Copper(I) chloride-pyridine complex supported on silica gel as adsorbent for carbon monoxide

A copper(I) chloride-pyridine complex supported on silica gel was prepared by mixing porous silica gel beads with an acetonitrile solution containing the complex composed of copper(I) chloride (CuCl) and pyridine under nitrogen, followed by removal of liquid phase under reduced pressure. The resulting silica gel, 5.8 g, contained 4.39 mmol of CuCl and 4.08 mmol of pyridine. It rapidly adsorbed carbon monoxide (CO) at 30 degrees C under 1.0 atm of CO, and the equilibrium amount of adsorbed CO was 3.29 mmol (80.6% against containing pyridine). The adsorbed CO was rapidly desorbed by maintaining it at 70 degrees C under 1.0 atm or at 30 degrees C under 0.4 mmHg. The adsorption-desorption cycle was repeated without any deterioration. The equilibrium amount of adsorbed CO (3.29 mmol) was 5.5 times that of adsorbed carbon dioxide (0.60 mmol), and 36.6 times that of adsorbed methane (0.09 mmol) at 30 degrees C under 1.0 atm. The reversible and selective adsorption of CO was attributed to formation of molar ratio 1 : 1 : 1 CuCl-pyridine-CO complex from CO molecule and molar ratio 1 : 1 CuCl-pyridine complex supported on silica gel. When the adsorbent contacted with oxygen, the CO adsorbing ability decreased. The adsorbing ability was completely recovered by maintaining the adsorbent at 120 degrees C under 1.0 atm of hydrogen for 48 h.