Methane storage using metal-dipyrazolate frameworks

Area of Science:

• Materials Science
• Chemical Engineering
• Energy Storage

Background:

• Adsorbed natural gas (ANG) storage offers a safer, more cost-effective alternative to conventional methods.
• Current ANG storage is limited by low deliverable gas capacity and material instability.
• Flexible porous materials, like metal-organic frameworks (MOFs), show promise for enhanced ANG storage.

Purpose of the Study:

• To develop novel flexible porous materials for efficient adsorbed natural gas storage.
• To overcome the hydrolytic instability and pelletization challenges of existing ANG sorbents.
• To achieve high methane deliverable capacities at ambient temperatures and low pressures.

Main Methods:

• Synthesis of a family of metal-bipyrazolate frameworks, including Zn(dpt) and Co(dpt).
• Investigation of methane-induced reversible narrow-pore and large-pore phase transformations.
• In situ structural characterization, high-pressure gas sorption, and computational modeling.
• Testing of material performance in 250-ml tanks and evaluation of formulation approaches for pelletization.

Main Results:

• Zn(dpt) and Co(dpt) frameworks exhibit reversible structural transformations upon methane adsorption.
• Zn(dpt) demonstrates exceptional methane deliverable capacities: 173 cm³(STP)/cm³ at 5-35 bar and 225 cm³(STP)/cm³ at 5-65 bar.
• Zn(dpt) shows excellent hydrolytic stability, unlike previous flexible sorbents like Co(bdp).
• High deliverable capacity was maintained over multiple adsorption-desorption cycles.
• A formulation approach provided a practical alternative to traditional pelletization.

Conclusions:

• Metal-bipyrazolate frameworks, particularly Zn(dpt), represent a significant advancement in adsorbed natural gas storage.
• The developed materials offer high methane deliverable capacity, enhanced stability, and practical processability.
• These findings pave the way for more efficient and cost-effective natural gas storage solutions.