傅里哀变换红外发射光谱法研究金属氧化物催化剂 I. 实验建立及氧化钼的还原-氧化研究

本文报导了傅里哀变换红外发射光谱法研究多相氧化物催化剂的实验装置的建立及实验条件的考察。设计加工了一个温度范围宽, 可在各种气氛和真空条件下原位研究氧化物催化剂的红外发射池。以MoO_3为例, 考察了样品厚度, 测试温度对发射光谱的影响。当样品量小于1 mm·cm~(-2)时, 随样品量增加, 谱峰强度线性增加, 但峰形不发生变化。当样品量高于1 mg·cm~(-2)时, 随样品量增加, 谱图严重畸变。随样品温度升高,谱峰强度近似线性增加。并用该方法研究了MoO_3在还原和再氧化过程中表面氧物种的变化。结果表明桥式MO—O—Mo物种比端基Mo=O物种较易还原, 再氧化时, Mo=O物种比Mo—O—Mo物种优先形成。

FT-IR Emission Spectroscopic Studies of Metal Oxide Catalysyts I. Experimental Respects and Reduction-reoxidation of Molybdenum Trioxide

Fourier-transform infrared(FT-IR) emission spectroscopic technique has been establi-shed to study metal oxide catalysts. An in situ infrared emission cell was specially de-signed to treat sample in vacuo or in various gases at a wide temperature range (r.t. -700 ℃). Infrared emission spectrum of MoO_3 was presented and the results demons-trated that FT-IR emission spectroscopy is a sensitive method to detect vibrational information of metal oxide catalysts.The experimental conditions including sample preparation, effects of temperature and sample thickness on the infrared emission spectrum were detailed. It was found that the spectrum was severely disordered when the sample thickness of MoO_3 was beyond 1.00 mg·cm~2 and the more intensive emission bands were detected at higher temperatures. Infrared emission spectra recorded in the course of H~2 reduction of MoO_3 showed that surface linkage Mo—O—Mo species giving the band at 880 cm~(-1) is more easily reduced comparing to the terminal Mo=O species giving the band at 990 cm~(-1), vice versa, the Mo=O species are preferentially formed than the Mo—O—Mo species during the reoxidation of the partially reduced MoO_3.