Kinetics Of Removal Of Hg~0 By Copper-modified ZSM-5 Molecular Sieves

The mercury in exhaust gas with high pollution and multi-hazard is difficult to be removed.It is an effective way to control mercury pollution by the catalytic oxidation of elemental mercury into oxidized mercury,which is easy to be captured and removed.The key problem of this approach is the preparation of high efficient mercury removal adsorbent.It not only has important theoretical significance and engineering value of flue gas,but also has the reference and guiding significance for the development and application of similar mercury adsorbent for studying on modification and Hg⁰ adsorption kinetics mechanism of mercury removal adsorbent for improving Hg⁰ removal efficiency and reducing the cost of application of mercury removal adsorbent.This paper prepared Cu-ZSM-5 molecular sieve adsorbent for mercury removal selecting ZSM-5 molecular sieve as carrier of preparation high efficient economic mercury sorbent,CuCl₂,Cu?AC?2,CuSO4,Cu?NO3?2 as the active material modified by impregnation method.XRD,BET,SEM,FT-IR etc.methods were used to comparative analysis the characterization of ZSM-5 zeolite before and after modification.Under the same condition,the mercury removal performance of Cu-ZSM-5 molecular sieve was tested on small fixed bed mercury removal reaction system,screening the best copper-based modified materials.The adsorption behavior of Hg⁰ was investigated by kinetic experiments and kinetic models at different adsorbent dosage,adsorption temperature and flow rate.Materials Studio software was used to simulate the adsorption of Hg molecule on Cu-ZSM-5 molecular sieve to study on adsorption characteristics from microcosmic point of view.XRD,FTIR,EDS and XPS tests were used to characterize the Cu-ZSM-5 molecular sieve before and after the adsorption of Hg,revealing catalytic oxidation mechanism of Hg⁰ by Cu-ZSM-5 zeolite.The main results and conclusions are as follows:?1?ZSM-5 molecular sieve crystallinel has not been changed,the specific surface area decreased with the increase of load,the pore size distribution unchanged,and Cu was successfully introduced into molecular sieve after copper-based impregnated modification.Hg⁰ removal performance of Cu-based modified molecular sieve improved than that not modified.The best material for removing mercury is ZSM-5 molecular sieve modified by2.5wt% CuCl₂.The penetration rate of CuCl₂-ZSM-5 molecular sieve adsorption Hg⁰ decreased with adsorbent dosage increaseing,increased with temperature rising,rose with air flow rate increasing.Mercury adsorption capacity unit decreased with adsorbent dosage,temperature,and air flow rate.Under the conditions studied,pseudo-second-order model could well describe the adsorption process of Hg⁰ on CuCl₂-ZSM-5 zeolite.?2?The loading capacity of ZSM-5 zeolite cell to copper material through MS simulation is CuCl₂ > CuSO4 > Cu?NO3?2 > Cu?AC?2.ZSM-5 zeolite has higher loading capacity for CuCl₂.The temperature affects the adsorption amount and adsorption isotherm of Hg molecule on molecular sieve.With the increase of temperature,the adsorption amount of mercury decreased following Langumir single molecular layer adsorption model.Mercury molecules are mainly adsorbed in the pores of molecular sieves with a large number of adsorption sites on the surface.?3?Cu-ZSM-5 molecular sieve after adsorption of Hg was characterized,showing that the molecular sieve surface had more catalytic oxidation of mercury removal functional groups which could oxidize Hg⁰ to Hg2+,following the Mars-Maessen reaction mechanism.?4?The CuCl₂-ZSM-5 molecular sieve can be used as a high efficient mercury removal adsorbent for the control of Hg⁰ in coal fired flue gas because of its good mercury adsorption performance and catalytic oxidation efficiency.