Microporous MOF-5@AC and Cu-BDC@AC Composite Materials for Methane Storage in ANG Technology

Novel composites (MOF-5 and Cu-BDC) based on economically activated carbon have been developed to investigate methane adsorption capacity for ANG applications. The composites were synthesized by adding MOFs precursor in two different weight percent (10% and 40%) to commercial activated carbon under solvothermal conditions (110-120 degrees C). The synthesized adsorbents were characterized by FT-IR, XRD, SEM, EDS, and BET techniques to gather information about their crystallinity, morphology, and specific surface area. A methane uptake measurement system based on the volumetric method was made to obtain methane adsorption capacity on each composite. Then, the amount of methane adsorption for each one was calculated, and the experimental data were compared with different isotherm adsorption models appropriate for gas adsorption, including Langmuir, Freundlich, and Dubinin-Radushkevich. This comparison showed that the best fitting belonged to the Langmuir isotherm model. Also, stability and kinetic studies were done for two MOF-5(40%) @AC and Cu-BDC40% @AC composites. In the kinetics study, experimental data were compared and analyzed in terms of pseudo-first order, pseudo-second order, and intraparticle diffusion models. The kinetics study showed that methane adsorption happens very fast on the synthesized adsorbents. The amount of methane adsorption at 35 bar and room temperature for pure activated carbon was specified as 4.32 mmol/g. The 10% and 40% of Cu-BDC with activated carbon are 5.59 mmol/g and 6.85 mmol/g, respectively. The capacity of MOF-5(10%) @AC and MOF-5(40%) @AC composites were obtained at 5.9 mmol/g and 7.3 mmol/g, respectively. Increasing methane uptake (70%) was obtained by adding 40 wt.% of MOF-5 to commercial activated carbon.