The Synthesis Of MOFs Materials With Oxygen Adsorpty And The Research Of Its Performance

Coal bed methane is a kind of important unconventional gas energy. Due to the presence of oxygen, coal bed methane has an explosion hazard in the enrichment of CH4. So the O2removing is one of the key factors in the process of coal bed methane enrichment of industrialization. At present, there are many technology of the O2removing. For example, catalytic combustion, low temperature liquid separation, pressure swing adsorption separation and chemical adsorption technology, etc. Among them, chemical adsorption technology has a good industrial application prospect, and the core technology of chemical adsorption is the adsorbent. Therefore, the research and development of new materials is an important subject area.As a new material, the function of metal-organic frameworks materials (MOFs) has become the research focus. Since Jeffrey group reported Cr3(BTC)2with a high oxygen adsorption capacity (11wt%mass fraction), the oxygen absorbent of MOFs materials showed good application prospect in coal bed methane. In this paper, We use different synthesis methods and conditions to obtain the oxygen absorbent of MOFs materials having an oxygen adsorption performance and based on Fe, V:Fe2(dobdc), MIL-101Vand MIL-100V. At the same time, the optimum synthesis conditions of each reaction were explored. We get the characterization of materials in detail by using XRD, TG and SEM, and used IGA to obtain detailed performance of oxygen and water sensitivity. The main research contents and conclusions include the following aspects:(1) The optimum synthesis conditions of the sample Fe2(dobdc)(A): reaction material mole ratio of FeCl2/H4dobdc is5mmol/2mmol, DMF is50mL and methanol is6mL. Under the393K temperature, the reaction material in three flask react18to22h. the optimum synthesis conditions of sample Fe2(dobdc)(B):material FeCl2/H4dobdc mole ratio is1mmol/0.4mmol, DMF is10mL and methanol is1.2mL. Under the403K temperature, the material react20h in kettle.Though the oxygen adsorption performance at298K temperature knowable oxygen adsorption quantity of sample is8.0wt%, it shows that this method is very good to protect the metal vacancy in the material. According to oxygen stripping quadratic curve and the oxygen adsorption curve, the oxygen adsorption material is irreversible chemical adsorption. Because the electron cloud density of unsaturated Fe (Ⅱ) is big and the acting force is strong between oxygen and Fe (Ⅱ) to form the chemical bonds. But under the200K low temperature, unsaturated Fe (Ⅱ) and oxygen reaction has been weakened. The adsorption of material to oxygen becomes reversible physical adsorption. Sample Fe2(dobdc)(B) has5.11wt%of oxygen ability. And under the298K, material also does not have oxygen secondary adsorption capacity.According to water sensitivity data of samples, material lost oxygen adsorption ability after water treatment. This is because water molecules will occupy unsaturated Fe (Ⅱ) site of A and B material structure to form the stable chemical bonds after the water molecules contact materials. This states the water molecules can make sample Fe2(dobdc)(A) and sample Fe2(dobdc)(B) metal site inactivation.(2) The optimum synthesis conditions of the sample MIL-100V:reaction material mole ratio of VC13/H3BTC is2.4mmol/1.68mmol and H2O is4mL. Under the473K temperature, the reaction material react72h in reaction still.According to primary and secondary oxygen isothermal stripping absorption curve of MIL-100V sample at298K, we found that MIL-100V has an oxygen adsorption performance of2.77wt%. But it does not have secondary adsorption of oxygen. Under the200K low temperature, interaction force between unsaturated V(Ⅲ) and oxygen is reduced. This has prompted the adsorption of material for oxygen is reversible.According to adsorption data of MIL-100V, the material MIL-100V not only have structural stability but also water molecules have very good protection effect to having oxygen MIL-100V unsaturated metal slots. This is due to the composite materials under water and oxygen, water molecules dominate the unsaturated metal site. In the air, oxygen cannot replace water molecule. Water molecules will removal from the metal seats through activation, and material won the oxygen adsorption capacity.(3) The optimum synthesis conditions of the sample MIL-101V(DMF): reaction material mole ratio of VC13/H2BDC is1.9mmol/0.92mmol and DMF is3mL. Under the423K temperature, the reaction material in reaction still react24h. The optimum synthesis conditions of sample MIL-101V(MeOH):material VC13/H2BDC mole ratio is1.9mmol/0.92mmol and MeOH is3mL. Under the423K temperature, the material react24h in reaction still.Though the oxygen adsorption performance of MIL-101(DMF) at298K temperature knowable oxygen adsorption quantity of sample is2.5wt%. According to the oxygen release curve and oxygen second adsorption curve, samples do not have secondary oxygen adsorption capacity. Because the electron cloud density of V(Ⅲ) is big, the acting force is strong between oxygen and V(Ⅲ) and the electron clouds of the V (Ⅲ) transfer to oxygen. Thus the chemical bonds form. But under the200K low temperature, oxygen reaction of material is reversible. Having a similar situation with MIL-101(DMF), sample MIL-101V(MeOH) have1.9wt%oxygen adsorption capacity, but oxygen adsorption is irreversible.According to water sensitivity data of samples MIL-101V (DMF), water molecules still have good protection effect to unsaturated metal site of MIL-101V(DMF) in the present of oxygen environment. This is because water molecules will replace DMF object molecules to adsorb on the metal site after water treatment. And in the air, oxygen is not enough to replace the water molecules. The material remove the water molecules in the structure activation by excitation to regain the unsaturated metal site, namely the oxygen adsorption capacity.