Nanostructured functionalised niobium oxide as chemoselective catalyst for acetalation of glucose

Kumar, Sahil and Saini, Kanika and Saravanamurugan, Shunmugavel and Zhang, Xiaolei and Kansal, Sushil Kumar (2022) Nanostructured functionalised niobium oxide as chemoselective catalyst for acetalation of glucose. Topics in Catalysis, 65 (19-20). pp. 1994-2004. ISSN 1572-9028 (

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Developing a chemoselective catalyst for the acetalation of biomass-derived glucose to alkyl glycosides has been recognised as an emerging field due to its wide range of applications. The present study focuses on synthesising sulfate functionalised niobium oxide-based (NbOx-DS) catalyst to introduce medium/strong acidic sites that contribute to the catalytic activity towards glucose acetalation, which has not been explored previously. The nanosized NbOx-D is prepared via a precipitation approach using niobium chloride and diethylamine as a precursor and precipitating agent, respectively. The sulfate groups incorporated NbOx-DS gives a good yield of ethyl glucosides (60%) with excellent selectivity (97%) in ethanol. On the other hand, the sulfate groups incorporated into the commercial niobium oxide (NbOx-CS) exhibits poor catalytic activity, yielding 6% ethyl glucoside with a low selectivity (8%). FTIR analysis corroborates the incorporation of sulfate groups in the NbOx-DS matrix, unlike NbOx-CS. XRD pattern of NbOx-DS shows a lower angle shift of a peak to 23.5° compared to parent NbOx-D (24.32°), indicating lattice expansion due to the incorporation of sulfate groups, and no such a shift in the case of NbOx-CS is observed. NH3- temperature programmed desorption ( NH3-TPD) reveals that NbOx-DS possess a 2.1-fold higher number of acidic sites than NbOx-D, whereas NbOx-CS possess a negligible number of acidic sites, indicating the significance of the synthesis procedure of NbOx-D for efficient incorporation of sulfate groups. NbOx-DS displays recyclability for at least three runs with minor loss in the activity. In a nutshell, the current study reflects that NbOx-DS obtained via precipitation followed by sulfate groups incorporation increases the medium/strong acidic sites, which contributes significantly to enhancing the ethyl glucoside selectivity (97%).