Cu(II) complex ink consisting of copper formate (Cuf) and a primary alkylamine could yield highly conductive copper films at low heating temperatures without a reducing atmosphere. A synergetic effect of the blended alkylamines on the formation of conductive films was observed. It was found that blending two types of amines with different alkyl chain lengths as ligands could improve the conductivity of copper films, compared with using one of these amines alone. The decomposition mechanism of the Cuf–amine complex and the role of amines with different alkyl chain lengths were investigated. It was found that the decrease in the decomposition temperature and the formation of copper films were attributed to the activating effect and capping effect of the amine, and these two effects were dependent on the alkyl chain length. The relative intensity of the dual effects determined the decomposition rate of the complex and the nucleation and growth of particles. The use of blended amines with different alkyl chain lengths as ligands could balance the two effects and lead to appropriate nucleation and growth rates, so that densely packed copper films with low resistivity could be obtained at low heating temperature in a short time. The Cuf–butylamine–octylamine (Cuf–butyl–octyl) ink with 1:1 molar ratio of the amines showed the best performance. The understanding of the synergetic effect could provide guidance to the design of copper complex inks to control the morphology of the films.

The confinement effect of the solid–liquid phase in porous materials was explained only qualitatively in previous research because the pore structure is complicated and difficult to describe quantitatively. In this work, fractal theory was adopted to characterize quantitatively the pore shape by surface fractal dimension. A quantitative model that disclosed the relationship among the solid–liquid phase-change enthalpy, pore size, pore shape, and interfacial groups was proposed for phase-change materials confined in a porous matrix. Furthermore, the model was applied to hydrated salts/silica composite and hydrated salts/expanded graphite composite; the results show that the fitted values agree well with the experimental values.

The chemical equilibrium for the preparation of glycerol monostearate (GMS) from glycerol carbonate (GC) and stearic acid (SA) was investigated. The chemical equilibrium constant K of the base-catalyzed synthesis of GMS from GC and SA was much smaller than that of the acid-catalyzed synthesis of (2-oxo-1,3-dioxolan-4-yl) methyl stearate (ODOMS) from GC and SA. In other words, it was thermodynamically difficult to obtain GMS with a high yield from GC and SA catalysed by basic catalysts. To prove this argument, we used magnesium oxide (MgO) as a catalyst to synthesize GMS from GC and SA. As expected, the yield of GMS was quite low. To increase the yield of GMS, a two-step procedure was proposed. First, pure ODOMS was synthesized by the esterification of GC with SA using copper p-toluenesulfonate (CPTS) as the catalyst. The conversion of SA reached 96.14% under the following conditions: reaction temperature, 140 °C; catalyst amount, 3% CPTS (based on the SA weight); reaction time, 3 h; GC-to-SA molar ratio, 1.5:1. Second, GMS was produced at a yield of 64.4% by the hydrolysis of ODOMS in the presence of triethylamine. The syntheses of ODOMS and GMS were confirmed by 1H- and 13C-NMR, FTIR and LC-MS analysis.

•The equilibrium densities of [Emim][BF4] were used to determine interfacial tension.•The interfacial tension was mainly dependent on the CO2 solubility in [Emim][BF4].•A linear equation was proposed to correlate the interfacial tension and solubility.•The contact angles of [Emim][BF4] phase on solids in CO2 atmosphere were analyzed.In this study, the interfacial tension and wetting properties of [Emim][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate) in CO2 were measured at pressures from 0.1 to 15.0 MPa and temperatures between 308.15 and 343.15 K. Economical modifications of the commercial interfacial apparatus were implemented to pre-saturate the [Emim][BF4] phase by CO2 for the measurement of interfacial tension and production of small sessile droplets for contact angle measurements. The interfacial tension was found to be mainly dependent on CO2 solubility in the [Emim][BF4] phase, and a linear fitting equation was proposed. The contact angles of the [Emim][BF4] phase on quartz, 316L stainless steel, and polytetrafluoroethylene (PTFE) in CO2 atmosphere were analyzed to predict the interfacial tension differences between CO2/solid and IL/solid phases. The reduction of interfacial tension difference was caused by increased CO2 solubility in the [Emim][BF4] phase at low pressure for quartz and 316L stainless steel dense solids. The polymer PTFE material behaved very differently, being susceptible to swelling in compressed CO2.

As an important green synthesis technology of caprolactam, the Beckmann rearrangement reaction of cyclohexanone oxime using high temperature and pressure water as the reaction media was carefully studied with a microreactor. An important byproduct – acetamide was confirmed with a selectivity higher than 40% in the subcritical water, which was more serious than the reported cyclohexanone. The effects of phase state and operating conditions, such as reaction temperature, pressure, flow rate ratio and reactant residence time, on the cyclohexanone oxime conversion and caprolactam selectivity were carefully analyzed, and the results showed that keeping the reaction close to the supercritical state was critical for the preparation of caprolactam.

The phase behavior of the 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) and carbon dioxide (CO2) system from atmospheric to supercritical state was investigated at 0.1–15.0 MPa and 308.15–343.15 K. The solubility data of CO2 in [emim][BF4] and the volumetric expansion ratios of CO2-saturated [emim][BF4] were provided. Experimental results indicated that although CO2 dissolved significantly in [emim][BF4] (from 0 to 62 mol%), the ionic liquid phase only had an expansion ratio less than 17 vol%. The density difference between CO2-saturated [emim][BF4] and pure [emim][BF4] was obvious at high pressure and low temperature, with a maximum of 16.11% at 308.15 K and 15.0 MPa. Based on the experimental results, a fitting equation applicable to precise data interpolation was proposed for the CO2-saturated [emim][BF4] density in this study.

•The NaNO3/SiO2 composite was prepared as shape-stabilized PCM by sol–gel process.•The composite had good thermal energy storage and release ability.•The latent heat was increased with the increase of the roasting temperature.A sodium nitrate (NaNO3)/silica (SiO2) composite was prepared as a shape-stabilized phase change material by a sol–gel procedure. In this composite, NaNO3 acted as the phase change material and SiO2 was used as the supporting material. The maximal weight percentage of NaNO3 in the composite was determined to be 60 wt.%. The chemical composition, morphology, structure and thermal properties were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC) and Laser thermal conductivity meter. The DSC results indicated that the enthalpies of melting and freezing of the NaNO3/SiO2 (60 wt.% NaNO3) composite were 108 kJ/kg and 110 kJ/kg, and the corresponding temperatures of the phase transition were 302 °C and 300 °C, respectively. In the temperature range of lower than 500 °C the phase change enthalpy of the composite was increased with the increase of the roasting temperature.

•A mixture of hydrated salts were adopted as phase change materials.•Phase segregation of the hydrated salts was inhibited.•Subcooling was slightly mitigated.•Thermal cycling performance was greatly improved after PVP coating.A novel shape-stabilized phase change material composite was prepared by impregnating the mixture of hydrated salts (Na2SO4·10H2O–Na2HPO4·12H2O) into porous silica matrix obtained by sol–gel process and further coated with polyvinylpyrrolidone (PVP) to improve the thermal cycling performance. The chemical compatibility, morphology and phase change properties were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), hot-stage polarizing optical microscope (HS-POM) and differential scanning calorimetry (DSC). Confined in the silica matrix, phase segregation of the hydrated salts was inhibited and subcooling was slightly mitigated. No leakage was observed during the solid–liquid phase transition even when the mass ratio of hydrated salts to silica was as high as 70:30. Results showed that the melting enthalpy of the composite can reach 106.2 kJ/kg with the melting temperature at 30.13 °C and there was no significant enthalpy loss after 30 thermal cycles.

Polyethylene glycol (PEG2000)/silica (SiO2) composites with various weight percentages of PEG were prepared as solid–liquid shape-stabilized phase change materials using sol–gel method. In the composite, PEG and SiO2 were chosen as the phase change substance and the supporting material, respectively. The composites were characterized by differential scanning calorimetry and scanning electron microscope. The pore structure of the SiO2 matrix with removal of PEG was studied using N2 adsorption analysis. The phase change enthalpy of PEG in the composite was determined. It was lower than the theoretical value, and decreased with the increase of PEG content. PEG in the composite was strongly confined during the phase transition, and the confinement effect was related with the pore structure of the silica matrix. By correlating the phase change enthalpy with the average pore diameter of the SiO2 matrix by employing a confined phase change model with a constraint layer, the effect of the pore structure on phase transition of PEG was quantitatively evaluated. The phase change enthalpy of PEG in the composite depended on the average pore diameter of the SiO2 matrix, the pore geometrical shape, and the thickness of the PEG constraint layer.

The deactivation of alkali solid catalysts for the synthesis of glycerol carbonate from glycerol and dimethyl carbonate was investigated. Calcium oxide, calcium hydroxide and calcium methoxide were chosen as the representatives of the alkali solid catalysts. When the catalysts were recycled, the yield of glycerol carbonate decreased dramatically. The alkali solid catalyst was converted to the basic calcium carbonate Cax(OH)y(CO3)z, which was the cause of the decrease of glycerol carbonate yield. It was found that the chemical interactions of the alkali solid catalyst with glycerol and glycerol carbonate led to the formation of the basic calcium carbonate Cax(OH)y(CO3)z, for which the mechanism was proposed. Based on the deactivation mechanism, calcium diglyceroxide was adopted as a new catalyst for the transesterification of glycerol and dimethyl carbonate. Compared to calcium oxide, calcium hydroxide and calcium methoxide, calcium diglyceroxide showed excellent reusability for the transesterification of glycerol and dimethyl carbonate. For calcium oxide, calcium methoxide and calcium diglyceroxide, there were dissolution losses of the catalysts in the reaction medium. For calcium hydroxide, the catalyst dissolution loss in the reaction medium was nearly negligible. For calcium diglyceroxide, the dissolution of the catalyst in the reaction medium did not influence the yield of glycerol carbonate significantly.

Continuous synthesis of d,l-α-tocopherol catalyzed by a sulfonic acid-functionalized ionic liquid was conducted in supercritical carbon dioxide (SC-CO2). The product was continuously separated from the reaction mixture by SC-CO2 extraction during the course of reaction. Decompression of the supercritical fluid mixture downstream gave the product free of ionic liquid. The yield of d,l-α-tocopherol was improved with non-polar SC-CO2 and polar propylene carbonate as solvents. The selectivity of d,l-α-tocopherol to trimethylhydroquinone (TMHQ) between CO2-rich and ionic liquid-rich phase increased with the increase of pressure, and decreased with the increase of temperature at temperatures from 70 to 115 °C and pressures from 15 to 25 MPa. Effect of temperature, pressure and flow rate on the continuous synthesis of d,l-α-tocopherol was studied. The conversion of isophytol (IP) and the yield of d,l-α-tocopherol increased with decreasing pressure. The extraction rate of d,l-α-tocopherol increased with increasing pressure and decreased with increasing temperature. d,l-α-Tocopherol yield of 90.4% was obtained at 100 °C, 20 MPa and a CO2 residence time of 12.6 min.Continuous synthesis of d,l-α-tocopherol catalyzed by a sulfonic acid-functionalized ionic liquid was conducted in supercritical carbon dioxide (SC-CO2). The product was continuously separated from the reaction mixture by SC-CO2 extraction during the progress of reaction. d,l-α-tocopherol yield of 90.4% was obtained at 100 °C, 20 MPa and CO2 flow rate of 178 mmol min−1.

The silica aerogel was prepared by a sol–gel process followed the drying process at atmospheric pressure and 40 °C. The silicon source was the rice hull ash, which is an agricultural waste and rich in silicon. The rice hull ash was extracted with sodium hydroxide solution to get a sodium silicate solution. The solution was neutralized with sulfuric acid solution to form silica hydrosol, which was immediately added appropriate quantity of tetraethyl orthosilicate (TEOS), and then gelated to be a gel. The aged gel was washed successively by water and ethanol, and finally dried at the atmosphere. The prepared material was characterized using transmission electron microscope (TEM) and Brunauer–Emmett–Teller (BET) measurements. The specific surface area of the prepared material is high as 500 m2/g with a bulk density of 0.33 g/cm3. The diameters of the pores inside the prepared materials are between 5 and 60 nm.

A linear solvation energy relationship (LSER) method was used to develop a predictive model for the diffusivities of organic solutes in supercritical CO2 at infinite dilution. The LSER model was based on the diffusivities of 18 solutes and 104 data points for sc-CO2 in the range of 32–60 °C and 8–100 MPa. The independent variables in the model were empirically determined descriptors of the solute molecules and the dipolarity/polarizability of CO2 at a given density. The model was tested for prediction accuracy by using the diffusivities of 10 solutes not included in the database. The model provided relative deviations less than 10% in the correlation and prediction of the diffusivities in supercritical CO2 of the organic solutes considered. The accuracy of the proposed LSER model is comparable with He–Yu [31] equation, which is the most effective correlation in the literatures. The coefficients of the model show that diffusivity in supercritical CO2 is strongly dependent on the dipolarity/polarizability of CO2. The hydrogen-bond basicity and dipolarity/polarizability of the solute have significant effects on the diffusivity, whereas the hydrogen-bond acidity and excess molar refractivity are less important. The logarithm of the solute's gas-to-hexadecane partition coefficient used to model dispersion interactions and cavity formation processes was found to be statistically insignificant.

Silica aerogel, which is a mesoporous light solid material, was prepared from the rice hull ash by sol–gel followed supercritical carbon dioxide drying. The rice hull ash, which is rich in silica, was extracted using sodium hydroxide solution to produce a sodium silicate solution. The solution was neutralized with sulfuric acid solution to form a silica gel. After washing with water and the solvent exchange with ethanol, the aged gel was dried to produce aerogel using supercritical carbon dioxide drying. The prepared silica aerogel was characterized using SEM, TEM and BET measurements. The specific surface area of the rice hull ash aerogel was as high as 597.7 m2/g with a bulk density of 38.0 kg/m3. The diameters of the pores inside the aerogel are between 10 and 60 nm.

Supercritical carbon dioxide was used as the reaction medium for the transesterification of ethylene carbonate (EC) with methanol to produce dimethyl carbonate (DMC) with K2CO3 as the catalyst under pressure up to 30 MPa. The effects of the presence of supercritical CO2 and the pressure on the conversion of EC and the selectivity of DMC were investigated. From the experimental results, it was found that the selectivity of DMC could be enhanced when the reaction was pressurized with supercritical CO2, although the conversion of EC decreased.

A sodium sulfate (Na2SO4)/silica (SiO2) composite was prepared as a shape-stabilized solid-liquid phase change material by a sol-gel procedure using Na2SiO3 as the silica source. Na2SO4 in the composite acts as a latent heat storage substance for solid-liquid phase change, while SiO2 acts as a support material to provide structural strength and prevent leakage of melted Na2SO4. The microstructure and composition of the prepared composite were characterized by the N2 adsorption, transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. The results show that the prepared Na2SO4/SiO2 composite is a nanostructured hybrid of Na2SO4 and SiO2 without new substances produced during the phase change. The macroscopic shape of the Na2SO4/SiO2 composite after the melting and freezing cycles does not change and there is no leakage of Na2SO4. Determined by differential scanning calorimeter (DSC) analysis, the values of phase change latent heat of melting and freezing of the prepared Na2SO4/SiO2 (50%, by mass) composite are 82.3 kJ·kg−1 and 83.7 kJ·kg−1, and temperatures of melting and freezing are 886.0 °C and 880.6 °C, respectively. Furthermore, the Na2SO4/SiO2 composite maintains good thermal energy storage and release ability even after 100 cycles of melting and freezing. The satisfactory thermal storage performance renders this composite a versatile tool for high-temperature thermal energy storage.