Synthesis of Ni/SAPO-11-X zeolites with graded secondary pore structure and its catalytic performance for hydrodeoxygenation-isomerization of FAME for green diesel production

Green diesel is regarded as an efficient alternative to fossil fuels because of its clean and renewable properties. SAPO-11 is extensively used as metal support due to its rich weak acidic sites. However, for the one-step production of hydrogenated vegetable oil, the deoxygenation-isomerization process is hindered by the small pore size of SAPO-11. Herein, we reported a method to achieve in-situ regulation of SAPO-11 pore size by adding surfactants and evaluating its catalytic performance for hydrodeoxygenation-isomerization. The addition of surfactant can increase the specific surface area and the number of acid sites of the catalyst. After the regulation of various soft template agents, the secondary pore structure properties of catalyst support have been significantly different. A selective gradient secondary pore structure in the range of 8–18 nm is obtained. The average pore size of the SAPO-11 produced with F127 is the largest, and the hydrodeoxygenation product conversion is as high as 96%, but the stability is poor and the catalyst is easy to be inactivated. The molecular sieve synthesized by using DIPA and DPA as soft templating agents shows excellent catalytic performance. The selectivity of C15–C18 products in the reaction reaches 94%, and the conversion rate only decreases by 11% after four times cycles.