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Effect of Mg2+ on the catalytic activities of CoMgAl hydrotalcites in
the selective oxidation of benzyl alcohol to benzaldehyde
Weiyou Zhou, Jie Liu, Jiugao Pan, Fu’an Sun, Mingyang He*, Qun Chen
Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, Changzhou University, Changzhou 213164, China
Abstract With the knowledge the significant effect of basic site on the catalytic performance of heterogeneous
catalysts in the selective oxidation of alcohol, a series of Co2MgxAl-LDHs (x=0, 0.5, 1.0, 1.5, and 2.0)
compounds with different Mg2+ contents have been prepared, characterized and introduced into the selective
oxidation of benzyl alcohol with TBHP as the oxidant. The results showed that introducing Mg2+ ions can not
only influence the amount of basic site, but also promote the oxidation process of Co2+ to Co3+. These facts must
contribute to the markedly improved catalytic activities of Co2MgxAl-LDH samples.
Keywords: Hydrotalcite-like compounds, magnesium ion, benzyl alcohol, Selective oxidation, Benzaldehyde
1. Introduction
Benzaldehyde is an important raw material in perfumery and pharmaceutical industries. Selective oxidation
of benzyl alcohol to benzaldehyde under efficient catalyst is an industrially important reaction as it avoids large
amounts of highly toxic heavy metal wastes, generating from traditional production process [1,2]. Therefore,
various catalysts have been developed for the reaction. Although noble metal catalysts are known to be effective
catalysts for liquid-phase aerobic oxidation of benzyl alcohol, the base additives are always needed [3,4]. To
avoid the using of soluble base, basic supports, such as MgO, Mg(OH)2, hydrotalcite (HT), etc., has been widely
applied as the support for noble metal catalysts, such as Pd [5], Au [6], Pt [7] and Ru [8]. It has been
demonstrated that the Au/HT catalysts can be more active in the absence of base additives than other commonly
used gold catalysts such as Au/TiO2, Au/CeO2 and Au/Al2O3. Under the optimized conditions, the conversion of
benzyl alcohol reached to 96% with a selectivity of >99%, suggesting synergy between AuNPs and basic sites
of the HT [9,10]. However, from the viewpoint of economy and sustainable chemistry, it is especially important
to develop economically catalysts for the selective oxidation of benzyl alcohol, because noble metal catalysts are
highly expensive and scarce.
Actually, some catalytic systems based on transition metals have been reported using O2, H2O2 or
tert-butylhydroperoxide (TBHP) as the oxidants, including Co@SiO2@[Ni(II)SBC] [11], NiAl-LDH [12],
N-CNTs [13], CeCrO3 [14], etc. However, few reports on the adjustment of surface basicity of catalyst and the
*
Corresponding author.
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