Optimization of the pore structure and acidity of SAPO-11 for highly efficient hydroisomerization on the long-chain alkane

摘要

To obtain both high conversion and selectivity on the long-chain alkane hydroisomerization is still challenging. Herein, we report an excellent hydroisomerization catalyst with flower-like morphology, using the dual-additive synthetic method to simultaneously modulate the pore structure and acidity of SAPO-11 molecular sieve, with the activated carbon and n-butanol as additives. Various characterization results show that the dual additives have a synergistic promotion effect on the as-synthesized samples: (i) the dual additives promote the formation of higher external surface area and more mesoporous structure with suitable mesopore distribution; (ii) the total Bronsted acid sites of prepared SAPO-11 samples are enhanced by the dual additives and Bronsted acid strength are optimized as well. The resulting SAPO-11-B/C0.6 loaded with 0.5 wt% Pt exhibited excellent performance on a series of alkanes hydroisomerization (n-C6, n-C8, n-C10, n-C12, and n-C16). In addition, the Pt-SAPO-11-B/C0.6 showed the highest i-C16 yield of 90.7% on the n-hexadecane hydroisomerization, outperforming the reported conventional Pt/SAPO-11 catalysts; and it also presents high catalytic activity over 1700 h, which is promising in the real industrial field.