Synthesis And Adsorption Properties Of Hydrophobic Porous Materials

Industrial VOCs exhaust gas contains a certain amount of toluene and moisture.Toluene is a highly carcinogenic substance,which can stimulate the human nervous system and harm human health.In order to avoid the interference of water vapor when adsorbing toluene in VOCs,a hydrophobic adsorption material should be selected.ZSM-5 molecular sieve porous material has a large specific surface area,adjustable pore structure and multiple adsorption sites.It is a good adsorbent,and the hydrophobic property can be improved to effectively adsorb toluene.Using industrial by-product micro-silica powder as the silicon source and sodium metaaluminate as the aluminum source,the ZSM-5 molecular sieve porous material was synthesized by hydrothermal method.This paper systematically studied the influence of the reaction feedstock silicon-to-aluminum ratio,water-silicon ratio,crystallization temperature,crystallization time,p H value,type and amount of template agent and other conditions on the synthetic materials.The results showed that: the feeding ratio of silicon to aluminum was 19,the ratio of water to silicon was4.15,the p H was 13.60,the crystallization temperature was 180°C,the crystallization time was 72 h,the template was Tetrapropyl Ammonium Hydroxide,and the amount was 10 g.This is the optimal reaction condition.The ZSM-5 molecular sieve porous material synthesized under this condition has a specific surface area of 377 m2/g,a micropore area of 336 m2/g,a micropore volume of 0.18 ml/g,and an average pore diameter of 3.06 nm.The self-synthesized ZSM-5 molecular sieve porous material was modified by the method of silanization modification.The modifiers used were triethoxymethylsilane(TMS)and methyltrimethyloxysilane(MTMS).Two organosilane modifiers with different molecular sizes.The results show that the ZSM-5 molecular sieve porous materials modified with different addition amounts of modifiers all exhibit strong hydrophobic properties,and the hydrophobic angles are mostly close to 150°.Among them,the hydrophobic angle of the material reached the maximum value of 164° when the amount of TMS added was 0.24 g,achieving super hydrophobicity.When RH=80%,the adsorption amount of toluene was 17 mg/g;when the amount of MTMS added was 0.08 g The hydrophobic angle of the material reaches the minimum value of 140°,and the adsorption capacity of toluene is 60mg/g at RH=80%.In summary,as the amount of modifier added increases,the amount of toluene adsorbed by the hydrophobic material shows a decreasing trend.When RH=80%,the hydrophobic material with the highest adsorption capacity is0.08-MTMS-ZSM-5,the adsorption capacity is 60mg/g,followed by0.08-TMS-ZSM-5,the adsorption capacity is 59mg/g.Compared with the unmodified ZSM-5 molecular sieve porous material,their toluene adsorption capacity increased by 78% and 77%,respectively.The results show that the surface silanization modification method has greatly improved the hydrophobic properties and toluene adsorption properties of the self-made ZSM-5 molecular sieve,especially the small molecular weight MTMS modifier.