Syngas production from CO2 reforming of methane over Ni supported on hierarchical silicalite-1 fabricated by microwave-assisted hydrothermal synthesis

Abstract

The conversion of carbon dioxide and methane to syngas is one of the most environmentally benign routes for methane reforming, where the two major greenhouse gases are converted to hydrogen or syngas (H2 and CO). Hierarchical silicalite-1 was prepared in one-step by the microwave-assisted hydrothermal synthesis (MAHyS) approach. Ni particles with loadings of 5, 10, 15 and 20 wt.% were impregnated on the silicalite-1, as well as modified silicalite-1. The mesopore volume of the 20 wt.% Ni on S-1 catalyst increased from 0.0712 cm3/g to 0.1159 cm3/g by ion-exchanging silicalite-1 with Ce, prior to impregnation. The structural integrity of the modified catalysts was maintained as shown by characterization with XRD, FESEM, N2-physisorption, XPS and FTIR. Reducibility studies by H2-TPR showed that the addition of a second metal enhanced Ni reducibility. The 20 wt.% Ni on silicalite-1 was found to be more active than 10 and 15 wt.% on silicalite-1. Upon modification before impregnation of the 20 wt.% Ni, it was observed that Ce-ion-exchanged silicalite-1 supported Ni catalyst was the most active catalyst during 12 h time-on-stream (TOS). Raman spectroscopy and TGA-DSC revealed that the carbon deposits on the surfaces of the spent catalysts were predominantly crystalline.