Influence of gelation and calcination temperature on the structure-performance of porous VOX-SiO2 solids in non-oxidative propane dehydrogenation

VOX-doped porous SiO2 solids (VOX-SiO2) were synthesized at different gelation and calcination temperatures through an in-situ one-step synthesis and evaluated by non-oxidative propane dehydrogenation (PDH), exhibiting excellent catalytic performance. VOX-SiO2 catalysts were characterized by XRD, low temperature N-2 adsorption/desorption, SEM, TEM, UV-Vis, Raman, XPS, NH3-TPD, H-2-TPR, and TGA. The structural and performance results for the catalysts reveal that gelation temperature has only a slight effect on the surface acidity, textural properties and VOX species dispersion of VOX-SiO2 catalysts within a reasonable temperature range (30-60 degrees C). The 60-VOX-SiO2-580 catalyst, with a gelation temperature of 60 degrees C, a calcination temperature of 580 degrees C, and prepared by the one-step synthesis method, obviously shortens gelation process time by half compared to catalyst gelled at 30 degrees C and exhibits superior catalytic performance for PDH. Over high gelation temperature (>= 75 degrees C) leads to the loss of integrity and decreases catalytic activity of the VOX-SiO2 catalysts. Compared with the VOX-MCM-41 catalyst prepared by a one-step hydrothermal method, VOX-SiO2 catalysts exhibit better catalytic activity and stability. Importantly, at a reaction temperature of 580 degrees C, the 60-VOX-SiO2-580 catalyst exhibits remarkable long-term catalytic stability in the eight reaction-regeneration cycles for PDH. Its propane conversion shows a slow decrease from 55% to 45% for a 4 h reaction duration, but the propene selectivity remains at approximately 91%. The results of this work will be beneficial for further industrial development and application of porous VOX-SiO2 solids in catalysis. (C) 2017 Elsevier Inc. All rights reserved.