Integration of molecular dynamic simulation and free volume theory for modeling membrane VOC/gas separation

Molecular simulations: From fundamental principles to applications in gaseous pollutant control

Removing gaseous pollutants from the environment is crucial for mitigating air pollution and safeguarding public health. Conventional laboratory methods for gaseous pollutant removal face significant challenges, including complex experimental setups, limited scalability, and difficulties in capturing molecular-level interactions under real-world conditions. Molecular simulations have emerged as a powerful tool to address these issues, with ongoing research focusing on improving computational efficiency and force field accuracy to model diverse pollutants and materials. These methods predict the absorption properties of gaseous pollutants, offering detailed insights at the molecular level that are challenging to achieve experimentally. This research begins by discussing the theory underlying molecular simulation methods, highlighting their relevance in understanding gas-solid interactions. Various absorbents' physical and chemical properties are analyzed, focusing on their effectiveness in trapping and neutralizing harmful gases. The study also examines the influence of molecular simulations in determining key transfer properties, such as permeability, solubility, and selectivity, which enhance the design and optimization of absorbent materials. The importance of this research lies in its potential to predict the removal efficiency of gaseous pollutants, providing valuable tools for developing effective pollution control strategies. This approach advances the understanding of gas absorption mechanisms and profoundly impacts the development of innovative solutions for environmental protection. By reviewing past achievements, present applications, and future directions, this article underscores the transformative role of molecular simulations in accelerating the development of novel materials for efficient gaseous pollutant control.

Molecular Dynamics Simulation on Structure and Dielectric Permittivity of BaTiO3/PVDF Composites

Molecular dynamics (MD) simulation was performed to investigate the structure and dielectric permittivity of poly(vinylidene fluoride)- (PVDF-) based composites with different contents of barium titanate (BT). The β-phase PVDF model with 100 structural units and the spherical BT particle model with a radius of 0.495 nm were built and applied in the initial models with three PVDF macromolecular chains and BT particles for the MD simulations of the BT/PVDF composites. The influences of BT content on the morphological structure, the free volume fraction, and glass transition temperature of the composites were explored according to the simulated results and the experimental ones of X-ray diffraction (XRD) and scanning electron microscope (SEM). A model was proposed to predict the static dielectric permittivity of the composites, the results of which were compared with the Cole-Cole fitting results of dielectric spectroscopy. Attempts were made to reveal the structure evolution and the micropolarization mechanism with the increasing content of BT.

Conceptual Design of Pyrolytic Oil Upgrading Process Enhanced by Membrane-Integrated Hydrogen Production System

Hydrotreatment is an efficient method for pyrolytic oil upgrading; however, the trade-off between the operational cost on hydrogen consumption and process profit remains the major challenge for the process designs. In this study, an integrated process of steam methane reforming and pyrolytic oil hydrotreating with gas separation system was proposed conceptually. The integrated process utilized steam methane reformer to produce raw syngas without further water–gas-shifting; with the aid of a membrane unit, the hydrogen concentration in the syngas was adjusted, which substituted the water–gas-shift reactor and improved the performance of hydrotreater on both conversion and hydrogen consumption. A simulation framework for unit operations was developed for process designs through which the dissipated flow in the packed-bed reactor, along with membrane gas separation unit were modeled and calculated in the commercial process simulator. The evaluation results showed that, the proposed process could achieve 63.7% conversion with 2.0 wt% hydrogen consumption; the evaluations of economics showed that the proposed process could achieve 70% higher net profit compared to the conventional plant, indicating the potentials of the integrated pyrolytic oil upgrading process.