Sorbent for Sorption-Enhanced Reforming

In SERF, CO2 is adsorbed over a solid sorbent while SMR and WGS reactions occur. 

Another type of sorbent is based on hydrotalcite, which shows good cyclic stability, even if lower than competitive sorbents, and fast sorption kinetics. On the other hand, CO2 sorption on hydrotalcite has a low heat of reaction, making it necessary to sustain the endothermic reforming reaction by an external source of heat or the application of an autothermal system. In addition, these materials are suitable for operations at 400-450 °C where methane conversion is rather low. For these reasons, hydrotalcites are more promising for the sorption-enhanced water-gas shift concept, which is described in the following section. 

A promising sorbent for SER applications is calcium oxide (as pure CaO or dolomite), which can react with CO2 generating CaC03 according to the following carbonation reaction (6.3)  

Equation (6.4), reported in Ref. [11], is an example equation expressing the equilibrium CO2 partial pressure with temperature. 

The overall calcium-based SER reaction, which results from the single carbonation (Eq. (6.3)), reforming and water-gas shift reactions is reported in Eq. (6.5)  

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