Pt(-M) Nanoparticles Supported On Ordered Mesoporous Materials For Liquid-Phase Selective Hydrogenation

In the preceding work of our project group, we noticed CMK-3 loaded noble metal performed excellent catalytic effect. Therefore, in the first part of this paper, Pt/CMK-3 catalyst was prepared by excessive impregnation method firstly, with the particle size distribution around 1.5-2.5 nm. When the catalyst was used for hydrogenation of nitrobenzene, the catalytic effect was better than the result of commercial Pt/C catalyst. Due to the dissolving capacity of aromatic nitro-compounds in neat ethanol was better than that of the mixed solvent with water and ethanol, the reaction rate of aromatic nitro-compounds in ethanol was higher than that in mixed solvent. All the nitrobenzene and its derivatives reacted quickly in neat ethanol, and the highest TOF of 43.8 s-1 was obtained by 2-CH3 nitrobenzene which has an electronic donating group. In addition, the selectivity of aniline derivatives can reach 99%, except chloronitrobenzenes were dechlorinated a little in ethanol. It is worth noting that the Pt/CMK-3 catalyst showed a better performance of repeated use, without any activity and selectivity decreasing after the fifteenth recycling.For the second part, we used mesoporous silica materials with different symmetry as the base, and introduced alumina into the mesoporous pore channels of mesoporous silica materials to prepare alumina-silica composite materials. The composite materials were used as support to prepare Pt0.8Fe0.2/15AX catalysts, which were used for the selective hydrogenation of cinnamaldehyde. We found the Pt-Fe catalysts loaded on Al2O3@SBA-15 with 2D hexagonal structure performed relatively better catalytic results. The highest conversion can reach 69.2%, and the highest cinnamyl alcohol selectivity can reach 85.9%. In order to further optimize the reduction method of catalyst precursors, the Pt0.8Fe0.2/15AS catalysts were reduced by sodium formate. Under such condition, the catalytic effects were improved prominently with the highest TOF of 7040.7 h’1 and the highest cinnamyl alcohol selectivity of 85.2% achieved. Furthermore, after the catalyst was used of seven times, the catalytic activity did not decrease notably, among which the cinnamyl alcohol selectivity can reach 90%. For the catalyst preparation method, whether the metals (Pt, Fe) loaded order, calcination temperature, alumina content in the composite materials, or impregnating method, all can impact the catalytic effect. When preparing Pt, Pt-Fe catalysts on the basis of MCM-41, the pores were easy to be blocked, leading to worse catalytic results for hydrogenation of cinnamaldehyde. Even though a certain hydrocinnamaldehyde selectivity was obtained for PtCux/15AS catalysts, the selection advantage of C=C hydrogenation was not significant.