In this paper, a series of hexaaluminate oxides, LaMAl 11 O 19-δ (M=Fe, Co, Ni, Mn and Cu), were prepared using transition metals M to substitute Al in the hexaaluminate lattices. XRD analyses indicated that the series of hexaaluminates had almost the same magnetoplumbite crystal structure, however, they exhibted different reducibility and catalytic activities for CO 2 reforming of methane to synthesis gas. Among the LaMAl 11 O 19-δ samples, LaNiAl 11 O 19-δ showed the best catalytic activity for the reaction at 1 053 K for 2 h, the conversion of CH 4 and CO 2 was 98.8% and 97.6%, respectively, and the catalytic activities of rest Msubstituted catalysts were extremely lower than that of LaNiAl 11 O 19-δ . The sequence of affection on catalytic activity of transition metal M for the topic reaction was NiCo>Fe> Mn> Cu.
In this paper,the kinds and amount of carbon deposited over Ni base hexaaluminate LaNiAl 11 O 19 catalyst,after both CH 4 decomposition and CO 2 reforming of methane,was determined by means of X ray photoelectron spectroscopy (XPS) and thermogravimetric analysis(TGA) techniques,respectively.Over the catalyst,the rates of carbon deposited vs reaction time were also investigated during the reaction.Two carbon forms were produced,and graphitic carbon was the main and inactive carbon.
A series of Ni modified hexaaluminates LaNi y Al 12- y O 19- δ ( y =0 3, 0 6, 0 9, 1 0) were prepared by decomposition of nitrates and calcination at high temperature. The crystalline structure and catalytic properties for CO 2 reforming of methane to synthesis gas were investigated by using XRD, XPS, TPR and TGA techniques. The results showed that a pure hexaaluminate LaNi y Al 12- y O 19- δ phase is formed only when y value is in 0< y ≤1. The reduced hexaaluminates LaNi y Al 12- y O 19- δ exhibit significant catalytic activity and stability for the reaction of CO 2 reforming of methane to synthesis gas at 780 ℃, and no deactivation resulting from carbon deposition is found. In the meantime, the catalytic activity is obviously affected by the modifier Ni in the hexaaluminate lattices. Under the same reaction conditions, the conversion of CH 4 and CO 2 increase with increase in the amount ( y value) of the modifier Ni.
