Study On Preparation Of Activated Carbon From Deoiled Asphalt

Solvent Deasphlating Technology has been widely applied in heavy oil processing.Using the by-product deoiled asphalt reasonably can not only benefit the petroleum enterprise economy but also improve the environment protection. Studying on preparation of activated carbon from deoiled asphalt can enhance the value of oil products and also open up a new resource of carbon materials. It can also enrich and develop carbon science.The deoiled asphalt from CNOOC was firstly pretreated through a retorting process, which is determined the optimum conditions. Then the products of pretreated deoiled asphalt were studied via using steam-heating furnace and steam-microwave methods. The feasibility of nitric acid and ferric nitric impregnation used before the steam activation process was explored. The alkali activating methods to prepare high surface area activated carbon was also employed.The benzene adsorption, iodine adsorption and BET specific surface were used to characterize activated carbon adsorption properties. Discussion of the factors affecting the different processes was carried out and the optimum conditions of preparing deoiled asphalt activated carbon were selected.In this paper, deoiled asphalt would be heated to 450℃keeping out the air in the autoclave, then the solid product from the retorting pretreatment process would be used as raw material for the next activation process. The optimum retorting conditions were as follows: heating rate was 2.86℃/min, the constant time was 2h.The retorting process had an obvious effect on product, and the iodine adsorption reached 600mg/g. The steam-microwave method can obtain higher surface area and microporosity than steam-heating furnace method. Under the conditions of steam current capacity 9ml/min, microwave power 1400W, activation time 20min, the surface area can up to 963.73 m2/g.The surface area of product by nitric acid impregnation became greater with impregnation temperature increasing, and firstly became greater then lower with the impregnation time longer. Under the conditions of impregnation temperature 100℃, impregnation time 12h. The surface area can up to 1280.68 m2/g; The surface area of product by ferric nitric impregnation firstly became greater with impregnation concentration increasing, then stayed the level. Under the conditions of impregnation concentration 15%, carbonization temperature 450℃, carbonization time 1h, the surface area can up to 1223.40 m2/g.Taking KOH and NaOH as active agent respectively, the optimum preparation process conditions using heating furnace were as follows: the ratio of active agent to deoiled asphalt was 4:1, carbonization temperature was 700℃, activation temperature was 850℃,activation time was 2h.The results show that the effect of KOH activation is much better than that of NaOH activation. The product surface area of KOH activation is 2231.56 m2/g, microporosity is 93.9%; the product surface area of NaOH activation is 1285.76 m2/g, microporosity is 89.2%.Using the deoiled asphalt as raw material, the product surface area sequence is KOH activation> NaOH activation> steam-nitric acid impregnation> steam-ferric nitric impregnation> steam-microwave > steam-heating furnace.The microporosity of products with microwave method is even higher ,and microwave method has the adventures of saving time and conserving energy.Using nitric acid and ferric nitric impregnation to improve the microwave process,can obtain the medium activated carbon which the surface area exceeds 1000 m2/g.