Adsorption separation of oxidative coupling of methane effluent gases. Mini-plant scale experiments and modeling

This work explored the use of a zeolite molecular sieve as adsorbent material in the separation of effluent gases from an oxidative coupling of methane (OCM) process. The molecular sieve granules were synthesized, characterized, and evaluated as adsorbent material at the mini-plant scale. Dynamic adsorption experiments were performed at different feed temperatures (298, 308, 328 K), with pure and mixed gases (ethylene, ethane, oxygen, nitrogen and carbon dioxide), and at different absolute pressures (2 and 6 bar). The breakthrough curves and the corresponding dynamic temperature profiles from the adsorption system were obtained under the different experimental conditions. According to results pressure swing adsorption can be used as a de-methanizing alternative during the OCM downstream separation, and even as an ethane/ethylene separation alternative. The adsorption capacities for the different gases, per unit mass of adsorbent, at 303 K and 5 bar were: 0.138 kgCO2/kg, 0.094 kg C2H4/kg, 0.082 kgC2H6/kg, and 0.020 kgCH4/kg. A model of the process was implemented within Aspen Adsorption software, and the transport parameters were adjusted to fit experimental observations. The computer model agreed with experimental results, and it can be used for further process up-scaling and techno-economic evaluation.