Preparation and n-hexadecane hydroisomerization properties of SAPO-11 based composite molecular sieve

Abstract In this work, SAPO-11, SAPO-11-γ-Al₂O₃ and SAPO-11-ZSM-5-γ-Al₂O₃ molecular sieve supports were prepared by static hydrothermal synthesis, which SAPO-11-γ-Al₂O₃ and SAPO-11-ZSM-5-γ-Al₂O₃ supports were loaded with Co and Mo as active metal components. The hydroisomerization properties of n-hexadecane on SAPO-11, SAPO-11-γ-Al₂O₃ and SAPO-11-ZSM-5-γ-Al2O₃ molecular sieves were investigated, as well as the effects of reaction temperature, reaction time, solid-liquid ratio and reaction pressure on the hydroisomerization properties. The results showed that the SAPO-11 molecular sieves under the conditions Al₂O₃: H₃PO₄: DPA: SiO₂: H₂O = 1:2:1.2:0.6:55, a crystallization time of 48 h, and crystallization temperature of 180 ℃ were synthesized, had a higher degree of crystallinity and uniform size distribution, and the pore structure was more obvious. After the metal-loaded SAPO-11-γ-Al₂O₃ molecular sieves due to the charged metal blocked part of the pore or pore opening of the molecular sieve, resulting in the reduction of the specific surface area and pore volume, some of their acidic sites are blocked occupied by the metal and the acid is weakened. The results of the hydroisomerization experiments showed that SAPO-11 molecular sieves the isoparaffin selectivity and isoparaffin yield reached maximum values of 31.26% and 28.32% at 340 ℃, 60 min, respectively. The selectivity and yield reached maximum of 51.02% and 43.76% at liquid-solid ratio up to 25:1. The selectivity and yield reached maximum values of 55.82% and 51.2% at an initial reaction pressure of 5 MPA. For the SAPO-11-γ-Al₂O₃ supports, the selectivity and yield the maximum values of 79.50% and 71.49% at a metal Co: Mo loading ratio of 1:3 was achieved. For the SAPO-11-ZSM-5-γ-Al₂O₃ supports, the selectivity and yield the maximum values of 55.44% and 54.05% were achieved with ZSM-5 loading of 30 wt%. These catalysts have the potential for a wide range of applications.