Tuning the acidity of SAPO-34 zeolite through niobium incorporation for enhanced catalytic performance during MTO reaction

Abstract

SAPO-34 zeolite is commonly used for light olefin production, an important petrochemical, through the methanol-to-olefin (MTO) conversion process. To modify the physicochemical characteristics of the SAPO-34 zeolite, a series of Nb-incorporated SAPO-34 catalysts were synthesized to alter the crystal size and acidity of the catalysts to enhance its MTO catalytic properties. The Nb incorporation reduced crystal size from 4.6 μm to 1.4 μm, with enhanced acidity for the Nb0.005SP catalyst. The catalytic results revealed that the Nb0.005SP catalyst showed remarkably superior MTO conversions, ∼2.5 time as compared with conventional SP catalyst, due to its reduced crystal size, higher surface area and higher acid sites concentration owing to its shorter diffusion pathlength, greater number of exposed active sites and ability to maintain MTO reaction for longer time, respectively. Moreover, the Nb0.005SP catalyst also exhibited a lower hydrogen transfer index-HTI index with a slight slope, leading to slower coking, enhanced light olefine selectivity and a longer lifetime compared to other counterparts.