Wet Chemically Derived Li4sio4 Nanowires As Efficient Co2 Sorbents At Intermediate Temperatures

Lithium silicate based ceramic sorbents are potential materials for CO2 sorption in the temperature range of 500-700 degrees C. However, its sorption performance at temperatures < 500 degrees C is kinetically limited due to the formation of lithium carbonate as a hard surface layer that limits the CO2 diffusion to the reaction interface. This shortcoming in temperature of application has widely impeded its practical application in industrially important reaction environments such as in petrochemical processes. In the present study, we report compositionally tuned lithium silicate nanowires wherein the formation of hard lithium carbonate layer during the sorption process is addressed through the incorporation of low melting eutectics that softens the carbonate layer and facilitates an easier pathway for the diffusion of CO2. This modification is demonstrated to overcome the kinetic limitations of CO2 sorption in lithium silicate at lower temperatures (< 500 degrees C). The nanowire morphology of lithium silicate also facilitated enhanced CO2 capture as the diffusion path-ways for lithium are considerably shorter compared to the conventional micron sized agglomerates. Further, the compositional tuning of lithium silicate nanowires helped to realize an absorption capacity value of 300 mgg(-1) at 450 degrees C, a value seldom achieved for lithium silicate based materials at such low temperatures. The sorption capacity could also be fully regenerated at the same temperature by a pressure swing operation. The results thus pave the possibility of using modified lithium silicate compositions as CO2 sorbents in industrially significant chemical reaction processes such as high temperature water gas shift reaction where the temperatures are generally in the range of 350-450 degrees C.