Catalytic performances of natural Ni-bearing clay minerals for production of syngas from dry reforming of methane

Abstract

The catalytic activity of Ni-bearing clay minerals obtained from natural nickel lateritic ores from Niquelândia, Brazil was evaluated in methane dry reforming reaction at 800 °C. These phyllosilicates materials are Ni/Mg smectites with a Ni content of about 23 wt %. The mineralogy and the crystallochemistry of the clay minerals were characterized using X-Ray diffraction and FTIR spectroscopy respectively. Prior to any catalytic test, the clay fraction was extracted from the lateritic ore to concentrate the smectites and remove primary minerals (quartz, pyroxenes) or impurities. In these samples, the Ni is localized in the octahedral layers (structural Ni) and in the interlayer space (exchangeable Ni). To evidence the impact of octahedral or exchangeable Ni, the clays were saturated either with Mg or with Ni. The activity in methane dry reforming is higher with the clay minerals saturated with Ni compared to those saturated with Mg. These results support the hypothesis that both octahedral and exchangeable Ni play a role in the conversion of CH4 and CO2 into H2 and CO. Finally, in situ XRD and TEM analyses were crucial to explain the strong influence of the reduction temperature on the H2 yield. In these natural nickel lateritic ores, the presence of Fe leads to strong interaction with Ni during the reduction step, which depending on its temperature can result in the loss of catalytic activity.