Study On Adsorption Of Tetrachloroethane And Dichloromethane From Naphtha With Zeolites

Organic chlorine in naphtha were the main cause of corrosion of the equipment in the catalytic reforming process. In the paper, zeolites were made as the adsorbent to adsorb the organic chlorine in naphtha and were characterized by XRD, BET, NH3-TPD and TGA-DCS. The equilibrium adsorption amount of dichloromethane and tetrachlorothane at different temperature with adsorbent was measured. The best calcination condition and adsorption condition were determined. The adsorption isotherms of dichloromethane and tetrachlorothane were measured and fitted, the thermodynamic parameters were calculated. The kinetic curves were measured and simulated to determine the adsorption mechanism.The results showed that the increased acid sites of mild strong acid didn’t improve dechlorination of zeolites in the process of adsorbed tetrachloroethane. The specific surface area and pore size of zeolites was positive to the performance in the process of antichloration. The removal ratio of tetrachloroethane was 96.9% and equilibrium adsorption amount was 4.67 mg/g under the optimal adsorption and calciantion conditions. The adsorption isotherm of tetrachlorothane can be simulated by Freundlich adsorption equation. The adsorption enthalpy change △H=-12.56 kJ/mol, entropy change △S=-22.54 J/(mol·K), and Gibbs energy change △G< 0. The adsorption process can be simulated by pseudo second-order kinetic equation. According to the kinetic equation, the adsorption activation energy were calculated, and Ea was 17.193 kJ/mol. In the process of adsorbed dichloromethane, NiMCM-22 zeolites were the best adsorbent to adsorb dichloromethane. The presence of Ni2+ produced a strong mild strong acid which contributes to increasing the dechlorination capacity of MCM-22 zeolites. The removal ratio of dichloromethane was 97.0% and equilibrium adsorption amount was 4.73 mg/g under the optimal adsorption and calciantion conditions, which was increased 110% before the Ni2+ modified MCM-22 zeolites. The Freundlich adsorption equation could describe the adsorption process well. The thermodynamic parameters △H=-40.67 kJ/mol, △S=-132.37 J/(mol·K), △G< 0. The adsorption process can be simulated by pseudo second-order kinetic equation and Ea was 45.924 kJ/mol.