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Natural gas whose major component (85?95%) is methane, has three advantages: natural abundance, low cost, and clean burning as the first alternative fuel. Now the storage and transport technology of natural gas is sticking point to achieve this target. Among the natural gas storage technology, adsorptive natural gas (ANG) has attracted more attention, because of the lower energy consumption, rapid adsorption-desorption rate and good reversibility and kinetics.This paper investigated methane storage capacities of zeolites and MOFs. And the influence of microporous structure (channel diameter, pore volume and cave structure) were discussed. The primary contents and results are as follows:1. The influence of activation temperature on methane storage capacity of zeolites FAU and LTA was investigated. The results show that the best activation temperature was 500℃; the methane storage capacity of them at pressure 2 MPa, temperatures 194.5 K, 273 K and 303 K, are 7.5 mmol.g-1, 4.3 mmol.g-1, 3.5 mmol.g-1 and 6.8 mmol.g-1, 3.5 mmol.g-1, 2.9 mmol.g-1 respectively; the zero-coverage isosteric heats of them are 9.5 kJ.mol-1 and 21 kJ.mol-1.2. The methane storage properties of zeolites LEV and MAZ were investigated. The results show that the methane storage capacity of them at pressure 2 MPa, temperatures 194.5 K, 273 K and 303 K, were 3.7 mmol.g-1, 2.4 mmol.g-1, 2.1 mmol.g-1 and 2.9 mmol.g-1, 2.4 mmol.g-1, 2.1 mmol.g-1; the zero-coverage isosteric heats of them were 19 kJ.mol-1 and 17 kJ.mol-1.3. The methane storage capacities of zeolites LEV, MAZ, FAU, LTA and mesoporous material SBA-15 were compared. The results show the order of their methane storage was FAU﹥LTA﹥LEV≈MAZ﹥SBA-15 at 273 K and 303 K, but at 194.5 K, the order was FAU﹥SBA-15﹥LTA﹥LEV﹥MAZ. The relationship between methane uptake and the structure (channel diameter, pore volume and cage structure) proved that the best methane adsorption channel diameter was 8 ? and the cage structure was essential to methane uptake.4. The methane storage properties of aluminum-phosphate molecular sieves AlPO-53, SAPO-34 and AlPO-5 were investigated. The results show that the methane storage capacities of them at pressure 2 MPa, temperatures 273 K and 303 K, were 1.5 mmol.g-1, 2.3 mmol.g-1, 1.3 mmol.g-1, and 1.2 mmol.g-1, 1.2 mmol.g-1, 2.1 mmol.g-1; the zero-coverage isosteric heats of them were 17 kJ mol-1, 10 kJ.mol-1 and 19 kJ.mol-1. The relationship between methane uptake and the structure (channel diameter, pore volume and cage structure) also proved that the cage structure was important to methane uptake. It was impossible for the material possessing optimum channel diameter but no cage structure to have excellent storage capacity.5. The methane storage properties of MIL-100 , MIL-96(Cr) and Cu3(BTC)2 were investigated. The results show that the methane storage capacity of them at pressure 2 MPa, temperatures 273 K and 303 K, are 4.5 mmol.g-1, 3.8 mmol.g-1, 3.8 mmol.g-1, and 3.5 mmol.g-1, 3.2 mmol.g-1, 3.0 mmol.g-1; the zero-coverage isosteric heats of them are 5 kJ.mol-1, 20 kJ.mol-1 and 17 kJ.mol-1. The comparison of the experiment data and reference data presented that crystallinity played a great part in methane uptake. The methane storage capacity of single crystal was larger than that of powder crystal. MOFs with the same structure but different metal ions had similar methane uptake, that is, metal ions were not important for methane uptake.6. The variation of the free-energy change ( ) decreased with increasing temperature and adsorption amount. Low temperature was beneficial for adsorption. Spontaneous process turned into unnatural as the adsorption amount increase.
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