用脉冲色谱法研究Pd-V_(2)O_(5)体系催化剂的吸附作用

THE CHROMATOGRAPHIC INVESTIGATION ON ADSORPTION OF ETHYLENE ON Pd-V SYSTEM CATALYSTS

本文用脉冲色谱法测定了Pd-V氧化物体系催化剂对乙烯、氧和二氧化碳的吸附作用。指出在接近反应温度下(80—100℃),Pd-V氧化物体系的催化剂对乙烯有可逆与不可逆两种吸附作用,而单独的PdO和V_(2)O_(5)以及载体SiO2则只有可逆吸附作用。测定了不同温度下可逆吸附等温线,计算了吸附热,考查了不可逆吸附与催化剂中Pd含量之间的关系,指出在Pd-V氧化物催化剂上,乙烯的不可逆吸附量与催化氧化活性一样,是与Pd含量有关的。测定了预吸附氧有利于乙烯的不可逆吸附,而CO_(2)则不能牢固的吸附在催化剂表面上。

The adsorption properities of ethlene on Pd-V-Ti-Mo oxide/SiO_(2) and Pd-V oxide/SiO_(2),V_(2)O_(5)/SiO_(2),PdO/SiO_(2),SiO_(2) were investigated by pulse chromatography.On both Pd-V-Ti-Mo oxide/SiO_(2) and pd-V oxide/SiO_(2) catalysts the irreversible adsorption and reversible adsorption of ethylene were measured respectively.The reversible adsorption in our experimental conditions does not play a direct role in oxidation reaction.No irreversible adsorption of ethylene on PdO/SiO_(2),V_(2)O_(5)/SiO_(2) and SiO_(2) was exhibited.However,the irreversible adsorption of ethylene on Pd-V-Ti-Mo oxide/SiO_(2) and Pd-V oxide/SiO_(2) was very obvious.It is also shown that the amount of irreversible adsorbed ethylene on Pd-V-Ti-Mo oxide/SiO_(2) catalyst containing 0.05%Pd and its correlated activity of oxidation were all the highest.So the authors consider that there is a direct relationship between irreversible adsorption and the reactivity of selective oxidation of etylene,and the active centers are,perhaps,caused by Pd-V conbination.The active surface area was calculated and the effect of preadsorbed oxygen on chemisorption of ethylone was examined By-product(CO3)does not make catalysts poisoned.