Abstract
In this present study, the nanocrystalline ZrO 2 particles synthesized by the solvothermal method were calcined in reductive (H 2), inert (N 2) and oxidative (O 2 and air) atmospheres prior to impregnation with tungsten (W) in order to produce the W/ZrO 2 (WZ) catalysts. Based on the ESR measurement, it revealed that only the ZrO 2 samples calcined in H 2 and N 2 exhibited the F-center (single charged oxygen vacancy) at g = 2.003. None of Zr 3+ defect was detected for all calcined ZrO 2 samples. After impregnation with tungsten, the WZ catalysts were also characterized. It was present as the polycrystal, which can be seen by the selected area electron distribution (SAED). However, the presence of Zr 3+ defect was evident in all WZ catalysts, while the F-center was absent. The highest Zr 3+ intensity detected in the WZ catalyst using ZrO 2 under H 2 calcination atmosphere can be attributed to the transformation of F-center to Zr 3+ defect. It revealed that the WZ-H 2 catalyst exhibited the highest conversion under transesterification of triacetin and methanol among other WZ catalysts. This can be attributed to the high surface acidity, which was probably induced by large amounts of Zr 3+ defect.
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