| SOx is the culprit of acid rain, which is caused by combustion emissions of sulfur compounds from the fuel oil. Acid rain brings great harm to crops and buildings. Traditionally, hydrodesulfurization (HDS) was selected as the main desulfurization method. While, hydrodesulfurization will cause the loss of octane number, H2 consumption, high operation conditions of pressure and temperature. Compared with HDS, adsorption desulfurization has the advantages of mild operating conditions, low energy consumption, no loss of octane number and good selectivity for thiophene and its derivatives.Active carbons (ACs) have rich pore structure, good adsorption performance and availability, having attracted extensive attention of researchers; but the problems of small adsorption capacity and slow adsorption rate existed. Two kinds of commercial AC, marked as AC1(Tianjin), AC2(ChangGe, Henan) respectively,were selected for adsorption desulfurization. The modification of adsorbent based carbon was prepared, and desulfurization performance of the modified AC was evaluated. The main contents and conclusions were as follows:(1) Static adsorption was carried out firstly. The results showed that desulfurization performance of AC2 was better than that of AC1. The best adsorption temperature of AC1 and AC2 were 35℃ and 45℃ respectively.(2) Through orthogonal experiment, the effect of calcining temperature, processing time and concentrations of nitric acid on AC desulfurization performance were investigated. Results showed that AC2, which was treated with 30% nitric acid under 25℃ for 4h, had good desulfurization performance, and the desulfurization rate was 72% with initial sulfur content 31.25 mmol/L. Compared with the untreated AC2, sulfur adsorption capacity changed from 0.3 mmol/g to 0.45 mmol/g after nitric acid oxidation, and desulfurization rate was increased to about 1.5 times.(3) Impregnation and ultrasonic method were applied to prepare the adsorbents of Ni/AC, Co/AC, Cu/AC. Operation conditions of calcining temperature, metal load effect on the properties of desulphurization were examined through static adsorption experiments. Results showed that the best calcining temperature of adsorbents was 400℃, and for the three kinds of adsorbent metal ions, the best load were 4%,3% and 1% respectively. Desulfurization rate on Ni/AC, Cu/AC, Co/AC were 82%,84% and 85% respectively.(4) Adsorption isotherms were fitted by means of Langmuir and Freundlich models. Results showed that adsorption processes of three adsorbents for DBT were in accordance with Langmuir model and Freundlich model. The biggest adsorption sulfur capacity reached about 0.98mmol/g after modification of AC. Kinetics analysis showed that adsorption process of DBT on AC conformed to line with quasi secondary dynamics model. Thermodynamic analysis showed that adsorption process is a spontaneous process and endothermic among the temperature range studied.(5) Dynamic adsorption results showed that adsorption temperature was also 45℃. Breakthrough time increased with the increasing of bed height, but it decreased with the increasing of initial concentration. Relationship between breakthrough time and fixed bed height was fitted through Yoon-Nelson model. |
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