Description of phase equilibrium and volumetric properties for CO2+water and CO2+ethanol using the CPA equation of state

The Phase Distribution Characteristics and Interphase Mass Transfer Behaviors of the CO2-Water/Saline System under Gathering and Transportation Conditions: Insights on Molecular Dynamics

In order to investigate the interphase mass transfer and component distribution characteristics of the CO2-water system under micro-scale and nano-scale transport conditions, a micro-scale kinetic model representing interphase mass transfer in the CO2-water/saline system is developed in this paper. The molecular dynamics method is employed to delineate the diffusion and mass transfer processes of the system's components, revealing the extent of the effects of variations in temperature, pressure, and salt ion concentration on interphase mass transfer and component distribution characteristics. The interphase mass transfer process in the CO2-water system under transport conditions can be categorized into three stages: approach, adsorption, and entrance. As the system temperature rises and pressure decreases, the peak density of CO2 molecules at the gas-liquid interface markedly drops, with their aggregation reducing and their diffusion capability enhancing. The specific hydration structures between salt ions and water molecules hinder the entry of CO2 into the aqueous phase. Additionally, as the salt concentration in water increases, the density peak of CO2 molecules at the gas-liquid interface slightly increases, while the density value in the water phase region significantly decreases.

Phase equilibria modeling of biorefinery-related systems: a systematic review

The search for sustainable ideas has gained prominence in recent decades at all levels of society since it has become imperative an economic, social, and environmental development in an integrated manner. In this context, biorefineries are currently present as the technology that best covers all these parameters, as they add the benefits of waste reuse, energy cogeneration, and fossil fuel substitution. Thus, the study of the various applicable biological matrices and exploring the technical capabilities of these processes become highly attractive. Thermodynamic modeling acts in this scenario as a fundamental tool for phase behavior predictions in process modeling, design, and optimization. Thus, this work aimed to systematize, using the PRISMA statement for systematic reviews, the information published between 2010 and 2020 on phase equilibria modeling in systems related to biorefineries to organize what is already known about the subject. As a result, 236 papers were categorized in terms of the year, country, type of phase equilibria, and thermodynamic model used. Also, the phase behavior predictions of different thermodynamic models under the same process conditions were qualitatively compared, establishing PC-SAFT as the model that best represents the great diversity of interest systems for biorefineries in a wide range of conditions.

Impact mechanisms of supercritical CO2-ethanol-water on extraction behavior and chemical structure of eucalyptus lignin

A compounded medium of supercritical CO₂, ethanol, and water (SEW) was used to extract lignin from eucalyptus fiber and the mechanism of the extraction was studied. Compared with the extraction method based on high-temperature ethanol (HTE), the lignin yield of the SEW method was 49.7% higher with higher average molecular weight. Physical and chemical synergies occurred during the extraction process. SEW compound medium penetrated eucalyptus fiber cell walls because of strong permeability, while the fast discharge of the compounded medium facilitated efficient lignin dissociation and removal. Carbonic acid formed from CO₂ and water under high temperature and pressure can provide an acidic environment to effectively degrade hemicellulose. Formaldehyde formed from CO₂ and ethanol in the process also prevented condensation of the extracted lignin fragments. The obtained lignin had high content of β-O-4 linkages and syringyl units.