Studies on purification of yellow phosphorus off-gas by combined washing, catalytic oxidation, and desulphurization at a pilot scale

The challenges of purification pretreatment process of yellow phosphorous off-gas could limit its application as chemical raw material gas to produce high accessional products. A pilot-scale experiment of the purification process, which included two sub-processes of caustic washing and catalytic oxidation, of yellow phosphorus off-gas was studied in this paper. The results indicated that HF and SO2 can be removed completely by the caustic washing process. In the process of catalytic oxidation purification, the reaction temperature and oxygen concentration of the off-gas were two crucial factors, through which the impurities were selectively oxidized. The concentrations of PH3, H2S, CS2, HF, SO2, and COS were less than 1 mg/m3 in the off-gas of yellow phosphorus after the purification process under oxygen concentration of below 2%. Sulfur and phosphor compounds were oxidized to S and P4O10, respectively, in the catalytic oxidation process and adsorbed on the surface of catalysts. This purified gas was qualified to be used as feedstock in C1 chemistry. Furthermore, the deactivated catalysts were easily regenerated and their catalytic activity can be recovered after several regeneration cycles. This study provided evidence that CO derived from purified industrial off-gas could be used as the raw material of many products.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The impurities can be selectively catalytic oxidized by trace oxygen in the off-gas. ► How to use the trace oxygen for the oxidation of impurities without oxidizing CO was a challenge. ► The P4O10(P2O5) species in the catalyst sample were generated by a catalytic oxidation process.