a hybrid absorption–adsorption method to efficiently capture carbon - carbon dioxide absorbent
Removing carbon dioxide is an essential step in many energy sources.
Here we report a new slurry concept that combines the specific advantages of metals
Through suspended zeolitic imidazolate framework-organic framework, ionic liquid, Amine and membrane8 in glycol-2-
1) metriac solution
We show that this approach may provide a more efficient technology for capturing carbon dioxide than conventional technologies.
The carbon dioxide adsorption capacity of our slurry reaches 1.
1 bar the of 25 Moore L-1 and carbon dioxide/hydrogen, carbon dioxide/nitrogen and carbon dioxide/methane of selective respectively 951, 394 and 144.
We have proved through breakthrough experiments that the slurry can effectively remove carbon dioxide from the gas mixture at normal/normal temperature.
Most importantly, the adsorption enthalpy is only-29 k _ j _ m _ 1, which indicates a significant reduction in the energy required for the regeneration of the adsorption agent.
In addition, from a technical point of view, the mud can flow and pump, unlike the solid adsorption agent.
This allows us to use a continuous separation process with a thermal integral.
The materials used in this work include ZIF-
8, mIm, ethylene glycol, ethanol ,-
N-hexane, ethane, methybenzene, carbon monoxide, triethylene glycol, water and gas.
Two of them, ZIF-
Purchased 8 and mIm from Sigma-Aldrich.
Image of scanning electron microscope ()
X-ray diffraction of purchased ZIF-8 sample ()
Consistent with the reports in the literature.
Hexane, chlorhexone, toluene, four-chlorine methane and triethylene glycol were purchased from Beijing chemical reagent company, China.
Analytical grade carbon dioxide (99. 99%), nitrogen (99. 99%), methane (99. 99%)and hydrogen (99. 999%)
It was purchased from Beijing Associated Press North Fen natural gas industry, China.
Synthetic gases CO/N, CO/H and CO/CH were prepared in our own laboratory. A Hewlett-
Packard gas chromatography (HP 7890)
Used to analyze the composition of the prepared gas. All the ab(d)
The adsorption measurement experiment was carried out using an experimental device with exemplary instructions.
A detailed description of the settings can be found in our previous report.
The key components of the device are clear sapphire batteries and steel-
Blind batteries are made and they are all installed in the air bath.
The effective volume of sapphire battery is 60 cm, and the effective volume of blind battery plus connecting tube is 112 cm.
The maximum working pressure of these two batteries is designed as 20mpa mpa.
In order to directly observe the sample in the cell, the lamp with the light source (type LG100H)
Installed on the outside of the battery.
Secondary platinum resistance thermometer (type-pt100)
Used as a temperature sensor.
The system pressure is measured using a calibrated Heise pressure gauge and differential pressure sensor.
The uncertainty of pressure and temperature measurement is ± 0. 01u2009MPa and±0.
1 K respectively. Real-
Record the time reading of the system temperature and pressure.
Before the experiment, remove the sapphire battery from the instrument, wash and dry with distilled water, and then load a known amount of dry porous material.
After that, the known amount of solvent is slowly and evenly immersed in the Sapphire battery.
The dry porous materials and solvents used are weighed by an electric balance with a precision of ± 0. 1u2009mg.
Stir a mixture of porous materials and liquid solvents into a suspended mixture (Mud).
The battery was subsequently reinstalled into the device. The system (
Sapphire battery blind Battery Tube connecting two batteries)
Then clear by vacuum.
Inject a sufficient amount of synthetic gas into the blind pool, and then set the desired temperature value through the air bath.
Once the temperature and pressure of the blind pool remain the same, the gas mixture pressure in the blind pool is recorded as the initial pressure.
The top valve of the Sapphire battery is then slowly opened to allow the required amount of synthetic gas to flow into the sapphire battery from the blind battery.
After that, the valve was closed and the magnetic mixer was opened.
The pressure of the residual gas mixture in the blind pool was recorded.
With the adsorption of the slurry to the gas mixture, the system pressure in the Sapphire battery gradually decreases.
During each measurement, the pressure in the Sapphire battery is recorded as the function time.
When the pressure of the system remains constant for at least 2 km/h, we think the system is balanced.
The balance pressure of the Sapphire battery is recorded.
By pushing the connected hand pump, sample the gas mixture in the Sapphire battery balance gas phase at constant pressure and analyze it by HP 7890 gas chromatography.
By measuring the height of the equilibrium liquid phase, the volume of the slurry in the Sapphire battery can be obtained.
The inner radius of the Sapphire battery is known to be 1. 27u2009cm.
In this work, the amount of each gas absorbed and adsorbed in the measurement sample was determined by mass balance, as described below.
Total number of moles of gas mixture ()
The temperature of the injected Sapphire battery is calculated by the following formula: where is the system temperature, where is the initial pressure of the blind battery, and what is the equilibrium pressure of the blind battery after injecting gas into the sapphire battery? The total volume of the blind unit plus the tube connected to the blind unit is the gas constant.
Can be compressed and calculated using the Benedict-Webb-Rubin-Starling equation of state.
Total gas ()
In the equilibrium gas phase of the Sapphire battery after absorption and adsorption equilibrium, it is determined by the following factors: where is the equilibrium pressure of the Sapphire battery, which is the compression factor corresponding to the gas composition.
It is the volume of the equilibrium gas phase in the Sapphire battery at the end of each experiment.
Total absorption CO ()and that of N (CH or H)()
The calculation in the slurry is as follows: The neutralization is the molar fraction of CO in the synthetic gas and the equilibrium gas phase, respectively;
Is the Moore score of N (CH or H)
In the synthesis gas and equilibrium gas phase.
Therefore, the apparent molar fraction of CO ()and N (CH or H)()
In the equilibrium slurry stage, the following formula can be obtained: in the equilibrium-
Based on the separation process, adsorption selectivity is a good indication of the efficiency of CO separation.
In this study, the apparent selectivity of CO to other components in the mud ()
The calculation is as follows: to provide a reference for showing the superiority of the proposed absorption-adsorption mixing method, the selectivity of CO in solid ZIF-8 ()
Also provided, the calculation is as follows: The mole fraction of CO and N (CH or H)
Adsorption phase (ZIF-8), respectively.
Coefficient of solubility ()
The content of CO in the adsorption agent is an important indicator of the separation capacity, calculated as follows: where is the volume of the adsorption agent (
Liquid or slurry).
Apparent Volume solubility of CO in slurry ()
Defined as: the volume ratio of the initial slurry ()
Volume ratio of gas-solid adsorption agent (′)
Defined as: where is the volume of the solid adsorption agent.
Standard temperature and pressure, respectively.
Adsorption capacity of solid ZIF-
8 suspended in the liquid adsorption of the gas composition, the calculation is as follows: where the total absorption of CO and N (CH or H)in ZIF-
8 suspended in the slurry is their Henry constant in the liquid adsorption agent, which is the corresponding equilibrium pressure.
The quality of the absorbent.
Henry constants of CO, CH, N and H in ethylene glycol at 293 °c.
The experiment determined and reported 15 k.
The above method of mass balance has been used in our previous work.
To verify our measurement method, the pure CO adsorption equation and gas selectivity obtained for CO/N (=0. 2286)
Mixture in solid ZIF-8 at 303.
This method was used to measure 15 k and compare it with the literature data (). Adsorption agent (solid ZIF-8)
By X-ray diffraction (6000)
There is Cu k alpha radiation (0.
1542, nm, 40kv, 400ma)
At a scanning rate of 2 °c per minute.
Form and energy dispersion of X-
X-ray spectral measurements were obtained using a FEI Quanta 200F scanning electron microscope.
The Fourier transform infrared spectrum was obtained using the Bruker 80 v spectrometer.
Fourier transform Raman spectroscopy was obtained using the HORIBA XploRA spectrometer.
Thermal weight measurements were performed on the netzsch sta 409 PC/PG instrument.
The experimental device for dynamic breakthrough measurement is shown.
The gas manifold consists of two parts, Line A and Line B, with A mass flow controller.
From the inert gas "a" line (It's helium)
Inject before the experiment to clear the air in the columns and pipes and regenerate the slurry after each experiment.
From the "B" line, a CO-containing gas mixture with constant flow rate is injected into the breakthrough experiment.
Both lines "A" and "B" use three-way valve.
The stainless steel column is 165 high with a coat attached to the water lot for temperature control.
The inner diameter of the column is 2 cm.
ZIF-wait about 400
Loading 8/ethylene glycol-mIm slurry in the column.
A gas dispenser is fixed at the bottom of the tower.
The maximum working pressure of the device design is 5mpa mpa.
The outlet gas at the top of the column was sampled and analyzed by HP 7890 gas chromatography.