Study on hydrophobic adsorption of VOCs by alkali-treated hierarchical titanium silicalite zeolites
China's energy structure will likely remain dominated by coal combustion for a period of time.Titanium silicalite zeolites(TS-1)with MFI topology were adopted for adsorption and reduction of VOCs in coal-fired flue gas treatment in this work.We treated the zeolites with alkali solutions(NaOH,NH4 OH,TPAOH)of different strength and properties to construct a differentiated hierarchical pore structure.The relative content of Si—OH groups(including isolated Si—OH groups on the outer surface and hydroxyl nests at internal defect sites)was also regulated in order to improve VOCs hydrophobic adsorption capacity.The changes of zeolitic framework structure,internal defects and other relevant properties were investigated using XRD,BET,UV-vis,IR,SEM and TEM.The re-sults showed that the NaOH solution treatment significantly etched the framework,leading to a decrease in ordered pores and increase in defects,which resulted in a sharp decrease in adsorption capacity.NH4 OH solution could dredge the pores and remove amorphous silicon species,improving the adsorption performance of VOCs,but the hydrophobic ability decreases slightly.The dissolution-recrys-tallization effect in TPAOH treatment process led to the formation of numerous ordered zeolitic frame-works.The development of micropores was significantly improved,and the internal defects were re-paired,resulting in a significant improvement of hydrophobic adsorption performance of VOCs.The ad-sorption capacity of VOCs was increased by 50％,and the static water adsorption capacity was reduced by 18％.
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维普
