摘要
Noble metal-based-bimetallic catalysts have been highly investigated and applied in wide applications including biomass transformation via regioselective C−O hydrogenolysis while further modification especially with noble metal is highly promising yet still under investigation.Herein,Ru was found as an effective modifier among the screened noble metals(Ru,Pt,Rh,Pd,Au,and Ag)for Ir-Fe/BN(Ir=5 wt%,Fe/Ir=0.25)catalyst in terminal C−O hydrogenolysis of 1,2-butanediol(1,2-BuD)to 2-butanol(2-BuOH).Only trace amount of Ru(up to 0.5 wt%)was effective in terms of high 2-BuOH selectivity(>60%)and activity(about twice).Larger amount of Ru species(3 wt%)highly enhanced the activity but gave low selectivity to 2-BuOH with by-products of terminal C−C bond scission.Optimized catalyst(Ru(0.5)-Ir-Fe/BN)was reusable at least 4 times and gave moderate 2-BuOH yield(47%)in hydrogenolysis of 1,2-BuD.The promoting effect of Ru addition(0.5 wt%)to Ir-Fe/BN on hydrogenolysis of various alcohols was also confirmed.Combining catalytic tests with various characterizations,the promotion mechanism of Ru species in trimetallic catalysts was clarified.The Ru species in Ru(0.5)-Ir-Fe/BN form alloy with Ir and are enriched at the interface with BN surface,and direct interaction between Ru and Fe was not necessary in Ru-Ir-Fe alloy.The interface of Ir and Fe on the surface of Ir-Fe alloy may work as active sites for 1,2-diols to secondary alcohols via direct C−O hydrogenolysis,in which Ru-modified Ir activates H_(2) to form hydride-like species.The activity of Ru species in C−C bond cleavage was highly suppressed due to the direct interaction with Ir species and less exposed to substrate.Larger loading amount of Ru species(3 wt%)led to the formation Ru-rich trimetallic alloy,which further works as active sites for C−C bond scission.
贵金属基双金属催化剂已被系统研究并广泛应用于区域选择性C-O键氢解进行生物质转化等领域,而进一步采用贵金属改性非常有应用前景,函待深入研究。本文发现,在所筛选的贵金属(Ru,Pt,Rh,Pd,Au和Ag)中,Ru是1,2-丁二醇(1,2-BuD)末端C-O氢解为2-丁醇(2-BuOH)的Ir-Fe/BN(Ir=5wt%,Fe/Ir=0.25)催化剂的有效改性剂.微量的Ru(0.5wt%)改性后,即可高选择性获得2-BuOH(>60%),活性提升约1倍,提升Ru负载量(3wt%)可继续提高活性,但2-BuOH选择性较低,并产生了末端C-C键断裂的副产物.最优催化剂(Ru(0.5)-Ir-Fe/BN)可重复在1,2-BuD氢解反应中使用至少4次,2-BuOH收率适中(47%).结果还表明,添加0.5wt%的Ru促进了Ir-Fe/BN上各种醇的氢解反应结合催化反应和表征结果,研究了Ru物种在三金属催化剂中的促进机理。Ru(0.5)-Ir-Fe/BN中Ru物种与Ir形成合金,并在与BN表面的界面上富集,在Ru-Ir-Fe合金中Ru和Fe之间不需要直接相互作用.Ir-Fe合金表面的Ir-Fe界面可能是1,2-二醇通过直接C-O氢解制备仲醇的活性位点,其中Ru改性的Ir活化H_(2)形成氢化物类物质.由于与Ir物种的直接相互作用和较少暴露于底物,大大抑制了Ru物种断裂C-C键的活性.Ru负载量较高时(3wt%)导致形成富Ru三金属合金,该合金进一步充当C-C键断裂的活性位.
