Metal Organic Frameworks, or MOFs as they are commonly known, are crystals used as adsorbents in oil and gas operations.
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The material has the largest internal surface area known to man and has been successfully researched for many clean energy solutions such as pollution reduction and vehicular light gas delivery. framergy Inc., a Texas based company that pioneered the sector in 2011, has been exploring the materials for cleaning hydrogen produced from natural gas reformation. In framergy’s system, the use of surface area and intermolecular interactions can replace costly separation methods to a measurable degree.
When hydrogen is produced from fossil fuels, reformation-based hydrogen generation processes leave residual hydrocarbons in the outlet process stream. These impurities are detrimental to the gas transportation infrastructure and hydrogen-driven power generators such as fuel cells. framergy used its AYRSORB™ F250, based on MOFs PCN-250 and MIL-127 (available for research purposes through Strem Chemicals), to demonstrate that a MOF-based polishing approach is capable of upgrading contaminated hydrogen streams to fuel-cell quality product purity.
In 2019, the Company conducted a series of hydrogen purification tests from a simulated process plant gas stream containing 5% methane and 95% hydrogen. A 500 mL canister (Canister 1) was packed with 245 g of AYRSORB™ F250 filled at with the simulated gas stream for a single-stage separation test. Pressure was released in stages and samples were analyzed at each stage in pressures ranges between 780 - 1600 psig. At the highest pressures analyzed, 1400 - 1600 psi, hydrogen gas was successfully purified to above 99%. After the MOF was saturated with methane, the purification efficiency decreased to 2%, which was still 60% less methane in the treated hydrogen stream than the source concentration.
A continuous mode system was designed to also test the purification efficiency of AYRSORB™ F250. A pressure controller downstream of the canister was installed to regulate the pressure exiting the canister since the mass flow controller operating pressures is lower than process operating pressure. After the mass flow controller, samples from the process stream were analyzed with an Agilent 6850 Gas Chromatograph (GC). Tests were conducted at 1000 psig and room temperature with a 10 sccm (standard cubic centimeters per minute) flow rate. The test results demonstrated that AYRSORB™ F250 captures methane and a pure stream of hydrogen was achieved initially in the process. For the first 96 minutes at this scale, methane concentration was below the source concentration.
Industrial hydrogen processes typically run at higher pressures, making this a leverageable quality at a typical plant. AYRSORB™ F250 used by framergy clearly showed that this technology could be deployed to clean hydrogen. With the proliferation of hydrogen as a new source of clean energy, especially in the automotive industry, MOFs have a new gas purification horizon.
Originally authored by O.K.Ray Ozdemir, Carlos Ybanez & Jason Ornstein