| Metal–organic framework materials are widely applied to molecule separation and catalysis due to their high specific surface area,tunable cavities,bare metal sites,good stability and stable framework structure.Microfibrous materials with adjustable shape and thickness can obviously enhance the contacting-efficiency,heat transfer efficiency and decrease the bed pressure drop because of the high voidage three-dimentional network structure and good mechanical strength.Thus,microfibrous metal organic framework membranes could effectively combine the advantages of MOFs material and microfiber substrates,making it promising in various applications.Firstly,the preparation technique of microfibrous ZIF-8 membranes and its application in absorption of isopropanol were investigated.The paper-like stainless steel fiber?PSSF?supports were prepared by wet lay-up papermaking and sintering process,then the ZIF-8membrane coated PSSF support was synthesized via seeded growth and solvothermal synthesis method.The effects of the seed layer growth time,the Hmim/Zn molar ratios,the solvothermal synthesis temperature and the solvothermal synthesis time on properties of ZIF-8 membrane/PSSF composites were investigated.The synthesized ZIF-8membrane/PSSF composites were characterized by SEM,XRD,N2 adsorption and desorption isotherms,TG and FT-IR.The experimental results indicated that the optimal conditions were80 of Hmim/Zn2+molar ratios,12 h of seed layer deposition time,24 h of solvothermal synthesis time and 100?of solvothermal synthesis temperature.Under the optimal conditions,ZIF-8 membrane/PSSF composites showed outstanding continuity,compactness,free-defect and crystal shape.The specific surface area was 398 m2/g,the total pore volume was 0.174 cm3/g,the void volume of ZIF-8 membrane/PSSF composites reached to 89%,the thermal stability conducted up to 450?.Compared with the structured fixed bed filled with ZSM-5 particles,the adsorption dynamics of isopropanol in the structured fixed bed filled with ZIF-8 membrane/PSSF composites indicated that microfibrous ZIF-8 membrane could obviously improve the adsorption efficiency,reduce mass transfer resisdance.It was observed that the bed utilization??Z?decreased from 75.2%to 48.7%and the rate constant?k'?increased from 0.0360 min-1 to 0.0437 min-1 in the ZIF-8/PSSF structured fixed bed,as the flow rate of isopropanol increased from 50 mL min-1 to 150 mL min-1.The values of rate constant and the?Z in the fixed bed with ZIF-8 membrane/PSSF increased by 6%and 7.8%,respectively,compared with that of commercial ZSM-5 zeolites at the flow rate of 100 mL min-1.Secondly,the preparation technique of microfibrous HKUST-1 membranes and its application in the catalytic wet peroxide oxidation of phenol in a structured fixed bed reactor were investigated.The HKUST-1 membrane/PSSF catalysts were characterized by SEM,XRD,XPS,TGA and FT-IR.The results indicated that the catalyst showed a specific surface area of 376.72 m2 g-1,the total pore volume was 0.178 cm3 g-1,the pore size distributed mainly in a value of 1 nm,and the catalyst was stable in the air to 320?.The loading amount of HKUST-1 on the PSSF support was estimated to be 15.70%.The effects of the temperature,catalyst bed height,and the feed flow rate on the catalytic performance of the membrane were investigated.The experimental results showed that the efficiencies of HKUST-1membrane/PSSF were enhanced with the increase of the temperature,and the conversion of phenol,H2O2,TOC were improved with the increase of the catalytic bed height and the low feed flow rate which accounted for the longer residence time.Under the optimal condition,the bed height was 3 cm,the catalytic temperature was 80?,the feed flow rate was 2 mL min-1,the conversion of phenol reached 100%and the conversion of TOC was 70%,and the phenol could be totally into transformed into low-molecular products,indicating that HKUST-1/PSSF catalysts was potential for the catalytic wet peroxide oxidation of phenol in a structured fixed bed reactor. |
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