| Greenhouse effect caused by Carbon dioxide(CO2) emissions has attracted global concern. It is emergent to reduce the emissions or make good use of it.However,CO2 separation and purification from the carbon sources prevent the process.C6H6 has been recognized as one of human carcinogens,hence it is necessary to rmove it completely when producing food-grade CO2.The purpose of this study is to develop efficient adsorbents for C6H6 removal from CO2 stream.The abilities of dfferent types of adsorbents have been investigated according the content of adsorption capacity of adsorbent.Results showed that activated carbon as the best adsorbent has the highest adsorption capacity for the removal of trace amount C6H6 from CO2 because of its special graphite structure,high surface area and micropore volume.The effect of the gas flow rate,adsorbent particle size and pre-treatment on the adsorption breakthrough curve,adsorption capacity,LUB(equivalent length of unused bed) and Q(utilization rate of bed) were investigated.Activated carbon was modified with three methods:oxidizing modification,deoxidizing modification and metal ions modification.Adsorption performances of all kinds of modified activated carbons were evaluated.Some factors which may affect the adsorption capacity, such as the kinds of oxidants,the concentration of oxidant,deoxidization temperature and deoxidization time were also investigated in the fixed-bed reactor.Results showed that deoxidizing modification can improve the adsorption capacity of activated carbon.The activated carbon modified by N2 for 3 h at 300℃has the best capacity.Oxidizing modification and metal ions modification make against the improvement for C6H6 removal from CO2.Removing C6H6 from CO2 with activated carbon depends on its special graphite structure,high specific area,microporous volume and nonpolar surface.The adsorbent for deep removal of C6H6 from CO2 is dependent on not only its large adsorption capacity but also its strong bonding with C6H6.NaY zeolite was investigated in the fixed-bed reactor.TPD and TG results showed that NaY and AgNaY were good adsorbents with high adsorption capacity and strong bonding force with C6H6.Ag+ supported on the NaY forms a new adsorption bond ofπ-complexation,which can improve the adsorption capacity. Effects of regeneration temperature,regeneration time and regeneration ability on adsorption performance were investigated.Activated carbon has effective adsorption performance after repetitious heating regeneration for 180 min with the blow gas of N2 or CO2.Activated carbon and NaY can be regenerated at 150℃and 250℃respectively. |
