The potential mechanism of potassium promoting effect in the removal of COS over K/NiAlO mixed oxides

The removal of carbonyl sulfide (COS) on potassium promoted NiAl hydrotalcite-derived oxides (HTO) has been investigated. The adsorbents were characterized by using techniques of XRD, SEM, XPS, FTIR, CO2-TPD and N-2 adsorption/desorption. A dramatic improvement of the activity can be observed when the NiAl HTO is modified with KOH and K2CO3. However, KCl and KNO3 loading can lead to a decrease in desulfurization efficiency. K2CO3 is decomposed on the surface of the carrier to form K2O. The low temperature activity is enhanced due to the electron donating effect of potassium. KOH loading can not only increase the number of hydroxyl groups on the surface of the carrier, but also raise the Lewis base of Ni atoms. On the one hand, the KCl and KNO3 can enhance the Lewis basicity of the Ni atom; however, because of the domination of the Ni atoms by Cl- and NO3-, the reduction of the moderate intensity base is noted.