Nickel–alumina composite aerogel catalysts with a high nickel load: a novel fast sol–gel synthesis procedure and screening of catalytic properties

AbstractNickel–aluminacompositeaerogelswithlargenickelloadingweresynthesizedusinganovelcomplexingagent-assisted sol–gel procedure to obtain materials displaying very large and open internal surface area, easily ac-cessible for large molecules and demonstrating excellent catalytic properties. They were tested in the followingreactions:(i)hydrogenationofpropeneand1-butene,(ii)methanizationofcarbondioxide,(iii)isometizationof1-butene,(iv)dehydrogenationofcyclohexane,(v)conversionofequimolarmixtureofCOandNOtoCO 2 andN 2 .Fullconversions and 100% selectivities were obtained in reactions (i), (ii), (iv) and (v) and an equilibrium composi-tioninreaction(iii).ThesecatalystsshowednopyrophoricactivityonexposingtoairevenatNicontentaslargeas50wt%. 2003ElsevierScienceB.V.Allrightsreserved. 1. IntroductionThenickel-basedcatalystsareofconsiderableindustrialinterest,especiallyforreactionssuchashydrogenationofaromaticsandunsaturatedhy-drocarbons, CO 2 =CH 4 reforming and reductionoffunctionalgroups[1–5],andaluminaismostoften used as nickel support. Quite often thesecatalystscontainaconsiderablenickelload,wellinexcessof10%(w/w)[2,5],toensureapropersurfacedensityandsizeofmetalclusters.How-ever,carbondepositionoverthemetallicandtheacidsidesofthesupportandNiparticlelossandsinteringathightemperatures,facilitatedbyhighnickelloadings,leadtocatalystsdeactivation.Itis well documented that this carbon depositiondecreaseswiththeincreaseinbasestrengthofthecatalystsandtheadditionoflantanium,magne-sium or molybdenium oxides has been foundparticularlyusefultodiminishthiseffect[3,6,7].