Sorbent selection, high temperature

PFE uses standard solvents at elevated temperatures and pressures to increase extraction efficiency. The technique uses standard laboratory solvents that would be used to extract the compound of interest, but PFE techniques use solvent near supercritical temperatures. The high pressure does not allow the solvent to boil, hence increasing its penetration, while the high temperature increases solvent viscosity. Samples are placed in stainless-steel extraction vessels that are loaded into the device, which has been programmed for the extraction protocol. Instruments are available from a variety of manufacturers who allow extraction of either a single or multiple samples. In a variant of the technique, sometimes different solid-phase sorbents are placed in the extraction vessel to allow for a more selective extraction using PFE. 

MEA, have been investigated for their performance as CO2 adsorbents. The synthesis and eharacterization for select polyoximes have been described. The CO2 uptake studies have also been performed at high temperatures (up to 70 C) and high pressures (up to 200 bars) in an attempt to produce high performance solid sorbents for CO2. 

In the search for a sorbent for selective SO2 removal from combustion gases, it was found that styrenic polymeric sorbents had high selectivities for SO2 over CO2 and H2O (Kikkinides and Yang, 1991 Yang 1993). It was also found that the polymeric sorbents had even higher selectivities toward NO than SO2, and these sorbents were extremely hydrophobic. For example, over 100 mg/g of NO was chemisorbed at room temperature from a simulated flue gas. The chemisorbed NO... 

The optimum conditions needed to achieve the desired sulfur capture efficiency (90 percent) is dependent on sorbent type, coal type, and fluidized bed design. Representative conditions are a bed temperature of 1116 K, a sorbent particle of 1 mm, and a Ca/S ratio of about 3. The bed temperature selection is based on the admittedly shaky evidence that this is where the maximum sulfation peaks. The particle size selection is a compromise between a desire to use high gas velocities and the observed decrease in sulfation with increasing size (Figure 2). The Ca/S ratio corresponds to a maximum sulfation of about 0.3. For these conditions the mass feed rate of a limestone sorbent is 0.345 that of the coal feed and the flow rate of the partially sulfated spent sorbent is 0.285 the coal feed rate. 

---