BREAKTHROUGH ANALYZER (BTA)

DIRECT AIR CAPTURE DAC is difficult due to low concentrations of carbon dioxide in air along with other impurities including moisture, and the captured CO2 may be sequestered underground, sold, or converted into value added chemicals to offset carbon emissions.	CO2 ADSORPTION Power generation, chemical plants, and refineries are significant point sources for carbon dioxide emissions and the higher concentrations often require different operating conditions when compared to direct air capture
OLEFIN/PARAFFIN SEPARATONS Are a core part of the petrochemical industry and used to in the production of polymers such as polyethylene and polypropylene; these separations are energy intensive and increase CO2 emissions.	NATURAL GAS SEPARATION Natural gas is a mixture of hydrocarbons and other gases that must be purified prior to use in industrial applications and households for heating and food preparation.
TOXIC GAS ADSORPTION Porous solids are used for personal protection and also under development for the capture of toxic gases including sulfur dioxide, hydrogen sulfide, and nitrogen dioxide from natural gas or other process feeds.	WATER ADSORPTION Harvesting water from the air may be a critical technology for many parts of the world clean, where the fresh water supply is limited due to an arid climate or the increasing usage of water for agriculture.

ZEOLITES Pressure swing adsorption using Zeolite 5A, 13X, or LiX, which have high selectivity for adsorbing nitrogen are used commercially for air separation and producing oxygen.	SILICAS Amine functionalized silicas are effective and highly selective adsorbents and used for the direct air capture (DAC) of CO2.
POROUS MEMBRANES/MONOLITHS Porous membranes and monoliths coated zeolites or MOFs are commonly used to improve the operational efficiency of separation processes.	ACTIVATED CARBON Volatile organic component (VOC) from automobile fuel systems are captured by canisters filled activated carbon and these VOC emissions are minimized.
POROUS ALUMINAS Alumina – Supported Ionic Liquids are effective adsorbents with potential applications for the separation of CO2 from natural gas.	METAL-ORGANIC FRAMEWORKS MOFs are highly selective adsorbents which are effective for demanding commercial applications including alkanes & olefins, olefins & alkynes, DAC and CO2 & CH4.

BREAKTHROUGH ADSORPTION THEORY

Breakthrough analysis is a powerful technique for determining the sorption capacity of an adsorbent under flow conditions. Dynamic breakthrough adsorption provides many advantages over static adsorption measurements.

• • Easily collect multicomponent adsorption data
  • Determine adsorbate selectivity
  • Replicate process conditions

When conducting breakthrough analysis, sample preparation is a critical step in the analysis process to prevent pressure drop and mass transfer limitations. Pressure drop occurs when the interstitial space between particles is too small to accommodate the flow rate of gas. Mass transfer limitations occur when the pore size of the material is similar to the kinetic diameter of the adsorbate. Appropriately sizing particles is therefore critical to obtain the best results.

MULTICOMPONENT VAPOR ANALYSIS

The Micromeritics BTA is capable of flowing up to two vapor streams simultaneously through its packed column. The thermostated environmental chamber prevents the condensation of these vapor streams during analysis and ensures that all gases and vapors maintain a constant temperature within the instrument. Vapor streams are generated using a bubbler which allows for a carrier gas to reach saturation with the vapor of choice. The figure below displays multicomponent ethanol/water breakthrough measurements conducted on zeolite 13X.

EXAMINING A BREAKTHROUGH CURVE

• • 1. COMPLETE ADSORPTION

       The adsorbate gas is completely adsorbed such that none can be detected at the outlet of the breakthrough column

    2. BREAKTHROUGH

       The adsorbate gas is first detected at the outlet of the breakthrough column. Gas continues to adsorb; however, the adsorbent is no longer able to adsorb the entirety of the gas that is entering the breakthrough column

    3. SATURATION

       The adsorbent has reached saturation and can no longer adsorb the adsorbate gas, allowing it to pass through the column freely

 

 

CARBON DIOXIDE ADSORPTION

Single component carbon dioxide breakthrough adsorption experiments were conducted on zeolites 13X and 5A, and metal-organic frameworks MIL-53(Al) and Fe-BTC. All materials were analyzed at 30°C while flowing an equimolar gas stream consisting of 10 sccm nitrogen and 10 sccm carbon dioxide. A 1 sccm stream of helium was also blended into the feed gas stream as a tracer gas to aid in identifying the start of the breakthrough experiment. The breakthrough curves for the four materials are plotted below on a mass normalized axis. The total quantity of CO₂ adsorbed follows the trend: molecular sieve 5A > zeolite 13X > Fe-BTC > MIL-53(Al). The table below shows the total quantity adsorbed in mmol/g.

 

MATERIAL	CARBON DIOXIDE ADSORBED(MMOL/G)
ZEOLITE 13X	2.94
MOLECULAR SIEVE 5A	3.52
MIL-53 (AI)	1.23
FE-BTC	2.30

HIGH-PRESSURE ADSORPTION

Zeolite 13X has been extensively studied for applications in catalysis and adsorption. In this study, zeolite 13X was used as an adsorbent for carbon dioxide adsorption to collect breakthrough curves from 1 – 10 bar pressure. These measurements were collected using equimolar flowrates of 10 sccm nitrogen and 10 sccm carbon dioxide. A 1 sccm stream of helium was used as a tracer gas to determine the start of the breakthrough experiment. All measurements were collected at an analysis temperature of 30°C. Between each measurement, the zeolite 13X sample was reactivated overnight to ensure complete desorption of carbon dioxide. The figure shows a consistent increase in breakthorugh time across successive experiments as the pressure is increased.

 

Following carbon dioxide breakthrough measurements an equilibrium adsorption quantity was calculated for each curve by solving the breakthrough equation. Next, an isotherm was constructed displaying the quantity of carbon dioxide adsorbed at 1, 2, 3, 5, 7, and 10 bar total pressure. At 10 bar, zeolite 13X adsorbed roughly 15 mmol/g carbon dioxide. While isothermal data collected via breakthrough cannot be directly correlated with static adsorption measurements, it can provide an assessment of an adsorbent in process-relevant conditions.