Jian-Zhong Yin

Modeling of supercritical fluid extraction from Hippophae rhamnoides L. seeds

Modeling of supercritical CO2 extraction of Hippophae rhamnoides L. seed oil was studied at 15 to 30 MPa and 30 to 45°C. Four mean Hippophae rhamnoides L. particle sizes raging from 0.4 to 1.0 mm were tested. CO2 flow rate ranged between 0.05 and 0.2 m3 h− 1. A new method that can be used for the simulation of SCFE process was presented. The model was based on differential mass balances along the extraction bed. The equilibrium between the solid and the fluid phase appeared to be the controlling step during the extraction fast period. By a series of transforms and derivatives, the explicit expression of the oil yield, q(z,t), was obtained. It can be used for the SCFE process simulation. In this model, only one adjustable parameter was used: the equilibrium constant between the solvent and the free solute phase, K. A fairly good fitting of the experimental data was obtained by setting K = 10. The Hippophae rhamnoides L. seed oil extraction process was modeled as a desorption process from the seed matter plus a small mass‐transfer resistance.

Phase Behavior of Supercritical CO2 Microemulsion with AOT and its Solubilization Properties of 1,3-propanediol

The phase behaviors of three microemulsion systems were studied in a custom-made volume-variable view cell, including the ternary system of CO2/EtOH (ethanol)/1,3-PDO (1,3-propanediol), quaternary system of CO2/EtOH/H2O/1,3-PDO and quinary system of AOT/CO2/EtOH/H2O/1,3-PDO, using 1,3-PDO as the model compound, AOT (sodium bis(2-ethylhexyl) sulfosuccinate) as surfactant and ethanol as co-solvent in the CO2 continuous phase. The phase behaviors of the AOT/CO2/EtOH/H2O/1,3-PDO quinary system were mainly discussed in the temperature range of 29.1°C–44.3°C and pressure range of 6.41 MPa-15.95 MPa. The result shows that a thermodynamically stable microemulsion can be formed by controlling the operating pressures and temperatures, which can provide basic thermodynamics data for industrial design and proper operating conditions for selectively solubilizing 1,3-PDO from dilute aqueous solution.

Impregnation of ionic liquids in mesoporous silica using supercritical carbon dioxide and co-solvent

Ionic liquids (ILs) have been considered to be attractive alternatives for CO2 capture. The impregnation of ILs on porous substrates can significantly reduce the ILs consumption, enhance the mass transfer of CO2 in the ILs and make their recycling easier. However, due to the high viscosity of the ILs, the impregnated ILs were often poorly dispersed on the substrates or blocked the nanochannels when the traditional impregnation method was used. In this study, a new, effective and environmentally benign technique to impregnate ILs onto mesoporous substrates was proposed. The impregnation of [Bmim]BF4 on SBA-15 was successfully achieved using supercritical carbon dioxide (scCO2) as the solvent and methanol as co-solvent. The ILs were proved to be impregnated into the nanochannels rather than on the outside of the substrate by N2 adsorption–desorption and SEM analysis. The operating pressure, temperature and time were investigated to find out the optimum parameter to synthesis these nanocomposites. Finally, the CO2 adsorption capacity of the ILs@SBA-15 composites was performed on a dynamic adsorption apparatus.

Direct growth of highly dispersed MnCl2 · 4H2O nanostructures with different morphologies on graphene in supercritical CO2

Willow leaf-like Mn3O4 nanoplates@graphene nanocomposites were synthesized using graphene instead of graphene oxide as initial materials with the assistance of supercritical CO2. The near-zero surface tension and the gas-like viscosity of supercritical CO2 favored the intercalation and dispersion of precursors among the graphene nanosheets. In addition, MnCl2 4H2O ultra-small nanoparticles with diameter of 1–3 nm were supported on graphene using MnCl2 4H2O as precursor, supercritical CO2 as solvent and methanol as co-solvent under very moderate conditions. It was also found that the specific capacitance of the MnCl2 4H2O ultra-small nanoparticles@graphene with a metal loading of only 12.4% was twice that of pure graphene. In addition, the capacitance retention ratio of the MnCl2 4H2O ultra-small nanoparticles@graphene composite decreased by only 5.4% when the cycle number increased from 200 to 1000.

Selective solubilization of 1,3-propanediol using a water–supercritical CO2 microemulsion with Ls-45 as surfactant

In order to purify the fermentation broth efficiently, this paper focuses on solubilizing polyalcohols from their dilute aqueous solution using a supercritical CO2 microemulsion (W–C microemulsion). The phase behavior of four systems was studied, including Ls-45/CO2, Ls-45/CO2/H2O, Ls-45/CO2/1,3-propanediol (1,3-PDO), and Ls-45/CO2/H2O/1,3-PDO, with 1,3-PDO dilute aqueous solution used to simulate the real fermentation broth, supercritical CO2 (scCO2) as the continuous phase, and the non-fluorous and non-silicon non-ionic Ls-45 as surfactant. The effects of Ls-45 concentration and 1,3-PDO concentration on the selective solubilization of 1,3-PDO in the Ls-45/CO2/1,3-PDO/H2O quaternary system are discussed at temperatures of 29.5–49.9 °C and at pressures of 7.22–19.27 MPa. The results show that a thermodynamically stable microemulsion can be formed by controlling the operating pressure and temperature and can selectively solubilize 1,3-PDO from its dilute aqueous solution. Both the Ls-45 concentration and 1,3-PDO concentration in the system have great influence on the selectivity of solubilzing 1,3-PDO from dilute aqueous solution. Moreover, it is found that the addition of ethanol (EtOH) can significantly decrease the operating pressure of forming the W–C microemulsion system. This result is useful for further research on the selective extraction of polyalcohols in biotechnology and helpful for industrialization.

Molecular dynamics simulations of CO2 permeation through ionic liquids confined in γ-alumina nanopores

Abstract CO2 permeation through imidazolium-based ionic liquids (ILs, [BMIM][Ac], [EMIM][Ac], [OMIM][Ac], [BMIM][BF4], and [BMIM][PF6]) confined in 1.0, 2.0, and 3.5 nm γ-alumina pores was investigated using molecular dynamics simulation. It was found that the nanopore confinement effect influenced the structure of confined ILs greatly, resulting in a layered structure and anisotropic orientation of ILs. In the center of 2.0-nm pore, the long alkyl chain of [BMIM]+ tended to be parallel to the wall, providing a straight diffusion path benefiting the CO2 permeation. The CO2 diffusion coefficients in confined [EMIM][Ac], [BMIM][Ac], and [OMIM][Ac] were 2.3–4.1, 2.4–6.4, and 14.4–21.7 × 10−10 m2 s−1, respectively. This order was opposite to that in the bulk ILs, because the longer alkyl chain led to a more ordered structure, facilitating CO2 diffusion. In addition, the CO2 solubilities were 445–722 mol m−3 MPa−1 for the five ILs confined in 1.0 nm pore, which were larger than those in 2.0 and 3.5 nm pores (196–335 mol·m−3 MPa−1), due to the larger free volume. Both parallel orientation of alkyl chain and large free volume could increase the CO2 permeability in confined ILs.

SIMULATION OF SOLID–LIQUID SUSPENSION AND SCALE-UP OF AGAROSE GEL ACTIVATION REACTOR

Agarose gel activation reaction, which is of great importance in preparing the carrier of the column packing material for blood purification, would be significantly influenced by the configuration and parameter of reactor. In order to optimize the structure design of the reactor and operating parameters of the process, the characteristics of suspension system composed of agarose gel, NaOH, water, 3-allyl bromide, and activated alumina were simulated numerically utilizing an Eulerian multiphase flow model and multi-reference frame (MRF) approach. The effect of impeller configuration was studied with three typical impellers, including Rushton disk turbine (DT), pitched blade downflow turbine (PBTD45), and pitched blade upflow turbine (PBTU45). The results showed that the optimum solid suspension was obtained using PBTD45 impeller with a diameter of 100mm and critical suspension speed of 570rpm in a 20L stirred reactor. In addition, the critical suspension speeds using the three impellers were calculated and the errors were all within the engineering allowance. Finally, the feasibility of scale-up design for agarose gel activation reactor was preliminarily discussed. The results would be useful to the optimization and scale-up of relevant reactor design.