Experimental study on thermal effect on infiltration mechanisms of glycerol into ZSM-5 zeolite under cyclic loadings

Understanding the fundamental infiltration mechanisms under thermal response is of crucial importance to design and develop nanoporous energy systems. In this work, a glycerol/ZSM-5 zeolite-based pressure-driven energy absorption system was built, while the temperature-dependent intrusion of glycerol molecules into lyophobic nanopores of ZSM-5 zeolite and the underlying mechanisms were experimentally studied. By changing the system temperature, the correlations of infiltration pressure with the infiltration and defiltration percentages of the liquid phase under thermal response were explored. It turns out that lifting the system temperature will reduce the critical infiltration pressure barriers and change the system's wettability. The equivalent surface tension and contact angle are calculated to elucidate the thermal dependence of the system's wettability. Elevating system temperature can also help enlarge the entry area of the nanochannels and trigger more glycerol molecules to flow out of the nanochannels, which means an increase of the infiltration and defiltration percentages. Weakened hydrogen bonding interaction, temperature sensitivity of glycerol viscosity, and the inherent gas phase in the nanoporous channels may contribute to the infiltration and outflow process at a higher temperature level. Cyclic loadings were applied under each working condition to test the recoverability of the built system. Results showed that the system's throughput shrank in the first three/four cycles and became stable afterwards. Lifting the system temperature could enhance both intrusion and extrusion processes, thus helping the system reach a faster throughput balance, which is beneficial in establishing a recoverable and reusable energy absorption/storage/conversion system. © 2016 IOP Publishing Ltd.