Preparation And Modification Of Activated Carbon From Petroleum Coke And Their CO₂Adsorption Performance

In recent years, high temperature and drought, floods, hail and other weather disasters induced by greenhouse effect occur frequently, therefore, energy-saving, green energy and greenhouse gas emission reduction technologies have gained more and more attention. Among all greenhouse gases that resulting by human activities, CO2has the largest emissions. Therefore, how to reduce the emission of CO2is an important issue that has to be addressed. CO2capture technique is a promising option due to its simple devices, easy operation et al. The major problem is that the cost of adsorbent is still high. The development of low-cost, high quality adsorbent has become one of the important subjects to be solved.In this paper, activated carbon is produced by petroleum coke as precursor materials and KOH as active agent. The experiment summarized the effect of different techniques to produce active carbon (mass ratio, alkali coke mixed mode, granularity of raw materials, different raw materials). This work also adjusted pore structure of the samples, by reactivation with KOH/NaOH, the property of the reactivation sample were investigated by FT-IR and BET and their CO2adsorption properties at room temperature were also investigated. Finally, nitrification-amination treatment was employed to modify the activated carbons. The samples were characterized by N2adsorption/desorption, elemental analysis, FT-IR and XPS. CO2capture properties of samples were investigated by high pressure adsorption instrument.The results show that:The optimum conditions:the100-150μm Hubei coke was employed as carbon source, and KOH as the activating agent, the quality ratio of coke:KOH were3:1; the starting materials were mixed with dry mixing method. The CCl4and CO2adsorption properties of the optimized activated carbon are2252mg/g and15.03mmol/g, respectively.(2)The effect of pore structure on CO2adsorption performance was investigated. KOH (or NaOH) was employed to reactivation the resulting activated carbon obtained in step(1). Experimental results indicated that the surface group of reactivation sample basically unchanged, but the pore size distribution and the mesoporous volume increased, leading to a decrease in the adsorption properties of CCl4and CO2for samples. When the mass ratio of KOH (or NaOH) was1, the CO2adsorption ability was higher than the raw sample in the pressure range of0-4bar. Adsorption ability of reactivation sample on the unit specific surface area were also higher than the raw sample. The samples were recycled10times at ambient conditions found that:adsorption capacity of raw sample decreased slightly faster than the reactivation onesbecause of Its smaller pore size and pore distribution. The effect of surface chemistry character on CO2adsorption performancewas investigated. Nitrification-amination treatment was employed to modifyactivated carbons obtained in step(1). The modified AC samples weresuccessfully introduced basic functional groups such as-NH2on their surface.When treated the sample at the optimum conditions (the volume ratio of acidand water is1, at50℃, for90min) then the adsorption capacities of the samplewere17.72mmol/g and14.01mmol/g at room temperature and319.15K,respectively, which improved by18%and33%compared with the pristinesample. The modified activated carbon was recycled4times at ambientconditions without significant decreases of CO2absorption ability.