Biomethane as a promising renewable carbon feedstock for the synthesis of zeolite templated carbons for hydrogen storage application

Abstract

Biogas, generated through the anaerobic digestion of organic matter, is an attractive renewable energy source due to its continuous production and utilisation cycle. Rising concerns about the environmental impact of fossil fuel-derived energy have sparked interest in developing sustainable energy alternatives. Consequently, considerable research efforts have been directed towards biogas valorisation, particularly its main component, methane (CH4). This is achieved by converting raw or upgraded biogas into high-value products, such as Zeolite-templated carbons (ZTCs), and concurrently producing cleaner hydrogen gas. ZTCs are highly ordered porous structures that exhibit high surface areas, uniform pore size distributions, and large pore volumes, rendering them attractive for various applications. These applications include gas storage, CO2 capture, supercapacitors and batteries. In this study, we focused on the utilisation of simulated biogas (CH4 and CO2 mixture) and pure CH4 (in this case, simulated ‘biomethane’) for the synthesis of zeolite-templated carbons (ZTCS). When CH4 was utilised on both the one-step and two-step processes, the obtained ZTCs had higher surface area and hydrogen (H2) adsorption. The highest surface area obtained was 2974 m2/g, while the best H2 storage capacity, at 1 bar, was 2.77 wt%. Structural (XRD) and morphological (SEM and TEM) characterisations were found to be indistinguishable from those of the samples obtained when fossil-derived ethylene was used as a carbon source. Unfortunately, ZTCs were not obtained when simulated biogas was used as a carbon source, due to the zeolite having a greater affinity towards CO2 than CH4, primarily because of the large quadrupole moment of CO2. This study has demonstrated that a sustainable source of carbonaceous feedstock, such as biogas-derived ‘biomethane’, can be converted into value-added products (ZTCs), thereby creating additional economic opportunities for industries within the biogas sector.