Urban gas production from low H2/CO biogas using Re-promoted Ni catalysts supported on modified manganese sand

Abstract

Re-promoted Ni catalysts supported on the raw manganese sand (RMS) and HNO3/ NH3·H2O/H2O2 modified manganese sand (MMS) were prepared by co-impregnation method. The catalysts were tested for urban gas production from low H2/CO biogas by partial methanation coupling with water gas shift (WGS). A series of characterization analysis including XRF, ICP, nitrogen isothermal adsorption, XRD, H2-TPR, H2-TPD, TG, XPS, TEM, SEM and DRIFTS were employed to comprehensively investigate the physico-chemical properties of the supports and catalysts. The results showed that the Ni-Re/RMS catalyst was more active than the Ni/RMS catalyst due to the improved dispersion of Ni particles. Through further modification on the RMS, it was found that Ni-Re/MMS-H2O2 catalyst showed a superior synergy effect on catalyzing methanation coupling with WGS over the other four catalysts. The addition of Re promoter facilitated to increase the proportion of β-type NiO for forming more Ni active sites after reduction as well as to inflict electronic effect, which could enhance the electron cloud density of Ni atoms to promote CO disassociation during the reaction. H2O2 was more suitable to be the modification reagent than HNO3 and NH3·H2O, owing to its positive contribution to the enhancement of anti-sintering and anti-coking ability of the catalysts. The lower heating value of outlet gas catalyzed by Ni-Re/MMS-H2O2 catalyst at the condition of H2/CO = 0.8, H2O/CO = 1.0 and 400 °C was 10.63 MJ/Nm3, implying the feasibility of using Re-promoted Ni catalysts for urban gas production from low H2/CO biogas and the promising potential of utilizing low-cost manganese sand as catalyst support.