C包覆Ni磁性载体负载Pt催化硝基苯加氢性能

Hydrogenation of Nitrobenzene Catalyzed by Pt Supportedon Carbon Coated Nickel Magnetic Supports

苯胺是一种重要的基础化工原料,在医药、染料、橡胶等领域被广泛应用。以硝基苯为原料通过液相催化加氢制备苯胺是目前主要工业生产方法之一,然而,如何从液相加氢反应体系中将催化剂高效分离和回收仍然是该领域的一个重要挑战。本工作开发了一种具有磁可分的C包覆Ni磁性载体负载Pt金属催化剂,用于高效催化硝基苯加氢制苯胺。以乙二胺四乙酸和Ni(OH)_(2)为原料成功合成了N掺杂石墨烯包覆Ni纳米颗粒磁性载体(Ni@NG),采用沉积-沉淀法制备Ni@NG负载Pt金属催化剂(Pt/Ni@NG),通过Raman光谱、TEM、XRD和XPS对制备的Pt/Ni@NG催化剂进行结构表征。结果表明,这种Ni@NG载体具有典型的核壳结构(纳米Ni颗粒为核,石墨烯为壳层)。XPS结果表明Ni@NG载体表面N掺杂石墨烯壳含有3.64%N (原子分数)。当Pt负载量(质量分数)从0.1%增加到0.5%时,Pt在石墨烯壳层表面的分散状态经历了单原子、团簇、颗粒的转变过程。当Pt负载量为0.3%时,以Pt团簇形式分散为主的Pt/Ni@NG催化硝基苯加氢显示出最高的活性,在反应压力为1 MPa和反应温度为30℃时,硝基苯加氢的周转频率为27239.2 h^(-1),硝基苯在60 min内完全转化为苯胺。此外,由于Pt/Ni@NG催化剂具有优异的液相磁可分性能,催化剂经5 cyc使用后加氢活性未明显降低。

Aniline is an important chemical raw material widely used in various industries,including medicine,dye manufacturing,and rubber production.Catalytic liquid-phase dhydrogenation of nitrobenzene is a main industrial production method for aniline.However,the separation and recovery of the catalyst from the liquid hydrogenation system remain challenging.Graphene-encapsulated transition-metal nanoparticles(TM@G,where TM=Fe,Co,and Ni)exhibit magnetic separability and electron transfer effects,making them widely applicable in heterogeneous catalysis.In this study,a magnetically separable catalyst support,comprising graphene-encapsulated Ni nanoparticles(Ni@NG),was developed.This support was then loaded with a Pt metal catalyst for efficient catalytic hydrogenation of nitrobenzene to aniline.To fabricate the catalyst support,ethylenediaminetetraacetic acid and Ni(OH)_(2) were uniformly mixed in deionized water until the solution turned blue at 90℃.The resulting blue solid precursor was then dried and annealed at 600℃ in argon to yield the magnetic support(Ni@NG).The support was then characterized using Raman spectroscopy,TEM,XRD,and XPS.TEM results revealed that the Ni@NG support exhibited a typical core-shell structure(with nanoscale Ni particles as the core and 2-5 layers of graphene as the shell).The Raman spectrum of the Ni@NG support exhibited the characteristic D and G bands of graphene at 1341 and 1604 cm^(−1),respectively.Moreover,the XRD spectrum of this support exhibited distinct peaks corresponding to Ni and graphene,while its XPS analysis confirmed the presence of an approximate nitrogen atom concentration of 3.64%in the nitrogen-doped graphene shell.Furthermore,the deposition-precipitation method was employed to synthesize a Pt-loaded Ni@NG catalyst(Pt/Ni@NG),which was later used in the catalytic hydrogenation of nitrobenzene in a liquid-phase reaction.Results revealed that increasing the Pt weight loading(mass fraction)from 0.1%to 0.5%altered the Pt dispersion state from single atoms to clusters and then to particles.In particular,at a Pt weight loading of 0.3%,the Pt/Ni@NG catalyst dominated by Pt clusters exhibited the highest activity for the hydrogenation of nitrobenzene.At this Pt weight loading,the catalyst achieved a turnover frequency of 27239.2 h^(−1) at 1 MPa reaction pressure under 30℃,completely converting nitrobenzene to aniline within 60 min.Furthermore,the Pt/Ni@NG catalyst maintained its activity over five testing cycles,attributed to its excellent liquid-phase magnetic separability.