Oxidative Desulfurization of Benzothiophene by Persulfate and Cu-Loaded g-C₃ N₄ via the Polymerization Pathway

Abstract

Turning aromatic sulfur impurities to value-added polymers is a promising technology for fuel desulfurization. In this study, Cu(I,II)@g-C 3 N 4 plates prepared via facile calcination show high reactivity in catalytic oxidation of benzothiophene (BT) by persulfate in a mixture of MeCN/H 2 O (v/v = 50/50). Quenching experiments rule out the primary contributions of SO 4•− , • OH, and O 2•− to BT oxidation and confirm the presence of carbon-centered radicals during the desulfurization process. XPS and Raman analyses reveal that Cu(I) and graphitic-N are reactive sites for persulfate activation, accompanied with moderate activation of the peroxo group in persulfate via the nonradical pathway. Solid characterizations indicate the formation of polybenzothiophene S,S-dioxide during the oxidation process, which further reveals that the moderately activated persulfate abstracts H from BT to form a BT radical cation, followed by subsequent polymerization of BT radical cations to a BT tetramer, and then the BT tetramer is further oxidized to a BT S,S-dioxide tetramer. The high electrochemical stability and pseudo-capacitive properties of the obtained polymers also imply their high potential to be used for capacitors. This work provides new insight on turning aromatic sulfur impurities in fuels to "treasures".

Highly Selective Photooxidation of Benzyl Alcohol to Benzaldehyde by Bi–Mo/g-C3N4 in Aqueous Solution

“…Meanwhile, the slight shift of the (002) plane of Bi–Mo/CN-2 from 27.6 to 27.4° compared with those of CN, Bi/CN, and Mo/CN indicates the increased stacking distance between the CN nanosheets due to the addition of Bi and Mo in pyrolysis. Our recent work suggested that the doped Cu­(II) influenced the crystallinity of CN by bringing about a shift of the diffraction peak at 27.4 to 27.6° and the decreased peak intensities of the (002) plane . Moreover, the absence of Bi and/or Mo oxides in the XRD patterns of Bi/CN, Mo/CN, and Bi–Mo/CN-2 indicates the uniform distribution of Bi and/or Mo in the CN structure.…”

“…The oxidizing species on the surface of catalysts (e.g., superoxo and peroxo species) can effectively mediate the oxidation selectivity of H-rich substrates via the H-abstraction pathway. , For instance, our recent works suggested that the surface Bi–OO• superoxo and Bi–OOH peroxo during the photocatalytic activation of O 2 on Bi 2.15 WO 6 not only selectively oxidized benzyl alcohol to benzaldehyde via the H-abstraction pathway, but also contributed to the oxidation of various H-donors such as As­(III), glucose and phenolics with the production of H 2 O 2 , indicating the high reactivity of surface superoxo and peroxo species in H-abstraction . Likewise, Lyu et al suggested that the surface Ti–OOH peroxo on Pd@HTS-1 achieved 46.4% conversion of benzyl alcohol with high selectivity of 100% toward benzaldehyde.…”