Study Of Chlorine Adsorption Properties On Modified 13X, NaY And Mordenite Molecular Sieves

Chlorine is a very important basic chemical raw material in the chlor-alkali industry. Chlorine has been used extensively in industrial, agricultural and other areas, and it is convenient for daily life and created wealth. As demands for chlorine increased, there have been large amounts of chlorine gas in industrial. We have to wellhandle this problem otherwise it would endanger on human health, the growth of plants and animals and lead to the irreversible negative influence on the environment. The handling of chlorine-gases become a serious problem in industrial fields because the exhaust containing chlorine gas source is highly complex. Recently adopting solid adsorbents have been a new ideal method for adsorption-separation chlorine-gases, therefore, exploring a new efficient absorbent is a very meaningful work.The research progress of chlorine adsorption properties was reviewed. This paper studied the chlorine adsorption properties on 13X, NaY and mordenite molecular sieves before and after modified pretreatment with the P-C-T apparatus. The stability of the three types of molecular sieves were characterized and analyzed by SEM, X-ray diffraction and FT-IR spectroscopy.The main conclusions are as following.1. The characteristic IR bands of 13X, NaY and mordenite molecular sieves revealed that the existing framework structure of molecular sieves before and after modified pretreatment, which can indicate that the main structure remains unchanged after the adsorption of chlorine. The characteristic IR peaks of NaY and mordenite zeolite shifted to a lower value after chlorine adsorption, suggesting that the formation of complex compound of C2O42- with aluminium. After chlorine adsorption, the diffraction peaks intensity of three types of modified pretreatment molecular sieves declined slightly, which may be caused by the combination of chlorine and Al-OH or Si-OH, and also may be caused by the trace of acid in chlorine.The increasing diffraction peaks intensity of the XRD patterns of the three modified pretreatment molecular sieves indicating that on one hand impurities in the zeolites were removed; on the other hand internal structure and pore size of the molecular sieves were changed by modification. The diffraction peak intensity of the three modified zeolites decreased slightly after chlorine adsorption, which showed that the framework structures of the molecular sieves were demaged in some parts after adsorption and the sequencing intensity were declined.2. Experimental data showed that the adsorption capacities of the three modified molecular sieves were NaY-1 zeolite> mordenite zeolite> 13X-3 at 0℃,30℃,50℃and 0.20 MPa. The experimental data showed that the chlorine uptaking in the zeolites were strongly dependent on the internal (pore volume, pore size, surface interactions, framework structure) and external (temperature, pressure and acidity) factors. NaY and mordenite molecular sieves after modified pretreatment with larger pore volume and pore size may have resulted in the higher adsorption capacity than the 13X-3 zeolites. Therefore, the main factors which affected the adsorption capacity of the three types of modified molecular sieves were large cage and channel size close to the kinetic diameter of a chlorine molecule.3. The adsorption curves of 13X, NaY and mordenite after modified pretreatment were studied at different temperature of 0℃,30℃and 50℃. The results showed that the amount of chlorine absorption rised with temperature falling and pressure rising. Moreover, the adsorption is classified as physical process because the adsorption curves confirm to the Langmuir equation.