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Graphical abstract Highlights • CO 2 -expanded gelation approach was proposed for preparing bimodal porous materials. • CO 2 -expansion induced much short time for gelation. • CTAB template contributed to the surface area and CO 2 -expansion to the pore volume. • Bimodal silica-PW showed good selectivity and short time for 1,8-cineole from α-terpineol. • Bimodal Ni/SiO 2 exhibited excellent performance for phenol hydrogenation to cyclohexanol. Abstract In this work, a facile route was designed to fabricate bimodal porous silica with high surface area and pore volume via a CO 2 -expanded gelation with assistance of CTAB. Parameters such as the amount of CTAB, pressure of CO 2 and agitation time were investigated and optimized. Results showed bimodal silica contained small pore size (around 2 nm) from CTAB templating and large pore size (> 4 nm) from CO 2 -expanded gelation could be easily adjusted by the synthesis conditions. A typical sample with surface area of 1133 m2/g and pore volume of 1.24 mL/g was applied as a catalyst support for phosphotungstic acid, revealing much faster catalysis rate and relatively high selectivity for 1, 8-cineole from α-terpineol than the commercial MCM-41. The approach was also successfully extended to the preparation of bimodal NiO/silica composite, and the reduced Ni/silica showed higher catalysis performance than the unimodal sample for phenol hydrogenation to cyclohexanol. [ABSTRACT FROM AUTHOR]

A solute-saturated supercritical fluid loading (SSFL) process was proposed to load 2-phenylethyl alcohol (PEA) in silica and activated carbon (AC). The adsorption and loading amounts of PEA in carries were investigated at different temperatures (50.0–60.0 °C) and pressures (8.0–14.0 MPa) by a column sampling method. By using a high-pressure quartz spring method, the adsorption amounts of the binary PEA and CO 2 in silica were determined. The retention of PEA in the SSFL powder flavors was evaluated by a nitrogen-purging method. Results revealed that, compared with AC, silica had high loading of PEA (maximum 0.484 g/g) and showed better results in PEA preservation from loss at room temperature and control release at higher temperature; PEA suppressed the adsorption of CO 2 at relatively high pressure. Discussion indicated that precipitation and adsorption contributed to the high loading of PEA in silica, while adsorption mainly contributed to that in AC. [ABSTRACT FROM AUTHOR]

The solid–liquid–gas equilibrium data of the tetra-n-heptyl ammonium bromide ([thepAm][Br])–CO 2 system, and then the solubility and absorption kinetic data of CO 2 in different phases of [thepAm][Br] were measured by a high pressure quartz spring method. Results showed high molar fractions of CO 2 in solid [thepAm][Br] (0.921 at 15.0 MPa and 313.2 K; 0.567 at 5.0 MPa and 313.2 K) which were even higher than those in liquid [thepAm][Br] at same pressures and those in other ionic liquids (ILs) reported in the literature at relatively high pressures. The study also revealed that CO 2 absorption rate was very pressure dependent. The Peng–Robinson equation of state (PR-EoS) with the van der Waals one-fluid mixing rules and the NRTL model were employed to calculate the phase equilibrium data by looking the solid [thepAm][Br] as a special liquid. A 1-D diffusion model with a concentration dependent diffusion coefficient equation combined with the NRTL model was developed to calculate the absorption kinetic data of CO 2 in [thepAm][Br], suggesting that the diffusion coefficient was not a constant at high pressures. [ABSTRACT FROM AUTHOR]

Highlights: [•] A high-pressure PLM approach was proposed and established. [•] Melt crystallization behaviors of two solutes in CO2 were studied. [•] High pressure CO2 accelerated the crystallization rates of the two solutes. [•] CO2 did not evidently affect the nucleation or growth patterns of the two solutes. [•] The crystallization behaviors of the two solutes were different from those of polymers in CO2. [ABSTRACT FROM AUTHOR]

Abstract: Adsorption of 2-phenylethyl alcohol (PEA) from supercritical CO2 onto silica aerogel was investigated. A monolayer to multilayer adsorption isotherm was observed, measured at 15.0MPa and 323.2K, from the PEA-unsaturated to PEA-saturated supercritical CO2, indicating the potential utility of the solute-saturated supercritical adsorption (SSA). The amount of PEA adsorbed on the silica aerogel with SSA at different temperatures and pressures was measured, and the release of PEA from the aerogel at 303.2K was also evaluated. A theoretical model for the SSA equilibrium was developed with the assistance of the adsorption isotherms of pure CO2 onto the silica and considering a three-phase binary system, where the two-dimensional van der Waals equation of state and the three-dimensional Stryjek–Vera modification of the Peng–Robinson equation of state were used respectively to describe the adsorbed phase and the bulk phases (vapor phase and liquid phase). Results showed that the model was capable of describing the adsorption behavior of the system with an average absolute relative deviation of 3.3%. [Copyright &y& Elsevier]

Abstract: A novel carbonation route for the synthesis of CaCO3 is reported with high pressure CO2 scintillated into dry Ca(OH)2 powder containing a solid ionic liquid (SIL, tetra-n-heptyl-ammonium bromide). Results show that calcite structure with rhombohedral lattice is produced at all CO2 conditions investigated: supercritical (15.0MPa, 50.0°C), compressed (5.0MPa, 30.0°C), liquid (15.0MPa, 25.0°C), gaseous (0.1MPa, 30.0°C) and atmospheric (0.1MPa, 30.0°C). Furthermore, rapid and complete conversion is achieved under the supercritical condition with the production of nano-sized calcite particles, suggesting that coupling SIL with CO2 could be an effective system for enhancing traditional gas–solid reactions. A mechanism for the rapid gas–solid carbonation reaction is proposed with emphasis on the initialization of the reaction by tiny adsorbed water and CO2 dissolved in the SIL. [Copyright &y& Elsevier]

Abstract: A supercritical fluid-based method is proposed to produce coenzyme Q10 (CoQ10) nanoparticles. First, CoQ10/polyethylene glycol 6000 composite particles are prepared by a modified PGSS (particles from gas-saturated solutions) process with controlling the flow rate of the gas-saturated solution. Then, CoQ10 nanoparticles are obtained by dissolving the composite particles into water. The effect of experimental variables of the modified PGSS process, including pressure, temperature, flow rate of the gas-saturated solution, and mass fraction of CoQ10, on the CoQ10 particle size and particle size distribution was investigated. Results show that CoQ10 slurry product with a median diameter of 190nm and yield of 89.8% can be prepared at an optimum condition (operating pressure of 25MPa, operating temperature of 80°C, gas-saturated solution flow rate of 1.02mL/min, CoQ10 mass fraction of 40% and nozzle diameter of 100μm) via the supercritical fluid-based method. [Copyright &y& Elsevier]