•We synchronize gas hydration with membrane permeation to improve mass transfer for gas separation.•An accurate formula was developed to calculate the gas consumption during stable growth of ...hydrate.•We built a dynamic matching model to describe hydrate-membrane synergistic action.•We simulated the separation of H2-containing gas mixture by hydrate-membrane coupling method.•Simulation results indicate that the coupling method greatly improves the gas separation effect.
The recovery of hydrogen (H2) form H2-containing gas mixtures, such as petrochemical refinery tail gas, plays a important role in energy conservation and cost reduction. The hydrate-membrane coupling separation process has been demonstrated as a more efficient and energy-saving approach for H2 recovery. This study aims to achieve the synergistic matching of hydration and permeation, so as to explore the underlying mechanisms of coupling and facilitate subsequent experimental studies. In this work, an effective method was developed to calculate the gas consumption rate during the stable growth stage of hydrates. Furthermore, a dynamic matching model of the hydrate-membrane coupling mechanism was employed to simulate the variations in the separation process using infinitesimal methods. The simulations indicate that the H2 concentration of product gas and the feed gas treatment capacity of the coupling method outperform those of hydrate separation and membrane separation alone. Overall, this study provides valuable insights into an efficient and energy-saving method for H2 recovery from H2-containing gas mixtures, utilizing the hydrate-membrane coupling method. These findings hold promising prospects for practical application in the future.
Here, an approach toward for continuous H2 recovery from hydrogenation plant off-gas based on hydrate formation in the presence of tetra-n-butyl ammonium bromide (TBAB) is proposed. Firstly, we ...explored the conditions to form the CH4/H2/TBAB hydrate through pressure search method in the single-stage equilibrium separation experiments toward CH4/H2 mixture. The influence of initial pressure, temperature, and initial gas–liquid volume ratio were systematically optimized in the context of 10 wt% TBAB solution. Then, we conducted the continuous separation experiments of CH4/H2 binary mixture and hydrogenation plant off-gas using a set of laboratory-scale continuous stirred reactor according to the optimized conditions, in which the effects of pressure and liquid flow rate upon continuous separation were further studied. The experimental results that the H2 concentration in the unhydrated gas (the recovered gas) is up to 89 mol% and the yield of H2 recovery is more than 58.68% indicate the efficiency to recover H2 using continuous hydrate separation, which lays the foundation for further industrial application.
•We explored the condition to form CH4/H2/TBAB hydrate.•One stage equilibrium hydrate separation of CH4/H2 mixture was conducted.•We achieved continuous H2 recovery from plant off-gas via hydrate formation.•We investigated the influences of pressure, temperature and gas-liquid volume ratio.•The gas storage capacity of hydrate was investigated.
The effects of mung starch on methane hydrate formation equilibria/rate and gas storage capacity were investigated in this work. Mung starch at three concentrations of 100, 500, and 800 ppm were ...tested comparing with the pure water. The results show that mung starch has slight thermodynamic promotion effect on methane hydrate formation, because it decreases the gas-liquid-hydrate three-phase equilibria pressure at the same temperature. The formation rate and gas storage capacity of methane hydrate in the presence of mung starch were studied at 8.0 MPa and 275.15 K–281.15 K. The results demonstrate that mung starch significantly accelerates methane hydrate formation rate. It could shorten the induction time and reaction time of methane hydration process. In addition, the gas storage capacity of methane hydrate is also increased greatly. The solubility data of methane indicate that mung starch indeed plays a role of solubility enhancement. The green and environmental friendly characteristics of mung starch could be helpful to promote the application of hydrate-based technology.
•The formation conditions of CH4 hydrate were measured in mung starch solution.•We measured the formation rate/gas storage capacity of CH4 hydrate with mung starch.•We obtained the solubility of CH4 in mung starch solution without hydrate formation.•A green and effective hydrate kinetic promoter is developed in this work.
The carbon dioxide (CO2) capture and utilization has attracted a great attention in organic synthesis. Herein, an unpresented transient stabilization effect (TSE) of CO2 is disclosed and well applied ...to the electrochemical hydrogenation of azo compounds to hydrazine derivatives. Mechanistic experiments and computational studies imply that CO2 can capture azo radical anion intermediates to protect the hydrogenation from potential degradation reactions, and is finally released through decarboxylation. The promotion effect of CO2 was further demonstrated to work in the preliminary study of electrochemical reductive coupling of α‐ketoesters to vicinal diol derivatives. For the electrochemical reductive reactions mentioned above, CO2 is indispensable. The presented results shed light on a different usage of CO2 and could inspire novel experimental design by using CO2 as a transient protecting group.
A new transient stabilization effect (TSE) of CO2 is identified and applied to the electrochemical hydrogenation of azo compounds and the reductive coupling of α‐ketoesters. The TSE influence of CO2 means that overactive intermediates can be captured by CO2 to prevent their decomposition or side reaction to complete the synthesis that is difficult to achieve by direct means. The CO2 can be released later through a decarboxylation process.
•L-proline and betaine are outstanding environmental-friendly THIs.•Betaine is more potent than L-proline and ethylene glycol at the same mole fraction.•Betaine forms stronger H-bonds with water than ...L-proline and ethylene glycol.•Stronger H-bonds between THIs with water led to more potent hydrate inhibition.
L-proline (PRO) and betaine are osmoprotectants that protect various plant species in extreme environments such as drought, salinity, extreme temperatures, ultraviolet radiation, and heavy metals. In this work, the phase equilibrium conditions of methane hydrates were examined in the presence of PRO and betaine. The results showed that both PRO and betaine were outstanding effective thermodynamic inhibitors for methane hydrate. And betaine showed stronger inhibition than PRO at the same concentration. Additionally, the Gaussian 09 program was used to predict the hydrogen bond energies between PRO, betaine, and ethylene glycol with water molecules. The results demonstrated that betaine showed stronger interactions with water than PRO, which was in agreement with the experimental data of methane hydrate phase equilibrium.
•CH4/N2 hydrate formation conditions were measured with tea polyphenol and catechin.•The formation rate and gas storage capacity of CH4/N2 bioclathrates were obtained.•The enhanced separation of ...CH4/N2 via bioclathrate formation was conducted.•Biopromoter can promote the development and application of hydrate separation method.
The separation and utilization of coal bed methane have great research and economic significances. Consequently, we investigated the two-stage separation of CH4/N2 binary gas mixture, an analogue of coal bed methane, using hydrate separating method in this work. In order to realize green environmental protection and promote the popularization of hydrate separation method, two biological additives, i.e., tea polyphenol and catechin, were applied to recovery CH4 by forming bioclathrates. The influences of tea polyphenol and catechin on hydrates thermodynamic phase equilibria, kinetic hydration rate, gas storage capacity and separation effects were systematically studied. The results show that these two bio-additives could significantly increase the formation rate and gas storage capacity of hydrates in comparison with pure water system. In addition, the recovery of CH4 and separation factor are also enhanced in the presence of bio-promoters. Therefore, the formation of bioclathrates is helpful to protect environment, and promote the industrial application of the hydrate separation technology.
•OGP was first time used in hydrate formation and significantly increased RWH and rR.•The performance of OGP on increasing RWH was better than those of other surfactants.•OGP had little negative ...thermodynamic effect on hydrate formation.•The increase in RWH affected the effects of wp,0 and pressure on hydrate formation.•The model in this work can accurately predict the Peq of C2H4OGP solution systems.
A new promoter for hydrate-based technologies (HBTs) called n-octyl-β-D-glucopyranoside (OGP) was proposed in this work. The effect of OGP on the properties of liquid phase, the thermodynamic effect of OGP on structure I hydrate (formed by ethylene and water) and the effect of OGP on the formation process of structure I hydrate were investigated. To determine the controlling factors of the hydrate formations, a new model which can accurately predict the thermodynamic equilibrium hydrate formation pressures of corresponding systems was proposed, and the average relative deviation of the model is 1.6%. The experimental results show that, OGP was a low foaming promoter with high surface activity, and OGP rarely affected the thermodynamic phase equilibria of corresponding systems. OGP not only significantly increased the hydrate formation rate (rR) but also increased the conversion rate of the water into hydrate (RWH) from about 61.2% to about 95.5%, and the maximum RWH of the ethylene gas-OGP solution system in this work was 97.5 ± 1.6%. The optimum initial OGP concentration for HBTs was 0.2 mass%. The difference in rR caused by the difference in pressure significantly decreased as RWH increased from 10% to 40%. rR did not significantly decrease during the period that RWH increased from 40% to 65%, and the steady rR during that period benefits the application of HBTs.
Recovery of H2 and N2 from the tail gases of the ammonia synthesis plant could significantly improve the ammonia output and economic benefits. In this work, we measured the formation conditions of ...tail gas hydrates, conducted separation of tail gases via hydrate formation in tetrahydrofuran (THF) and ammonia solution, and proposed a two-stage separation process. The separation effects of temperature, pressure, and gas–liquid ratio (GLR) were investigated as well. The results show that the two-stage separation can effectively remove CH4 from the tail gases. The total concentration of H2 and N2 in gas products is more than 94 mol %, with a recovery of up to 95%.
