Ni-Co@C-N催化剂的制备及其催化硝基芳烃还原偶联反应

Preparation of Ni‑Co@C‑N catalysts for application to nitroaromatic‑azoxybenzene reduction coupling reaction

以ZIF-67为前驱体,通过高温热解和乙二醇还原的方法制备了低成本的负载镍纳米粒子催化剂Ni-Co@C-N。研究了催化剂对硝基芳烃化合物合成相应氧化偶氮苯类化合物的催化性能,并讨论了碱及分散剂种类对催化剂结构与性能的影响。结果表明,碱性增强可以加快纳米粒子的成核速率,分散剂分子量增加则会限制纳米粒子的粒径增长。其中,由弱碱与低分子量分散剂制备的Ni-Co@C-N-4对硝基芳烃还原具有良好的催化活性,原料的转化率和产率在反应30 min后分别达到92.8%和89.3%,且循环实验表明Ni-Co@C-N-4具有良好的稳定性。

The low‑cost supported nickel nanoparticle catalysts Ni‑Co@C‑N were prepared with ZIF‑67 as a precursor by pyrolysis and then ethylene glycol reduction.The characterization results of X‑ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),and X‑ray photoelectron spectroscopy(XPS)indicated the successful preparation of supported nickel nanoparticle catalysts Ni‑Co@C‑N,Ni and Co nanoparticles uniformly dispersed.Weak bases such as Na2CO3 and low molecular weight PVPk18 dispersants contribute to the loading of Ni nanoparticles.The results of N2 adsorption‑desorption indicated that the specific surface areas of the Ni‑Co@C‑N materials were between 107 and 211 m2·g-1,and the average pore widths were between 7.4 and 11.2 nm.The catalytic performance of the Ni‑Co@C‑N catalysts for the synthesis of nitroaromatic compounds into the corresponding oxide azobenzene compounds was studied,and the effects of the types of alkali and dispersant on the structure and properties of catalysts were also discussed.The results demonstrated that the alkaline enhancement accelerated the nucleation rate of nanoparticles while increasing the molecular weight of dispersants limited the size growth of nanoparticles.Among them,Ni‑Co@C‑N‑4 prepared by the weak base and low molecular weight dispersant possessed the best catalytic performance,the conversion rate and yield of raw materials reached 92.8%and 89.3%respectively after 30 min of reaction,and the cycle test showed that Ni‑Co@C‑N‑4 had good stability.