Chemical control of the characteristics of Mo-doped carbon xerogels by surfactant-mediated synthesis

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• 作者：Francisco J. Maldonado-Hó ; dar ; ^{fjmaldon@ugr.es} ; Hana Jirglová ; ¹ ; Agustí ; n F. Pé ; rez-Cadenas ; Sergio Morales-Torres
• 刊名：Carbon
• 出版年：2013
• 出版时间：January, 2013
• 年：2013
• 卷：51
• 期：Complete
• 页码：213-223
• 全文大小：1443 K

文摘

Carbon xerogels doped with Mo were prepared by a sol-gel modified method for the resorcinol (R) - formaldehyde (F) polymerization (RF-gels). The use of surfactants (S) yields composites (RFS-gels), the S molecules are incorporated to the gel structure generating different metal anchoring sites. The interaction of molybdate ions with RF and RFS-gels was analysed. The adsorption is favoured by the attractive interactions with the RFS-gel containing a cationic surfactant, and by the presence of oxygenated chemical groups introduced by the non-ionic surfactant. The smallest Mo-loading was obtained in RFS-gels containing anionic surfactant as a consequence of repulsive interactions. The adsorbed Mo-species influence on the curing of the polymeric gels, inducing a larger shrinkage and a lower microporosity of the carbon xerogels. The dispersion and chemical nature of Mo particles depend also on the Mo-gel interactions. Stronger attractive interactions avoid sintering in some extent and favour the reduction of the molybdate with formation of a mixture of ¦Á-Mo₂C and MoO₃, while MoO₃ particles were only found in RF-Mo or anionic RFS-Mo carbon xerogels. Only propene was obtained as product of the isopropanol decomposition showing the acid character of these catalysts. The catalytic activity is correlated to the proportion of Mo₂C formed in each sample.