Phosphates and Hydrogeno-Phosphates as Materials for Catalysts and Humidity Sensors
2004 年 15 巻 p. 100-109
詳細
2004 年 15 巻 p. 100-109
Phosphates as surface-functional materials were investigated. Boron phosphate (BPO4), which is known to be a solid acid catalyst, showed prominent activity for the oligomerization of light olefins giving a liquid fuel, although other phosphates were inactive. Its activity was enhanced by grinding before use or by adopting a new preparation method characterized by supercritical drying As a catalyst support, AlPO4 was examined for selective catalytic reduction of NO in exhaust gas to N2 by hydrocarbon in the presence of excess oxygen. It was found that the activity of Pt(0.5wt%)/AlPO4 catalyst was higher than that of conventional Pt(0.5wt%)/Al2O3 catalyst, although AlPO4 alone was hardly inactive. Next, metal phosphates were examined as humidity-sensing materials, and several new candidates including Ti(HPO4)2·?H2O were found. The humidity-sensing characteristics of Ti(HPO4)2·H2O was considerably improved by treating with a NaOH solution. In addition, we found that Cu-P-Y-O ceramics, which were produced by the solidstate reaction between Cu3(PO4)2·3H2O and Y2O3, showed good humidity-sensitive characteristics; its electric resistance decreased by three orders in magnitude as the surrounding relative humidity increased from 0% to 96%.
