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Accurate expansion data for CO 2 in petroleum model compounds (e.g., alkanes, cycloalkanes and aromatics) are fundamental information for CO 2 sequestration and enhanced oil recovery in oil reservoir. In this study, the volume expansion of the CO 2  + octane mixture was measured using a fused silica capillary cell with in situ Raman spectroscopy. A section of water was loaded between octane and CO 2 in the fused capillary tube to seal the octane whilst allowing the diffusion of CO 2 into the octane. Raman spectroscopy was applied during our experiments to verify that the CO 2  + octane mixture reached phase equilibrium. Moreover, a good quadratic relationship was observed between the Raman peak intensity ratio and volume expansion factor. It was verified that this method can be used not only just to obtain more accurate experimental data, but also to protract additional volume expansion factor curves or curved surfaces from measured Raman peak intensity ratio using this equation. Over an extended temperature and pressure range, this method was thus shown to be more efficient and accurate than the traditional pressure–volume–temperature methods. [ABSTRACT FROM AUTHOR]

A fused silica capillary reactor combined with a heating/cooling stage, a microscope and a digital camera were used to investigate phase behavior during the hydrothermal liquefaction of microalgae (Dunaliella tertiolecta) and model compounds, including soya protein and glycine, starch, glucose and xylose, stearic acid and palmitic acid. Bubbles were generated at 246°C and disappeared at 360°C upon heating whenDunaliella tertiolectaused as feedstocks. Moreover, liquid products were generated at 300°C upon heating and oily liquid products began to separate out at 250°C upon cooling. The phase behavior of soya protein was similar to that of theDunaliella tertiolecta. Meanwhile, there only observed the bubbles generation during hydrothermal liquefaction of glycine. Heating the starch, glucose and xylose above 350°C generated black solids from carbonization. Stearic acid and palmitic acid only had the process of melting, dissolution, dispersion and precipitation. [ABSTRACT FROM AUTHOR]

Hot compressed water (HCW), with its unique properties, is regarded as a promising solvent for industrial applications. A number of methods to measure the solubility of hydrophobic organic compounds (HOCs) in HCW have been reported. However, these methods were conducted in large-scale stainless-steel reactors, and few included an in situ study regarding the dissolution mechanism of HOCs in HCW during the solubility determination process. In this study, a fused silica capillary reactor in combination with Raman spectroscopy was applied to investigate phase changes, determine the solubility, and study the dissolution mechanism of 1,2-dichlorobenzene in HCW. The total dissolution process of 1,2-dichlorobenzene in HCW was observed under a microscope, and the images were recorded continuously using a digital camera. Raman spectroscopy was used to confirm the homogeneity of the 1,2-dichlorobenzene solution during dissolution. The solubility of 1,2-dichlorobenzene increased from 35.9 to 85.7 mg g−1 in water with increasing temperature from 256.7 to 294.1 °C. Furthermore, the dissolution mechanism of 1,2-dichlorobenzene in HCW is proposed based on the Raman spectra of 1,2-dichlorobenzene and water during the dissolution process in the fused silica capillary reactor. The breakage of the fully hydrogen-bonded (tetrahedral) configuration and the consequent change in the static dielectric constant of water are deemed to be compelling reasons for the high solubility of 1,2-dichlorobenzene in HCW. Our experimental method exhibits great potential for determining the solubility of HOCs in HCW and for investigating their dissolution behavior and dissolution mechanism at elevated pressure and temperature conditions. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Depolymerization is a potentially viable means of recycling waste polymers, converting them back into monomers or other useful compounds. Terephthalic acid (TPA) and 1,4-butanediol (1,4-BD) are the depolymerization monomer products of polybutylene terephthalate. Their yields from depolymerization in hot compressed water (HCW) were previously found to be lower than reported theoretical values. Thus, the phase behavior, stability, and mechanism of monomers in HCW were investigated in a fused silica capillary reactor (FSCR) and a stainless steel autoclave reactor. Phase change observations showed that TPA was completely dissolved in water at 300°C, was relatively stable at 320 to 350°C, and that its recovery significantly decreased at temperatures above 350°C. The decomposition of TPA increased with increasing heating time. However, the recovery of 1,4-BD decreased rapidly with increasing temperature or heating time. A mechanism for the stability of TPA and 1,4-BD is proposed based on their depolymerization products. The products were quantified by Fourier transform-infrared spectroscopy, high-performance liquid chromatography, and gas chromatography coupled with mass spectrometry. The wall effect of the stainless steel autoclave promoted the decomposition of TPA and 1,4-BD in HCW. POLYM. ENG. SCI., 57:544-549, 2017. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Depolymerization of poly(butylene terephthalate) (PBT) in sub- and supercritical ethanol was performed both in a fused silica capillary reactor (FSCR) or a batch autoclave reactor. The phase behavior of PBT in ethanol during heating and cooling was studied in the FSCR under a microscope and captured by a digital camera. The results showed that PBT could dissolve in supercritical ethanol at 330 °C and form a homogeneous solution. Under autogenous pressure in the batch autoclave reactor, the effects of the ethanol/PBT mass ratio (8 g/2 g to 24 g/2 g), reaction temperature (200–280 °C) and reaction time (5–60 min) on depolymerization of PBT in sub- and supercritical ethanol were investigated. The main liquid products of depolymerization were identified and quantified as diethyl terephthalate (DET) and 1,4-butanediol (1,4-BD) by liquid chromatography mass spectrometry, gas chromatography mass spectrometry, and gas chromatography, respectively. PBT could be completely depolymerized at 240 °C in 60 min with an optimal ethanol/PBT mass ratio of 20 g/2 g (10:1). The highest yields of DET and 1,4-BD were 97.7% and 89.4%, respectively. Reaction kinetics analysis showed that the PBT depolymerization in sub-critical ethanol reaction was first order and activation energy was 38.8 kJ mol−1. A reaction pathway was proposed based on the experimental results. [ABSTRACT FROM AUTHOR]

• CSWO of M−NA and nitrogen conversion by CuCo 2 O 4 catalyst was investigated. • Degradation pathways and nitrogen migration mechanism of M−NA were proposed. • Elevate temperature can promote NO 3 – to NO 2 –, resulting in NH 4 + with NO 2 – to form N 2. • CuCo 2 O 4 catalyzing the reaction of ·NO 2 with ·NH 4 , hastening N 2 generation. • CuCo 2 O 4 may induce a reaction between the nitro and amino groups on M−NA to form N 2. Catalytic subcritical water oxidation (CSWO) of M−nitroaniline (M−NA) was investigated in a fused quartz tube reactor (FQTR) to determine the effects of reaction parameters on M−NA mineralization rate, total nitrogen (TN) removal rate and nitrogen-containing products distribution. The results indicated that the TN removal rate was only 26.36 % at 200 °C, 200 % excess oxidant and 15 min residence time, while the TN removal rate reached 67.83 % at 360 °C in SWO of M−NA. Compared with SWO of M−NA, the mineralization rate and TN removal rate of CSWO of M−NA increased by about 10 % and 17.83 %, respectively. The main reason is mainly attributed to CuCo 2 O 4 catalyzing the preferential reaction of ·NO 2 with ·NH 4 , hastening N 2 generation. Alternatively, the CuCo 2 O 4 catalyst may induce a direct reaction between the nitro and amino groups on M−NA within the benzene ring to form N 2. Moreover, degradation pathways and nitrogen migration mechanism of M−NA under SWO/CSWO conditions were proposed. These crucial findings are expected to guide the development of environmentally sustainable catalytic technologies towards addressing significant water pollution challenges. [ABSTRACT FROM AUTHOR]

Abstract: Poly(trimethylene terephthalate) (PTT) was depolymerized in hot compressed water (HCW) using a fused-silica capillary reactor (FSCR) and a batch-type autoclave reactor. The phase behavior of PTT in water during the heating, reaction, and cooling processes was observed in an FSCR with a microscope and recorded by a digital camera. It was found that PTT can dissolve in water in a temperature range of 240–320 °C and form a homogeneous aqueous solution. The effects of the reaction temperature (240–320 °C) and reaction time (5–60 min) were evaluated in a batch-type autoclave reactor. The main depolymerization products of PTT were terephthalic acid (TPA) and 1,3-propanediol (1,3-PDO), which were identified by liquid chromatography mass spectrometry, Fourier-transform infrared spectroscopy, gas chromatography mass spectrometry, Raman spectroscopy, and quantified by high-performance liquid chromatography as well as gas chromatography. Additionally, it was found that 1,3-PDO was converted to 1,5-dioxocane partly in the presence of TPA. Under optimal reaction conditions, i.e. 300 °C, 15 min, with a water/PTT ratio of 8:1 (w/w), complete depolymerization was achieved, and the yields of TPA and 1,3-PDO reached 90.5% and 69.03%, respectively. Based on the results, a reaction mechanism for PTT depolymerization in HCW was proposed. [Copyright &y& Elsevier]

To ascertain the reaction variables on o -chloroaniline (o -ClA) mineralization, total nitrogen (TN) removal rate, and N-species distribution, o -ClA was subjected to catalytic supercritical water oxidation (CSCWO) in a fused quartz tube reactor (FQTR). The findings demonstrated that when the temperature, reaction time, and excess oxidant were 400 °C, 90 min, and 150%, respectively, the mineralization rate of o -ClA could reach more than 95%. Moreover, potential degradation pathways of o -ClA in supercritical water oxidation (SCWO) was proposed according to the GC-MS results. TN removal rate is significantly impacted by Ru/rGO, despite the fact that its catalytic effect on the mineralization of o -ClA was not particularly noteworthy. Compared with no catalyst, the TN removal rate of o -ClA obviously increased from 44.1% to 90.3% at 400 °C, 10 wt% Ru loading, 90 min and 200% excess oxidant. In addition, N-species distribution in SCWO and CSCWO were also investigated. Results indicated that the Ru/rGO catalyst could accelerate the oxidation of ammonia-N and convert it to nitrate-N, promoting N 2 generation. Finally, the possible N transformation pathway in CSCWO of o -ClA was proposed. As a result, this work offers fundamental information about o -ClA catalytic oxidation removal in the SCWO process. [Display omitted] • CSCWO of o -ClA was investigated in a FQTR coupled with Raman spectroscopy system. • The potential degradation pathways of o -ClA in SCWO was proposed. • Ru/rGO has a significant effect on the removal rate of TN. • Ru/rGO accelerate the oxidation of ammonia-N to nitrate-N, promoting N 2 generation. • Possible nitrogen transformation pathway in CSCWO of o -ClA was proposed. [ABSTRACT FROM AUTHOR]

This work developed a new method for measuring the volume expansion of a CO 2 + n -dodecane mixture, using a fused silica capillary cell (FSCC), combined with a heating-cooling stage and a confocal Raman spectrometer. The cell was constructed on the micron scale to reduce the temperature gradient and reagent consumption. The results confirmed the feasibility of this method that using Raman spectra to verify phase equilibrium, a digital camera to record images of the CO 2 + n -dodecane mixture and a micrometer to measure the volume, a section of water (water seal) between n -dodecane and gas phase to prevent n -dodecane from evaporating. It was shown that the volume expansion factor of the mixture increased with pressure going from 1.0 to 10.0 MPa, but decreased as the temperature was raised from 30 to 80 °C. In addition, a positive quadratic relationship ( R 2 > 0.99) was obtained between Raman peak intensity ratio and volume expansion factor, such that more volume expansion factors could be obtained according to the equations with measured Raman peak intensity ratio data. This experiment widens the ranges of temperature and pressure in the measurements of the volume expansion, and provides more volume expansion data for CO 2 -enhanced oil recovery. [ABSTRACT FROM AUTHOR]

The solubility of 4-chlorotoluene in subcritical water was measured using an optically transparent fused silica capillary reactor (FSCR). The total dissolution temperature of 4-chlorotoluene in subcritical water was visually determined. The dissolution uniformity of 4-chlorotoluene in subcritical water was confirmed by Raman spectroscopy. The solubility of 4-chlorotoluene linearly increased with increasing temperature in the range 262.3–293.8 °C. The dissolution mechanism of 4-chlorotoluene in subcritical water is proposed based on the Raman spectra of 4-chlorotoluene and water during the dissolution process in the FSCR. [ABSTRACT FROM AUTHOR]

Abstract: Decomposition of 1,1,1-trichloroethane (TCA) in hot compressed water, with or without an oxidizer, was studied using an optically transparent anti-corrosive fused silica capillary reactor (FSCR), and Raman spectroscopy. The phase behavior of TCA in water during hydrolysis/oxidation was observed continuously under a microscope and recorded with a digital-camera/recording system, A new phase behavior of TCA was found in the presence of excess H2O2; TCA was first gasified during heating, followed by liquefaction under increasing internal pressure as a result of the formation of O2 from the decomposition of H2O2, and subsequently gasified again during further heating up to 400°C. The gaseous products of TCA oxidation in hot compressed water were monitored quantitatively and qualitatively using Raman spectroscopy. The effects of the operating parameters, namely the stoichiometric amount of oxidizer, temperature, and reaction time, were investigated. In our experiments, it was found that 100% CO2 yield was achieved with a 175% stoichiometric amount of H2O2 at 420°C after 360s. Temperature plays a key role in the decomposition of TCA and the formation of CO2 in the supercritical water oxidation (SCWO) process. Based on our results, a reaction mechanism for TCA decomposition in hot compressed water was proposed. The global reaction kinetics showed that the formation of CO2 in the SCWO of TCA was a first-order reaction. [Copyright &y& Elsevier]

• Catalytic oxidation of o -ClA and nitrogen transformation in HCW were investigated. • A flexible micro-reactor platform consist of FQTR and Raman spectroscopy was developed. • Mn 2 O 3 improved the degradtion of ammonia-N and inhibited the production of nitrate-N. • o -Chlorophenol was the main intermediate product of o -ClA in HCWO process. • The potential degradation pathway of o -ClA was proposed. Catalytic oxidation of o -chloroaniline (o- ClA) in hot compressed water (HCW) was investigated in a fused quartz tube reactor (FQTR) to determine the effects of catalyst, temperature, oxygen stoichiometric ratio (OSR) and reaction time on o- ClA mineralization, total nitrogen (TN) removal rate and nitrogen-containing products distribution. The results showed that o -ClA can be effectively degraded in HCW. With the increased of OSR, retention time and temperature or added of Mn 2 O 3 as catalyst, the mineralization rate of o -ClA and the removal rate of TN increased. Ammonia-N was the main nitrogen-containing intermediate product of o -ClA degradation, however, when the oxidant was excessive, ammonia-N was oxidized to form nitrate-N. Althought the catalytic effect of Mn 2 O 3 on the mineralization of o -ClA was not outstanding, it promoted the removal of ammonia-N from the benzene ring, improved the degradtion of ammonia-N, and inhibited the production of nitrate-N. GC–MS analyzed results indicated that o -chlorophenol was the main degradation intermediate product of o -ClA in HCWO process. Meanwhile, the potential degradation pathway of o -ClA was proposed. This work thus provides basic knowledge about o -ClA catalytic oxidation removal in HCW process. [ABSTRACT FROM AUTHOR]

Degradation of phenol by sodium persulfate (SPS) in hot compressed water (HCW) was investigated in a lab-built fused quartz tube reactor (FQTR) coupled with Raman spectroscopy system. The species of S 2 O 8 2−, SO 4 2−, HSO 4 −, SO 3 2− and HSO 3 − in the reaction system were qualitatively and quantitatively analyzed by Raman spectroscopy. The hydrothermal stability of phenol and SPS at different temperature and the degradation of phenol by SPS were also studied. The results indicated that phenol was not stable in aqueous solution above 200 °C, and that only SO 4 2− was generated in the hydrolysis of SPS at temperatures below 50 °C, and SO 4 2− and HSO 4 − were generated at higher temperatures. The maximum conversion rate (90.93%) and mineralization efficiency (38.88%) of phenol by SPS was obtained at reaction temperature of 300 °C with 180 min reaction time. During the degradation of phenol by SPS, HSO 4 − was the main product and S∗ (not detected by Raman spectroscopy) exhibits a positive correlation with temperature. In addition, a degradation pathway of phenol by SPS was proposed. The degradation data for the kinetic analysis indicated that the reaction followed pseudo first-order kinetics, and the reaction rate constants (k s) were given as k 50 °C = 0.0083 min−1, k 100 °C = 0.0197 min−1, k 200 °C = 0.0498 min−1, k 300 °C = 0.0619 min−1 and k 400 °C = 0.0505 min−1 at 30 min reaction. Moreover, the activation energy (12.580 kJ mol−1), the enthalpy change (9.064 kJ mol−1) and the entropy change (−222.104 J mol−1) of the reaction were also calculated. • A lab-built fused quartz tube reactor coupled with Raman spectroscopy system was developed. • Degradation of phenol by sodium persulfate in hot compressed water was investigated. • Hydrothermal stability and products distribution of phenol and SPS were discussed. • The fate of S during the degradation process was qualitative and quantitative analyzed by Raman. • A degradation pathway of phenol by SPS was proposed. [ABSTRACT FROM AUTHOR]