Green synthesis of functionalized graphene and their use as solid acid catalysts
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ARTICLE Green synthesis of functionalized graphene and their use as solid acid catalysts Xu Zhang,a) Qiuyu Fan, and He Yang School of Petroleum & Chemical Engineering, Dalian University of Technology, Panjin 124221, China (Received 3 July 2018; accepted 10 September 2018)
Here we report a facile and mild synthesis of the sulfonated graphene (PSS-RGO) catalysts by in situ polymerization of sodium p-styrenesulfonate. Graphene sheets can be used as the flat backbones to graft abundant sulfonate groups on both sides. The PSS-RGO catalysts were characterized by 1H Nuclear Magnetic Resonance (1H NMR), energy dispersive spectrometer, Raman spectroscopy, X-ray photoelectron spectroscopy, and so on. The catalytic properties of the PSS-RGO catalysts for the hydrolysis of ethyl acetate and the esterification of acetic acid with ethanol were evaluated, showing that the as-made PSS-RGO catalysts were active for both probe reactions. The possible deactivation mechanism involved in the surface catalysis of the graphene-based acid catalysts has been addressed.
I. INTRODUCTION
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.369
Graphene, a one-atom thick sheet made of hexagonally arrayed sp2-bonded carbon atoms, is the thinnest material with extraordinary mechanical, electrical, thermal, chemical, and optical properties, and may be used as as an ideal support for various functional groups to tune the structure and catalytic performance of graphene.21–24 Graphene is the very appealing plat material to be sulfonated in virtue of the structural merits with considerable solubility. Recently, there are some reports on the preparation of graphene-based solid acid catalysts with a high S content on the graphene surface. For example, sulfated graphenes can be synthesized by anchoring the sulfonic acidcontaining aryl radicals on graphene,9,25 by sulfonating the graphene in Ar with chlorosulfonic acid14 or modified graphene with Oleum under harsh conditions.26 In situ polymerization is an effective way to construct a nanocomposite material. This method affords a unique way to bond an initiator on the graphene surface by a chemical reaction and then to use the initiator to trigger an in situ chain growth of the monomers to form a polymer grafted graphene.27,28 Herein, we report a green synthesis method for making graphene-based solid acid catalysts (PSS-RGO) by in situ polymerization of sodium p-styrenesulfonate (NaSS) under controllable and mild conditions. This strategy has its own advantages compared with the previous reports. First, the NaSS could be polymerizd and grafted to graphene in one step under mild conditions. Second, graphene sheets can be used as flat backbones to produce graphene-based molecular brushes by in situ polymerization, which along with the in situ chain growth of the monomers, abundant sulfonate groups could be grafted to graphene sheets. Third, the polymer chains could well maintain the stability of graphene sheets in solution, increasing the accessibility of the reagent
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