Commercial MoS2 was found to be a highly selective catalyst for the reduction of nitrobenzenes to the corre- sponding anilines with hydrazine under mild conditions. MoS2 is not only much cheaper, but also more selecti...Commercial MoS2 was found to be a highly selective catalyst for the reduction of nitrobenzenes to the corre- sponding anilines with hydrazine under mild conditions. MoS2 is not only much cheaper, but also more selective than noble metal catalysts for the reduction of functional nitrobenzenes to the corresponding anilines. Nitrobenzenes with halides （F, C1, Br and I） were reduced selectively, and the corresponding anilines were obtained in excellent yields, and no dehalogenation was detected. Functional groups such as NH2, OH, alkene groups were tolerated dur- ing the reduction of the nitro compounds. The reduction ofp-chloronitrobenzene was studied over MoS2 and Pd/C respectively with hydrazine. The yield ofp-chloroaniline was much higher with MoS2 than that with Pd/C at full conversion.展开更多
文摘Commercial MoS2 was found to be a highly selective catalyst for the reduction of nitrobenzenes to the corre- sponding anilines with hydrazine under mild conditions. MoS2 is not only much cheaper, but also more selective than noble metal catalysts for the reduction of functional nitrobenzenes to the corresponding anilines. Nitrobenzenes with halides （F, C1, Br and I） were reduced selectively, and the corresponding anilines were obtained in excellent yields, and no dehalogenation was detected. Functional groups such as NH2, OH, alkene groups were tolerated dur- ing the reduction of the nitro compounds. The reduction ofp-chloronitrobenzene was studied over MoS2 and Pd/C respectively with hydrazine. The yield ofp-chloroaniline was much higher with MoS2 than that with Pd/C at full conversion.
基金supported by the Ministry of Science and Technology(MOST,2016YFA0204100 and 2011CBA00504)the National Natural Science Foundation of China(21573254,91545110)+1 种基金the Youth Innovation Promotion Association(CAS)the Sinopec China~~
文摘MoS_2具有独特的二维层状结构,被广泛用于加氢脱硫过程以及HER反应,而且可以通过减少MoS_2的颗粒尺寸以及层数来进一步改善其催化活性.通过剥离方法得到的MoS_2纳米片虽然表现出优良的加氢脱硫活性,但容易团聚使其循环使用性能很差.如果通过引入纳米碳将单层的MoS_2纳米片进行有效'隔离',则可明显降低团聚的可能性,从而改善其催化性能和稳定性.本文通过一步水热法制备出了碳嵌入的MoS_2纳米颗粒(MoS_2@C),将其应用于硝基苯类化合物的氢转移反应中表现出了非常好的催化性能.进一步通过粉末X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和在线质谱检测等手段研究了层间距增加的MoS_2催化剂在硝基苯类化合物的氢转移反应中催化性能提升的原因.XRD,SEM和TEM结果表明,通过引入碳材料可以明显增加MoS_2的层间距,同时减小其颗粒尺寸,而且使MoS_2表现出弯曲的(002)晶面.由于存在一定的曲率,这种(002)晶面也会表现出一定的催化能力.氮气物理吸附结果表明,这种MoS_2@C复合物具有较高的比表面积(89 m^2g^(-1))和明显的介孔结构(~20 nm),在催化反应中有利于底物扩散,进而改善催化性能.XPS结果显示,与体相的MoS_2相比,MoS_2@C表面暴露出更多的不饱和Mo原子(Mo/S=0.71(MoS_2@C)vs Mo/S=0.63(MoS_2)),形成了独特的S-Mo-O结构以及缺陷结构.在硝基苯类化合物的氢转移反应中,层间距增加的MoS_2@C由于暴露出更多的活性位和具有弯曲的(002)晶面,表现出了更高的催化活性–(TOF=3.66 s^(-1) vs 1.24 s^(-1)(MoS_2)).通过质谱对反应过程的追踪发现,在只有肼存在的条件下,MoS_2@C催化肼分解的主要气相产物是氨气.这说明MoS_2@C能够使肼发生N-N键的断裂.而当肼和硝基苯同时存在的条件下,质谱检测的气相产物主要是氮气,表明硝基苯的存在可以诱导肼逐步发生N-H键断裂,在催化剂表面形成活性的H物种,进而转移到硝基苯上使其还原得到苯胺.使用偶氮苯和氧化偶氮苯作为反应底物,发现MoS_2@C很难使其还原为苯胺,这说明在该催化体系中,硝基苯的还原过程主要是沿着直接路径(硝基苯-亚硝基苯-苯胺)进行的.
