Study On Preparation, Modification And Catalytic Performance Of Nano Aluminosilicates Solid Acid

Aluminosilicates solid acids catalysts play an important role in petrochemical industry. The size and dispersion of aluminosilicates have a significant effect on their catalytic activity especially for the liquid phase Beckmann rearrangement reaction. However, the problems resulting from nanoparticles, including preparation method, actual catalytic performance and stability still need to be addressed. In this paper, a novel efficient supported nanosized-aluminosilicates solid acid catalyst is well designed and prepared by absorption phase method based on previous work.Firstly, well-dispersed and size-controlled nanosized aluminosilicates solid acid is in situ prepared on the surfaces of silica gel particle, by precisely controlling the reaction conditions, including the precursors, the bulk phase. TEM shows that the size distribution of the nano solid acid catalysts is between2and5nm. In the structure fine aluminosilicates particles suggest high acid catalytic performance, and stable silica nanoparticles inhabit the agglomeration of nano-aluminosilicates particles and improving the stability of supported catalysts. The nano-aluminosilicates particles with amorphous phase are filled with some micro phase with ordered structure, illustrated by HRTEM and XRD. These catalysts are used to liquid phase Beckmann rearrangement reaction of cyclohexanone oxime, showing higher catalytic activity. FTIR and NH3-TPD are conducted to interpret the catalytic results. The highest catalytic activity could be achieved by optimized the precursors, the components of bulk phase under following steps.In order to improve the catalytic performance, small amount of other elements, including Ti, Zr, Cr. Mo, W, Co. and Ni are doped into the supported nanosize aluminosilicates to adjust and control the properties of acid sites, considering that their corresponding oxide showing different acid properties. TEM show the morphology and structure changes little. However, the composition and distribution of the acidic sites are largely changed with the element doping, which are evidenced by FTIR, NH3-TPD. According to the Beckmann rearrangement reaction, doping with Ti, Zr, Mo, W. Co, and Ni could highly enhance the catalytic activity, except Cr. For Ni-doping, the doping sequence and amount have great impact on catalytic activity, which is similar to Ti-doping. Both Ni-doping and Ti-doping samples with doping amount of2wt%shows the highest catalytic activity.