Macromolecular Reaction Engineering最新文献

Low salinity water–polymer flooding (LSWPF) is an emerging hybrid enhanced oil recovery (EOR) method that uses the synergetic effects of low salinity water (LSW) and polymers to enhance both the microscopic and macroscopic sweep efficiencies. Polymer flooding is an EOR method that aims to increase water viscosity and improve the mobility ratio of the injected fluid to the reservoir. It enhances mobility control and reduces water relative permeability, reaching a more favorable condition for sweep efficiency. LSW is an EOR method that aims to change wettability by exploiting crude oil and reservoir rock interactions. It allows for improving oil recovery when the injected water has a very low salinity compared to seawater or formation water. The literature reports LSWPF studies applied to sandstone reservoirs. However, LSWPF applications in carbonate reservoirs still lack. This review critically analyzes LSWPF as an alternative to Polymer flooding using seawater in carbonate reservoirs.

Three ω-alkenyltrimethylsilanes of different alkenyl moieties, i.e., 3-butenyltrimethylsilane, 5-hexenyltrimethylsilane, and 7-octenyltrimethylsilane, are copolymerized with propylene over a heterogeneous Ziegler-Natta catalyst. The experimental results reveal that, at odds with what the molecular volumes will foretell, 5-hexenyltrimethylsilane top the three ω-alkenyltrimethylsilanes in incorporation rate into PP while 3-butenyltrimethylsilane becomes the most sluggish of the three. This comonomer incorporation rate order is in line with that of ω-alkenylmethyldichlorosilanes in copolymerization with propylene-synthesizing long-chain-branched PP (LCB-PP), pointing to a peculiar alkenyl length effect on comonomer incorporation rate for these comonomers. DFT simulation is then applied to seek energetic basis in coordination-insertion for such an effect. It is revealed that complexation abilities of the three ω-alkenyltrimethylsilanes decrease in the following order: 3-butenyltrimethylsilane > 5-hexenyltrimethylsilane > 7-octenyltrimethylsilane, in line with their molecular sizes. However, the insertion energy barriers increase in the order of: 5-hexenyltrimethylsilane < 7-octenyltrimethylsilane < 3-butenyltrimethylsilane. The repulsive interaction between the bulky trimethylsilane functionality of ω-alkenyltrimethylsilanes and growing PP chain is found to contribute significantly to the insertion energy barrier, which grows disproportionally large with 3-butenyltrimethylsilane. The current discovery will be conducive to understanding the more complex ω-alkenylmethyldichlorosilane/propylene copolymerization that synthesizes the industrially important LCB-PP.

Oxaliplatin and modified magnetic nanoparticles (magnetite-lysine) are inserted into microspheres of previously synthesized poly(lactic acid-co-glycolic acid-b-ethylene glycol) PLGA-PEG to evaluate the in vitro hyperthermal potential and the acute toxicity in mice. The used nanoparticles are synthesized by the coprecipitation method, using Fe II and Fe III, and modification with lysine is performed during the synthesis. The drug and the magnetic nanoparticles are inserted into the polymer beads through oil in water (O/W) emulsion. The obtained composites are then characterized by Fourier-transform infrared (FTIR), Thermogravimetric analysis (TGA), X-ray Diffraction (XRD), and submitted to magnetic hyperthermia and acute toxicity tests. The hyperthermia tests are conducted according to an experimental design. The magnetite-lysine nanoparticles reached the temperature for the desired application and are able to raise the temperature by 6 °C at the higher investigated current, time, and concentration conditions. According to the proposed statistical study, only the test time exerted significant positive influence on the observed temperature increase, although synergies between time and concentration and between current and concentration are also significant. In vivo acute toxicity tests are also conducted with swiss mice and revealed that the prepared materials and procedures can be regarded as safe and of low toxicity.

The iron-containing imidazolium-based ionic liquids (ILs) 1-n-butyl-3-methylimidazolium heptachlorodiferrate (BMI.Fe₂Cl₇) and 1-n-butyl-3-methylimidazolium tetrachloroferrate (BMI.FeCl₄) are applied as catalysts in the homogeneous polymerization of n-butyl vinyl ether. Both solventless conditions as well as using different organic solvents, catalyst concentrations, temperatures, and reaction times are tested to assess the polymerization conditions that lead to the highest molecular weights of poly(n-butyl vinyl ether). The Lewis acidic IL BMI.Fe₂Cl₇ proves to be highly efficient, even at low catalyst concentrations. In bulk polymerization, polymers with 142 kg mol⁻¹ are obtained using a 1:10000 molar ratio of catalyst to monomer. In solution polymerization, the monomer consumption is also rapid and the molecular weight of the polymer is related to the catalyst concentration used. These results indicate the potential of this catalyst for industrial applications. In contrast with the acidic IL, the neutral iron-containing imidazolium-based IL BMI.FeCl₄ does not show any catalytic activity.

A detailed mathematical model of the propylene-1-hexene copolymerization based on the two-dimensional probability generation function technique is developed. It calculates the joint molecular weight-copolymer composition distribution (MWD-CCD) of the copolymer, as well as the average copolymer composition distribution, the molecular weight distribution (MWD), the copolymer composition distribution (CCD), average molecular weights and composition, and yield. The parallelized execution of the model code allows for obtaining the different copolymer microstructure distributions efficiently. The model allows for reaching a thorough understanding of the copolymer microstructure under different operating conditions of a semibatch reactor. It also has the potential to become a powerful tool for selecting operating conditions to obtain a material with target molecular properties.

Front Cover: Microreactor parts made of stainless steel are modified by a chemically inert ultra-thin sol-gel film which combines ultra-low surface energy with a smoothening of the surface by preferential coating accumulation in surface rifts. The applied films lead to a significant inhibition of polymer deposit formation as well as to an extended operating time of microreactors employed during aqueous polymerization of poly(vinylpyrrolidone). This is reported by Guido Grundmeier and co-workers in article number 2200043.

In the present paper, a dynamic optimization problem regarding grade transitions in bulk poly(propylene) polymerization processes is formulated and solved for the first time. Initially, a detailed dynamic process model is presented and implemented, comprising mass and energy balances, some of the polymer properties (such as the melting flow index and the xylene solubles) and regulatory control loops. Additionally, the effects of cocatalyst and electron donor on the propagation rate constant are taken into account. Then, the dynamic optimization problem is formulated and an evolutionary algorithm is used to solve the resulting nonlinear programming problem. It is shown that there is significant coupling among the manipulated variables and the controlled performance and polymer property variables, which adds complexity to the grade transition problem and demands the simultaneous manipulation of multiple variables during transitions. Despite the inherent open-loop unstable nature of the analyzed process, it is shown that smooth grade transition trajectories can be accomplished through proper adjustment of the objective function weights. Finally, it is shown that the obtained optimum trajectories can significantly diminish the transition time, which can be of paramount importance for the plant economics.

To predict the polymer properties produced by free-radical polymerization of N-vinylpyrrolidone (NVP) in aqueous solution a detailed kinetic model has been developed. The kinetic model allows to calculate the chain length distribution, the number of branching points, and the number of terminal double bonds (TDB). The latter is accounted for since TDBs are a precondition for branching. While monomer conversion can be predicted sufficiently using independently determined rate constants for propagation and termination, here the predictions of structural properties by a newly developed extended kinetic model to experimental findings are compared. Polymer produced in a continuous stirred tank reactor is analyzed by gel permeation chromatography (GPC), field flow fractionation (FFF), and high-pressure liquid chromatography (HPLC).

In this work, polymeric microspheres based on glycidyl methacrylate and divinylbenzene with magnetic properties are synthesized by the suspension polymerization technique. To obtain magnetic properties, magnetite particles modified by oleic acid are synthesized in the laboratory. The effects of stirring speed, concentration of magnetite added, and concentration of stabilizer on the particles’ properties are studied. The magnetic microspheres are characterized according their morphology, magnetite incorporation, and magnetic and thermal properties. The incorporation of iron particles is mainly affected by stirring speed during synthesis and the amount of added magnetic material. The saturation magnetization of the microspheres is affected by the content of incorporated magnetic material. The modification with oleic acid is important for incorporation of the magnetic material in the copolymer matrix. Polymeric particles with superparamagnetic behavior are obtained with spherical morphology and saturation magnetization of 7.11 (emu g⁻¹) when employing a monomer molar ratio of 50/50, 1% poly(vinyl alcohol), 20% magnetite particles modified by oleic acid, and stirring speed of 500 rpm.