainly attributed to the dilution of seawater during a semi-batch process in lab scale testing. However, it is possible to minimize flux decrease by maintaining a constant salinity at the draw solution side. Various changes in urban runoff water quality, including acidic conditions (acid rain) and natural organic matter presence, did not show significant effects on the rejection of trace metals and phosphorus, but influenced salt leakage and the rejection of nitrate and total nitrogen. Rejection of trace metals varied from 98% to 100%, phosphorus varied from 97% to 100, nitrate varied from 52% to 94% and total nitrogen varied from 65% to 85% under different feed water conditions. The work described in this study contributes to an integrated system of urban runoff management, seawater desalination and possible power generation in coastal regions to achieve a sustainable solution to the water-energy nexus.

Industrial Production of Poly Vinyl Acetate Dispersions: Relationship Between Latex Properties and Polymerization Start-Up Temperature

An industrial polymerization process for the production of polyvinyl alcohol stabilized polyvinylacetate dispersions has been examined to investigate the influence of the start-up temperature on production process and latex characteristics. The product investigated is a high solids, high viscosity latex, obtained by a semi-batch emulsion polymerization process, initiated with persulfate. The main finding shows that small variations of the start-up temperature affect the reaction kinetics in the first stage of polymerization and have a direct influence on physicochemical and rheological properties of the finished products.

In Situ Attenuated Total Reflectance Fourier Transform Infrared (ATR FT-IR) Spectroscopy Monitoring of 1,2-Butylene Oxide Polymerization Reaction by Using Iterative Concentration-Guided Classical Least Squares

There has been rapid growth in the application of in situ optical spectroscopy techniques for reaction and process monitoring recently in both academia and industry. Vibrational spectroscopies such as mid-infrared, near-infrared spectroscopy, and Raman spectroscopy have proven to be versatile and informative. Accurate determination of concentrations, based on highly overlapped spectra, remains a challenge. As an example, 1,2-butylene oxide (BO) polymerization, an important industrial reaction, initiated by propylene glycol (PG) and catalyzed by KOH, is studied in this work in a semi-batch fashion by using in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) monitoring. The weak BO absorbance, the constantly changing interference from the product oligomers throughout the course of the reaction, and the change in BO spectral features with system polarity posed challenges for quantitative spectral analysis based on conventional methods. An iterative concentration-guided classical least-squares (ICG-CLS) method was developed to overcome these challenges. Taking advantage of the concentration-domain information, ICG-CLS enabled the estimation of the pure oligomer product spectra at different stages of the semi-batch process, which in turn was used to construct valid CLS models. The ICG-CLS algorithm provides an in situ calibration method that can be broadly applied to reactions of known order. Caveats in its applications are also discussed.

High‐Solids‐Content Hybrid Acrylic/CeO2 Latexes with Encapsulated Morphology Assessed by 3D‐TEM

Hybrid acrylic/CeO2 latexes with solids content as high as 50 wt% and CeO2 content up to 1 wt% are synthesized by a seeded semibatch emulsion polymerization process. TEM images show that CeO2 nanoparticles are randomly located within the polymer particles. The 2D trasmission electron microscopy (TEM) images are not conclusive to elucidate if CeO2 is encapsulated in the hybrid polymer particles. A TEM tomographic analysis is presented here to assess their morphology. The study shows that the latexes synthesized present an encapsulated morphology for CeO2 nanoparticles regardless of whether these are located at the center or borders of the polymer particles. image

Reactor modeling and recipe optimization of polyether polyol processes: Polypropylene glycol

The reactor modeling and recipe optimization of conventional semibatch polyether polyol processes, in particular for the polymerization of propylene oxide to make polypropylene glycol, is addressed. A rigorous mathematical reactor model is first developed to describe the dynamic behavior of the polymerization process based on first‐principles including the mass and population balances, reaction kinetics, and vapor‐liquid equilibria. Next, the obtained differential algebraic model is reformulated by applying a nullspace projection method that results in an equivalent dynamic system with better computational performance. The reactor model is validated against plant data by adjusting model parameters. A dynamic optimization problem is then formulated to optimize the process recipe, where the batch processing time is minimized, given a target product molecular weight as well as other requirements on product quality and process safety. The dynamic optimization problem is translated into a nonlinear program using the simultaneous collocation strategy and further solved with the interior point method to obtain the optimal control profiles. The case study result shows a good match between the model prediction and real plant data, and the optimization approach is able to significantly reduce the batch time by 47%, which indicates great potential for industrial applications. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2515–2529, 2013

Classification and optimization of potentially runaway processes using topology tools

Fast and strongly exothermic reactions can exhibit a well-known phenomenon called “thermal runaway”. To identify high productivity and safe conditions for these reactions, with particular reference to industrial semibatch processes carried out using both isothermal and isoperibolic temperature control mode, a dedicated classification/optimization software has been implemented. This software is able to both classify a set of operating parameters from the thermal stability viewpoint and identify the optimum reacting/synthesis conditions using a topological criterion that binds the so-called “QFS region”, where reactants accumulation is low and all the heat released is readily removed by the cooling equipment. During the search for system optimum a number of safety and quality constraints can be taken into account. The software reliability, in terms of both classification and optimization ability, has been tested using both laboratory and industrial scale experimental data. Obtained results confirm a good agreement between theoretical predictions and experimental evidence.

Thermal behaviour of binary and ternary copolymers containing acrylonitrile

Three types of acrylonitrile copolymers (acrylonitrile-styrene-butadiene copolymer (ABS11Acrylonitrile-styrene-butadiene copolymer.), acrylonitrile-styrene random copolymer (SAN22Acrylonitrile-styrene random copolymer.) and acrylonitrile-butadiene random copolymer (BAN33Acrylonitrile-butadiene random copolymer.) were studied by thermogravimetry (TG/DTG44Thermogravimetry.) and by pyrolysis in a semi-batch process at 450 °C in order to find structure–thermal behaviour relationships. The overlapped thermo-oxidative degradation processes were separated and the corresponding kinetic parameters were calculated. The TG/DTG studies have evidenced that the styrene-acrylonitrile interactions stabilize the nitrile groups reacting by chain scission rather than cyclization and destabilize the styrene units. Also, the cyclization of the acrylonitrile units in ABS is favoured by interactions with the styrene and butadiene units. The pyrolysis behaviour evidenced that the styrene-acrylonitrile interactions in SAN and ABS lead to the formation of 4-phenylbutyronitrile as the most important decomposition compound. ABS shows similar composition of the degradation oil with SAN copolymer therefore in the ABS the styrene-butadiene interactions are less important than those between styrene and acrylonitrile units.

TEMPO Mediated Radical Emulsion Polymerization of Styrene by Stepwise and Semibatch Processes

AbstractIn the present study we carried out nitroxide mediated radical polymerizations (NMRP) of styrene in emulsion using 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) by stepwise and semibatch processes obtaining polystyrene (PS) with a dispersity (Đ) lower than 1.5 and average particle diameter (Dp) between 180 and 520 nm when methanol was used. Otherwise, when the polymerization was carried out in the absence of methanol, a bimodal particle size distribution (PSD) was obtained. This is attributed to the super‐swelling effect, which causes the particles to grow considerably and also to lower the nitroxide efficiency reducing chain formation and thus drastically reducing the particle nucleation. These polymerizations did not require a separate macroinitiator synthesis step, which represents an important simplification for further applications.