A series of graphene-oxide- supported Cu-Al and Co-Al hydrotalcites (M/Al = 2:1) were synthesised by coprecipitation at constant pH and tested for carbon-carbon coupling via Ullmann reaction. All the investigated catalysts were characterised by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) ,thermogravimetric analysis (TGA), x-ray photoelectron spectroscopy (XPS), and nitrogen adsorption at 77K.All catalyst systems showed reflections typical for layered double hydroxide (LDH) structures with no phase impurities apparent.For the hybrid catalysts, no significant effect of the graphene oxide (GO) on the thermal LDH degradation was observed. The actual GO weight percentage in the sample was estimated from the TGA residue.The specific surface area of the Cu-Al LDHs is significantly larger than for the Co-Al LDHs, consistent with the smaller Cu-Al LDH particle sizes observed by SEM and deduced from XRD analysis. This inclusion of 3 wt.% GO led to 100% increase in the BET-surface area for Cu-Al LDH and Co-Al LDH catalysts. The catalytic conversion of idobenzene into biphenyl under reflux was increased in the order Cu-Al LDH &gt; Co-Al LDH &gt; Cu-Al LDH /GO &gt; Co-Al LDH/GO. The GO supported catalysts showed better catalytic performance after 5 times regenerated in comparison to the GO unsupported ones. The high performance of these catalysts was attributed to the co-operative contribution of its redox nature and large surface area provided by the inclusion of 3 wt.% GO.

Graphene-oxide-supported Cu-Al and Co-Al hydrotalcites as enhanced catalysts for carbon-carbon coupling via Ullmann reaction

251st National Meeting (2016)

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