论文部分内容阅读
用质谱检测的程序升温脱附研究了~(13)CH_3OH在不同La_2O_3含量的Pd-La_2O_3/SiO_2催化剂上的脱附和分解。高温He处理的催化剂室温下对甲醇的吸附容量随La_2O_3含量增加而增加,但其脱附和分解产物之比几乎为常数。氢还原的催化剂室温下对甲醇吸附容量在Pd/La体相原子比为1:1时达最大值,但甲醇脱附和分解产物之比值随La_2O_3含量增加而增加,且产物中CO_2随La_2O_3含量增加而减少。CH_3OH和~(13)CH_3OH次序吸附后的TPD谱表明在催化剂上有对甲醇的分子吸附中心,可置换的解离吸附中心和不可置换的强解离吸附中心。CO和~(13)CH_3OH共吸附的TPD谱表明:在CO和~(13)CH_3OH共吸附物类之间有相互排斥的作用。这种作用有利于CO吸附态的重新分布和脱附,因此阻止了CO的岐化反应。
The desorption of ~ (13) CH_3OH on Pd-La_2O_3 / SiO_2 catalysts with different La_2O_3 contents was investigated by mass spectrometry. The adsorption capacity of methanol at room temperature increased with the increase of La 2 O 3 content but the ratio of desorption and decomposition products was almost constant. The catalyst for hydrogen reduction has a maximum methanol adsorption capacity at 1: 1 atomic ratio of Pd / La at room temperature, but the ratio of methanol desorption and decomposition products increases with the increase of La 2 O 3 content, and the content of CO 2 in the product increases with La 2 O 3 content And reduce. The TPD spectra of sequential adsorption of CH_3OH and ~ (13) CH_3OH showed that there was a molecular adsorption center, a displaceable dissociative adsorption center and a non-displaceable strong dissociative adsorption center on the catalyst. The TPD spectra of CO and ~ (13) CH_3OH co-adsorption show that there is a mutual repulsion between CO and ~ (13) CH_3OH co-adsorbates. This effect favors the redistribution and desorption of CO-adsorbed states, thus preventing the CO disproportionation reaction.