Controlling Acidic Sites to Improve Hydroisomerization Performance of Pt/SAPO-11 Catalysts
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SAPO-11 zeolites with different amount of silicon were synthesized to control the acidic sites of Pt/SAPO-11 catalysts. The structure, acidity and hydroisomerization performance of the SAPO-11 zeolites were systematically investigated. The results showed that with increase of silicon amount, the relative crystallinity of SAPO-11 apparently decreased and dominant crystal faces were different. BET surface area and total pore volume of the samples can change by difference of phase crystal structure. Amount of framework silicon controls acidic property of the SAPO-11. The more incorporation of silicon in the framework resulted in more medium acidic sites on the samples. The different acidic property of the samples was ascribed to different coordination mode of silicon. There are SM2 and SM3 substitution in the frameworks of the SAPO-11 zeolites. On catalysts of Pt/SAPO-11, more platinum existed in the pores. Platinum dispersion and reduction property were almost duplication for all the catalysts. The conversion of model compound and isomerization selectivity strongly depended on the acidic property of the catalysts. The results demonstrated that the optimum catalysts for hydrocarbon isomerization should remain the balance between metal sites and acidic sites.
KeywordsSAPO-11 Acidic sites Silicon amount Hydroisomerization n-Heptane
This work was supported by the “Innovation Fund of China National Petroleum Corporation” (Grant No. 2012D-5006-0402).
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