Effect of Silicates and Carbonates on the Structure of Nickel-Containing Hydrotalcite-Derived Materials

Abstract

The NiAl and NiAlSi were prepared by coprecipitation method at constant basic pH, calcined at 800 °C, and characterized by ICP analysis, XRD, FTIR, SEM, BET method and (TPR). The CH₄/CO₂ reaction was carried out in a fixed-bed tubular reactor at 750 °C. A reactant mixture CH₄ and CO₂ were mixed at a ratio of 1 diluted in He (10:10:80). The XRD patterns of the “as prepared” materials exhibit the characteristic diffractions of hydrotalcite-like layered double hydroxide materials, although were not clearly evidenced in the Si containing samples. Nevertheless, after calcination this hydroltacite-like structure is destroyed. We have studied the reaction of dry reforming of methane by carbon dioxide in presence of various catalysts at 750 °C. In the case of NiAlSi, the CH₄ conversions were close to 70%, with a H₂/CO ratio close to 0.9. Nevertheless, the NiAl sample presented a very variable conversion and a high carbon formation, what resulted in a blocking of the reactor at the end of the experience and a decrease in the H₂/CO ratio, which indicates that probably the CO₂ is consumed in parallel in the reverse water gas shift reaction (RWGS). We have shown that Ni/Al/Si mixed oxides obtained through the thermal decomposition of layered double hydroxide-type precursors are promising catalysts in the reforming of methane with CO₂.