| Large amount of hydrogen chloride (HCl) is produced as by-productin chemical and pharmaceutical production. If the HCl tail gas is directlydischarged into the atmosphere, it will be not only a waste of the HClresource, but also seriously damage the environment, and even endangerhuman life.At present, the HCl gas is generally treated by a series of muli-levelabsorber columns, using water as absorber, for the production ofhydrochloric acid or high-purity HCl gas. However, there are somedisadvantages for this process, such as the lower economical efficiency,serious corrosiveness and intensive energy requirement for producinghigh purity anhydrous hydrochloride through desorption of thehydrochloride acid due to the presence of water and its higher volatility.Therefore, it is necessary to develop an environmently friendly solventfor HCl absorption, and the solvent is preferential to have high adsorptioncapacity for hydrochloride gas and have negligible volatility. Toward thisaim, the solubility of HCl gas in some ionic liquids (ILs) at differenttemperature and pressure is studied. According to the stability of the ILs’ anion and cation, fourimidazolium based ILs ([mim]Cl,[Bmim]Cl,[Hmim]Cl,[Omim]Cl) andone pyridium based IL ([OPy]Cl) are chose to study the solubility of HClgas. The above ILs are synthesised, and their purities in mole fraction areestimated higher than99%as determined by the NMR analysis.Solubility data of HCl in [mim]Cl,[Bmim]Cl,[Hmim]Cl,[Omim]Cland [OPy]Cl at low pressure in the temperature range of (298.15to363.15) K ware measured for the first time using constant volume method.The results show that the solubility of HCl in theses ILs is higher than inwater, and the mole fraction solubility is above0.5at room temperatureand atmospheric pressure. The solublity of HCl gas in imidazolium basedILs decreases with the increase of alkyl length to the cations of the ILswith the same anion.With respect to the ILs [Omim]Cl and [OPy]Cl with the same alkylsubstitute length, it is found that the solubility of HCl gas in theimidazolium based ILs is lower than in the pyridinium IL. The solubilityof HCl gas in [OPy]Cl and [Bmim]Cl is nearly the same, considering thegood stability of the imidazolium based ILs,[Bmim]Cl is more suitableas the absorbent of hydrochloride tail gases.The solubility data have been correlated satisfactorily by theLangmuir–Herry model, indicating that the Langmuir-Herry model canwell represent the solubility-pressure behaviour of hydrochloride gas in ILs. |
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