Synthesis Of Typical Zeolitic Imidazolate Frameworks And Their Adsorption Properties For Furfural And 5-Hydroxymethylfurfural

With the rapid development of the economy,the fossil resources and the increasing environmental problems make the development and utilization of renewable biomass resources more and more concerned.Furfural and5-hydroxymethylfurfural are important platform compounds based on biomass resources that can directly or indirectly prepare many important chemicals.According to the current production process,the concentration of furfural and5-hydroxymethylfurfural in the stock solution to be separated and purified is low.In order to obtain the pure furfural and 5-hydroxymethylfurfural,it is necessary to enrich the low concentration furfural and 5-hydroxymethylfurfural stock.Compared with distillation,extraction and membrane separation,adsorption methods is a separation method with relatively simple operation,lower energy consumption,and environmentally friendly.Adsorption separation performance still depends on the further optimization of adsorbent materials or the development of new adsorbent materials.Zeolitic imidazolate frameworks materials（ZIFs）have both high stability of zeolites and large pore volume of metal organic frameworks materials,and ZIFs can change the pore size and hydrophobic through regulate the group.Based on these advantages,four hydrophobic ZIFs were studied in this paper:the synthesis,characterization and adsorption separation properties for furfural and 5-hydroxymethylfurfural.The main research contents and conclusions are as follows:（1）Four hydrophobic materials with different aperture were synthesized by different ligands:ZIF-8,MAF-6,MAF-5 and ANA-2PIm,of which ZIF-8 and MAF-6 is ZIFs material with round pore,their aperture are 3.3?and 7.4?,respectively.MAF-5 and ANA-2PIm ZIFs material with oval pore,and their aperture are 7.5*4.9?和7.4*3.6?,respectively.The materials were characterized via X-ray diffraction,scanning electron microscopy,Fourier transform infrared,thermo gravimetric and N₂ adsorption and desorption and water vapor adsorption.（2）The relationship between ZIFs（ZIF-8 and MAF-6）with round pore size and the adsorption properties for furfural and 5-hydroxymethylfurfural was studied.The static adsorption and fixed-bed dynamic breakthrough properties were investigated.The experimental results show that the adsorption amount of furfural and 5-hydroxymethylfurfural is MAF-6≈ZIF-8.This is because the pore volume of the two materials is approximative:MAF-6（0.69cm³/g）≈ZIF-8（0.70 cm³/g）.From the perspective of fixed bed breakthough,compared with MAF-6,ZIF-8 has a long dynamic breakthough time for one-component furfural and a low dynamic adsorption capacity for one-component 5-hydroxymethylfurfural,which is related to small pore aperture of ZIF-8 that it is not conducive to the adsorption and diffusion of furfural and5-hydroxymethylfurfural,while the large pore aperture of MAF-6（7.4?）is close to that of furfural or 5-hydroxymethylfurfural,which make furfural or5-hydroxymethylfurfural adsorb and diffuse rapidly.Thus,MAF-6 is a static and dynamic adsorption separation material with excellent performance.（3）The relationship between ZIFs（MAF-5 and ANA-2PIm）with oval pore and the adsorption properties for furfural and 5-hydroxymethylfurfural were studied.The static adsorption and dynamic bed breakthough were studied.The static and dynamic adsorption experimental results of one-component show that compared with MAF-5,ANA-2PIm hardly adsorbs 5-hydroxyfurfural.Further two-component breakthough experiment shows the ANA-2PIm material has a screening effect for two-component furfural and 5-hydroxymethylfurfural.This is because MAF-5 and ANA-2PIm are both ANA topolopy and oval pore,but ANA-2PIm allows furfural to pass through the pore and the 5-hydroxyfurfural is repelled through changing pore aperture via regulating group,thereby it act on screening effect for furfural and 5-hydroxymethylfurfural.