有序介孔Sn-SBA-15负载铂催化剂上丙烷脱氢性能的提高（英文）

丙烷脱氢制丙烯能够将低级烷烃转变成烯烃,是有效扩大丙烯来源的生产工艺.铂锡催化剂用于丙烷催化脱氢的主要缺点是稳定性差、选择性低,通过稳定锡的氧化态可以大大改善催化剂的脱氢性能及稳定性.本文采用一锅水热合成法制备了一系列高比表面积具有高度有序介孔结构的Sn掺杂的Sn-SBA-15材料,并作为载体负载铂催化剂用于丙烷脱氢反应.同时利用传统浸溃法(IM)合成了Sn/SBA-15-IM材料作为对比.结合X射线衍射(XRD)、BET比表面积和孔体积测试、红外光谱(FT-IR)、X射线光电子能谱、H_2程序升温脱附(H_2-TPD)、热重分析(TGA)、扫描电镜和透射电镜等多种物理化学表征手段研究了Sn-SBA-15材料和催化剂的结构性质及其丙烷脱氢反应性能.XRD和BET比表面积和孔体积测试结果表明,水热合成法原位引入助剂Sn不影响载体SBA-15的有序孔道结构,同时能够保持较大的比表面积.传统浸溃法引入Sn会堵塞载体孔道,载体比表面积及孔道有序度下降.Sn掺杂进入SBA-15骨架能够增强Sn物种与载体的相互作用,有利于Sn物种在反应过程中保持氧化态,提高催化剂丙烷脱氢反应的活性及选择性.当Sn掺杂量增至2.0 wt%时,Pt,Sn组分与载体之间的相互作用减弱,催化剂中Sn^0物种所占比例增多,导致催化剂丙烷脱氢性能下降.在丙烷脱氢反应过程中,一锅法引入Sn的催化剂上反应活性和稳定性明显优于浸溃法引入Sn的催化剂.其中,Pt/0.5Sn-SBA-15催化剂表现出最优的丙烷脱氢性能,丙烷转化率为43.8%,丙烯选择性为98.5%.

Improvement of catalytic stability for CO_2 reforming of methane by copper promoted Ni-based catalyst derived from layered-double hydroxides

Copper-promoted nickel-based metal nanoparticles (NPs) with high dispersion and good thermal stability were derived from layered-double hydroxides (LDHs) precursors that were facilely developed by a co-precipitation strategy. The copper-promoted Ni-based metal NPs catalysts were investigated for methane reforming with carbon dioxide to hydrogen and syngas. A series of characterization techniques including XRD, N2adsorption and desorption, H2-TPR, XPS, CO2-TPD, TEM, TGA and in situ CH4-TPSR were utilized to determine the structure-function relationship for the obtained catalysts. The copper addition accelerated the catalyst reducibility as well as the methane activation, and made the Ni species form smaller NPs during both preparation and reaction by restricting the aggregation. However, with higher copper loading, the derived catalysts were less active during methane reforming with CO2to syngas. It was confirmed that the catalyst with 1 wt% Cu additive gave the higher catalytic activity and remained stable during long time reaction with excellent resistance to coking and to sintering. Furthermore, the mean size of metal NPs changed minimally from 6.6 to 7.9 nm even after 80 h of time on stream at temperature as high as 700 °C for this optimized catalyst. Therefore, this high dispersed anti-coking copper-promoted nickel catalyst derived from LDHs precursor could be prospective catalyst candidate for the efficient heterogeneous catalysis of sustainable CO2conversion. © 2016 Science Press