Landfill gas upgrading using amine-functionalized silica sorbents

ABSTRACT

Separation of acid gases such as CO₂ from biogas is a key step for its purification before biomethane is used in various applications such as injection into a pipeline or use as a vehicle fuel. In this study, the single step purification of real biogas (locally collected landfill gas) was demonstrated using (3-Aminopropyl) triethoxysilane (APTES)-grafted SBA-15. The sorbent was optimized between amine amount and accessibility to adsorption sites. In studies using a surrogate mixture of CH₄/CO₂ the sorbent recorded an adsorption capacity of 0.85 mmol_CO2/g_ads under dry conditions and this decreased to 0.72 mmol_CO2/g_ads when the surrogate biogas was saturated with steam. Even though the capacity was further decreased to 0.55 mmol_CO2/g_ads using real landfill gas, it remained fairly stable over 5 cycles despite the presence of impurities, namely hydrogen sulfide (68 ppm). In all cases, the capacity was regenerated with a thermal treatment in inert gas at 100°C. The results suggested possibilities for a single step purification unit to remove acid gasses and water and provide potential for a streamlined operation for the separation of carbon dioxide from biogas. The enhanced economics should propel the move toward a green energy future.

GRAPHICAL ABSTRACT

KEYWORDS:

• Landfill gas upgrading
• landfill disposal
• municipal solid waste
• biomethane

Acknowledgments

Parts of this manuscript were previously published in the Master’s thesis (Gopalakrishan, 2019) of one of the co-authors (UG).

Disclosure statement

Two authors (BJ and JNK) hold financial interests in T2C-Energy LLC, which is a startup commercializing a different technology to upgrade biogas to diesel fuel.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15435075.2022.2156293.

Availability of data and material

The datasets generated during and/or analyzed during the current study may be available from the corresponding author on reasonable request.

Additional information

Funding

The authors acknowledge funding from the Hinkley Center for Solid and Hazardous Waste Management.