The possibility of separating hydrogen fluoride from its gaseous mixture with silicon tetrafluoride

Abstract

We report in this paper investigations of the conditions necessary to effect the selective absorption of hydrogen fluoride from its gaseous mixture with silicon tetrafluoride when that mixture is brought into contact with solid sodium fluoride. Thus, when an anhydrous HF-SiF4 gas mixture is brought into contact with granular NaF at room temperature only hydrogen fluoride is absorbed (giving NaF•HF), while silicon tetrafluoride remains in the gaseous state. In this way it is possible to separate HF from SiF4. The hydrogen fluoride may subsequently be regenerated by heating the sodium hydrogen fluoride at 350-400°1. If, however, the gaseous mixture contains only small traces of water vapor then SiF4 also reacts with NaF to give Na2SiF6 in addition to NaF•HF. Under these circumstances it is not possible to effect a separation.