Preparation And Preformance Of Activated Carbon-based La And Mn Desulfurization Adsorbents

Deep desulfurization of oil products is a hot and difficult point in petrochemical industry.Compared with other desulfurization technologies,adsorption desulfurization technology has the advantages of less investment and good selectivity.In this paper,commercial coconut shell activated carbon with rich pore structure was used as carriers.La（III）/AC and Mn（II）/AC were prepared by ultrasound assisted impregnation method.The performance of removal DBT with two adsorbents was evaluated by static and dynamic adsorption experiments.Adsorption isotherms,kinetics and thermodynamics of adsorption process were studied.The main conclusions are as follows:（1）The optimal calcination temperature and loading amount with La modified activated carbon were 803 K and 2 wt%,respectively.The active metal on the surface of activated carbon was La（III）.The adsorption capacity reached 0.60 mmol g^-1(sulfur in the initial concentration:300 mg L^-1,5 g L^-1).The optimal loading amount with Mn modified activated carbon was 2 wt%,respectively.The active metal on the surface of activated carbon was Mn（II）.The adsorption capacity reached 0.53 mmol g^-1(sulfur in the initial concentration:300mg L^-1:5 g L^-1).（2）By contrast experiment,adsorption mechanism with La（III）/AC and Mn（II）/AC wereπ-πcomplexation.The adsorption capacity with La（III）/AC and Mn（II）/AC held the level of 88%comparison with that of fresh adsorbents after using 4 times in total.Dynamic adsorption tests showed that La（III）/AC had the best adsorption capacity and selectivity under the same experimental conditions;Real gasoline dynamic adsorption experiment over La（III）/AC,the results showed that La（III）/AC could obtain zero sulfur gasoline in initial stage,and gasoline color become clear and transparent.（3）Langmuir and Freundlich isothermal equations were used to fit the experimental data.Coefficient of determination（R²）and root mean square error（RMSE）were used to estimate the goodness of fit.The results showed that Freundlich model could fit the experimental data better and the surface with activated carbon by active metal modified was heterogeneous.（4）Kinetic studies indicated that MPnO model could fit the experimental data better;the reaction order of La/AC and Mn/AC was 2.2 and 1.7,respectively.Parameter sensitivity analysis showed that three adjusted parameters-MPnO model could not get the uncorrelated and accurate parameters by fitting experimental data,which were over-parameters.Two parameters-MPnO model was obtained by modification,which indicated that uncorrelated and accurate parameters could be got by fitting experimental data,and the goodness of fit was not inferior to that of three parameters-MPnO model.（5）Thermodynamic analysis indicated that adsorption enthalpy and entropy changes with La/AC and Mn/AC were less than 0,indicating that the adsorption process was exothermic process and a decrease in the degree of freedom with the adsorbed species.Gibbs free energy with La/AC and Mn/AC were less than 0,which showed that the adsorption process was a spontaneous process.