Novel construction and synthesis mechanism of b-axis oriented flower-like SAPO-11 molecular sieve in OSC-containing system for efficient hydroisomerization of long-chain n-alkanes

Abstract

In view of the fact that different kinds of flower-like zeolites and materials have been synthesized for catalysis, but there are few reports on the construction of flower-like SAPO-11 molecular sieve. In this work, we successfully synthesized b-axis oriented flower-like SAPO-11 molecular sieve with multi-layered structure in the organosilicon compounds (OSC)-containing system for the first time. The morphology and b-axis thickness of SAPO-11 flakes were controlled and the tailored synthesis of b-axis oriented flower-like SAPO-11 with multi-layered structure was realized by adding [3-(trimethoxysilyl) propyl] octadecyl dimethyl ammonium chloride (DMC) into the synthesis system. The NiWS supported catalyst for hydroisomerization of n-hexadecane was prepared by using the synthesized flower-like SAPO-11 as support. Through a series of characterization techniques, the effects of morphological changes of SAPO-11 molecular sieve on the textural properties, acidity, element composition and silicon distribution of SAPO-11 molecular sieve were investigated, and the influence mechanism of morphological changes of the support on the active phase properties of the catalyst was studied. The formation mechanism of multi-layered flower-like SAPO-11 was proposed, the influence mechanism of the morphological change of the support on the catalytic performance of the catalyst and the catalytic reaction kinetics was investigated, and the structure–activity relationship between flower-like SAPO-11 and NiWS supported catalyst was systematically expounded. It provides a reference for enriching the morphological types of SAPO-11 molecular sieve and preparing catalyst for high-efficiency hydroisomerization of long-chain n-alkanes.