Cr and CeO2 Promoted Ni/SBA-15 Framework for Hydrogen Production by Steam Reforming of Glycerol

Abstract

Abstract Ni/SBA-15 meso-structured catalysts modified with Chromium and CeO2 (Ni-Cr-CeO2/SBA-15) were utilized to produce hydrogen from glycerol steam reforming (GSR). The catalysts were synthesized by a one-pot hydrothermal process and extensively characterized by analytical techniques such as N2 adsorption-desorption (BET), H2-temperature programmed reduction (H2-TPR), powder X-ray diffraction (PXRD), Inductively coupled plasma-optical emission spectrometry (ICP-OES), and Transmission electron microscopy (TEM). Overall, the Ni-based catalysts exhibited higher glycerol conversion − 12Ni-SBA-15-99.9%, 12Ni3CeO2-SBA-15-89.4% and 8Ni4Cr3CeO2-SBA-15-99.7%. Monometallic 12Ni/SBA-15 performed exceptionally well, while 12Cr/SBA-15 performed poorly with the highest 71.48% CO selectivity. For short-term GSR reactions, CeO2 addition to 12Ni/SBA-15 did not have any effect, whereas Cr addition resulted in 32% decrease in H2 selectivity. The long-term stability studies of 12Ni-SBA-15 showed H2 selectivity of ~ 64% and ~ 98% glycerol conversion. However, its activity was short-lived. After 20-30hrs, the H2 selectivity and conversion dropped precipitously to 40%. The doping of mesoporous Ni/SBA-15 with Cr and CeO2 remarkably enhanced the long-term stability of the catalyst for 12Ni3CeO2-SBA-15, and 8Ni4Cr3CeO2-SBA-15 catalyst with ~ 58% H2 selectivity and ~ 100% conversion for the entire 60hrs. Nonetheless, Cr and CeO2 seem to improve the shelf-life of Ni-SBA-15 via different mechanistic pathways. CeO2 mitigated Ni poisoning through coke oxidation whereas Cr bolstered the catalyst stability via maintaining a well-defined pore size and structural integrity of the heterogeneous framework, thereby restricting structural collapse, and hence reducing sintering of the Ni active sites during the long-term 60hrs continuous reaction.