二甲基二硫醚对Pt/Al_2O_3催化丙烷脱氢反应性能的影响

Effects of dimethyl disulfide on catalytic performance of propane dehydrogenation over Pt/Al_2O_3

制备了Pt/θ-Al_2O_3催化剂,在该催化剂上进行丙烷脱氢反应过程中引入不同用量的二甲基二硫醚(DMDS),考察了DMDS对Pt/θ-Al_2O_3催化剂性能的影响。实验结果表明,在一定浓度范围内,在丙烷脱氢反应中引入DMDS可大幅提高Pt/θ-Al_2O_3催化剂的丙烯选择性及稳定性,同时降低结焦速率和结焦的石墨化程度,但催化剂活性有所降低。采用HRTEM、XPS、TG和拉曼光谱等方法对催化剂结构和结焦性质进行了分析。表征结果显示,丙烯选择性以及稳定性的提高主要是由于DMDS在Pt表面解离生成的含硫物种吸附于Pt表面,使Pt处于富电子状态,促进了丙烯的脱附并抑制了深度脱氢反应;但同时也提高了C—H键断裂难度,导致催化剂活性有所降低。

Pt/θ-Al2O3 catalyst was prepared,and the effects of dimethyl disulfide(DMDS) on the Pt/θ-Al2O3 catalyst were evaluated in propane dehydrogenation with different concentrations of DMDS in the feed. The results reveal that the addition of DMDS with a desired concentration can significantly improve the propylene selectivity and catalyst stability. Meanwhile,the coking rate and the degree of graphitization are reduced at the expense of a slight activity loss. The HRTEM,XPS, TG and Raman spectroscopy were used to analyze the structure of the catalyst and coking properties. The characterization results indicate that the improvement of propylene selectivity and catalyst stability is mainly due to the fact that sulfur-containing species generated by dissociation of DMDS on the surface of Pt are adsorbed on the surface of Pt,so that Pt is in an electron-rich state,desorption of propylene is promoted,and deep dehydrogenation reaction is inhibited. However,the difficulty of C-H bond breaking is also increased,resulting in inhibition of catalyst activity.