磷化铁/石墨烯纳米复合物的制备及其在F-T合成反应中的应用

Abstract

作为一种新型碳材料,石墨烯(G)具有较大的比表面,因而可以作为载体担载多种金属或金属氧化物.通过水热法一步合成了磷酸铁/氧化石墨复合物(FePO/GO),氧化石墨(GO)上复合的磷酸铁(FePO)呈多孔状,粒径为100～300nm.以FePO/GO为前体,在氢气氛围下,通过煅烧进一步合成了磷化铁/石墨烯纳米复合物(FeP/G).粒径为10 nm左右的磷化铁(FeP)均匀的分散在石墨烯表面,主要暴露(201)晶面.石墨烯不但能调控FePO的结构,而且还能促进FePO的还原.FeP/G催化剂可以用于费-托反应,相对于非负载的FeP,FeP/G具有较高的催化活性、对长链烃较高的选择性以及较高的烯/烷比.

Graphene (G) is a huge open it-electron system with a unique electronic structure, which ignites diverse applications such as electronics, photovoltaics, batteries, supercapacitors and so on. Because of the larger surface area, G can be used as the catalyst or the advantageous carrier for the catalytic active components for hydrogenation, oxidation and carbon-carbon coupling reactions. In the present study, we exploited G as a support for iron phosphide nanoparticles (FeP/G) by calcination the precursor iron phosphate-graphene oxide nanocomposite (FePO/GO) under hydrogen atmosphere. In the same method, we also prepared the control pure iron phosphide (FeP) by H-2 calcination the precursor iron phosphate (FePO). The FePO of FePO/GO existed in the form of porous spherical and the particle size ranges from 100 nm to 300 nm. After transforming into FeP, the average particle size of FeP is about 10 mu while the particles were uniformly dispersed on the G and no obvious aggregation was observed. While, not only the pure FePO but also the pure FeP was powerful aggregation. That meant GO and G could regulate the microstructure and morphology of FePO and FeP, respectively. The as-prepared products were investigated by X-ray diffraction, transmission electron microscopy, field emission environment scanning electron microscopy and XPS spectroscopy. XPS spectra showed that the electron binding energy of Fe in FeP/G increased slightly. The Fischer-Tropsch Synthesis (FTS) reaction has been selected as model reaction for evaluating FeP/G. When the reaction conditions were 15 mg catalyst (reduced in H2 at 623 K for 2 h prior to FTS reaction), 2 MPa syngas (CO : H-2 : Ar=32 : 63 : 5), 5 mL.min(-1), 593 K, the remarkable catalytic discrepancies in FTS activity and product selectivity were observed. The activity toward the conversion of CO on FeP/G was about 70 times that of FeP. The result show that FeP/G catalysts are potential good catalysts for FTS.