Synthesis Of Mesoporous Mn Based Bimetallic Oxides And Selective Oxidation Of Benzyl Alcohol To Benzaldehyde

As an important industrial materials, benzaldehyde have been widely used in food, medicine, dyes, spices, etc, which can be prepared by the methods of toluene chlorination hydrolysis, toluene oxidation, methyl benzoate reduction, benzyl alcohol oxidation, etc. The method of benzyl alcohol oxidation is one of the most potential means because of green environmental protection and high yield. At present, many noble metals (Ru, Au, Ag, Pd) as a high activity catalysts were used in benzyl alcohol oxidation to Benzaldehyde, but the price is expensive, so looking for a kind of Non-noble metal catalysts to replace noble metals is particularly important. The metal of Mn and its oxides as catalyst have been widely studied due to rich resources and low price, but there is also a big distance compared with noble metals on catalytic activity. It is very meaningful to prepare a kind of high-efficiency Mn based metal oxides as catalysts in oxidation of benzyl alcohol. In this paper, the catalytic activity of Mn oxides was improved by the modification of catalyst morphology and bimetal compound based on Mn. Mainly includes the following two parts:First part, the mesoporous bimetallic oxides Cu-Mn-x (x means the ratio atomic of the Mn and Cu) was obtained by thermal decomposition of single crystal oxalate synthetized by coprecipitation.It was used in benzyl alcohol oxidation to Benzaldehyde as the catalyst. It shows the highest catalytic activity, when the design atomic ratio of Cu and Mn was 1:2. The conversion of benzyl alcohol is over 90% only in 30 min when using Cu-Mn-x as the catalyst. A series of characterization methods proved that the Cu doped can improve the activity of Mn oxides, but it must be controlled in a certain ratio, too little or too much can’t effectively increase the activity, maybe the right proportion of Cu doped can weaken the binding energy of Mn-O keys, which provides more oxygen species for catalytic process. In addition, the effect of different amounts of catalysts on activity was investigated, it turned out that the higher activity the more catalysts. This may be related to the mesoporous morphology, the mesoporous structure of the catalyst provides a place for catalytic process, the more catalysts the greater active sites.Second part, the mesoporous bimetallic oxides X-Mn-2 (X means Mn, Cu, Co, Ni, Zn) was also obtained by thermal decomposition of single crystal oxalate synthetized by coprecipitation. Its application in catalytic oxidation of benzyl alcohol was found that Ni-Mn-2 catalyst has good catalytic activity. Benzyl alcohol could be completely converted into benzaldehyde within 30 minutes, when oxygen was used as oxidant and Ni-Mn-2 as the catalyst, and its catalytic activity is obviously higher than single metal oxides of Mn-Mn-2 catalyst. Moreover, the catalytic activity of Zn-Mn-2 catalyst significantly was weaker than single metal oxides of Mn-Mn-2 catalyst. A series of characterization techniques proved that Ni doped in the manganese oxide can not only increase its surface area, but also improves the ability of its oxidation, and changes the ratio of Mn2+, Mn3+ and Mn4+. But the addition of Zn gets the opposite results, it shows that the synergy of the bimetallic oxides is able to enhance the activity for some metals, also can decrease the activity for some others.