Preparation And Methane Adsorption Properties Of Metal-organic Frameworks

Natural gas (methane) is considered as an ideal vehicle fuel due to its environmental protective, economy and safe. However, the application of natural gas in Vehicle has been limited by the difficulties in on-board storage. Adsorption nature gas is considered a most prospective storage method. And the key of adsorption nature gas is to develop efficient adsorbents. A new type of porous materials, metal-organic frameworks, is believed to be a kind of very potential nature gas adsorbent, which has large surface area, designable pore texture and several advantages. This dissertation is mainly concerned with study on methane adsorption onto several novel metal-organic frameworks, MOF-5, ZIF-8, ZIF-62, MIL-101and HKUST-1. This research mainly involves synthesis and characterization of the MOF-5 crystals, determination of CH4 adsorption thermodynamics on the MOF-5, ZIF-8, ZIF-62, MIL-101and HKUST-1 particles. This study tries to answer the questions of engineering application and adsorpion science, like the uptake of CH4 at different temperature or under different pressure and so on, which has scientific research value and practical significance.The effects of synthesis condition on physical properties of MOF-5 crystals, including the morphology, crystal structure and porous texture were investigated. SEM, XRD and N2 adsorption/desorption were used to characterize the morphology, crystal structure and porous texture properties of MOF-5 crystals. Results showed that MOF-5 crystals whose partical sizes ranged from 40 to 70μm and surface area was up to 2595m2/g were obtained under the following conditions: synthesis temperature of 130°C, reaction time of 4 hours, the Zn2+/BDC molar ratio of 2.64 and N, N-diethylformamide as the solvent.Adsorption equilibriums of CH4 on the MOF-5, ZIF-62, MIL-101 and HKUST-1 particles were studied by using gravimetric method. The isosteric adsorption heat of CH4 on the MOF-5, MIL-101 and HKUST-1 were estimated. Results showed that CH4 adsorption behavior can be accurately described by Langmuir isotherm equation; HKUST-1 had the largest amount of CH4 adsorbed compared to the other MOFs crystals investigated in this work. The amount adsorbed of CH4 on the HKUST-1 was up to 93.8mg/g at 299.15K and 40bar. The isosteric adsorption heats of CH4 on the MOF-5, MIL-101 and HKUST-1 particles were in the range of 10.85-8.14kJ/mol, 15.75-13.23kJ/mol and 18.02-9.03kJ/mol, respectively.Methane adsorption properties onto ZIF-62 and SBA-15 were studied in this research. Results showed that the amount adsorbed of benzene on the ZIF-62 was more than that on the SBA-15 if p / po≤0.4. Asorption isotherm of benzene on ZIF-62 was typical type-I adsorption isotherm. The equilibrium amount adsorbed of benzene on the ZIF-62 was up to 185mg/g. And sorption of benzene on ZIF-62 conforms to pseudo-first-order equation.